Microbots Decorated with Silver Nanoparticles Kill Bacteria in Aqueous Media

Abstract

KEYWORDS Silver nanoparticles, water propulsion, bacteria remediation, biocompatibility and environmental application.Water contamination is one of the most persistent problems in public health. The resistance of some pathogens to conventional disinfectants can require the combination of multiple disinfectants or increased their dosages which may produce harmful by-products. Here, we describe an efficient disinfection and removal method of Escherichia coli (E. coli) from contaminated water by using water self-propelled Janus microbots decorated with silver nanoparticles (AgNPs). The spherical Janus microbot's structure consists of a magnesium (Mg) microparticle as a template that also functions as propulsion source by producing hydrogen bubbles while in contact with water, an inner iron (Fe) magnetic layer for their remote guidance and collection, and an outer AgNP coated gold (Au) layer for bacteria adhesion and bactericidal properties. The active motion of microbots improves the chances of the contact of microbot surface decorated AgNPs with the bacteria, which provokes the selective Ag + release in bacteria cytoplasma, and their self-propulsion increase diffusion of the released Ag + ions. In addition, the AgNPs coated Au metal cap of the microbots has dual capabilities capturing bacteria and then killing them. Thus, we have demonstrated that AgNPs coated Janus microbots are capable of efficiently killing more than 80% of E. coli compared to colloidal AgNPs that killed less than 35% of E. coli in 15 minutes in contaminated water solutions. After bacteria capture and extermination, the magnetic properties of the cap allow microbots to be collected from water with the captured dead bacteria, leaving water with no contaminants. The presented biocompatible Janus microbots offers an encouraging method for rapid disinfection of water.

Self‐Propelled Micro/Nanomotors for Sensing and Environmental Remediation

“…Removal of waterborne pathogens is a critical challenge led the developments of microscopic level tools for efficient water treatments. Micro/nanomotors have been developed for degradation of chemical pollutions and recently they have been used for removal of microbial pathogens . The abilities to motor around water samples, collecting microbial pathogens, degrading them, and recovering from water make them a promising candidates for future of water and waste‐water treatments ( Table 1 ).…”

“…Compared to static chitosan‐coated microparticles, these micromotors showed significant antibacterial activity (e.g., 27‐fold enhancement), with a 96% killing efficiency in 10 min . In another example, Vilela et al developed a self‐propelled Janus microbots which decorated by Ag NPs for disinfection and removal of E. coli from water . The spherical Janus microbots composed of a) Mg particles as a template and propulsion in water, b) an internal Fe magnetic layer for remote controlling and final collection, and c) external Ag NP coated gold layer for antibacterial activities (Figure b).…”

“…b) AgNP‐coated Janus microbots. Reproduced with permission . Copyright 2017, American Chemical Society.…”

Fabrication of Self‐Propelled Micro‐ and Nanomotors Based on Janus Structures

“…[12] The Mg microparticles weres pread in am onolayer on the glass slide. [15] Janus structures based on spherical Mgm icroparticles were achieved by depositing metal caps of Fe and Au. [12] This kind of self-destroyed micromotor exhibited efficient motion and controlled degradation in biological fluid.…”

Screening Small Metabolites from Cells as Multifunctional Coatings Simultaneously Improves Nanomaterial Biocompatibility and Functionality

“…The uncontrolled release of Ag + from the oxidized surface of nAg (Ag 2 O+H 2 O→2Ag + +2OH − ) exerts hazardous effects on organisms and limits the widespread use of nAg in healthcare 19, 20, 21, 22, 23, 24, 25. To hinder ionic release and prevent the access of oxygen to the nAg surface, surface coatings are expected to be a useful tool 26, 27.…”