Eric Stava

Guided neuronal growth on arrays of biofunctionalized GaAs/InGaAs semiconductor microtubes

We demonstrate embedded growth of cortical mouse neurons in dense arrays of semiconductor microtubes. The microtubes, fabricated from a strained GaAs/InGaAs heterostructure, guide axon growth through them and potentially enable electrical and optical probing of propagating action potentials. The coaxial nature of the microtubes—similar to myelin—is expected to enhance the signal transduction along the axon. We present a technique of suppressing arsenic toxicity and prove the success of this technique by overgrowing neuronal mouse cells.

Single-Ion Channel Recordings on Quartz Substrates

We show that a single-crystal quartz substrate provides a working platform for ion channel research. Single-crystal quartz is piezoelectric, so it can be nanomechanically actuated to perform precise membrane deformations. This, along with its superior noise properties, makes single-crystal quartz ideal for analyzing mechanosensitive ion channels.

On-Chip Stochastic Resonance of Ion Channel Systems With Variable Internal Noise

We induced stochastic resonance in planar lipid bilayer systems with alamethicin ion channels, and varied alamethicin concentration, membrane area, and applied voltage. We found that membrane-induced microphonic noise significantly affects the signature of stochastic resonance, and that this noise can be used to optimize ion channel-based biosensors.

Flow characterization and patch clamp dose responses using jet microfluidics in a tubeless microfluidic device

BACKGROUND Surface tension passive pumping is a way to actuate flow without the need for pumps, tubing or valves by using the pressure inside small drop to move liquid via a microfluidic channel. These types of tubeless devices have typically been used in cell biology. Herein we present the use of tubeless devices as a fluid exchange platform for patch clamp electrophysiology. NEW METHOD Inertia from high-speed droplets and jets is used to create flow and perform on-the-fly mixing of solutions. These are then flowed over GABA transfected HEK cells under patch in order to perform a dose response analysis. RESULTS TIRF imaging and electrical recordings are used to study the fluid exchange properties of the microfluidic device, resulting in 0-90% fluid exchange times of hundreds of milliseconds. COMSOL is used to model flow and fluid exchange within the device. Patch-clamping experiments show the ability to use high-speed passive pumping and its derivatives for studying peak dose responses, but not for studying ion channel kinetics. COMPARISON WITH EXISTING METHOD(S) Our system results in fluid exchange times slower than when using a standard 12-barrel application system and is not as stable as traditional methods, but it offers a new platform with added functionality. CONCLUSIONS Surface tension passive pumping and tubeless devices can be used in a limited fashion for electrophysiology. Users may obtain peak dose responses but the system, in its current form, is not capable of fluid exchange fast enough to study the kinetics of most ion channels.

Ultra-stable glass microcraters for on-chip patch clamping

We report on a single-step fabrication procedure of borosilicate glass micropores surrounded by a smooth microcrater. By inserting a thin air-gap between a borosilicate glass substrate and a reflective layer, we achieve dual-sided laser ablation of the device. The resultant crater provides a smoother, curved surface onto which cells settle during planar patch clamping. Gigaohm seals, which are more easily achievable on these devices as compared to conventional micropores, are achieved by patch clamping human embryonic kidney (HEK 293) cells. Further, the microcraters show enhanced mechanical stability of the planar patch clamped cells during perfusion. We integrate polydimethylsiloxane microfluidic devices with the microcraters and use passive pumping to perfuse the cells. We find that passive pumping increases the pressure within the device by 1.85 Pa. However, due to the enhanced stability of the microcrater, fluidic shearing reduces the seal resistance by only 6.8 MΩ on average, which is less than one percent of the gigaohm seal resistance.