Semiconductor Nanoparticles Biological Toxicity Analysis And Their Labeling And Detecting For The Selenium-containing RGDS

Quantum dots (QDs), also known as fluorescent semiconductor nanoparticles have been widely used as luminescent probes in biological and medical community because of their unique size-dependent optical and electronic properties. As QDs providing more and more positive nano-biological activity in biothchnological and cell-imaging applications, scientists begin to think much of their negative biological effects (called nano-toxicology) which is focus on studing the whole biological activities and the influence of nano material to physiological functions. C. elegans is an ideal model organism in laboratory to study the biological effects. It is easy to feed and its transparent epidermis can ease the process of observation. More important, it is a eukaryotic metazoan whose cells, molecular constructions and regulate pass ways are correspondent with higher animals. So the results gotten from C. elegans are possible to apply to human directly. Therefore, one purpose of this dissertation is to study the negative biological effects of the soluble CdTe nanoparticles and analyses their influence to organism with C. elegans as model organisms. A new method is established to evaluate the toxic effect of QDs, which may be used as a valuable quantitative analysis method to study negative nano-biological activities.GPX is a kind of protein containing selenium. It plays a key role in antioxidant defense system of enzymatic action. Thus it has very important perspective in drug development. However, due to the limitations associated with native GPX such as instability, limited cellular, accessibility, short half-lives, costs of production and big molecular weight, it is hard to be prepared extensively.The artificial mimic of GPX has provided a new method for the drug development of GPX. So the other purpose of this thesis is to synthesis seleno-RGDS, making use of RGDS which have application value in biology and iatrology. Then we applied the soluble CdTe nanoparticles as luminescent probes to label seleno-RGDS, and studied the status of conjugation in C. elegans.In Chapter 1, the unique optical properties of QDs and its preparation methods are introduced. The methods for QDs labeling biomolecules are summarized. The development and the trends of the QDs in biological and medical applications are generalized, specially introducing the applications in biological label. A description of C. elegans and several common methods in toxicology analysis are given too.In Chapter 2, we confirmed the ultraviolet absorption spectrum, fluorescence excitation and emission spectrum of CdTe nanoparticles emitting at 542 and 618 nm, and compared them with Rhodamine B which is one of the organic dyes. The CdTe nanoparticles showed unique optical and electronic properties, such as sharp emission spectrum with full width at half maximum (FWHM) as narrow as less 25 nm, large absorption coefficients across a wide spectral range and high levels of brightness and photostability. As compared with the broad excitation profiles and narrow, symmetric emission spectrum of CdTe nanoparticles, Rhodamine B has a discontinuous excitation and broad emission spectra. The different buffers have the effect on the stability of CdTe nanoparticles. CdTe nanoparticles emitting at 542 nm are more stable in water and PBS, while CdTe nanoparticles emitting at 618 nm are stable in Na2CO3 solution and water.In Chapter 3, we take the death rate of C. elegans as detecting object to study the toxic effect of soluble CdTe nanoparticles, comparing with RhB. Count the death number of C. elegans, and then calculate the LC50 of QDs and RhB by improved Karber's method. They are 0.85 mg/mL and 0.18 mg/mL. QDs shows lower toxic dose than RhB. Then we observe the influence of QDs and RhB to physiological movement, such as locomotory behavior, bodily growth and procreation ability. From the result we may see that QDs and RhB both influencethe physiological activity of C. elegans. But comparing with RhB, QDs with surface modification show huge superiority to fluorescent label biological molecule in organism. The most important, we grope a new way to evaluate the biological toxicity of semiconductor nanocrystals, establishing a foundation for analysing negative effect of nanoparticles.In Chapter 4, we successfully synthesized selenium containing RGDS as the functional mimics of GPX. The GPX activity of seleno-RGDS was determined to be about 3 U/μmol, making it possible to defense oxidation damage. Then we conjugated seleno-RGDS to CdTe nanoparticles through covalent bonding. The emission peak and full width at half maximum (FWHN) of QDs-SeRGDS are the same as single QDs, but the fluorescence intension increased remarkably. After characterized by agarose gel electrophoresis, they were used to culture C. elegans. Under the fluorescence microscope, we may see the red fluorescence of QDs in the vivo of C. elegans. This proved that making use of C. elegans to lucubrate the biological effect of Seleno-RGDS is possible.Sum up, our research analyzed the basic characteristic of different semiconductor nanoparticle; valued the biological toxicity of soluble CdTe nanoparticle with C. elegans, establishing a easy method to analyses the negative biological activities of QDs. Taking C. elegans as experiment model, we observed the status of the distributing and stability in vivo of the QDs and Seleno-RGDS conjugation.In our further work, we will focus on the study of Seleno-RGDS, especially the GPX activity. Combining with labeling technology of QDs, we may use C. elegans as model to investigate the biological effects of Seleno-RGDS. This selenium containing peptide maybe has great potential application value.