Biofilms present a major problem to industry and healthcare worldwide. Composed of a population of surface-attached microbial cells surrounded by a protective extracellular polysaccharide matrix, they are responsible for increased tolerance to antibiotics, treatment failure and a resulting rise in antimicrobial resistance. Here we demonstrate that self-assembled peptide nanostructures composed of a diphenylalanine motif provide sufficient antibacterial activity to eradicate mature biofilm forms of bacteria widely implicated in hospital infections. Modification of terminal functional groups to amino (-NH₂), carboxylic acid (-COOH) or both modalities, and switch to d-isomers, resulted in changes in antibacterial selectivity and mammalian cell toxicity profiles. Of the three peptide nanotubes structures studied (NH₂-FF-COOH, NH₂-ff-COOH and NH₂-FF-NH₂), NH₂-FF-COOH demonstrated the most potent activity against both planktonic (liquid, free-floating) and biofilm forms of bacteria, possessing minimal mammalian cell toxicity. NH₂-FF-COOH resulted in greater than 3 Log₁₀ CFU/mL viable biofilm reduction (>99.9%) at 5 mg/mL and total biofilm kill at 10 mg/mL against Staphylococcus aureus after 24 hours exposure. Scanning electron microscopy proved that antibiofilm activity was primarily due to the formation of ion channels and/or surfactant-like action, with NH₂-FF-COOH and NH₂-ff-COOH capable of degrading the biofilm matrix and disrupting cell membranes, leading to cell death in Gram-positive bacterial isolates. Peptide-based nanotubes are an exciting platform for drug delivery and engineering applications. This is the first report of using peptide nanotubes to eradicate bacterial biofilms and provides evidence of a new platform that may alleviate their negative impact throughout society.

Statement of significance

We outline, for the first time, the antibiofilm activity of diphenylalanine (FF) peptide nanotubes. Biofilm bacteria exhibit high tolerance to antimicrobials 10-10,000 times that of free-flowing planktonic forms. Biofilm infections are difficult to treat using conventional antimicrobial agents, leading to a rise in antimicrobial resistance. We discovered nanotubes composed of NH₂-FF-COOH demonstrated potent activity against staphylococcal biofilms implicated in hospital infections, resulting in complete kill at concentrations of 10 mg/mL. Carboxylic acid terminated FF nanotubes were able to destroy the exopolysaccharide architecture of staphylococcal biofilms expressing minimal toxicity highlighting their potential for use in patients, whilst amidated (NH₂-FF-NH₂) forms demonstrated reduced antibiofilm efficacy and significant toxicity. These results contribute significantly to the development of innovative antibacterial technologies and peptide nanomaterials.

中文翻译：

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自组装二苯丙氨酸肽纳米管有选择地根除细菌生物膜感染

生物膜给全世界的工业和医疗保健提出了一个主要问题。它们由一群表面附着的微生物细胞组成，周围有保护性的细胞外多糖基质，它们负责增加对抗生素的耐受性，治疗失败并导致抗菌素耐药性上升。在这里，我们证明了由二苯丙氨酸基序组成的自组装肽纳米结构提供了足够的抗菌活性，以根除广泛涉及医院感染的细菌的成熟生物膜形式。末端官能团修饰为氨基（-NH ₂，羧酸（-COOH）或两种方式，并转换为D-异构体，导致抗菌选择性和哺乳动物细胞毒性谱的变化。在研究的三种肽纳米管结构（NH ₂ -FF-COOH，NH ₂ -ff-COOH和NH ₂ -FF-NH ₂）中，NH ₂ -FF-COOH对两种浮游生物（液体，游离-细菌）和生物膜形式的细菌，具有最小的哺乳动物细胞毒性。NH ₂ -FF-COOH在5 mg / mL时对金黄色葡萄球菌的存活生物膜减少量大于3 Log ₁₀ CFU / mL（> 99.9％），在10 mg / mL时杀死总生物膜暴露24小时后。扫描电子显微镜证明，抗生物膜活性主要是由于离子通道的形成和/或类似表面活性剂的作用，其中NH ₂ -FF-COOH和NH ₂ -ff-COOH能够降解生物膜基质并破坏细胞膜，导致革兰氏阳性细菌分离物中的细胞死亡。基于肽的纳米管是用于药物输送和工程应用的令人兴奋的平台。这是使用肽纳米管根除细菌生物膜的第一份报告，并提供了减轻其对整个社会的负面影响的新平台的证据。

重要声明

我们首次概述了二苯丙氨酸（FF）肽纳米管的抗生物膜活性。生物膜细菌对抗菌剂的抵抗力是自由流动的浮游生物形式的10-10,000倍。使用常规抗微生物剂难以治疗生物膜感染，从而导致抗微生物剂耐药性上升。我们发现，由NH ₂ -FF-COOH组成的纳米管表现出了针对与医院感染有关的葡萄球菌生物膜的有效活性，在10 mg / mL的浓度下可导致完全杀灭。羧酸封端的FF纳米管能够破坏葡萄球菌生物膜的胞外多糖结构，表现出最小的毒性，突出显示了其在酰胺化患者中的潜在应用（NH ₂ -FF-NH ₂）形式显示出降低的抗生物膜功效和明显的毒性。这些结果为创新的抗菌技术和肽纳米材料的发展做出了重要贡献。