Preparation Of Transferrin-based/H~+ Modified Gold Nanoclusters And Their Multifunctional Applications

Gold nanoclusters?AuNCs?with ultra-small size consist of several to hundreds of gold atoms,which have the several advantages,such as long fluorescence lifetime,large Stokes shift,low toxicity and easy chemical modification.These excellent properties make AuNCs potential applications in the detection of environmental contaminant and biological samples,cell imaging and biomedical treatment.In this paper,two kinds of red fluorescent gold nanoclusters were synthesized.One is using a biocompatible transferrin?Tf?as a template;The other is H⁺modified gold nanoclusters?AuNCs@EW/H⁺?based on the gold nanoclusters protected by egg white?AuNCs@EW?,The applications involve the determine of ions,cell imaging,tumor cell recognition and encryption/decryption of information.The main works include four contents:1.Using Tf as both reducing agent and stabilizer under alkaline conditions of pH 12,AuNCs@Tf(?_ex=410 nm,?_em=640 nm)of strong red fluorescence was synthesized by reacting for 1 h in a microwave reactor.At the same time,AuNCs@Tf was characterized by a series of test instruments including Fourier Infrared Spectroscopy?FTIR?,Transmission Electron Microscopy?TEM?,X-ray Photoelectron Spectroscopy?XPS?,Malvern Particle Size Analyzer?DLS?,X-ray Diffractometer?XRD?and laser confocal microscopy?LSCM?.The results show that AuNCs@Tf is spherical,the average size is about 4-7 nm.In addition,AuNCs@Tf has a face-centered cubic structure?fcc?and can co-localize with lysosomes in the cells.2.Due to the strong red fluorescence of AuNCs@Tf,a Cu²⁺-mediated ON-OFF-ON switch was developed.In the presence of Cu²⁺,the fluorescence of AuNCs@Tf was quenched due to the formation of the AuNCs@Tf-Cu²⁺complex.The addition of glutathione?GSH?restores the fluorescence of the AuNCs@Tf-Cu²⁺because of the higher binding of GSH to Cu²⁺.Based on this mechanism,quantitative evaluation of GSH can be achieved.Moreover,the lysosomal environment of tumor cells is rich in endogenous GSH in compared to normal cells,so that the AuNCs@Tf-Cu²⁺system can illuminate tumor cells rather than normal cells,resulting in successfully applying to cancer cell recognition,which implied its great potential application in cancer diagnosis.In addition,the AuNCs@Tf was also applied to Cu²⁺strips and encryption/decryption of information.3.H⁺modified gold nanoclusters?AuNCs@EW/H⁺?with strong red fluorescence were obtained by the addition of H⁺to AuNCs@EW through microwave assisted method.AuNCs@EW/H⁺was characterized by UV spectrometer,fluorescence spectrometer,FTIR,TEM,DLS and XRD.The results show that AuNCs@EW/H⁺has strong absorption at 280 nm.Under the 380 nm excitation,AuNCs@EW/H⁺has a maximum fluorescent emission peak at 640 nm.The shape of AuNCs@EW/H⁺is approximately spherical,and a phenomenon of agglomeration appears.The average size of approximately 170-330 nm and a Zeta potential of approximately 20 mV,providing excellent light stability over a wide pH range.4.The application of AuNCs@EW/H⁺in the specific sense of cationic Fe³⁺and anion NO₂^-was determined and the detection limits of Fe³⁺and NO₂^-were calculated to be 1.4 nM and 2.83 nM,respectively.The content of NO₂^-in various meat products from supermarket in Taiyuan city was examined and applied to the actual situation,contributing to the prevention of diseases related to nitrite.Moreover,AuNCs@EW/H⁺can also be used for cell imaging.