光敏剂-壳聚糖纳米粒复合体的构建及对龋坏影响牙本质生物改性的作用研究

Caries-affected dentin (CAD) is the structural foundation for the restoration of carious lesions. However, due to its structural characteristics, such as low collagen crosslinking degree and the deposition of acid-resistant minerals, CAD is also the area the most susceptible to secondary caries after restoration, severely influencing the clinical effect of caries management. Biomodification of CAD by the stabilization of collagen in its matrix can overcome the adverse impact of its structural abnormality. It will lay foundation for the prevention, replacement and regenerative restoration of dental caries, and is hopeful to solve the critical problem restricting the clinical effects of caries management. Our previous research demonstrated that demineralized dentin collagen can be stabilized by natural crosslinkers, while the crosslinking method still needs to be optimized. Literatures showed that photodynamic therapy can provide collagen crosslinking effect. This brings us a new idea to stabilize CAD collagen. Photodynamic therapy has more advantages than natural crosslinkers when applying to the CAD, since its crosslinking effect act rapidly, and it has remarkable antibacterial effect. Chitosan nanoparticles can be used as carriers for photosensitizers, enhancing the photodynamic effects. The present project was aimed to prepare photosensitizer-chitosan nanoparticles complex by grafting, encapsulating or mixing the photosensitizers into our successfully prepared chitosan nanoparticles; screen out optimum preparation method by the evaluation of photodynamic effect; clarify the mechanisms of photodynamic biomodification on CAD by the assessment of denuded collagen, residual bacteria, and dentin; and finally investigate the impact of photodynamic crosslinking and antibacterial effect on the improvement of CAD bonding durability, inhibition of secondary caries and advancement of the dentin remineralization potential. This project will provide new strategy for improving the clinical effect of caries management.

龋坏影响牙本质(CAD)是龋损修复的结构基础，但因胶原交联度低、抗酸物沉积等结构特点，是治疗后继发龋最易发生的部位，严重影响龋病临床疗效。通过稳定CAD胶原实现其生物改性，克服CAD异常结构的不利影响，将为龋病预防、替代性乃至再生性治疗奠定基础，并有望解决制约龋病临床疗效的关键问题。我们前期研究证实，天然交联剂可稳定脱矿牙本质胶原，但仍需改良交联方法。光动力疗法交联作用显著，为稳定CAD胶原提供了新途径，由于作用快速且抗菌疗效优异，用于CAD优势更大。本项目拟应用能增强光动力效应的壳聚糖纳米粒作为光敏剂载体（前期已成功制备），利用接枝共聚、包封或共混法构建光敏剂-壳聚糖纳米粒复合体，根据光动力效应筛选构建方法，从胶原、细菌、牙本质三层面揭示其对CAD生物改性的机制，探究光动力交联、抗菌联合作用影响CAD-修复材料界面稳定性、继发龋发生、牙本质再矿化潜能的规律，为提高龋病临床疗效提供新思路。

本课题针对龋坏影响牙本质的结构特殊性，龋损修复后牙本质粘接界面胶原稳定性差，粘接耐久性远低于健康牙本质的临床问题，基于光动力疗法交联作用快速，抗菌疗效优异的优势，深入探索了稳定龋坏影响牙本质胶原的有效途径。主要成果如下：（1）成功构建了玫瑰红-壳聚糖纳米粒复合体和核黄素-壳聚糖纳米粒复合体，证实两种光敏剂-壳聚糖纳米粒复合体均形态圆整、均一、稳定，都具有良好的生物相容性。（2）两种复合体经牙科LED光固化灯照射后的单线态氧释放产率均高于相应光敏剂，提示具有良好的光氧化能力。抗菌实验证实，两种复合体光照后对口腔常见致龋菌的抗菌作用均明显强于无光照组及空白壳聚糖纳米粒，且暗毒性与空白壳聚糖纳米粒基本一致。（3）探索了光敏剂-壳聚糖纳米粒复合体生物改性龋坏牙本质的作用机制，证实两种复合体均能有效清除残留细菌、提高胶原交联度，稳定裸露胶原，增强牙本质耐基质金属蛋白酶降解的能力。筛选得到两种复合体适宜的光处理时间均为90s，应用浓度为2%的玫瑰红-壳聚糖纳米粒复合体对龋坏影响牙本质的生物改性作用更佳。（4）证实了经复合体光处理的龋坏影响牙本质，粘接并老化后的粘接强度下降程度明显慢于未经复合体光处理组，其混合层质量也优于阴性对照组。说明光敏剂-壳聚糖纳米粒复合体生物改性龋坏影响牙本质可在一定程度上延缓龋病的进程。本项目的研究为提高龋病临床疗效提供了新的思路，为光动力作用在口腔医学其他领域中的应用提供了借鉴。