Rapid Synthesis Of Protein Conjugated Gold Nanoclusters And Their Application In Tea Polyphenol Sensing

Gold nanoclusters are the new type of luminescent nanomaterials, with size approximately one nanometer. Compared with other nanoparticles, gold nanoclusters have their unique advantages, such as simple synthesis, stability, biocompatibility, optical stability and easy to preserve. It has been reported that gold nanoclusters have a wide range of applications in analytical testing, biomarkers, cell imaging, drug delivery and other aspects. Tea is a popular and healthy drink, which greatly attributed to its important component – tea polyphenols(TPs). Therefore, the detection of tea polyphenols in food and beverage companies is the important task. In this paper, we study about the catalase mimic activity of gold nanoclusters and developed a new photometric analysis method of polyphenols, and then implemented to detect tea polyphenols in the real tea samples.This thesis includes the following sections:The first part, concerns heating rapid synthesis of AuNCs-P-h. In this report, a rapid approach for the synthesis of protein conjugated gold nanoclusters under heating condition(AuNCs-protein(p)-heating(h)) was proposed. This method is very fast and easy. These AuNCs-p-h were synthesized within 3 min atapproximately 100 ?C and show red fluorescence under UV irradiation.The second part, the peroxidase-like activity of Au NCs-P-h. It has been reported, the traditional synthesized of BSA gold clusters having peroxidase-like activity. Through experimental study, we choose TMB as chromogenic substrate to verify that AuNCs-P-h also has peroxidase-like activity.The third part, the detection of tea polyphenols. Initially, our early experiments found that polyphenols can quench AuNCs-Ph, Nevertheless, tea polyphenols show a strong peak in the fluorescence spectra which interfere the detection of polyphenols. In the presence of tea polyphenols(TPs), the peroxidase activity of Au NCs-Ph was inhibited, which may be caused by aggregation of AuNCs-Ph allowing the develpement of a coloimetric detection method. This novel TP detecting method exhibits a linear response in the concentration range of 10 nM to10μM with detection limit of 10 nM. The approach also shows prominent selectivity towards various TP related molecules including tyrosol, protocatechuate, chlorogenicacid, theophylline, l-theanine, and l-norepinephrine hydrochloride. Comparing with the traditional tartaric acid colorimetric approach(TAC), this new system shows basically identical experimental results but with much higher sensitivity. AuNCs-p-h can be readily used for TP quantification from real tea samples. Thus, based on the inhibition of peroxidase activity, we propose a simple method for detection of tea polyphenols.The fourth part, we use this detection method to detect tea polyphenols in the real tea samples. In addition, we also compare this innovative and sensitive detection method with the traditional tartaric acid colorimetric method(TAC). The same samples were detected by using both methods, the experimental results are basically the same, but the method we proposed exhibits a higher sensitivity. Therefore, AuNCs-p-h can easily be applied to quantitative analysis of the actual content of polyphenols in tea samples.