Shell-cross-linked amino acid-modified APLA-b-PEG-Cys copolymer micelle as a drug delivery carrier

Cysteine modified amphiphilic block copolymer acetate-polylactide-block-poly(ethylene glycol)-Cysteine (APLA-b-PEG-Cys) was synthesized and characterized. The polymer could self-assemble to form micelles with nano-size and regularly spherical in shape in aqueous solution. Folic acid (FA) was then used as a model drug to incorporate into APLA-b-PEG-Cys micelles. To enhance the stabilization of APLA-b-PEG-Cys micelle and control the drug release, the shell of APLA-b-PEG-Cys micelle was cross-linked by the in situ polycondensation of amino acid moieties on its surface. The effects of shell-cross-linking on the micelle physical chemistry properties were investigated in detail. It was found that, after cross-linking, the CMC of the APLA-b-PEG-Cys micelle was decreased, indicating that the shell-cross-linked micelle is more stable as compared to the uncross-linked one. In addition, the shell-cross-linking also changed the surface potential, micelle size and model drug (FA) release behaviour, but it did not significantly affect the micelle morphology and drug encapsulation efficiency of APLA-b-PEG-Cys micelles.