Multiscale Shellac-Based Delivery Systems: From Macro- to Nanoscale

Delivery systems play a crucial role in enhancing the activity of active substances; however, they require complex processing techniques and raw material design to achieve the desired properties. In this regard, raw materials that can be easily processed for different delivery systems are garnering attention. Among these raw materials, shellac, which is the only pharmaceutically used resin of animal origin, has been widely used in the development of various delivery systems owing to its pH responsiveness, biocompatibility, and degradability. Notably, shellac performs better on encapsulating hydrophobic active substances than other natural polymers, such as polysaccharides and proteins. In addition, specially designed shellac-based delivery systems can also be used for the codelivery of hydrophilic and hydrophobic active substances. Shellac is most widely used for oral administration, as shellac-based delivery systems can form a compact structure through hydrophobic interaction, protecting transported active substances from the harsh environment of the stomach to achieve targeted delivery in the small intestine or colon. In this review, the advantages of shellac in delivery systems are discussed in detail. Multiscale shellac-based delivery systems from the macroscale to nanoscale are comprehensively introduced, including matrix tablets, films, enteric coatings, hydrogels, microcapsules, microparticles (beads/spheres), nanoparticles, and nanofibers. Furthermore, the hotspots, deficiencies, and future perspectives of shellac-based delivery system development are also analyzed. We hoped this review will increase the understanding of shellac-based delivery systems and inspire their further development.

Assessment of the effect of polymers combination and effervescent component on the drug release of swellable gastro-floating tablet formulation through compartmental modeling-based approach

The aim of this research was to assess the effect of polymer blend and effervescent components on the floating and swelling behaviors of swellable gastro-floating formulation as well as the drug release through a compartmental modeling analysis. Swellable gastro-floating formulation of freely water-soluble drug, metformin HCl as a drug model, was formulated and developed using D-optimal design. Polymer combination between interpolymer complex (IPC) (poly-vinyl acetate-copolymer methacrylate) and hydroxy propyl methyl cellulose (HPMC), and effervescent components were studied and optimized in this work. Several factors affecting the drug release behavior were determined e.g. swelling behavior, erosion behavior, and floating behavior were studied as well as the drug release through compartmental modeling analysis. The results revealed that the hydrophilic polymer was responsible for gas entrapment formed from effervescent reaction, meanwhile IPC contributed on maintaining the swollen matrix integrity through intermolecular polymer interaction. In addition, effervescent components played fundamental role in the formation of porous system as well as inducing burst release effect. Compartmental modeling provided different outlook about the drug release. Presence of IPC at a high proportion (10-15%) of the polymer blend modulated the changes of pattern of the drug release kinetics and mechanism. Finally, compartmental modeling-based approach was more adequate to describe the drug release kinetics and mechanism compared to the monophasic equation model correlating with process understanding of the drug release from swellable gastro-floating formulation.

Reducing Burst Release Effect of Freely Water-Soluble Drug Incorporated into Gastro-Floating Formulation Below HPMC Threshold Concentration Through Interpolymer Complex

Undesired-burst release effect is observed in a freely water-soluble drug formulated into a gastro-floating formulation with effervescent (GFFE) delivery system. In order to address this limitation, interpolymer complex (IPC) of two swellable and non-soluble polymers, poly-ammonium methacrylate and poly-vinyl acetate, was incorporated into hydroxypropyl methyl cellulose (HPMC)-based matrix GFFE. This research studied the effect and interaction of the IPC-HPMC blending on the drug release of GFFE using a freely water-soluble drug, metformin HCl, under different threshold concentration levels and curing effect. The interaction between the IPC and HPMC was characterized using vibrational spectroscopy and thermal analyses under curing and swelling conditions. Anti-solvent followed by lyophilization had better physicochemical and physicomechanic properties than spray dying technique. The interaction was observed by a specific shifting of the vibrational peaks and alteration of the thermal behavior pattern. These effects altered the drug release behavior. Thereafter, the IPC reduced burst release effects in the initial time and during testing, and the IPC improved the HPMC matrix robustness under mechanical stress testing below threshold concentration of HPMC matrix formulated in the GFFE.