Electrophoretic time-of-flight measurements of single DNA molecules with two stacked nanopores.

Electrophoretic transport through a solid-state nanodevice comprised of two stacked nanopore sensors is used to determine the free-solution mobility of DNA molecules based on their "time-of-flight" between the two pores. Mobility measurements are possible at very low (100 pM) DNA concentration and for low as well as high salt concentrations (here 30 mM and 1 M KCl). The mechanism of DNA transport through the device is elucidated by statistical analysis, showing the free-draining nature of the translocating DNA polymers and a barrier-dominated escape through the second pore.

A pore-cavity-pore device to trap and investigate single nanoparticles and DNA molecules in a femtoliter compartment: confined diffusion and narrow escape.

Spatial confinement from the nano- to the microscale is ubiquitous in nature. Striving to understand the behavior of nanoscale objects in confined domains we present a nanofluidic silicon device which consists of two stacked nanopores forming the in/outlets to a pyramidal cavity of micrometer dimensions (10 fL volume). Being electrically addressable, charged objects can be actively loaded into, trapped inside, and unloaded from the "pore-cavity-pore" (PCP) device.

Multiplexed parallel single transport recordings on nanopore arrays.

We introduce a nanofabricated silicon chip for massively multiplexed analysis of membrane channels and transporters in suspended lipid membranes that does not require any surface modification or organic solvent. Transport processes through single membrane complexes are monitored by fluorescence. The chip consists of an array of well-defined nanopores, addressing an individual pyramidal back-reflecting 30-fL compartment.

Fabrication of metallized nanopores in silicon nitride membranes for single-molecule sensing.

The fabrication and characterization of a metallized nanopore structure for the sensing of single molecules is described. Pores of varying diameters (>10 nm) are patterned into free-standing silicon nitride membranes by electron-beam lithography and reactive ion etching. Structural characterization by transmission electron microscopy (TEM) and tomography reveals a conical pore shape with a 40 degrees aperture.

Electrically facilitated translocations of proteins through silicon nitride nanopores: conjoint and competitive action of diffusion, electrophoresis, and electroosmosis.

Solid-state nanopores bear great potential to be used to probe single proteins; however, the passage of proteins through nanopores was found to be complex, and unexpected translocation behavior with respect to the passage direction, rate, and duration was observed. Here we study the translocation of a model protein (avidin) through silicon nitride nanopores focusing on the electrokinetic effects that facilitate protein transport across the pore. The nanopore zeta potential zeta(pore) and the protein zeta potential zeta(protein) are measured independently as a function of solution pH.

Data analysis of translocation events in nanopore experiments.

Nanopores have become important tools for single molecule experiments, where information about the properties of DNA/RNA or proteins is inferred from current pulses elicited by individual molecules as they traverse a single pore. However, because of necessary electronic filters employed in the measurement technique, the extraction of meaningful information from short pulses is limited. This restricts the use of nanopores for the investigation of small molecules which cross the pore rapidly.

Organophosphonate-based PNA-functionalization of silicon nanowires for label-free DNA detection.

We investigated hydroxyalkylphosphonate monolayers as a novel platform for the biofunctionalization of silicon-based field effect sensor devices. This included a detailed study of the thin film properties of organophosphonate films on Si substrates using several surface analysis techniques, including AFM, ellipsometry, contact angle, X-ray photoelectron spectroscopy (XPS), X-ray reflectivity, and current-voltage characteristics in electrolyte solution. Our results indicate the formation of a dense monolayer on the native silicon oxide that has excellent passivation properties.

PNA-PEG modified silicon platforms as functional bio-interfaces for applications in DNA microarrays and biosensors.

The synthesis and characterization of two types of silicon-based biofunctional interfaces are reported; each interface bonds a dense layer of poly(ethylene glycol) (PEG(n)) and peptide nucleic acid (PNA) probes. Phosphonate self-assembled monolayers were derivatized with PNA using a maleimido-terminated PEG(45). Similarly, siloxane monolayers were functionalized with PNA using a maleimido-terminated PEG(45) spacer and were subsequently modified with a shorter methoxy-terminated PEG(12) ("back-filling").