Adhesion of E. coli to silver- or copper-coated porous clay ceramic surfaces

Abstract

Porous ceramic water filters (CWFs), produced by sintering a mixture of clay and a combustible material (such as woodchips), are often used in point-of-use water filtration systems that occlude microbes by size exclusion. They are also coated with colloidal silver, which serves as a microbial disinfectant. However, the adhesion of microbes to porous clay surfaces and colloidal silver coated clay surfaces has not been studied. This paper presents the results of atomic force microscopy (AFM) measurements of the adhesion force between Escherichia coli bacteria, colloidal silver, and porous clay-based ceramic surfaces. The adhesion of silver and copper nanoparticles is also studied in control experiments on these alternative disinfectant materials. The adhesive force between the wide range of possible bi-materials was measured using pull-off measurements during force microscopy. These were combined with measurements of AFM tip radii/substrate roughness that were incorporated into adhesion models to obtain the adhesion energies for the pair wise interaction. Of the three antimicrobial metals studied, the colloidal silver had the highest affinity for porous ceramic surface (125 ± 32 nN and ∼0.29 J/m2) while the silver nanoparticles had the highest affinity for E. coli bacteria (133 ± 21 nN and ∼0.39 J/m2). The implications of the results are then discussed for the design of ceramic water filter that can purify water by adsorption and size exclusion.

One-step, solvent-free mechanosynthesis of silver nanoparticle-infused lignin composites for use as highly active multidrug resistant antibacterial filters

“…The resulting material have activity similar to previously reported antibacterial silver nanomaterials, while maintaining a low level of leaching. [15][16][17][18] This result is consistent with our previous study on other noble metals, including Au. 37 The accessibility of kra lignin makes it particularly suitable for this application.…”

Mechanisms and efficacy of disinfection in ceramic water filters: A critical review

“…When taken together, all of these results, as well as the results presented in Table 5, highlight a trend where much more silver is lost when filters are painted with, or submerged in, a silver solution, than when co-fired. These results align with the findings from Yakub and Soboyejo (2012), who enumerated the attachment force between silver and CWF material to be only 125 ± 32 nN after painting/submerging, which was attributed to van der Waals forces (Yakub & Soboyejo, 2012). As such, the interfacial energy between the materials is low, which is why co-firing has exhibited more consistent release and less vulnerability to the impacts of water chemistry (Ren & Smith, 2013;Lyon-Marion et al, 2018).…”

“…In terms of ionic silver, studies by Yamanaka et al (2005) and others suggested that a monovalent cation like Ag þ attaches to the negatively charged cell walls of the bacterium by electrostatic attraction, which leads to cell death as per the mechanisms explained in Section 3.2.1.2 (Dror-Ehre et al, 2009;Stoimenov et al, 2002;Yamanaka et al, 2005). Other researchers, however, have reported negatively charged Ag-NPs attachment to the cell walls, suggesting electrostatic attraction is not necessarily the governing mechanism (Morones et al, 2005;Sondi & Salopek-Sondi, 2004;Yakub & Soboyejo, 2012). Rather, attachment of this nature is generally attributed to the bonding between silver nanoparticles and the sulfuric thiol groups on the cell membrane, which subsequently leads to toxicity effects or ROS generation and eventual cell death (Matsumura et al, 2003;Shuang et al, 2014).…”

Ceramic Water Filters: A Point-of-Use Water Treatment Technology to Remove Bacteria from Drinking Water in Longhai City, Fujian Province, China

“…In addition to filtration, the development of a biofilm on the surface of the CWF aids in the removal of pathogens. Silver nitrate and/or silver nanoparticles are also utilized as disinfectants in some cases (Oyanedel-Craver and Smith, 2008;Vinka, et al, 2008;Yakub and Soboyejo, 2012;Rayner et al, 2013). Hence, the combination of filtration, disinfection and biofilm development result in significant removal of microorganisms from source water during CWF operation.…”