Establishing the selective phospholipid membrane coordination, permeation and lysis properties for a series of 'druggable' supramolecular self-associating antimicrobial amphiphiles

Supramolecular Self-Associating Amphiphiles Inhibit Biofilm Formation by the Critical Pathogens, Pseudomonas aeruginosa and Candida albicans

In 2019, 4.95 million deaths were directly attributed to antimicrobial-resistant bacterial infections globally. In addition, the mortality associated with fungal infections is estimated at 1.7 million annually, with many of these deaths attributed to species that are no longer susceptible to traditional therapeutic regimes. Herein, we demonstrate the use of a novel class of supramolecular self-associating amphiphilic (SSA) salts as antimicrobial agents against the critical pathogens Pseudomonas aeruginosa and Candida albicans. We also identify preliminary structure-activity relationships for this class of compound that will aid the development of next-generation SSAs demonstrating enhanced antibiofilm activity. To gain insight into the possible mode of action for these agents, a series of microscopy studies were performed, taking advantage of the intrinsic fluorescent nature of benzothiazole-substituted SSAs. Analysis of these data showed that the SSAs interact with the cell surface and that a benzothiazole-containing SSA inhibits hyphal formation by C. albicans.

Tools to enable the study and translation of supramolecular amphiphiles

This tutorial review focuses on providing a summary of the key techniques used for the characterisation of supramolecular amphiphiles and their self-assembled aggregates; from the understanding of low-level molecular interactions, to materials analysis, use of data to support computer-aided molecular design and finally, the translation of this class of compounds for real world application, specifically within the clinical setting. We highlight the common methodologies used for the study of traditional amphiphiles and build to provide specific examples that enable the study of specialist supramolecular systems. This includes the use of nuclear magnetic resonance spectroscopy, mass spectrometry, X-ray scattering techniques (small- and wide-angle X-ray scattering and single crystal X-ray diffraction), critical aggregation (or micelle) concentration determination methodologies, machine learning, and various microscopy techniques. Furthermore, this review provides guidance for working with supramolecular amphiphiles in in vitro and in vivo settings, as well as the use of accessible software programs, to facilitate screening and selection of druggable molecules. Each section provides: a methodology overview - information that may be derived from the use of the methodology described; a case study - examples for the application of these methodologies; and a summary section - providing methodology specific benefits, limitations and future applications.

Phospholipid headgroup composition modulates the molecular interactions and antimicrobial effects of sulfobetaine zwitterionic detergents against the "ESKAPE" pathogen Pseudomonas aeruginosa

We determine the efficacy for three known structurally related, membrane active detergents against multidrug resistant and wild type strains of Pseudomonas aeruginosa. Accessible solution state NMR experiments are used to quantify phospholipid headgroup composition of the microbial membranes and to gain molecular level insight into antimicrobial mode of action.

Noncovalent Bile Acid Oligomers as Facial Amphiphilic Antimicrobials

New antimicrobial agents are needed to address the ever-growing risk of bacterial resistance, particularly for methicillin- and vancomycin-resistant Staphylococcus aureus (S. aureus). Here, we report a class of bile acid oligomers as facial amphiphilic antimicrobials, which are noncovalently fabricated by cholic acid (CA) and deoxycholic acid (DCA) with polyamines (e.g., diamines, diethylenetriamine, spermidine, and spermine). The antibacterial activities of these bile acid oligomers (CA/polyamines and DCA/polyamines) against S. aureus become stronger with increasing the amine group numbers of polyamines without obviously enhanced cytotoxicity and skin irritation. DCA/spermine, entirely composed of natural products, exhibits the best antibacterial activity but the lowest cytotoxicity and the weakest skin irritation. All CA/polyamines and DCA/polyamines form well-ordered ribbon-like aggregates, collecting numerous facial amphiphilic structures to significantly enhance the interactions with bacterial membranes. In particular, the biogenic polyamines with more than two amine groups provide extra positively charged sites, hence facilitating the binding of bile acid oligomers to the negatively charged outer membrane of the bacteria via electrostatic interaction. This in turn promotes more oligomeric bile acid units that can be inserted into the membrane through hydrophobic interaction between bile acids and lipid domains. The noncovalently constructed and separable amphiphilic antimicrobials can avoid the long-term coexistence of microorganisms and antibacterial molecules in different acting modes. Therefore, the noncovalent bile acid oligomers, especially those with higher oligomerization degrees, can be a potential approach to effectively enhance antibacterial activity, improve environmental friendliness, and reduce bacterial drug resistance.

Cavity Size Effect on Host-Guest Property of Tiara-like Structural Mn(SR)2n Nanoclusters Probed by NMR Spectroscopy

The lack of detect technology hinders the understanding of host-guest (H-G) chemical properties for thiolate-protected tiara-like structural nanoclusters (Mn(SR)2n). In this work, NMR spectroscopy is demonstrated as a powerful tool to probe the H-G structure of Mn(SR)2n both experimentally and theoretically. A low-field shifting and wide chemical shift (CS) signal of the H nucleus in CH2Cl2 is observed in the NMR spectrum of the mixture of CH2Cl2 and Pd8(PET)16 (PET is 2-phenylethanethiol), agreeing with the theoretical results that a deshielding area appears in the central cavity of Pd8(SR)16. All Mn(SR)2n own similar nucleus-independent chemical shift maps and deshielding cavities, which means that the H nucleus in small molecules trapped by Mn(SR)2n should have consistent low-field shifted CSs. However, such a phenomenon was only observed in the NMR spectrum of the mixed solution of Pd8(SR)16 and CH2Cl2, indicating that Pd8(SR)16 is the only one in the series of Pdn(SR)2n (n = 4~16) analogues that can capture a CH2Cl2, the H-G properties of Mn(SR)2n are highly dependent on their cavity sizes, and a guest molecule only inserts into the matching cavity of Mn(SR)2n. We anticipate that the realization of such convenient probe strategy will give a deeper understanding of the H-G properties of Mn(SR)2n.

A water-soluble membrane transporter for biologically relevant cations

Synthetic ionophores are promising therapeutic targets, yet poor water solubility limits their potential for translation into the clinic. Here we report a water soluble, supramolecular self-associating amphiphile (SSA) with cation transport function.