One-pot synthesis of poly(N-isopropylacrylamide)/chitosan composite microspheres via microemulsion

This work presents a new approach for the synthesis of multiresponsive composite microspheres of PNIPAM/chitosan. The resulting microspheres in a sandwich structure with PNIPAM nanoparticles embedded in the crosslinked chitosan matrix were characterized. Compared to other preparation methods, this proposed technique not only is a facile route but also endows the microspheres a desirable structure. The products undergo a temperature induced volume phase transition and exhibit an appreciable pH response. They are further tested as drug carriers to investigate potential application. The encapsulation efficiency in acidic environment (pH=4.0) is 73.5% and much higher than that in neutral (20.3%, pH=6.9) and alkaline (15.1%, pH=9.2) environments. The release of the drug from the microspheres can be controlled by pH and temperature.