Shellac as a renewable natural resin for pharmaceutical and biomedical applications: Properties, modification strategies, and emerging technologies

Abstract

Shellac is a renewable natural resin secreted from the lac insect “Kerria lacca”. According to its excellent film-forming ability, moisture-protective properties, thermoplastic behavior, and pH-responsive dissolution, shellac has been conventionally employed as a pharmaceutical enteric coating material. Nevertheless, its broader application is limited by several inherent drawbacks, including film brittleness, hydrophobicity, relatively slow dissolution at intestinal pH, and progressive loss of solubility during storage. This review discusses the chemical composition and physicochemical properties of shellac, with particular emphasis on strategies developed to overcome these limitations. These approaches include partial hydrolysis, salt formation, esterification, plasticization, polymer blending, particle engineering, and controlled thermal processing. In addition to its established use in enteric and colon-targeted drug delivery, shellac has been incorporated into floating dosage forms, micro- and nanoparticulate carriers, periodontal in situ delivery systems, biodegradable implants, wound dressings, and controlled-release formulations. More recently, its thermoplastic processability and pH-responsive characteristics have enabled its application in hot-melt extrusion and fused deposition modeling three-dimensional printing for the fabrication of personalized and site-specific drug delivery systems. Collectively, these developments demonstrate that shellac is not merely a traditional coating material but a versatile and sustainable platform for advanced pharmaceutical manufacturing and biomedical applications.