Journal
NPG ASIA MATERIALS
Volume 4, Issue -, Pages -Publisher
NATURE PUBLISHING GROUP
DOI: 10.1038/am.2012.18
Keywords
colorimetric detection; copper ion; gold nanoparticles; immunoassays
Categories
Funding
- National Basic Research Program of China [2010CB732403]
- National Natural Science Foundation of China [21125524, 20975023]
- Program for New Century Excellent Talents in University of China [09-0014]
- Program for Changjiang Scholars and Innovative Research Team in University [IRT1116]
- National Science Foundation of Fujian Province [2010J06003]
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In this study, a novel method for the fast, sensitive and selective detection of Cu2+ using gold nanoparticles (AuNPs) was developed and used in immunoassays. In the presence of L-cysteine, L-cysteine can bind to the surface of citrate-stabilized AuNPs through Au-S bonds. As a result, aggregation of AuNPs occurs through electrostatic interactions between the cysteine-bound AuNPs. In contrast, in the presence of Cu2+, Cu2+ can catalyze O-2 oxidation of cysteine, leading to the quick formation of disulfide cystine. An increase in the concentration of Cu2+ decreased L-cysteine-induced AuNPs aggregation by decreasing the number of free cysteine thiol groups, and the solution color changed from purple to red. Therefore, the concentration of Cu2+ can be detected with the naked eye or with ultraviolet-visible spectroscopy, and the detection limits of Cu2+ were 20 nM and 10 nM, respectively. This sensitivity was approximately three orders of magnitude higher than that of traditional AuNPs-based colorimetric Cu2+ detection methods. Because of the high sensitivity of the proposed method, we further used it with a labeled antibody in colorimetric immunoassays. The detection limit of the cancer biomarker alpha-fetoprotein was 2 ng ml(-1), which is comparable to the detection limit of the enzyme-linked immunosorbent assay method. NPG Asia Materials (2012) 4, e10; doi: 10.1038/am.2012.18; published online 16 March 2012
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