Studies On Preparation And Properties Of Silk Fibroin Drug-loading Microspheres

A w/o/w double emulsion method was developed to prepare silk fibroin microspheres using silk fibroin (SF) as vehicle, dexamethasone sodium phosphate (DSP) as drug model. The surface shape was observed by SEM, the particle diameter's size and distribution were observed by Laster particle sizer. The structure was studied by X-ray, FTIR and DTA. The cytotoxicity was assessed by MTT assay. The properties of drug release was assessed by in vitro release method. The effect on the preparation of SF microspheres and properties were investigated by the ratio of emulsifier, the variety of organic solvent, the organic solvent :SF ratio, the concentration of SF, the DSP : SF ratio.The results showed that the microsperes approximatively spherical. The SF microspheres'average size was between 0.56～56.52μm, and the particle sizes decreased with the ratio of emulsifier increased, there was an obviously decrease when the ratio above 3%. The particle size of SF microspheres increased with the concentration of SF increased, especially above 6%. The particle size of SF microspheres decreased obviously when the organic solvent : SF ratio added from 1:1 to 2:1, but there was no obvious change above 2:1. The drug-loading microspheres'average size was between 6.53～66.27μm. The structure of pure silk fibroin was mainly amorphism. The structure of SF microspheres and drug-loading microspheres prepared by different organic solvent, different organic solvent :SF ratio, different concentration of SF had an obviously change compared to pure SF, the state of aggregation was mainly silkⅠand silkⅡand conformation wasβ-sheet. The cytotoxicity rank of SF microspheres prepared by the three different organic solvent were 0, this showed non-poisonous. The average drug-loading efficiency was between 2.31%～9.01% and the average encapsulation efficiency was between 31.28%～99.07%. Drug release of microspheres:the release rate was about 50% for 1h, there had a slow release effect when the DSP : SF ratio was between 1:20～1:40, the organic solvent : SF ratio was between 4: 1～6:1 and the concentration of SF was between 3%～6%, especially the DSP :SF ratio was between 1:20～1:40 and the organic solvent : SF ratio was 5: 1～6:1. After 4h had passed, the release rate obviously decreased, and the quantity of the released drug was about 85% of the total. The SF drug-loading microspheres prepared under other technologies had an obvious suddenly release.