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Abstract
There is a substantial requirement for the development of biosensors capable of selective detection, that are also low cost, easy to use and have the possibility of being integrated into portable devices. Silicon is a good candidate due to the possibility of fabricating field-effect devices, stable chemical bond with organic monolayer and the ability to convert biological information directly into electrical signals due to generating of electrical charge by photo-irradiation. Based on silicon characteristics, the research herein will demonstrate a light addressable electrochemical measurement for fabrication of DNA bio-sensing interface towards DNA hybridization detection and developing a DNA electrode array. As the fouling biomolecules might limit the application of biosensor in complex samples two efficient antifouling molecules, bovine serum albumin (BSA) and hexa-ethylene oxide (HEO), were employed to minimize this fouling behavior. Then the proposed method is utilized to make a DNA electrode array via microcontact printing technique. The DNA biosensing interface shows that although BSA provides a decent antifouling property by blocking the potential non-specific binding sites for DNA adsorption to discriminate different target DNAs, it is not a good nominate as its stability suppress over time whilst HEO shows an excellent stability and selectivity for DNA detection. Effect of different complementary DNA concentration on the DNA biosensor using HEO as the antifouling agent was also investigated. The response was proportional to the logarithm value of target DNA concentration over the range from 1.0 x 10-6 M to 1.0 x 10-11 M with a linear correlation coefficient of 0.9764. The parallel measurements of three different DNA biosensors by using complementary target DNA in three different days exhibits a low relative standard deviation of 4.56% and demonstrates a plausible reproducibility. The DNA biosensor has shown great selectivity toward DNA complementary target when tested in a complex sample consist of one complementary and three different non-complementary targets DNA. Micro-contact printing of three different DNA probes onto HEO modified Si(100) surface and light activated amperometric detection has shown excellent reproducibility and selectivity toward DNA target discrimination in complex sample.