Conjugation of bioactive ligands to PEG-grafted chitosan at the distal end of PEG

Graft copolymers of chitosan and PEG-CO2H incorporating biologically active molecules and tags (mannose, cholesterol, a coumarin dye, and biotin) at the distal end of poly(ethylene glycol) (PEG) have been synthesized in excellent yields and nearly quantitative mass recoveries. Experimental conditions allowing the preparation of multifunctional graft copolymers incorporating simultaneously several of those active molecules and tags in controlled ratios are also presented. The required functionalized PEG-CO2H conjugates have been prepared from a heterodifunctional PEG and the experimental conditions established to ensure the purity of PEG end groups (H-1 and C-13 NMR and matrix-assisted laser desorption/ionization mass spectrometry-time of flight (MALDI-TOF)) and the completion of each synthetic step.