Magnetic Assembly of Vertical Nanogaps for Highly Sensitive Electrical Biosensors.

Nanogap biosensors have emerged as potential tools for the detection and analysis of minuscule quantities of biomolecules, offering unparalleled sensitivity, a low limit of detection (LOD), and enhanced output signals. However, their potential is often limited by the intricate and labor-intensive processes required to precisely engineer the the tiny gap between electrodes. In this work, we present an innovative fabrication method to obtain vertical nanogap platforms for electrical biosensing. Leveraging magnetic attraction, we facilely construct 40 nm gaps by assembling antibody-tagged nanowires onto a nanodisk positioned between a pair of microelectrodes. An electrically conductive bridge is established when gold nanoparticles, conjugated with targeted antigen, are captured within the gaps. This results in a substantial amplification in the output current across the electrodes. Our platforms demonstrate an LOD of 18 pM with a linear dynamic detection range up to 150 pM. This approach offers a versatile biosensing platform with potential integration into a myriad of applications, from lab-on-chip systems to biomedicine and point-of-care diagnostics.