The rise of antimicrobial resistance and multi‐drug resistant pathogens has necessitated explorations for novel antibiotic agents as the discovery of conventional antibiotics is becoming economically less viable and technically more challenging for biopharma. Antimicrobial peptides (AMPs) have emerged as a promising alternative because of their particular mode of action, broad spectrum and difficulty that microbes have in becoming resistant to them. The AMPs bacitracin, gramicidin, polymyxins and daptomycin are currently used clinically. However, their susceptibility to proteolytic degradation, toxicity profile, and complexities in large‐scale manufacture have hindered their development. To improve their proteolytic stability, methods such as integrating non‐canonical amino acids (ncAAs) into their peptide sequence have been adopted, which also improves their potency and spectrum of action. The benefits of ncAA incorporation have been made possible by solid‐phase peptide synthesis. However, this method is not always suitable for commercial production of AMPs because of poor yield, scale‐up difficulties, and its non‐‘green’ nature. Bioincorporation of ncAA as a method of integration is an emerging field geared towards tackling the challenges of solid‐phase synthesis as a green, cheaper, and scalable alternative for commercialisation of AMPs. This review focusses on the bioincorporation of ncAAs; some challenges associated with the methods are outlined, and notes are given on how to overcome these challenges. The review focusses particularly on addressing two key challenges: AMP cytotoxicity towards microbial cell factories and the uptake of ncAAs that are unfavourable to them. Overcoming these challenges will draw us closer to a greater yield and an environmentally friendly and sustainable approach to make AMPs more druggable.

Antimicrobial resistance is a critical global challenge in the 21st century, validating Sir Alexander Fleming’s warning about the misuse of antibiotics leading to resistant microbes. With a dwindling arsenal of effective antibiotics, it is imperative to concentrate on alternative antimicrobial strategies. Previous studies have not comprehensively discussed the advantages and limitations of various strategies, including bacteriophage therapy, probiotics, immunotherapies, photodynamic therapy, essential oils, nanoparticles and antimicrobial peptides (AMPs) within a single review. This review addresses that gap by providing an overview of these various non-antibiotic antimicrobial strategies, highlighting their pros and cons, with a particular emphasis on antimicrobial peptides (AMPs). We explore the mechanism of action of AMPs against bacteria, viruses, fungi and parasites. While these peptides hold significant promise, their application in mainstream drug development is hindered by challenges such as low bioavailability and potential toxicity. However, advancements in peptide engineering and chemical modifications offer solutions to enhance their clinical utility. Additionally, this review presents updates on strategies aimed at improving the cost, stability and selective toxicity of AMPs through the development of peptidomimetics. These molecules have demonstrated effective activity against a broad range of pathogens, making them valuable candidates for integration into surface coatings to prevent device-associated infections. Furthermore, we discuss various approaches for attaching and functionalising these peptides on surfaces. Finally, we recommend comprehensive in vivo studies to evaluate the efficacy of AMPs and their mimetics, investigate their synergistic combinations with other molecules and assess their potential as coatings for medical devices.

The ongoing battle against viral pandemics continues, with the possibility of future outbreaks. The search for effective antiviral compounds that can combat a diverse range of viruses continues to be a focal point of research. This study investigated the efficacy of two natural antimicrobial peptides (AMPs) (lactoferricin and LL-37), two synthetic AMPs (melimine and Mel4), and nine AMP mimics (758, 1091, 1096, 1083, 610, NAPL, 3-BIPL, 4-BIPL, and Sau-22) against influenza A virus strains H1N1 and H3N2, human adenovirus 5 (HAdV-5), and murine norovirus 1 (MNV-1). These compounds were tested using virus pre-treatment, cell pre-treatment, or post-cell entry treatment assays, electron microscopy, and circular dichroism (CD), alongside evaluations of cytotoxicity against the host cells. After virus pre-treatment, the AMP mimics 610 and Sau-22 had relatively low IC₅₀ values for influenza strains H1N1 (2.35 and 6.93 µM, respectively) and H3N2 (3.7 and 5.34 µM, respectively). Conversely, natural and synthetic AMPs were not active against these strains. For the non-enveloped viruses, the AMP Mel4 and mimic 1083 had moderate activity against HAdV-5 (Mel4 IC₅₀ = 47.4 µM; 1083 IC₅₀ = 47.2 µM), whereas all AMPs, but none of the mimics, were active against norovirus (LL-37 IC₅₀ = 4.2 µM; lactoferricin IC₅₀ = 23.18 µM; melimine IC₅₀ = 4.8 µM; Mel4 IC₅₀ = 8.6 µM). Transmission electron microscopy demonstrated that the mimics targeted the outer envelope of influenza viruses, while the AMPs targeted the capsid of non-enveloped viruses. CD showed that Mel4 adopted an α-helical structure in a membrane mimetic environment, but mimic 758 remained unstructured. The diverse activity against different virus groups is probably influenced by charge, hydrophobicity, size, and, in the case of natural and synthetic AMPs, their secondary structure. These findings underscore the potential of peptides and mimics as promising candidates for antiviral therapeutics against both enveloped and non-enveloped viruses.

Purpose: Antimicrobial peptides show promise as broad-spectrum agents and are less likely to induce rapid resistance. However, protease sensitivity limits their potential as antibiotic alternatives. Non-canonical amino acid incorporation may enhance stability but could impact other properties. Methods: The activities of four peptides (oligoarginine (PLR10), oligohomoarginine (PLHR10), Mel4, and Mel4HArg) were tested against strains of S. aureus , P. aeruginosa and E. coli. Circular dichroism (CD) was used to determine their secondary structure. Their MICs against E. coli and P. aeruginosa were re-examined after protease treatment. Cytotoxicities against L929 cell line were determined. Results: MICs for the four AMPs ranged from 31.25 to > 500 µM. Total substitution of arginine with homoarginine had minimal effect on MICs of PLR10, but increased the MICs of Mel4, e.g., against S. aureus ATCC 6538 from 31.25 to > 250 µM. In 30 mM SDS, substitution with homoarginine resulted in the loss of α-helical structures. Trypsin reduced PLR10 activity against E. coli and P. aeruginosa but had less effect on PLHR10. At 62.5 µM, PLR10 reduced E. coli growth by 20% compared to 90% for PLHR10. At 125 µM, PLR10 reduced P. aeruginosa growth by 22% compared to 70% for PLHR10. Mel4HArg retained activity against E. coli post-trypsin treatment but not against P. aeruginosa . The IC ₅₀ for PLR10 and PLHR10 (15.625 µM) against L929 cell line was below their MIC (31.25 µM), indicating low therapeutic potential. In contrast, Mel4 and Mel4HArg had IC50 > 500 µM, exceeding Mel4’s MIC for S. aureus (31.25–62.5 µM) and E. coli (125 µM), though not for Mel4HArg’s MIC against P. aeruginosa . Conclusion: The total arginine substitution with homoarginine in Mel4 and PLR10 resulted in improved stability but reduced activity in Mel4 and no improvement in cytotoxicity of PLR10, highlighting the need to find balance in optimizing AMP properties.

Antimicrobial peptides offer rapid, often membrane centered activity, but their therapeutic translation is limited by proteolytic instability, toxicity, reduced activity under physiological conditions, unfavourable pharmacokinetics, and manufacturing challenges. Peptidomimetics seek to retain the functional logic of antimicrobial peptides while improving these properties. This review presents a unified framework for peptidomimetic based antimicrobial discovery. It describes the fundamentals and classes of antimicrobial peptidomimetics, discusses mechanisms of antibacterial activity and the molecular basis of multidrug resistance. The review also highlights advances in molecular modelling and the growing role of artificial intelligence. A literature search was performed using PubMed, Scopus, Web of Science, and Google Scholar to review experimental, computational, and translational studies on peptidomimetics. Relevant studies were selected. The review examines the fundamentals of peptidomimetics, including key classes, structural modifications, and optimization strategies designed to overcome antimicrobial resistance. The review also highlights that effective antibacterial action involves electrostatic accumulation, selective membrane anchoring, transition into a membrane active conformation, and, in some cases, permeation to intracellular targets. In Gram-negative organisms, lipopolysaccharide organization and Ca²⁺/Mg²⁺ mediated cross linking increases the energetic barrier to membrane engagement. Furthermore, advances in synthetic methodologies, coupled with AI, are expected to enable faster and more efficient synthesis routes. Peptidomimetics seek to redefine antibacterial strategy by encoding resistance resilience into molecular design rather than relying on single target novelty. Their future impact will depend on integrating structure-activity relationships, mechanistic understanding with AI guided design.