Suspending nanoliter droplet arrays for cell capture and copper ion stimulation

In this paper, we developed a microdevice with raised cylinder arrays for capture of Chlorella vulgaris cells and kinetic analysis of stimulation. The cell solution was injected into the chip and held in the gaps between the opposite raised cylinders, forming 0.314 nL volume of suspending droplets. The number of the captured cells in each nanoliter suspending droplet could be controlled within five under our experiment conditions. When the stimulation reagent of copper ion (Cu2+) was injected into the chip and contacted with the suspending droplets, gradient concentration of Cu2+ stimulation to the captured C. vulgaris cells by free diffusion was formed. The bioabsorption kinetic process of C. vulgaris cells under continuous Cu2+ stimulation was investigated and the two-step bioabsorption process was revealed clearly. The Cu2+ toxicity accumulation effect on the cell was also studied by monitoring the fluorescence of cellular chlorophyll.