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G-quadruplex DNAzyme-based microcystin-LR (toxin) determination by a novel immunosensor

Zhu, Yingyue, Xu, Liguang, Ma, Wei, Chen, Wei, Yan, Wenjing, Kuang, Hua, Wang, Libing, Xu, Chuanlai
Biosensors & bioelectronics 2011 v.26 no.11 pp. 4393-4398
World Health Organization, antibodies, antigen-antibody complex, antigens, colorimetry, detection limit, drinking water, immunoassays, immunosensors, microcystin-LR, nanogold, peroxidase, screening
In this paper, we demonstrate the application of versatile G-quadruplex–hemin DNAzymes in an immunoassay for detecting Microcystin-LR (MC-LR). Taking advantage of the high peroxidase activity of G-quadruplex–hemin complexes and the enhancement effect of gold nanoparticles (AuNPs), the method showed simple, high sensitive and selectivity detection of target toxin residues in water samples. The coated antigen, MC-LR–ovalbumin (OVA) coated on a plate, competed for MC-LR antibody with added target analyte to form antibody–antigen immune complexes. Subsequently, the immune complex reacted with G-quadruplex-labeled secondary antibodies for colorimetric detection of MC-LR. This assay specifically determined MC-LR in the linear range of 0.1–10ng/ml, with a limit of detection (LOD) of 0.05ng/mL for MC-LR. The results indicated that the novel immunoassay was an alternative to traditional plate-based immunoassay for MC-LR residue screening due to this method met the standard of World Health Organization (WHO) requirements for MC-LR content in drinking water (1ng/mL).