Microfluidic chip to produce temperature jumps for electrophysiology

We developed a microfluidic chip that provides rapid temperature changes and accurate temperature control of the perfusing solution to facilitate patch-clamp studies. The device consists of a fluid channel connected to an accessible reservoir for cell culture and patch-clamp measurements. A thin-film platinum heater was placed in the flow channel to generate rapid temperature change, and the temperature was monitored using a thin-film resistor. We constructed the thermal chip using SU-8 on a glass wafer to minimize the heat loss. The chip is capable of increasing the solution temperature from bath temperature (20 degrees C) to 80 degrees C at an optimum heating rate of 0.5 degrees C/ms. To demonstrate the ability of the thermal chip, we have conducted on-chip patch-clamp recordings of temperature-sensitive ion channels (TRPV1) transfected HEK293 cells. The heat-stimulated currents were observed using whole-cell and cell-attached patch configurations. The results demonstrated that the chip can provide rapid temperature jumps at the resolution of single-ion channels.