Biological studies with tin oxide materials

Abstract Studying how the morphology or electrophysiology of biological cells changes with a new drug has been crucial for screening the efficacy and side effects of the new drug. While conventional instruments are limited to studying only a few cells in parallel, this chapter introduces the possibility of integrating indium tin oxide (ITO) microelectrodes with microfluidic systems to form a transparent microlab. The microlab contains microfluidic channels to guide biological cells to stay right above ITO microelectrodes, so that both morphology and electrophysiology of the cells can be studied simultaneously. Fabricating the microelectrodes into an array further enables rapid drug screening. This chapter first introduces the potential biological applications and advantages for ITO electrodes. By comparing the electrochemical impedance of microelectrodes made of ITO and inert metals, whether the impedance of ITO electrodes is small enough for electrophysiological studies is discussed. Afterwards, the process for fabricating multilayer, microfluidic channels above an ITO microelectrode array is proposed and realized. The fabricated “transparent” microlab contains micro-channels to guide cells to flow into microwells above ITO microelectrodes. After verifying the structure and fluid flow in the microlab, the feasibility of using the microlab for trapping biological cells and recording electrophysiological signals is verified with red blood cells, neurons, and a dissected heart of the zebrafish. The results demonstrate that the ITO microelectrode is able to record the heartbeat signals reliably, as well as to trap cells whose diameter is greater than 10 μm.