Microfluidic Selection and Retention of a Single Cardiac Myocyte, On-Chip Dye Loading, Cell Contraction by Chemical Stimulation, and Quantitative Fluorescent Analysis of Intracellular Calcium

A microfluidic method to study the contraction of a single
cardiac myocyte (heart muscle cell) has been developed.
This method integrates various single-cell operations as
well as on-chip dye loading, and quantitative analysis of
intracellular calcium concentration, [Ca2+]i. After the
channel enlargement by on-chip etching to accommodate
large-sized cardiac myoytes, a single cell is selected and
retained at a V-shaped cell retention structure within the
microchip. Owing to the fragile property of the cardiac
myocytes that could easily be damaged by centrifugation,
the calcium-sensitive fluorescent dye was loaded in the
cell by on-chip dye loading. This on-chip method minimized the damage to the cells from the use of a centrifuge
in the conventional method and provided a way of cellular
analysis of fragile cells. Subsequently, quantitative analysis of [Ca2+]i of a single cardiac myocyte by fluorescence
measurement was achieved for the first time in a microfluidic chip, thanks to the intracellular calcium stimulant
of ionomycin. The resting [Ca2+]i of the cardiomyocyte
determined was consistent with the literature value. From
the spontaneous contraction study, it was found that
fluorescence intensity cannot represent the [Ca2+]i variation accurately, which implied the importance of the
quantitative analysis of [Ca2+]i.