Colorimetric immunoassay chip based on gold nanoparticles and gold enhancement

Abstract

A colorimetric immunoassay chip has been developed based on gold nanoparticles for indicating the antibody-antigen binding activity and gold enhancement for amplifying the specific binding signal. Our investigations showed that the results of immunoassay can be represented by the level of color intensity. They were easily observed by a regular camera or naked eye, which is not needed of sophisticated laboratory equipment. Optimization of experimental conditions was carried out and the colorimetric detection had been compared to the standard chemifluorescent detection. Under the optimized conditions, colorimetric immunoassay chip had been demonstrated to detect different amount of immobilized antigens, i.e., human IgG. The results, i.e., color intensity, were mapped to the concentration of immobilized antigens in a dynamic range of 1-5,000 ng/ml. The proposed detection method does not require any sophisticated optical systems; therefore, it is possible to be miniaturized and integrated into a microfluidic system for developing a portable immunoassay device.

Novel plastic biochips for colorimetric detection of biomolecules

“…It appears that a colorimetric-based biochip (in which biorecognition events are transduced into color) is a promising candidate for such need, as the color change can be observed by the naked eye, common camera or flatbed scanner, thereby requiring no specialized equipment . For constructing this type of biochip, it is believed that the transduction of biorecognition events into visual signals is the critical step, which is typically realized by using enzyme- [17,18] or nanoparticle- [10][11][12][13][14][15][16][17][19][20][21][22][23][24][25][26][27][28][29][30][31][32][33] catalyzed deposition strategies. Gold nanoparticle (AuNP) labeling followed by silver staining (also called autometallography or silver enhancement) is one of the most efficient ways to achieve color labeling and signal amplification, thus has been widely adopted in colorimetric detection in the past decade [10,11,14,16,20,[23][24][25][29][30][31].…”

Microfluidic Systems for Diagnostic Applications: A Review

“…Colorimetric and electrical immunoassays using antibody-nanogold conjugates and gold enhancement have been demonstrated. [106][107][108] Moreover, nanogold particles have been applied to the electrochemical detection of protein binding activity. 109,110 The immunoassay of goat IgG was performed using donkey anti-goat IgG labeled by nanogold.…”

Nanostructured substrates for portable and miniature SPR biosensors

“…The increase in scattering of Au NP and wavelength shift from the absorption of Au NP on glass can lead to a functional biosensor [35]. Use of a flatbed scanner as detection method has also been demonstrated for reading bioassays on glass [33,34]. In one example, BSA was detected at 1 ng mL −1 with the paper-based biosensor, which is close to the detection limit of ELISA assays recently reported in the literature (0.38 ng mL −1 ) [36] or with commercial ELISA kits at 0.25 ng mL −1 [37].…”

“…4). Au NP labelled with secondary antibodies or streptavidin induce the color change in the presence of the analyte at the surface of the glass slide [33,34]. Well-established surface chemistry and adequate transparency for transmission measurements are advantages of glass.…”