Design of polymeric microparticles for pH-responsive and time-sustained drug release

Abstract

We described the design of uniform microencapsulates with almost 100% encapsulation efficiency, synthesized without organic solvents, via microfluidic spray drying of water-based dispersions of pH-responsive methacrylic acid polymers (Eudragit® L 30D-55). The effects of incorporating water-based network-forming materials in the formulations on pH-responsiveness and controlled release patterns of enteric microparticles were observed. Acid hydrolysed tetraethoxysilane (TEOS) was used to form an interpenetrating, rigid framework of silica, whereas Eudragit® NE (a copolymer based on ethyl acrylate and methyl methacrylate) was added to produce a more flexible polymeric network. The spray-dried microparticles generally displayed crumbled or buckled morphologies dependent on drying temperatures, due to large hydrodynamic sizes of solutes in feed dispersions. The drug release kinetics of microparticles were sensitive to the type and the added amount of network-forming materials, due to different colloidal interactions between Eudragit® L and either silica or the copolymer. This study demonstrated a strategy to design enteric microparticles with different microstructural properties and drug release behaviours through understanding of colloidal interactions between constituents of matrix materials.