Showing papers by "Debarun Dutta published in 2020"

Mechanism of Action of Surface Immobilized Antimicrobial Peptides Against Pseudomonas aeruginosa.

Abstract: Bacterial colonization and biofilm development on medical devices can lead to infection. Antimicrobial peptide-coated surfaces may prevent such infections. Melimine and Mel4 are chimeric cationic peptides showing broad-spectrum antimicrobial activity once attached to biomaterials and are highly biocompatible in animal models and have been tested in Phase I and II/III human clinical trials. These peptides were covalently attached to glass using an azidobenzoic acid linker. Peptide attachment was confirmed using X-ray photoelectron spectroscopy and amino acid analysis. Mel4 when bound to glass was able to adopt a more ordered structure in the presence of bacterial membrane mimetic lipids. The ability of surface bound peptides to neutralize endotoxin was measured along with their interactions with the bacterial cytoplasmic membrane which were analyzed using DiSC(3)-5 and Sytox green, Syto-9, and PI dyes with fluorescence microscopy. Leakage of ATP and nucleic acids from cells were determined by analyzing the surrounding fluid. Attachment of the peptides resulted in increases in the percentage of nitrogen by 3.0% and 2.4%, and amino acid concentrations to 0.237 nmole and 0.298 nmole per coverslip on melimine and Mel4 coated surfaces, respectively. The immobilized peptides bound lipopolysaccharide and disrupted the cytoplasmic membrane potential of Pseudomonas aeruginosa within 15 min. Membrane depolarization was associated with a reduction in bacterial viability by 82% and 63% for coatings melimine and Mel4, respectively (p < 0.001). Disruption of membrane potential was followed by leakage of ATP from melimine (1.5 ± 0.4 nM) or Mel4 (1.3 ± 0.2 nM) coated surfaces compared to uncoated glass after 2 h (p < 0.001). Sytox green influx started after 3 h incubation with either peptide. Melimine coatings yielded 59% and Mel4 gave 36% PI stained cells after 4 h. Release of the larger molecules (DNA/RNA) commenced after 4 h for melimine (1.8 ± 0.9 times more than control; p = 0.008) and after 6 h with Mel4 (2.1 ± 0.2 times more than control; p < 0.001). The mechanism of action of surface bound melimine and Mel4 was similar to that of the peptides in solution, however, their immobilization resulted in much slower (approximately 30 times) kinetics.

Activity of Antimicrobial Peptides and Ciprofloxacin against Pseudomonas aeruginosa Biofilms.

Abstract: Pseudomonas aeruginosa is increasingly resistant to conventional antibiotics, which can be compounded by the formation of biofilms on surfaces conferring additional resistance. P. aeruginosa was grown in sub-inhibitory concentrations of the antimicrobial peptides (AMPs) melimine and Mel4 or ciprofloxacin for 30 consecutive days to induce the development of resistance. Antibiofilm effect of AMPs and ciprofloxacin was evaluated using crystal violet and live/dead staining with confocal microscopy. Effect on the cell membrane of biofilm cells was evaluated using DiSC(3)-5 dye and release of intracellular ATP and DNA/RNA. The minimum inhibitory concentration (MIC) of ciprofloxacin increased 64-fold after 30 passages, but did not increase for melimine or Mel4. Ciprofloxacin could not inhibit biofilm formation of resistant cells at 4× MIC, but both AMPs reduced biofilms by >75% at 1× MIC. At 1× MIC, only the combination of either AMP with ciprofloxacin was able to significantly disrupt pre-formed biofilms (≥61%; p < 0.001). Only AMPs depolarized the cell membranes of biofilm cells at 1× MIC. At 1× MIC either AMP with ciprofloxacin released a significant amount of ATP (p < 0.04), but did not release DNA/RNA. AMPs do not easily induce resistance in P. aeruginosa and can be used in combination with ciprofloxacin to treat biofilm.

The Development of an Antimicrobial Contact Lens - From the Laboratory to the Clinic.

Abstract: Contact lens wear is generally safe and provides excellent vision. However, contact lens wear is often associated with the risk of developing ocular surface infection and inflammation, and in severe cases, the infection can result in loss of vision. Antimicrobial peptide-coated contact lenses have been made to help reduce the incidence of infection and inflammation. This paper reviews the research progress from conception, through the laboratory and preclinical tests to the latest information on clinical testing of an antimicrobial contact lens. We provide insights into the pathways followed and pitfalls that have been encountered. The journey has not always been linear or smooth, but has resulted in some of the first published clinical testing of antimicrobial peptide-coated contact lenses in humans. We hope this may help lead to the development and commercialisation of antimicrobial contact lenses in the future.

Active loading graphite/hydroxyapatite into the stable hydroxyethyl cellulose scaffold nanofibers for artificial cornea application

Abstract: The design of biocompatible porous scaffolds that encourage cell adhesion for corneal tissue engineering applications continues to be challenging. In addition to porous hydrogels, nanofibers that can simulate the extracellular matrix structure for cell adhesion would be beneficial. Graphite and nano-hydroxyapatite (nHA) are two bioactive materials that have been used to improve cell adhesion in scaffolds for corneal tissue engineering. In this study, nanofibers were fabricated from hydroxyethyl cellulose and polyvinyl alcohol (PVA) and cross-linked by glutaraldehyde bound to graphite and nano-hydroxyapatite. This scaffold surrounded a transparent hydrogel core from PVA that was cross-linked by freeze-thawing cycles. The chemical and mechanical evaluations demonstrated that nanofibers met the requirements as a scaffold for corneal tissue engineering. The results showed that when the concentration of nHA was approximately 1.66 wt%, the morphology of human epithelial cells did not change, and clot formation occurred around the scaffold during the 1-week in vivo implantation.

Interaction of the surface bound antimicrobial peptides melimine and Mel4 with Staphylococcus aureus.

Abstract: Melimine and Mel4 are cationic antimicrobial peptides which can resist biofilm development once bound to biomaterials. The aim of the current study was to determine the mode of action of bound meli...

Poly-ε-Lysine or Mel4 Antimicrobial Surface Modification on a Novel Peptide Hydrogel Bandage Contact Lens

Abstract: Microbial keratitis (MK) is a serious issue in many countries and is often caused by contact lens wear. Antimicrobial peptides (AMPs) are a potentially useful tool for creating antimicrobial surfaces in light of increasing antibiotic resistance. Poly--lysine (pK) is an AMP that has been used extensively as a food preservative and Mel4 has recently been synthesised and studied as an antimicrobial coating for contact lenses. A hydrogel synthesised of pK cross-linked with biscarboxylic acids provides a potential lens material which has many surface free amines, that can be subsequently used to attached additional AMPs, creating an antimicrobial lens. The aim of this study was to investigate peK hydrogels against a clinical strain of Pseudomonas aeruginosa for preventing or treating MK. Covalent attachment of AMPs was investigated and confirmed by fluorescently tagged peptides. Bound pK effectively reduced the number of adherent P. aeruginosa in vitro (>3 log). In ex vivo studies positive antimicrobial activity was observed on bare pK hydrogels and those with additionally bound pK or Mel4; lenses allowed the maintenance of the corneal epithelium. A peK hydrogel contact lens with additional AMPs could be a therapeutic tool to reduce the incidence of MK.

Prevalence and seasonal variation of Acanthamoeba in domestic tap water in greater Sydney, Australia

Abstract: This study examined the prevalence of free‐living Acanthamoeba in domestic tap water in the greater Sydney region, Australia, and determined any seasonal variation in prevalence.Fifty‐four particip...