The analysis built on an earlier experiment in which the Candida strains had been exposed daily to hydrogen peroxide for 30 days. Susceptibility to the disinfectant had already been assessed by broth microdilution, after which strains were maintained in broth containing hydrogen peroxide at 0.5×MIC, 1×MIC or 2×MIC. For the work reported here, antifungal susceptibility was evaluated at baseline and after 10, 20 and 30 days of repeated exposure. Testing followed the European Committee on Antimicrobial Susceptibility Testing broth microdilution protocol. Candida strains were cultivated overnight on Sabouraud dextrose agar at 35 °C, and inocula were adjusted to 0.5 McFarland, reported as 1–5 × 10^6 CFU/mL. Each exposed strain was tested in triplicate for each antifungal and incubated for 24 hours at 35 °C before minimum inhibitory concentrations were determined.

For most antifungals, the MIC was defined as the concentration producing 50% growth inhibition; amphotericin B used a greater-than-90% inhibition endpoint. Data were normalized against changes in the corresponding positive control at each time point and then interpreted against EUCAST antifungal susceptibility breakpoints. The researchers regarded a variation as significant only when it exceeded a two-fold dilution relative to the day-zero positive control. This distinction was consequential because the controls themselves displayed some fluctuations, making it difficult to attribute every change in the exposed cultures to hydrogen peroxide. The results therefore separated control-associated variation from subsequent changes confirmed in particular hydrogen-peroxide-exposed strains.

One C. albicans strain, ATCC 10231, showed several shifts after repeated exposure. Following exposure to 0.5×MIC hydrogen peroxide for 20 days, its micafungin MIC was reported as changing from 0.03 to 0.008 mg/L, a numerical decrease that the paper described as an increase in susceptibility in its results section. By day 30, the amphotericin B MIC rose from 0.125 to 0.5 mg/L after 30 days at 1×MIC, while the caspofungin MIC rose from 0.125 to 0.5 mg/L after exposure at 0.5×MIC and 2×MIC. These changes involved both a polyene antifungal and echinocandins, but the investigators classified them as minor fluctuations because the maximum deviation was two two-fold dilutions. The pattern did not establish a consistent mechanism of adaptation across concentrations, agents or sampling times.

Both C. parapsilosis strains showed exposure-associated changes confined to posaconazole susceptibility. C. parapsilosis ATCC 22019 shifted from an MIC of 0.125 to 0.5 mg/L after 30 days at 1×MIC hydrogen peroxide, indicating increased resistance. At 2×MIC, the same strain changed from a susceptible result of 0.003 mg/L to a resistant result of 0.5 mg/L after both 20 and 30 days. The clinical isolate C. parapsilosis CP 009 changed in the opposite direction, moving from a resistant result of 0.125 mg/L to susceptibility at 0.03 mg/L after 30 days at 0.5×MIC. As with the C. albicans findings, the changes did not follow a single disinfectant concentration or antifungal class, and most appeared late in the 30-day period. The authors therefore regarded them as limited susceptibility fluctuations rather than evidence of a coherent resistance mechanism.

The C. auris results require a more qualified interpretation. Major MIC variations were identified for anidulafungin and caspofungin in C. auris DSMZ 21092 at day 30, but the paper also reported comparable variation in positive controls and did not list C. auris among the strains for which subsequent changes were confirmed as associated with hydrogen peroxide exposure. The three C. auris strains had equivalent initial susceptibility values across the antifungals evaluated. Thus, the study did not demonstrate a stable baseline pattern for every measured value, nor did it confirm an exposure-associated susceptibility shift for C. auris. This distinction prevents the preliminary control variation from being presented either as proof that hydrogen peroxide selected for resistance or as evidence of complete absence of variation during the experiment.

Catalase production remained detectable in every exposed strain. Qualitative testing involved mixing five drops of a 3% hydrogen peroxide working solution with a fresh colony; immediate effervescence, representing peroxide decomposition into water and oxygen, was treated as a positive result. The assay was performed in triplicate at each designated time point. Because all strains were catalase-positive from the outset, the experiment established persistence of the detectable phenotype rather than an increase or decrease in enzyme production. The researchers did not directly quantify catalase, measure gene expression or trace the biochemical pathways involved in peroxide detoxification, so the assay cannot establish whether cells altered the amount or activity of the enzyme while retaining a positive tube-test result.

Biofilm formation was assessed with a microtiter-plate assay in which Candida were grown for 48 hours at 35 °C under static conditions. Suspended cells were removed, attached biomass was washed with phosphate-buffered saline, fixed with methanol and stained with 1% crystal violet. The stain was then resolubilized with 33% acetic acid, and biomass was quantified by absorbance at 570 nanometres. Classification used a cutoff calculated from the negative control and its standard deviation, with C. albicans ATCC 90028 included as a positive biofilm-forming control. Six of the seven strains maintained their original biofilm characteristics. The exception was C. parapsilosis CP 009, which shifted from a weak-producer profile at baseline to a non-biofilm-producer classification on day 10 under all three hydrogen peroxide concentrations, then rose above its baseline value on day 20. The investigators interpreted this pattern as a transient, strain-specific fluctuation rather than a general loss of biofilm-forming capacity.

Overall, the experiment did not reveal a consistent adaptive trajectory across the tested Candida strains. Limited MIC shifts occurred in C. albicans and C. parapsilosis, while major variations in the C. auris positive controls prevented those preliminary differences from being confirmed as exposure-associated changes. Catalase remained detectable in every strain, and biofilm formation was stable in all but one C. parapsilosis isolate, whose response fluctuated over time. The results support the limited conclusion that repeated laboratory exposure did not produce broad or uniform changes across the three measured attributes. They do not establish the safety or effectiveness of hydrogen peroxide as a daily hospital disinfectant, nor do they demonstrate changes in fungal virulence, persistence, transmission or human infection. The authors called for periodic environmental monitoring and further studies, including in vivo work, while emphasizing that the clinical relevance of the observed MIC fluctuations remains unresolved.

Subject of Research: Effects of repeated hydrogen peroxide exposure on antifungal susceptibility, catalase production and biofilm formation in Candida strains.

Article Title: Assessment of Candida attributes under in vitro repeated exposure to hydrogen peroxide

Article References: Fernandes, Â. R., Rodrigues, A. G., & Cobrado, L. (2026). Assessment of Candida attributes under in vitro repeated exposure to hydrogen peroxide. International Microbiology. https://doi.org/10.1007/s10123-026-00886-1

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DOI: 10.1007/s10123-026-00886-1

Keywords: Candida, hydrogen peroxide, antifungal susceptibility, biofilm formation, catalase, Candida albicans, Candida parapsilosis, Candida auris, disinfection, in vitro study, Assessment, attributes

The researchers prepared 80% ethanol extracts from seeds collected in Saudi Arabia’s Jazan region, then quantified selected phytochemical classes and individual phenolics. Total phenolics, flavonoids, alkaloids and terpenes were measured with colorimetric assays, while HPLC–DAD was used to analyze phenolic compounds. The biological testing included DPPH and ABTS radical-scavenging assays, FRAP, inhibition of α-amylase, α-glucosidase and butyrylcholinesterase, antimicrobial testing against four bacterial reference strains and one yeast strain, biofilm assays, and cytotoxicity measurements in Caco-2 colorectal adenocarcinoma cells and Wi38 normal lung fibroblasts.

Coffee seed extract contained 172.46 ± 7.17 mg gallic acid equivalents per gram of dry extract for total phenolics, 157.36 ± 3.34 mg quercetin equivalents per gram for total flavonoids, 10.16 ± 0.27 mg/g of alkaloids and 12.41 ± 0.26 mg limonene equivalents per gram for total terpenes. The corresponding loquat values were 40.00 ± 1.58 mg GAE/g, 3.24 ± 1.02 mg QuE/g, 4.25 ± 0.24 mg/g and 2.30 ± 0.04 mg/g. Chlorogenic acid was the dominant measured phenolic in both extracts, at 63,681.37 ± 1,245.6 µg/g in coffee and 5,848.71 ± 98.3 µg/g in loquat.

The coffee extract recorded lower half-maximal inhibitory concentrations in the principal antioxidant and enzyme assays. Its reported IC₅₀ values were 0.42 ± 0.02 µg/mL for ABTS radical scavenging and 0.66 ± 0.03 µg/mL for DPPH, compared with 1.85 ± 0.06 and 2.10 ± 0.08 µg/mL, respectively, for loquat. Coffee also showed lower IC₅₀ values for α-glucosidase inhibition, at 10.20 ± 0.15 µg/mL versus 48.50 ± 1.10 µg/mL, and butyrylcholinesterase inhibition, at 3.20 ± 0.08 µg/mL versus 6.90 ± 0.12 µg/mL. These measurements demonstrate activity in the specific in vitro assays but do not establish the inhibition mechanism or effects in people.

Both extracts inhibited the tested microorganisms, although the quantitative endpoints generally favored coffee. The reported minimum inhibitory concentration of coffee extract against Staphylococcus aureus was 7.8 µg/mL, compared with 31.25 µg/mL for loquat extract. Against C. albicans, the corresponding values were 15.62 and 62.5 µg/mL. The study used reference strains, including Enterococcus faecalis, S. aureus, Escherichia coli, Salmonella typhi and C. albicans, rather than clinical or drug-resistant isolates.

Established-biofilm testing produced the study’s most prominent loquat result. At 75% of the minimum fungicidal concentration, loquat extract reduced measured C. albicans biofilm biomass by 94.12 ± 0.8%. Coffee extract reduced the same measure by 96.68%. These crystal-violet measurements cover both living and dead microorganisms and extracellular material, so they cannot by themselves distinguish inhibition of biofilm formation from cell killing. Parallel viability assessments indicated that the lowest tested concentrations were sublethal, but additional imaging and viability methods would be needed to characterize the effect more precisely.

In the cell assays, coffee extract showed differential cytotoxicity between the two tested cell lines, with a reported Caco-2 IC₅₀ of 78.5 ± 0.2 µg/mL and a Wi38 IC₅₀ of 181.3 ± 2.2 µg/mL, producing a preliminary selectivity index of 2.31. Loquat extract also reduced Caco-2 cell viability, but was more toxic to the normal fibroblast line. The study assessed one cancer cell line and one normal cell line over 48 hours; it did not establish broad anticancer activity, apoptosis, therapeutic selectivity or safety in humans.

Analysis of 12 phenolics quantified in at least one extract found strong inverse associations between chlorogenic acid concentration and several IC₅₀ measurements. Those correlations are compatible with chlorogenic acid contributing to the observed activity, but they do not demonstrate causation. The chemical analysis was limited to 18 phenolic standards, and a major chromatographic peak remained unidentified. Caffeine and loquat triterpenoids were not quantified, leaving their proposed contributions unconfirmed.

The study was also constrained by its use of one seed source and crude extracts, plus the absence of pharmacokinetic, animal or clinical testing. The findings therefore identify measurable in vitro differences between the two seed extracts. Coffee seed extract showed the broader set of stronger assay results, while loquat seed extract was distinguished by its reduction of established C. albicans biofilm biomass. Broader microbiological, chemical and in vivo studies are needed to determine how those laboratory observations translate beyond the tested systems.

Subject of Research: Comparative in vitro phytochemical and biological assessment of coffee and loquat seed extracts

Article Title: Comparative phytochemical characterization and in vitro biological activities of coffee (Coffea arabica) and loquat (Eriobotrya japonica) seed extracts

Article References: Al-Rajhi, A. M. H., Alsalamah, S. A., Almotayri, A. M., Almimoni, N. M., Zeleei, R. I., Al Abboud, M. A., Shater, A.-R. M., Mashraqi, A., Sahagi, E. M., Masmali, I., & Abdelghany, T. M. (2026). Comparative phytochemical characterization and in vitro biological activities of coffee (Coffea arabica) and loquat (Eriobotrya japonica) seed extracts. Scientific Reports, 16(1), Article 32073. https://doi.org/10.1038/s41598-026-72286-4

Image Credits: AI Generated

DOI: 10.1038/s41598-026-72286-4

Keywords: coffee seed extract, loquat seed extract, chlorogenic acid, antioxidant activity, enzyme inhibition, antimicrobial activity, Candida albicans, biofilm reduction, cell cytotoxicity, in vitro study, Comparative, phytochemical

The research team set out to qualitatively and quantitatively assess the antimicrobial efficacy of penicillin, gentamicin, vancomycin, rifampicin, kanamycin, ampicillin, clotrimazole, and amphotericin-B alongside essential oils from lemongrass (Cymbopogon flexuosus), palmarosa (Cymbopogon martinii), and peppermint (Mentha piperita). The pathogens under scrutiny included the Gram-positive bacteria Staphylococcus aureus, Staphylococcus epidermidis, Mycobacterium smegmatis, and Enterococcus faecalis, together with two fungal pathogens, Malassezia furfur and a clinical isolate of Candida albicans. These microorganisms are not exotic threats but everyday residents of the human skin, gut, and mucous membranes that can turn dangerous when the body’s homeostasis is disturbed by surgery, injury, malnutrition, immunodeficiency, or medication.

Opportunistic pathogens occupy a peculiar niche in medical microbiology. In an immunocompetent person, they live harmlessly as commensals, part of the vast microbial community that coexists in mutualistic association with the human body. But when the immune system is subverted or the normal balance of microflora is upset, these facultative parasites can escalate from mild infections to life-threatening bloodstream invasions. S. aureus, for instance, can circumvent immune defenses to cause carbuncles, folliculitis, cellulitis, abscesses, and bacteremia. S. epidermidis, which dwells predominantly on human skin, is a major culprit in hospital-acquired infections and infections of medical implants. E. faecalis, a gastrointestinal commensal, can trigger oral cavity infections, periodontitis, urinary tract infections, and nosocomial disease. Even M. smegmatis, which is not linked to tuberculosis in humans, has the potential to cause soft tissue and pulmonary infections in vulnerable patients.

On the fungal side, the study examined two dimorphic and polymorphic pathogens. C. albicans, an exclusively opportunistic fungus, is well known for causing oral, cutaneous, and vulvovaginal candidiasis, as well as candidaemia and hospital-acquired infections. M. furfur, isolated in this study from a human scalp, is associated with skin conditions such as dandruff, seborrheic dermatitis, and pityriasis versicolor. Combatting these infections traditionally requires reliance on synthetic or semi-synthetic antimicrobials spanning classes such as β-lactams, aminoglycosides, glycopeptides, quinolones, azoles, and polyenes. Yet the indiscriminate use of these drugs has fueled the emerging phenomenon of antibiotic resistance and can carry harmful effects on essential organs, prompting researchers to explore natural alternatives.

Methodologically, the study employed two complementary assays. The disk diffusion test involved spreading 100 microliters of microbial suspension evenly onto fresh nutrient or Sabouraud agar plates, then placing 5-millimeter filter paper disks loaded with 5 micrograms of standard antimicrobials or 30 microliters of essential oil. After incubation at 37 degrees Celsius for 24 hours for bacteria and 28 degrees Celsius for 48 hours for fungi, clear zones of growth inhibition were measured in millimeters, with each test performed in triplicate. The minimum inhibitory concentration, or MIC, was determined by broth dilution in 96-well microtiter plates, with cultures adjusted to 0.5 McFarland standard turbidity to obtain 1 × 10^8 colony-forming units per milliliter. A redox indicator dye, shifting from purple to pink in the presence of cellular reductases, provided a visual readout of microbial viability. The minimum bactericidal and fungicidal concentrations were deduced by spot inoculation onto fresh agar plates from the last three wells of each dilution series.

The disk diffusion results exposed the patchy nature of synthetic drug efficacy. Penicillin produced the maximum zone of inhibition against S. aureus at 40.0 millimeters and suppressed E. faecalis with a 33.0-millimeter zone, while rifampicin and ampicillin also generated strong zones against S. aureus at 32.0 and 32.3 millimeters respectively. Gentamicin proved the most favorable drug against S. epidermidis and M. smegmatis, each at roughly 19 to 20 millimeters. Yet penicillin and ampicillin were completely inactive against M. smegmatis, and S. epidermidis showed no response to penicillin, vancomycin, or ampicillin. Vancomycin, often considered a drug of last resort for Gram-positive infections, exhibited activity against three of the four tested bacteria but proved ineffective against S. epidermidis. Among the antifungals, clotrimazole was highly effective against both M. furfur and C. albicans, producing zones of 34.0 and 32.0 millimeters respectively, while amphotericin-B showed more modest inhibition at 17.5 and 18.0 millimeters.

The essential oils told a different story. Lemongrass oil, applied at 3 percent volume per volume, displayed prominent zones of inhibition against every pathogen examined, including the strains resistant to conventional antibiotics. Its zones ranged from 12.7 millimeters against S. aureus to 30.3 millimeters against M. smegmatis, with particularly strong activity against the fungal pathogens at 27.0 and 28.3 millimeters for M. furfur and C. albicans respectively. Peppermint oil was most effective against M. smegmatis at 31.7 millimeters, while palmarosa oil showed its highest inhibition against M. furfur at 16.7 millimeters. Notably, M. smegmatis, which was resistant to penicillin and ampicillin, was prominently inhibited by both lemongrass and peppermint oils. A similar pattern emerged against S. epidermidis, though peppermint oil showed very low inhibition in that case.

The MIC data reinforced these findings with quantitative precision. Penicillin and rifampicin inhibited S. aureus and E. faecalis at an MIC of 0.10 micrograms per milliliter, while gentamicin suppressed S. epidermidis and M. smegmatis at the same concentration. Kanamycin required a higher MIC of 0.39 micrograms per milliliter to restrict S. epidermidis, and vancomycin was effective at slightly higher concentrations for all pathogens except E. faecalis. Clotrimazole showed antifungal activity at an MIC of 0.10 micrograms per milliliter for both fungal pathogens, whereas amphotericin-B required a higher concentration of 3.12 micrograms per milliliter. For the essential oils, palmarosa yielded the most favorable results against the bacterial pathogens, with MIC values ranging from 0.07 to 0.09 percent volume per volume. Peppermint oil was particularly effective against S. aureus at 0.07 percent, while lemongrass required slightly higher concentrations at 0.19 percent. Against the fungal pathogens, palmarosa and peppermint oils inhibited both at 0.3 percent, while lemongrass achieved inhibition at just 0.12 percent. Crucially, the minimum bactericidal concentrations aligned with the MIC values, indicating that the oils were not merely suppressing growth but killing the pathogens outright.

The mechanistic explanation for essential oil activity lies in their complex bioactive composition. These natural extracts contain a wide variety of terpenes and phenolic compounds whose antimicrobial mode of action relies mainly on cell membrane disruption, interference with enzymatic activity, inhibition of cellular respiration, and disruption of DNA and RNA synthesis. Because these mechanisms target multiple cellular structures simultaneously rather than a single molecular target, pathogens pose minimal risk of developing resistance through the routes that plague conventional antibiotics, such as target alteration or the development of efflux pumps to expel the drug. Combined with their low toxicity, economic viability, and biodegradability, essential oils may be better suited as medications in contrast to synthetic antimicrobials, particularly in an era when multidrug-resistant pathogens have become a serious threat to existing antibacterial treatment.

The authors conclude that although the antimicrobial potency of essential oils cannot surpass standard antibiotics in absolute terms, their efficacy managed to align with synthetic drugs even when differing concentrations were taken into account. All three essential oils inhibited the growth of all tested pathogens to some degree, contrary to several antibiotics that failed to suppress the proliferation of specific microorganisms. Lemongrass oil depicted the most favorable results, giving distinct zones of inhibition between 12.7 and 30.3 millimeters for the majority of tested pathogens while remaining efficient toward resistant strains. The researchers caution that additional research under in vivo conditions is needed to thoroughly assess the full therapeutic potential of these oils and provide valuable insights into potential treatments as substitutes against relevant diseases. Yet the message is clear: nature’s pharmacy, refined over millions of years of plant evolution, may hold answers that synthetic chemistry alone cannot provide.

Subject of Research: Comparative antimicrobial efficacy of synthetic antibiotics and plant essential oils against human pathogenic bacteria and fungi

Article Title: Comparative antimicrobial evaluation of synthetic antibiotics and essential oils against human pathogenic bacteria and fungi

Article References: Khaliq, A., Mishra, A. K., & Rabbani, A. (2024). Comparative antimicrobial evaluation of synthetic antibiotics and essential oils against human pathogenic bacteria and fungi. Innovations in Agriculture, 7, 1-7. https://doi.org/10.3897/ia.2024.124222

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DOI: 10.3897/ia.2024.124222

Keywords: antimicrobial resistance, essential oils, lemongrass, antibiotics, Candida albicans, Staphylococcus aureus, natural remedies, disk diffusion assay, Comparative, antimicrobial, evaluation, synthetic

The therapeutic arsenal against this yeast is eroding. Overuse and misuse of antifungal drugs have fueled the emergence of resistant C. albicans strains, and studies have documented resistance to widely used agents such as fluconazole and itraconazole, contributing to chronic and recurrent infections. Non-albicans Candida species are increasingly recognized as additional treatment challenges. This growing resistance has pushed researchers toward alternative approaches, including postbiotic metabolites, yet studies evaluating the direct effects of postbiotic mediators on fungal biofilms have remained limited.

Probiotics, live microorganisms that can suppress the growth and colonization of C. albicans, have attracted attention for managing oral candidiasis. They produce antifungal compounds such as lactic acid and bacteriocins, and may offer benefits including reduced adverse effects compared with antifungal medications and immunomodulatory effects. But live probiotics carry drawbacks: delayed effects, variable efficacy among individuals, and an increased risk of infection in immunocompromised patients. Postbiotics sidestep these concerns. Defined as non-viable microbial preparations or their components that retain bioactive properties, postbiotic mediators are sterile, cell-free, filter-sterilized preparations containing bioactive metabolites produced by probiotic metabolic activity. Because they avoid administration of viable microorganisms, they may offer practical advantages in storage and formulation, making them particularly interesting for populations in whom live bacteria may be undesirable, although the safety and stability of each preparation require direct product-specific evaluation.

A new study published in MicrobiologyOpen investigated the antifungal effects of postbiotic mediators derived from two of the most extensively studied probiotic strains, Lactobacillus rhamnosus GG (LGG) and Lactobacillus reuteri (LR). Both strains are known for robust growth, adhesion, pathogen antagonism, and production of antimicrobial substances. The researchers assessed the mediators’ minimum inhibitory concentration (MIC) and minimum fungicidal concentration (MFC) against C. albicans ATCC 10231 following Clinical and Laboratory Standards Institute M27-A3 broth microdilution guidelines, then examined their ability to destroy mature biofilms and suppress fungal metabolic activity.

The methods were rigorous. The lactobacilli were cultured in MRS broth for 48 hours, after which cultures were centrifuged and supernatants filtered through 0.22 micrometer membranes to yield sterile cell-free preparations. The pH of each preparation was adjusted to physiological values of 7.2 to 7.4 using sodium hydroxide, a step with important consequences, since organic acids such as lactic and acetic acid exert their primary antifungal effects in their protonated, acidic form. For susceptibility testing, yeast suspensions were standardized spectrophotometrically and diluted in RPMI 1640 medium buffered with MOPS. For biofilm assays, a higher inoculum of 1.5 × 10⁶ CFU/mL was used to ensure confluent and reproducible biofilm formation within the incubation period.

The results were striking. The MIC for both LGG-derived and LR-derived postbiotic mediators was 25 percent (v/v), and no fungal growth appeared on agar at concentrations above this level, confirming the MFC value. Because the MFC equaled the MIC for both preparations, the mediators demonstrated fungicidal activity against planktonic cells. In the biofilm destruction assay, colony-forming unit enumeration showed that both mediators yielded lower viable counts than the untreated control, but the reduction was statistically significant only for the LGG group (p = 0.0038) and not for the LR group (p = 0.1537). The authors note that the absolute reduction for LGG, while significant, was relatively modest, approximately a 17.5 percent decrease relative to control, or about 0.08 log₁₀.

Scanning electron microscopy painted a vivid picture of what the treatments did to biofilm architecture. Biofilms formed on tooth slabs, fixed with glutaraldehyde, dehydrated through ascending ethanol concentrations, and coated with palladium-gold revealed reduced microbial density and fewer microcolonies on treated surfaces, with LGG-derived mediators producing the more pronounced antibiofilm effect. The XTT reduction assay, which measures metabolic activity by detecting absorbance of reduced tetrazolium compound at 490 nm, showed that both mediators significantly suppressed biofilm metabolic activity at half the MIC: mean absorbance fell from 1.78 ± 0.09 in the control to 0.96 ± 0.06 for LGG (p = 0.0009) and 1.12 ± 0.08 for LR (p = 0.0015). This indicates that the mediators exerted biologically relevant effects on biofilm physiology even though they did not achieve rapid, high-level killing of biofilm-embedded cells within the 24-hour exposure window.

The disparity between the two strains, despite comparable MIC and MFC values, may reflect strain-specific differences in metabolite composition and biofilm-targeted mechanisms. While MIC and MFC assays primarily assess fungicidal activity against planktonic cells, LGG mediators may contain metabolites such as biosurfactants, proteases, or bacteriocins that destabilize biofilm architecture by affecting extracellular matrices or hyphal formation, a critical virulence trait of C. albicans. Prior work offers clues: LGG’s major secretory peptidoglycan hydrolase Msp1 has been shown to contribute to chitin degradation in C. albicans hyphae, and lactic acid in LGG-derived preparations affected the glucan coating on hyphal surfaces, potentially making hyphae more accessible to Msp1 activity. LR, meanwhile, produces various organic acids including acetic, lactic, oxaloacetic, propanoic, decanoic, and benzoic acids, which may contribute to growth restriction or fungal cell deformation.

The study has important limitations that temper enthusiasm. Only one reference strain of C. albicans was evaluated, so the results cannot be assumed to represent the susceptibility of genetically diverse clinical isolates, antifungal-resistant strains, or non-albicans Candida species. The postbiotic mediators were tested as crude, chemically uncharacterized preparations, leaving the concentrations and relative contributions of organic acids, peptides, bacteriocin-like compounds, and other metabolites unknown; metabolomic approaches such as LC-MS/MS should be used to identify the active components. Mechanisms of action were not directly investigated, cytotoxicity and biocompatibility were not assessed in mammalian cell models, and all experiments were performed in vitro without reproducing salivary flow, host immune responses, or polymicrobial oral biofilms. The pH adjustment may also have reduced the activity of pH-sensitive organic acids, and no standard antifungal comparator such as fluconazole was included for direct benchmarking.

These caveats aside, the findings demonstrate that cell-free postbiotic mediators from LGG and LR suppress the metabolic activity of C. albicans biofilms, with LGG-derived preparations showing the greater antibiofilm effect and electron microscopy confirming altered biofilm architecture. As antifungal resistance continues to spread and dental caries remains a burden on public health, especially among children, postbiotics offer a compelling direction: the antimicrobial benefits of probiotic bacteria without the risks of administering live microorganisms. Before therapeutic or preventive applications are considered, future research must evaluate diverse clinical and resistant Candida isolates, chemically characterize the active metabolites, investigate hyphal transition and membrane integrity, assess cytotoxicity in oral epithelial and fibroblast models, and test efficacy in physiologically relevant in vivo conditions. The road from laboratory dish to dental clinic is long, but this study marks a meaningful step along it.

Subject of Research: Antifungal and antibiofilm activity of postbiotic mediators from Lactobacillus rhamnosus GG and Lactobacillus reuteri against Candida albicans

Article Title: Antifungal Activity Assessment of Postbiotic Mediators Derived From Lactobacillus rhamnosus GG and Lactobacillus reuteri Against Candida albicans

Article References: Amirinia, F., Banakar, M., Alaeddini, M., Etemad‐Moghadam, S., Pourhajibagher, M., & Noori, M. (2026). Antifungal Activity Assessment of Postbiotic Mediators Derived From Lactobacillus rhamnosus GG and Lactobacillus reuteri Against Candida albicans. MicrobiologyOpen, 15(5), Article e70439. https://doi.org/10.1002/mbo3.70439

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DOI: 10.1002/mbo3.70439

Keywords: postbiotics, Lactobacillus rhamnosus GG, Lactobacillus reuteri, Candida albicans, biofilm, antifungal resistance, oral health, Antifungal, Activity, Assessment, Postbiotic, Mediators

The study, published in the Spanish Journal of Soil Science by Darina Zheleva and Desislava Angelova of the University of Chemical Technology and Metallurgy together with Ekaterina Krumova, Lyudmila Yovchevska and Yana Gocheva of the Stephan Angeloff Institute of Microbiology at the Bulgarian Academy of Sciences, addresses a gap in leather nanotechnology. Most work on antimicrobial leather has focused on the pre-tanning stage, where nanomaterials are added to the tanning solution itself. Far fewer investigations have explored the very last step of leather processing—the finishing stage—where a thin protective film is laid on top of the material. It is precisely here that the Bulgarian team chose to intervene, synthesizing and depositing zinc oxide nanoparticles in situ rather than simply mixing a pre-made powder into a coating.

The choice of zinc oxide is deliberate. Among metal oxide nanomaterials such as titanium dioxide, copper oxide, silver and copper, ZnO stands out for its strong antimicrobial properties, its biocompatibility, its relatively low toxicity and its cost-effectiveness. Positively charged zinc-containing particles can interact electrostatically with the negatively charged surfaces of bacterial cell walls, and the nanoparticles are known to generate reactive oxygen species—hydrogen peroxide, superoxide anions and hydroxyl radicals—that inflict oxidative stress on microbial cells. Released zinc ions additionally interfere with bacterial metabolism and enzyme function, and the particles’ small size allows them to penetrate membranes and damage intracellular components, including DNA.

To anchor the nanoparticles to the leather, the researchers used a cleverly matched scaffold: a cross-linked gelatin hydrogel, chemically similar in structure to the collagen that constitutes natural leather itself. Gelatin and collagen carry abundant amino, amide and carboxyl groups in their side chains, and these polar groups can bind metal atoms. The amino and carboxyl functional groups act as binding sites for zinc ions, seeding localized nucleation of ZnO crystals on and within the coating. In effect, the organic matrix becomes a template that guides the growth of the inorganic particles.

The team prepared chrome-tanned pig leather samples, each 50 by 50 millimeters and 0.89 millimeters thick, and treated them with three different methods that varied the sequence of steps. In the first method, gelatin was cross-linked with glutaraldehyde before leather impregnation, followed by the addition of zinc nitrate solution and sodium hydroxide. The second method immersed the leather in gelatin first and introduced the crosslinking agent later. The third method, performed in an ultrasonic bath, pre-mixed the zinc nitrate and sodium hydroxide solutions before impregnation and crosslinking. In all cases, sodium hydroxide was added in tenfold excess relative to zinc ions, driving the precipitation of zinc hydroxide and its conversion to zinc oxide during thermal treatment and drying.

Scanning electron microscopy revealed what happened next: the spherical nanoparticles morphed into striking flower-like structures, a sign that nucleation of ZnO crystal architecture had begun on the leather surface. Individual particles measured between 50 and 200 nanometers, but clusters and agglomerations swelled to more than 500 nanometers and beyond one micrometer. The team attributes the flower-like morphology to heterogeneous nucleation on the gelatin matrix: supersaturation after the addition of sodium hydroxide drives crystal growth along specific crystallographic planes of the wurtzite structure, while the surrounding organic network restricts orientation and promotes radial, petal-like assembly. Elemental analysis added a dramatic quantitative contrast. In the first sample type, the coating contained roughly 11.6 percent zinc oxide by weight within the probed cubic-micrometer region; in the second, where the particles sat atop the hydrogel surface, the figure jumped to approximately 64.6 percent—suggesting heavy agglomeration and, critically, higher surface activity exactly where it matters for microbial contact.

Spectroscopy confirmed the chemistry underneath. Fourier-transform infrared spectra showed the expected absorption peaks for amide and amine groups from collagen and gelatin, and demonstrated that positively charged zinc species can bind electrostatically to negatively charged carboxylate residues or to the lone electron pairs on amino acid nitrogen atoms. A characteristic peak at 852 wavenumbers confirmed the formation of tetrahedrally coordinated zinc oxide, most clearly expressed in the ultrasonically treated sample. Ultraviolet-visible spectroscopy sealed the case with a low absorption peak at 363 nanometers—the unambiguous optical fingerprint of nanostructured zinc oxide.

Then came the biological tests, conducted with the Kirby–Bauer disc diffusion method against four bacterial strains: Pseudomonas aeruginosa and Escherichia coli, both Gram-negative, and Bacillus subtilis and Erysipelothrix rhusiopathiae, both Gram-positive. The results revealed a clear selectivity. Only the ultrasonically prepared sample produced a measurable zone of inhibition, and only against Bacillus subtilis, with a modest inhibition zone of about 4 millimeters—small compared with the 18-millimeter zones produced by a reference antibiotic. The Gram-negative bacteria proved entirely resistant to all the modified samples. This pattern matches earlier findings that Gram-positive bacteria are generally more vulnerable to ZnO nanoparticles than their Gram-negative counterparts, possibly owing to differences in cell wall architecture, surface charge, membrane composition and cellular physiology. The researchers also note that the relatively weak antibacterial effect may stem from limited diffusion of active zinc species out of the cross-linked gelatin matrix, which restricts the particles’ availability at the bacterial interface—a trade-off inherent in immobilizing nanoparticles for durability.

Against fungi, the story was considerably more impressive. The untreated leather showed no antifungal activity whatsoever, but all three ZnO-modified variants strongly protected against Aspergillus niger and Candida albicans. Growth of Candida albicans was inhibited for the first 24 hours before the yeast resumed growth, while Aspergillus niger growth was suppressed for 24 hours, followed by long-lasting inhibition of sporulation that persisted through 72 hours of observation. The mechanism likely combines physical effects—disruption of ion transport, membrane integrity and protein function by the particles—with chemical attack through reactive oxygen species generation, zinc ion release and direct membrane interaction. When treated with the nanoparticles, fungal hyphae developed compact vacuole-like structures, lost cytoplasmic volume and became coated with electron-dense particle layers, consistent with nanoparticle adsorption and subsequent cellular damage.

The authors conclude that these ZnO-containing finish films can serve as effective protective antibacterial and antifungal coatings for shoe leather, helping shield the human foot from microbial exposure. Because zinc oxide holds Generally Recognized As Safe status for certain uses and has shown limited dermal penetration and low acute toxicity in most studies, the approach looks promising relative to the hazardous biocides traditionally used to prevent leather biodegradation. Still, the researchers urge caution: the long-term effects of chronic skin contact with zinc ion release remain insufficiently understood, and nanomaterials fall under the EU’s REACH regulatory framework, demanding careful toxicological evaluation. There is also an unsolved sustainability problem at the end of the product’s life. No current technology can extract or regenerate nanoparticles embedded in footwear materials, which limits both the reuse of the embedded metal and the technology’s overall environmental credentials. For now, the work stands as a vivid demonstration that the final finishing step—the one the industry has long overlooked—may be the best place to build infection-fighting power directly into the shoes on our feet.

Subject of Research: Antimicrobial zinc oxide nanoparticle coatings for shoe lining leather

Article Title: Investigation of ZnO Antimicrobial Surface Treatment of Shoe Lining Materials

Article References: Zheleva, D., Angelova, D. S., Krumova, E., Yovchevska, L., & Gocheva, Y. (2026). Investigation of ZnO Antimicrobial Surface Treatment of Shoe Lining Materials. Spanish Journal of Soil Science, 15, Article 14992. https://doi.org/10.3389/sjss.2025.14992

Image Credits: AI Generated

DOI: 10.3389/sjss.2025.14992

Keywords: zinc oxide nanoparticles, antimicrobial coating, shoe lining leather, gelatin hydrogel, footwear hygiene, reactive oxygen species, Aspergillus niger, Candida albicans, nanotechnology, leather finishing, collagen, antifungal activity

At the heart of Zhang’s research lies a deceptively simple idea: rather than trying to engineer, molecule by molecule, a synthetic particle capable of navigating the treacherous terrain of the human bloodstream, why not simply borrow the camouflage that nature has already perfected? His laboratory takes membranes harvested from human cells and wraps them around biodegradable nanoparticles roughly one-thousandth the width of a human hair. Once cloaked, these particles inherit some of the biological powers of the cells they mimic. Red blood cell membranes allow the particles to circulate undetected for extended periods, delivering drugs to the tissues that need them. White blood cell membranes endow the particles with an entirely different talent: the ability to soak up and neutralize the toxic molecules that drive sepsis, to attack infection-causing fungi, and even to intercept the inflammatory signals that fuel rheumatoid arthritis.

The insight emerged from a longstanding frustration in nanomedicine. Nanoparticles can carry enormous payloads of medicine relative to their size, but once injected into the bloodstream they run headlong into the immune system, a surveillance network exquisitely designed to eliminate anything that does not belong. Researchers had long tried to make synthetic particles less conspicuous, coating them with polymers and other materials intended to suppress immune recognition, with limited success. Zhang’s alternative was more radical and, in retrospect, more elegant. Instead of making synthetic particles harder to recognize, he would make them genuinely recognizable as self. His team began with red blood cells, collecting their membranes and wrapping them around nanoparticles while carefully preserving the proteins, lipids, and carbohydrates that naturally stud the cell surface.

The landmark demonstration came in 2011, when Zhang’s group published a paper in the Proceedings of the National Academy of Sciences showing that membrane-coated nanoparticles could circulate in the bloodstream for up to two days, far longer than many conventional nanoparticles of the era. Zhang has often described the strategy as an engineering shortcut. Recreating the staggering molecular complexity of a cell surface from scratch, with its precisely organized arrays of proteins, lipids, and carbohydrates, would be a monumental synthetic challenge. Using the membrane itself sidesteps that problem entirely. The beauty of the technology, as Zhang puts it, is that the complexity does not have to be rebuilt; it can simply be transferred intact onto the surface of a particle small enough to travel wherever the blood goes.

The disguise offered far more than extended circulation time. Red blood cells are natural targets for bacterial toxins that kill cells by punching holes in their membranes, and particles dressed as red blood cells proved irresistible to those toxins. Zhang’s team christened these decoys nanosponges for their ability to soak up toxins and divert them away from real cells. The approach showed promise against toxins produced by dangerous bacteria, including methicillin-resistant Staphylococcus aureus, better known as MRSA. By removing toxins from circulation, the nanosponges helped weaken MRSA infections, and because the strategy does not depend on antibiotics at all, it points toward a way of treating drug-resistant infections without fueling the resistance crisis that has rendered so many conventional drugs ineffective.

From that first success, Zhang began borrowing membranes from an expanding cast of cell types. His laboratory developed macrophage-coated nanosponges to capture the toxins and inflammatory molecules involved in sepsis, the uncontrolled immune response triggered by bacterial infection that can cascade into organ damage and death. Because macrophage membranes carry receptors for a broad spectrum of sepsis-causing molecules, the particles function as universal traps rather than single-target drugs, an approach Zhang argues is more effective than attacking one disease-causing molecule at a time. Neutrophil-coated nanosponges followed, designed to treat rheumatoid arthritis. Neutrophils are immune cells that rush to sites of inflammation, where they can perpetuate a chain reaction of tissue damage; the neutrophil nanosponges acted as decoys, intercepting inflammation-causing molecules before they could keep the destructive cycle turning.

More recently, the concept has been extended to drug-resistant fungal infections caused by Candida albicans, the organism behind common yeast infections and, in severe cases, deadly bloodstream infections. Since macrophages naturally recognize Candida, Zhang’s researchers used macrophage membranes to build nanoparticles that could seek out fungal cells. In experiments, the particles attached to Candida cells, physically damaged them, and helped stimulate the body’s own immune defenses. The same membrane-borrowing principle has also produced platelet-coated nanoparticles for targeted drug delivery. Platelets, the tiny cell fragments that bind to damaged blood vessels to stop bleeding, also preferentially bind to certain pathogens, including MRSA. When loaded with medicine, the platelet-disguised particles delivered their cargo directly to damaged arteries and bacterial infections, healing them with only a fraction of the typical dose while minimizing side effects elsewhere in the body.

For Zhang, the urgency of translating laboratory discoveries into real medicine has a deeply personal origin. When he joined UC San Diego in 2008, his laboratory was housed in the Moores Cancer Center, where he watched dozens of cancer patients pass through the building every day. That environment, he has said, provided a natural intersection between engineering and medicine, and seeing so many people suffering left him feeling a scientist’s responsibility to do something that could make a difference. His path to that mission was unconventional. As an undergraduate studying chemical engineering at Tsinghua University in Beijing, he helped develop an unusually tough plastic and could have commercialized it and opened a factory. Instead he left for a Ph.D. in chemical engineering at the University of Illinois at Urbana-Champaign and a postdoctoral fellowship at MIT. Though the plastics factory never materialized, his entrepreneurial instincts did: he co-founded biotech startups, including San Diego-based Cellics Therapeutics, which is working to move the red blood cell and macrophage nanosponges toward clinical studies for bacterial infections, autoimmune diseases, and inflammatory diseases, while also exploring cellular nanoparticles that could neutralize a wide variety of pathogens, including bacterial toxins and viruses.

That commitment to scalability now shapes his leadership as chair of his department, where he has worked to bridge the traditionally separate territories of chemical engineering and nano engineering. Nano engineering, as Zhang explains it, centers on innovative nanoscience and technologies operating at very small scales, while chemical engineering focuses on large-scale production, manufacturing, and the processes that turn materials into products. His effort to fuse the two was recognized with a $21 million gift to the department in 2024 from San Diego business leader and philanthropist Aiiso Yufeng Li and his family, and the merged department now operates under the slogan Scalable Innovation, allowing undergraduates to move seamlessly between nanoscale science and the realities of manufacturing at scale. Zhang’s career has accumulated a long list of distinctions along the way: election as a fellow of the National Academy of Inventors in 2020, the American Association for the Advancement of Science in 2018, and the American Institute for Medical and Biological Engineering in 2015, plus recognition on Popular Science’s Brilliant 10 list in 2016, MIT Technology Review’s top 35 young innovators in 2013, and repeated appearances among Clarivate’s Most Highly Cited Researchers.

The reach of Zhang’s idea now extends well beyond his own laboratory. In the past decade, more than 10,000 papers on cell membrane coating technology have been published by hundreds of laboratories worldwide, a testament to how thoroughly the approach has permeated the field. Zhang notes that laboratories around the globe are using the technology to advance their own research, an impact that reaches researchers he may never meet. At UC San Diego, he joins a select company of MacArthur Fellows on the current faculty, including computer science and engineering professor Stefan Savage, Division of Social Sciences Dean Carol Padden, anthropology professor Guillermo Algaze, and philosophy professor Nancy Cartwright, along with several emeritus recipients. Chancellor Pradeep K. Khosla congratulated Zhang on what he called a tremendous, well-deserved honor, crediting the professor with turning cellular membranes into a platform technology to deliver medicines and combat infectious disease and inflammation. As the fellowship’s unrestricted funds free him to pursue whatever directions he chooses, the cellular disguises that began as an engineering shortcut now stand as one of the most influential ideas in modern nanomedicine, with the potential to redefine treatment for cancer, infection, and inflammatory disease alike.

Subject of Research: Cell-mimicking nanoparticles for drug delivery and treatment of infectious and inflammatory diseases

Article Title: Nanomedicine pioneer at UC San Diego awarded MacArthur ‘Genius Grant’

Article References: Nanomedicine pioneer at UC San Diego awarded MacArthur ‘Genius Grant’. (n.d.). Original publication

Image Credits: AI Generated

DOI: Not provided

Keywords: MacArthur Fellowship, nanomedicine, cell membrane-coated nanoparticles, drug delivery, nanosponges, antibiotic resistance, sepsis, rheumatoid arthritis, MRSA, Candida albicans, UC San Diego, biotechnology

A central puzzle in resistance biology is whether different fungal isolates traveling toward the same resistant phenotype take the same genetic road or different ones. If resistance usually arises through a shared, predictable set of mutations, then diagnostic assays targeting those mutations could catch resistant strains early, and drug development could focus on countering a small number of mechanisms. If, however, resistance can be assembled through many alternative mutational routes, surveillance becomes far harder, because each new resistant isolate may carry a unique genomic signature. A new study published in PLOS One by Mounzer Abbas, Nour Fattouh, Christy Chedraoui, Setrida El Hachem, Tsolaire Sourenian, Ibrahim Bitar, and Roy A. Khalaf set out to answer exactly this question for C. albicans, asking whether antifungal resistance follows convergent or divergent adaptive pathways at the genetic level.

The team’s experimental design was deliberately controlled. They generated six laboratory-induced fluconazole-resistant isolates and six caspofungin-resistant isolates and then subjected all twelve to whole-genome sequencing, paired with a battery of phenotypic tests measuring traits tied to pathogenicity, including ergosterol content, efflux pump activity, chitin levels, and biofilm formation. By evolving resistance in the laboratory under defined conditions, the researchers could compare resistant isolates against their susceptible progenitors and attribute specific genomic changes to the resistance process itself, rather than to the heterogeneous backgrounds of clinical strains collected from different patients.

The fluconazole-resistant isolates told a story of remarkable phenotypic convergence. Every one of the six showed increased ergosterol production, a classic response to azole pressure, because the fungus compensates for the partial inhibition of its ergosterol biosynthesis pathway by pushing the pathway harder. Every one also displayed elevated activity of ATP-binding cassette transporter efflux pumps, the molecular pumps that actively expel fluconazole from the cell before it can reach its target. In other words, at the level of physiology, all six isolates had arrived at essentially the same resistant state, combining target-pathway compensation with active drug export.

When the researchers looked at the underlying DNA sequences, however, the picture became more complicated. Certain mutations recurred across all the fluconazole-resistant isolates, including variants in ERG24, a gene encoding an enzyme in the ergosterol biosynthesis pathway, and a specific substitution, SOD6 S225P, in a superoxide dismutase gene that appears in every resistant isolate. These recurrent changes suggest genuine convergent evolution, with the same amino acid substitutions arising independently in separate lineages because they confer a selective advantage under azole stress. Yet other mutations, such as ERG11 T128K in the direct target of fluconazole, appeared in some isolates but not others, indicating that the resistance program is assembled from a mixture of shared core mutations and isolate-specific accessory changes.

The caspofungin-resistant isolates presented an equally instructive contrast. All six shared a common resistance strategy centered on the cell wall, but the genetic implementation differed from isolate to isolate. Each carried mutations in CHS3, the gene encoding chitin synthase 3, the enzyme responsible for the bulk of chitin synthesis in C. albicans. Because caspofungin blocks beta-glucan synthesis, fungi can compensate by reinforcing their walls with extra chitin, and elevated chitin is a well-established mechanism of echinocandin tolerance. Strikingly, although every resistant isolate increased its chitin content, the magnitude of that increase varied among isolates, tracking the diversity of CHS3 mutations each had acquired. A shared adaptive strategy, chitin reinforcement, was thus implemented through distinct genetic variants with quantitatively different outcomes.

Beyond point mutations, the sequencing analysis, performed with the Yeast Mapping Analysis Pipeline, or YMAP, revealed large-scale chromosomal rearrangements in the resistant isolates. These structural changes, which can include aneuploidy and segmental duplications, add an important dimension to the resistance story because they can amplify the dosage of resistance-conferring genes or alter the copy number of entire chromosomes carrying drug targets. The finding underscores that resistance evolution in C. albicans is not simply a matter of accumulating single-nucleotide changes; genome architecture itself is a mutable substrate, and rearrangements can contribute materially to the acquisition of the resistant phenotype.

Perhaps the most biologically intriguing result concerns what resistance costs. Many of the resistant isolates, for both drugs, showed decreased biofilm formation and reduced virulence-associated characteristics compared with their susceptible counterparts. Biofilms, the surface-attached microbial communities that are particularly problematic on catheters and other medical devices, are energetically expensive structures, and the same cellular remodeling that confers drug resistance appears to impose fitness trade-offs on other traits. This pattern suggests that resistance and virulence are not independently adjustable dials; rather, the evolutionary pressure to survive drug exposure can force the fungus to sacrifice aspects of its pathogenic arsenal, a phenomenon with potential implications for how resistant infections behave in patients.

Taken together, the study delivers a nuanced verdict on the convergence question: convergent phenotypes, divergent genetics. The resistant isolates converged on shared physiological strategies, ergosterol elevation and efflux for fluconazole, chitin reinforcement for caspofungin, and even on some recurrent point mutations, but the full set of genomic changes underlying each resistant phenotype was largely isolate-specific, and chromosomal rearrangements added further heterogeneity. For clinicians and epidemiologists, this means that sequencing a single canonical mutation will not reliably identify all resistant strains, and that resistance surveillance must contend with a shifting mosaic of genetic mechanisms. For drug developers, the fitness trade-offs observed here hint that combination strategies targeting both resistance mechanisms and virulence pathways could exploit the costs that resistance imposes.

The work also highlights the value of laboratory evolution experiments as a complement to clinical genomics. By observing resistance as it emerges under controlled conditions, researchers can distinguish cause from correlation, identify recurrent mutations that represent genuine adaptive solutions, and measure the phenotypic consequences of specific genetic changes. As antifungal resistance continues to spread globally and the pipeline of new antifungal agents remains thin, studies of this kind provide an essential map of the evolutionary landscape that future drugs and diagnostics will need to navigate, one in which the same destination can be reached by many different roads.

Subject of Research: Genetic mechanisms of fluconazole and caspofungin resistance evolution in Candida albicans

Article Title: Diverse genetic pathways drive convergent fluconazole and caspofungin resistance phenotypes in Candida albicans

Article References: Abbas, M., Fattouh, N., Chedraoui, C., El Hachem, S., Sourenian, T., Bitar, I., & Khalaf, R. A. (2026). Diverse genetic pathways drive convergent fluconazole and caspofungin resistance phenotypes in Candida albicans. PLOS One, 21(10), e0360234. https://doi.org/10.1371/journal.pone.0360234

Image Credits: AI Generated

DOI: 10.1371/journal.pone.0360234

Keywords: Candida albicans, antifungal resistance, fluconazole, caspofungin, whole-genome sequencing, ergosterol, efflux pumps, chitin, biofilm, chromosomal rearrangements, evolutionary convergence, virulence trade-offs

The new study, published in PLOS Biology, addresses a long-standing puzzle in the biophysics of fluoride transport. FEX channels belong to a broader family of anion-selective channels known as Fluc proteins, which are remarkable for their extreme selectivity: they permit fluoride ions to flow through at high rates while excluding nearly all other anions, including the chemically similar chloride. Earlier work had established that FEX activity depends on sodium, meaning the channels do not simply export fluoride on their own but require the presence of sodium ions to function. What remained unclear was how sodium achieves this activation, where the ions bind, and whether other monovalent cations, the positively charged ions such as lithium, potassium, and rubidium that abound in biological environments, might influence the process. Because the cellular milieu is a crowded soup of competing ions, the answer could matter for real organisms, not just purified proteins in a test tube.

To dissect the mechanism, the researchers turned to a reconstituted system, a minimalist experimental platform in which purified FEX proteins are embedded into artificial lipid membranes. This approach strips away the confounding complexity of a living cell and allows the researchers to control precisely which ions are present on either side of the membrane. By measuring fluoride flux under different ionic conditions, they could isolate the contribution of each cation to channel activity. The results revealed that sodium and lithium, despite their chemical similarity as small alkali metal ions, have sharply divergent effects. Sodium supports robust channel activity, acting as the activating cofactor that the fluoride exporter needs to transport its anionic cargo. Lithium, by contrast, does not activate the channel at all. Worse, it actively interferes with sodium-dependent activation.

The functional assays showed that lithium behaves as a competitive antagonist of channel activation. In other words, lithium ions compete with sodium ions for the same binding site, located at the center of the channel, and when lithium occupies that site, the channel is locked into an inactive state. Competitive antagonism is a familiar concept in pharmacology, where drug molecules block receptor sites to prevent natural ligands from binding, but seeing it play out with two biologically common metal ions competing to regulate an ion channel is unusual. The implication is that the ratio of sodium to lithium in the cellular environment could directly tune how well a fungus or other eukaryote exports fluoride, and therefore how resistant it is to fluoride poisoning.

The team then connected this molecular mechanism to a whole-organism phenotype. In yeast, a standard eukaryotic model organism, the presence of lithium markedly reduced fluoride tolerance. Yeast cells that would normally survive a given dose of fluoride faltered when lithium was also present, because their FEX channels could no longer export the fluoride efficiently. This finding elevates the work from an in vitro biophysical curiosity to a potentially significant environmental and physiological observation. Lithium has not previously been recognized as an environmental antagonist of eukaryotic fluoride export, and the results tie cellular fluoride stress tolerance directly to the abundance of additional ions in the surrounding milieu. Any environment where lithium concentrations rise, whether through natural geochemistry or industrial contamination, could thereby sensitize eukaryotic communities to fluoride that they would otherwise shrug off.

To understand why lithium and sodium have such different effects on the same binding site, the researchers determined a cryo-electron microscopy structure of the FEX channel from the pathogenic fungus Candida albicans in the presence of lithium ions. Cryo-EM, a technique that flash-freezes individual protein molecules in glassy ice and images them with an electron beam, has revolutionized the study of membrane proteins, and it allowed the team to visualize the channel at near-atomic resolution with the antagonist bound. The structure revealed the architecture of the central cation binding site and showed how lithium coordinates there. But a static structure alone could not explain the functional differences, because ion binding sites often look deceptively similar for chemically related ions. The crucial differences, it turned out, lay in the dynamics.

Complementing the cryo-EM structure, the team ran molecular dynamics simulations, computational models that track the motion of every atom in the protein and its surrounding membrane over time. These simulations exposed a fundamental difference in the preferred coordination sphere of the two cations, meaning the geometric arrangement of atoms that each ion prefers to surround itself with. Sodium binding supports a dynamic structure with a broader pore radius, keeping the channel in an open, flexible conformation through which fluoride ions can pass. Lithium coordination, by contrast, favors a more rigid and compact conformation, particularly in the channel’s vestibule, the funnel-shaped entry region that guides ions toward the pore. Lithium’s smaller radius and stronger electrostatic grip on its coordinating atoms essentially stiffen the protein around the binding site.

Those conformational changes propagate through the channel in ways that directly obstruct fluoride transport. The simulations showed that lithium binding perturbs the tilt angle of a pore-lining helix, one of the protein’s structural elements that forms part of the wall of the ion-conducting pathway. At the same time, it alters the rotamer, or side-chain orientation, of a key phenylalanine residue that juts into the pore. Phenylalanine’s bulky aromatic side chain acts as a gatekeeper within the permeation pathway, and when its orientation shifts, the effective opening of the channel narrows. Together, the helix tilt change and the phenylalanine rearrangement constrict the permeation pathway, explaining at the atomic level why lithium-bound channels cannot conduct fluoride even though the ion sits in the very site that normally activates transport.

The study thus delivers a complete mechanistic arc, from organism-level physiology down to individual atoms, and back again. It explains how a eukaryotic fluoride channel is regulated by monovalent cations, identifies the structural determinants of that regulation, and demonstrates that the regulation has real consequences for fluoride resistance in living cells. For biophysicists, the work adds to a growing appreciation that ion channels are not merely passive conduits but are exquisitely sensitive to the ionic composition of their environment, with different cations stabilizing distinct conformational ensembles of the same protein. For microbiologists and ecologists, it suggests that fluoride resistance in nature is not determined by fluoride alone but by the full ionic context in which organisms live, a factor that has been invisible until now.

There are also practical implications worth considering. Candida albicans, the organism whose channel was visualized structurally, is a major human fungal pathogen, and fluoride tolerance mechanisms have been proposed as contributors to fungal fitness in host environments and clinical settings. If lithium or related cations can compromise fluoride export in fungi, the interplay between environmental ion concentrations and microbial survival becomes a variable worth measuring in agricultural, industrial, and medical contexts where fluoride exposure is significant. Conversely, the finding that a simple, environmentally available ion can disable a resistance mechanism hints at new strategies for sensitizing fluoride-resistant organisms. As with any reconstituted and cell-based study, extending these results to more organisms and more complex environments will be the next step, but the core message is already clear: the battle over fluoride toxicity is fought not just with fluoride, but with the sodium and lithium ions that decide whether the cellular escape route stays open.

Subject of Research: Regulation of eukaryotic fluoride exporter channels by monovalent cations and its effect on fluoride resistance

Article Title: Monovalent cations differentially regulate the activity of eukaryotic fluoride channels and impact fluoride resistance

Article References: Kang, C.-Y., Heidari, S., Kolb, S., An, M., Ohi, M. D., Torabifard, H., & Stockbridge, R. B. (2026). Monovalent cations differentially regulate the activity of eukaryotic fluoride channels and impact fluoride resistance. PLOS Biology, 24(9), e3004008. https://doi.org/10.1371/journal.pbio.3004008

Image Credits: AI Generated

DOI: 10.1371/journal.pbio.3004008

Keywords: fluoride exporter, FEX channels, lithium, sodium dependence, cryo-EM, molecular dynamics, yeast, Candida albicans, fluoride resistance, ion channels, competitive antagonism, PLOS Biology

A team of pharmaceutical scientists in India has now developed a thin, flexible film loaded with amixicile, a next-generation antimicrobial, designed to be placed directly into the diseased gum pocket. The work, published in Discover Chemistry, describes how the researchers combined amixicile with two film-forming polymers, the natural polysaccharide pullulan and the synthetic, water-soluble polymer polyvinyl alcohol, to create a locally applied treatment for periodontitis. Amixicile is a derivative of the antiparasitic drug nitazoxanide and works through an unusual mechanism: it inhibits pyruvate-ferredoxin oxidoreductase, or PFOR, a key enzyme in the energy metabolism of anaerobic bacteria. By binding to thiamine pyrophosphate, a cofactor the enzyme depends on, amixicile prevents pyruvate from binding, blocking the formation of acetyl-CoA and carbon dioxide and thereby starving anaerobic pathogens of energy. Crucially, every oral Treponema species studied so far relies on PFOR, making amixicile a particularly promising candidate against periodontal pathogens, while its high selectivity for anaerobic organisms keeps it relatively non-toxic to host tissues.

The choice of polymers was equally deliberate. Pullulan, a fermentation product of the fungus Aureobasidium pullulans, is non-ionic, bio-erodible and biocompatible, with outstanding film-forming ability; it is already used in commercial oral care films sold internationally under the Listerine brand. Its many hydroxyl groups make it highly water-soluble, so it absorbs water, swells and breaks down, helping entrapped drug molecules diffuse out. Polyvinyl alcohol complements this by adding mechanical strength through intermolecular hydrogen bonding, improving the film’s elasticity, wettability and swelling behavior. Together, the two polymers form a matrix that is strong enough to be handled and inserted into a gum pocket yet dissolves quickly enough to release its payload. The films themselves were made by solvent casting: the polymers were dissolved in water, amixicile was stirred into the homogeneous blend, and the solution was cast into petri plates and dried in a hot air oven at 80 degrees Celsius before being trimmed into two-by-two-centimeter squares.

Before formulating, the team established how much drug is actually needed to stop microbial growth. Using a broth dilution method, they determined that the minimum inhibitory concentration of amixicile against both Pseudomonas aeruginosa and Candida albicans was 20 micrograms per milliliter. The minimum bactericidal concentration against Pseudomonas aeruginosa and the minimum fungicidal concentration against Candida albicans were both 25 micrograms per milliliter. The choice of test organisms reflects the complex ecology of periodontal pockets: Candida albicans is the most prevalent fungus in both healthy and diseased oral cavities and has been shown to facilitate invasion of gingival epithelial cells by Porphyromonas gingivalis, while Pseudomonas aeruginosa, though not a primary periodontal pathogen, can thrive in the low-oxygen niches of periodontal pockets, forming biofilms and secreting virulence factors such as phenazines and pyocyanin that sustain inflammation and tissue destruction.

To optimize the formulation rather than rely on trial and error, the researchers employed a central composite design, a statistical approach that systematically varies the concentrations of pullulan and polyvinyl alcohol and models their effects on two critical quality attributes: in-vitro drug release and tensile strength. Nine formulations were produced and evaluated. Drug content across the batches ranged from 87.7 to 97.4 percent, indicating that amixicile was evenly dispersed throughout the films. Drug release over five minutes ranged from about 81.8 to 95.2 percent, with formulations A1 and A6 performing best. The regression analysis revealed that both polymers increased drug release, but pullulan’s linear coefficient, 4.80, was nearly three times that of polyvinyl alcohol, 1.69, confirming that the hydrophilic polysaccharide was the dominant driver of dissolution. A low interaction coefficient showed the two polymers acted largely through their individual effects rather than synergistically on release.

Tensile strength told a complementary story. The strongest film, batch A1, withstood 12.8 newtons per square centimeter, a result attributed to high polymer concentrations producing dense chain entanglement and extensive hydrogen bonding. But excessive rigidity can compromise elasticity and patient comfort during periodontal application, so the strongest film was not necessarily the best. Batches with low polymer content, A2 through A5, ranged from just 1.02 to 5.23 newtons per square centimeter, reflecting weak matrix cohesion. Batch A6, with moderate polymer levels, achieved 10.78 newtons per square centimeter, striking what the authors describe as the ideal balance between structural stability and flexibility. The statistical models for both responses were validated by analysis of variance, with model F-values of 119.88 for drug release and 22.51 for tensile strength, and prediction errors for the optimized batch of only 0.41 percent for release and 2.13 percent for mechanical strength.

The optimized formulation, containing 300 milligrams of pullulan and 200 milligrams of polyvinyl alcohol, was then put through a full battery of characterization tests. The yellow film was uniform and smooth, with an average thickness of 0.06 millimeters, a weight of 0.0125 grams, and a folding endurance of 200 folds, indicating robust mechanical integrity. Its pH of 6 falls within the natural range of the oral cavity during gingival infections, minimizing irritation risk, and it disintegrated completely in about one minute, enabling rapid drug release. In-vitro diffusion through a cellophane membrane reached 78.6 percent over 70 minutes, notably longer than the five-minute release window, because only one side of the film contacted the membrane. When tested against fresh sheep gingival mucosa, ex-vivo diffusion reached 65.1 percent, with a steady-state flux of 0.93 micrograms per square centimeter per minute, about 16 percent lower than the in-vitro value, a reduction the researchers attribute to the additional diffusional and partitioning resistance of biological tissue.

Perhaps the most striking results came from the antimicrobial testing. Using an agar-well diffusion assay, the optimized film produced a zone of inhibition of 35 millimeters against Pseudomonas aeruginosa and 28 millimeters against Candida albicans. A plain pullulan film without drug showed much smaller zones, 18 and 22 millimeters respectively, meaning the drug-loaded film enlarged the inhibition zone by 94.4 percent against the bacterium and 27.3 percent against the fungus, differences that were statistically significant. The particularly large effect against Pseudomonas aeruginosa makes mechanistic sense, since that organism depends directly on the PFOR pathway that amixicile disables, whereas the eukaryotic fungus is affected through a less direct route. These findings suggest the film could suppress both the bacterial and fungal contributors to periodontal infection at the site where they do their damage.

The broader significance of this work lies in its approach to a stubborn clinical problem. Deep periodontal pockets, those exceeding four millimeters, are often inaccessible to thorough cleaning because of tooth structure, which is precisely why localized delivery systems that place antimicrobials directly at the infection site, prolonging drug contact time while limiting systemic exposure, have attracted so much research attention. A dissolvable film that releases over 95 percent of its drug within minutes, then sustains diffusion for over an hour, could offer clinicians a non-invasive, easy-to-insert option that avoids the resistance risks of systemic antibiotics. The authors are careful to note that the road to the clinic is not yet complete: preclinical periodontal efficacy testing, mucosal safety and toxicity studies, bioadhesion and residence time measurements, microbiological efficacy against clinically relevant periodontal organisms, and eventually clinical trials will all be required before therapeutic use can be established. Still, the convergence of a mechanistically novel antimicrobial, well-characterized biocompatible polymers, and rigorous statistical optimization makes this amixicile film a compelling candidate in the fight against a disease poised to affect billions.

Subject of Research: Development of an amixicile-loaded pullulan and polyvinyl alcohol composite film for localized drug delivery in periodontitis treatment

Article Title: Amixicile loaded polyvinyl alcohol and pullulan composite film for localized periodontal treatment

Article References: Kandekar, U., Davkare, P., Pandit, A., Chaudhari, P., Chavan, M., Sayare, A., & Kolhe, R. (2026). Amixicile loaded polyvinyl alcohol and pullulan composite film for localized periodontal treatment. Discover Chemistry, 3(1), Article 573. https://doi.org/10.1007/s44371-026-01011-x

Image Credits: AI Generated

DOI: 10.1007/s44371-026-01011-x

Keywords: amixicile, periodontitis, pullulan, polyvinyl alcohol, drug delivery film, PFOR inhibitor, antimicrobial, periodontal pocket, solvent casting, central composite design, Pseudomonas aeruginosa, Candida albicans

The central innovation lies in the finishing chemistry applied to the cotton. Rather than relying on leaching biocides or heavy-metal coatings, the researchers built a multilayer dye-finishing design that incorporates two photoactive compounds directly into the textile. When these compounds absorb visible light, they enter an excited state and transfer energy or electrons to surrounding oxygen molecules, generating a highly reactive form of oxygen at the fabric surface. This reactive oxygen species attacks the cell membranes, proteins and genetic material of microorganisms that adhere to the fibers, damaging them beyond repair and thereby eliminating them from the textile. Because the killing mechanism is physical and photochemical rather than pharmacological, it does not depend on a specific molecular target that microbes could easily mutate around, and it is refreshed continuously as long as the fabric remains illuminated.

“The material incorporates two photoactive compounds which, when exposed to light, generate a highly reactive form of oxygen that damages the microorganisms adhering to the fabric, thereby eliminating them,” explains Alberto Blázquez-Moraleja of the ITQ CSIC-UPV. The description captures the essence of photodynamic antimicrobial action, a principle long studied in water treatment and surface disinfection but notoriously difficult to translate into a durable, washable textile. Dyes and photosensitizers tend to wash out, migrate, or photobleach over time, which is precisely why many antimicrobial fabrics on the market lose efficacy after a handful of laundering cycles. The multilayer architecture reported by the Spanish team appears to anchor the photoactive chemistry in a way that survives the mechanical and chemical stress of domestic and hospital washing.

The motivation behind the project is explicitly practical. “We aim to develop fabrics capable of reducing the presence of microorganisms such as bacteria, fungi and viruses in hospitals and other healthcare settings, thereby mitigating some of the problems associated with conventional antimicrobials, such as a loss of efficacy with use or when washed, or the promotion of resistant microorganisms. And that is precisely what we have achieved in this study,” says Marilés Bonet of the Textile and Paper Engineering Department at the UPV’s Alcoy campus. Her point about resistance is significant. Antibacterial surfaces and coatings that slowly release biocides can create selective pressure that favors tolerant strains, whereas light-driven generation of reactive oxygen delivers an acute, non-specific oxidative assault that leaves little room for microbes to adapt.

The laboratory performance data are striking. Under illumination, the treated fabric completely inactivated Escherichia coli, a Gram-negative bacterium whose outer membrane typically makes it harder to kill than Gram-positive species, within 60 minutes. Enterococcus faecalis, a Gram-positive organism and a common culprit in hospital-acquired infections, was completely inactivated even faster, within 20 minutes of light exposure. The fabric also achieved a measurable reduction in Candida albicans, an opportunistic fungal pathogen, within three hours. This breadth of activity, spanning Gram-negative and Gram-positive bacteria as well as fungi, and extending to viruses as the team reports, is what distinguishes a genuinely useful self-disinfecting textile from materials that target only a narrow slice of the microbial world.

Durability, the historical Achilles heel of antimicrobial textiles, was tested through repeated laundering. “The material also retains a significant proportion of its activity after repeated washes. Even after 20 cycles, it maintained a bactericidal efficacy above the reference levels used for antimicrobial fabrics,” says Pilar Moya of the UPV’s Research Institute for Mediterranean Agroforestry. Twenty wash cycles is a meaningful benchmark in the textile industry, since fabrics in clinical environments are laundered frequently and at high temperatures with aggressive detergents. A treatment that survives that regime while remaining above recognized antimicrobial reference thresholds suggests the photoactive layers are chemically bonded or structurally integrated with the cotton fibers rather than merely deposited on their surface.

Perhaps the most compelling part of the study is its validation outside the laboratory. The team tested the fabric in the rooms of 12 patients at La Fe University and Polytechnic Hospital in Valencia, placing samples in two locations for 48 hours. Bed rails, which receive ambient room light, represented the illuminated scenario, while mattresses, which receive far less light, represented a shaded condition. Untreated cotton fabrics placed under identical conditions served as controls. This design allowed the researchers to measure not just whether the material works, but how much its performance depends on the lighting conditions of a real clinical space, where illumination varies dramatically from windowsill to under-bed shadow.

The results confirmed both the promise and the limits of the technology. “In the hospital rooms, the fabric exposed to light accumulated 75% fewer microorganisms than a conventional cotton fabric placed under the same conditions. When the material was placed in an area without direct light, the reduction was much lower, just 25%, confirming that its antimicrobial effect depends largely on lighting. The efficacy was particularly high against Gram-positive bacteria, with their presence reduced by 77.5%,” notes Inmaculada Andreu of the UPV-IIS La Fe Joint Research Unit. A 75 percent reduction in microbial burden on a frequently touched surface such as a bed rail, achieved passively and continuously, would represent a meaningful addition to hospital infection-control programs. The 25 percent reduction in low-light zones, however, makes clear that placement matters: the technology complements rather than replaces cleaning protocols, and it performs best on surfaces with good access to visible light.

From a manufacturing standpoint, the outlook is encouraging. The researchers emphasize that the process used to produce the fabric could be easily integrated into standard textile-finishing techniques, the same industrial steps used to apply dyes, water repellents and flame retardants at scale. That compatibility means self-disinfecting hospital linens, curtains and covers would not require exotic production lines or fundamentally new supply chains; existing mills could, in principle, adopt the multilayer dye-finishing design with modest adjustments. Given that healthcare-associated infections affect hundreds of millions of patients worldwide each year and that contaminated soft surfaces are a recognized contributor to transmission, a scalable, washable, light-powered antimicrobial textile addresses a genuine unmet need.

The study, titled “Light-Driven Antimicrobial Cotton Fabric: Multilayer Dye-Finishing Design and Hospital Environment Validation,” appeared in ACS Applied Materials & Interfaces and stands as a rare example of an antimicrobial material moving from bench chemistry through standardized laboratory testing into an authentic hospital environment within a single research program. The combination of visible-light activation, broad-spectrum efficacy, resilience through 20 wash cycles and real-world validation gives the material a credible path from prototype to product. If subsequent studies replicate these findings at larger scale and confirm long-term safety for patients and staff, hospital rooms of the future may rely on fabrics that quietly sanitize themselves every time the lights are on, turning one of the most humble elements of the clinical environment into an active line of defense against infection.

Subject of Research: A light-activated antimicrobial cotton fabric for reducing microbial contamination in hospital settings

Article Title: A self-disinfecting fabric eliminates bacteria, fungi and viruses in hospital settings

Article References: A self-disinfecting fabric eliminates bacteria, fungi and viruses in hospital settings. (n.d.). Original publication

Image Credits: AI Generated

DOI: Not provided

Keywords: antimicrobial fabric, self-disinfecting textile, reactive oxygen species, hospital-acquired infections, photodynamic inactivation, cotton finishing, Escherichia coli, Enterococcus faecalis, Candida albicans, La Fe Hospital, ACS Applied Materials & Interfaces, Universitat Politècnica de València