Study On The Fluorescence Biosensor Based On Graphene Oxide And Lead Sulphide Nanoparticles

Nanomaterial has a surface effect, small size effect, quantum size effect andmacroscopic quantum tunneling effect. Since the1980s, the science of nanomaterialhas changed fundamentally, and continue to penetrate in other disciplines and fields,led to many research areas and hot spots continue to emerge, has been widely used inmany fields of physics, chemistry, etc. Nanomaterials and nanotechnology wererecognized as one of the most promising areas of research of the21st century.Nanoparticles with organisms exactly have a close relationship: the components’ sizeof biological body is generally in the5-200nm range, which marks the nano-biology atthe nanometer scale range to understand the structure of biological macromoleculesand their functional relationships. In recent years, nano technology and bio-sensingtechnology, has injected new vitality into the development of nanoscience.Protein is one of the most basic material of organisms, and closely related to theorigin and evolution of life, material operation and heredity. The concentration ofvarious proteins in the human body directly related to the body’s metabolism, andbecoming a disease mark for discrimination and diagnosis. Therefore, it is of greatsignificance to create a simple, fast, sensitive, practical protein detection method forpharmaceutical research, medical research, clinical diagnosis and treatment.As the melamine is difficult to metabolites, it can cause calculus of kidney andinduce bladder and urinary system diseases. Thus, it must pay more attention to controlthe use of melamine. However, melamine detection methods have some drawbacks,such as needing of large instruments, testing costs, and operating complex andtime-consuming, so that the development of new, high sensitivity, good specificitydetection of melamine appears particularly important.This research will be the combination of the two kinds of nanomaterials （thegraphene oxide and PbS nanoparticles） and bio-sensor technology, with the purpose tobuild a new type of biosensor. Pointing at the focal point of the development ofanalytical chemical and medical examination for the current analysis, we designedanovel sensor method and signal amplification mode, with the purpose of proposing ofthe high sensitivity of fluorescent sensors to detect a variety of living matter. We useFluorescence analysis, immunoassay, chemical and biological sensing technology todetect human IgG, DNA methylase, melamine and other disease markers, proteins and small molecules. In this way, it provided new simple practilal methods for fast andaccurate diagnosis of genetic diseases, epidemics on-site screening and populationcontrol, environmental monitoring, food safety testing and research.（1）A fluorescence method for methylase detection based on grapheme oxide hasbeen developed in Chapter2. Briefly, the oligonucleotide probe （hairpin probe） thatcan be methylated totally if DamMTase. The specific sites of the hairpin probes weresplited by the the restriction endonuclease Dpnâ… . Then, the ssDNA that markingfluorophor FAM were released out, because the ssDNA can be adsorbed on the surfaceof GO, lead to the quench of fluorophor FAM, dsDNA can not. As a result, the activityof methylase has been detected. This method has the advantages of high sensitivity andaccuracy. Besides, it is also a rapid and convenient method.（2）A fluorescence biosensor for melamine detection based on grapheme oxide hasbeen studied in Chapter3. Basically, a oligonucleotide probe labeled with afluorophore on one end has been designed. This oligonucleotide probe was constitutedwith24thymines. In the presence of melamine, the oligonucleotide probe will combinewith thymines and conjugates with T-melamine-T were formed. The reason is thessDNA can be adsorbed on the surface of GO, lead to the quench of fluorophor FAM,but dsDNA can not. It will cause the huge change of fluorescence signal. The mainadvantage of the method were high sensitivity, rapidity and high selectivity.（3） In Chapter4, we design a novel fluorescence-immune immunosensor for thedetection of human IgG using Pb²⁺DNAzyme. On one hand, goat anti-human IgG werefixed on the surface of polystyrene microplates, then binding PbS quantum dots labledwith goat anti-human IgG through immune sandwith reaction in the presence of humanIgG. Then nitric acid was added to dissolve PbS quantum dots, make sure that thePb²⁺released completely and get Pb²⁺sample. On the other hand, Pb²⁺DNAzyme wascombined containing a fluorophor and a quencher and cause fluorescence quenching.In the presence of Pb²⁺sample, the DNAzyme was splited and ssDNA was released,leading the recover of fluorescence signal.