Sakloetsakun Duangkamon, Hombach Juliane M R, Bernkop-Schnürch Andreas
Department of Pharmaceutical Technology, Institute of Pharmacy, University of Innsbruck, Innrain 52, Josef Möller Haus, A-6020 Innsbruck, Austria.
Biomaterials. 2009 Oct;30(31):6151-7. doi: 10.1016/j.biomaterials.2009.07.060. Epub 2009 Aug 21.
The rheological behaviour of chitosan-thioglycolic acid conjugate (chitosan-TGA) in the presence of four oxidizing agents was investigated. Chitosan-TGA was synthesized via amide bond formation between the primary amino group of chitosan and the carboxylic acid group of thioglycolic acid. The sol-gel phase transition of the polymer was determined by rheological measurements. Moreover, cytotoxicity of the gel in combination with each oxidizing agent was evaluated utilizing LDH and MTT assay. The modified chitosan displayed 1053+/-44 micromol/g thiol groups. Results of rheological studies showed that 1% (m/v) chitosan-TGA without any oxidizing agents became gel within 40 min. In contrast, when the oxidizing agents hydrogen peroxide, sodium periodate, ammonium persulfate and sodium hypochlorite were added, respectively, gelation took place within a few minutes. Within 20 min, hydrogen peroxide having been added in a final concentration of 25.2 nmol/L increased dynamic viscosity of 1% (m/v) chitosan-TGA up to 16,500-fold. This can be explained by the formation of inter- and/or intramolecular disulfide bonds which were indirectly verified via the decrease in thiol groups. Additionally, evidence of an increase in cross-linking of thiolated chitosan as a function of time was provided by frequency sweep measurements. Furthermore, viability of Caco-2 cells having been incubated with chitosan-TGA/oxidizing agent systems assessed by MTT assay was 70-85% and the percentage of LDH release was only in case of the chitosan-TGA/ammonium persulfate system significantly (p<0.05) raising compared to the negative control. According to these results, chitosan-TGA/oxidizing agent combinations might be a promising novel in situ gelling system for various pharmaceutical applications such as a controlled drug release carrier or for tissue engineering.
研究了壳聚糖-巯基乙酸共轭物（壳聚糖-TGA）在四种氧化剂存在下的流变行为。壳聚糖-TGA是通过壳聚糖的伯氨基与巯基乙酸的羧基之间形成酰胺键合成的。通过流变学测量确定了聚合物的溶胶-凝胶相变。此外，利用乳酸脱氢酶（LDH）和噻唑蓝（MTT）测定法评估了凝胶与每种氧化剂组合的细胞毒性。改性壳聚糖显示出1053±44微摩尔/克的巯基。流变学研究结果表明，不含任何氧化剂的1%（质量/体积）壳聚糖-TGA在40分钟内变成凝胶。相反，当分别加入过氧化氢、高碘酸钠、过硫酸铵和次氯酸钠等氧化剂时，凝胶化在几分钟内发生。在20分钟内，以25.2纳摩尔/升的终浓度加入过氧化氢，使1%（质量/体积）壳聚糖-TGA的动态粘度增加到16500倍。这可以通过分子间和/或分子内二硫键的形成来解释，二硫键的形成通过巯基的减少间接得到证实。此外，频率扫描测量提供了硫醇化壳聚糖交联随时间增加的证据。此外，通过MTT测定法评估，与壳聚糖-TGA/氧化剂系统孵育后的Caco-2细胞活力为70-85%，只有壳聚糖-TGA/过硫酸铵系统的乳酸脱氢酶释放百分比与阴性对照相比显著升高（p<0.05）。根据这些结果，壳聚糖-TGA/氧化剂组合可能是一种有前途的新型原位凝胶系统，可用于各种药物应用，如控释药物载体或组织工程。
