Development of antibacterial agents and materials

在研究这些材料发挥抗菌活性的机理的过程中，我们发现精氨酸含量对凝胶的细胞毒活性有很大的影响。基于这一发现，我们设计了一种新型的多肽凝胶，其材料表面可以有效杀灭包括多重耐药铜绿假单胞菌在内的革兰氏阳性和阴性细菌。实现活性不需要添加抗菌剂。在1.5wt%或更高浓度下制备的凝胶显示出对细菌的高效力，但对人类红细胞以及哺乳动物间充质干细胞具有细胞相容性。流变学研究表明，该凝胶具有中等硬度，表现出剪切稀薄的恢复行为，允许通过简单的注射器给药。这种水凝胶可用于清洁表面以抑制潜在的感染，此外，还可被输送到受感染的部位，在那里细菌细胞在接触时被杀死。在这项研究的过程中，我们偶然发现了一种新的可溶性多肽，它可以有效地杀死癌细胞。我们以这一发现为基础，设计了一种18个残基的抗癌肽SVS1，其作用机制利用了癌细胞膜外叶上的异常脂质成分。这种组合物使这些细胞的表面相对于非癌细胞具有相对的电负性。SVS1被设计成在水溶液中保持未折叠和不活跃，但优先在癌细胞表面折叠，采用能够破坏膜的两亲性β发夹结构。膜诱导折叠是由多肽与癌细胞带负电荷的膜表面之间的静电相互作用驱动的。SVS1对A549(肺癌)、KB(表皮癌)、MCF 7(乳腺癌)和MDA MB 436(乳腺癌)等多种癌细胞具有活性。然而，对具有典型膜成分的非肿瘤细胞，如人脐静脉内皮细胞和红细胞的细胞毒性很低。CD光谱、适当设计的多肽对照、基于细胞的研究、脂质体渗漏分析和电子显微镜支持预期的作用机制，从而导致对癌细胞的优先杀伤。我们计划探索这种多肽的用途，并在小鼠模型中设计相关的多肽。

In the course of studying the mechanism by which these materials exert their antibacterial activity, we have discover that arginine content greatly influences the cytotoxic activity of the gels. Based on this discovery, we have designed a new class of peptide based gel, whose material surface can actively kill Gram positive and negative bacteria including multi drug resistant P. aeruginosa. No added antibacterial agents are necessary to realize activity. Gels prepared at 1.5 wt % or higher concentration, demonstrate high potency against bacteria, but are cytocompatible towards human erythrocytes as well as mammalian mesenchymal stem cells. Rheological studies indicate that the gel is moderately stiff and displays shear-thin recovery behavior, allowing its delivery via simple syringe. The hydrogel can be applied to clean surfaces to inhibit potential infections, and in addition, can be delivered to an infected site where bacterial cells are killed on contact. During the course of this study, we made a serendipitous discovery of a new class of soluble peptide that is effective at killing cancer cells. We used this discovery as the foundation to design an 18 residue anticancer peptide, SVS1, whose mechanism of action takes advantage of the aberrant lipid composition presented on the outer leaflet of cancer cell membranes. This composition makes the surface of these cells relatively electronegative relative to non-cancerous cells. SVS1 is designed to remain unfolded and inactive in aqueous solution but preferentially fold at the surface of cancer cells, adopting an amphiphilic beta hairpin structure capable of membrane disruption. Membrane induced folding is driven by electrostatic interaction between the peptide and the negatively charge membrane surface of cancer cells. SVS1 is active against a variety of cancer cell lines such as A549 (lung carcinoma), KB (epidermal carcinoma), MCF 7 (breast carcinoma) and MDA MB 436 (breast carcinoma). However, the cytotoxicity towards non-cancerous cells having typical membrane compositions, such as HUVEC and erythrocytes, is low. CD spectroscopy, appropriately designed peptide controls, cell based studies, liposome leakage assays and electron microscopy support the intended mechanism of action, which leads to preferential killing of cancerous cells. We plan to explore the utility of this peptide and design relatives in mouse models.