Executive Summary : | In this work, it was proposed to design and develop a smart electrode system for DNA biosensor which is an important class of point-of-care diagnostic device and can convert recognition event signal into an interpretable analytical signal. By definition, electrochemical DNA-based biosensor is a device that integrates DNA as a biological recognition element and an electrode as a physicochemical transducer. It is more adavantageous than other types of sensors due to its specificity of response, and selectivity to the analyte. Moreover, electrochemical DNA sensor gives an electronic signal directly and does not involve any complicated chemical procedures. The disadvantages of using such sensors include high background signals, and more importantly it does not consider the chirality of the molecule in its primary and secondary (helix) structure. In the light of the above mentioned fact, investigators propose the novel idea of using spin polarized current instead of charge current for the detection and recognition of DNA. When spin-polarized electrons interact with alpha/beta helix of DNA, it produces different degrees of interactions depending on the chirality of DNA molecules. In a recent discovery at Weizmann Institute of Science, it has been observed that electrons transmitted through DNA yield spin polarized electrons (64%) at room temperature. Quantitative estimation of this spin polarized current signifies the intrinsic nature of the DNA and its interactions. This (spin) is more fundamental which would enable for efficient bio-detection and recognition of DNA based electrochemical sensor. Process: 1. Nano fabrication of electrodes: Using the state of the art technique including electrochemical and photo lithographic techniques, the working electrodes would be designed on Si substrates. The electrode will consists of a multilayer of half metallic alloy for 100 % spin injection in to the molecule. The electrode thus prepared will be functionalized with the DNA molecule or the target molecule. 2. Electrochemical measurements: We will place the functionalized electrode inside a specially designed electrochemical cell and inject a particular spin by applying magnetic field on the surface of the electrode. Due to the CISS effect, only a particular spin will be preferential and the other one will be suppressed and a difference of spin current in these two will estimate the spin polarization yield that will determine the type of interaction, hybridization or the sequence of DNA. Other electrochemical techniques including impedance spectroscopy, chronoamperommetry etc. will be conducted to supplement the results. Electrochemical DNA biosensors based on smart electrode system would pave the way for fast, accurate, simple, and low cost device and would play a key role in the fields of molecular and medical diagnosis, environmental monitoring, food analysis, pharmacogenomics, and drug discovery. |