Bioinspired Protein Channel-Based Scanning Ion Conductance Microscopy (Bio-SICM) for Simultaneous Conductance and Specific Molecular Imaging

The utility of stochastic single-molecule detection using protein nanopores has found widespread application in bioanalytical sensing as a result of the inherent signal amplification of the resistive pulse method. Integration of protein nanopores with high-resolution scanning ion conductance microscopy (SICM) extends the utility of SICM by enabling selective chemical imaging of specific target molecules, while simultaneously providing topographical information about the net ion flux through a pore under a concentration gradient. In this study, we describe the development of a bioinspired scanning ion conductance microscopy (bio-SICM) approach that couples the imaging ability of SICM with the sensitivity and chemical selectivity of protein channels to perform simultaneous pore imaging and specific molecule mapping. To establish the framework of the bio-SICM platform, we utilize the well-studied protein channel alpha-hemolysin (alpha HL) to map the presence of beta-cyclodextrin (beta CD) at a substrate pore opening. We demonstrate concurrent pore and specific molecule imaging by raster scanning an alpha HL-based probe over a glass membrane containing a single 25-mu m-diameter glass pore while recording the lateral positions of the probe and channel activity via ionic current. We use the average channel current to create a conductance image and the raw current-time traces to determine spatial localization of beta CD. With further optimization, we believe that the bio-SICM platform will provide a powerful analytical methodology that is generalizable, and thus offers significant utility in a myriad of bioanalytical applications.