Hidetaka Uno

Noise Analysis of Si-Based Planar-Type Ion-Channel Biosensors

A micropore with a diameter of 50–100 µm was formed, which penetrated a silicon on insulator (SOI) substrate and a Teflon substrate. The single-ion-channel current of gramicidin A (g-A) was measured for the planar lipid bilayer with reconstructed g-A formed in this micropore. The background noise in the SOI substrate was almost at an equivalent level to that in the Teflon substrate. It can be concluded from the noise analysis that a noise characteristic of the same level as that of the Teflon substrate or the glass substrate can be achieved for the Si substrate by controlling the substrate structure in the vicinity of the micropore with a wide range of pore diameters.

Giant Vesicle Fusion on Microelectrodes Fabricated by Femtosecond Laser Ablation Followed by Synchrotron Radiation Etching

We have developed a new technique for fabricating a hole (well) with a diameter of about 1 µm for a microelectrode on the surface of SiO2 (600 nm)/CoSi2 (10 nm)/Si substrate. This process enabled the fabrication of electrode holes while maintaining the original nanolevel flatness (Ra~0.8 nm) of the SiO2 surface. A lipid bilayer was formed by giant vesicle fusion on these microelectrodes. Fluorescence microscope, in situ atomic force microscope and electrical characteristics measurements showed that a single lipid bilayer of sufficiently high resistance (gigaohm seal) was successfully fabricated.

Microfabrication of PMMA sensor chips for an incubation-type planar patch clamp

A sensor chip for use in an ion channel biosensor based on an incubation-type planar patch clamp was formed using both side hot embossing and focused ion beam (FIB) processing. A biosensor was constructed using the PMMA chip, and the performance of this chip was investigated by measuring the laser-stimulated ion channel current of a channel rhodopsin wide receiver (ChRWR) expressed on HEK293 cells. The observed current profile and membrane potential dependences agreed well with the data measured using a pipette patch clamp. The noise level of the channel current recorded using a 1 kHz low pass filter was 7 pA (rms). The sensor chip fabrication processes are readily modified to permit multi-point measurements; therefore, the excellent performance of the PMMA chip indicates that the chip is suitable for use in high-throughput ion channel biosensor screening applications.