| Xanthan gum is an extracellular heteropolysaccharide produced from fermentation of Xanthomonas campestris. The relative molecular weight (Mr) distribution ranges from 2×106 to 2×107. Xanthan gum has the properties of high stability, pseudoplastic rheology, thickening, emulsion and suspension stabilization, and safety. In medical field, xanthan gum is mainly used as pharmaceutic adjuvant. Because of its unique physical and chemical properties, xanthan gum has potential applications in many biological and pharmaceutical fields. At present, the production process of purified xanthan gum for injection was established, which was suitable for industrial scale, and the quality standard of xanthan gum for injection grade was also established. Studies had been carried out on xanthan gum intra-articular injection and its pharmacodynamics and action mechanism on experimental osteoarthritis in rabbits. According to the properties of xanthan gum, it can also be used in other fields. Mr, one of the most fundamental parameters in xanthan gum characterization, is a key industrial output control variable for many applications of end products. Xanthan gum of different M, displays different physical and chemical properties, which may determine its final applications. The high stability and viscoelasticity of xanthan gum are closely related to its Mr. Xanthan gum with higher Mr exhibits higher solution viscosity and better viscoelasticity. More efforts should be made on the production, development of high Mr xanthan gum, to further expand the application scope of xanthan gum in medical and pharmaceutical field. In the present study, we obtained xanthan gum with higher Mr by fermentation optimization; prepared xanthan gum of different Mr, established the Mr quantitative model of xanthan gum by near-infrared spectroscopy (NIRS) to achieve rapid analysis; evaluated the preventive effects of xanthan gum of different Mr on postoperative intra-abdominal adhesions in rats.1 Fermentation optimization of high Mr xanthan gumObjective To obtain high Mr xanthan gum by optimization of fermentation conditions and establish the fermentation process of high Mr xanthan gum. Methods Through shaking flask culture, the fermentation temperature and time, inoculum volume, carbon sources and nitrogen sources were optimized using solution viscosity of raw xanthan gum samples as screening index. Then, followed by fermentation in a 10 L tank, the final fermentation process was determined. At last, fermentation process in 50 L tank was investigated. The Mr of purified xanthan gum samples were analyzed by size exclusion chromatography combined with multi-angle laser light scattering (SEC-MALLS). To ensure the accuracy of the determination results of Mr, the dn/dc value of purified xanthan gum was determined. Results The optimal medium components and fermentation conditions were defined as:glucose 4%, soybean cake powder 0.3%, yeast extract 0.05%, citric acid 0.1%, MgSO4 0.01%, CaCO3 0.4%, inoculum volume 4%, temperature 28 ℃, time 72 h, pH 7.0. The fed-batch fermentation process was used. The initial concentration of glucose was 2%; the other 2% glucose was added at 42 h. The dn/dc value of pure xanthan gum in NaCl solution was 0.163. The Mr of xanthan gum produced with the optimized fermentation conditions was 6.91×106, which was 30.4% higher than that of the product obtained with fermentation process before optimization. Conclusion The industrialized fermentation process of high Mr xanthan gum was established and the high Mr xanthan gum was obtained.2 Establishment of the rapid determination method for the Mr of xanthan gum based on near-infrared spectroscopyObjective To establish a rapid M, determination method for xanthan gum quality control by NIRS coupled with partial least square (PLS) algorithm. Methods A group of xanthan gum powder samples with homogeneous Mr gradient were prepared by ultrasonic degradation. SEC-MALLS was used to measure the reference values of Mr. Through PLS method, the useful information of the near-infrared (NIR) spectra was extracted and a new orthogonal matrix was set to represent the raw spectral data. The new data set was related to the Mr, which was used to create the PLS model. All samples were divided into two sets by principal component analysis (PCA). Several combinations of pre-processing methods and the selected spectral regions were studied in order to construct the optimal calibration models. Two sample measurement modules, integrating sphere module and fiber-optic probe module, were compared. Results Although both modules could satisfy the needs of Mr determination, the best PLS regression model was based on fiber-optic probe module. Finally, fiber-optic probe was selected to acquire NIR spectra; multiplicative signal correction and mean centering was used as the best pre-processing method. Spectral regions including 4900-4000 cm-1,7100-5465 cm-1 and 8240-7345 cm-1 were finally selected. For this model, the values of coefficient of determination in calibration (R2C), coefficient of determination in prediction (R2p), residual predictive deviation (RPD) and root mean square error of prediction (RMSEP) were 0.967,0.975,6.028 and 0.250×106 Da, respectively. The method validation was based on the fiber-optic module. The Mr range, linearity, accuracy and precision of the established method were validated. In this study, the Mr range of the model was from 0.844×106-5.962×106. The R2 of the model was 0.969, demonstrating a good linearity of the model. There was no significant difference between the Mr values predicted by NIRS and the reference values. As the relative standard deviation from NIRS was below the normally accepted level of 5%, therefore the repeatability and intermediate precision of the NIR method was validated. The accuracy and precision of the NIR method was acceptable from a manufacturing perspective. Furthermore, influence factors on this method, including the samples used in NIR analysis, the sampling modules and the moisture content of the samples were discussed. The moisture content of the samples was considered to have significant influence on the method; therefore, an appropriate measurement protocol should be established to minimize the adverse effect. Conclusion A simple, rapid, non-destructive and practical method based on NIRS and PLS multivariate calibration for Mr determination of xanthan gum was developed. Results showed that the proposed NIR method may be suitable for practical applications in manufacturing plants and probably be accepted as a good alternative approach for fast determination of Mr of xanthan gum in production process.3 Experimental study on the preventive effects of xanthan gum on postoperative intra-abdominal adhesions in ratsObjective To evaluate the safety and preventive effects of xanthan gum on postoperative intra-abdominal adhesions in rats. Methods The rat peritoneal adhesion model was prepared. Consequently,1 mL of each solution, including 0.5%,1% and 2% (w/v) xanthan gum injection,1.2% medical sodium hyaluronate gel or normal saline, was individually applied to the defect side of each wound. On the 7th day after surgery, the animals were euthanized. The body weight, hematological and biochemical parameters were examined, the histopathological changes in heart, liver, kidney and injured tissues were observed, and the adhesion severity grade was evaluated. In order to evaluate the anti-adhesion effects of xanthan gum of different Mr, the 1% xanthan gum injection was prepared using pure xanthan gum of different Mr (Mr:6.91×106,4.75×106 and 2.51×106).1 mL of each solution, including 1% xanthan gum injection of different Mr,1.2% medical sodium hyaluronate gel or normal saline, was individually applied to the defect side of each wound. At 7 days after surgery, the animals were euthanized. The safety and anti-adhesion effects of xanthan gum was evaluated and the rheological properties of xanthan gum of different Mr were measured and compared. Results Compared to normal saline group, the body weight, hematological and biochemical parameters showed no significant change (P>0.05) in xanthan gum groups of different concentrations and Mr, and no obvious histopathological changes were detected in heart, liver and kidney. Compared to normal saline group, the incidence and severity of intra-abdominal adhesions of xanthan gum group were significantly lower (P<0.05). Xanthan gum with higher concentration or higher Mr exhibited better anti-adhesion effects. At low shear rate, the viscosity and overall stiffness of 1% high Mr xanthan gum was higher than that of 1.2% medical sodium hyaluronate gel. Conclusion When 1 mL of 0.5%-2% xanthan gum was intra-abdominally applied into rats for 7 days, there is no significant systemic and topical toxicity. The incidence and severity of intra-abdominal adhesions of the experimental adhesion model rats were significantly reduced when xanthan gum was applied. The anti-adhesion effect of 1% high Mr xanthan gum was significantly superior to that of 1.2% medical sodium hyaluronate gel (P<0.05). |
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