Three-dimensional (3-D) microfluidic-channel-based DNA biosensor for ultra-sensitive electrochemical detection

A three-dimensional (3-D) microfluidic-channel-based electrochemical DNA biosensor was constructed using anodic aluminum oxide (AAO) filtration membranes as the designing templates by taking advantage of their well-defined cylindrical fluidic channels. By electroless gold plating and through thio chemistry, single stranded DNA sequences with 19 base pairs specified to Bacteroides thetaiotaomicron were immobilized into the AAO fluidic channels to form a probe DNA electrode for electrochemical sensing. Cyclic voltammetry (CV) was used to measure the electrochemical response of the sensor using two different redox indicators, [Fe(CN)6]4− and/or [Ru(NH3)6]3− before and after hybridization with the complementary target DNA sequences. The microfluidic-channel-based DNA biosensor showed detection sensitivity amplified to 10−19 M, which is one order of magnitude higher than attomolar (10−18 M) range. Such enhanced detection sensitivity is attributed to the well-defined fluidic channel structure that gives high surface area for probe DNA immobilization and enables target DNA solutions to pass through its fluidic channels for rapid and efficient hybridization.