Antibiotic-resistant microorganisms have become a serious threat to public health, resulting in hospital infections, the majority of which are caused by commonly used urinary tract catheters. Strategies for preventing bacterial adhesion to the catheters’ surfaces have been potentially shown as effective methods, such as coating thesurface with antimicrobial biomolecules. Here, novel antimicrobial peptides (AMPs) were designed as potential biomolecules to prevent antibiotic-resistant bacteria from binding to catheter surfaces. Thiolated AMPs were synthesized using solid-phase peptide synthesis (SPPS), and prep-HPLC was used to obtain AMPs with purity greater than 90%. On the other side, the silicone catheter surface was activated by UV/ozone treatment, followed by functionalization with allyl moieties for conjugation to the free thiol group of cystein in AMPs using thiol-ene click chemistry. Peptide-immobilized surfaces were found to become more resistant to bacterial adhesion while remaining biocompatible with mammalian cells. The presence and site of conjugation of peptide molecules were investigated by immobilizing them to catheter surfaces from both ends (C-Pep and Pep-C). It was clearly demonstrated that AMPs conjugated to the surface via theirN terminus have a higher antimicrobial activity. This strategy stands out for its effective conjugation of AMPs to silicone-based implant surfaces for the elimination of bacterial infections.

Antimicrobial peptides (AMPs) are crucial components of the innate immune system in all living organisms, playing a vital role in the body’s defense against diseases and infections. The immune system’s primary functions include preventing disease‐causing agents from entering the body and eliminating them without causing harm. These peptides exhibit broad‐spectrum activity against bacteria, viruses, fungi, parasites, and cancer cells. They are secreted by innate and epithelial cells and contribute to host defense by inducing cellular activities such as cell migration, proliferation, differentiation, cytokine production, angiogenesis, and wound healing. In response to the growing challenge of bacterial resistance to antimicrobial agents, alternative drugs and new antibacterial molecules are being explored. In a previous study, NET AMPs were synthesized and their antimicrobial effects were determined. The current study extends this work by assessing the effects of these peptides on the immune system through cell culture experiments and ELISA. Specifically, the study investigated how different concentrations of these peptides influence the secretion of interleukin‐6 (IL‐6), tumor necrosis factor‐α (TNF‐α), and interferon‐γ (IFN‐γ) in mouse macrophages. Among the synthesized peptides, NET1 and NET2 demonstrated low cytotoxicity in TIB‐71 RAW 264.7 macrophages. These peptides induced an anti‐inflammatory response and reduced IL‐6 expression in the absence of LPS stimulation, while simultaneously increasing IFN‐γ and TNF‐α secretion. These findings suggest that NET1 and NET2 peptides possess both anti‐inflammatory and pro‐inflammatory properties, highlighting their potential role in modulating immune responses.

Trichomonas vaginalis is the causative agent of trichomoniasis, the most common non-viral sexually transmitted infection worldwide. In these cases, 5-Nitroimidazoles, particularly metronidazole (MTZ), remain the primary treatment option; however, resistance to MTZ has been increasingly reported. This study aimed to evaluate the in vitro activity of D-form synthetic antimicrobial peptides and investigate transcriptional differences associated with MTZ resistance and peptide treatment in T. vaginalis. D-form synthetic peptides (D-TN1, D-TN3, and D-TN6) developed in the R&D Laboratory of Acibadem University were tested against metronidazole-susceptible (T. vaginalis ATCC 30236) and metronidazole-resistant (T. vaginalis ATCC 50143) strains by minimum lethal concentration (MLC) assays. D-TN1 exhibited an MLC of 16 µg/mL in both strains, whereas D-TN3 and D-TN6 exhibited MLC values of 32 µg/mL and 16–32 µg/mL, respectively. Comparative transcriptomic analysis was conducted to investigate transcriptional differences. Differential gene expression analysis identified 3395 genes between the resistant and susceptible isolates and 3060 genes in the D-TN1-treated resistant isolate (FDR < 0.05, |log₂FC| ≥ 1). D-TN1 treatment in the resistant isolate was associated with downregulation of ribosomal and metabolic pathways. If confirmed with further in vivo studies, this new antimicrobial peptide may become a new therapeutic alternative in the treatment of trichomoniasis in the future.

Purpose: In recent years, antimicrobial resistance is one of the biggest and most important reasons for the difficulties in treating infections and threatening public health. One of the priority pathogens listed by the World Health Organization is carbapenem resistant Enterobacterales (Klebsiella pneumoniae). Antimicrobial peptides are considered as alternatives to antibiotics due to their broad-spectrum antibacterial properties and the difficulty of developing resistance. In this study, we investigated the antimicrobial effects of NET1 and NET3 peptides, which are known to have antimicrobial effects on different bacteria, on carbapenem-resistant and -susceptible K. pneumoniae control strains. Methods: NET1 and NET3 peptides were synthesized and purified. In vitro antibacterial activity of the peptides against carbapenem-resistant and susceptible K. pneumoniae was demonstrated by minimum inhibitory concentration test and minimum bactericidal concentration test. In addition, the mechanism of action of the peptides on carbapenem-resistant K. pneumoniae cells was investigated by scanning electron microscopy. Results: The minimum inhibitory concentration and minimum bactericidal concentration results of NET1 peptide are 4 µg/ml for carbapenem-resistant K. pneumoniae and 2 µg/ml for NET3 peptide. Scanning electron microscope imaging has shown that NET3 peptide exhibits antibacterial activity by damaging the carbapenem-resistant K. pneumoniae cell membrane and disrupting the permeability of the outer membrane. Conclusion: When our results are evaluated, we show that NET1 and NET3 peptide has the potential to be a new generation broad-spectrum antibiotic candidate that can be used for the treatment of carbapenem-resistant K. pneumoniae infection.