Development of a new poly(ethylene glycol)-graft-poly(D,L-lactic acid) as potential drug carriers

A new poly(ethylene glycol) (PEG)-modified poly(D,L-lactic acid) (PLA) was synthesized by grafting maleic anhydride onto PLA and subsequently amidating with O,O'-bis-(2-aminopropyl) polypropylene glycol-block-polyethylene oxide-block-polypropylene glycol (H2N-PEG-NH2, Mw: 600). Its structure was confirmed by FTIR, DSC, 1H NMR, GPC, and ninhydrin test. The polymer is more hydrophilic compared with PLA according to contact angle tests, and is degradable as determined from its pH and mass changes during degradation. The polymer shows a 62.7% decrease in BSA absorption compared with PLA when dried in air, and a 82.76% decrease when dried under 65% humidity, as measured by fluorospectrophotometry. The polymer promotes adhesion and proliferation of osteoblasts, determined by MTT assay. With this new polymer, spherical nanoscale aggregates encapsulated with or without hydrophilic dye are formed spontaneously in water, visualized by inverted microscope and AFM. The particle size is concentration dependent as confirmed by dynamic light scattering, and its critical micelle concentration was 1.124 microg/mL as determined by a fluorescence method. The good hydrophilicity, degradability, cellular compatibility, protein-resistance, self-aggregation, and reactivity of the polymer may lead to its potential applications in drug delivery.