Synthesis and characterization of poly(L-lysine)-g-poly(D,L-lactic-co-glycolic acid) biodegradable micelles

A series of amphipathic graft copolymers composed of poly(L-lysine) (PLL) as the cationic polymer backbone and biodegradable poly(D,L-lactic-co-glycolic acid) (PLGA) as the grafting chains were synthesized and characterized. The terminal group of PLGA was activated and chemically conjugated to the primary epsilon-amine groups of PLL to produce PLL-g-PLGA copolymers. PLL-g-PLGA formed a self-assembling micelle structure in aqueous solution. The micelle size ranged from 69.4 to 149.6 nm in diameter, depending on the grafting percentage of PLGA. Upon increasing the number of PLGA chains grafted onto the PLL backbone, the size of the micelles gradually decreased, at the same time lowering their critical micelle concentration. The micelles were individually separated and had a spherical geometry, as observed by atomic force microscopy (AFM). These PLL-g-PLGA copolymers can be applied as cell adhesive surface coating materials for biodegradable tissue engineering scaffolds and can be used as non-viral DNA carriers for gene therapy.