Electrochemical Biosensing Technology For Detecting Heavy Metal And Protein

Heavy metals in the environment are difficult to degrade, which can be accumulated into the human body through the food chain, leading a serious threat to people's health and life. Proteins as the basic material of living organisms with large content and wide variety take part in every step of the reaction and activities, and being closely related to the origin, evolution of life, physical functioning, genetic and so on. Moreover, the concentration of proteins is closely related to the body's metabolism, becoming the basis for identification and diagnosis. Therefore, it is of great significance to establish a simple, fast, sensitive protein detection method used in drug research, clinical treatment of medical research. Electrochemical biosensor with real-time, stable, online, quick, selective, visual inspection involved in pharmaceutical, environment, food and metal areas, indicating its broad space to develop and apply. In this research paper, we construct several electrochemical sensors, the details are described as follows:(1) A novel electrochemical sensor has been developed for sensitive and selective detection of mercury(II) based on target-induced structure-switching DNA. A 33-mer oligonucleotide 1 with five self-complementary base pairs separated by seven thymine-thymine mismatches was first immobilized on the electrode via self-assembly of the terminal thiol moiety and then hybridized with a ferrocene-tagged oligonucleotide 2, leading to a high redox current. In the presence of Hg2+, mercury-mediated base pairs (T-Hg-T) induced the folding of the oligonucleotidel into a hairpin structure, resulting in the release of the ferrocene-tagged oligonucleotide 2 from the electrode surface with a substantially decreased redox current. The response characteristics of the sensor were thoroughly investigated using cyclic voltammetry (CV), differential pulse voltammetry (DPV) and electrochemical impedance spectroscopy (EIS). The effect of the reaction temperature on the response of the sensor was also studied in detail. The results revealed that the sensor showed sensitive response to Hg2+ in a concentration range from 0.1 nM to 5μM with a detection limit of 0.06 nM. In addition, this strategy afforded exquisite selectivity for Hg2+ against other environmentally related metal ions, which was superior to that of previous anodic stripping voltammetry (ASV)-based techniques. The excellent sensitivity and selectivity signified the potential of the sensor for Hg2+ detection in real environmental samples.(2)We establish a new electrochemical sensor based on immunoliposome for sensitive and selective detection of alpha-fetoprotein. Sensitive electrochemical methods and encapsulated labled DNA probe in liposome, lead to inceasing of sensitivity. At the same time, The results revealed that the sensor showed sensitive response to AFP in a concentration range from 1 fg/mL to 10 ng/mL, with a detection limit of 0.7 fg/mL.(3)A novel electrochemical immunosensor based on double signal amplification of enzyme-encapsulated liposomes and biocatalytic metal deposition was developed for the detection of human prostate specific antigen (PSA). Alkaline phosphatase (ALP)-encapsulated and detection antibody-functionalized liposomes were first prepared and used as the detection reagent. In the sandwich immunoassay, the model analyte PSA was first captured by anti-PSA capture antibody immobilized on the electrode and then sandwiched with the functionalized liposomes. The bound liposomes were then lysed with surfactant to release the encapsulated ALP, which served as secondary signal amplification means. ALP on the electrode surface initiated the hydrolysis of ascorbic acid 2-phosphate (AA-p) to produce ascorbic acid. The latter, in turn, reduced silver ions on the electrode surface, leading to deposition of the metal silver on the electrode surface. Linear sweep voltammetry (LSV) was chosen to detect the amount of the deposited silver. The results showed that the anodic stripping peak current was linearly dependent on the PSA concentration in the range of 0.01 ng/mL to100.0 ng/mL, and a detection limit as low as 0.007 ng/mL can be obtained. Since the cut-off value of human PSA is 4.0 ng/mL, the proposed electrochemical immunosensor would be expected to gain widespread applications for the detection of PSA in clinical diagnosis.