Alginate-Based Hydrogels and Particulate Systems: Preparation Techniques, Adaptations, and Utilizations in Pharmaceutical Delivery and Biomedical Research

Alginate, a naturally derived anionic polysaccharide largely extracted from brown algae, has become a versatile biomaterial for pharmaceutical and biomedical applications due to its exceptional biocompatibility, biodegradability, non-toxicity, and gentle gelation qualities. The peculiar block-copolymeric arrangement of alginate, composed of β-D-mannuronic acid (M) and α-L-guluronic acid (G) residues, governs its physicochemical, mechanical, and biological features via modifications in molecular weight, M/G ratio, and block distribution. This review critically analyzes recent developments in alginate-based hydrogels and particulate systems, focusing on extraction methods, structural characterization, and modification strategies designed to address inherent limitations, including inadequate mechanical strength, uncontrolled degradation, and restricted bioactivity. The impacts of ionic and covalent crosslinking techniques, including egg-box gelation, photo-crosslinking, dual-network formation, and thermo-responsive systems, on rheology, stability, swelling, and controlled drug release behavior are discussed. The paper highlights the expanding biological applications of alginate systems in regenerative medicine, tissue engineering, wound healing, controlled and targeted drug delivery, and cell encapsulation. Special emphasis is placed on in vivo efficacy, immunogenicity, toxicity assessments, and regulatory compliance, comprising FDA and EU approvals. We also look at new developments including injectable hydrogels, hybrid scaffolds, and stimuli-responsive alginate composites. Alginate-based platforms comprise a promising category of biomaterials, and continuous developments in molecular modification and crosslinking technologies are projected to boost their translational potential in next-generation pharmacological and biological applications. Keywords: Alginate hydrogels; Egg-box cross-linking; Bio-polymeric frameworks; Biomedical materials