Studies On The Development Of Biosensor Detection Of OTA And Hg(Ⅱ) In Foods Based On Aptamer

Specificity, high sensitivity and rapid detection of heavy metals and toxins have great significance for food safety. Aptamer can get through systematic evolution of ligands by exponential enrichment (SELEX). Aptamer have played an important pole in many areas of the toxin and heavy metals'detection. Based on aptamer, we have build the NMR method to detect Hg²⁺ ion, as well as colloidal gold and quantum dot strip for the detection of ochratoxin A method.In this paper, these aspects as the main content:1. Aptamer of OTA marked gold nanoparticles, prepared by this complex, we developed a quick and on-site sensor for detection of OTA in the competion format. The best ratio between gold nanoparticles and DNA is 1:10 , the best buffer is 0.01M pH7.4 PB(0.5%PEG,1%sucrose,0.1%Tween20,0.02% MgSO4,0.05% (NH4)2SO4)and take the CN140 nitrocellulose membrane. The test strip took the qualitative and semi-quantitative measurement of OTA within 15min .We got a good linear relationship between OTA and the response signal. The limit of detection with naked eyes is 2.5ng/mL, and according to the standard curve, the linear range is 0.2-2.5ng/mL and LOD is 0.18ng/mL.2. Aptamer of OTA marked quantum dots, prepared by this complex, we developed a quick and on-site sensor for detection of OTA in the competion format. The best buffer is 0.01M pH7.4 PB(1.5%PVP,1%sucrose,0.1%Tween20,0.02% MgSO4,0.05% (NH4)2SO4) and take the M135 nitrocellulose membrane. The test strip took the qualitative and semi-quantitative measurement of OTA within 15min. The limit of detection with naked eyes is 5ng/mL, and according to the standard curve, the linear range is 2.2-10ng/mL and LOD is 1.9ng/mL.3. We conjugated the T-rich nucleic acid to magnetic nanoparticles which would form the T- Hg²⁺-T structure with the accession of Hg²⁺. Then magnetic nanoparticles began to aggregate, hence lead to a change in the distribution of water proton. Using the magnetic resonance imaging apparatus, we got T2–weighted images and T2 contrast image. The more Hg²⁺ concentration increased, the more water proton environment changed. Accordingly T2 contrast image became dimmed and T2 relaxation time gradually decreased. We got a good linear relationship between the analyte concentration and the response signal. The linear range is 0.25-10pg/mL, and the limit of detection is 0.15pg/mL.