Synthesis and characterization of microparticles made of carboxymethyloxysuccinic-acid-modified PLA-PEG co-polymer.

A novel tri-block co-polymer, HO2C-PLA-PEG-PLA-CO2H (co-polymer II), with polybasic carboxylic acids as the end-groups was synthesized and characterized by IR and 1H-NMR. Based on the successful synthesis of co-polymer II, water-soluble sodium salicylate and oil-soluble tetrandrine, used as model drugs, were loaded in the co-polymer microparticles prepared through a modified multiple emulsion method. The encapsulation efficiency and drug-releasing behaviour were also investigated. It is found that the microparticles of about 10 μm in size are porous and can be produced from co-polymer II in better encapsulation efficiency (up to 86.65% and 55.94%) compared to those made from PLA/PEG/PLA (co-polymer I) (77.50% and 44.01%). The drug-release behaviour of co-polymer II exhibits an extended continuous release behaviour and the initial burst was reduced obviously. The results show that such functionalised PLA/PEG/PLA carrier provides higher drug encapsulation efficiency and better profiles.