Universal Correlation and Mechanism for the Antibacterial Activity of Silver Nanoparticles
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1209-YY01-07
Universal Correlation and Mechanism for the Antibacterial Activity of Silver Nanoparticles Georgios A. Sotiriou1, Adrian Camenzind1, Frank Krumeich2, Andreas Meyer3, Sven Panke3 and Sotiris E. Pratsinis1* 1
Particle Technology Laboratory, Institute of Process Engineering, Department of Mechanical and Process Engineering 2 Laboratory of Inorganic Chemistry, Department of Chemistry and Applied Biosciences Sonneggstrasse 3, CH-8092 Zurich 3 Bioprocess Laboratory, Department of Biosystems Science and Engineering Mattenstrasse 26, CH-4058 Basel Swiss Federal Institute of Technology Zurich (ETH Zurich), Switzerland ABSTRACT Silver clusters (4-150 nm) anchored on nanostructured silica particles (300-400 m2/g) with closely controlled Ag content and size were made in one-step by scalable flame spray pyrolysis of Ag-nitrate and hexamethyldisiloxane containing solutions. Composite Ag/SiO2 nanoparticles were characterized by S/TEM, EDX spectroscopy, X-ray diffraction, N2 adsorption. The activity of such nanoparticles against the Gram negative bacterium Escherichia coli was investigated by monitoring the recombinantly synthesized green fluorescent protein. It is shown that higher Ag content particles exhibit a stronger antibacterial effect. INTRODUCTION Silver can conduct electricity and heat better than any other metal [1]. It has been used since antiquity for coins, jewelry and silverware, and later on in photography, explosives, and dental alloys [2]. Lately, the unique properties of Ag nanoparticles bring them to catalysis [3], biological labeling [4], and surface enhanced Raman scattering (SERS) [5]. Another property of silver is its ability to kill microorganisms. This is not unique to silver but also other metals have it like mercury and lead that are, however, toxic to humans while silver is not [6]. This antibacterial property has been known for years. Silver vessels were used in the past to preserve water and wine [2]. Even till modern times, bandages for burn wound treatments contain silver compounds for faster healing while medical equipment such as catheters are coated with silver compounds to prevent infections [7]. Silver nanoparticles inhibit bacterial growth by their contact with (or even penetration into) the cell and the released Ag+ ions from their surface [7-9]. Furthermore, Ag ions interfere with DNA replication [10]. When Ag nanoparticles are partially oxidized, their antibacterial activity increases, while metallic Ag nanoparticles alone exhibit limited bactericidal activity [11, 12]. The question, however, remains whether it is the contact of bacterial cells with Ag nanoparticles or Ag+ ions released from their surface that determine the bactericidal activity of silver [13]. Such questions need to be addressed before Ag nanoparticles are ready to be employed in biological applications and commodities (e. g. textiles [14] or polymers films [15]). An answer to such questions would help understand the interactions between biological systems and nanoparticles which can be used as antibacterial
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