新型手性石墨烯量子点的设计合成及选择性抗菌应用研究

Bacterial infection is one of the most serious health threats. It is already quite difficult to apply conventional antibiotic for curing infection caused by resistant bacteria. Therefore, there is a pressing need to develop novel antibacterial medicine to combat against drug-resistant bacterial infection. A variety of nanomaterials bring new opportunity to the treatment of drug resistance bacterial. But the lack of selectivity, poor biosafety and insufficient stability of the reported nanomaterials arouse further concerns. The project intends to combine the chiral amino acid that can selectively interact with the Mur ligase, the high stereo-selective enzyme for peptidoglycan synthesis during the formation of cell wall, and the graphene quantum dot which provides advantages such as good biosafety, unique optical properties, and excellent stability in physical conditions to design new selective antibacterial agents with high antibacterial efficacy and low side effect on human health. Functionalizing GQD with the chiral D-amino acid which is the substrate of Mur ligase could trigger the specific binding of GQD and Mur ligase due to the stereo adaptation. And the π-π interaction between GQD and aromatic amino acid residues in protein can enhance the binding of GQD and the target protein to inhibit its activity and disrupt the synthesis of peptidoglycan, resulting in serious damage of cell wall and then the mortality of bacteria. With the aid of the theory calculation, we propose to design and direct the synthesis of chiral GQD that shows strong binding ability with the target protein. In combination with the experimental study of antibacterial activity and cellular toxicity of chiral GQD, we could explore the molecular mechanism of the selective anti-bacterial action and further optimize the properties of the nanomaterials. Through the process of “material design and synthesis – structure & property analysis - antibacterial test - feedback optimization”, the project can provide new insights for the development of Nano-antibacterial agents with high selective toxicity towards bacteria over mammalian cells.

细菌感染严重威胁着人类健康，传统抗生素已很难治愈由耐药性细菌所引起的感染，因此研发能够有效应对耐药菌感染的新型抗菌药物迫在眉睫。种类繁多的纳米材料虽为治疗耐药菌感染带来了新契机，但仍存在选择性差、生物安全性不理想和稳定性低等问题。针对上述问题，本项目以细菌细胞壁的特有成分肽聚糖合成途径中具有高度立体选择性的Mur连接酶为靶蛋白，结合石墨烯量子点（GQD）安全无毒、光学性质优异、稳定性好等优势，提出设计一种新型手性GQD，使其空间构型与靶蛋白匹配并与之发生特异性结合，且GQD还可通过与蛋白芳香氨基酸残基之间的π-π互作增强二者的结合作用，进而干扰肽聚糖合成，破坏细菌细胞壁的完整性使细菌死亡。通过理论计算辅助设计合成与靶标蛋白结合能力较强的手性GQD，结合实验研究抗菌性能并阐明抗菌机制。实现材料设计合成 - 结构性能研究 - 抗菌测试 - 反馈优化，为发展高选择性纳米抗菌药物提供新思路。

由于细菌耐药性的全球范围的传播，对公共卫生构成了严重威胁，引发了新型抗菌试剂的迫切需求。不易诱发细菌耐药性的纳米材料在治疗细菌感染方面取得了快速进展。然而，大多数抗菌纳米材料不能同时满足对杀菌剂的两个重要标准（有效的抗菌活性和针对微生物对哺乳动物细胞的高选择性毒性），并且相关机理尚未完全阐明。基于我们先前对纳米材料的合成和生物应用的研究，我们开发了新型手性分子功能化的纳米粒子（以D- / L-Glu功能化的石墨烯量子点为例），并研究了它们的抗菌作用以及手性对抗菌活性的影响。实验数据和理论模拟均表明，D型纳米颗粒可被细菌有效吸收，随后以高亲和力与MurD连接酶结合，并抑制其催化活性，抑制肽侧链肽聚糖的合成，导致细胞壁破坏和细胞内容物的泄漏，并最终杀死细菌。相反，其L型对应物无明显的抗菌作用，表明功能化纳米颗粒的手性结构通过与MurD的结合相互作用在其抗菌活性中起着至关重要的作用。手性纳米粒子对哺乳动物细胞无毒，因为PG独特地存在于细菌细胞壁中而不是哺乳动物中。这项研究为设计具有高选择性和高效抗菌活性的手性功能化纳米材料作为有前途的抗菌剂提供了新的视角。