Synthesis, Characterization, and Drug Delivery from pH- and Thermoresponsive Poly(N-Isopropylacrylamide)/Chitosan Core/Shell Nanocomposites Made by Semicontinuous Heterophase Polymerization

Temperature- and pH-responsive core/shell nanoparticles were prepared by semicontinuous heterophase polymerization of N-isopropylacrylamide (NIPA) in the presence of chitosan micelles for drug delivery purposes. Micelles of chitosan, formed in an acetic acid aqueous solution at 70°C containing potassium persulfate, were fed with N-isopropylacrylamide (NIPA) at a controlled rate, to produce PNIPA/chitosan core/shell nanoparticles of about 350źnm. Then, the crosslinking agent, glutaraldehyde, was added to crosslink the nanoparticles. These nanocomposites were temperature- and pH-responsive, which make them suitable as controlled drug releasing agents. The nanoparticles exhibit thermoreversibility to heating-and-cooling cycles and show different responses depending on the releasing mediumźs pH. Drug delivery tests were performed, employing as a model drug, doxycycline hyclate.