Based On Graphene-type Nanomaterials Detection Of Biomarkers

Life science,as one of the most important scientific fields in today's,is closely related to human health and social development.Human attention and demand for health and environment-related aspects have also reached an unprecedented level.This puts forward higher demands on workers in areas such as scientific research and medical care,prompting researchers to make more in-depth and more accurate judgments and interpretations about life activities and related diseases,in the early diagnosis of disease,mainly related to the disease-related markers(nucleic acids?enzymes?proteins,etc.)for sensitive detection.Biosensor technology is widely used in biomedical?clinical diagnosis?food medicine and environmental monitoring because of its fast response?high detection sensitivity?good selectivity?simple operation and low cost.In recent years,nano-materials because of its unique optical and electrochemical properties,has become the current research focus,its application greatly for the development of biosensors provide a new way of thinking and vitality.Nanobiosensors constructed by nanomaterials and biosensors,involving cross-application including nanoscience?chemistry?biology and many other disciplines.Based on the emerging two-dimensional nanomaterials-graphene oxide and graphite carbon nitride,this paper developed a new nano-biosensor method to detect the disease-related markers-miRNA and tyrosinase activity.The main contents of the paper are summarized as follows:MicroRNAs(miRNAs)are a class of noncoding 23 nucleotides long single-stranded RNA molecules,in organisms,miRNAs regulate the gene expression,which promote mRNA degradation and translational repression by binding to the 3'-untranslated region of the target mRNA into a double strand.In recent years,the study found that changes in miRNAs expression levels are closely related to the development and progression of many diseases and cancers,and accurate detection of miRNAs allows us to better understand its role in cancer or cancer treatment.In Chapter 2,we combined the high fluorescence quenching capability of graphene oxide(GO)and its difference in the adsorption of single-stranded DNA and double-stranded DNA with target-recycling signal amplification assisted by duplex-specific nuclease(DSN),a new fluorescence assay for miRNAs determination was proposed.In the experiment,a fluorescent labeled DNA probe was designed,when the target miRNA was absent,the probe was quenched by GO adsorption.Once the target miRNA was added,one fragment of the probe labeled with the fluorophore can specifically recognize the target miRNA and hybridizes with it to form a DNA:RNA heteroduplex,the resulting duplex recognized by double-stranded specific nuclease(DSN),and the DNA was selectively cleaved into short oligonucleotide fragments,achieved fluorescence recovery of the fluorophore and produced a detectable fluorescence signal,the target miRNA is released and hybridized with the other DNA probe,thereby triggering the next round of cleavage,release and hybridization,and obtained a higher detection sensitivity for miRNA.The method proposed in this chapter has a detection limit of 197 fM and successfully used in cancer cell lysate detection of target miRNA.The method can be a potential tool for selective analysis of miRNAs(biomarkers)in cells or tissues and provide reliable information for early detection of miRNA-associated cancers.Graphite carbon nitride(g-C3N4)nanosheets,a new graphene-like two-dimensional carbon nanomaterials with graphite-like structures formed by sp2 hybridization of carbon atoms and nitrogen atoms have been widely used in the field of photocatalysis.In order to further broaden its application in the field of optical biosensing,in Chapter 3,we developed a novel biosensor based on g-C3N4 nanomaterials for the highly sensitive detection of tyrosinase(TYR)activity and its inhibitor.In this thesis,tyrosine was catalyzed by TYR to produce various melanin oligomers,and this melanin oligomer can be easily assembled on g-C3N4 nanosheets,and then gradually in situ growth of melanin-based polymers,and finally quenched the fluorescence of g-C3N4 nanosheet.In this thesis,the analysis of TYR activity with high sensitivity and high selectivity and the rapid screening of tyrosinase inhibitors were achieved by using the fluorescence properties of g-C3N4 nanosheets.Thus,the developed approach has established a new biosensor platform for early diagnosis of TYR-related diseases including melanoma and rapid screening of its inhibitors.