Rapid eradication of vancomycin and methicillin-resistant Staphylococcus aureus by MDP1 antimicrobial peptide coated on photocrosslinkable chitosan hydrogel: in vitro antibacterial and in silico molecular docking studies.

Introduction: Antibiotic resistance and weak bioavailability of antibiotics in the skin due to systemic administration leads to failure in eradication of vancomycin- and methicillin-resistant Staphylococcus aureus (VRSA and MRSA)-associated wound infections and subsequent septicemia and even death. Accordingly, this study aimed at designing a photocrosslinkable methacrylated chitosan (MECs) hydrogel coated by melittin-derived peptide 1 (MDP1) that integrated the antibacterial activity with the promising skin regenerative capacity of the hydrogel to eradicate bacteria by burst release strategy. Methods: The MECs was coated with MDP1 (MECs-MDP1), characterized, and the hydrogel-peptide interaction was evaluated by molecular docking. Antibacterial activities of MECs-MDP1 were evaluated against VRSA and MRSA bacteria and compared to MECs-vancomycin (MECs-vanco). Antibiofilm activity of MECs-MDP1 was studied by our novel 'in situ biofilm inhibition zone (IBIZ)' assay, and SEM. Biocompatibility with human dermal fibroblast cells (HDFs) was also evaluated. Results and Discussion: Molecular docking showed hydrogen bonds as the most interactions between MDP1 and MECs at a reasonable affinity. MECs-MDP1 eradicated the bacteria rapidly by burst release strategy whereas MECs-vanco failed to eradicate them at the same time intervals. Antibiofilm activity of MECs-MDP1 were also proved successfully. As a novel report, molecular docking analysis has demonstrated that MDP1 covers the structure of MECs and also binds to lysozyme with a reasonable affinity, which may explain the inhibition of lysozyme. MECs-MDP1 was also biocompatible with human dermal fibroblast skin cells, which indicates its safe future application. The antibacterial properties of a photocrosslinkable methacrylated chitosan-based hydrogel coated with MDP1 antimicrobial peptide were successfully proved against the most challenging antibiotic-resistant bacteria causing nosocomial wound infections; VRSA and MRSA. Molecular docking analysis revealed that MDP1 interacts with MECs mainly through hydrogen bonds with reasonable binding affinity. MECs-MDP1 hydrogels eradicated the planktonic state of bacteria by burst release of MDP1 in just a few hours whereas MECs-vanco failed to eradicate them. inhibition zone assay showed the anti-biofilm activity of the MECs-MDP1 hydrogel too. These findings emphasize that MECs-MDP1 hydrogel would be suggested as a biocompatible wound-dressing candidate with considerable and rapid antibacterial activities to prevent/eradicate VRSA/MRSA bacterial wound infections.

In silico and In vitro Assessment of Antibacterial Activity, LPS Binding Affinity, and Toxicity of the GKY25 Peptide.

INTRODUCTION: Extensively and multi-drug resistant isolates of bacteria (MDR, XDR) have caused significant health problems and are responsible for high morbidity and mortality as well. In this critical condition, the discovery, design, or development of new antibiotics is of great concern. According to this necessity, antimicrobial peptides (AMPs) suggested as promising agents. Accordingly, this study aims to evaluate the GKY25 peptide to develop its future antibacterial applications as well as confirmation of LPS neutralization. METHODS: Predictions of 3D structure and helical wheel projection analysis of the peptide were performed by ITASSER and Heliquest servers. Binding affinity and antibacterial activity were performed using molecular docking and CAMPR4, respectively, followed by experimental binding assay as well as in vitro antibacterial assay. RESULTS: GKY25 was predicted as an alpha-helical peptide, and its helicity showed probable projection of hydrophobic and positively-charged amino acid residues. Docking studies showed binding affinity of GKY25 peptide to gram-positive and outer and inner gram-negative bacterial membranes as -5.7, -6.8, and -4 kcal/mole, respectively. CAMPR4 analysis predicted the peptide as an AMP. Experimental binding assay showed that the peptide binds LPS immediately and their interaction was observed at 274 nm. CONCLUSION: Gathering all in silico and in vitro data together, GKY25 is a good drug lead that could be examined further using clinical isolates of gram-negative bacteria in vitro.