Evaluation of the effects of gold nanoparticles (AuNPs) on protein folding in Escherichia coli
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Date
2014
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Publisher
University of Zululand
Abstract
Gold nanoparticles have shown promising applications, more especially in the biomedical
industry. This has seen major improvements in disease diagnostics, therapeutics, imaging and
treatment. All this is owed to the unique physicochemical properties possessed by the AuNPs.
More studies continue to be carried out on AuNPs as the uses of these nanometer-sized particles
are limitless. Water soluble citrate capped gold nanoparticles were synthesized through a slightly
modified citrate method. In order to determine size, shape, dispersion and the crystalline nature of
the AuNPs, characterization was done using Transmission electron microscopy (TEM) and High
resolution transmission electron microscopy (HRTEM). The AuNPs were used to ascertain
bacterial-nanoparticle interactions, their effect on E.coli growth as well as the effect on the
solubility of E.coli proteins. The in vitro effects on DNA and protein integrity was also determined.
The bacteria work was done by exposing E.coli to AuNPs. Imaging was done through TEM and
bacterial growth monitored by measuring optical density at hourly intervals. AuNPs were
assimilated by the bacterial cells with minimal effects on cellular integrity in DnaK- cells. DnaK
+ cells exhibited containment of AuNPs in the cytosol. AuNPs also inhibited E.coli growth
marginally and had no observable effect on the solubility of E.coli proteins at the concentrations
tested (25-75 μg/mL) in DnaK+ cells. MDH and MDH in the presence of PfHsp70 were exposed
to AuNPs. The AuNPs effect was ascertained by SDS-PAGE. Citrate AuNPs managed to suppress
MDH aggregation at low concentrations (2.5-25 μg/mL). At all the concentrations used, the citrate
AuNPs complemented the ability of PfHsp70 in suppressing MDH aggregation. The stability of
DNA exposed to AuNPs was confirmed by agarose gel electrophoresis and transformations into
E.coli XL1 blue cells. DNA damage was observed at concentrations (25-100 μg/mL) after
exposure for forty-eight (48) hours and for damaged DNA preparations no or fewer colony forming
units were observed on agar plates. These findings show that citrate AuNPs are less cytotoxic and
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can maintain proteins in soluble form. Although their effect on protein solubility is valuable, citrate
AuNPs impact on protein function and are damaging to DNA. Further studies need to be carried
out in order to fine tune the physicochemical properties of these particles as a way of improving
the biosafety of the AuNPs.
Description
Submitted in fulfilment for the award of the degree of Master’s (MSc) in Biochemistry
Department of Biochemistry and Microbiology, Faculty of Science and Agriculture, at the
University of Zululand, South Africa, 2014.
Keywords
Nanoparticles, Nanoparticles - gold