Different cytotoxicity responses to antimicrobial nanosilver coatings when comparing extract‐based and direct‐contact assays

Abstract

This study was performed to understand how the choice of cytotoxicity assay format affects the observed biocompatibility of nanosilver (nAg). nAg coatings are physical coatings containing silver (Ag) that have feature sizes of 100 nm or less, often in the form of nanoparticles or grains. They are used on medical devices to prevent infection, but in spite of this intended benefit, observations of potential cytotoxicity from nAg have been reported in numerous published studies. For medical device regulation, cytotoxicity testing is part of a biocompatibility evaluation, in which specific test methods are chosen based on the technological characteristics and intended use of a device. For this study, nAg-coated tissue culture polystyrene surfaces were prepared using magnetron sputter coating, resulting in nAg films of 0.2 to 311 µg cm(-2) Ag. These coatings exhibited nanometer-scale morphologies and demonstrated a > 4log10 reduction in Escherichia coli viability. It was observed that extracts of nAg caused no cytotoxicity to L929 mouse fibroblasts, but cells cultured directly on nAg coatings (direct-contact assay format) showed a dose-dependent reduction in viability by up to 100% (P < 0.001). Results using inductively coupled plasma mass spectrometry to measure Ag release suggested that extracts of nAg are not toxic because the dissolved Ag in those samples becomes less cytotoxic over time, probably owing to the reaction with cell culture media and serum (six-fold cytotoxicity reductions observed over a 24-h period). These findings highlight the potential value of direct-contact cytotoxicity testing for nAg in predicting biological interactions with cells or tissue in vivo.

Porous magnesium-based scaffolds for tissue engineering

“…Although direct contact cell cytotoxicity methods may introduce additional information, extract based assays are the most common ones [98]. These cytotoxicity testing standards are developed for non-degradable materials, thus applying them on the degradable magnesium scaffolds may not be suitable.…”

Silver Nanocoating Technology in the Prevention of Prosthetic Joint Infection

“…and its intended use in a specific tissue. In addition, a level of cytotoxicity can be dependent on the assay technique and a difference between extraction-based and direct contact assays has been found [280]. …”

Current Options and Emerging Biomaterials for Periprosthetic Joint Infection

“…Silver nanoparticles are one of the most common non-antibiotic antibacterial coatings [64–76]. In these settings, silver ions leach from the coating, diffuse into bacterial cells, and damage enzymes in the cell [66]. Specifically, several nanosilver formulations have been developed in which the silver is slowly solubilized over an extended period of time, preventing excessive local concentrations [66].…”