Double-Codified Gold Nanolabels for Enhanced Immunoanalysis

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• 作者：Adriano Ambrosi ; Maria Teresa Casta&ntilde ; eda ; Anthony J. Killard ; Malcolm R. Smyth ; Salvador Alegret ; Arben Merkoç ; i
• 刊名：Analytical Chemistry
• 出版年：2007
• 出版时间：July 15, 2007
• 年：2007
• 卷：79
• 期：14
• 页码：5232 - 5240
• 全文大小：408K
• 年卷期：v.79,no.14(July 15, 2007)
• ISSN：1520-6882

文摘

A novel double-codified nanolabel (DC-AuNP) based ongold nanoparticle (AuNP) modified with anti-human IgGperoxidase (HRP)-conjugated antibody is reported. Itrepresents a simple assay that allows enhanced spectrophotometric and electrochemical detection of antigenhuman IgG as a model protein. The method takes advantage of two properties of the DC-AuNP label: first, theHRP label activity toward the OPD chromogen that canbe related to the analyte concentration and measuredspectrophotometrically; second, the intrinsic electrochemical properties of the gold nanoparticle labels that beingproportional to the protein concentration can be directlyquantified by stripping voltammetry. Beside these twomain direct determinations of human IgG, a secondaryindirect detection was also applicable to this system,exploiting the high molar absorptivity of gold colloids, bywhich, the color intensity of their solution was proportional to the concentration of the antigen used in the assay.Paramagnetic beads were used as supporting material toimmobilize the sandwich-type immunocomplexes resulting in incubation and washing times shorter than thosetypically needed in classical ELISA tests by means of arapid magnetic separation of the unbound components.A built-in magnet graphite-epoxy-composite electrodeallowed a sensibly enhanced adsorption and electrochemical quantification of the specifically captured AuNPs. Theused DC-AuNP label showed an excellent specificity/selectivity, as a matter of fact using a different antigen(goat IgG) a minimal nonspecific electrochemical orspectrophotometric signal was measured. The detectionlimits for this novel double-codified nanoparticle-basedassay were 52 and 260 pg of human IgG/mL for thespectrophotometric (HRP-based) and electrochemical(AuNP-based) detections, respectively, much lower thanthose typically achieved by ELISA tests. The developedlabel and method is versatile, offers enhanced performances, and can be easily extended to other proteindetection schemes as well as in DNA analysis.