A Synergistic New Approach Toward Enhanced Antibacterial Efficacy via Antimicrobial Peptide Immobilization on a Nitric Oxide-Releasing Surface.

Despite technological advancement, nosocomial infections are prevalent due to the rise of antibiotic resistance. A combinatorial approach with multimechanistic antibacterial activity is desired for an effective antibacterial medical device surface strategy. In this study, an antimicrobial peptide, nisin, is immobilized onto biomimetic nitric oxide (NO)-releasing medical-grade silicone rubber (SR) via mussel-inspired polydopamine (PDA) as a bonding agent to reduce the risk of infection. Immobilization of nisin on NO-releasing SR (SR-SNAP-Nisin) and the surface characteristics were characterized by Fourier transform infrared spectroscopy and scanning electron microscopy with energy-dispersive X-ray spectroscopy and contact angle measurements. The NO release profile (7 days) and diffusion of SNAP from SR-SNAP-Nisin were quantified using chemiluminescence-based nitric oxide analyzers and UV-vis spectroscopy, respectively. Nisin quantification showed a greater affinity of nisin immobilization toward SNAP-doped SR. Matrix-assisted laser desorption/ionization mass spectrometry analysis on surface nisin leaching for 120 h under physiological conditions demonstrated the stability of nisin immobilization on PDA coatings. SR-SNAP-Nisin shows versatile in vitro anti-infection efficacy against Gram-negative Escherichia coli and Gram-positive Staphylococcus aureus in the planktonic and adhered states. Furthermore, the combination of NO and nisin has a superior ability to impair biofilm formation on polymer surfaces. SR-SNAP-Nisin leachates did not elicit cytotoxicity toward mouse fibroblast cells and human umbilical vein endothelial cells, indicating the biocompatibility of the material in vitro. The preventative and therapeutic potential of SR-SNAP-Nisin dictated by two bioactive agents may offer a promising antibacterial surface strategy.

Highly hydrophobic polytetrafluoroethylene particle immobilization via polydopamine anchor layer on nitric oxide releasing polymer for biomedical applications.

Biomedical surface-associated infections and thrombus formation are two major clinical issues that challenge patient safety and patient the fate of a medical device in the body . Single platform multifunctional surfaces are critical to address both these indwelling medical device-related problems. In this work, bio-inspired approaches are employed to fabricate a polymer composite with a versatile surface that can reduce bacterial infections and platelet adhesion in vitro. In the first bio-inspired approach, the functionality of nitric oxide (NO) produced by endothelial cell lining of blood vessels is mimicked through incorporation of S-nitroso-N-acetylpenicillamine (SNAP) within a CarboSil-2080A™ (CarboSil) polymer composite matrix. The second approach involves utilizing mussel adhesive chemistry, via polydopamine (PDA) to immobilize polytetrafluoroethylene (PTFE) particles on the polymer composite surface. The PTFE coating facilitates a decrease in wettability by making the polymer composite surface highly hydrophobic (contact angle ca. 120°). The surface of the fabricated polymer composite , CarboSil SNAP-PTFE, had a cobblestone-like structured appearance as characterized through scanning electron microscopy (SEM). Water contact angle (WCA) and surface tension measurements indicated no significant coating losses after 24 h under physiological conditions. NO surface flux was measured and analyzed for 5 days using a chemiluminescence-based nitric oxide analyzer and was found to be within the physiological range. CarboSil SNAP-PTFE reduced adhered bacteria (99.3 ± 0.5% for Gram-positive S. aureus and 99.1 ± 0.4% for Gram-negative E. coli) in a 24 h in vitro study. SEM analysis showed the absence of biofilm formation on CarboSil SNAP-PTFE polymer composites, while present on CarboSil in 24 h exposure to S. aureus. Platelet adhesion was reduced by 83.3 ± 4.5%. Overall, the results of this study suggest that a combination of NO-releasing CarboSil with PTFE coating can drastically reduce infection and platelet adhesion.

Characterization of a nitric oxide (NO) donor molecule and cerium oxide nanoparticle (CNP) interactions and their synergistic antimicrobial potential for biomedical applications.

HYPOTHESIS: Broad-spectrum antimicrobials are needed to mitigate the complicated nature of antibiotic-resistant infections. It is imperative to formulate new antimicrobials by combining agents with different mechanisms and broader microbial targets. A combined antimicrobial solution could be a highly critical step towards developing a strategy to prevent polymicrobial infections. Herein, we have investigated the interaction and antimicrobial potential of a solution that contains cerium oxide nanoparticles (CNP) and a nitric oxide (NO) donor, S-nitroso-N-acetylpenicillamine (SNAP). It is hypothesized that these two agents induce synergistic effects and would provide broad antimicrobial effects since CNP is known to be an effective antifungal agent while NO released by SNAP is known to be a potent bactericidal agent. EXPERIMENTS: Different concentrations of SNAP and CNP were combined in a solution and tested for colloidal stability, NO release, mammalian cell cytotoxicity, and antimicrobial efficacy against Staphylococcus aureus, Escherichia coli, and Candida albicans, accounting for Gram-positive bacteria, Gram-negative bacteria, and fungi, respectively. FINDINGS: SNAP and CNP combined in equimolar solution of 3 mM were found to be highly virulent for all microbes tested compared to higher amounts of the treatments required individually. These results hold a promising outlook toward the development of broad-spectrum antimicrobial coatings and films with the potential to prevent polymicrobial infections and further enhance biomedical device usage and applications.