Preparation Of CdTe@SiO₂@PDA Nanocomposites For Ratiometric Fluorescence Analysis Of MicroRNA

A lot of researches have shown that the expression level of endogenous and noncoding micro RNA（mi RNA）as an important disease marker in human body is closely related to many high-risk and severe diseases.Since the first discovery of mi RNA,many detection methods for mi RNA have been developed.Among them,nano fluorescent probes have excellent advantages in selectivity,sensitivity and simple operation.So,they have developed rapidly in the detection of mi RNA and other disease markers.At present,a lot of fluorescent probes with application value have been developed.However,traditional mi RNA fluorescent probes often have some limitations in practical application,such as unstable single output signal,vulnerable to background interference,high production cost and so on.In this paper,a core-shell-shell nanocomposites was designed.Based on this,combined with the advantages of ratiometric probe and label-free fluorescent probe,a label-free ratiometric fluorescent probe was constructed for the analysis and application of mi RNA detection.The main work is as follows:1.Taking advantage of the strong and stable fluorescence of quantum dots（QDs）,the tunable emission wavelength,as well as the excellent biocompatibility,degradability and light transmittance of silica,Cd Te@SiO₂ nanoparticles were prepared and optimized.The adjustability of silica shell thickness by reverse microemulsion method and modified St（?）ber method was explored respectively.Finally,by controlling the addition of tetraethyl orthosilicate（TEOS）and aqueous ammonia in modified St（?）ber method,the silica layer thickness of Cd Te@SiO₂ was adjustable from 20 nm to 80 nm.Furthermore,based on the fluorescence quenching property of polydopamine（PDA）and its easily modified surface,a multifunctional core-shell-shell nanocomposites of Cd Te@SiO₂@PDA with adjustable fluorescence as well as modifiable surface was designed.Provide a basis for subsequent applications.2.Based on the advantages of adjustable fluorescence emission peak position,stable fluorescence intensity and easy surface modification of Cd Te@SiO₂@PDA nanocomposites,a label-free ratiometric fluorescence probe was designed.Using the fluorescence of Cd Te QDs as the Internal reference and the fluorescence of SYBR GreenⅠ（SGⅠ）as the output signal,an analysis strategy for mi RNA was established by using the fluorescence ratio of the two.Taking mi RNA-155 as the analysis model,the detection ability of the probe to target mi RNA was explored.It has good linearity in the range of 0.1 to 10 n M,and the LOD is 0.1n M.The analysis platform integrates the advantages of simple synthesis and easily available materials of label-free fluorescent probes,as well as the high signal reliability and reduced background interference of ratiometric fluorescent probes,which provides a new method for the analysis and detection of miRNA.