Reduced cytotoxicity of silver ions to mammalian cells at high concentration due to the formation of silver chloride

Abstract

Silver-containing antimicrobial agents are used in various medical products. However, their toxicity to mammalian cells has not been sufficiently evaluated. Numerous studies have unveiled evidence of significant antimicrobial properties associated with Ag ions. In cell culture media or human body fluids, the free Ag(+) has rich opportunities to complex with Cl(-). Surprisingly, studies on the toxicity of solid form AgCl(s) to mammalian cells are quite limited. In this study, we evaluated the cytotoxicity of Ag ions and silver chloride colloids on red blood cells and human mesenchymal stem cells (hMSCs). The adverse effects of silver chloride on red blood cells and hMSC were viewed by SEM and LIVE/DEAD viability staining, respectively. Among different tested chemical forms of silver, AgCl was identified to be the least cytotoxic. Moreover, a decline in the cytotoxicity of AgCl at significantly high concentrations was observed. We attributed the reduced cytotoxicity to aggregated AgCl which limited the bioavailability of free Ag(+) ions.

Silver coordination compounds: A new horizon in medicine

“…As a matter of fact, bacterial resistance to silver is very rare and often transitory [6,7]; there is a single report in the literature describing a silver-resistant strain of P. stutzeri isolated in a silver mine [8]. Silver toxicity for bacterial cells has long been recognized and documented [9], while for humans its toxicity seems to be quite low: this metal has no biological role but has been found in human tissues as a consequence of bio-accumulation over the lifespan, with an average concentration of a few micrograms per kilo of wet tissue [10][11][12], indicating that the body can tolerate the presence of silver in low doses without any toxic effects, probably through the formation of AgCl [13]. Thus, low toxicity is one of silver's greatest advantages over other medicinally relevant metals and the antimicrobial power of its ionic compounds can be exploited in medical practice with reasonable safety.…”

The predominant species of ionic silver in biological media is colloidally dispersed nanoparticulate silver chloride

“…These will react with the silver ions in one or the other way, reducing the concentration of dissolved silver ions, as pointed out by a number of authors, [5][6][7] and also for engineered silver nanoparticles aer their release into the environment. [8][9][10][11] Consequently, there have been attempts to study the biological effect of silver chloride [5][6][7]12 which is the most likely precipitation product in the absence of sulphide. 2,13 However, in all these studies, silver chloride was prepared as precipitated solid, i.e.…”

Biosynthesis, Characterization of Some Combined Nanoparticles, and Its Biocide Potency against a Broad Spectrum of Pathogens

“…Journal of Nanomaterials Na + , Ca 2+ , and Mg 2+ could be adsorbed on negatively charged NPs which neutralize their surface forming large flocculates and thus losing monodispersity. Consequently, the effective dose that was designed for bacterial eradication required to be adjusted according to the type of the samples and their content [73].…”