Determination of Ochratoxin A Using a Cathodic Photoelectrochemical Sensor Based on AgBr£­Ag£­CNTs Composite and Aptamer

KeyWord:AgBr£­Ag£­CNTs  photocathode sensor  aptamer  ochratoxin A

Abstract:

      Photocathode-based sensors possess the advantages of high selectivity and anti-interference in real sample detection£¬though photocathode produces low photocurrent signal and gives rise to poor sensitivity£®Herein£¬a novel silver bromide-silver-carbon nanotubes£¨AgBr£­Ag£­CNTs£© composite was synthesized by solvothermal method£¬and was characterized by scanning electronic microscopy£¬X-ray diffraction and X-ray photoelectron spectroscopy£®Because reduced Ag has revealed localized surface plasmon resonance effect£¨LSPR£©£¬it can amplify light absorption efficiency£®Furthermore£¬CNTs could optimize the electric field near metallic Ag£¬strengthen light absorption and improve the separation efficiency of photo-generated carriers£®Thus AgBr£­Ag£­CNTs displayed an better cathodic photoelectrochemical activity£¬compared with AgBr or AgBr£­Ag£®With K3£ÛFe£¨CN£©6£Ý as photoelectron acceptor£¬the photocurrent response could be further increased£®To develop the practicality of AgBr£­Ag£­CNTs£¬an ochratoxin A£¨OTA£© aptasensor was constructed by using AgBr£­Ag£­CNTs as photocathodic sensing interface£¬an aptamer as target recognition site£¬and K3£ÛFe£¨CN£©6£Ý as photoelectron acceptor£®Since the aptamer/OTA complex has a rigid structure with weak conductivity£¬it could effectively block the absorption of light with the sensing interface£¬inhibit the transfer of photoelectrons toward electron receptors£¬and reduce the photocurrent signal£®Based on the changed photocurrent as signal£¬the sensor showed a wide linear response from 4.0 pg/mL to 2.5 ng/mL£¨r2 = 0.994£© and a low detection limit of 1.5 pg/mL£®It was used for detection of OTA in real samples£¬with recoveries of 92.0%£­108%£®This work provided a novel photoelectrochemical method for OTA detection£¬with high sensitivity£¬specificity and good anti-interference£®