Integrated In-Plane Nanofluidic Devices for Resistive-Pulse Sensing.

Single-entity (or digital) measurements enhance sensitivity (10- to 100-fold improvement) and uncover heterogeneity within a population (one event in 100 to 10,000). Many biological systems are significantly influenced by rare or infrequent events, and determining what species is present, in what quantity, and role of that species is critically important to unraveling many questions. To develop these measurement systems, resistive-pulse sensing is used as a label-free, single-particle detection technique and can be combined with a range of functional elements, e.g., mixers, reactors, filters, separators, and pores. Virtually, any two-dimensional layout of the micro- and nanofluidic conduits can be envisioned, designed, and fabricated in the plane of the device. Multiple nanopores in series lead to higher-precision measurements of particle size, shape, and charge, and reactions coupled directly with the particle-size measurements improve temporal response. Moreover, other detection techniques, e.g., fluorescence, are highly compatible with the in-plane format. These integrated in-plane nanofluidic devices expand the toolbox of what is possible with single-entity measurements.

Characterization of Extracellular Vesicles by Resistive-Pulse Sensing on In-Plane Multipore Nanofluidic Devices.

Extracellular vesicles (EVs) are cell-derived, naturally produced, membrane-bound nanoscale particles that are linked to cell-cell communication and the propagation of diseases. Here, we report the design and testing of in-plane nanofluidic devices for resistive-pulse measurements of EVs derived from bovine milk and human breast cancer cells. The devices were fabricated in plane with three nanopores in series to determine the particle volume and diameter, two pore-to-pore regions to measure the electrophoretic mobility and zeta potential, and an in-line filter to prevent cellular debris and aggregates from entering the nanopore region. Devices were tested with and without the channels coated with a short-chain PEG silane to minimize electroosmotic flow and permit an accurate measurement of the electrophoretic mobility and zeta potential of the EVs. To enhance throughput of EVs, vacuum was applied to the waste reservoir to increase particle frequencies up to 1000 min-1. The nanopores had cross-sections 200 nm wide and 200 nm deep and easily resolved EV diameters from 60 to 160 nm. EVs from bovine milk and human breast cancer cells had similar particle size distributions, but their zeta potentials differed by 2-fold, -8 ± 1 and -4 ± 1 mV, respectively.