Hydrogel encapsulated biofilm inhibitors for dental caries prevention and treatment

变形链球菌作为龋病的主要致病菌， 多种机制来定殖牙齿表面并成为牙齿生物膜的组成部分。下 在不健康的条件下，致病菌，即产酸菌和耐酸菌，开始在口腔中占主导地位， 而有益生物如血链球菌和链球菌的数量 Gordonii显著降低。生物膜然后发酵的饮食碳水化合物生产酸性副产品 例如乳酸，其导致口腔pH降低，从而导致牙齿脱矿。通常 唾液系统采用缓冲系统来维持口腔中6.0-7.5的健康pH。pH值下降 低于5.5对口腔中的硬组织（牙釉质和牙本质）和软组织有潜在的危害。所以我们 假设不影响口腔粘膜细菌活力的生物膜抑制剂被递送到 以pH响应（当pH下降到5.5以下时释放）方式的口腔将是一种理想的方法， 预防/治疗龋齿。我们实验室的初步研究已经确定了这种特定的低微摩尔 不影响口腔黏膜生长的小分子生物膜抑制剂。我们确定 这些化合物通过抑制S.变形菌毒力因子，葡糖基转移酶。 从这些研究中鉴定的两种活性化合物SN 204和SN 199一致显示出剂量依赖性 抑制生物膜，IC 50值分别为16.7 μM和15 μM。此外，这些化合物 不抑制S. mutans和另外两种嗜盐菌（S. sanguinis和S. gordonii）up 至200 µM，这比它们的生物膜IC 50值高得多。对S. 在用SN 204或SN 199的致菌大鼠中，变形杆菌（UA 159）感染的龋齿导致相当大的 与对照组相比，颊面、龈沟和近端龋齿评分降低。鉴于唾液 pH值小于5.5可能对牙釉质有害，我们的目标是将我们的铅生物膜抑制剂封装在 聚甲基丙烯酸（PMAA）水凝胶纳米粒网络具有pH敏感性， 这种水凝胶包封的生物膜抑制剂（HEBI）对生物膜形成和龋齿的影响 发展在初步研究中，SN 199已成功地包封到具有微胶囊化的水凝胶中。 载量为1.72×10 ~（-5）ng/粒。作为原理的证明，我们已经证明了pH依赖性 小分子抗癌药物阿霉素从PMAA水凝胶中的药物释放， 报告的研究。本提案的总体目标是证明HEBI在以下情况下的生物膜抑制活性： 体外和体内，并建立其作为一种新的和选择性的生物材料，可用于 预防和治疗龋齿。该项目的长期目标是开发这些HEBI， 可以随时使用的牙条/乳霜，特别是在晚上睡觉时， 在口腔中按需释放生物膜抑制剂以预防/治疗龋齿。

As the primary etiological agent for the dental caries development, Streptococcus mutans has developed multiple mechanisms to colonize the tooth surface and become an integral part of the dental biofilm. Under unhealthy conditions, pathogenic bacteria, namely acidogenic and aciduric species, begin to dominate the oral population while the number of beneficial organisms such as Streptococcus sanguinis and Streptococcus gordonii decrease significantly. Biofilm then ferments the dietary carbohydrates producing acid byproducts such as lactic acid which causes a decrease on oral pH leading to the demineralization of tooth. Normally, the salivary system employs buffer systems to maintain a healthy pH of 6.0–7.5 in the oral cavity. A drop in the pH below 5.5 is potentially harmful to the hard (enamel and dentin) and soft tissues in oral cavity. Therefore, we hypothesize that a biofilm inhibitor that does not affect the viability of oral commensal bacteria delivered in to oral cavity in a pH responsive (released when the pH drops below 5.5) manner will be an ideal approach to prevent/treat dental caries. Preliminary studies from our labs have identified such specific low micromolar small-molecule biofilm inhibitors that do not affect the growth of oral commensals. We have established that these compounds produce their biofilm inhibition by inhibiting S. mutans virulence factor, glucosyl transferases. Two active compounds identified from these studies, SN204 and SN199 consistently showed dose dependent inhibition of biofilms with IC50 values of 16.7 µM and 15 µM, respectively. Furthermore these compounds did not inhibit the viability of S. mutans and of the other two commensal species (S. sanguinis and S. gordonii) up to 200 µM, which is a much higher concentration than their biofilm IC50 values. A 43 day treatment of S. mutans (UA159) infected dental caries in gnotobiotic rats with SN204 or SN199 have resulted in considerable reduction in buccal, sulcal and proximal caries scores compared to the control groups. Given that the salivary pH less than 5.5 is potentially harmful to the enamel, we aim to encapsulate our lead biofilm inhibitors within the network of poly(methacrylic acid) (PMAA) hydrogel nanoparticles which possess pH sensitivity and explore the effect of such hydrogel encapsulated biofilm inhibitors (HEBIs) on biofilm formation and caries development. In the preliminary studies, SN199 has been successfully encapsulated into hydrogel with a loading capacity of 1.72×10-5 ng per particle. As proof of principle, we have demonstrated the pH dependent drug release of the small-molecule anticancer drug, doxorubicin from PMAA hydrogel in the previously reported studies. The overall goal of this proposal is to demonstrate the biofilm inhibitory activity of HEBIs in vitro & in vivo and establish its potential as a novel and selective biomaterial that can be used for the prevention and treatment of dental caries. The long term goal of this project is to develop these HEBIs as dental strips/creams that can be used any time, especially at night when sleeping in order to provide a steady, on-demand release of biofilm inhibitors in the oral cavity to prevent/treat dental caries.