PLGA degrades by hydrolysis of its ester linkages in agueous environments. In detail, four steps can be described during its degradation 1.Hydration: water penetrates into the amorphous region and disrupts bonds, causing a decrease in the glass transition temperature(Tg) 2. Initial degradation: cleavage of covalent bonds, with a decrease in the molecular weight. 3.Constant autocatalyze the degradation process, and mass loss begins by massive cleavage of the backbone covalent bonds,resulting in loss of integrity. Solubilization: the fragments molecules that soluble in the aqueous environment