Dual stimuli responsive poly(N-isopropylacrylamide) coated chitosan scaffolds for controlled release prepared from a non residue technology

The first decade of the 21st century saw an increasing interest in the development of devices and biomaterials for delivery of bioactive substances that can be controlled by external stimuli. Herein we report the production of smart partially biodegradable scaffolds that exhibit pH- and temperature-responsive behavior and their effects on the release of a model protein and a drug of low molecular weight. Chitosan (CHT) scaffolds (pH sensitive) were coated/impregnated with a thermoresponsive polymer, poly(N-isopropylacrylamide) (PNIPAAm), by in situ synthesis of PNIPAAm within CHT micropores. Microarchitectural analysis by scanning electron microscopy and mercury intrusion porosimetry demonstrate that the coating of the pores inner structure could be efficiently achieved without a considerable loss of porosity of native CHT-scaffolds. Two different strategies were used to impregnate the polymeric devices: supercritical fluid impregnation for scaffold uptake with a model low molecular weight drug (ibuprofen) and bulk loading to impregnate a model protein (bovine serum albumin, BSA). The release profiles showed a specific pattern according to pH and temperature. PNIPAAm temperature responsiveness is able to control BSA release but ibuprofen (Ibu) release is only mediated by pH environmental conditions.