| At present, nano-material displays an amazing potential in almost every areas because of its unique physical and chemical properties. With the reduction of production costs and the continuous development of new technologies, more and more nano-materials come into people's lives, but reports of the toxicity of nano-materials emerge followed. In recent years, numbers of studies show that nanoscale substances have potential biological risk. They can travel through the blood-brain, blood-testis and other natural barriers, and do harm to human health through a variety of ways, such as breathing, skin contact, esophagus, injections.Protein and DNA are important material fundations of life activities and major component of living organisms. Various toxic and harmful substances come into human bodies often interact with these biological macromolecules to show their harmfulness. Therefore, study the interaction between nanoparticles and biological macromolecules (such as proteins, DNA) at functional macrobiomolecular level, research the influence of nanoparticles on biological macromoleculars'structure and function will provide important references about the toxicity of nanomaterials on the body and will have significant implications on establish new and reliable evaluation method of nanoparticles toxicity. Also, these researches are propitious to the widely use of nano-materials.In this paper, we studied the toxicity mechanism of CdTe quantum dots and nano TiO2 targeted to bovine serum albumin (BSA) and calf thymus DNA (ctDNA) in molecule level by the methods of fluorescence spectroscopy, ultraviolet-visible (UV-vis) absorption spectroscopy, circular dichroism (CD) spectroscopy and resonance light scattering (RLS) spectroscopy. And the correlation of spectroscopy signals and the toxic effect of nanoparticals to BSA and ctDNA was studied. The dissertation consists of the following three parts.In the first part, the biological toxicity of CdTe quantum dots (QDs) to bovine serum albumin (BSA) has been investigated mainly by fluorescence spectra, UV-vis absorption spectra and circular dichroism (CD) under simulative physiological conditions. Fluorescence data revealed that the quenching mechanism of BSA by CdTe QDs was a static quenching process and the binding constant is 6.05×103 and the number of binding sites is 0.7938. The thermodynamic parameters (ΔH=-62.33 kJ mol-1,ΔG=-21.21 kJ mol-1,andΔS=-140.3 J mol-1 s-1) indicate that hydrogen bonds and van derWaals forces between the protein and the QDs are the main binding forces stabilizing the complex. In addition, UV-vis and CD results showed that the addition of CdTe QDs changed the conformation of BSA.In the second part, utilizing fluorescence spectroscopy, ultraviolet-visible (UV-vis) absorption spectroscopy, circular dichroism (CD) spectroscopy and resonance light scattering (RLS) spectroscopy techniques, the toxic effects of CdTe QDs modified with glutathione to BSA and ctDNA was studied in the molecular level. Research shows that the interaction modes of CdTe QDs modified with glutathione and mercaptoacetic acid to BSA is similar, but the former is more instable, when it caused the loose of BSA skeleton, its fluorescence activity was reduced. In addition, we evaluated the gene toxicity of CdTe QDs by using the fluorescence quenching intensity (Fo/F) of ctDNA to CdTe QDs. The result showed that CdTe QDs mainly combined with external phosphate of ctDNA, and the fluorescence quenching mode of ctDNA to CdTe QDs is static quenching. The addition of CdTe QDs can cause conformational change of ctDNA, and has the strongest genotoxicity interaction intensity at the concentration of 5.0×10-7 mol L-1 and pH 8.In the third part, the environmental toxic behavior of nano TiO2 to BSA was examined by using resonance light scattering (RLS) spectroscopy, fluorescence spectroscopy, ultraviolet-visible (UV-vis) absorption spectroscopy and circular dichroism (CD) spectroscopy techniques in vitro. The RLS result shows that nano TiO2 and BSA can aggregate together, making the particle size increase, and the RLS intensity stronger. By nanlyzing the foourescence spectrum of the system, we found that the fluorescence intensity of BSA at the emission peak (λmax=340 nm) decreased regularly when nano TiO2 were added. First of all, this quenching is due to the addition of nano TiO2 change the microenvironment of BSA, and cause its skeleton structure loose, the fluorescent group exposed to hydrophilic environment; at the same time, nano TiO2 can interact with try of BSA and quench its fluorescence intensity. UV absorption spectra and circular dichroism spectra results further confirmed this conclusion.The results of our study indicate that after nano-materials came into the body, they can not only affect the carrier protein conformation, but also interact with the genetic material DNA, thus showing its genotoxicity. This conclusion provides a basis to the evaluation of biological toxicity of nanoparticles at functional macrobiomolecular level.
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