Synthesis and characterization of amphiphilic block polymers with amino groups and their conjugates with folic acid and fluorescent probes

Amphiphilic amino-bearing biodegradable copolymers, [methoxy-poly(ethylene glycol)]-block-poly[(L-lactide)-co-(serinol carbonate)] (mPEG-block-P(LA-co-CA)), are prepared by synthesizing amino-bearing cyclic carbonate monomer N-benzoxycarbonylserinol carbonate (CAB) starting from serinol, by ring-opening polymerization of L-lactide and CAB using diethylzinc as catalyst and mPEG as macroinitiator, and by subsequent removal of the protective benzyloxycarbonyl groups by HBr treatment. After deprotection, the pendant amino groups on the carbonate units are reacted with N-hydroxylsuccinimide-activated folic acid (FA) to achieve mPEG-block-P(LA-co-CA/FA) conjugate and with fluorescein isothiocyanate (FITC) to achieve mPEG-block-P(LA-co-CA/FITC) conjugate. The structures of mPEG-block-P(LA-co-CAB), mPEG-block-P(LA-co-CA), mPEG-block-P(LA-co-CA/FA) and mPEG-block-P(LA-co-CA/FITC) are confirmed using H-1 NMR and Fourier transform infrared spectroscopy. The block copolymers can self-assemble into micelles in aqueous solution. Because of the functionality of FA and FITC, these copolymers can find important applications in drug delivery systems to serve as targeting moieties and fluorescent probes. (C) 2011 Society of Chemical Industry