Preparation and characterization of thermosensitive and biodegradable PNDH-g-PLLA nanoparticles for drug delivery

A series of thermosensitive and biodegradable graft copolymers (PNDH-g-PLLA) were synthesized by the radical copolymerization of N-isopropylacrylamide, N,N-dimethylacrylamide and N-(hydroxymethyl)acrylamide, followed by the ring-opening polymerization of L-lactide. The molecular weight and chemical structure of these copolymers were determined by gel permeation chromatography (GPC), nuclear magnetic resonance (1H NMR) and Fourier transform infrared spectra (FT-IR). The resulting copolymers were temperature-sensitive and the lower critical solution temperature (LCST) was affected by their compositions. The graft copolymers obtained in this study exhibited low critical micelle formation concentration (CMC) values that were affected by the content of PLLA. Spherical nanoparticles with degradable cores were prepared from aqueous solutions of the amphiphilic graft polymers by a dialysis method. Dynamic light scattering (DLS) results indicated that the particle size increased with increase of PLLA content in the copolymer. The morphologies of prepared nanoparticles were observed by transmission electron microscopy (TEM). The prepared PNDH-g-PLLA nanoparticles with thermosensitive and biodegradable properties may have practical application in drug delivery and controlled drug release.