Reaction Between Quantum Dots-Bromelain And Fibrinogen And A Novel Method For Determination Sudan Dyes In Foods

The thesis is divided into two portions: one is a study of the reaction between Quantum Dots-Bromelain and Fibrinogen;the other is a novel detection methods of Sudan dyes in hot chilli products.In part 1, for detection the process of reaction between Bromelain and Fibrinogen, CdTe nanopaticles synthesized in aqueous solution were used to label Bromelain in order to form CdTe-Bromelain. The fluorescence spectrum were used to detect the reaction process between CdTe-Bromelain and Fibrinogen.In the chapter 1,the synthesizing methods of QDs and its considerable asvantages are introduced.Especially,its current usage and studying in the aspect of biological and medical community are reviewed.In the same time, the usage and studying of Bromelain were introduced in pharmaceutical.In the chapter 2,CdTe nanoparticles was synthesized in aqueous solution using mercaptopropinic acid(MPA) as the stabilizer.CdTe nanoparticles were effectively bound to positively charge protein,Bromelain via electrostatic interaction at a certain pH value.Compared with the free QDs, the absorption spectrum of CdTe-Bromelain bioconjugates was flatter in 400～600nm and the emission peak of the bioconjugates underwent a red shift 8nm,but the intrinsic spectral width was unchanged.The emission peak of the Bromelain is at 340nm,However,CdTe nonaparticles is at 550nm,thus,the emission peak of CdTe nanoparticles can not be interfered by Bromelain.Finally,the reaction was monitored via changing of the emission spectrum between CdTe-Bromelain and Fibrinogen.The experimental results show that the emission spectrum is gradual blue-shift and the fluorescence intensity declines gradually with the increase of time.Besides those, it is necessary to conside the effect of CdTe nanoparticles on the enzymic activity of Bromelain after the conjugation.F.I.P.experimental results show that the QDs- Bromelain bioconjugates preserve the biological activity of Bromelain.It is calculated that 77.5% of the original enzymic activity is retained.In portion 2, a novel detection methods for determination Sudan dyes in hot chilli products by microwave-assisted extraction (MAE) and high performance liquid chromatography(HPLC) were developed.In the chapter 1,the pollution in food and its toxicity to human being were discussed. It is also reviewed that the sample containing food additive were technique of preparation and methods of detection.The key is that the origin of Sudan dyes and its toxicity to humane being were introducted.In the chapter 2,Microwave-assisted extraction (MAE)combined with high performance liquid chromatography- ultraviole(HPLC-UV) detection has been employed to the quantitative analysis of SudanⅠ,SudanⅡ,SudanⅢand SudanⅣin hot chilli products. The main parameters of effect the extraction efficiency,such as extraction solvent,irradiation time and temperature,were optimized.The optimized extraction condition were that the methanol was used as extraction solvent and the extraction was performed at 100℃for 6min.The separation was achieved in the isocratic mode with mobile phase of methanol-water(V/V,90/10) at 1mL/min of a flow rate and column temperature is 35℃.The proposed methods was appled to analysis of hot chilli sauce,hot chilli oil and hot chilli tomato sauce with Sudan dyes.The limit of detection(LOD) and the limit of quantitation (LQD) of SudanⅠ,SudanⅡ,SudanⅢand SudanⅣwere 0.013,0.020,0.039,0.042μg/mL and 0.040,0.062,0.128,0.130μg/mL, repectively .Recoveries of Sudan dyes are in the range of86-99% for hot chilli sauce and hot chillic tomato sauce,84-96% for hot oil,and and the relative standard deviations of the quantitative results are from 1.3-10.03% in hot chilli sauce and hot chilli tomato sauce, 1.86-11.33% in hot chilli oil.