Rapid screening of the antimicrobial efficacy of Ag zeolites

• Published in: Colloids and surfaces, B, Biointerfaces Vol. 157; pp. 254 - 260
• Main Authors: Tosheva, L., Belkhair, S., Gackowski, M., Malic, S., Al-Shanti, N., Verran, J.
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 01-09-2017
• Subjects: Anti-Bacterial Agents - adverse effects; Anti-Bacterial Agents - chemistry; Anti-Bacterial Agents - pharmacology; Antimicrobial; Candida albicans - drug effects; Cell Line; Cell Survival - drug effects; Crystal size; Cytotoxicity; Humans; Killing efficacy; Leukocytes, Mononuclear - drug effects; Microbial Sensitivity Tests; Silver - chemistry; Silver zeolites; Staphylococcus aureus - drug effects; Zeolites - adverse effects; Zeolites - chemistry; Zeolites - pharmacology; Antimicrobial; Crystal size; Killing efficacy; Cytotoxicity; Silver zeolites
• ISSN: 0927-7765; 1873-4367
• DOI: 10.1016/j.colsurfb.2017.06.001

[Display omitted]
•Rapid screening method used to study the antimicrobial efficacy of Ag zeolites.•Larger zeolite crystals show enhanced killing efficacy.•Zeolite beta more efficient than zeolite X despite its lower Ag content.•Cytotoxicity results for Ag zeolites cannot be generalized.
A semi-quantitative screening method was used to compare the killing efficacy of Ag zeolites against bacteria and yeast as a function of the zeolite type, crystal size and concentration. The method, which substantially reduced labor, consumables and waste and provided an excellent preliminary screen, was further validated by quantitative plate count experiments. Two pairs of zeolite X and zeolite beta with different sizes (ca. 200nm and 2μm for zeolite X and ca. 250 and 500nm for zeolite beta) were tested against Escherichia coli (E. coli) and Candida albicans (C. albicans) at concentrations in the range 0.05–0.5mgml−1. Reduction of the zeolite crystal size resulted in a decrease in the killing efficacy against both microorganisms. The semi-quantitative tests allowed convenient optimization of the zeolite concentrations to achieve targeted killing times. Zeolite beta samples showed higher activity compared to zeolite X despite their lower Ag content, which was attributed to the higher concentration of silver released from zeolite beta samples. Cytotoxicity measurements using peripheral blood mononuclear cells (PBMCs) indicated that Ag zeolite X was more toxic than Ag zeolite beta. However, the trends for the dependence of cytotoxicity on zeolite crystal size at different zeolite concentrations were different for the two zeolites and no general conclusions about zeolite cytotoxicity could be drawn from these experiments. This result indicates a complex relationship, requiring the necessity for individual cytotoxicity measurements for all antimicrobial applications based on the use of zeolites.