Application Of DNA Electrochemical Biosensor In DNA Methyltransferase Activity And Detection Of Tumor Cell Exosomes

DNA electrochemical biosensor is a kind of biosensor which based on the specific complementary pairing law between DNA molecules via the bases of DNA. And it's an emerging biosensor that based on cyclic voltammetry, differential pulse voltarmmetry, square wave cyclic voltammetry, AC impedance method and other electrochemical methods to study the physical and chemical properties of the redox that near the surface of the electrode, which can detect and analyze various targets. Since DNA electrochemical biosensor has many advantages such as fast analysis speed,simple operation, high sensitivity, good selectivity, good reproducibility and low test cost and so on, it has been widely used in the field of life sciences. DNA electrochemical biosensors can be used not only to detect specific DNA fragments associated with diseases, but also to study the diseases that caused by DNA damage. And they become increasingly important in anticancer drug screening, clinical diagnostics and environmental monitoring. In this paper, we constructed two DNA electrochemical biosensors which have been used to detect the activity of DNA methyltransferase and exosomes of tumor cells, respectively.DNA methylation is an epigenetic modification. This process is catalyzed by DNA methyltransferase (DNMT). Overexpression of DNMT1 can cause aberrant DNA methylation in human cells, and aberrant DNA methylation is directly linked to cancer,accordding to a research. Many studies have shown that DNMT1 is overexpressed in tumor cells such as colorectal, breast carcinomas, lung, stomach, pancreas, and liver cancer. Thus,an effective method for the easy detection of DNMT1 is required. We have established a DNA electrochemical sensor to detect the methyltransferase activity in cancer cell lysate samples effectively. The double amplification of the signal is achieved by the numerous DNAs on the Au NPs and the catalytic current generated between Ru(NH3)63+ and Fe(CN)63-, thus improving the sensitivity of detection. We tested and compared the activity of DNMT 1 in different cancer cells, and the results were consistent with those of the commercialization kit.As nano-sized extracellular vesicles with sizes of 30-150 nm, exosomes are secreted from various cells and exist in body fluids, including blood, saliva, urine and breast milk. Exosomes carry a variety of proteins, including cytosol proteins, proteins involved in intracellular signal transduction, various metabolic enzymes, heat shock protein, tetraspanin and other special proteins. They involve in the regulation of cell activity, and become early diagnostic markers for various diseases. Exosomes have become a research focus in the field of gene and drug delivery, tumor and tumor biology.Studies have shown that there is an antigen called PSMA exist on the exosomes of human prostate cancer cells, and it has become a marker for prostate cancer detection.Therefore, the detection of exosomes can be used to diagnose cancer. In this paper,DNA electrochemical biosensor was constructed base on the specific binding between antigen protein on exosomes and the aptamers, and signal amplification was achieved by using target molecular cycles. As exosomes exist in body fluids such as blood, urines and so on, they could be detected simply and effectively, enabling the cancer diagnosis.