An Electrochemical Metalloimmunoassay Based on a Colloidal Gold Label

Abstract

A novel, sensitive electrochemical immunoassay has been developed using a colloidal gold label that, after oxidative gold metal dissolution in an acidic solution, was indirectly determined by anodic stripping voltammetry (ASV) at a single-use carbon-based screen-printed electrode (SPE). The use of disposable electrodes allows for simplified measurement in 35 microL of solution. The method was evaluated for a noncompetitive heterogeneous immunoassay of an immunoglobulin G (IgG) and a concentration as low as 3 x 10(-12) M was determined, which is competitive with colorimetric ELISA or with immunoassays based on fluorescent europium chelate labels. The high performance of the method is related to the sensitive ASV determination of gold(III) at a SPE (detection limit of 5 x 10(-9) M) and to the release of a large number of gold(III) ions from each gold particle anchored on the immunocomplex (e.g., 1.7 x 10(5) gold atoms are theoretically contained in a 18-nm spherical gold particle).

Successively amplified electrochemical immunoassay based on biocatalytic deposition of silver nanoparticles and silver enhancement

“…The coupling of the high catalytic action of enzyme and metal nanoparticles makes the immunoassay ultrasensitive with a very low detection limit, favorably compared with the electrochemical metalloimmunoassay based on a colloidal gold label of which detection limit for goat IgG is 0.5 ng ml −1 (Dequaire et al, 2000). This strategy is even preferable to the electrochemical stripping metalloimmunoassay based on silver-enhanced gold nanoparticle label of which detection limit for human IgG is 1.0 ng ml −1 (Chu et al, 2005) and comparable with the fluoroimmunoassay of which the detection limit is 0.1 ng ml −1 (Evangelista et al, 1991).…”

“…Based on these advantages, colloidal gold was first applied as TEM marker in 1971 (Faulk and Taylor, 1971), and was then introduced for SEM in 1975 (Horisberger et al, 1975). Recently, besides the application of metal nanoparticles in some analytical methods such as UV-vis (Schofield et al, 2006), Raman (Ni et al, 1999;Santos et al, 2004) and time-resolved fluorescence spectroscopy (Ipe and Thomas, 2004), SPR (He et al, 2000;Lyon et al, 1998) or QCM techniques (Zhou et al, 2000), a new electrochemical metalloimmunoassay by using colloidal gold as label was reported, which pushed the sensitivity of immunoassay to the picomolar domain (Dequaire et al, 2000). Further sensitivity enhancement can be obtained by the application of metal-enhanced gold nanoparticles, where functional gold nanoparticles act as catalysts to reduce gold or silver ions on themselves.…”

“…In these methods, the autocatalytic metal deposition procedure enlarges the size and darkens the color of nanoparticles, resulting in two to three orders of magnitude improvement in detection sensitivity of scanning electrochemical microscope , QCM (Su et al, 2001) or electrochemical stripping techniques (Wang et al, 2001;Cai et al, 2002;Liao and Huang, 2005;Chu et al, 2005). Anodic stripping voltammetry (ASV) has been proved to be a powerful approach for trace determination of metal ions (Jacobs, 1963;Dequaire et al, 2000). Its remarkable sensitivity is attributed to the preconcentration step during which the target metal is accumulated onto the surface of the working electrode through cathodical electro-deposition and the stripping step when the metal is stripped from the electrode by anodic oxidation.…”

Biomolecules and Pure Carbon Aggregates: An Application Towards “Green Electronics”

“…In contrast to the above, the application of nanoscale materials for electrochemical biosensors has been grown exponentially due to high sensitivity and fast response time [11,12]. So we can say that there evolved a parallel study as nano-bio-complexes in the field of green electronics, blending the biomolecules and nanotechnology.…”

Enhanced electrochemical activity of redox-labels in multi-layered protein films on indium tin oxide nanoparticle-based electrode

“…When employed as signal-generating labels in the detection of biological affinity reactions such as DNA hybridization and immunoassays, gold and semiconductor nanoparticles have improved the detection sensitivity by orders of magnitude over their molecular counterparts [7][8][9][10][11][12][13]. This is attributed to the fact that each biological binding event is tagged with at least one * Corresponding author.…”