Rapid screening of the antimicrobial efficacy of Ag zeolites

Abstract

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. 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.

Synthesis of FAU-Type Zeolite Membranes with Antimicrobial Activity

“…The substitution of Si atoms by Al atoms in the zeolite framework creates negative charge that should be compensated by cations (the most common compensating cations are Na + ). These cations can be easily exchanged by silver, copper, or zinc cations to confer to zeolites antibacterial, antiviral, and antifungal activities [ 3 , 4 , 5 , 6 , 7 , 8 , 9 ]. Silver-exchanged zeolites have antibacterial and antifungal properties against a broad spectrum of microscopic bacteria and fungi ( Escherichia Coli , Pseudomonas aeruginosa , Bacilus cereus , Staphylococcus aureus , Candida albicans , Candida glabata , Aspergillus niger and Penicillium vinaceum , etc.).…”

Synthesis of Antimicrobial Films Based on Low-Density Polyethylene (LDPE) and Zeolite A Containing Silver

“…The MIC of zeolite X was 0.1 mg/mL for the inhibition of E. coli. Beta zeolite was effective from 0.05 to 0.5 mg/mL [9]. Other authors reported the loading of 5.8% (w/w) silver in zeolite X, finding the excellent inhibition of Gram-negative and Gram-positive microorganisms over the course of 24 h, with no growth occurring within the first hour of analysis [34].…”

“…Zeolites are among the materials used as carrier supports where silver can be incorporated. They display specific attractive characteristics, such as rigid structures, good thermal, mechanical and chemical stability, high specific areas, and microporous systems that allow the controlled release of silver [9]. Zeolite A, modified with Ag + by ion exchange, was reported to exhibit good antibacterial properties against the growth of Escherichia coli and Staphylococcus aureus [3].…”

Microporous Frameworks as Promising Platforms for Antibacterial Strategies Against Oral Diseases

“…After adding 20 mg of silver-loaded green β-zeolite into culture medium (10 mL, 10 8 CFU/mL) for 1 h, no colonies of E. coli were found by agar plate counting. Besides, other types of zeolites, such as zeolite X and EMT zeolite, were also reported to exchange with Ag + for antibacterial application (Dong et al, 2014;Tosheva et al, 2017). In addition to Ag + , other metal ions including zinc ions, copper ions, etc., were also exchanged into different types of zeolites to exert antibacterial properties.…”