The inhibitory effects of silver nanoparticles, silver ions, and silver chloride colloids on microbial growth
WATER RESEARCH 42 (2008 ) 3066 – 3074
a b s t r a c t
Emerging nanomaterials are of great concern to wastewater treatment utilities and the
environment. The inhibitory effects of silver nanoparticles (Ag NPs) and other important Ag
species on microbial growth were evaluated using extant respirometry and an automatic
microtiter fluorescence assay. Using autotrophic nitrifying organisms from a well-controlled
continuously operated bioreactor, Ag NPs (average size ¼ 1476nm), Ag+ ions (AgNO3), and
AgCl colloids (average size ¼ 0.25 mm), all at 1mg/L Ag, inhibited respiration by 8673%,
4277%, and 4674%, respectively. Based on a prolonged microtiter assay, at about 0.5mg/L
Ag, the inhibitions on the growth of Escherichia coli PHL628-gfp by Ag NPs, Ag+ ions, and AgCl
colloids were 5578%, 100%, and 6676%, respectively. Cell membrane integrity was not
compromised under the treatment of test Ag species by using a LIVE/DEAD BaclightTM
bacterial viability assay. However, electron micrographs demonstrated that Ag NPs attached
to the microbial cells, probably causing cell wall pitting. The results suggest that nitrifying
bacteria are especially susceptible to inhibition by Ag NPs, and the accumulation of Ag NPs
could have detrimental effects on the microorganisms in wastewater treatment.
Hydrogel networks as nanoreactors: A novel approach to silver nanoparticles for antibacterial applications
Polymer 48 (2007) 158 - 164
Abstract
Hydrogel networks based on N-isopropylacrylamide (NIPAM) and sodium acrylate (SA) were prepared by redox-polymerization in the
presence of N,N0-methylenebisacrylamide (MBA). Highly stable and uniformly distributed silver nanoparticles have been prepared using these
hydrogel networks as a carrier via in situ reduction of silver nitrate in the presence of sodium borohydride as a reducing agent. It has been
demonstrated that the hydrogel hybrid with different sizes of silver nanoparticles can be effectively employed as antibacterial material.
Antimicrobial effects of silver nanoparticles
Nanomedicine: Nanotechnology, Biology, and Medicine 3 (2007) 95– 101
The antimicrobial effects of silver (Ag) ion or salts are well known, but the effects of Ag
nanoparticles on microorganisms and antimicrobial mechanism have not been revealed clearly.
Stable Ag nanoparticles were prepared and their shape and size distribution characterized by particle
characterizer and transmission electron microscopic study. The antimicrobial activity of Ag
nanoparticles was investigated against yeast, Escherichia coli, and Staphylococcus aureus. In these
tests, Muller Hinton agar plates were used and Ag nanoparticles of various concentrations were
supplemented in liquid systems. As results, yeast and E. coli were inhibited at the low concentration
of Ag nanoparticles, whereas the growth-inhibitory effects on S. aureus were mild. The free-radical
generation effect of Ag nanoparticles on microbial growth inhibition was investigated by electron
spin resonance spectroscopy. These results suggest that Ag nanoparticles can be used as effective
growth inhibitors in various microorganisms, making them applicable to diverse medical devices and
antimicrobial control systems.
Biological properties of “naked” metal nanoparticles
Advanced Drug Delivery Reviews xxx (2008) xxx-xxx (in press)
Over the past few decades, inorganic nanoparticles, which exhibit significantly distinct physical, chemical
and biological properties from their bulk counterpart's, have elicited much interest. Discoveries in the past
decade have demonstrated that the electromagnetic, optical and catalytic properties of noble-metal
nanoparticles such as gold, silver and platinum, are strongly influenced by shape and size. This has motivated
an upsurge in research on the synthesis routes that allow better control of shape and size for various nanobiotechnological
applications. Biomedical applications of metal nanoparticles have been dominated by the
use of nanobioconjugates that started in 1971 after the discovery of immunogold labeling by Faulk and Taylor.
Currently metal-based nanoconjugates are used in various biomedical applications such as probes for
electron microscopy to visualize cellular components, drug delivery (vehicle for delivering drugs, proteins,
peptides, plasmids, DNAs, etc), detection, diagnosis and therapy (targeted and non-targeted). However
biological properties of bare-metal (naked) nanoparticles have remained largely unexplored. Therefore, in
this review we discuss the novel biological properties and applications of three most widely used metal
nanoparticles, namely, the nanoparticles of gold, silver and platinum. We describe the novel properties and
use of these nanoparticles in angiogenesis and cancer related disorders.