| With the development of society, health problems have attracted more and more people’s attention. Cancer as a major fatal disease, seriously threats to people’s health. According to statistics, there are about 1.7 millions new cancer patients in China every year, but more than 80% of the early cancers can be cured. Therefore, early detection and early diagnosis of cancer cure are of decisive importance. Methods of the clinical diagnosis of tumors can be divided into physics, cytological and biochemical three categories. The physics and organizing cytology diagnosis method often can only detect the middle-late tumor; they are difficult to achieve the goal of early detection. Biochemical method is the detection of tumor specific genes produce proteins or molecular markers. But the use of biochemistry inspection method in clinical often cannot meet the testing purpose since the sensitivity is not enough high. Therefore, a rapid and sensitive method for detecting cancer markers is particularly important in the clinical research.In many detection methods, the photoelectrochemical detection method possesses the advantage of fluorescence detection and electrochemical detection at the same time, becomes a sensitive and promising detected method. The separation of the excitation signal and the detection signal make the measuring method become simple and higher sensitivity. Zn O nanomaterials have the characteristics of non-toxicity, biocompatibility and good chemical stability, which have been regarded as first choice of the electrode material to fix biological molecules in biological sensing. This paper focused on the combination of photoelectrochemical detection method with nano-zinc oxide materials. And quantum dots and enzymes were applied to the electrode to achieve a signal amplification of photocurrent, and highly sensitive photoelectrochemical immunosensor for AFP. Firstly, we designed two kinds of porous structure of Zn O nanomaterials as electrode of the sensor. Secondly, we improved the property of immunosensor in the aspect of enhancing photoelectric response and a low cost, simple detection, high sensitivity, wide linear range, good stability and repeatability photoelectrochemical sensor was obtained. Lastly, we compared the sensitivity of two kinds of structure of the sensor. The main work is as follows:(1) Firstly, we successful prepared the inverse opal structure of Zn O nanomaterials electrode by colloid self-assembly and sol-gel method in the FTO conductive glass surface. Secondly, Cd S QDs was prepared using the method of hydrothermal synthesis, which was connected with the AFP and GOD forming the complex. The AFP antibody and the AFP-Cd S-GOD complex were connected on through the specific immune principle. The sensor successfully applied to the detection of cancer markers-AFP. The narrow band gap of Cd S QDs will be connected to the electrode surface by immune combination, which effective energy level matching of conduction band between Cd S QDs and zinc oxide will broaden the scope of spectral absorption. And it is advantageous to accelerate the electronic transmission and reduce the recombination of electrons and holes, improving the photocatalytic efficiency and increasing the photocurrent effectively. At the same time, GOD catalyzed glucose to produce H2O2, which H2O2 could decompose and produce electron to fill into the valence band of Cd S QDs. Thereby, it reduced the recombination of electrons and holes to increase the photocurrent response. The experimental results show that the sensor for the detection of AFP has wide linear range: 0.1ng/ml-500ng/ml with the detection limit of 0.01ng/ml. This photoelectrochemical detection method greatly improves the performance of the sensor and shows excellent anti-interference performance and good stability.(2) First, Zn O electrodes of three-dimensional porous structure were prepared by combination electrostatic spinning and hot pressing technology in the FTO surface. We used the same principle in the previous work for the detection of cancer markers-AFP. We studied the three-dimensional porous structure constituted with one-dimensional nanometer fiber and the influence of the photocurrent caused by morphology and thickness of electrode. We realized the detection of AFP using the photoelectrochemical detecting method. The experimental results show that the sensor has a good linear range in 10ng/ml-500ng/ml with the detection limit of 4.6ng/ml.(3) Zn O nanometer electrodes of different microstructure using two different methods of prepared methods were studied. The inverse opal structure of Zn O electrode and the fiber porous structure of Zn O electrode were compared in the photoelectric response and detection sensitivity for detecting AFP. We preliminary concluded that the photocurrent response of the inverse opal structure of Zn O electrode is higher than one-dimensional nanometer fiber structure of Zn O electrode. Meanwhile, the inverse opal structure of Zn O electrode has a wider range and lower detection limit for detecting AFP. |
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