Poly(lactic-co-glycolic acid) and functional hydrogels for drug delivery applications

Biodegradable polyesters like poly(lactide-coglycolide acid) (PLGA) and pH-sensitive hydrogels have been used increasingly for various medical and biological applications. The present work focused on the use of these functional polymers to design an assembled drug delivery system (DDS) that could integrate multiple functions in a single device and achieve different release patterns. For PLGA, The major concerns are the poor hydrophilicity, accumulated acidity during degradation, and bulk erosion characteristics. In this study, poly(ethylene oxide)/poly(propylene oxide)/poly(ethylene oxide) (PEO-PPO-PEO) tri-block copolymer and a nano-clay Cloisite® 30B were utilized as modifiers to control the degradation behavior and hydrophilicity of PLGA. For comparison, a block copolymer, poly(lactic acid)/ poly(ethylene glycol) (PLA-co-PEG) was synthesized. A pH-sensitive hydrogel together with a poly(hydroxyethyl methacrylate) (HEMA) was used as a gate to control drug release. By using this bilayered self-folding design, the drug protection and self-regulated oscillatory release were demonstrated.