A Multi-Plex Biochip Platform for Integrated Ionic Current and Plasmonic Molecular Sensors

A new low-cost and portable biomolecule nanosensor platform, with single-molecule sensitivity and single-mutation nucleic acid selectivity, is designed by integrating a nanoporous membrane/gel-based 3-D microfluidic biochip platform with two nanosensor technologies: nanopore ion current sensors and plasmonic hotspot enhanced fluorescence at nanoparticle assemblies. The open-flow design with embedded electro-osmotic pump allows high throughput, shear-enhanced selectivity and rapid flow-electrophoresis separation. The membrane components, integrated by a 3-D polycarbonate biochip architecture, are designed for automated analyte concentration, pH/ionic strength control and large-dynamic range (fM to mM) probe-based sensing of nucleic acids (including short microRNA) from the non-equilibrium ion flux across the ion-selective membranes. The on-chip ionic circuits of this new membrane-based platform are interfaced with the micro-circuits of a portable electronic instrument. The nonlinear ionic components permit many simplifying designs, such as reading/activation of multiple on-chip sensors/actuators with a single binary sequence input.  For single molecule enumeration and for small protein targets, we integrate conic nanopores, fabricated by low-cost ion-track etching or laser-assisted drawing, and optical fiber bundles with etched conic tips into the biochip.  By assembling Au nanoparticles at the nanopore and at the nanocone array, we are able to produce tunable plasmonic hotspots that can enhance the sensitivity of the FRET fluorescent reporter by orders of magnitude, allowing optical imaging with an integrated miniature camera. Continuous enumeration is achieved with single-molecule ion current translocation signals and dielectrophoretic trapping is often introduced to accelerate the assay time. The first-generation devices of the ion current platform are being commercialized by Notre Dame-affiliated startups and the combined ion current/plasmonic platform is being developed for several multi-target portable diagnostic applications, including monitoring of mosquito-carried diseases. 

Annual Review of Analytical Chemistry, 2014,DOI: 10.1146/annurev-anchem-071213-020155); Biosensors and Bioelectronics, 2014,doi.org/10.1016/j.bios.2014.04.008 ; Langmuir, 2013, 29:8275;  LabChip, 2014, 14:979; Biomicrofluidics, 2013, 7:061102; 2014, 8:021101; J. Chem Phys, 2013, 138:044706; Optics Express 2013, 21:6609;  Phys Rev Lett, 2012,  109:224301; ACSNano, 2009, 3:1823.