[Preparation of uniform-sized chitosan microspheres and application as carriers for protein drugs].

Chitosan microsphere has been wildly researched in controlled release of protein and peptide drug because of its excellent mucoadhesive and permeation enhancing effect across the biological surfaces. The control of the size and size distribution of microspheres is necessary in order to improve reproducibility, bioavailability, and repeatable release behavior. In this work, uniform-sized chitosan microspheres containing insulin were prepared by a novel membrane emulsification technique combined with glutaraldehyde crosslinking method. In order to prepare uniform-sized chitosn microspheres, it is necessary to modify hydrophilic membrane into hydrophobicity. It is found that there exists a linear relationship between the size of chitosan microspheres and pore size of the membrane used, so it is easy to control the size of microspheres by using membranes with different pore size. In this study, the effect of different amount of crosslinker and crosslinking time on microspheres' morphology, encapsulation efficiency (EE) and release profile of drug in vitro were investigated. It is shown that the morphology of microspheres is more smooth and spherical, and the release rate is slower with the increase of amount of glutaraldehyde and prolongation of crosslinking time. When the molar ratio of amino group of chitosan to aldehyde group of glutaraldehyde is 1:0.7, and crosslinking time is 1 h, the highest EE was obtained (about 65%). Date obtained suggest that chitosan microspheres prepared by this new method would be a promising system for controlled release of protein drugs.