【作者】 肖瑶；

【导师】 段金友；

【作者基本信息】 西北农林科技大学 ， 化学生物学， 2020， 硕士

【摘要】 细菌性肠炎是一种常见的感染性疾病,通常伴有恶心、便血和腹泻等症状,给人类健康带来了严峻的挑战。抗生素作为治疗细菌感染的主要临床手段,目前存在严重的耐药危机和毒副作用,因此急需开发一种新型高效的治疗策略来治疗细菌性肠炎。研究表明,肠道病原菌粘附到上皮细胞是其致病过程中的关键一步,若不发生,致病菌将会被宿主的免疫防御机制排出体内。益生菌可通过竞争抑制病原菌的粘附及定植从而有效改善肠道病原菌引起的菌群失调和炎症反应。然而,口服过程中遇到的生物学挑战（胃酸、高浓度胆盐等）极大地限制了其潜在的健康益处。在本研究中,我们选用鼠李糖乳杆菌为模型益生菌包封在还原响应型的水凝胶中,以一种新的思路治疗沙门氏菌诱导的细菌性肠炎。该水凝胶是巯基化透明质酸通过氧化自交联制备而成,当接触到周围肠道病原体分泌的H₂S后,水凝胶可局部降解并快速释放鼠李糖乳杆菌,进而与病原菌竞争肠道养分及结合位点,阻止其在肠道内的定植。首先应用核磁共振氢谱和高效凝胶色谱分别从定性及定量上证明了巯基化透明质酸的成功合成。通过流变学分析研究了水凝胶的机械性能,在聚合物浓度为4%（w/v）时其综合性能达到最佳。用扫描电镜对水凝胶递送体系的微观形貌进行了观察,结果表明,鼠李糖乳杆菌被均一的负载在水凝胶的三维网络结构中。胃肠道耐受实验表明,鼠李糖乳杆菌在包封后,面对胃肠道的侵蚀,其生存能力明显提高。同时,水凝胶的包封也能适当提高鼠李糖乳杆菌在常温及冷藏条件下的贮存稳定性。与游离的鼠李糖乳杆菌相比,包封的鼠李糖乳杆菌对沙门氏菌诱导的肠炎有更好的治疗效果,且兼具良好的生物相容性。综上所述,这种基于透明质酸的还原响应型水凝胶是一种很有前景的病原菌靶向递送系统,可有效提高益生菌的口服疗效。同时,益生菌疗法能在一定程度上缓解抗生素带来的负面效应,为细菌性肠炎的治疗提供了新的方案。更多还原

【Abstract】 Bacterial enteritis is one of the most common global health threats which usually accompanied by symptoms involving nausea,hematochezia and diarrhea.As the main clinical treatment for bacterial infections,current antimicrobial therapy suffers greatly from antibiotic-resistance crisis and toxic side effects in patients,emphasizing the urgent need for new approaches to mitigate bacterial enteritis.Attachment of pathogens on epithelial tissues has been recognized as the first step in infectious process,otherwise they will be expelled by the host’s physiological mechanical defense mechanisms.Probiotics were found to be effective in ameliorating the microbial dysbiosis and inflammation caused by intestinal pathogens.However,biological challenges（acidic conditions and bile salts）encountered during oral delivery have greatly limited their potential health benefits.Here,a model probiotic（Lactobacillus rhamnosus）was encapsulated in an intestinal-targeted hydrogel to alleviate bacterial enteritis.The hydrogel was prepared simply by self-crosslinking of thiolated hyaluronic acid.Upon exposure to H₂S which were excreted by surrounding intestinal pathogens,the hydrogel can locally degrade and rapidly release cargos to compete with source pathogens for binding to the host.The successful synthesis of HA-SH was verified by ¹HNMR and HPGPC respectively.The mechanical properties of hydrogel were studied by rheological analysis,and the ideal stability was achieved at a polymer concentration of 4%（w/v）.The morphology of the encapsulation system was further measured by SEM,exhibiting uniform payload of probiotics.Endurance experiments indicated that the encapsulation of Lactobacillus rhamnosus significantly enhanced their viability under gastrointestinal tract insults.Besides,the encapsulation technology can also improve shelf time of Lactobacillus rhamnosus when stored at refrigerated and ambient conditions.Compared with free cells,encapsulated Lactobacillus rhamnosus exerted better therapeutic effect against Salmonella-induced enteritis with negligible toxicity in vivo.In summary,this pathogen-targeted hydrogel could be a promising delivery system to effectively improve the oral efficacy of probiotics.Moreover,the probiotics therapy can alleviate the negative effects brought by antibiotics,which provides a new treatment for bacterial enteritis.更多还原