Natural Polysaccharide-based Polyelectrolyte Complexes in Biomedical Applications: Fundamentals and Therapeutic Prospects

Polyelectrolyte complexes (PECs) have gained considerable attention in recent years as multifunctional materials for biomedical and pharmaceutical applications. PECs are formed by electrostatic interactions between anionic polymers (such as alginate, pectin, xanthan gum, gellan gum, inulin, carrageenan, and chondroitin sulphate) and cationic polymers (e.g., chitosan). Poly-electrolyte complexes provide a simple and effective strategy to design delivery systems with desirable properties such as biocompatibility, biodegradability, non-toxicity, and environmental responsiveness. PECs have the ability to incorporate and protect premature release of therapeutic molecules, including small molecules, peptides, proteins, and nucleic acids, under mild condi-tions, thereby ensuring enhanced stability, controlled release, and site-specific targeting. The cur-rent review highlights the classification of PECs based on origin, ionic nature, and composition, the basic fundamentals of PEC formation, underlying mechanisms, and factors that influence the stability of PECs, such as pH, ionic strength, charge density, molecular weight, and mixing conditions. Current advancements in polyelectrolyte complex-based delivery systems, such as hydrogels, nanoparticles, microparticles, multilayer films, and scaffolds, are explained with their biomedical and pharmaceutical applications in controlled drug delivery, tissue engineering, wound healing, and regenerative medicine. Continued research in polymer chemistry, nanotech-nology, and fabrication strategies is expected to advance PECs as promising carriers for next-generation therapeutic platforms.