21-05-2012, 02:08 PM
Antibacterial effect of silver nanoparticles on Staphylococcus aureus
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Introduction
Nanotechnology merges materials at the atomic level with
unprecedented unique properties which can be suitably
manipulated for the desired application (Gleiter, 2000).
However, emerging literature on nanotoxicology has suggested
that nanoparticles might reveal new physicochemical and toxicological
properties (Lesniak et al., 2005; Handy et al., 2008;
Asharani et al., 2008). Colloidal silver nanoparticles (AgNPs)
smaller than 100 nm in at least one dimension have recently
received a great deal of attention and concern due to their
antibacterial activity (Shrivastava et al., 2007). AgNPs have
been widely used for development of biological and pharmaceutical
processes, products, and applications such as coating
material for medical devices, orthopedic or dental graft materials,
topical aids for wound repair, clothing, underwear and
socks, textile products, and even washing machines (Chen and
Schluesener, 2008; Navarro et al., 2008).
Materials and methods
Materials
S. aureus PTCC1431 was purchased from the Iranian
Research Organization for Science and Technology (IROST,
Iran). HPLC grade methanol and ethanol were obtained from
Caledon Co. (Georgetown, Canada). In all procedures, Milli-Q
HPLC grade water was used. Ammonium acetate, silver nitrate,
3-sodium citrate, hydrochloric acid, myo-inositol, acetic
anhydride, potassium hydroxide, hydroxylamine hydrochloride,
dichloromethane, DMSO, ethyl acetate, and hexane were
purchased from Merck. (Darmstadt, Germany). 4-dimethyl
amino pyridine was obtained from Alfa Aesar Co. (Karlsruhe,
Germany). MA and S. aureus cell wall PGN which were
supplied by SigmaeAldrich Co. (Steinheim, Germany) were
produced in Israel and Canada, respectively.
Circular dichroism (CD) study of PGN
In order to study the influence of AgNPs on cell walls, the
standard suspension of S. aureus PGN was used. Homogenized
suspension of standard PGN was prepared on DMSO
using 30 min sonication and treated with AgNP solution at
a ratio of 1:1. The secondary structural changes in the samples
were evaluated by CD spectroscopy. Results of measurements
were recorded over a wavelength range of 200e260 nm using
an AVIV spectropolarimeter, model 215 (USA) with a 0.1 cm
path length sample cell.