Fabrication and in vitro drug release of drug‐loaded star oligo/poly( DL ‐lactide) microspheres made by novel ultrasonic‐dispersion method

Cholic acid functionalized star oligo/poly(DL-lactide)s with different molecular weights were synthesized through the ring-opening polymerization of DL-lactide initiated by cholic acid. On the basis of the specific physicochemical properties of the star oligo/poly(DL-lactide)s, submicron sized drug-delivery systems were fabricated using a very convenient "ultrasonic dispersion method," which did not involve toxic organic solvents. The drug-loaded microspheres had a regular spherical shape with a narrow size distribution. The effects of ultrasonic power and the molecular weight of polymers on the microsphere fabrication were investigated. The in vitro drug release was studied. The release profiles were fitted by the classical empirical exponential expression. The fitting result indicated that the drug release was controlled by combined degradation and diffusion mechanism.