Novel HSA-PMEMA Nanomicelles Prepared via Site-Specific In Situ Polymerization-Induced Self-Assembly for Improved Intracellular Delivery of Paclitaxel.

Background/Objectives: Paclitaxel (PTX) is a potent anticancer drug that is poorly soluble in water. To enhance its delivery efficiency in aqueous environments, amphiphilic polymer micelles are often used as nanocarriers for PTX in clinical settings. However, the hydrophilic polymer segments on the surface of these micelles may possess potential immunogenicity, posing risks in clinical applications. To address this issue, nanomicelles based on human serum albumin (HSA)-hydrophobic polymer conjugates constructed via site-specific in situ polymerization-induced self-assembly (SI-PISA) are considered a promising alternative. The HSA shell not only ensures good biocompatibility but also enhances cellular uptake because of endogenous albumin trafficking pathways. Moreover, compared to traditional methods of creating protein-hydrophobic polymer conjugates, SI-PISA demonstrates higher reaction efficiency and better preservation of protein functionality. Methods: We synthesized HSA-PMEMA nanomicelles via SI-PISA using HSA and methoxyethyl methacrylate (MEMA)-a novel hydrophobic monomer with a well-defined and stable chemical structure. The protein activity and the PTX intracellular delivery efficiency of HSA-PMEMA nanomicelles were evaluated. Results: The CD spectra of HSA and HSA-PMEMA exhibited similar shapes, and the relative esterase-like activity of HSA-PMEMA was 94% that of unmodified HSA. Flow cytometry results showed that Cy7 fluorescence intensity in cells treated with HSA-PMEMA-Cy7 was approximately 1.35 times that in cells treated with HSA-Cy7; meanwhile, HPLC results indicated that, under the same conditions, the PTX loading per unit protein mass on HSA-PMEMA was approximately 1.43 times that of HSA. These collectively contributed to a 1.78-fold overall PTX intracellular delivery efficiency of HSA-PMEMA compared to that of HSA. Conclusions: In comparison with HSA, HSA-PMEMA nanomicelles exhibit improved cellular uptake and higher loading efficiency for PTX, effectively promoting the intracellular delivery of PTX. Tremendous potential lies in these micelles for developing safer and more efficient next-generation PTX formulations for tumor treatment.