ABSTRACT
Silver ions are antimicrobial agents with powerful action against bacteria. Applications in surface treatments, as Ag+-functionalized sol-gel coatings, are expected in the biomedical field to prevent contaminations and infections. The potential cytotoxicity of Ag+ cations toward human cells is well known though. However, few studies consider both the bactericidal activity and the biocompatibility of the Ag+-functionalized sol-gels. Here, we demonstrate that the cytotoxicity of Ag+ cations is circumvented, thanks to the ability of Ag+ cations to kill Escherichia coli (E. coli) much faster than normal human dermal fibroblasts (NHDFs). This phenomenon was investigated in the case of two silver nitrate-loaded sol-gel coatings: one with 0.5 w/w% Ag+ cations and the second with 2.5 w/w%. The maximal amount of released Ag+ ions over time (0.25 mg/L) was ten times lower than the minimal inhibition (MIC) and minimal bactericidal (MBC) concentrations (respectively, 2.5 and 16 mg/L) for E. coli and twice lower to the minimal cytotoxic concentration (0.5 mg/L) observed in NHDFs. E. coli were killed 8-18 times, respectively, faster than NHDFs by silver-loaded sol-gel coatings. This original approach, based on the kinetic control of the biological activity of Ag+ cations instead of a concentration effect, ensures the bactericidal protection while maintaining the biocompatibility of the Ag+ cation-functionalized sol-gels. This opens promising applications of silver-loaded sol-gel coatings for biomedical tools in short-term or indirect contacts with the skin.
ABSTRACT
When investigating the toxicological impact of aerosols using in vitro systems like cell cultures, it is essential to have a quantitative measurement of the chemicals that the cells are exposed to. Carbonyl compounds represent an important class of marker compounds for in vitro and in vivo exposure to different toxicological agents, including cigarette smoke (CS). A new LC-MS/MS method that quantifies eight of these analytes in aerosols trapped in phosphate-buffered saline solutions has been developed to measure exposure. During the method development phase, particular attention has been paid to the efficient derivatization of the target compounds in the trapped aerosols and to avoid the formation of poly-derivatized molecules, which could lead to inaccurate quantifications. The method has been successively validated using the accuracy profile procedure. Selectivity, detection limits, precision, and accuracy have been evaluated for Vitrocell®, Gas Vapor Phase (GVP), and Whole Smoke (WS) matrices of smoke generated by 3R4F cigarettes and aerosol generated by the Tobacco Heating System (THS) 2.2, a heat-not-burn tobacco product developed by Philip Morris International (Smith et al., 2016) [1]. Validation results confirmed that the established working ranges also allow the analysis of THS aerosols, where the concentrations of carbonyl compounds are substantially lower than those generated by 3R4F cigarettes. Moreover, data gathered on 3R4F aerosol samples trapped with DNPH in acetonitrile solutions have been compared to the quantification given by an in-house UHPLC-MS/MS and reference values from the literature.
