(131e) A Low-Cost Nucleic Acid Biosensor for Point-of-Care Application

                                         A Low-Cost Nucleic Acid Biosensor for Point-of-Care Application

Satyajyoti Senapati, Zdenek Slouka, Sunny Shah, and Hsueh-Chia Chang

Department of Chemical and Biomolecular Engineering

University of Notre Dame, Indiana 46556

Abstract

The development of low-cost and portable detection platform for genetic identification has attracted great attention to a wide variety of application such as infectious disease control, epidemic control, clinical diagnosis etc. Nucleic acid amplification-based detection systems (real time PCR) specifically designed for portability are far from reality due to their complex protocol, difficulty of use and high costs limiting their widespread use among first responders and public health officials. Alternatively, a simple label-free and PCR-free turn-key sensing platform based upon direct nucleic acid (DNA/RNA) detection would have the potential to identify the specific virus and strain as well as detect infection in patients more quickly and specifically than immunoassays. In our prior studies, we discovered a nanoporous ion-selective sensing platform that can achieve these objectives. Here, we report a low-cost, portable, selective and PCR free biosensing platform for the detection of DNA/RNA molecule using ion selective environments. The detection is based on a charge inversion phenomenon that occurs when negatively charged DNA/RNA molecules hybridize with specific probes attached to ion exchange nanoporous materials bearing a positive fixed charge. When a DC field is applied across a nanoporous material, a small molecular charge polarized layer develops on the depletion side after concentration polarization. The presence of molecules in this polarized layer can hence sensitively change the limiting and overlimiting currents of the ion-selective material. Furthermore, oppositely charged small molecule targets can produce a bipolar membrane, like a P-N semiconductor junction, that can produce a large water-splitting signal when a high field develops at the carrier-depleted junction with a reverse bias. This new molecular sensing technology also accelerates the assay time because the high field in the polarized layer can attract large nucleic acids by dielectrophoresis and the depletion region can concentrate the charged molecules near the sensor surface in a flowing stream. Instead of the classical electrochemical sensing technique, we utilize a much more sensitive conductance and impedance signature based on sensitivity of ion current across the nanoporous membrane or particle to surface charge density change effected by hybridized molecules. The sensitivity involves a nonlinear correction to the conductance and is hence much more sensitive than EIS or other linear electrochemical sensing techniques.