MICROSPHERES AS ADVANCED DRUG CARRIERS: INNOVATIONS IN CONTROLLED DRUG DELIVERY

Microspheres have emerged as a highly versatile and scientifically advanced platform for controlled, sustained, and targeted drug delivery applications. These spherical particulate systems, typically ranging from 1 to 1000 µm in diameter, are engineered from biodegradable synthetic polymers, natural biopolymers, lipids, or inorganic materials to encapsulate therapeutic agents with high efficiency and stability. The structural architecture of microspheres—whether matrix-type or reservoir-type—enables precise modulation of drug release kinetics through mechanisms including diffusion, polymer degradation, erosion, and swelling-controlled transport. By optimizing physicochemical parameters such as polymer molecular weight, copolymer ratio, particle size distribution, surface morphology, and encapsulation efficiency, microspheres can be tailored to achieve predictable in vitro and in vivo release profiles. The clinical significance of microsphere-based delivery systems lies in their ability to enhance therapeutic efficacy, reduce systemic toxicity, improve bioavailability, protect labile biomolecules from enzymatic or hydrolytic degradation, and minimize dosing frequency. Advanced fabrication techniques including emulsion–solvent evaporation, spray drying, phase separation (coacervation), ionic gelation, and microfluidics have enabled scalable and reproducible production of microspheres with controlled characteristics. Furthermore, functionalization strategies such as surface modification, ligand conjugation, and stimuli-responsive polymer incorporation have expanded their applications in targeted cancer therapy, vaccine delivery, hormone therapy, ocular and pulmonary administration, and regenerative medicine. Despite their advantages, challenges such as initial burst release, scale-up complexity, sterilization constraints, polymer-associated toxicity, and regulatory compliance remain critical considerations in translational development. Ongoing advancements in polymer science, nanotechnology integration, and precision medicine are expected to drive the next generation of intelligent and multifunctional microsphere systems capable of responsive and personalized drug delivery.