The rationale for the approach lies in the peculiar biology of glioblastoma. These tumors are notoriously oxygen-starved because their blood vessels are underdeveloped and chaotic. That hypoxia activates hypoxia-inducible factor 1, or HIF-1, a master transcription factor that drives angiogenesis, metabolic reprogramming, and drug resistance by upregulating efflux pumps. Photodynamic therapy, which uses a photosensitizer and light to generate reactive oxygen species that destroy tumor cells, makes the problem worse: it consumes oxygen and damages tumor microvessels, deepening the hypoxia and paradoxically boosting HIF-1 activity. Photothermal therapy, which kills cells with heat, triggers its own countermeasure in the form of heat shock proteins, particularly HSP70, which help tumor cells survive thermal stress and develop thermoresistance.

To exploit light-based therapy despite these obstacles, the team first optimized the ratio of IR780 to paclitaxel inside bovine serum albumin nanoparticles. Using the combination index method, a standard quantitative tool for drug synergy, they found that a 1:2 ratio of IR780 to paclitaxel yielded a combination index of 0.39, well below the threshold of 1 that indicates true synergism. The resulting nanoparticles measured roughly 168 nanometers in hydrodynamic diameter by dynamic light scattering, with polydispersity indices around 0.1, indicating a highly uniform population. Transmission electron microscopy revealed spherical particles of approximately 120 nanometers. Encapsulation efficiency was high, at 89.8 percent for IR780 and 84.4 percent for paclitaxel, and the particles remained colloidally stable for at least 72 hours at room temperature.

The photophysical performance of the encapsulated dye proved markedly superior to the free drug. Under 808-nanometer near-infrared irradiation, free IR780 raised solution temperature by about 18 degrees Celsius within five minutes before its effect collapsed, a consequence of photobleaching. The albumin-encapsulated version, by contrast, generated roughly 25 degrees of heating and sustained it for at least ten minutes without decline. The nanoparticles also withstood at least four heating-cooling cycles, while free IR780 survived only one. Ultraviolet-visible spectroscopy showed a red shift in the dye’s absorption peak from 770 to about 790 nanometers, attributed to molecular aggregation within the particles, which improved excitation at 808 nanometers. Reactive oxygen species generation, measured with the chemical probe DPBF, was equally robust, and adding paclitaxel did not diminish the dye’s photodynamic output.

In LN229 human glioma cells, the nanoparticles were taken up faster than free IR780, and the team traced the mechanism to albumin-specific pathways. Pretreating cells with free albumin competitively blocked nanoparticle internalization in a concentration-dependent manner, consistent with uptake mediated by proteins such as SPARC and gp60, both overexpressed in glioblastoma. Once inside, the nanoparticles localized to lysosomes, where near-infrared irradiation disrupted lysosomal membranes, as shown by acridine orange staining, facilitating the escape and release of paclitaxel. Irradiated cells loaded with the nanoparticles heated about 15 degrees Celsius in four minutes, compared with roughly 10 degrees for free dye, and produced visibly more reactive oxygen species.

But the irradiation also exposed the therapy’s Achilles heel. A hypoxia-sensitive fluorescent probe revealed that photodynamic treatment significantly increased oxygen deprivation in the cells, and western blotting showed HIF-1α expression rising by 56 percent after irradiation. Under simulated hypoxia, the potency of both phototherapy and chemotherapy dropped substantially: the half-maximal inhibitory concentration of the combined nanoparticles rose from 0.08 to 0.48 micrograms per milliliter of IR780 equivalent. This is precisely where acriflavine entered the picture. When added to the treatment, the drug, which binds the HIF-1α subunit and prevents its dimerization with HIF-1β, further reduced the inhibitory concentrations to 0.32 and 0.63 micrograms per milliliter for IR780 and paclitaxel respectively under hypoxic conditions, and drove apoptosis, measured by cleaved caspase-3, to its highest levels.

The most striking discovery came when the team examined heat shock protein expression. Acriflavine alone suppressed HSP70 by roughly 80 percent compared with controls, and when combined with the nanoparticles it brought HSP70 levels down even under photothermal stress. To the authors’ knowledge, this is the first report of acriflavine acting as a potent HSP70 inhibitor, meaning a single molecule simultaneously blocks the hypoxia response that undermines photodynamic therapy and the thermoresistance that blunts photothermal therapy. The combination also nearly abolished glioma cell migration and invasion in scratch and Transwell assays, an effect the researchers linked to acriflavine’s suppression of HIF-1 downstream targets including VEGF, GLUT-1, and MMP9, proteins that drive angiogenesis, glucose uptake, and metastasis.

In tumor-bearing mice, the nanoparticles accumulated preferentially in tumors after intravenous injection, peaking at 24 hours, while free IR780 showed far weaker tumor localization. Acriflavine was delivered differently: because it is highly water-soluble and clears quickly from the body, the team embedded it in sodium alginate that gels on contact with the physiological calcium found inside tumor tissue, releasing the drug for at least 72 hours. In the treatment study, nanoparticles plus acriflavine hydrogel under near-infrared irradiation suppressed tumor growth by essentially 100 percent from day six onward, and three of five mice in that group showed complete tumor elimination. Histology confirmed the most extensive cellular destruction and the highest apoptotic fractions in the combination group. Tumors heated by 17 degrees Celsius within five minutes of irradiation, and HSP70 expression in treated tumors fell below even the untreated control level.

Safety signals were encouraging. Body weights remained stable across all treatment groups, organ histology showed no lesions, hemolysis stayed below 5 percent even at high nanoparticle concentrations, and blood chemistry markers of liver and kidney function showed no significant differences between treated and control animals. The authors are candid about limitations: the efficacy studies used a subcutaneous model rather than an orthotopic brain tumor, which lacks the blood-brain barrier and invasive growth patterns of real glioma, and the two delivery systems remain separate formulations. Still, both platforms have clinical precedents, from the FDA-approved albumin-paclitaxel formulation Abraxane to carmustine wafers implanted in post-surgical brain cavities. By showing that one repurposed, clinically approved dye can neutralize both HIF-1 signaling and heat shock defenses at once, the study offers a compelling template for reinforcing combination therapy in hypoxic, treatment-resistant tumors.

Subject of Research: Albumin nanoparticle photochemotherapy with acriflavine-mediated HIF-1 and HSP70 inhibition for glioma treatment

Article Title: Acriflavine-empowered IR780-PTX albumin nanoparticles for reinforced synergistic photochemotherapy

Article References: Li, D., Wang, T., Liu, H., Yao, Y., Lu, T., Wang, R., Jiang, X., Zhang, X., Sun, M., Peng, Y., Yang, Y., Shao, N., Ding, D., & Zhi, F. (2026). Acriflavine-empowered IR780-PTX albumin nanoparticles for reinforced synergistic photochemotherapy. Advanced Biotechnology, 4(1), Article 10. https://doi.org/10.1007/s44307-026-00097-9

Image Credits: AI Generated

DOI: 10.1007/s44307-026-00097-9

Keywords: glioblastoma, albumin nanoparticles, photothermal therapy, photodynamic therapy, paclitaxel, IR780, acriflavine, HIF-1, HSP70, tumor hypoxia, drug delivery, combination therapy