Masahki Matsudaira

Electrochemical Imaging of Dopamine Release from Three-Dimensional-Cultured PC12 Cells Using Large-Scale Integration-Based Amperometric Sensors

In the present study, we used a large-scale integration (LSI)-based amperometric sensor array system, designated Bio-LSI, to image dopamine release from three-dimensional (3D)-cultured PC12 cells (PC12 spheroids). The Bio-LSI device consists of 400 sensor electrodes with a pitch of 250 μm for rapid electrochemical imaging of large areas. PC12 spheroids were stimulated with K(+) to release dopamine. Poststimulation dopamine release from the PC12 spheroids was electrochemically imaged using the Bio-LSI device. Bio-LSI clearly showed the effects of the dopaminergic drugs l-3,4-dihydroxyphenylalanine (L-DOPA) and reserpine on K(+)-stimulated dopamine release from PC12 spheroids. Our results demonstrate that dopamine release from PC12 spheroids can be monitored using the device, suggesting that the Bio-LSI is a promising tool for use in evaluating 3D-cultured dopaminergic cells and the effects of dopaminergic drugs. To the best of our knowledge, this report is the first to describe electrochemical imaging of dopamine release by PC12 spheroids using LSI-based amperometric sensors.

Potentiometric bioimaging with a large-scale integration (LSI)-based electrochemical device for detection of enzyme activity

This paper describes potentiometric bioimaging for enzyme activity using a large-scale integration (LSI)-based electrochemical device with 400 sensors. Potentiometric detection is useful for bioimaging because redox species are not consumed or produced during the detection process; therefore, there is no effect on cell activity and the detectable signal is sustained. In this study, the potentiometer mode of the LSI-based device was applied for the detection of glucose oxidase (GOx) and alkaline phosphatase (ALP) activity. The enzyme activities were quantitatively detected within the concentration ranges of 25-250 μg/mL and 0.10-5.0 ng/mL. In addition, GOx activity in hydrogels and the ALP activity of embryoid bodies (EBs) from embryonic stem (ES) cells were successfully imaged based on detection of the open circuit potentials of individual sensors in real time. To the best of our knowledge, this is the first report of potentiometric imaging using LSI-based electrochemical arrays to detect enzyme activity in ES cells. The LSI-based device is thus demonstrated to be a promising tool for bioimaging of enzyme activity.

Electrochemicolor Imaging Using an LSI-Based Device for Multiplexed Cell Assays

Multiplexed bioimaging systems have triggered the development of effective assays, contributing new biological information. Although electrochemical imaging is beneficial for quantitative analysis in real time, monitoring multiple cell functions is difficult. We have developed a novel electrochemical imaging system, herein, using a large-scale integration (LSI)-based amperometric device for detecting multiple biomolecules simultaneously. This system is designated as an electrochemicolor imaging system in which the current signals from two different types of biomolecules are depicted as a multicolor electrochemical image. The mode-selectable function of the 400-electrode device enables the imaging system and two different potentials can be independently applied to the selected electrodes. The imaging system is successfully applied for detecting multiple cell functions of the embryonic stem (ES) cell and the rat pheochromocytoma (PC12) cell aggregates. To the best of our knowledge, this is the first time that a real-time electrochemical mapping technique for multiple electroactive species, simultaneously, has been reported. The imaging system is a promising bioanalytical method for exploring complex biological phenomena.

Simulation Analysis of Positional Relationship between Embryoid Bodies and Sensors on an LSI-based Amperometric Device for Electrochemical Imaging of Alkaline Phosphatase Activity.

In the present study, we monitored the alkaline phosphatase (ALP) activity of embryoid bodies (EBs) of mouse embryonic stem (ES) cells using a large-scale integration (LSI)-based amperometric device with 400 sensors and a pitch of 250 μm. In addition, a simulation analysis was performed to reveal the positional relationship between the EBs and the sensor electrodes toward more precise measurements. The study shows that simulation analysis can be applied for precise electrochemical imaging of three-dimensionally cultured cells by normalization of the current signals.

Electrochemical evaluation of sarcomeric α-actinin in embryoid bodies after gene silencing using an LSI-based amperometric sensor array

In the present study, gene analysis using siRNAs for cell differentiation of embryonic stem (ES) cells was performed using an LSI-based amperometric sensor array (Bio-LSI). CITED2 and WNT11 were silenced using siRNA, and then the effect of these genes on the differentiation of ES cells into cardiomyocytes was evaluated. For the evaluation, endogenous ALP activity and sarcomeric α-actinin were electrochemically detected using the Bio-LSI system. These results show the crucial role of these genes in determining the fate of differentiation of ES cells. These results also show that the Bio-LSI is a great tool for cell analysis.