Research Of Ultrasensitive Biosensor Of Concanavalin A Based On Single Au@Ag Nanocubes

Core/shell nanoparticles are highly functional materials with modified properties. Sometimes properties arising from either core or shell materials can be quite different. The properties can be modified by changing either the constituting materials or the core to shell ratio. Ultimately, particles show distinctive properties of the different materials employed together. This is especially true of the inherent ability to manipulate the surface functions to meet the diverse application requirements. The purpose of the coating on the core particle are many fold, such as surface modification, the ability to increase the functionality, stability, and dispersibility, controlled release of the core, reduction in consumption of precious materials, and so on. That is why Core/shell nanoparticles are gradually attracting more and more attention and these nanoparticles have emerged at the frontier between materials chemistry and many other fields, such as electronics, biomedical, pharmaceutical, optics, and catalysis. Based on this, We designed a ultrasensitive bio-sensor relying on the LSPR properties of Au@Ag nanocubes, and applied it to study the specific binding reaction betwenen the glycogen and protein reaction(mannose- ConA).(1) Gold and silver(Au@Ag) core-shell nanocube combining both the stability of gold nanoparticle and ultrasensitive property of silver nanoparticle, has excellent local surface plasmon resonance(LSPR) property. And subtle changes of the medium environment on the nanoparticle’s surface could lead to significant shift of LSPR scattering spectra. The spectroscopic and morphology properties of these nanoparticles were characterized by UV- fluorescence spectra, transmission electron microscopy( TEM), scanning electron microscopy( SEM).(2) We synthesized a mannose-derivatives by combining the water-soluble 2,2’-disulfanediyldiethanol and mannose, which contain a disulfide bond. The product can be modified to the metal and semiconductor materials such as Au, Ag, Cd surface through the covalent bond and can be combined specifically with Concanavalin A(ConA). The process of gold/silver nanoparticles modified with mannose-derivatives and the identification process between ConA and mannose, can be characterized under the dark field microscopy(DFM) by the significant shift(usually red shift) or image color changes of single nanoparticles’ LSPR spectrum by real-time.(3) At last, functionalized mannose was modified on the Au@Ag surface through Ag-S bond which could serve as a plasmon biosensor. Specific binding of Concanavalin A(ConA) and mannose on the surface of Au@Ag NC would induce to significant red-shift of the LSPR spectra. We had real-time monitor the specific binding process of mannose and ConA by LSPR spectra at a single particle level for the first time. And the results could be used for designing novel plasmon glycoprotein nano-biosensors with a low limit of detection up to 10 nM.