Discovery and Characterization of a Rapidly Fungicidal and Minimally Toxic Peptoid against Cryptococcus neoformans

Quaternized 1,2,3-Triazolyl Content and Modulation Potentiate Antibacterial and Antifungal Activities of Amphipathic Peptoids

Bioinspired from cationic antimicrobial peptides, sequence-defined triazolium-grafted peptoid oligomers (6- to 12-mer) were designed to adopt an amphipathic helical polyproline I-type structure. Their evaluation on a panel of bacterial strains (Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus, and Enterococcus faecalis), pathogenic fungi (Candida albicans, Cryptococcus neoformans, and Aspergillus fumigatus), and human cells (hRBC, BEAS-2B, Caco-2, HaCaT, and HepG2) enabled the identification of two heptamers with improved activity to selectively fight Staphylococcus aureus pathogens. Modulation of parameters such as the nature of the triazolium and hydrophobic/lipophilic side chains, the charge content, and the sequence length drastically potentiates activity and selectivity. Besides, the ability to block the proinflammatory effect induced by lipopolysaccharide or lipoteichoic acid was also explored. Finally, biophysical studies by circular dichroism and fluorescence spectroscopies strongly supported that the bactericidal effect of these triazolium-grafted oligomers was primarily due to the selective disruption of the bacterial membrane.

Recent advances in peptoids as promising antimicrobial agents to target diverse microbial species

The emergence of multidrug-resistant microbial species has become a global health concern, calling for novel antimicrobial agents. Peptoids, a class of synthetic peptidomimetics with unique structural properties, exhibit antimicrobial activity against a broad-spectrum of microbes, in addition to their stability to enzymatic degradation, selectivity, and relative ease of synthesis. Thus, peptoids have great potential in combating various drug-resistant pathogenic microbes. This review provides a comprehensive analysis of the recent advances in utilizing peptoids as effective antimicrobial agents against a wide range of bacteria, fungi, viruses, and parasites. In addition, some of the synthetic strategies and antimicrobial mechanisms are discussed. The imperfections of antimicrobial peptoids and the defects in current antimicrobial peptoids research are pointed out and promising directions for future development in peptoids are highlighted, to pave the way for innovating better antimicrobial peptoids to address the challenges posed by multidrug-resistant microbial species.

Navigating the Expansive Landscapes of Soft Materials: A User Guide for High-Throughput Workflows

Synthetic polymers are highly customizable with tailored structures and functionality, yet this versatility generates challenges in the design of advanced materials due to the size and complexity of the design space. Thus, exploration and optimization of polymer properties using combinatorial libraries has become increasingly common, which requires careful selection of synthetic strategies, characterization techniques, and rapid processing workflows to obtain fundamental principles from these large data sets. Herein, we provide guidelines for strategic design of macromolecule libraries and workflows to efficiently navigate these high-dimensional design spaces. We describe synthetic methods for multiple library sizes and structures as well as characterization methods to rapidly generate data sets, including tools that can be adapted from biological workflows. We further highlight relevant insights from statistics and machine learning to aid in data featurization, representation, and analysis. This Perspective acts as a "user guide" for researchers interested in leveraging high-throughput screening toward the design of multifunctional polymers and predictive modeling of structure-property relationships in soft materials.

Synthesis and Characterization of Derivatives of the Antifungal Peptoid RMG8-8

Cryptococcal meningitis, caused by the fungal pathogen Cryptococcus neoformans, is a devastating disease with a mortality rate of over 80%. Due to the increasing prevalence of resistance to antifungals and the high mammalian toxicity of current treatments, the development of new antifungal therapies is vital. In an effort to improve the biological properties of a previously discovered antifungal peptoid, termed RMG8-8, an iterative structure-activity relationship study was conducted. This three-round study sought to optimize the structure of RMG8-8 by focusing on three main structural components: the lipophilic tail, aliphatic side chains, and aromatic side chains. In addition to antifungal testing against C. neoformans, cytotoxicity testing was also performed on all derivatives against human liver cells, and select promising compounds were tested for hemolytic activity against human red blood cells. A number of derivatives containing unique aliphatic or aromatic side chains had antifungal activity similar to RMG8-8 (MIC = 1.56 μg/mL), but all of these compounds were more toxic than RMG8-8. While no derivative was improved across all biological tests, modest improvements were made to the hemolytic activity with compound 9, containing isobutyl side chains in positions 2 and 5, compared to RMG8-8 (HC₁₀ = 130 and 75 μg/mL, respectively). While this study did not yield a dramatically optimized RMG8-8 derivative, this result was not totally unexpected given the remarkable selectivity of this compound from discovery. Nonetheless, this study is an important step in the development of RMG8-8 as a viable antifungal therapeutic.