Synthesis And Labeling Study Of Mannose Conjugated Gold Nanoclusters As Fluorescent Probe

Carbohydrate is not only the energy supply materials of living organisms,but also plays an important role in various biological processes such as cell communication,immunity,infection,development and fertilization through mutual recognition with receptor proteins.Therefore,the study of carbohydrate receptor interaction is of great significance for the study of life activities.In this study,the glycoconjugated fluorescent gold nanoclusters was designed and synthesized.We used this conjugate as a tool for studying of carbohydrate-receptor interactions.Firstly,the bovine serum albumin protected gold nanoclusters(BSA-AuNCs)was synthesized,by using 1,8-Diamino-3,6-dioxaoctane to modify the amino group on the surface of the gold nanoclusters.After that the amino-terminated gold nanoclusters(NH2-BSA-AuNCs)was obtained.Then the NH2-BSA-AuNCs were coupled with mannose through amidation reaction.Finally,the fluorescent mannose gold nanoclusters conjugated fluorescent probe(Man-BSA-AuNCs)was fabricationed.Subsequently,the molecular weight of the fluorescent probe was measured by matrix-assisted laser desorption ionization time-of-flight mass spectrometry(MALDI-TOF-MS),and the amount of surface coupled mannose was measured by phenol-sulfuric acid colorimetry.Fluorescence experiments show that the fluorescence probe with red fluorescence properties(λemission=742 nm,λexcitation=362 nm).Using scanning electron microscopy(SEM)observed that the grain size of the fluorescent probe is uniformly distributed between 1-10 nm.Next,the biological evaluation of the mannose gold nanocluster fluorescent probe was carried out.At the protein level,the fluorescent quenching experiment and the fluorescent competition experiment verified that the fluorescent probe can recognize the mannose receptor ConA.The fluorescence quenching experiment and the scanning electron microscope experiment of fluorescent probe and Escherichia coli K12 proved that the fluorescent probe can bind to the mannose receptor on the pili of Escherichia coli K12.The fluorescence labeling of human breast cancer cells(MCF-7)with this fluorescent probe at the cellular level in vitro was studied using an inverted fluorescence microscope.The above experimental results indicate that the mannose-gold nanocluster conjugate synthesized in this subject is a fluorescent probe with important application value,which can be used to study the sugar-receptor interaction,detect Escherichia coli K12 and image cancer cells.