Studies Of Nano-electrochemical Immunosensor Used For Detecting Gastric Cancer Markers

Gastric cancer is one of the most common malignant tumors. The incidence and mortality rates of gastric cancer rank the second and third, respectively. No symptom of the early gastric cancer makes the early gastric cancer clinical diagnosis difficult. Therefore, the early diagnosis level is of great significance in improving the quality of survival and the evaluation of the treatment effect. Nano-electrochemical immunosensor is a kind of biosensor combined nanotechnology, immunology technology, and electrochemical analysis, which possess the advantages, such as high sensitivity, good selectivity, easy operation, and fast analysis speed, and so on. With the deepening of the research, novel nano-electrochemical immunosensors with high sensitivity and high selectivity have developed rapidly, in order to meet the needs of the life science research and clinical medicine. At the same time, to meet the demand of clinical testing, the development of high sensitive, accurate, economic and high-throughout of multiple tumor markers detection analysis method is the long-term pursuit of clinical diagnosis.Aiming at the early determination of gastric cancer, this work has combines the high specific immunoassay technology, signal amplification strategy, multi-probe labeling technique with the electrochemical detection technique, and focuses on the synthesis functional nanomaterials, construction of novel signal enhancement strategy and developing of high sensitive immunosensor interface. Two kinds of novel nano-electrochemical immunosensors have been fabricated to realize the rapid and sensitive detection of gastric cancer markers, and novel method for sensitive, rapid, portable and economic simultaneous determination of double gastric cancer markers has been developed. The details of this paper are given as follows:Part One: Study of electrochemical immunosensor based on multiple signal amplification technology for detecting gastric cancer biomarker CA72-4In this work, a high sensitive electrochemical immunosensor based on tungsten sulfide- reduced graphene oxide- chitosan(WS2-Gr-CS) modified electrode as the sensor platform, Au nanoparticles-Fe3O4-polydopamine(Au-Fe3O4-PDA) nanocomposite as the secondary antibody label, and the silver amplification technologyhas been developed. Under the optimum experimental conditions, in the range of 0.0001~5 U/mL, the concentration of CA72-4 were proportional to the decreased currents, with a detection limit of 3×10-5 U/mL. The biosensor showed excellent stability, good selectivity, and acceptable reproducibility. This multiple signal amplification strategy significantly improved the sensitivity of sensors, reduced the detection limit.Part Two: Studies of electrochemical immunosensor based on double signal nanoprobes for simultaneous multiplexed detection of gastric cancer markers as a secondary antibody labelIn this work, Au nanoparticles–toluidine blue–graphene oxide(AuNPs-TB–GO) and Au nanoparticles–carboxyl ferrocene–tungsten disulfide(AuNPs–FMC–WS2) nanocomposites were prepared for labeling CEA and CA72-4 antibody, respectively, and used as two kinds of probes with different electrochemical signals. With the excellent magnetic performance of biotin magnetic beads(IMBs), the biofunctional IMBs were firmly deposited on the electrode surface by applying a constant magnetic field, and then the CEA and CA72-4 antibody were immobilized on the IMBs by the avidin–biotin conjugation. The assay was based on the chang in the detection peak current at two peak potentials in the presence of the corresponding signal tags. Under the optimum experimental conditions, the linear range of detection of CEA is of the two-component immunosensoris 0.01 ~ 120 ng/mL, with a low detection limit of 0.003 ng/mL, and the linear range of detection of CA72-4 is 0.05 ~ 35 U/mL, with a detection limit of 0.016 U/mL. The results showed that the proposed immunosensor enabled simultaneous monitoring of CEA and CA72-4, and exhibited good reproducibility, excellent high selectivity and sensitivity. In particular, the proposed multiplexed immunoassay approach does not require sophisticated fabrication, and is well-suited for high-throughput biosensing and application to other areas.