Controlling Silver Release from Antimicrobial Surface Coatings for Biofouling Control

Silver nanoparticles (Ag NPs) are used for the functionalization of surfaces in order to achievenbsp;antimicrobial properties and control biofilm growth. The antimicrobial activity of Ag NPs is attributed to thenbsp;release of Ag + ion, which means that Ag NPs need to be soluble to achieve microbial inactivation.nbsp;However, because of this constant silver release, Ag NPs rapidly dissolve away from the surface, depleting the biocidal activity and limiting the use of Ag NPs for long term biofouling control.nbsp;In Phase I of this project, the team led by Cactus Materials Inc. demonstrated that Ag NPs can benbsp;passivated with less soluble forms of silver, such as Ag 2 S, AgBr, or AgI, to slow down silver release andnbsp;extend the lifetime of Ag NPs-based antimicrobial coatings. When different passivation chemistries werenbsp; compared, sulfidation of Ag NPs was found to have the best performance in terms of both slow silvernbsp;release and high antimicrobial performance. The improved anti-biofouling performance is attributed to thenbsp;higher retention of silver on the surface over time. A green chemistry approach was developed tonbsp;functionalize surfaces in situ using a flow through system with reagents of Toxicity Class II or lower. Thenbsp;passivated silver coatings were shown to be compatible with the current use of aqueous AgF for waternbsp;treatment and storage in the International Space Station.nbsp;Phase II of this project will evaluate how to coat surfaces comprised of different materials or havingnbsp;complex morphologies with the passivated silver coating developed in Phase I. Long term anti-biofoulingnbsp;performance will be assessed in a dormancy scenario of up to a year. Release of chemicals and particlesnbsp;during the dormancy period will be assessed to identify any risk to the water quality from long termnbsp;exposure to the passivated silver coatings. The results of this research will establish the capacity of the proposed innovation to control biofilm in a wide variety of structures for extended periods of time.nbsp;