One-step fabrication of triple-layered polymeric microparticles with layer localization of drugs as a novel drug-delivery system.

Particulate systems have tremendous potential to achieve controlled release and targeted delivery of drugs. However, conventional single-layered particles have several inherent limitations, including initial burst release, the inability to provide zero-order release, and a lack of time-delayed or pulsatile release of therapeutic agents. Multilayered particles have the potential to overcome these disadvantages. Herein, it is shown how triple-layered polymeric microparticles can be fabricated through a simple, economical, reliable, and versatile one-step solvent evaporation technique. Particle morphologies and layer configurations are determined by scanning electron microscopy, polymer dissolution tests, and Raman mapping. Key fabrication parameters that affect the formation of triple-layered polymeric microparticles comprising poly(DL-lactide-co-glycolide) (50:50), poly(L-lactide), and poly(ethylene-co-vinyl acetate) (40 wt% vinyl acetate) are discussed, along with their formation mechanisms. Layer thickness and the configurations of these microparticles are altered by changing the polymer mass ratios. Finally, it is shown that drugs can be localized in specific layers of the microparticles. This fabrication process can therefore be used to tailor microparticle designs, thus allowing such "designer" particulate drug-delivery systems to function across a wide range of applications.