Construction And Applications Of Fluorescent Nano-biosensors Based On Quantum Dots And Metal Nanoclusters

Biosensor is an important branch of chemical sensor,which is developed by chemistry,physics,biology and electronics.Among them,fluorescent nano-biosensors have been widely used in the field of biological analysis due to their low toxicity,fast response,simple operation and high sensitivity.Nanomaterial technology is one of the fastest growing and most widely branched material technologies in the 21st century,and its vigorous development plays a crucial role in the construction of biosensors.Quantum dots,as a kind of fluorescent nanomaterials,have outstanding properties including tunable size-dependent emission,broad excitation peak,narrow and symmetrical emission peak and high quantum yields,which make them widely used in the field of biosensing.As a novel type of fluorescent nanomaterials,metal nanoclusters have the advantages of strong photostability,large Stokes shift,low toxicity,good biocompatibility,and simple synthesis strategy,which make them broadly used in fluorescence detection,genetic diagnosis and bioimaging.In this paper,based on the excellent fluorescence properties of quantum dots and metal nanoclusters,and taking the advantages of biosensors,we developed a series of fluorescent nano-biosensors and applied them in biological and analytical field for the detection of biological enzyme and gene.The main research contents are as follows:In the first chapter,we briefly introduce two kinds of fluorescent nanomaterials:quantum dots and metal nanoclusters,which are most widely used for the construction of fluorescent nano-biosensors.Their fluorescent properties,synthesis methods,and applications in biological and analytical field were discussed in detail.Furthermore,we elaborated the design principle and research significance of this paper.In the second chapter,red emissive Hg-Zn Se QDs were prepared by facile mixing of Hg²⁺and Zn Se QDs.Further,a ratio fluorometric technique was designed for the detection of alkaline phosphatase(ALP)based on in situ generation of Hg-Zn Se QDs and quinoxaline derivative.The linear ranges were 0.001-0.02 U L^-1 and 0.02-1.4 U L^-1 with a detection limit of 0.001 U L^-1.Furthermore,the nanoprobe exhibited satisfactory results for measuring ALP in human serum.In the third chapter,a highly sensitive fluorescent nanoprobe(ZIF-8@QDs)was constructed based on the assembly between QDs and ZIF-8 for selective determination of glutathione S-transferase(GST).The ZIF-8@QDs nanoprobe not only enhanced the fluorescence of QDs,but also had the advantages of ZIF-8 such as enrichment ability for the analytes,which largely improved the detection sensitivity of GST.The linear range was 0.05-1.2 m U L^-1 with a detection limit of 0.014 m U L^-1.The method was successfully applied to the detection of GST in human urine samples.In the fourth chapter,a sensitive ratio fluorescent biosensor was constructed based on in-situ generation of fluorescent copper nanoclusters on the DNA modified graphene quantum dots for the detection of HTLV-I gene.The linear range was 20 p M-12 n M with a detection limit of 10 p M.Furthermore,the method exhibited satisfactory results for monitoring HTLV-I gene in human serum.In the fifth chapter,we successfully designed a sensing system which combined the technologies of target DNA recycling amplification,magnetic separation,and in situ formation of copper nanoclusters(Cu NCs)for viral gene analysis.The linear range was 5 p M-5 n M with a detection limit of 1 p M.Moreover,the strategy was successfully used for the detection of viral gene in human urine and serum.In the sixth chapter,we presented a novel label-free and dual-mode sensing strategy for the quantitative detection of HPV based on the integration of DNA/Ag NCs and DNAzyme.The fluorimetry and colorimetry of the strategy displayed linear ranges of 0.01-4 and 0.02-4 n M,with the detection limit of 2.3 and 5.2 p M,respectively.Meanwhile,the sensing platform was used for the detection of HPV in different real samples,verifying the specificity and practicability of the strategy.In the seventh chapter,the contents of this paper were systematically summarized,and the future perspectives were seriously discussed.