Bacteria‐Responsive Self‐Assembly of Antimicrobial Peptide Nanonets for Trap‐and‐Kill of Antibiotic‐Resistant Strains

Abstract

Bacterial trapping using nanonets is a ubiquitous immune defense mechanism against infectious microbes. These nanonets can entrap microbial cells, effectively arresting their dissemination and rendering them more vulnerable to locally secreted microbicides. Inspired by this evolutionarily conserved anti‐infective strategy, a series of 15 to 16 residue‐long synthetic β‐hairpin peptides is herein constructed with the ability to self‐assemble into nanonets in response to the presence of bacteria, enabling spatiotemporal control over microbial killing. Using amyloid‐specific K114 assay and confocal microscopy, the membrane components lipoteichoic acid and lipopolysaccharide are shown to play a major role in determining the amyloid‐nucleating capacity as triggered by Gram‐positive and Gram‐negative bacteria respectively. These nanonets displayed both trapping and killing functionalities, hence offering a direct improvement from the trap‐only biomimetics in literature. By substituting a single turn residue of the non‐amyloidogenic BTT1 peptide, the nanonet‐forming BTT1‐3A analog is produced with comparable antimicrobial potency. With the same sequence manipulation approach, BTT2‐4A analog modified from BTT2 peptide showed improved antimicrobial potency against colistin‐resistant clinical isolates. The peptide nanonets also demonstrated robust stability against proteolytic degradation, and promising in vivo efficacy and biosafety profile. Overall, these bacteria‐responsive peptide nanonets are promising clinical anti‐infective alternatives for circumventing antibiotic resistance.

Multifunctional Antibacterial Nanonets Attenuate Inflammatory Responses through Selective Trapping of Endotoxins and Pro‐Inflammatory Cytokines

“…In summary, our peptide nanonets displayed promising anti‐inflammatory activity both in vitro and in vivo, thus expanding their repertoire of functionalities beyond that of antibacterial trap‐and‐kill. [ 9 ] The nanonets are postulated to specifically bind and entrap endotoxin and pro‐inflammatory cytokines by exploiting the abundance of negative charges on these inflammation mediators. This could potentially overcome the limitation in activity spectrum associated with target‐specific anti‐septic strategies, and minimize undesirable inactivation of the beneficial anti‐inflammatory mediators.…”

“…From our in-house library of 𝛽-hairpin AMPs, [9,11] we selected two representative fibrillating peptides previously demonstrated to display potent trap-and-kill activity against pathogenic bacteria, BTT1-3A and BTT2-4A, for investigating their anti-inflammatory activity, as compared to the non-fibrillating peptide BTT2-2A. Their sequence and properties are listed in Table S1, Supporting Information.…”

“…In addition, our system offers superior flexibility as specific functionalities of the nanonets can be readily fine-tuned through simple manipulation of the peptide sequence, as illustrated in both this manuscript and prior works from our group. [9,11]…”

“…[ 9 ] These peptide nanonets, which comprise extensively cross‐linked nanofibrils, displayed unique trap‐and‐kill dual‐functionalities, which present a direct upgrade from the trap‐only nanonets in nature which are reliant on other host immune components for antimicrobial activity. [ 10 ] Upon coming into contact with LPS, the peptide can either: (1) undergo fibrillation to form cross‐linked nanonets for physical trapping of nearby bacteria cells, [ 9 ] or (2) fold into hairpin conformations for membranolytic antimicrobial activity. [ 11 ] The side strands of our peptides carry three Leu–Lys repeat units, and the resulting polycationicity proved integral to facilitating interactions between the peptides and endotoxins.…”

“…[5,8] Inspired by the trap-and-kill immune defense strategy ubiquitous in nature, our group recently designed synthetic 𝛽-hairpin antimicrobial peptides (AMPs) with the ability to self-assemble into amyloid-like nanonets specifically in response to bacterial endotoxins. [9] These peptide nanonets, which comprise extensively cross-linked nanofibrils, displayed unique trap-and-kill dual-functionalities, which present a direct upgrade from the trap-only nanonets in nature which are reliant on other host immune components for antimicrobial activity. [10] Upon coming into contact with LPS, the peptide can either: (1) undergo fibrillation to form cross-linked nanonets for physical trapping of nearby bacteria cells, [9] or (2) fold into hairpin conformations for membranolytic antimicrobial activity.…”