The interplay of solvent-drug-protein interactions during albumin nanoparticles formulations for temozolomide delivery to brain cancer cells

Objectives: Temozolomide (TMZ), the first line for glioma therapy, suffers from stability at physiological pH. TMZ was selected as a challenging model drug for loading into human serum albumin nanoparticles (HSA NPs). Our aim is to optimise the conditions for TMZ loading into HSA NPs while ensuring TMZ stability. Methods: Blank and TMZ-HSA NPs were fabricated using the de-solvation technique and the effect of different formulation parameters was evaluated. Key findings: For blank NPs, crosslinking time had no significant effect on NPs' size while acetone produced significantly smaller particles than ethanol. Upon drug loading, though TMZ was stable in acetone and ethanol as single agents yet, ethanol-based NPs showed misleadingly high EE% due to drug instability in ethanol formulations as evident by the UV spectrum. The optimum conditions for drug-loaded particles were: 10 mg/ml HSA, 4 mg TMZ using acetone, yielded NPs with 145 nm in diameter, ζ of -16.98 mV and 0.16% DL. The selected formula reduced the cell viabilities of GL261 glioblastoma cells and BL6 glioblastoma stem cells to 61.9% and 38.3%, respectively. Conclusions: Our results corroborated that careful manipulation of TMZ formulation processing parameters is crucial for encapsulating such chemically unstable dug while simultaneously ensuring its chemical stability.