First multiplexed electrochemical wax-on-plastic chip: PNA/GO interface integration for DNA detection

This study presents the fabrication of the first multiplexed wax-on-plastic electrochemical chip with low-temperature sintering of the conductive layers. A total of 169 sensing electrodes (1.2 mm diameter each) were printed on a wax-patterned plastic substrate using silver inkjet printing. Fidelity of the device was confirmed using optical and electrical techniques. The sensing electrodes were modified using graphene oxide (GO) ink and peptide nucleic acid (PNA) probes through simple drop-casting. The PNA/GO interface on the multiplexed chip was used to detect DNA using differential pulse voltammetry, which records the electrons transfer from the diffusion of a soluble redox probe. The PNA/GO interface was then tested against a target concentration, target size, and mismatched target. The response of the DNA-PNA duplex on the surface was additionally compared with the prehybridized duplex, and the lower affinity of the duplexes for the GO surface was confirmed by removing Mg2+. The interface was responsive to such variables at attomolar concentrations. The low volume of the target (300 nL) at that concentration level demonstrated the chip sensitivity with only 18 target molecules on the surface.