Preparation, Characterization, and Self-Assembled Properties of Biodegradable Chitosan−Poly(l-lactide) Hybrid Amphiphiles

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Abstract
Biodegradable chitosan-graft-poly(L-lactide) (CS-g-PLLA) hybrid amphiphiles were prepared through direct grafting of a PLLA precursor to the backbone of CS. The average number of PLLA grafts per CS could be adjusted by the feed ratio of PLLA to CS, and it varied from 1.3 to 16.8. Moreover, both the crystallization rate and degree of crystallization of PLLA grafts with these graft copolymers could be adjusted by the chain length of PLLA and the number of PLLA grafts per CS, respectively. Meanwhile, CS-g-PLLA exhibited good solubility in some nonpolar and polar organic solvents compared with the original CS. Furthermore, self-assembled nanoparticles could be generated by direct injection of these graft copolymer solutions into distilled water, and their critical aggregation concentration decreased with increasing number of PLLA grafts per CS. The average size of the nanoparticles (25-103 nm) could be adjusted through the graft copolymer composition and the graft copolymer concentration, which was very different from the observations in ordinary PLLA-b-poly(ethylene oxide) amphiphiles. Significantly, this will provide a convenient method not only to combine the bioactive functions of CS with the good mechanical properties of biodegradable polymers, but also to generate nanoparticles with adjustable sizes for targeted drug release.