(245d) Nanoparticles for Hydrophilic and Antimicrobial Surface Coatings

Hydrophilic and antimicrobial surfaces are highly desirable for use in applications where surface biofouling (or infection) limit performance such as biomedical implants, dental surfaces, water treatment membranes, and water quality sensors. Biofouling occurs through a cascade of events including at least four distinct stages ? (1) reversible attachment, (2) irreversible attachment, (3) maturation, and (4) detachment ? leading to biofilm formation. It is widely believed that physicochemical interactions govern primary adhesion whereas biological factors contribute more to latter stages of biofilm formation. Physicochemcal interactions derive from hydrodynamic forces (convection and diffusion) and interfacial forces (van der Waals, electrostatic double layer, and Lewis acid-base). Biological factors include extracellular polysaccharide production and irreversible attachment, substrate consumption (water chemistry, mass transfer, nutritional environment), and community interactions (cell-cell signaling, cell translocation, etc.). Hence, an ideal method of mitigating biofouling involves creation of materials that minimize primary adhesion, EPS production, and cell proliferation, thereby addressing the first three fundamental stages of biofilm formation.

Hydrophilic and antimicrobial nanoparticles have been developed to minimize adhesion and growth of bacteria onto aquatic substrata. Inorganic microporous nanoparticles were synthesized by microwave heating and characterized by dynamic light scattering, particle micro-electrophoresis, energy dispersive X-ray spectroscopy, X-ray diffraction, and scanning electron microscopy. The nanoparticles are densely negatively charged and exhibit excellent hydrophilicity (water instantly wets the particles when cast in a film). After modification with intrinsically biocidal elements, both as-synthesized and modified nanoparticles were deposited on a polymeric membrane and viability of bacteria subsequently deposited on the modified-membrane surfaces was verified by staining with commercial dye solution followed by observation with a fluorescence microscope. Unmodified nanoparticles reduced primary adhesion simply by increasing surface hydrophilicity and charge, whereas modified nanoparticles reduced primary adhesion and inactivated a significant fraction of deposited cells. The properties of nanoparticles may be very attractive in forming various hydrophilic and antimicrobial thin film coatings.