Alternative Label-free Immunosensor For Amperometric Immunoassay Toward Alpha-fetoprotein Based On The IrO_x Nanofiber

Even though the social is highly developed, cancer is still an unsolved problem. Scientific studies show that the cure rate of early cancer is as high as 83%, so the key is to find tumor timely and diagnose. In general, checking out the tumor makers in blood is the most effective way. In this paper, we focused on the detection of AFP(alpha-fetoprotein) which is the tumor maker for hepatic carcinoma. The AFP mainly comes from the embryonic liver cells. Usually, the content of AFP in the adult blood is less than 25ng/m L. The methods to detect AFP include fluorescence analysis, enzyme-linked immunoassay, chemiluminescence analysis, electrochemical analysis etc. However, the automation equipment for RIA technology is very expensive, and can endanger the health of human. In spite of the high sensitivity and wide range of applications of ELISA, its structure is relatively complex. Therefore, we focus on the research of the lable-free electrochemical sensor with a simple structure, short response time, low cost, high sensitivity and so on.In order to obtain an AFP sensor with excellent performance, first we choose the detection mean of the lable-free electrochemical. Secondly we use the IrO_x nanofibers prepared by electrospinning as the electrode material. The selection of electrode materials is very important for the performance of the sensor. Therefore, the electrode materials should have improved conductivity in order to assist the electron transfer, and also can provide a large surface area to immobilize more antibodies, as well as good biocompatibility and stability. Recently, iridium oxide(IrO_x) which has metal-like conductivity and a resistance of ~50 mΩ cm in bulk,has attracted much attentions due to its excellent performance in electrochemical sensor. Moreover, it’s especially superior chemical and thermal stability also make it much easier to control the structure of IrO_x. However, to the best of our knowledge, there have been no reports on the use of any IrO_x applied on label-free electrochemical immunosensor for AFP detection.In this paper, a sensitive label-free electrochemical immunosensor for amperometric immunoassay of AFP was designed based on the electrospun IrO_x nanofibers. Especially, the specific wire-in-tube nanostructure of IrO_x nanofibers was first fabricated through simply one-spinneret electrospinning process. Such IrO_x nanofibers can provide large effective surface area and act as a rapid electron transfer channel, which make the proposed IrO_x nanofibers immunosensor show good performance for AFP detection, such as high sensitivity and selectivity, wide detection range(0.05ng/m L-150ng/m L), low detection limit(20pg/m L), the promoted stability, and moreover, good accuracy to detect AFP in real serum. The comparison of the IrO_x nanofibers modified immunosensor in this work with other noble metal modified AFP immunosensors. It can be seen that the linear range of IrO_x nanofibers modified immunosensor is satisfactory with a larger slope, indicating that the as proposed immunosensor is more sensitive to AFP. Then we prepared the hetero structure of IrO_x and Cu O through the hydrothermal method and preliminary study its application in detecting AFP. From the results of this two AFP sensors, it show that the performance based on the IrO_x-Cu O is poor compared with singe IrO_x nanomaterials which is mainly due to the lager resistance of the Cu O.