Researchers exposed HT-29 cells to 1% dextran sulfate sodium, or DSS, to create an inflammatory epithelial model, and then treated the cells with 50% L. brevis cell-free supernatant for 48 hours. Viability was assessed with an MTT assay before the transcriptional analysis. The investigators profiled the expression of 84 genes involved in Toll-like receptor, or TLR, signaling using the RT² Profiler PCR Array. Differential expression was evaluated with the ΔΔCt method, and raw p-values were adjusted for multiple testing using the Benjamini–Hochberg false-discovery-rate procedure.

The most prominent response was the significant downregulation of multiple genes associated with inflammation and innate immune signaling. These included the receptors TLR2 and TLR4; the adaptor proteins MYD88 and TIRAP; the kinases IRAK1, IRAK4 and MAP3K7; and the transcription factor NFKB1. Proinflammatory cytokine genes IL1A, IL1B, IL6 and IL12A also declined, as did the chemokine CCL2 and the cyclooxygenase gene PTGS2. At the pathway level, the affected genes mapped to the MyD88-dependent and TRIF-dependent branches of TLR signaling.

Host defense-associated genes responded differently from the broadly downregulated inflammatory set. Components associated with the TRIF-dependent antiviral axis—including TLR3, TICAM1, TBK1, IRF3 and CXCL10—were also significantly downregulated. In contrast, TLR1, TLR10, TICAM2 and BTK were upregulated. Several other examined immune-response genes showed no significant change. The mix of increased, decreased and unchanged transcripts indicates that the supernatant altered specific parts of the TLR-associated gene network rather than indiscriminately shutting down every immune-related pathway.

The findings provide a cell-level view of how secreted L. brevis metabolites may influence inflammatory signaling in intestinal epithelial cells. They are consistent with attenuation of multiple inflammation-associated transcriptional responses under DSS-induced stress, while also showing that changes in host defense-related genes are context dependent. The experiment was conducted in one human intestinal epithelial cell line exposed to an inflammatory stimulus, and the results concern gene expression rather than clinical outcomes in people. The study therefore does not establish that the supernatant prevents or treats inflammatory bowel disease, nor does it define which secreted components or molecular mechanisms produced the selective effects. Its principal conclusion is limited to the observed modulation of TLR-associated transcription in DSS-stimulated HT-29 cells.

Subject of Research: Transcriptional effects of Lactobacillus brevis cell-free supernatant on TLR-associated genes in DSS-stimulated intestinal epithelial cells

Article Title: Lactobacillus brevis cell-free supernatant attenuates inflammation-associated gene expression and differentially modulates host defense-associated genes in DSS-stimulated HT-29 cells

Article References: Moghanlou, A., Rasouli, S., Asadi Lanjavani, S., Falsafi, S., & Behrouzi, A. (2026). Lactobacillus brevis cell-free supernatant attenuates inflammation-associated gene expression and differentially modulates host defense-associated genes in DSS-stimulated HT-29 cells. Molecular Biology Reports, 53(1), Article 1764. https://doi.org/10.1007/s11033-026-12890-9

Image Credits: AI Generated

DOI: 10.1007/s11033-026-12890-9

Keywords: Lactobacillus brevis, cell-free supernatant, HT-29 cells, intestinal inflammation, Toll-like receptors, gene expression, innate immunity, dextran sulfate sodium, molecular biology, Lactobacillus, brevis, cell-free

Selenium compounds have been investigated in clinical trials for several cancers, but their effects depend heavily on how the element is metabolized. The study distinguishes two major reactive pools: hydrogen selenide (H₂Se), produced from compounds such as selenite, and CH₃SeH, associated with methylseleninic acid, methylselenocysteine and other precursors. Although H₂Se can exert antitumor effects, excessive amounts that exceed the threshold associated with selenoprotein biosynthesis can cause single-strand DNA cleavage, potentially narrowing the safety margin. CH₃SeH is described as comparatively nongenotoxic and acts through several reported mechanisms, including regulation of NKG2D ligands, caspase-mediated apoptosis, modulation of oxidative stress and suppression of VEGF-mediated angiogenesis.

Natural methylselenocysteine can release CH₃SeH through a pathway dependent on endogenous beta-lyase, while selenomethionine follows a different metabolic route and may not generate enough CH₃SeH at low micromolar concentrations to produce antitumor effects. Existing donors based on methylselenocarbamates and methylselenoesters have also shown pharmacological activity, but their release can be difficult to control and may have low conversion efficiency. The central objective was therefore to build a donor that remains stable under physiological conditions yet converts rapidly to CH₃SeH when a selected stimulus is present, allowing spatial and temporal control in living systems.

The first design attempt used classical quinone-methide self-immolative chemistry. An azide-bearing donor was reduced with tris-(2-carboxyethyl)phosphine in phosphate-buffered saline at pH 7.4 and 25 degrees Celsius. The initial reduction was rapid, with a bimolecular rate constant of 1.43 M^-1s^-1, but the intermediate then decomposed very slowly. Its self-immolative rate was 2.63 × 10^-6 s^-1, corresponding to a half-life of about 73 hours. This result showed why the chemistry required a different release mechanism for a drug designed to respond quickly to a biological or external signal.

To overcome that limitation, the researchers screened methylselenocarbamate structures for stability in water. Se-methyl N-phenylcarbamoselenoate decomposed rapidly in phosphate-buffered saline, with a half-life of 9.4 minutes, and produced aniline consistent with hydrolysis through an isocyanate intermediate. Adding a methyl group to the carbamate nitrogen produced Se-methyl N-phenyl-N-methylcarbamoselenoate, which was much more stable in buffer and in the presence of physiologically relevant thiols and amines. The modified scaffold therefore offered a more controllable foundation for constructing triggered donors.

The investigators then placed a Boc-protected amino group next to the stable methylselenocarbamate. At physiological pH, deprotonation of the amino group created a nucleophile that attacked the carbamate intramolecularly, causing rapid cyclization and release of CH₃SeH. The resulting product, TD-MSe1, converted with an observed rate constant of 0.14 s^-1 and a half-life of approximately 5 seconds at pH 7.4. Across the tested pH range, the reaction was faster at higher pH: its half-life fell from 2,654 seconds at pH 4.5 to 5 seconds at pH 7.4. Trapping experiments measured a CH₃SeH release efficiency of up to 94.2 ± 2.7%.

Fluorescent detection with the selenol-responsive probe Sel-green supported intracellular delivery. HeLa cells pretreated with the probe showed little fluorescence on their own, whereas incubation with TD-MSe1 produced a concentration-dependent signal over 30 minutes. The unmodified methylselenocarbamate did not trigger the same response, indicating that activation of the caged amine was required. The findings demonstrated that the engineered platform could release CH₃SeH inside living cells, although they did not establish behavior in animals or humans.

To make release dependent on an external signal, the researchers attached an o-nitrobenzyl group to the TD-MSe scaffold, creating the light-triggered donor TD-MSe2. The caged compound remained stable in phosphate-buffered saline at pH 7.4, including in the presence of physiologically relevant concentrations of thiols. Irradiation with 365-nanometre light induced decomposition, generating CH₃SeH and the expected cyclization byproduct. High-performance liquid chromatography and mass spectrometry detected the predicted products, while a trapping reagent independently captured the released selenol. In alternating light-and-dark experiments, photolysis stopped when the light was switched off and resumed when it was switched on; product formation exceeded 80% after irradiation.

TD-MSe2 also showed a measurable biological effect in cultured HeLa cells. The donor alone, whether irradiated for 120 seconds or not, produced negligible cytotoxicity under the reported conditions. By contrast, exposing cells to 400 micromolar hydrogen peroxide for two hours reduced viability to approximately 22%. Pretreatment with 30 or 100 micromolar TD-MSe2 followed by 120 seconds of irradiation raised viability to approximately 42% and 67%, respectively, while the same donor without irradiation did not provide protection. Longer photoactivation produced greater protection, and a reactive-oxygen-sensitive probe showed lower intracellular fluorescence in irradiated donor-treated cells. The authors propose that released CH₃SeH, including the diselenide dimethyldiselenide that can be reduced back to CH₃SeH in glutathione-rich cells, may support a catalytic cycle for removing reactive oxygen species.

The platform was also adapted for biological activation. The researchers attached a trimethyl-locked quinone trigger that can be removed by hNQO1, an oxidoreductase reported to be overexpressed in some metastatic cells, producing TD-MSe3. The compound remained stable in phosphate-buffered saline for more than 70 hours but reacted rapidly when hNQO1 and NADH were present, with release of the trigger intermediate exceeding 90%. Dicoumarol, an hNQO1 inhibitor, reduced the reaction in a concentration-dependent manner. In cell imaging, hNQO1-high HT-29 colorectal adenocarcinoma cells produced a strong Sel-green response after treatment with TD-MSe3, while low-hNQO1 HeLa cells showed negligible fluorescence. Pretreatment with dicoumarol reduced the signal in HT-29 cells, supporting dependence on endogenous enzyme activity.

In the anticancer tests, TD-MSe3 reduced HT-29 cell viability after 72 hours with a reported half-maximal inhibitory concentration of 23.4 micromolar, whereas the non-triggered control compound did not show appreciable cytotoxicity up to 150 micromolar. The donor had much higher half-maximal inhibitory concentrations above 200 micromolar in hNQO1-low HeLa and HUVEC cells, indicating selectivity in this in vitro comparison. A separate colony-formation assay found that 2 micromolar TD-MSe3 reduced HT-29 colony formation by more than 35% relative to untreated cells, and 10 micromolar nearly abolished colony formation. These experiments demonstrate preferential activity in an hNQO1-high cell model, but the study did not test tumors, animals, dosing, long-term safety or therapeutic benefit in patients.

Subject of Research: Stimulus-responsive methylselenol donor chemistry for controlled intracellular selenium delivery

Article Title: Harnessing Methylselenol (CH3SeH): A Highly Effective Platform for Stimuli‐Responsive Delivery With Therapeutic Potential

Article References: Liang, W., Wang, L., Wang, X., Li, X., Xing, H., Sun, L., Xi, Z., & Yi, L. (2026). Harnessing Methylselenol (CH 3 SeH): A Highly Effective Platform for Stimuli‐Responsive Delivery With Therapeutic Potential. Advanced Science, Article e78356. https://doi.org/10.1002/advs.78356

Image Credits: AI Generated

DOI: 10.1002/advs.78356

Keywords: methylselenol, drug delivery, cancer research, hNQO1, photocaging, reactive oxygen species, selenium chemistry, HT-29 cells, intracellular delivery, Harnessing, CH3SeH, Highly

Investigators used an NK3.3/HT-29 co-culture system to assess cytotoxicity. According to the abstract, IL-2–activated NK cells alone did not produce robust killing of HT-29 cells, whereas treatment with sLTA restored NK-mediated tumor-cell killing. The researchers also examined NK-cell receptor expression, tumor-cell apoptosis-related genes, and the contribution of soluble NK-derived cytokines to the observed effect.

At the NK-cell side of the model, sLTA increased expression of activating receptors, including NKG2D and natural cytotoxicity receptors. In HT-29 cells, it increased MICB expression and reduced expression of the anti-apoptotic genes Bcl-2 and others. siRNA-mediated knockdown and Western blot analysis supported involvement of caspase-3–dependent apoptosis. Transwell and neutralization experiments indicated that sLTA-primed HT-29 cells became more sensitive to contact-independent cytotoxicity mediated by NK-derived TNF-α and IFN-γ.

The authors characterized sLTA as a dual-action immune sensitizer: it enhanced NK-cell effector activity while lowering the apoptotic threshold in resistant tumor cells. This conclusion is based on laboratory co-culture and related assays described in the abstract. The available summary does not report testing in animals or humans, does not establish safety, and does not show that sLTA would improve NK-cell-based immunotherapy in clinical settings. Its potential use as an adjunct therefore remains a suggestion for further study rather than a demonstrated therapeutic outcome.

Subject of Research: In vitro effects of sLTA on natural killer cell cytotoxicity against HT-29 colon cancer cells

Article Title: Synergistic restoration of NK cell cytotoxicity against solid tumors via sLTA-mediated dual-action modulation

Article References: Choi, D., Kim, H., Kim, H., & Chung, D.-K. (2026). Synergistic restoration of NK cell cytotoxicity against solid tumors via sLTA-mediated dual-action modulation. Molecular Biology Reports, 53(1), Article 1583. https://doi.org/10.1007/s11033-026-12764-0

Image Credits: AI Generated

DOI: 10.1007/s11033-026-12764-0

Keywords: natural killer cells, lipoteichoic acid, HT-29 cells, colon cancer, cell culture, immunotherapy, tumor killing, apoptosis, NKG2D, MICB, Synergistic, restoration

Oncolytic virotherapy rests on a deceptively simple principle: certain viruses preferentially infect and destroy cancer cells while sparing normal tissue. Vaccine strains are particularly attractive for this purpose because they have been attenuated through decades of use in immunization programs, meaning their safety profiles in humans are already well characterized. Measles virus, for instance, enters cells through receptors such as CD46 and PVRL4 (nectin-4), both of which are overexpressed on many tumor types, and high CD46 receptor density has been shown to determine preferential killing of tumor cells by oncolytic measles virus. Mumps virus, meanwhile, uses sialic acid-containing receptors and its matrix protein has been shown to activate apoptotic pathways in human colorectal cell lines.

The research team, led by investigators at 108 Military Central Hospital and Vietnam Military Medical University in Hanoi, focused on HT-29 cells, a well-established human colorectal cancer cell line. The cells were cultured in Dulbecco’s Modified Eagle Medium and infected with measles virus alone, mumps virus alone, or a one-to-one combination of the two viruses, referred to as MM. Cell viability was measured using the MTT assay, while apoptosis was quantified by flow cytometry. The combination was assessed at 48, 72, and 96 hours after infection to determine whether the two viruses interacted synergistically rather than simply adding their effects.

The results were striking. Using the Chou-Talalay combination index method, a standard quantitative framework for evaluating drug and treatment interactions, the researchers found that the MM combination demonstrated synergistic effects at all three time points, with combination index values of 0.473 at 48 hours, 0.692 at 72 hours, and 0.633 at 96 hours. A combination index below 1.0 indicates synergy, meaning the combined treatment kills more cancer cells than would be expected from the sum of the two viruses acting independently. The MM-treated group also showed significantly lower cell viability compared with groups infected with a single virus.

Beyond simply reducing viability, the combination markedly increased the rate of apoptosis, the programmed cell death pathway that viruses can trigger in infected tumor cells. Flow cytometry revealed a significantly higher apoptotic rate in the MM-treated group compared with single-virus-infected groups. This is consistent with prior work showing that measles virus nucleoprotein induces apoptosis and modulates diverse functional proteins in cultured mammalian cells, while mumps virus matrix protein activates apoptotic pathways in colorectal cell lines. The two viruses appear to converge on cell death machinery from different angles, overwhelming the tumor cell’s survival mechanisms.

To translate these in vitro findings into a living system, the team established a nude mouse xenograft model, in which HT-29 colorectal cancer cells were implanted to form tumors that could be treated with the viral combinations. Nude mice lack a functional adaptive immune system, which allows human tumor xenografts to grow and permits researchers to evaluate direct oncolytic effects without the confounding influence of a full immune response. The animals were treated with measles virus alone, mumps virus alone, or the MM combination, and tumor growth, survival, and mortality were monitored over time.

The in vivo results reinforced the laboratory findings. The MM-treated group exhibited significantly slower tumor growth compared with single-virus-treated groups, with a p value of 0.001 or less. Survival was significantly prolonged in the combination group, and mortality was reduced. Perhaps most intriguingly, the researchers observed increased proportions of innate immune cell populations in the spleen of MM-treated animals. Although nude mice cannot mount a complete adaptive immune response, the innate immune compartment, including natural killer cells and other populations, can still be engaged by viral infection and tumor cell death, and this engagement may contribute to the overall antitumor effect.

The concept of combining vaccine-strain measles and mumps viruses is not entirely new. Previous studies by overlapping research groups have shown that this combination enhances oncolytic activity against a wide range of human solid malignancies and synergistically kills hematological cancer cells, with particular focus on acute myeloid leukemia. The current study extends this approach specifically to colorectal cancer, a disease for which oncolytic virotherapy has been explored but remains far from clinical application. Prior work has demonstrated natural oncolytic activity of live-attenuated measles virus against human lung and colorectal adenocarcinomas, and recombinant measles viruses blind to certain receptors have been engineered to target colorectal cancer cells.

The mechanistic rationale for synergy between these two paramyxoviruses is grounded in their distinct receptor usage and intracellular effects. Measles virus, a morbillivirus, exploits CD46, PVRL4, and signaling lymphocyte activation molecule receptors, while mumps virus uses α2,3-linked sialic acid trisaccharides. This receptor divergence means the two viruses can enter tumor cells through different molecular doorways, potentially infecting subpopulations of cells that might be resistant to one virus alone. Once inside, both viruses can trigger apoptosis through overlapping and complementary pathways, and the resulting tumor cell lysis releases damage-associated molecular patterns that can stimulate innate immune responses.

The study’s authors conclude that the MM combination demonstrated synergistic and superior oncolytic efficacy against HT-29 colorectal cancer cells compared with single-virus therapies in both in vitro and in vivo xenograft models. While these findings are encouraging, the research remains at the experimental stage, and the leap from nude mouse xenografts to human patients involves substantial hurdles, including the development of antiviral immunity in immunocompetent individuals, delivery of sufficient viral doses to tumor sites, and the need to demonstrate safety and efficacy in clinical trials. Nevertheless, the work adds to a growing body of evidence that common childhood vaccine viruses, long celebrated for preventing disease, may also hold therapeutic promise against one of the world’s most prevalent cancers.

Subject of Research: Oncolytic virotherapy

Article Title: Anti-cancer efficacy of combined vaccine-strain measles and mumps viruses against colorectal cancer: an experimental study

Article References: Hung, T. X., Tung, N. D., Huong, N. T., Hoa, D. T., & Cuong, L. D. (2026). Anti-cancer efficacy of combined vaccine-strain measles and mumps viruses against colorectal cancer: an experimental study. Molecular Biology Reports, 53(1), Article 1537. https://doi.org/10.1007/s11033-026-12724-8

Image Credits: AI Generated

DOI: 10.1007/s11033-026-12724-8

Keywords: measles virus, mumps virus, colorectal cancer, oncolytic virotherapy, HT-29 cells, apoptosis, xenograft model, vaccine strains, Anti-cancer, efficacy, combined, vaccine-strain

Bacteroides fragilis is one of the most abundant bacterial species colonizing the human colon, and its relationship with its host is famously double-edged. Certain strains carry a toxin gene and are strongly associated with promoting colorectal tumors, producing the so-called Bacteroides fragilis toxin that damages DNA and drives inflammation. Yet other strains, lacking this enterotoxin, have been linked in previous studies to beneficial or protective effects, including the suppression of tumor growth in experimental models. The Chinese team worked with a human-derived non-enterotoxigenic strain precisely because of this paradox: if the same species can both promote and restrain cancer, then the specific molecules each strain produces become the decisive variable. Identifying those molecules is the first step toward understanding the mechanism and, eventually, toward developing microbiota-based therapies.

The methodological heart of the study is an approach known as activity-guided fractionation, a strategy long used in natural product chemistry to find the active needle in a haystack of molecules. The researchers first grew their bacterial strain in liquid culture and collected the conditioned supernatant, the cell-free broth containing everything the bacterium had secreted into its environment. They then tested this crude material against HT-29 cells, a well-established human colorectal cancer cell line, to confirm that the supernatant indeed inhibited cell proliferation. With that baseline activity established, they began to chop the complex mixture into progressively simpler fractions, testing each one for anti-proliferative activity along the way. Only fractions that retained activity were carried forward, ensuring that the analytical effort concentrated on the parts of the mixture most likely to contain the bioactive molecules.

The fractionation pipeline was deliberately multi-stage. Ultrafiltration first separated the supernatant by molecular weight, dividing proteins and other large molecules from smaller metabolites. Solvent extraction then partitioned the material according to chemical properties, distinguishing hydrophilic components from those that dissolve in organic solvents. Finally, chromatography provided a finer resolution, separating molecules on the basis of their interactions with a stationary phase. At each step, the researchers returned to the HT-29 cell assay, tracking where the anti-proliferative activity went. This iterative process, in which biological activity is used as a compass for chemical purification, is what distinguishes the study from a purely descriptive catalog of bacterial proteins. It converts an overwhelming proteomic inventory into a focused set of suspects.

Once the active fractions had been identified, the team turned to liquid chromatography coupled with tandem mass spectrometry, or LC-MS/MS, to determine which proteins were present in each. In this technique, proteins are digested into peptides, separated by liquid chromatography, and then fragmented inside the mass spectrometer; the resulting fragmentation patterns allow researchers to infer the identity and sequence of the original proteins with high confidence. Comparative proteomic analysis across the active and inactive fractions revealed 41 candidate proteins consistently associated with the bioactive material. The comparison is the critical element: proteins found in active fractions but absent from inactive ones, or enriched in the former, become candidates, while proteins present everywhere are unlikely to explain the specific biological effect.

Functional annotation of these 41 candidates revealed striking patterns. Many of the proteins are involved in iron acquisition, a vital survival function for bacteria living in the iron-restricted environment of the gut, where hosts actively withhold this metal from microbes. Others belong to ATP-binding cassette transport systems, molecular pumps that use the energy of ATP hydrolysis to move substrates across bacterial membranes, and to protein secretion pathways, the machinery by which bacteria export molecules into their surroundings. The enrichment of these functional categories suggests that the bioactivity may be tied to the bacterium’s interactions with its environment, including its host, rather than to housekeeping functions inside the cell.

Perhaps the most intriguing bioinformatic finding concerns protein localization. A substantial proportion of the 41 candidates were predicted to reside in the bacterial outer membrane or to carry signal peptides, the short amino acid tags that direct proteins out of the cell. This distribution raises the possibility that some of the candidate proteins travel in or on outer membrane vesicles, small spherical blebs that Gram-negative bacteria such as Bacteroides release into their environment. Outer membrane vesicles have attracted intense interest in microbiome research because they can package proteins, lipids, and genetic material and deliver them to host cells, potentially modulating immune responses and signaling pathways. If the anti-proliferative molecules are indeed shuttled in vesicles, that would offer a plausible route by which a gut bacterium could influence the behavior of epithelial cells lining the colon.

The authors are careful to frame their findings as a candidate list rather than a proof of mechanism, and this caution is scientifically appropriate. Correlation between the presence of a protein in an active fraction and the fraction’s biological effect does not establish causation. Any of the 41 proteins, or some combination of them, could be responsible for the anti-proliferative activity, or the true effector could be a non-protein molecule that co-purified with them. The researchers explicitly state that the candidates should be regarded as associated with the bioactive fractions rather than confirmed functional effectors, and that the individual and combined roles of these proteins require direct experimental validation. Such validation would typically involve purifying each candidate, testing it alone and in combination on cancer cells, and knocking out or silencing the corresponding genes in the bacterium to see whether activity disappears.

The broader significance of the study lies in the growing recognition that gut microbiota-derived factors contribute to colorectal cancer progression and, potentially, to its prevention. Epidemiological and experimental work over the past decade has implicated bacterial metabolites, toxins, and cell surface components in virtually every stage of tumor development, from DNA damage to immune evasion. Yet the field has struggled with a fundamental problem: the gut contains hundreds of bacterial species producing thousands of molecules, and pinpointing which of them matter for a given disease outcome is enormously difficult. Studies like this one demonstrate a tractable path forward. By coupling a reductionist fractionation workflow with unbiased proteomics and rigorous bioinformatics, researchers can convert a vague observation, that a bacterium seems to influence cancer cells, into a concrete, testable molecular hypothesis.

Looking ahead, the framework established by the Zunyi Medical University team could be applied to other bacterial strains and other cancer models, and the 41 candidates themselves provide a rich starting point for mechanistic work. If one or more of these proteins is eventually confirmed to suppress colorectal cancer cell proliferation, it could inspire entirely new classes of therapeutics derived from the microbiome, whether as purified proteins, engineered bacterial strains, or vesicle-based delivery systems. Conversely, even negative results from follow-up validation would sharpen the field’s understanding of how bioactive fractions exert their effects. For now, the study stands as a careful, methodical piece of science: a reminder that the answers to some of the most pressing questions in cancer biology may be produced by organisms already living inside us, waiting to be identified one protein at a time.

Subject of Research: Proteomic identification of secreted Bacteroides fragilis proteins associated with anti-colorectal cancer activity

Article Title: Proteomic identification of secreted protein candidates mediating anti-colorectal cancer activity in a human-derived non-enterotoxigenic Bacteroides fragilis

Article References: Peng, Y., Huang, L., Chen, M., Yang, H., Gan, Y., Wang, N., Wang, M., Yang, Z., & Li, J. (2026). Proteomic identification of secreted protein candidates mediating anti-colorectal cancer activity in a human-derived non-enterotoxigenic Bacteroides fragilis. BMC Cancer. https://doi.org/10.1186/s12885-026-17063-2

Image Credits: AI Generated

DOI: 10.1186/s12885-026-17063-2

Keywords: Bacteroides fragilis, colorectal cancer, proteomics, microbiome, activity-guided fractionation, LC-MS/MS, outer membrane vesicles, HT-29 cells, secreted proteins, ABC transporters, iron acquisition, gut microbiota

The construction of the nanocarrier is a three-step chemical campaign. The team began with pristine single-walled carbon nanotubes and oxidized them in a sulfuric and nitric acid mixture, sonicating and refluxing the material for 24 hours to decorate the graphitic surface with carboxyl and hydroxyl groups. These oxygenated sites served as chemical handles for the next stage: grafting branched polyethyleneimine, or PEI, a polymer rich in amine groups, using epichlorohydrin under alkaline conditions. Finally, glucuronic acid — a glucose-derived molecule — was activated with EDC and NHS coupling chemistry and conjugated to the amine-bearing scaffold. The result is a nanotube wrapped in a layered corona that is simultaneously amine-rich, hydrophilic, and decorated with sugar moieties chosen for a very specific biological reason.

That reason lies in cancer metabolism. Tumor cells are famously addicted to glucose, a phenomenon known as the Warburg effect, and they satisfy their enormous metabolic appetite by overexpressing glucose transporters on their surfaces — most notably GLUT1, which is induced by hypoxia-driven signaling and correlates with aggressive tumor behavior and poor prognosis. Glucuronic acid, as a glucose analog, is a plausible ligand for these transporters, and glucose–drug conjugates such as glufosfamide have already exploited this route to smuggle cytotoxic payloads into cancer cells. By conjugating GlcA to the nanotube surface, the researchers aimed to combine this potential targeting capability with the pH-responsive behavior that PEI naturally confers, creating a carrier whose outer layer could interact with transporter-rich tumor cells while its polymer shell responds to acidity.

Characterization confirmed that the elaborate surface chemistry had worked without destroying the underlying nanotubes. Fourier-transform infrared spectroscopy showed the disappearance of the GlcA carbonyl peak after conjugation, alongside the amide signatures of PEI grafting. X-ray diffraction revealed only minor shifts in the graphitic planes, indicating that the crystalline carbon framework remained intact beneath the organic coating. Electron microscopy told a consistent story: scanning images showed a compact polymeric layer coating the interwoven nanotube network, while transmission electron microscopy captured the preserved tubular architecture with added surface roughness from the deposited polymer. Energy-dispersive X-ray analysis quantified the transformation dramatically — carbon content fell from 90.8 to 65.6 weight percent, while oxygen rose to 30.3 percent and nitrogen appeared at 4.1 percent, the unmistakable fingerprint of an amine-rich PEI layer and oxygenated sugar residues spread uniformly across the surface.

The adsorption experiments revealed how the drug binds and what governs the process. Loading was optimal at pH 4, where 5-fluorouracil — a weakly acidic drug with a pKa of 7.93 — exists predominantly in its neutral form and the protonated PEI chains expand to expose more binding sites. Under these conditions the carrier achieved an adsorption capacity of 17.6 milligrams per gram with 88 percent loading efficiency. Kinetic analysis showed the data fit a pseudo-second-order model with correlation coefficients exceeding 0.9999, indicating that the rate is controlled by the chemistry of bond formation rather than simple diffusion. The Freundlich isotherm best described the equilibrium, pointing to adsorption on a heterogeneous surface with multilayer coverage — a picture consistent with the continuous polymeric coating seen microscopically. Notably, the modification boosted the maximum adsorption capacity more than fivefold compared with unmodified oxidized nanotubes, from 17.65 to 90.61 milligrams per gram at 298 kelvin.

Thermodynamics added a crucial layer of insight. The negative enthalpy change of −22.6 kilojoules per mole confirmed the process is exothermic, which explains why adsorption weakened at elevated temperatures, and the negative Gibbs free energy values at all tested temperatures confirmed spontaneous binding. Perhaps most interesting was the negative entropy change of −40.5 joules per mole per kelvin, indicating that drug molecules adopt a more ordered, constrained arrangement on the modified surface. The authors suggest this molecular confinement could help stabilize drug–carrier interactions under physiological conditions, limiting premature release during circulation — precisely the failure mode that makes conventional chemotherapy so toxic to healthy tissue.

The release experiments are where the design truly earns its keep. Placed in a dialysis system at 37 degrees Celsius, the drug-loaded carrier released roughly 10.5 percent of its 5-fluorouracil within the first 30 minutes at pH 5.6, versus 6.5 percent at pH 7.4. The gap widened relentlessly: 52 percent versus 34 percent after six hours, 80 percent versus 47 percent after 24 hours, and finally 88 percent versus 52 percent at the 48-hour mark. The mechanism is electrostatic. In acidic conditions, PEI amine groups become protonated, the chains repel one another and expand, and the matrix swells — loosening the network, weakening drug–carrier interactions, and opening the enlarged mesopores, which BET measurements showed had grown from 18.2 to 41.1 nanometers after functionalization. At physiological pH, reduced protonation keeps the polymer compact, trapping the drug inside a denser network.

Mathematical modeling of the release kinetics revealed a non-Fickian, or anomalous, transport mechanism. The Peppas–Sahlin equation gave the best fit with correlation coefficients of 0.999, and the diffusional exponent from the Korsmeyer–Peppas model fell between 0.5 and 1 under both pH conditions. This means release is governed not by diffusion alone but by a combination of drug diffusion through the matrix and simultaneous polymer relaxation and swelling — a dual mechanism that gives the carrier its tunable, sustained profile. The Higuchi release constant was markedly higher at acidic pH, confirming that the tumor-like environment accelerates delivery exactly when and where it matters therapeutically.

Biological testing on human colorectal cancer cells, HT-29, provided the first evidence that the chemistry translates into cellular effects. Using the MTT viability assay, the unloaded carrier showed acceptable cytocompatibility at low concentrations, with viability near untreated controls at 0.5 to 5 micrograms per milliliter, declining gradually to about 52 to 54 percent at the highest doses. The drug-loaded formulation diverged clearly from 50 micrograms per milliliter onward, reducing viability to approximately 60 percent compared with 77 percent for the bare carrier — a difference attributable to the biological activity of the delivered 5-fluorouracil. Importantly, the decline was progressive and concentration-dependent rather than abrupt, consistent with a moderated drug-availability profile rather than the sudden cytotoxic burst typical of free chemotherapeutics.

The study stops short of clinical claims, and appropriately so. The authors emphasize that further work on cellular uptake and in vivo evaluation is needed before the platform’s transporter-targeting potential and therapeutic efficacy can be established. Carbon nanotubes also carry well-known baggage — poor aqueous solubility and slow systemic clearance — that functionalization strategies like this one are designed to mitigate but not necessarily eliminate. Still, the convergence of results is compelling: a fivefold boost in drug capacity, thermodynamically stabilized binding, an 88-versus-52 percent release differential between tumor-like and physiological pH, and dose-dependent killing of colorectal cancer cells in vitro. Together they sketch a nanocarrier that loads like a sponge, travels like a locked vault, and opens like a key in the acidic lock of the tumor microenvironment — a design philosophy that may shape the next generation of stimulus-responsive cancer therapies.

Subject of Research: pH-responsive carbon nanotube-based nanocarriers for controlled delivery of the chemotherapy drug 5-fluorouracil

Article Title: Polyethyleneimine/Glucuronic acid-grafted carbon nanotubes for 5-fluorouracil delivery: adsorption optimization, pH-responsive release, and in-vitro cytotoxicity

Article References: badiee, N., Miralinaghi, P., Miralinaghi, M., & Serri, A. (2026). Polyethyleneimine/Glucuronic acid-grafted carbon nanotubes for 5-fluorouracil delivery: adsorption optimization, pH-responsive release, and in-vitro cytotoxicity. Journal of Saudi Chemical Society, 30(2), Article 15. https://doi.org/10.1007/s44442-026-00058-w

Image Credits: AI Generated

DOI: 10.1007/s44442-026-00058-w

Keywords: carbon nanotubes, drug delivery, 5-fluorouracil, polyethyleneimine, glucuronic acid, pH-responsive release, nanomedicine, chemotherapy, HT-29 cells, adsorption kinetics, cancer therapy, nanocarriers