Gel Microparticles Based on Polymeric Sulfonates: Synthesis and Prospects for Biomedical Applications

Polyelectrolyte microspheres based on a polymer containing sulfonate groups are considered promising drug delivery systems for encapsulating drugs and ensuring their prolonged release. In this study, gel microparticles based on various sulfonate-containing polymers were formed, and their potential as drug delivery systems was evaluated, particularly for the controlled administration of the cytotoxic anthracycline antibiotic doxorubicin and the antifungal drug fuchsine. An undeniable advantage of such gel microspheres is the presence in their structure of sulfonate groups localized both in the surface layer and in the volume. The main monomers used were styrene-4-sulfonic acid sodium salt and 3-sulfopropyl methacrylate potassium salt; spherical, porous microparticles were obtained via free-radical reverse suspension polymerization. Microsphere properties (size, porosity, pore structure, electrical surface properties, and swelling) were tailored by changing the nature of the sulfonate, using a comonomer (vinyl acetate or ethyl acrylate), adding a co-solvent, or modulating the crosslinker composition, which influenced drug loading efficiency (doxorubicin, fuchsine). The gel-like structure of the microspheres was confirmed, and the sulfonate groups were found to be distributed throughout both the surface layer and the internal volume of the microspheres. A comparison was also made with non-porous polymer particles containing sulfonate groups. The sorption capacity of the gel microspheres for doxorubicin was 2.2 mmol/g, significantly higher than the 0.4 mmol/g observed for the non-porous reference particles. The obtained values of doxorubicin sorption on gel microspheres are over 60 times higher than the values reported in the literature.