The Synthesis Of Fluorescent Probes Based On Carbon Dots And Their Application In Biosensing

Carbon dots?CDs?are nanocarbon materials that have been widely concerned in recent years and generally have a particle size of less than 10 nm.CDs have strong fluorescent properties and are capable of emitting fluorescence under excitation light.CDs show high biocompatibility and low cytotoxicity in scientific research.The synthesis process of CDs is very simple,easy to operate,and the quantum yield is high.Different synthetic methods can also make CDs emit different colors of fluorescence.Therefore,CDs have received great attention in the fields of biosensing,bioimaging,drug delivery,cancer treatment,and photocatalysis.However,CDs,as a single-signal fluorescent material,face two major problems in the process of biosensing:one is the lack of selectivity in biological detection,which limits their application;the second is Single-signal fluorescence output of CDs,which is inevitably disturbed by probe concentrations,light source,instrument efficiency and measurement conditions.This paper combined CDs with molecularly imprinted polymers?MIPs?for the detection of caffeic acid,which improved the selectivity of CDs as fluorescent probes,and a CDs-based ratiometric fluorescent probe was constructed for discriminative and highly sensitive detection of AChE and BChE in human whole blood,which overcomed the shortcomings of single signal output being susceptible to interference.The main research contents are as follows:1.Carbon dots coated with molecularly imprinted polymers for fluorescent determination of caffeic acid.We combined the photoluminescence properties of CDs with the selectivity of MIPs.The template molecule caffeic acid was imprinted on the surface of silane-functionalized CDs by sol-gel method in the presence of functional monomer APTES and crosslinker TEOS.Due to the electron transfer between caffeic acid and CDs,the fluorescence of the CDs was quenched.After elution of the template molecule,the fluorescence of the CDs is recovered,and the obtained CDs@MIPs were capable of specifically recognizing caffeic acid.When CDs@MIPs bonded with caffeic acid,the fluorescence would be quenched to detect the concentration of caffeic acid.2.A ratiometric fluorescence probe based on carbon dots for discriminative and highly sensitive detection of AChE and BChE in human whole blood.The fluorescence of APTES synthesized CDs at 460 nm was significantly quenched by the oxidization product of OPD oxidized by Cu²⁺due to inner filter effect,accompanied by a new emission peak at 570 nm.The AChE or BChE catalyzed hydrolysis reaction of AChE or BChE to generate thiocholine,whose sulfhydryl group strongly captured Cu²⁺,leading to the inhibition of oxidization of OPD,thus effectively preserving the natural fluorescence emission of CDs.The resulting fluorescence intensity ratio(F₄₆₀/F₅₇₀)could be served as the signal output for the sensitive and robust Cholinesterase activities sensing.Additionally,the inhibition of AChE or BChE in the presence of the corresponding inhibitor was also evaluated.Moreover,taking advantage of specific substrates and a selective BChE inhibitor Etho,the probe was successfully applied to simultaneously and discriminatively determining AChE and BChE in human whole blood.These results suggested that the proposed strategy provided a discriminative and sensitive analytical platform for cholinesterase clinical diagnostics and drug screening and enriches the detection methods for cholinesterase activity.