The Preparation Of Biosensors Based On Nanotechnology

This thesis is divided into two parts, the first part is the ultra-sensitive detection of mercury ion based on T-Hg2+-T. The pollution of heavy metal ions, especially Hg2+, is increasingly serious. Due to the recognized accumulative and toxic characters in human body, and it cannot be degraded by the degradation methods which are commonly used, the trace detection of mercury ions is extremely important. Here two new types of mercury ions detection methods were designed based on combining DNA nanomachines and nano-materials.1. DNA is a new kind of bio-functional material and the design of DNA nanomachines brings a new concept to biological analysis. Though some novel approaches for the detection of heavy metal ions based on the DNA-metal coordination chemistry were developed. In this study, a bio-barcode DNAmachine was designed based on T-Hg2+-T coordination chemistry and fluorescence detection. The Klenow polymerase was driving the reaction, which was with DNA as a template and dNTP as a substrate carried out continuously, and achieved signal amplification ultimately. Under the optimum conditions, a good linear relationship with the concentration of Hg2+ion from1.0×10-8mol·L-1to1.0×10-6mol·L-1and detection limits as low as2.2×10-9mol·L-1(3σ) were achieved. As a promising biomolecular device, this DNA machine may have an even broader application in the rapidly developing field of nano-biotechnology for other metal ions detection.2. A novel highly sensitive electrochemiluminescence (ECL) detection protocol of mercury(Ⅱ) ions was developed, which was based on strong and stable T-Hg2+-T coordination chemistry and DNA-linked luminol-Au NPs superstructure cooperated with APS as the enhancer in this study. In this experiment, the Luminpl-capped AuNPs were synthesized, based on Iuminol-reduced gold nanoparticles. Thiolated-modified DNA were readily immobilized on the luminol-Au NPs via Au-SH chemistry, then the DNA-linked luminol-Au NPs superstructure was formed through DNA strand hybrid. Under the optimum conditions, a good linear relationship with the concentration of Hg2+ion from2.0×10-10mol·L-1to2.0×10-8mol·L-1and the detection limits as low as1.05×10-10mol·L-1(3σ) were achieved.Secondly, the electrochemical sensor for the detection of AFP based on nanomaterials was prepared.A novel AFP immunosensor was designed by sandwich method, which was based on the good biological affinity of the Au nanoparticles and carbon nanotubes. In the experiment, the carboxyl functionalized carbon nanotubes were immobilized on the surface of the glassy carbon electrode, and via covalent bond. The Ab2and HRP were modified on the surface of AuNPs to form HRP-Au-Ab2. According to the property that HRP can catalyze hydrogen peroxide oxidation of o-aminophenol, differential pulse voltammetry (DPV) was used as a mean to achieve the detection of AFP. Under the optimum conditions, a good linear relationship with the concentration of AFP from1ng mL-1to200ng·mL-1and the detection limits as low as0.29ng·mL-1(3σ) were achieved.