To Örebro University

Bacterial resistance towards antibiotics is a major global health issue. Very few novel antimicrobial agents and therapies have been made available for clinical use during the past decades, despite an increasing need. Antimicrobial peptides have been intensely studied, many of which have shown great promise in vitro. We have previously demonstrated that the bacteriocin Plantaricin NC8 αβ (PLNC8 αβ) from Lactobacillus plantarum effectively inhibits Staphylococcus spp., and shows little to no cytotoxicity towards human keratinocytes. However, due to its limitations in inhibiting gram-negative species, the aim of the present study was to identify novel antimicrobial peptidomimetic compounds with an enhanced spectrum of activity, derived from the β peptide of PLNC8 αβ. We have rationally designed and synthesized a small library of lipopeptides with significantly improved antimicrobial activity towards both gram-positive and gram-negative bacteria, including the ESKAPE pathogens. The lipopeptides consist of 16 amino acids with a terminal fatty acid chain and assemble into micelles that effectively inhibit and kill bacteria by permeabilizing their cell membranes. They demonstrate low hemolytic activity and liposome model systems further confirm selectivity for bacterial lipid membranes. The combination of lipopeptides with different antibiotics enhanced the effects in a synergistic or additive manner. Our data suggest that the novel lipopeptides are promising as future antimicrobial agents, however additional experiments using relevant animal models are necessary to further validate their in vivo efficacy.

The skin is the largest organ of the human body. Wounds disrupt the functions of the skin and can have catastrophic consequences for an individual resulting in significant morbidity and mortality. Wound infections are common and can substantially delay healing and can result in non-healing wounds and sepsis. Early diagnosis and treatment of infection reduce risk of complications and support wound healing. Methods for monitoring of wound pH can facilitate early detection of infection. Here we show a novel strategy for integrating pH sensing capabilities in state-of-the-art hydrogel-based wound dressings fabricated from bacterial nanocellulose (BC). A high surface area material was developed by self-assembly of mesoporous silica nanoparticles (MSNs) in BC. By encapsulating a pH-responsive dye in the MSNs, wound dressings for continuous pH sensing with spatiotemporal resolution were developed. The pH responsive BC-based nanocomposites demonstrated excellent wound dressing properties, with respect to conformability, mechanical properties, and water vapor transmission rate. In addition to facilitating rapid colorimetric assessment of wound pH, this strategy for generating functional BC-MSN nanocomposites can be further be adapted for encapsulation and release of bioactive compounds for treatment of hard-to-heal wounds, enabling development of novel wound care materials.

Multidrug resistance bacteria constitue an increasing global health problem and the development of novel therapeutic strategies to face this challenge is urgent. Antimicrobial peptides have been proven as potent agents against pathogenic bacteria shown by promising in vitro results. The aim of this study was to characterize the antimicrobial effects of PLNC8 αβ on cell signaling pathways and inflammatory responses of human keratinocytes infected with S. aureus. PLNC8 αβ did not affect the viability of human keratinocytes but upregulated several cytokines (IL-1β, IL-6, CXCL8), MMPs (MMP1, MMP2, MMP9, MMP10) and growth factors (VEGF and PDGF-AA), which are essential in cell regeneration. S. aureus induced the expression of several inflammatory mediators at the gene and protein level and PLNC8 αβ was able to significantly suppress these effects. Intracellular signaling events involved primarily c-Jun via JNK, c-Fos and NFκB, suggesting their essential role in the initiation of inflammatory responses in human keratinocytes. PLNC8 αβ was shown to modulate early keratinocyte responses, without affecting their viability. The peptides have high selectivity towards S. aureus and were efficient at eliminating the bacteria and counteracting their inflammatory and cytotoxic effects, alone and in combination with low concentrations of gentamicin. We propose that PLNC8 αβ may be developed to combat infections caused by Staphylococcus spp.