A High Sensitivity Of Quantum Dot-based Fluorescent Microspheres Immunochromatographic Preliminary Study

Quantum dots (QDs), also named semiconductor nanocrystals, are mainly composed of groupⅡ—ⅥorⅢ—Ⅴelements. Compared with conventional fluorophores, the nanoparticles have unique optical properties such as size tunable fluorescence and broad absorption spectra, narrow and symmetric emission spectra, strong fluorescence intensity and excellent anti-photobleaching property.The aqueous-compatible QDs show great potentials as a new type of probe material in various fields, such as cellular imaging, clinical diagnoses, environmental pollutant. Especially, in the field of food safety detection, because of the superior optical property, the QDs probe is expected to exceed GICA and be used to assemble a more sensitive rapid detection immuno-chromatography stripe.This study mainly focused on the following areas.1. The water-soluble CdTe QDs were synthesized for different refluxing time with MPA as stabilizer. Various reaction conditions that affected the optical properties of CdTe QDs were studied, including the time of reaction and the pH value. Furthermore, these nanoparticles were characterized by UV-Vis spectroscopy, fluorescence spectra and TEM. Purification method and stability were studied, it is found that dialysis was not suitable for purification of CdTe QDs and pH8-10 was conducive to the stability of CdTe QDs.2. The red-emitting CdTe QDs and mouse IgG were taken as the representative to study the conjugation behavior of QDs and antibody by a novel immunochromatographic method. After comparing to several methods, i.e., direct conjugation, EDC-mediated conjugation, NHS-mediated conjugation, EDC/NHS-mediated conjuation, 1-ethyl-3(3-dimethylaminopropyl) carbodiimides hydrochloride (EDC) and N-hydroxysulfo-succinimide (NHS) were selected together as coupling agents to conjugate QDs with antibody efficiently. The immunochromatographic strip was a superior method to study the conjugation of the fluorophore and antibody.3. In order to obtain a higher fluorescence intensity of the nanoparticles, two schemes. were applied:the first one, it is expected to add a shell to enhance the fluorescence intensity, that is, to prepare the core-shell QDs; the second one, in order to enhance the fluorescence intensity of a single nano-particles, the CdTe@SiO2 nanoparticles were prepared. However, the results showed that the fluorescence intensity of core-shell nanoparticles prepared in aqueous has not been improved at all and the fluorescence intensity of CdTe@SiO2 nanoparticles decreased significantly because of the impacts of reagents. Thus, the two protocols were all not suitable to improve the fluorescence property of the probe.4. The high-intensity nanoparticles SiO2/CdTe nanoparticles were prepared in this section. Firstly, the silica nanoparticles were prepared by reverse microemulsion mothed and stober mothed, then the nanoparticles were aminated with silane coupling agent APTES, and then amino-modified silica nanoparticles were conjugated with QDs to get the high-intensity nanoparticles.5. The immunochromatographic strip based on SiO2/CdTe nanoparticles was constructed by mouse IgG and goat-anti-mouse as the representative. After optimizing each part, compared with the GICA, the sensitivity of the detection system can be increased by 4-20 times.