Development Of Novel Electrochemical DNA Biosensors Based On Nano-Materials

With improved understanding of structure and function of human gene, and the development of the Human Genome Project, DNA separation and analysis has taken a more and more important role in the areas of clinical diagnosis, medicine, epidemic prevention, environmental protection and bioengineering. Wide-scale genetic testing requires the development easy-to-use, fast, inexpensive, miniaturized devices. Many new biological technologies emerged and found their applications in this field. Among them, DNA biosensors are rapidly developed and have received considerable attentions. Such devices rely on the conversion of the DNA base-pair recognition event into a useful signal and offer a promising alternative for fast, cheap and simpler nucleic acid assays. Electrochemical biosensing of DNA hybridization is a novel and developing technique that combining biochemical, electrochemical, medical and electronic techniques with the advantages of being simple, reliable, cheap, sensitive and selective for genetic detection, and it can be compatible with DNA biochip. It is not only qualified for meeting the size, cost and power requirements of decentralized genetic testing but offers an elegant route for interfacing at the molecular level-the DNA recognition and signal transduction element. Therefore, they are expected to have a broad prospect of application in clinic examination of inherited diseases and drug screening.Nano-materials, with their size in the range of l~100nm, are currently under intense investigation owing to their special properties. Due to their small size, these materials exhibit quanta-size effect, small-size effect, surface effect and tunneling effect that differ from both their bulk material and the individual atoms from which they comprised. With these unique properties, they are widely used inthe fields of catalysis, optical absorption, medicine, magnetic medium, new materials synthesis and particularly attractive in biological applications.The goal of the present study is to design and optimize new DNA hybridization techniques with high sensitivity and selectivity. This dissertation focuses on fabricating novel electrochemical DNA biosensors by use of some kinds of nano-materials, thus developing a sensitive, sequence-specific and quantifiable gene detection method, and establishing the bases for application of electrochemical DNA biosensor to clinic diagnose. The high sensitivity of electrochemical device coupled to their compatibility with modern micro-fabrication technologies, portability, low cost, minimal power requirements, and independence of sample turbidity or optical pathway, made them excellent candidates for DNAbiochips. The dissertation includes five parts:The first part is the review of DNA biosensor.Firstly, we introduce the composition of a DNA biosensor and its classification; then briefly describe optical DNA biosensor and piezoelectric DNA biosensor. Secondly, emphatically review the operational principle, classification, application and development trends of electrochemical DNA biosensor. Immobilization method of ssDNA on electrode and signal conversion process are included. Advantages and disadvantages of electrochemical DNA biosensor were summarized. At last, nanoparticle-enhanced DNA biosensor and DNA biochip was introduced. While the use of DNA biosensors and DNA chip is at an early stage, such devices are expected to have an enormous effect on future DNA diagnostics.The second part to the fourth part are our research work focused on the fabrication of novel electrochemical biosensors.Electrochemical detection of DNA hybridization usually involves monitoringof a current response, resulting from the Watson-Crick base pair recognition event, under controlled potential conditions. The probe-coated electrode is commonly immersed into a solution of a target DNA whose nucleotide sequence is to be tested. When the target DNA contains a sequence which matches that of the probe, a hybrid duplex DNA is formed at the electrode surface. Such hybridization event is co...