Molecular transport of proteins through nanoporous membranes fabricated by interferometric lithography.

Millimeter sized arrays of uniformly-distributed nanopores (180-220 nm) were created in thin (200 nm) silicon nitride membranes using interferometric lithography. Molecular transport properties of the fabricated devices were investigated experimentally and compared with those of state-of-the-art polycarbonate track etched membranes. Two similarly-sized proteins, bovine serum albumin (BSA) and bovine hemoglobin (BHb), were used as permeates in the transport experiments.

Mesoscale simulations of biomolecular transport through nanofilters with tapered and cylindrical geometries.

Molecular transport properties in short cylindrical and pyramidal nanopores are investigated by mesoscale dissipative particle dynamics simulations. We examine the effect of pore geometry, size, flow direction, particle diameter and electrostatic forces on membrane flux, selectivity and fouling. Biomolecules of various sizes are represented by spherical particles as they move through nanopores.

The role of pore geometry in single nanoparticle detection.

We observe single nanoparticle translocation events via resistive pulse sensing using silicon nitride pores described by a range of lengths and diameters. Pores are prepared by focused ion beam milling in 50 nm-, 100 nm-, and 500 nm-thick silicon nitride membranes with diameters fabricated to accommodate spherical silica nanoparticles with sizes chosen to mimic that of virus particles. In this manner, we are able to characterize the role of pore geometry in three key components of the detection scheme, namely, event magnitude, event duration, and event frequency.

Polystyrene particles reveal pore substructure as they translocate.

In this article, we report resistive-pulse sensing experiments with cylindrical track-etched PET pores, which reveal that the diameters of these pores fluctuate along their length. The resistive pulses generated by polymer spheres passing through these pores have a repeatable pattern of large variations corresponding to these diameter changes. We show that this pattern of variations enables the unambiguous resolution of multiple particles simultaneously in the pore, that it can detect transient sticking of particles within the pore, and that it can confirm whether any individual particle completely translocates the pore.

Rapid-viability PCR method for detection of live, virulent Bacillus anthracis in environmental samples.

In the event of a biothreat agent release, hundreds of samples would need to be rapidly processed to characterize the extent of contamination and determine the efficacy of remediation activities. Current biological agent identification and viability determination methods are both labor- and time-intensive such that turnaround time for confirmed results is typically several days. In order to alleviate this issue, automated, high-throughput sample processing methods were developed in which real-time PCR analysis is conducted on samples before and after incubation.