Formation and degradation of biodegradable triple-layered microparticles.

In this work, we report how biodegradable triple-layered microparticles can be fabricated through a simple, reliable, and economical one-step solvent evaporation technique. Characterization of triple-layered PLGA (shell)/PLLA (middle layer)/EVA (core) microparticles was conducted and their formation mechanism was described. Subsequently, in vitro hydrolytic degradation of these microparticles was investigated. It was found that the PLGA shell degraded rapidly leaving behind double-walled microparticles of PLLA/EVA after 40 days. The middle PLLA layer degraded more rapidly than expected because of the migration of PLGA oligomers that created a hydrophilic and acidic microenvironment in the PLLA layer. These degradation results therefore provide important insights into how triple-layered microparticles degrade, and how their degradation characteristics affect the drug releasing properties of these novel microparticles.