Abstract

Novel anionic cross-linked hydrogel-based microparticles with controlled size, functionality, porosity, and morphology were synthesized via tailored precipitation polymerization of hydrophobic and hydrophilic monomers in the presence of dimethacrylate as a cross-linking agent. The resulting hydrogel microparticles (HG5), with a size of 250 ± 50 nm and a polydispersity index of 0.079, were readily dispersible in water and formed stable suspensions at physiological pH (7.2–7.4). Their physicochemical properties were comprehensively characterized using FT-IR, NMR, DLS, SAXS, TEM, and turbidimetry. HG5 efficiently incorporated albumin as a model antigen with a loading efficiency of 95%, forming stable hydrogel–protein complexes that maintained their hydrodynamic size and colloidal stability over one month of storage. Biological evaluation demonstrated low toxicity toward pseudonormal cell lines, with cell viability remaining above 50% at concentrations up to 5 mg/mL and no detectable apoptotic effects in HEK293 cells. Human peripheral blood mononuclear cells (PBMCs) were sensitive to HG5 exposure, exhibiting an IC50 of 0.52 mg/mL, while showing good hemocompatibility with hemolysis below 5%. HG5 significantly enhanced immunogenicity, increasing BSA-specific antibody levels by 1.9-fold compared to the immunization without adjuvant (p < 0.05). These findings demonstrate the potential of HG5 as a versatile platform for protein delivery and vaccine adjuvant development.

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