Antibacterial activity by nanosilver particles
- PDF / 865,482 Bytes
- 6 Pages / 612 x 792 pts (letter) Page_size
- 120 Downloads / 246 Views
Antibacterial activity by nanosilver particles Georgios A. Sotiriou and Sotiris E. Pratsinis Particle Technology Laboratory, Institute of Process Engineering, Department of Mechanical and Process Engineering ETH Zurich, Sonneggstr. 3, 8092 Zurich ABSTRACT The antibacterial activity of nanosilver against Gram negative Escherichia coli bacteria is investigated by immobilizing nanosilver on nanostructured silica particles and closely controlling Ag content and size. These Ag/SiO2 nanoparticles were characterized by S/TEM, EDX spectroscopy, X-ray diffraction. The antibacterical activity of these composite samples was investigated for a constant composite particle concentration. The highest activity was observed for the higher silver content particles. INTRODUCTION Nanosilver is used in heterogeneous catalysis [1] and has promising applications in textiles [2], biomedical applications [3], biodegradable polymer films for food packaging [4], biological labeling [5], photonics, coloristic (plasmon) [6], optoelectronics and surface enhanced Raman scattering (SERS) [7]. At the same time, the use of nanosilver raises concerns for its toxicity against aquatic microorganisms when disposed and therefore draws public attention [8]. In fact, nanosilver is one of the first nanomaterials to be regarded toxic and petitions had been filed to the U. S. Environmental Protection Agency (EPA) to regulate it as pesticide [9]. Therefore to safely employ nanosilver, correct risk and dose relations assessments need to be made [10,11]. There are several studies on the antibacterial activity of nanosilver made by wetmethods [12,13], co-condensation [14], electro-exploding wire [15] and flame spray pyrolysis [16,17]. Smaller nanosilver particles are more toxic than larger ones [13] especially when oxidized [13,16]. Additionally, even though silver metal is practically insoluble in water [18], when present in nanometer size range Ag+ ions are released (leached) [16,19,20] from its surface. It has been shown recently [17] that the antibacterial activity of small (15 nm) the antibacterial contribution by Ag+ ions and particles is comparable. Such a behavior implies a surface area dependency of the antibacterial activity especially for small nanosilver sizes since the Ag+ ion release is proportional to the exposed nanosilver surface area [17]. Additionally, when a nanothin silica coating on the surface of nanosilver is applied, this antibacterial activity can be minimized [21]. EXPERIMENTAL SECTION Particle synthesis Silver nitrate (Fluka, purity >99%) and hexamethyldisiloxane (HMDSO, Aldrich, purity >97%) were used as silver and silicon precursors, respectively. Appropriate amount of silver nitrate was dissolved in ethanol (Alcosuisse) and diethylene glycolmonobutyl ether (Fluka, purity >98%), both at a volume ratio 1:1, and stirred at
room temperature for 3 hours. The corresponding amount of HMDSO for a given xAg/SiO2 product was added and stirred for a few minutes just before that solution was fed into the FSP setup. The total metal (Ag and Si)
Data Loading...
