Shellac is a natural polyester resin widely used as a pharmaceutical and food coating material owing to its excellent barrier properties. However, its strong film-forming ability and aggregation tendency limit its application in the microscale coating of particulate drug carriers. Here, we developed a sequential ethanol-water solvent-exchange method to induce controlled shellac precipitation and microcoating formation on drug-loaded cellulose microbeads (CLMs). By gradually increasing the water content, shellac precipitation was directed onto CLM surfaces while suppressing macroscopic aggregation. Shellac solubility in ethanol-water mixtures was determined at 286.15, 296.15, and 306.15 K and analyzed using the Flory-Huggins theory, Hansen solubility parameters, and van't Hoff relationships. The results indicate that solvent exchange induces kinetically controlled nanoparticle-mediated precipitation, promoting preferential interfacial deposition on CLMs. These findings provide a thermodynamic framework for solvent-controlled shellac precipitation and demonstrate a mild strategy for preparing shellac-based enteric microcoatings for drug delivery and functional food applications.
Sharmin et al. (Fri,) studied this question.