Preparation, Characterization And Application Of Encoding Fluorescent Probe

Currently, the wide application prospect for encoding fluorescent nanoparticle as probes in molecular biology, cell biology, cell imaging, medical diagnostics, high-throughput drug screening and combinatorial chemistry synthesis has aroused great interest.Typically, the encoding fluorescent nanoparticle is comprised of two parts, fluorescent coding elements and micro/nano-carriers. Organic fluorescent molecules, fluorescent metal complexes and fluorescent semiconductor nanocrystals (also known as quantum dots) are the three most typical coding elements. Compared with traditional and mature organic fluorescent molecules and fluorescent metal complexes, quantum dots are bright, highly photostable and continuous excitation along with narrow symmetric, size-tunable fluorescence emission. The variety of QDs with different fluorescence colors can be excited by the same excitation. Therefore, QDs is an ideal fluorescent coding elements.Polystyrene particle and silica nanoparticle are the most common coding element vector. Among them, the SiO2 nanoparticles (SiO2 NPs) with the advantages of easy preparation and separation, surface modification, good hydrophilicity and biocompatibility is subject to much more researchers' attention. In recent years, many research groups at home and abroad controlled to assemble all kinds of fluorescent quantum dots, organic fluorescent dyes and metal complexes on the internal and surface of silica and polystyrene nanoparticles, and discussed the formation mechanism and structure of the corresponding particle, which is of great significance to the preparation and application of encoding fluorescent nanoparticle.Encoding fluorescent nanoparticle as a probe for the application of their research is based on its design, preparation and characterization. The encoding signal recognition of encoding fluorescent probes is through the control of the encoding elements concentration and concentration ratio in the nano-carrier to achieve the encoding of the fluorescent nanoparticle fluorescence emission intensity and fluorescence intensity ratio. At present, three major approaches are typically adopted to incorporate fluorescent encoding elements, such as organic dyes and QDs. In the first, the coding elements are encapsulated inside nano or microsized particles through electrostatic and hydrophobic interactions, covalent linkage, hydrogen bonding, and physical encapsulation. The second route is to directly assemble the coding elements on the external surface of spherical supports. In the third approach, the encoding elements are located in concentric shells surrounding a solid core or alternating with nonfluorescent spacer shells through layer-by-layer techniques. Although these approaches had been successfully prepared a variety of encoding fluorescent nanoparticles, but the preparation process was very complex. The use of metal ion-selective fluorescence quenching to quantum dots on the surface of encoding fluorescent precursors, the use of selective photolysis of fluorescent encoding precursors by different wavelengths and intensity light and other new coding technology enabled preparation of encoding fluorescent nanoparticle more simple, time-saving.In this paper, it reported the preparation of a series of encoding fluorescent nanoparticles based on the previous theories with the use of the red and green color CdTe QDs prepared in water-phase and organic fluorescent molecules doped. The experiments included the following components:(1) The preparation of green, orange and red color CdTe QDs had been improved. It proposed the preparation method of mercaptopropionic acid (MPA) capped CdTe QDs in the alkalescence precursor solution. It found that the preparation in the alkalescence precursor solution had better photoluminescence than in strong alkaline, and the growth of QDs particles was faster in green zone than red zone. It also discussed the concentration of Te precursor influenced on the preparation of CdTe QDs.(2) It reported the multi-step preparation of composite (SiO2-CdTe QDs)/SiO2 encoding fluorescent nanoparticle, which consisted of SiO2 nano-carrier with amino functional sueface, assembled green and red CdTe QDs shell, and the outermost layer of silica shell. The preparation of composite (SiO2-CdTe QDs)/SiO2 encoding fluorescent nanoparticle showed a good proportion of fluorescent signal had a potential application prospects.(3) Hybrid (FITC/SiO2-QDs)/SiO2 superstructure encoding fluorescent particle consist of FITC/SiO2 NPs, CdTe QDs shell and the outer silica shell had been prepared by multi-step. It showed a good double and distinguished fluorescent. It also reported a post-encoding process through quenching fluorescence of QDs in the hybrid (FITC/SiO2-QDs)/SiO2 superstructure encoding fluorescent particle by Cu2+, which was less time-consuming and more precisely encoding. Also, varities of hybrid (FITC/SiO2-QDs)/SiO2 superstructure encoding fluorescent particle can be prepared by changing other origanic dyes and QDs, and they as probes have potential prospects in biomedical application.