Preparation And Application Of Electrochemical Sensors With Signal Amplification Based On MnO₂ Nanosheets

Manganese dioxide has good ionic interaction,redox properties,molecular adsorption.In this thesis,manganese dioxide nanosheets with particle size of about 100-150 nm were synthesized by chemical synthesis method,and used to prepare electrochemical biosensors.The breast cancer marker HER2 is often overexpressed in patients with early breast cancer,and the detection of HER2 is helpful for early screening of breast cancer.Ascorbic acid is an important antioxidant,which plays an important role in reducing cell oxidation,preventing chronic diseases.The traditional detection of HER2 and ascorbic acid has the disadvantages of low sensitivity and complicated operation.In this thesis,manganese dioxide based signal amplification electrochemical sensors were prepared to achieve high sensitive and rapid electrochemical detection of breast cancer marker HER2 and ascorbic acid.The main research work of this thesis is summarized as follows.1.Manganese dioxide based electrochemical sensor for the detection of cancer marker HER2:We developed an electrochemical detection method capable of rapid and efficient detection of HER2concentration using functionalized Mn O₂nanosheets as electrochemical probes.Phosphate ions and HER2 aptamers were adsorbed directly onto the nanosheets.The reaction of phosphate ion and the phosphate group of aptamer with molybdate produced an electrochemical current.The HER-2-specific aptamer in this sensor acts as both a recognition probe as well as signal probe,and this dual signal amplification strategy greatly increases the sensitivity of the detection.The intensity of the current generated by the sensor at 0.22 V is proportional to the HER2concentration,and there is a linear range between the current response and the logarithm of the HER2 concentration in the range of 0.1-500pg·m L^-1with a detection limit of 0.05 pg·m L^-1.Finally,the analysis of breast cancer patient serum by commercial ELISA kits and our sensor was performed,and the two detection results were agreed well.2.Manganese dioxide based electrochemical sensor for the detection of ascorbic acid:Phosphomolybdate thin film electrochemical sensor based on manganese dioxide nanosheets was constructed for the detection of ascorbic acid.Phosphate ions were modified onto the manganese dioxide nanosheets,and the phosphate ions reacted with sodium molybdate to generate phosphomolybdate thin film,which has electrochemical catalytic activity.The intensity of the anodic current generated by the sensor at 0.35 V is proportional to the concentration of ascorbic acid from 0.1 m M to 1.5 m M with a detection limit of 0.02 m M,and the commercial sample recovery is between 100-102.8%.The sensor can widen the detection linear range,improve the detection sensitivity,and reduce the interference of other substances on the detection.This thesis contains 27 figures,11 tables,and 143 references...