Label-free Fluorescent Probes Based On Quantum Dots And Copper Nanoclusters And Their Applications In Glutathione Detection

Glutathione?GSH?is an important antioxidant in human body and plays crucial roles in basic biological functions.So far,it remains a challenge to develop convenient and reliable ways to quantify and monitor the changes of GSH levels.Quantum dots?QDs?,known as colloidal nanocrystalline semiconductors,possess many unique features such as broad absorption bands,size-dependent narrow,symmetric emission bands,high quantum yields and good photochemical stability.Therefore,QDs have been used extensively in the field of biosensing and bioimaging.As a class of metal nanoclusters,copper nanoclusters?Cu NCs?have similar optical properties with gold nanoclusters?Au NCs?and silver nanoclusters?Ag NCs?,such as high quantum yields,good photostability,ultrasmall size and good biocompatibility.Furthermore,copper is more abundant and cheap.Considering the excellent properties of QDs and Cu NCs,herein,we have constructed two label-free fluorescent probes for GSH detection.The research contents are as follows:1.A simple,sensitive and label-free fluorescence resonance energy transfer?FRET?based probe for GSH with MnO₂ nanosheets as energy acceptor and silica coated CdSe/ZnS quantum dots?QDs?as energy donor has been developed.The in situ synthesis of MnO₂ nanosheets allowed the formation of QDs@SiO₂@MnO₂ nanocomposites,and enabled the occurrence of FRET with the donor fluorescence was quenched.Upon the addition of GSH,MnO₂ nanosheets were decomposed and QDs@SiO₂ nanobeads were released with a remarkable recovery of the fluorescence intensity in a target-dependent manner.The established FRET probe showed excellent selectivity and sensitivity towards GSH,with the linear range of detection was divided into two parts:0-0.16 mmol/L and0.16-0.48 mmol/L,and the detection limit was 0.61?mol/L.The feasibility of the probe for GSH detection in complex matrix was further investigated by analyzing the content of GSH in reduced glutathione tablets.The results indicated the capability of the probe to detect low concentrations of GSH and suggested the practicability of the probe for GSH determination in real samples.And,it will provide new insights into the development of the combination of QDs with two-dimensional graphene analogues?2D-GAs?and promotes its further application in bioanalysis.2.By using poly?vinylpyrrolidone??PVP?as synthesis template and L-ascorbic acid as reducing agent,PVP supported copper nanoclusters?PVP-Cu NCs?has been synthesized in aqueous solution.Upon the addition of GSH,the fluorescence intensity of PVP-Cu NCs increased remarkably.It was found that the enhancement of PVP-Cu NCs fluorescence intensity was linear to the concentration of GSH,and thus,a simple,sensitive and label-free fluorescent probe for GSH was developed.The established fluorescent probe showed excellent selectivity and sensitivity towards GSH,with the linear range was determined to be 30 to 800?mol/L and the detection limit was calculated to be 1.2?mol/L.Fluorescence lifetime measurements indicated that the enhancement of PVP-Cu NCs fluorescence intensity may be resulted from the ligand exchange of PVP with GSH,for GSH can form more stable Cu-S bond with copper.The feasibility of the probe for GSH detection in complex matrix was further investigated by analyzing the content of GSH in reduced glutathione tablets and satisfying recoveries were obtained.The results of this work indicated the capability of this approach for GSH detection both in aqueous solutions and real samples.In addition,it should contribute to the studies of Cu NCs and promotes its application in biological systems.