Construction Of Ultrasensitive Electrochemical Biosensor For The Detection Of α2,6-Sialyted Glycans

The concept of biosensor was originated from the glucose biosensor which was firstly reported by Clark and his coworkers in the 1960s. The proposed biosensor was fabricated for the detection of glucose through the combination of glucose oxidase and oxygen electrode. Afterwards, the studies on biosensors have attracted wide attention and great interests. Now biosensors have developed to be a newly-interdisciplinary covering biology, medical science and electronics. The detection of bioactive substances can be achieved by the recognition of biological molecules and then the signal would be transferred into sound, light, electricity and other signals. Biosensors are of great value in food safety, life science, medicine, military and environmental monitoring, owing to their high sensitivity and selectivity, low-cost, rapid response, easily operating, continues detection and easy to be miniaturized and automated.For biosensor, it is important to select appropriate materials to improve its performance. As the development of science technology and the successive appearance of novel materials, the performance of the biosensor has been consecutively improved. Nanomaterials have attracted great interests owing to its unique properties, such as excellent conductivity and biological compatibility. Additionally, it is easy to make chemical modification on nanomaterials and more biomolecules will be immobilized to improve the sensitivity of the biosensor owing to their large surface area. The main work of this dissertation is to fabricate an electrochemical biosensor with ultra-high sensitivity, high selectivity and good stability through the immobilization of biomolecules on the surface and the specific recognition between these biomolecules, in which biosensoring technology and nanotechnology are well combined. The resulting electrochemical biosensor was successfully applied for the detection of a2,6-sialylated glycans in the serum.In this work, GO-PB-PTC-NH2 nanocomposite was synthesized as the functionalized material for the construction of the electrochemical biosensor. The target analytes were detected through the specific recognition of the lectin sambucus nigra agglutinins (SNAs). The structural characterization of GO-PB-PTC-NH2 nanocomposite was investigated by UV-vis spectroscopy and fourier transform infrared (FT-IR) spectroscopy. Scan electron microscopy (SEM) and transmission electron microscopy (TEM) were used for the morphology characterization of the as-made nanocomposite. The performance of the modified electrode and its response mechanism were characterized using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) techniques. Differential pulse voltammetry (DPV) was used for the detection of a2,6-sialylated glycans. The proposed electrochemical biosensor provides a new method for life science and other related fields. The detail contents are as follows:Ultrasensitive electrochemical biosensor based on graphite oxide, Prussian blue, and PTC-NH2 for the detection of α2,6-sialylated glycans in human seruma2,6-Sialylated glycans are crucial molecular targets for cancer diagnosis and clinical research. In this work, a novel ultrasensitive electrochemical biosensor was fabricated based on a graphite oxide (GO), Prussian blue (PB), and PTC-NH2 (an ammonolysis product of 3,4,9,10-perylenetetracarboxylic dianhy-dride) nanocomposite for the selective detection of a2,6-sialylated glycans. To increase the sensitivity of the electrochemical biosensor, gold nanoparticles (GNPs) were immobilized on a GO-PB-PTC-NH2 modified glassy carbon electrode (GCE). Sambucus nigra agglutinins (SNAs), which specifically bind with α2,6-sialylated glycans, were covalently immobilized on GNPs for the sensitive detection of a2,6-sialylated glycans in serum. This proposed method can be applied to human serum, and it worked well over a broad linear range (0.1 pg·mL-1～ 500 ng·mL-1) with detection limits of 0.03 pg·mL-1. Moreover, recovery of the spiked samples ranged from 100.2% to 105.0%, suggesting that this excellent electro-chemical biosensor can be used for the practical detection of α2,6-sialylated glycans.