Study of biodegradation behavior of chitosan-xanthan microspheres in simulated physiological media

Microspheres of a polyelectrolyte complex hydrogel were prepared from chito san and xanthan after interaction between the two polyionic polymers. Their biodegradation was studied vs. chitosan. Simulated gastric fluid (SGF, pH 1.2) and intestinal fluid (SIF, pH 7.5) both as biodegradation media and ph osphate buffered saline (PBS, pH 7.4) as a negative control were used. The degradation studies were performed at 37 degrees C at 240 rpm permanent sti rring to mimic the physiologic conditions. High performance liquid chromato graphy (HPLC) was carried out to quantify the chitosan degradation products using glucosamine (GA) and N-acetyl-D-glucosamine (N-Ac-GA) as references. The peaks area integration method was used to determine the amount of each degradation product as a function of incubation time in the media. The eff ect of the media on the morphological structure of microspheres was assesse d by scanning electron microscopy. From HPLC studies, it appeared that in S GF and SIF the major degradation products were glucosamine (GA) and N-acety l-D-glucosamine (NAc-GA). In the first 15 days, oligochitosan fractions wer e released from the complex whereas N-acetyl-D-glucosamine was detected in the media after this period. The degradation kinetics were assessed by the measurement of the cumulative degradation products, which showed faster deg radation of chitosan than the complex in SGF and SIF. SEM micrographs showe d an enhancement of microsphere porosity as a function of incubation time i n the simulated physiological media. Our results suggest a better control o f the degradation kinetics when chitosan is complexed to xanthan. (C) 2000 John Wiley & Sons. Inc.