Cellular calcium oscillations in droplets with different chemical concentrations supplied by droplet-array sandwiching technology

Abstract

Digital microfluidics using droplets on a chip, such as droplet-array sandwiching technology, provide efficient tools for biochemistry from the perspective of time and sample consumption. Droplet-array sandwiching technology uses the fusion and separation of droplets on upper and lower substrates for high-throughput screening. In our previous work, we developed independent control of individual droplets for this technology using electrowetting-on-dielectric to control the droplet height and allow different chemical concentrations in droplets on the same chip. In this study, we explored the applicability of droplet-array sandwiching technology to cell-based analysis by observing cellular calcium oscillations in HeLa cells in droplets with different histamine concentrations. Histamine concentrations could be controlled by controlling contact time between upper and lower droplets. We found that calcium oscillations intensified with higher histamine concentrations prepared by controlling contact time. These results suggest that droplet-array sandwiching technology can be used for cell-based analysis, where the chemical concentration for cellular stimulation needs to be controlled.