Silver dopped sol-gel hybrid coatings for antibacterial surfaces

S.A. PELLICE; J. BALLARRE; A.L. CAVALIERI; S. CERÉ

Porto de Galinhas-PE, Brazil

Conferencia; XV International Sol-Gel Conference; 2009

International Sol-Gel Society

Materials enriched with noble metal ions, such as of silver, cobalt or copper, are of great interest in the field of hygienic and healthiness products through its action against fungus and bacteria. Although a large number of commercial products are chemically active against microorganisms, they are usually limited to fabrics for medical bandages and sportswear in order to avoid, respectively, infections and odor. Although many of those products are based on the biocide properties of silver nanoparticles, it is well known Ag+ has an effective action against bacteria life inhibiting their DNA replication process, increasing the permeability of the cytoplasmic membrane and inhibiting the respiratory enzymes causing asphyxia of the bacteria. Taking this feature in account, reduction of silver ions must be strongly avoided in order to maximize the biocide character of the functional coating. In this work, the development of silver doped hybrid organic-inorganic sol-gel coatings is focused. A hybrid organic-inorganic matrix was obtained through the hydrolytic condensation of tetraethoxysilane (TEOS) and methyl-triethoxysilane (MTES). Silver nitrate (AgNO3) was added as supplier of Ag+ and, which was complexed with pyridine (C5H5N). Silica nanoparticles were added in different proportions in order to increase the coating density and control the silver diffusion through the hybrid matrix. UV-visible spectroscopy of precursor sols evidenced the chemical stability of silver upon more than two weeks in storing at 4 ºC. Colorless dip-coated films were obtained on glass slides at a withdrawal speed of 25 cm/min and thermal treated at 450 ºC during 30 min in air atmosphere. Lixiviation tests were performed along 30 days at 30 ºC in immersion in deionized water at a ratio of 1 cm2/ml. The ratio of silver releasing from coatings was analyzed by Atomic-Absorption Spectroscopy (AAS) and X-Ray Fluorescence (XRF). Contact angle of inoculated PBS on the sample surface and adhesion of bacteria were analyzed. Samples inoculated 2 h at 25 ºC in PBS solution were observed by fluorescence microscopy. The biocide potential was determined by the agar diffusion test on obtained coatings. After incubation period of 24 h the inhibition halo developed around samples in Petri dishes was measured.