Release of protein from poly/chitosan dual microspheres

Three kinds of poly(lactide-co-glycolide)/chitosan microspheres (abbreviated as PLGA/chitosan microspheres) were prepared with multiple emulsion technique. PLGA microspheres were prepared with the double emulsion method (W/O/W) based on PLGA as the matrix and bovine serum albumin (BSA) as the model protein. The PLGA microspheres were re-emulsified with chitosan solution containing BSA followed by cross-linking with sodium tripolyphosphate (TPP). Three kinds of PLGA were used as the raw material of PLGA microspheres in order to modulate the release kinetics of the model protein. The microstructure, the size distribution and the physical chemical properties of the PLGA/chitosan microspheres were analyzed by scanning electron microscope (SEM), laser scattering particle analyzer and fourier transform infrared (FTIR), respectively. The release of BSA from PLGA/chitosan microspheres was monitored in PBS and compared with PLGA microspheres. Simultaneously, the pH changes of the PBS were measured during the incubation. The results show that PLGA/chitosan microspheres demonstrate a multinuclear and dual microsphere structure. The drug-loading rate and the mean size of the PLGA/chitosan microspheres were 6%~8% and 40~60 μm, respectively. The PLGA/chitosan microspheres have excellent release curves with a less burst release and a longer than 75 days release. The degradation of PLGA/chitosan microspheres does not induce acidic environment as indicated by a pH value of 7~8 throughout the degradation. The PLGA/chitosan microspheres are excellent vehicles suitable for the proteins.