J. Tanner Nevill

Integrated microfluidic cell culture and lysis on a chip

We present an integrated microfluidic cell culture and lysis platform for automated cell analysis that improves on systems which require multiple reagents and manual procedures. Through the combination of previous technologies developed in our lab (namely, on-chip cell culture and electrochemical cell lysis) we have designed, fabricated, and characterized an integrated microfluidic platform capable of culturing HeLa, MCF-7, Jurkat, and CHO-K1 cells for up to five days and subsequently lysing the cells without the need to add lysing reagents. On-demand lysis was accomplished by local hydroxide ion generation within microfluidic chambers, releasing both proteinacious (GFP) and genetic (Hoescht-stained DNA) material. Sample proteins exposed to the electrochemical lysis conditions were immunodetectable (p53) and their enzymatic activity (HRP) was investigated.

Continuous differential impedance spectroscopy of single cells

A device for continuous differential impedance analysis of single cells held by a hydrodynamic cell trapping is presented. Measurements are accomplished by recording the current from two closely-situated electrode pairs, one empty (reference) and one containing a cell. We demonstrate time-dependent measurement of single cell impedance produced in response to dynamic chemical perturbations. First, the system is used to assay the response of HeLa cells to the effects of the surfactant Tween, which reduces the impedance of the trapped cells in a concentration dependent way and is interpreted as gradual lysis of the cell membrane. Second, the effects of the bacterial pore-forming toxin, Streptolysin-O are measured: a transient exponential decay in the impedance is recorded as the cell membrane becomes increasingly permeable. The decay time constant is inversely proportional to toxin concentration (482, 150, and 30 s for 0.1, 1, and 10 kU/ml, respectively).

Vacuum soft lithography to direct neuronal polarization

The ability to coat surfaces with pre-determined patterns of biomolecules by soft lithography has found use in areas ranging from fundamental biology to translational medicine, such as tissue engineering and diagnostics. However, existing surface patterning techniques (e.g., microcontact printing and traditional lithography) are unable to pattern several biomolecules in a single step. Here we introduce a simple method to simultaneously pattern multiple biomolecules in complex two-dimensional configurations onto substrates with better than 2 µm resolution. This protocol, termed vacuum soft lithography, utilized below ambient pressures temporarily stored within a removable microfluidic template to expose specific regions of a substrate to multiple biochemical solutions. We demonstrate the utility of this vacuum soft lithography technique by fabricating a multi-component array that directs the adhesion, polarization, and neurite guidance of primary hippocampal neurons.