Titanium dioxide nanoparticles (TiO 2 Np) exhibiting properties of photocatalyst under ultraviolet light (UV) exposition related with destruction of some hazardous organic moieties. To enhance the antibacterial characteristics of this material in our works, we developed a new method of TiO 2 Np doping with silver nanoparticles (Ag 0 Np), whose biocidal properties are well defined. The obtained products, Ag 0 Np/TiO 2 Np, in the form of suspensions and powders were characterized from chemical, physical and antimicrobial activity point of view. In addition, a mechanism of Ag + ions reduction reaction to Ag 0 Np has been proposed. The developed method of the Ag 0 Np/TiO 2 Np synthesis consists of the in situ chemical deposition of the Ag 0 Np on the dispersed TiO 2 Np in the form of anatase, using aqueous solutions of poly(acrylic acid sodium salt) (PAS) and NaBH 4. The Ag 0 Np synthesis was carried out both in the presence and absence of TiO 2 Np. The chemical composition of Ag 0 Np/TiO 2 Np was assessed by atomic absorption spectrometrical method (AAS). The physical properties were evaluated as follows: crystallite structure and dimensions of nanopowders by X-ray diffraction method (XRD), UV-Vis absorption of colloidal suspensions and UV-Vis reflectance of nanopowders by spectrophotometrical method, grain size distribution of nanoparticles by dynamic light scattering method (DLS), stability of colloidal suspensions by zeta potential measurements, forms and shapes of Ag 0 Np and Ag 0 Np/TiO 2 Np by transmission electronic microscopy (TEM) and scanning electronic microscopy (SEM) respectively. The antimicrobial activity was tested by standard methods against some broad spectra of fungi and bacteria. In suspensions, the concentration of TiO 2 Np was 1 wt. % and the concentration of Ag 0 Np varied in the range of 0.005…0.15 wt. %. The Ag 0 Np suspensions and Ag 0 Np/TiO 2 Np suspensions were stable from the physical and chemical point of view. The physical characterization test results were in accordance, proving the achievement of colloidal solutions containing Ag 0 Np and TiO 2 Np spherical nanocrystallite with average diameters of 4.1 nm and 7.8 nm, respectively. The results of the biological tests showed the high fungistatic and antibacterial activities of both products in form of colloidal suspensions and powders. The developed "one pot method" is efficient, ecological and easy to be scaled-up. The obtained products have biological activity but it depends on the nature of the tested germs, lowering in the series: Gram negative bacteria, Gram positive bacteria and fungi. Also, a synergistic action was proved at destroying of Trichoderma viride fungus, which was not obtained either for Ag 0 Np or for TiO 2 Np, independently.

The aim of this study was focused on the bactericide test of Silver nanoparticles with an average diameter of 6 nm, over Escherichia coli, Staphylococcus aureus and Candida albicans and the treatment of a dermatosis of unknown etiology with a poly(hydroxy urethane-acrylate) gel (PHU) with a concentration of approximately 10 ppm Ag-NPs and a ratio-NHCOO-:RGD (Arg-Gly-Asp) on the macromolecular chain of 200:1. The gel was obtained at the room temperature in sterile conditions, in a reactor with stirring facilities and a cushion of nitrogen purified by traces of oxygen, with several different silver (Ag 0) concentrations (10.907, 15.96, 31.92, 39.5, respectively) and 56.88 ppm Ag-NPs ppm for the anti-germs tests, while for the treatment of a dermatosis of unknown etiology we used the gel with the smallest silver concentration. For the gel with the highest metallic silver concentration of 56.88 ppm, after 48 hours at 37 o C, no one of the germs E. coli, S. aureus or C. albicans resisted. Candida albicans fungus showed an increased sensitivity to metallic silver, as it was eradicated after only 24 h. Probably, in the biological processes Ag 0-cell, the poly(hydroxy urethane-acrylate), also intervenes, as this might facilitate the accumulation of nanometric silver on the extracellular matrix (ECM). Thus, the microorganism might accumulate faster the amount of silver, which stops its vital functions, such as the permeability and breathe. The developed gel with the smallest silver concentration, of 10.907 ppm Ag-NPs, lead to very good results in the treatment of a dermatosis of unknown etiology, after 78 days of treatment.