Sugar-installed polymer micelles: Synthesis and micellization of poly(ethylene glycol)-poly(D,L-lactide) block copolymers having sugar groups at the PEG chain end

A poly(ethylene glycol)-poly(D,L-lactide) block copolymer (PEG-PLA) having a site specifically protected-sugar group at the PEG chain end was synthesi zed through a successive ring-opening polymerization of ethylene oxide and D,L-lactide using a metalated protected sugar as an initiator. Removal of p rotective groups from the sugar residue in the block copolymer was quantita tively carried out using 80% trinfluoroacetic acid at room temperature, yie lding a block copolymer having a glucose or galactose residue at the chain end in a regioselective manner. Polymer micelles having sugar residues on t he surface were then prepared by dialyzing an N,N-dimethylacetamide solutio n of the sugar-bearing PEG-PLA block copolymer against water. Dynamic light -scattering measurement of the polymer micelle solution revealed that the s caled characteristics line width had essentially no angular dependence, con sistent with the spherical geometry of the polymer micelle. The diameter an d polydispersity index of the polymer micelle, determined by a cumulant met hod, were approximately 40 nm and less than 0.1, respectively further, a ga lactose-bearing PEG-PLA micelle was confirmed to selectively attach to RCA- 1 lectin, which is known to recognize beta-D-galactose residues. These poly mer micelles having sugar groups regioselectively on their exterior are exp ected to have nide utility in the field of drug delivery as glyco-receptor- directed carrier systems.