(420i) Gold Nanoparticle-Based Biosensor for Colorimetric Detection of Helicobacter Pylori In Water

Authors: 
Calle, L. M., Universidad de los Andes
Reyes, J. R., Universidad de los Andes
Galvis, A. A., Universidad de los Andes
Vargas, W. L., Universidad de los Andes


Bottom–up nanotechnology approaches offer a wide array of nanoparticles (NPs) with special interest in biosensing. Gold nanoparticles (Au-NPs) have been the focus of attention in recent years due to their unique size and shape-dependent properties (including, optical, electrical, magnetic, catalytic, mechanical, and chemical) which make them interesting for biological applications. Therefore, biosensing platforms based on the application of Au-NPs are of great interest and are actively being pursued.

In this study, a colorimetric biosensor has been developed to give a rapid response for the presence or absence of Helicobacter pylori in water based on differences in electrostatic properties of single- and double-stranded oligonucleotides (ssDNA and dsDNA), no functionalization of the gold, the probe, or the target DNA is involved. The biosensor operates in two steps; the first step involves hybridization of a DNA probe with a complementary ssDNA sequence of the target pathogen, and second; a visual detection from colloidal gold particle aggregation for a positive result due to surface plasmon resonance which is greatly affected by agglomeration. DNA probe, target DNA and colloid amounts were optimized in order to improve the colorimetric readout.

Target DNA was extracted from a Helicobacter Pylori culture and denatured to obtain ssDNA, a lyophilized oligonucleotide complementary sequence was purchased and used as received, salt solution of given ionic strength was used to screen the repulsive interactions of Au-NPs and induced the aggregation. Colloidal gold was synthesized by means of citrate reduction of HAuCl4 (Turkevich method). Gold nanoparticles were characterized by Scanning Electron microscopy (SEM), Ultraviolet-visible spectroscopy, Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and Atomic force microscopy (AFM). This simple colorimetric hybridization assay has also been integrated into a disposable microfluidic device for simple widespread use.  The results show that this relatively simple assay is surprisingly robust in its ability to detect the presence of the target pathogen.