Super-fluorescent Gold Nanowires Constructed Via Self-assembly Strategies For Biological Enzyme Detection

Gold nanoclusters have excellent photoluminescence properties,biocompatibility and easy surface functionalization,and various preparation methods,mature synthesis techniques and wide application fields.It has great application prospects in the frontier fields of fluorescence sensing,analytical detection and bioimaging.However,in general,the fluorescence quantum yield of gold nanoclusters is not satisfactory,and the luminescence mechanism still needs to be investigated in depth,and the practical applications still need to be explored.Based on the above mentioned,this thesis optimized the synthesis process of gold nanoclusters based on their excellent comprehensive performance,and optimized the synthesis process of gold nanoclusters with the breakthrough point of improving the quantum yield based on the practical application requirements,and designed two highly sensitive and low-cost fluorescent nanosensors using gold nanoclusters as fluorescent probes,and explored their potential applications in biomedical analysis such as biological small molecules and biological enzyme activities,respectively.Details are as follows:（1）Self-assembly strategy for constructing high quantum yield gold nanowires and performance studyA novel fluorescent nanomaterial was firstly obtained by the reaction of a large excess of mercaptopropionic acid with chloroauric acid to obtain nonfluorescent gold clusters,and then a novel fluorescent nanomaterial was prepared using the coordination of zinc ions with the carboxylate in mercaptopropionic acid.The material has superb fluorescence properties with absolute quantum yields up to 32%.The fluorescent material was found by transmission and scanning electron microscopy to consist of homogeneous nanowires of micrometer length,and numerous nanowires were arranged in the same direction to form a bundle structure（AuNWs）.The AuNWs fluoresced blue-green under excitation light with a maximum emission peak at around 490 nm,and had good water solubility,optical stability and narrow pH response range（7.0-7.8）.（2）pH-responsive AuNWs-based fluorescent probes for urea and urease detectionAs a pH-sensitive fluorescent material,the decrease in fluorescence intensity of AuNWs in the range of 7.0-7.8 is linearly correlated with pH.Therefore,it can be used to design the measurement of enzyme-catalyzed reactions that can cause environmental pH changes.Based on this,we developed a simple and convenient"turn-off"type fluorescent nanosensor for the dual convenient and sensitive detection of urea and urease.Since urease catalyzes the hydrolysis of urea to carbon dioxide and ammonia,the pH of the solution increases,resulting in a sudden fluorescence inactivation of the system,so that the content of urea and urease can be quantified by the change of fluorescence intensity.Satisfactory results were obtained.（3）AuNWs fluorescent probes for acid phosphatase detectionA fluorescence sensing system for detecting ACP was designed using AuNWs stabilized under acidic conditions as a fluorescent probe as described above.When ATP was added to the AuNWs solution,the fluorescence signal of the AuNWs nanoprobe was reduced by the binding of ATP to Zn²⁺on the nanowire bundle.ACP can catalyze the hydrolysis of ATP and reduce the interaction force between Zn²⁺and AuNWs fluorescent probe,which enhances the fluorescence signal,and the sensitive detection of ACP can be achieved by the fluorescence intensity change of AuNWs.The detection range of this sensor is 0-0.4 U/L with an LOD of 0.01 U/L,and satisfactory results were obtained in the determination of human serum ACP content.