Nanosilver, the active component of more than 20% of the nanoproducts currently available on the market, is the most commonly used nanomaterial for commercial applications. Approximately 88% of these products have some form of antibacterial or antimicrobial activity. Silver nanoparticles exhibit physical properties that are different from both the ion and the bulk material. Because of their strong antibacterial properties, several studies have shown the potential use of silver nanoparticles in biomedical and environmental applications, such as the treatment of wounds and burns and water disinfection. While the antibacterial properties of silver nanoparticles have been extensively demonstrated, their disinfectant mechanism(s) and kinetics in the inactivation of bacteria, viruses, and protozoa have not yet been elucidated. Indeed, there have been no studies testing the ability of silver nanoparticles to deactivate protozoan pathogens like Cryptosporidium parvum and Giardia lamblia. Previous studies have not addressed the effect of environmental conditions on the antimicrobial properties of silver nanoparticles.
The researchers hypothesize that there are three possible antimicrobial processes for silver nanoparticles: (1) direct interaction of the silver particle with the cell membrane and subsequent damage to the membrane and complexation with intracellular components, (2) release of Ag+ ions and subsequent disinfection, and (3) formation of reactive oxygen species (ROS). None of these mechanisms have been conclusively confirmed, nor has the relative importance of each mechanism in the inactivation of different types of pathogenic microorganisms been elucidated. This work will synthesize silver nanoparticles with different mean particle sizes and specific surface areas and quantify their effects on pathogen disinfection mechanism and rate. Pathogens proposed for study include a virus (MS2), a bacteria (E. coli), and a protozoa (Cryptosporidium parvum). Experimental design will allow us to identify each potential mechanism individually and determine its relative contribution to the overall disinfection rate for each pathogen.
It is anticipated that this work will have broader impacts in several ways, including a summer program for high-school students, adding an environmental nanotechnology course module to an existing course, and working with the University of Rhode Island chapter of Engineering Students without Borders (ESWB) to develop a service project involving the manufacture and distribution of nanosilver particles specifically designed for use in ceramic water filters manufactured by Potters for Peace. They envision this latter effort to be a sustainable service project for the student chapter that will teach them about developing-world water problems, introduce them to silver nanotechnology, and provide funds to support their student chapter service efforts.
Nanoparticles are defined as small particles sized between 1 to 100 nanometers in at least one dimension. Currently there are more than 1,317 nanotechnology based consumer products. Compared to their counterparts in bulk states, manufactured nanomaterials have the merits of better adjustable electronic property, better tunable optical property, and higher reactivity. Among all the nanoproducts, 313 products (23%) are impregnated with nano-sized silver. Silver nanoparticles are used in a wide range of applications including pharmaceuticals, cosmetics, medical devices, foodware, clothing and water purification, among others uses, due to their antimicrobial properties. Evaluating the reactivity of silver nanoparticles is essential to support their application in water treatment technologies. Reactivity of nanoparticles is also important in order to address their environmental impacts once released in natural systems. This study evaluated the impact of water chemistry conditions impact the antimicrobial properties of silver nanoparticle in nanosuspension and attached to ceramic materials. The resutls of this study can be used to determine the performance of this nanoparticles embedded in water treatment technologies. Bacterial and virus were used as model organism to determine the change of antimicrobial performance. At the water conditions tested size seems the main parameter determining the antimicrobial effect, the small nanoparticles will have higher biocidal properties than large particles. Other possible mechanism such as production of reactive oxygen species and silver ions released seem to have a negletive effect in the overall antimicrobial properties.
