Antibacterial performance of hybrid nanocomposite coatings containing clay and silver nanoparticles

The performance of biocide-based coatings for health care applications, using the drug delivery method, depends primarily on the diffusive properties of storage material. When the active component is ionic silver, supplied from silver nanoparticles, an additional dissolution step must occur in the bulk of the storage material. This article presents the silver release behavior of organic-inorganic sol-gel hybrid coatings and the effect of clay-nanoparticle composite, added in the sol-type formulation. Hybrid coatings were synthesized from the hydrolytic condensation of (3-glycidoxypropyl)-trimethoxysilane (GPTMS) and tetraethoxysilane in acidic media. Clay nanoparticles, previously silanized with GPTMS, and silver nitrate were used as additives in sol-gel formulations, alternatively. Coatings were deposited on microscope glass slides by the dip-coating process at a constant withdrawal rate and densified at 150 °C. Through small angle X-ray scattering from a synchrotronic source, and transmission electron microscopy, the structure of hybrid matrix, silver nanoparticles morphology and the storability behavior of silver nanoparticles under leaching conditions was analyzed. Silver releasing process was analyzed by following the evolution of silver nanoparticles remaining in the coatings, by UV–visible spectroscopy, and the increase of silver ions in the liquid medium, using inductively coupled plasma with optical emission spectroscopy. Microbiological studies showed that the lixiviated silver exhibited inhibitory properties against E. coli in LB broth. The clay nanoparticles worked as a stabilizing agent avoiding the agglomeration of silver both on the sols and on the surface of the thermally densified coatings