Natural Macromolecules as Building Blocks for Microcapsule Formation in Drug Delivery

Background/Objectives: Microcapsules are particles 1–1000 µm in size, with a core containing the active substance (in liquid, solid, or gaseous state) and a shell typically composed of natural, synthetic, or semi-synthetic polymers. Although natural polymer-based microcapsules have applications in food, cosmetics, and other industries, this review primarily focuses on their role in pharmaceutical drug delivery. In recent years, natural macromolecules have gained increasing attention as coating materials due to their biocompatibility, biodegradability, low toxicity, mucoadhesive properties, and ability to enable controlled and targeted drug release. Based on previous research, this review provides an overview of microcapsules, the most common microencapsulation methods, natural polymers used as wall materials, and their pharmaceutical applications across different routes of administration. Results: By encapsulating active ingredients, microcapsules enhance their bioavailability, prolong their release, protect them, enable targeted delivery, and mask unpleasant tastes and odors. Among the most commonly used microencapsulation techniques are physical methods (spray drying, spray cooling, solvent evaporation, spray coating, and freeze drying) and physicochemical methods (coacervation). Natural polymers, particularly polysaccharides and proteins, have been successfully used in oral, topical, transdermal, pulmonary, and colon-targeted drug delivery systems, as well as for the stabilization and delivery of peptides, proteins, probiotics, and vaccines. Conclusions: Proper selection of microencapsulation technique depends on the properties of the polymer and the core material. Natural polymers represent versatile pharmaceutical excipients owing to their biocompatibility, biodegradability, safety, mucoadhesive behavior, and ability to provide controlled and targeted drug delivery. Their successful application with a wide range of therapeutic agents and administration routes highlights their considerable potential for the development of advanced drug delivery systems.