(217eu) Preparation of Chitosan Microspheres and Their Release Properties

Microencapsulation technique is an effective and long-lasting method for release of encapsulated drugs and has drawn increasing attention due to its potential applications in the fields of food and drug delivery systems, and so on. Biodegradable microspheres used as controlled release systems are important in pharmaceutics. Chitosan is a natural polysaccharide, comprising of glucosamine and N-acetylglucosamine and can be derived by partial deacetylation of chitin. Due to its major attributes, which include biodegradable, nontoxic and biocompatibility properties, chitosan has been widely used in the pharmaceutical industry. And chitosan microspheres have been investigated before in different drug delivery applications. Efforts should be still made to develop safe and facile approaches to fabrication of controlled release microspheres of natural biopolymers.

Therefore, in this study,  a kind of controlled release drug-loaded chitosan microspheres were prepared by an ultrasonic emulsion cross-linking method using glutaraldehyde as cross-linking agent and norfloxacin as model drug. The microspheres were characterized by Fourier transform infrared (FT-IR) before and after the cross-linking reaction. Laser particle size analyzer was used to obtain the the particle size. Ultraviolet specrophotometer was used to obtain the drug content of the microsphere. To obtain the optimum conditions, some factors, which influence the diameter and drug-loading rate of microspheres such as mechanical stirring time, adding volume of glutaraldehyde solution, ultrasonic emulsification time, water-oil volume ratio, concentration of chitosan and the amount of drugs (drug to chitosan), were changed. The results show that when mechanical stirring is 50min, the volume of glutaraldehyde solution is 2ml, ultrasonic emulsification time is 4min, water-oil phase volume ratio is1:8, the concentration of chitosan solution is 1% and the drug to chitosan weight ratio is 1:4 can obtain the best microspheres. 

The release behaviour of norfloxacin from chitosan microspheres in PBS solutions at pH 7.4 of different time intervals was monitored. From the release curve we can see that a burst release behavior was recorded at the initial stage (within 2h). After that, the norfloxacin loaded microspheres exhibited continuous slow release profiles for at lease 50h.