Tudies Of Electrochemical Human IgE Aptamer Biosensor

With the molecular biology and gene engineering quickly developing and an in-depth reaearching,it is graetly driving nucleic acid research.The aptamer a man-made nucleic acid has a strictly distinguishing and afinity abilities,which has a revolutionary change in antibody-antigene reactions and also affects the antibody's deficiencys. It developed a new way for the traditional immune sensor development.Electrochemical impedance aptamer array sensor is a new idea and attemptment.Compares with traditional technology,the electrochemical aptamer sensor has the advantages of rapidity,sensitivity,easy-using and has the molecular recognition function.In the experiment, we chosed the human IgE and its the DNA nucleic acid human IgE aptamer as a model system.The atamer was immobilized on the golden array electrode surface through electric addressing methods or not.,then we measuring the impedance values before and after interaction with human IgE and research the impedance values change in different conditions.The presented rapid and oriented aptamer immobilized method will benefit for the fabrication of aptamer array electrodes.1. Label-Free Electrochemical Aptamer-Based Array sensorThe electrode pattern was formed on a crystal wafer substrate (36mm×26mm). A 200 nm thick photolithographic gold film was prepared by vapor deposition, with an underlayer of chromium (50 ?) on the substrate. The dimension of each gold working electrode was 2mm×2mm. Prior to the modification, the chip was immersed in a piranha solution (H2SO4/H2O2: 3/1) for 30 minutes and then rinsed thoroughly using water and ethanol.A home-constructed poly(dimethylsiloxane) (PDMS; Dow Corning Inc.) frame containing 24-microwells was then aligned onto the electrodes such that each well could exactly match the working electrodes. Prior to the immobilization, a 10μM solution of the aptamer or the scrambled sequences was mixed with 100μM cysteamine ( Tris-HCl buffer, pH 7.4; 1 mM EDTA, 0.2 M NaCl, and 100 mM DTT.). To modify the electrodes, the resulting solution was transferred into the relative microwells of the PDMS frame and subsequently incubated with the gold electrodes overnight. After the immobilization, the PDMS frame was removed, and the aptamer-modified chip was rinsed by phosphate-buffered saline (PBS; 137 mM NaCl, 3 mM KCl, 10 mM phosphate, pH 7.4), followed by rinsing with deionized water. The rinsed chips were then dried under a stream of nitrogen.At last, the ctrochemical impedance spectroscopy measurements were performed.Through the condition optimization experiments,at the condition of the cysteamine molecule concentration 0.1mmol/L,the immobilization time 90 minutes, the human IgE incubation tme 90 minutes, the experiment can achieved the best results.