Research On New Tumor Marker Detection Methods Based On Tool Enzymes And Nanomaterials

The highly sensitive determination of cancer cells and cancer biomarkers plays an important role in clinical screening and diagnosis of cancer. Biosensor constructed offering a lot of advantages such as simplicity, rapidness, low-cost and high sensitivity and other superior characteristics. It is widely employed for the studies of not only small molecule protein, nucleic acid but also protein molecules and even cells. Peroxidase mimetics, as an increasingly promising approach for the sensitive assay of inorganic ions and biomolecules, has aroused wide interest. Like the natural enzymes, the developed peroxidase mimetics exhibit excellent properties, including high substrate specificity and catalytic efficiency. such systems have broken through many of the restrictions that limit the application of natural enzymes such as low operational stability and high cost of preparation, purification, and storage. A new generation of hybrid nanomaterial-based peroxidase mimetics triggered much attention because of the particularly impressive properties and greater opportunities for catalysis of such materials. DNA, for the abilities of high chemical stability, easily being labeled and ready-availability, have attracted growing attention as materials in the construction of biosensors.In this thesis, electrochemical and fluorescent detection methods were employed as the main test means. a simple method with a novel graphene-derived hybrid nanomaterial-based peroxidase mimetic that is expected to be widely applied in the construction of simple, sensitive, and selective biosensors for nucleic acids and proteins both inside and outside of cells through catalytic reaction of H2O2, one kind of amplified DNA detection sensors were developed by using nucleases as signal amplification technology for protein biomarker detection. The main works are listed below:1. A Ternary Composite Based on Graphene, Hemin, and Gold Nanorods with High Catalytic Activity for the Detection of Cell-Surface Glycan ExpressionA novel graphene-family ternary composite with high catalytic activity has been developed by using simple synthetic methods. We have described a simple method with which to prepare a ternary composite(H-RGO-Au NRs) based on graphene, hemin, and gold nanorods. The system has high catalytic activity and was applied for the detection of glycan expression on the cell surface of K562 cancer cells. The graphene-based ternary composite has abundant positively charged Au NRs, which greatly improved the catalytic properties of the graphene-family of peroxidase mimetics, because of the high electron-transfer rate of graphene and the synergistic interaction of three components. Sensitive detection of glycan expression on K562 cell surface can be achieved with a low detection limit of 10 cells. This finding constitutes a novel graphene-family hybrid nanomaterials-based peroxidase mimetic that is expected to be applied widely in the construction of simple, sensitive, and selective biosensors for nucleic acids and proteins both inside and outside of cells through catalytic reaction of H2O2.2. Human serum biomarker detection based on a cascade signal amplification strategy by a DNA molecule machineA convenient method is presented that employs a DNA machine for protein biomarker detection. we present a convenient method that employs a DNA machine for the detection of PSA, which is a model of a serum protein biomarker. The designed method employs an amplification technique using an isothermal polymerization system and connects the target antigen concentration to the amount of Nb.BtSI that was modified on the surface of the electrode. The effect of amplification is noticeable and the detection limit is estimated to be improved by 400 times during the PSA antigen analysis compared to the method without employment of a DNA machine. This study provides a promising method that could realize most protein biomarker detections without the corresponding aptamers, using a DNA machine for signal amplification. A DNA molecule machine, based on an isothermal cycle reaction, was introduced for protein antigen detection to develop a simple but convenient sensing method for the model PSA antigen. The proposed biosensing approach avoids the complicated synthesis and inconsistency of nanomaterials, and also shows a great amplification effect. The method could also be applied for the detection of other antigens inhuman serum by simply changing the respective antibodies and it provides a smart sensing strategy for human serum protein detection in precise and microtrauma clinical diagnostics.