Preparation Of High-Stability Quantum Dots Materials And Applications In Preliminary Immunoassay

In recent years,quantum dots（QDs）have been widely used in biomedicine due to their unique photoelectric property.However,how to develop high-performance QDs materials with high chemsical and colloidal stability to realize rapid,reliable and accurate immunoassay is still a focus in current research field.Firstly,we prepared hydrophobic high-quality Cd_1-xZn_xSe_1-yS_y QDs and discussed the influence of reaction conditions on fluorescence property.Then,hydrophilic QD/SiO₂/Poly（EGDMA-co-MAA）was synthesized by distillation precipitation polymerization.We mainly studied its structure,fluorescence property,chemical and colloidal stability.QD/SiO₂/Poly（EGDMA-co-MAA）-based immunochromatographic test strip was established for HCG antigen detection.After that,QDs nanogel was synthesized with enzymatic oxidation cross-linking by reverse nano-precipitation method.We mainly studied its synthesis conditions,structure and morphology,fluorescence property and stability.At last,we developed a novel self-healing encapsulation method to prepare QDs encoded microsphere.Surface morphology,fluorescence intensity,QDs dispersibility,chemical stability and QDs leakage were studied.Moreover,QDs encoded microsphere was used for human IgG detection by flow cytometry.Major conclusions are as follows.（1）For preparing Cd_1-xZn_xSe_1-yS_y QDs,reaction temperature and precursor ratio had great influences on fluorescence property.Emission wavelength could be adjusted from 500⁶00 nm by changing precursor ratios.High-quality QDs with good chemical and photochemical stability were obtained when reaction temperature was 310 ℃ and reaction time was 600 s.（2）Hydropilic QD/SiO₂/Poly（EGDMA-co-MAA）with the particle size of about 63 nm and the quantum yield 34 % was synthesized.Moreover,it showed excellent chemical stability and colloidal stability in different pH aqueous solution over time due to the protection effect from double-layers core-shell structure.For early screening of tumour,it was successfully used to establish QDs immunochromatographic test strip and realized a rapid,accurate and sensitive detection for HCG antigen.（3）QDs nanogel with a diameter of about 180 nm and PDI=0.045 was prepared by reverse nano-precipitation method.Cry-TEM showed QDs nanogel was near-perfect sphere and QDs dispersed uniformly in nanogel.Enzymatic oxidation cross-linking had no obvious influence on fluorescence property.QDs could be all encapsuled into nanogel to realize precise synthesis.Meanwhile,QDs didn’t leak out from nanogel.This QDs nanogel had very low nonspecific protein adsorption and good colloid stability because of excellent hydrophilicity.Moreover,fluorescence intensity could’t be changed in a few days.QDs nanogel has great potential to be a high-performance QDs nanoprobe for immunoassay.（4）Compared with the traditional method,QDs encoded microsphere prepared by self-healing encapsulation method had much higher fluorescence intensity and chemical stability.QDs dispersed much more uniformly in microsphere.Moreover,QDs didn’t leak out from microsphere due to self-healing of pores.QDs encoded microspheres were successfully used for human Ig G detection based on sandwich immunoassay,which realized accurate and sensitive quantitative analysis.