Preparation Of Nano-magnetic Polymer-coated Particles And Its Application In Study Of DNA Electrochemical Biosensor

Analytical chemistry face a new challenge with the development of life sciences. How to detect the trace bioactive substance from complex system has been a problem to our analyst. In the recent years, with the fast development of nanotechnology, nanometer material being applied to cell biology and molecular biology field, nano-magnetic functional materials have been show its great prospect owing to their particular advantages.This paper we prepared nano-magnetic polymer-coated particles which can covalently bound to the diverse bioactive substance such as cells, proteins and nucleic acid. The new electrochemical DNA hybridization biosensor was described that combined the highly sensitive and selective electrochemical detection techniques with the advantages of nano-magnetic particles. The new method offered great promise for ultrasensitive detection of DNA sequences. It would show wide applications in life sciences and medical studies.In chapter one, the systemic aspects, including the significance, structure, characteristic and prospect of magnetic microspheres were reviewed. The preparation of magnetic polymer microspheres, application in biological and medical field and the method of immobilizing active biology substance were described in detail. In addition, we proposed the protocol and planed this study briefly.On the basis of the former work, in chapter two, we studied the optimum conditions of preparation for magnetic microspheres. The carboxylate-modified magnetic nanoparticles and amino-modified magnetic nanoparticles were prepared successfully by dispersion polymerization. The fluorescent experiment with biological substance were qualitatively studied. The magnetic nanoparticles were found the following characteristic: super paramagnetism, narrow distribution of diameter, bounding to bioactive substance effectively.We studied electrochemical detection of DNA sequences using carboxylate-modified nano-magnetic particles in chapter three. The oligonucleotides were covalently immobilized on the nano-magnetic particles. The novel DNA probe of magnetic particlecan concentrate the trace amount of complementary DNA selectively from the sample solution onto the gold film electrode under a magnetic field. Differential pulse voltammetry (DPV) was used to detect DNA hybridization with an electroactive indicator which could bind to double stranded DNA. This new analytical assay offered the promise for rapid, low-cost, simplified detection. High sensitivity is achieved by coupling magnetic particle-based separation and electrochemical technology. The detection limit of complementary DNA is found to be 8.6 X 10 "10mol/L.In chapter four, a highly sensitive DNA biosensor was designed to detect DNA hybridization. This method is based on a magnetic DNA nano-enricher constructed with the target DNA were immobilized onto the surface of nano-magnetic particles, Ferrocenecarboxaldehyde labeled DNA probes were incubated with the magnetic nano-enricher, target DNA were captured with DNA probes containing a complementary sequence. Binding events were monitored by electrochemical signal of ferrocenecarboxaldehyde. The method also has the advantage of low-cost, simplified detection and high sensitivity.