| Quantum dots (QDs) are semiconductor nanocrystals, comprising elements from the periodic groups II-VI or III-V, which is close to or smaller than the dimensions of the exciton Bohr radius. They are roughly spherical and with sizes typically in the range 2–6 nanometer (nm) in diameter. As a result of quantum confinement, they endowed with unique optical and electronic properties unlike the bulk material, such as broad excitation spectra, narrow symmetric, and tunable emission spectra in comparison with conventional organic fluorescent dyes. As nanoparticles, QDs possess controllable surface properties, are comparable to the size of micro-molecular(nucleic acid, proteins)(2-6 nm), and thus could serve to deliver biomolecules and other exogenous drug compounds to cellular targets, which indicates their applicability as novel fluorophores for biological imaging. How to improve the synthesis method and technique of quantum dots? How to improve the quality of quantum dots and perfect the crystal properties? The ways to improve the quantum dots for their future application in biological and medical science are our aim targets as well.In this paper, we have synthesized high quality of soluble CdTe quantum dots, and modify it with silica and polymers, which realize the enrichment of the fluorescence. Furthermore, we have also applied the quantum dots as fluorescence prober in enzyme and the examine of lyme disease. The works we have done are presented as follows:1) Microwave synthesis of CdTe quantum dots. High quality CdTe quantum dots was synthesized by microwave. XRD shows that the CdTe has a cubic zinc blend crystalline structure, and the TEM image shows that individual particles have the size of 2-5 nm. Also the CdTe display good water solubility, and no obvious precipitation is observed. 2) Quantum dot-based pH probe for quick study of enzyme reaction kinetics.It is known that QDs are pH sensitive. In the present study, it is observed that the FL intensity of QDs linearly decreases by 90% with pH deceasing from 8.0 to 5.0. The restoration of the FL intensity of QDs cannot be achieved by adding OH?. It may suggest that the fluorescence quenching by H+ is irreversibly. The possible explanation may be that not all particles of QDs are perfectly capped with the shell and the added H+ can pass through the shell layer and interact with the core. Therefore, part of QD particles may be destroyed by the added H+. It is also found that Te is separated out from solution, when abundant H+ is added to the QDs solution. PNP is widely used as pH probe for monitoring the releasing of protons during the ester hydrolysis. However, there are some disadvantages for PNP as pH probe, it is unstable. When PNP is incubated in a buffer with a fixed ionic strength, the OD value of PNP persistent varies at either low or high ionic strength, he reaction rate could only be correctly monitored for UV detection when OD value is lower than 1. However, no such limit is observed for QDs. When exceeding 10 min, PNP is almost depleted and the reaction rate could not be detected correctly. On the other hand, QDs can be used to detect the reaction rate correctly even exceeds 15 min with the high concentration of substrate. It suggests that ODs has a wider monitoring range than PNP.3) The CdTe quantum dots has been conjugate to Borrelia burgdorferi. This is the first time apply CdTe quantum dots in fluorescence immno-analysis Borrelia burgdorferi. QDs may find practical application for the detection of pathogens and toxins, and in defining their characteristics, including virulence. QDs also have a long fluorescent lifetime after excitation, which may be taken advantage of in time-gated imaging. After conjugate CdTe quantum dots to the Borrelia burgdorferi two days, we can observe glealy Borrelia burgdorferi with high activity under fluorescence microscope. Compare to normal image technology, imaging with quantum dots has better the signal-to-noise ratio,which maybe useful in the determination of lyme disease nosogenesis and Borrelia burgdorferi overgrow progress.4) The synthesis of CdTe@SiO2 particles and the application of it in immunoassay and diagnosis of lyme disease.Uniform biocompatible CdTe@SiO2 nanoparticles were obtained using a reverse microemulsion, and the silica shell prevents flocculation of particles and species from adsorbing onto the surface, and help to maintain the photoluminescence. Silanol groups can be functionalized through different procedures. The hydroxyl group can react with various compounds to form amine, carboxyl, or thiol groups. Passive adsorption of molecules such as avidin is also commonly used. The versatility of silica in synthesis aspects as well as surface modifications offer a great advantage to the use of the material in bioanalysis. Furthermore, we can incode different quantity or different color quantum dots in one silica particles, to form the ptical spectral code, which is the perfect biomarker for multi-parameter and multi-virus. Borrelia burgdorferi were successfully conjugated to the fluorescent particles by the reaction of avidin and biotin, which were confirmed by fluorescence spectra. We found that the CdTe@SiO2 particles appear to down shift or"blue"shift their fluorescence emission by 150 nm or more when conjugated to antiserum, which were then bound to the surfaces of lyme disease spirochaete. This may be due to that the morphology of Borrelia burgdorferi transform from stripy into globosity (ovoid), after the formation of the CdTe@SiO2 particles/antiserum/Borrelia burgdorferi. While the CdTe@SiO2 particles were encapsulated in/on the"globosity", as the increase of quantity of the Borrelia burgdorferi, the size or shape of the globosity changed, resulting in shifting of the fluorescence emission wavelength of the CdTe@SiO2 particles. Regardless of the mechanism, these remarkable fluorescence emission wavelength shifts may suggest new detection methord to the detection and possible quantitation of Borrelia burgdorferi.5) The synthesis of PAMAM, which is applied in the modification of CdTe quantum dots, furthermore using the PAMAM as drug carriers. The PAMAM polymers possess a large number of primary and tertiary amine groups at the surface and in the interior branches of the molecule, which can graft to quantum dot surfaces, while additionally improving the fluorescent properties of the modified semiconductor nanoparticles. the CdTe quantum dots is actived by EDC and NHS, which can strengthened the conjugation of PAMAM and CdTe quantum dots, and reduce the releasing of CdTe from the complex.Dendrimers are versatile, derivatisable, well-defined, compartmentalised chemical polymers, with emphasis on the biocompatibility, such as in vitro and in vivo cytotoxicity, as well as biopermeability, biostability and immunogenicity. As PAMAM can easily excrete from body through urine and feces, make it an idea drug carrier in delivery systems.The aim of the present work wasto investigate the potential of PAMAM dendrimers as solubility enhancers of sulfonamides as exemplified by aspirin, study the effect of concentration and generation(1G to 3G) on the solubility of asiprin.6) The synthesis of PMMA/CdTe quantum dots complex, and the pilot study of its property. The PMMA/CdTe complex is obtained in situ synthesized, with kindly optical property, which has also successfully avoided the FRET between PMMA and CdTe quantum dots. But there is obvious precipitation, how to optimize experiment condition, how to get lesser diameter and distributing uniformity particles, requires further investigation.
|
PDF Full Text Request