Short self‐assembling cationic antimicrobial peptide mimetics based on a 3,5‐diaminobenzoic acid scaffold

Abstract

Infections caused by Staphylococcal and Micrococcal species represent a major public health burden. Although treatments do exist, these tend to be associated with cytotoxic effects; furthermore, the emergence of antimicrobial resistance presents an immediate challenge. New classes of active compounds are required to address these threats to human health. Here we present a de novo peptidomimetic strategy that produces self‐assembling cationic antimicrobials. To identify a candidate compound with bactericidal activity, a small library of 8 peptidomimetics comprising ultrashort peptide sequences attached to a 3,5‐diaminobenzoic acid scaffold was generated and tested against Micrococcus luteus and Staphylococcus aureus. Self‐assembly appears to be the driving force for increased potency, likely by contributing to increased local surface charge density and peptide mass and producing a multivalent effect that enhances electrostatic interactions with negatively charged bacterial membranes, causing membrane disruption. The most active library member C7 forms patched micellar nanoparticles and has an activity higher than that of known natural antimicrobial peptides against M luteus. C7 also shows activity comparable to that of gramicidin S and the standard antibiotic vancomycin used in antibacterial therapy, but with a greater selectivity index. Importantly, C7 is also nontoxic and nonhemolytic, unlike the currently administered vancomycin, which can cause acute renal failure, and gramicidin S, which is highly hemolytic in nature. The short sequence length, ease of design, convenient synthesis strategy, and presence of a substitutable hydrophobic residue that enables self‐assembly into different nanostructures make this model compound highly attractive for generating cost‐effective, rapid‐acting peptide‐based antimicrobials.

Rational Design of Amphiphilic Fluorinated Peptides: Evaluation of Self-Assembly Properties and Hydrogel Formation

“…The replacement of a single C-H bond with C-F is generally considered to be isosteric. 20,21 To date, investigations of the effects of fluorinated amino acids on hydrophobicity 22,23 , secondary structure formation 24,25 , protein-protein interactions 26 , amyloid folding kinetics 27,28 , proteolytic stability 29 , chemical and biological properties of fluorinated peptide-based materials 30 , and on the integration of fluorine into living organisms 31,32 have been reported by our group. Vast majority of previous studies including our own efforts examining fluorinated amino acids in the context of peptide and protein chemistry were limited to the incorporation of one or only a few of these building blocks.…”

Enhancing Antimicrobial Peptide Potency through Multivalent Presentation on Coiled-Coil Nanofibrils

“…41,44−52 We recently reported an ultrashort self-assembling cationic antimicrobial peptidomimetic scaffold based on 3,5-diaminobenzoic acid that forms patched micellar nanostructures showing selectivity toward Gram-positive cocci bacteria like S. aureus and Micrococcus luteus. 30 Among the different self-assembled peptide scaffolds that can be used for the presentation of AMPs 20,34 or other bioactive ligands, 53−57 the application of the coiled-coil peptide folding motif possesses several advantages, including lower cytotoxicity, higher water solubility, and higer thermostability. 58,59 The coiled-coil motif comprises two to seven αhelices that wrap around each other to form a left-handed supercoil.…”

“…One important factor for an ideal drug candidate is its ability to show rapid microbial killing kinetics. 30 In order to further understand the kinetics of cell death induced by IN4 and FF03 + IN4, timekill kinetics assays of IN4 and FF03 + IN4 toward MRSA (ATCC 43300) at their MICs were performed (Figure 4).…”

“…An ideal peptide antibiotic drug needs to be nonhemolytic and noncytotoxic. 30 Therefore, the hemolytic potential of FF03 + IN4 and IN4 was assessed up to a concentration of 100 μg/mL. As a positive control (100% lysis), 1% polyoxyethylene octyl phenyl ether (Triton X-100) dissolved in phosphate buffer was used, while hRBCs treated with phosphate buffer served as a negative control (Figure 6).…”

“…Though several natural and synthetic scaffolds such as aptamers, liposomes, hydrogels, metal nanoparticles, polymers, dendritic systems, carbon nanotubes, and cyclodextrins are being used for this purpose, the application of peptide-based nanostructures is connected to various advantages. These advantages encompass biocompatibility, biodegradability, and ease of design, synthesis, and characterization compared with, e.g., other polymeric systems. − Recent examples that highlight the benefits of using peptide-based nanostructures with inherent antimicrobial activity as scaffolds for AMP presentation include the natural AMP melittin bound to a β-sheet-forming self-assembling peptide, which led to improved membrane selectivity and cytocompatibility; self-assembling arginine- or lysine-rich antimicrobial lipopeptides with tunable hemolytic activity and cell specificity; , a bacterial-selective pH-responsive octapeptide hydrogel; a thermoresponsive antibacterial peptide hydrogel; anti-methicillin-resistant Staphylococcus aureus (anti-MRSA) peptide hydrogels; − and bacterial-selective hybrid AMPs. − The development of ultrashort self-assembling peptides with inherent antimicrobial activity is also currently being studied and presents another promising strategy. ,− We recently reported an ultrashort self-assembling cationic antimicrobial peptidomimetic scaffold based on 3,5-diaminobenzoic acid that forms patched micellar nanostructures showing selectivity toward Gram-positive cocci bacteria like S. aureus and Micrococcus luteus. …”