Dip pen nanolithography functionalized electrical gaps for multiplexed DNA detection

Nanoparticle-based, silver-enhanced DNA electrical detection shows great promise for point-of-care diagnostics. In this paper, we demonstrate that the dip pen nanolithography (DPN) method can be used to precisely functionalize multiple electrical gaps for multiplexed DNA detection. With the use of the DPN technique, capture ssDNAs are written inside 5 mu m x 10 mu m electrical gaps on substrates. The DPN functionalized electrical gaps can specifically hybridize to target ssDNAs in solution. Successful hybridization of the capture-target DNA complex is detected by the use of gold nanoparticles carrying ssDNA, which also hybridize to the target ssDNA, followed by silver enhancement. The drop of resistance across the gaps due to the formation of metal nanoparticle-DNA complexes is measured over time and compared against characteristics of control gaps, which are either left unfunctionalized or functionalized with noncomplementary capture ssDNA. This technique has potential for high-density multiplexed DNA assay chips. Multiplex detection of two different target ssDNAs in solution using DPN functionalized electrical gaps on the same chip is demonstrated. The lowest detection limit is 10 mu M.