Nanoengineered PANI-Au Interfaces for Bimodal Biosensing

Robust biosensors for on-line/in-line detection would enable new approaches for point-of-care medical diagnostics, as well as continuous monitoring and control of process parameters in pharmaceutical manufacturing, environmental monitoring and bioterrorism security. A bimodal approach, utilizing simultaneous transduction and/or sensing mechanisms, can enhance a sensor’s figures of merit and its reliability in critical applications. In this work a specific bimodal approach based on the coupling of electrochemical (EC) methods with surface enhanced Raman spectroscopy (SERS) is described. When used together, EC-SERS can provide information about electrochemical activity and molecule-specific vibrational signatures.

To realize these capabilities, we have developed a two-step electrochemical method to fabricate new composite electrode materials consisting of polyaniline (PANI) and nanostructured gold. These PANI-Au electrodes show electrochemical activity in biologically relevant pH ranges and SERS enhancement factors of up to five orders of magnitude. Additionally, under optimized deposition conditions the spot-to-spot deviation and electrode-to-electrode deviation have been minimized to 8% and 12%, respectively. Finally, these PANI-Au interfaces are applied towards bimodal monitoring of DNA hybridization and melting. Using this approach, the binding and stability of multiple complementary DNA sequences can be probed simultaneously.