pH-responsive liposomes self-assembled from electrosprayed microparticles, and their drug release properties

In this work, composite Eudragit L100/phosphatidyl choline microparticles were fabricated through electrospraying. pH-responsive liposomes were found to self-assemble from these when the microparticles were added into aqueous media. The microparticles and the liposomes were both approximately spherical in shape according to electron microscopy, but the liposomes have much smaller diameters (200-300 nm) than the electrosprayed particles (1.6-1.7 mu m). The zeta potential of the liposomes is approximately -30 mV, which suggests the formation of stable suspensions. Varying the pH conditions used for self-assembly causes the liposomes to change their shape and structure, due to the influence of the Eudragit molecules. Microparticles comprising Eudragit, phosphatidyl choline and the model drug ketoprofen were also prepared. Upon their addition to water, ketoprofen was found to be loaded into the liposomes self-assembled from the particles with an entrapment efficiency of 75%. pH-dependent release was observed from the drug-loaded liposomes. At pH 4.5, only 58% of the drug loaded was released after 12 h, while 80% was released at pH 7.4. Overall, these results demonstrate that the pH-dependent liposomes developed have great potential for application as stimuli-responsive drug delivery systems.