Microfluidic Synthesis Of ZnO/TiO₂ Composite Nanomaterials And The Application On Fluorescence Biodetection

In modern society,cancer is a major threat to people’s health and the detection of cancer biomarkers in early stage is crucial for early diagnosis and the increase of cure rate.Fluorescence immunoassay has been an important detection method in research and application due to its facile manipulation process,fast response and high efficiency.At the meantime,it is a significant trend to develop portable and miniaturized biosensors in order to accomplish Point-Of-Care Testing（POCT）.It is also an ideal device by integrating biodetection with the microfluidic devices with the advantage of high throughput,low cost and high integration.ZnO nanorods show significant fluorescence enhancement in biodetection and can be used in highly precision test owing to their high surface area and unique physical and chemical properties.To further optimize the sensitivity of biosensors,ZnO/TiO₂nanocomposites have been prepared in microfluidic devices and utilized for the detection of alpha fetoprotein（AFP）and carcinoembryonic antigen（CEA）.The main contents of the dissertation are as follows:1.ZnO/TiO₂ nanocomposites have been prepared and optimized.ZnO nanorods were synthesized by conventional hydrothermal method and TiO₂ sol was spin coated on ZnO nanorods to obtain final nanocomposites.The morphology and the fluorescence enhancement were investigated by spinning coating various layers of TiO₂ sol.It is revealed that one layer of TiO₂ sol can greatly enhanced fluorescence intensity when detecting FITC conjugated anti-bovine immunoglobulin G（FITC-anti IgG）.And then a microfluidic chip with multiple microchannels was designed and fabricated.Herein,ZnO nanorods were synthesized by conventional hydrothermal method on chip.The results show that the diameter,length and density of ZnO nanorods varied with the flow rate and growth time.In order to study the morphology and structure of ZnO nanorods,fluorescence detection of FITC-antiIgG was investigated.The results revealed that ZnO nanorods synthesized at the flow rate of 3.2?L/min for 1.5 h showed the optimized performance of fluorescence detection.Thus,the synthesis of ZnO/TiO₂nanocomposites was accomplished by perfusing TiO₂ sol（3 mg/mL）into microchannels with ZnO nanorod arrays synthesized in the above mentioned condition.The varied ZnO/TiO₂ nanocomposites were obtained by perfusing TiO₂ sol under different flow rates and coating time.FITC-antiIgG assay was also used to study the fluorescence enhancement on ZnO/TiO₂ nanocomposites of different morphology.Consequently,the maximum fluorescence enhancement can be observed on the ZnO/TiO₂ nanocomposites by perfusing TiO₂ sol at the rate of 1?l/min for 0.75 h.2.The detection of alpha fetoprotein（AFP）and carcinoembryonic antigen（CEA）were further performance on the optimized ZnO/TiO₂ nanocomposites.To optimize the parameter of fluorescence detection,we have investigated the exposure time when capturing fluorescent images.It’s revealed that the fluorescence images captured by the exposure time of 2 s showed the optimal performance.The fluorescence intensity showed linear correlation with the concentration of AFP antigens from 10 pg/mL to 1μg/mL and CEA antigens from 1 pg/mL to 1μg/mL.The limit of detection（LOD）of these two biomarkers was both as low as 10 fg/mL.Besides,the specificity of the immunoassay on ZnO/TiO₂ nanocomposites have examined.And all the results clarified that these ZnO/TiO₂ nanocomposites can not only be used for the detection of target proteins and also exhibited great detection performance.