Preparation of chitosan-g-polylactide graft copolymers via self-catalysis of phthaloylchitosan and their complexation with DNA

The graft copolymer of chitosan-g-polylactide (CS-g-PLA) was synthesized successfully through ring-opening polymerization of lactide onto phthaloyl-protected chitosan by a self-catalysis strategy. After graft copolymerization, the phthaloyl groups were deprotected to regenerate free amino groups in the CS-g-PLA. FT-IR and NMR were used to characterize the graft copolymers both before and after the deprotection. We observed that degradation of the grafted PLA chains occurred in the alkaline deprotection process, and this process was optimized. Moreover, the CS-g-PLA containing the amino-polysaccharide backbone was formed into a polyelectrolyte complex with DNA. The resultant CS-g-PLA/DNA complexes were determined to be about 60 nm, with a positive charge above an N/P of 4/1.