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Hun X.,Qingdao Technological University | Hun X.,Jiangnan University | Hun X.,State Key Laboratory Base of Eco chemical Engineering | Hun X.,Key Laboratory of Biochemical Analysis | And 11 more authors.
Biosensors and Bioelectronics | Year: 2013

In this work, a new signal amplified strategy based on target-induced strand release coupling cleavage of nicking endonuclease for the ultrasensitive detection of ochratoxin A (OTA) is reported. OTA aptamer (DNA1) and OTA aptamer complementary (DNA2) were immobilized onto a magnetic bead (MB). In the presence of OTA, DNA2 was dissociated and released from the MB. The released DNA2 then hybridized with DNA3, which was linked at the 5' terminus of the amplification template and can extend along the template in the presence of Phi 29 DNA polymerase. The formed double-stranded DNA was cleaved by nicking endonuclease Nb.BbvCI and produced a short single-stranded DNA. The cleaved DNA strand generated a new site by Phi 29 DNA polymerase and the process of extension and cleavage was cyclical. Thus, a amount of the short single-stranded DNA were produced. Using DNA and ABEI labeled carboxylic silica nanoparticles chemiluminescence (CL) probe, the short single-stranded DNA could be sensitively detected. The CL intensity (ΔI) versus the concentration of OTA was linear in the range from 1.0×10-12 to 5.0×10-8gmL-1. The detection limit was 3.0×10-13gmL-1, and the RSD was 3.4% at 1.0×10-10gmL-1 (n=7). The developed method has been applied to detect OTA in naturally contaminated wheat samples. Due to its simplicity, sensitivity and no need of specific recognition of aptamer for cleavage, this CL bioassay offers a promising approach for the detection of OTA and other biomolecules. © 2012 Elsevier B.V..

Hun X.,State Key Laboratory Base of Eco chemical Engineering | Hun X.,Qingdao University of Science and Technology | Chen H.,State Key Laboratory Base of Eco chemical Engineering | Chen H.,Qingdao University of Science and Technology | And 2 more authors.
Biosensors and Bioelectronics | Year: 2011

A label-free sensing technology for detection of Ramos cell was developed based on a signal probe Ru(bpy) 3Cl 2 (Ru) encapsulated by DNA. Gold electrode or magnetic bead as the sensing surface was firstly modified with long-strand DNA with five repeating units. Then two kinds of short-strand DNA are grafted onto the long-strand DNA to form DNA strands A and B (L-A and L-B) through the hybridization, respectively. The addition of aptamer initiates hybridization of L-A and L-B with the aptamer sequence. As the hybridization proceeds, the four kinds of DNA would finally transform into a three-dimensional network structure and the signal probe Ru was encapsulated by DNA simultaneously. When Ramos cells are introduced to interact with the aptamer, the signal probe is released. In order to confirm the generality of this method the ferrocenecarboxylic acid and luminol selected as a signal probe mode were also tested. The Ru used as a signal probe for electrogenerated chemiluminescence (ECL) detection was detailedly studied. With this ECL biosensor, detection limit as low as 58cells/mL was achieved for Ramos cell. The biosensor also exhibited excellent sensitivity and selectivity. © 2011 Elsevier B.V.

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