Centrifugation-Assisted Single-Cell Trapping in a Truncated Cone-Shaped Microwell Array Chip for the Real-Time Observation of Cellular Apoptosis.

Microfluidic devices have been extensively used in single-cell assays. However, most of them have complicated structures (multiple layers, valves, and channels) and require the assistance of a pump or pressure-controlling system. In this paper, we present a facile centrifugation-assisted single-cell trapping (CAScT) approach based on a truncated cone-shaped microwell array (TCMA) chip for real-time observation of cellular apoptosis. Our method requires neither a pump nor a pressure-controlling system, and it greatly reduces the complexity of other cell-trapping devices. This method is so fast and efficient that single-cell occupancy could reach approximately 90% within a few seconds. Combined with modern fluorescence microscopy, CAScT makes the highly ordered and addressable TCMA a high-throughput platform (10(4)-10(5) single-cell trapping sites per cm(2)) for single-cell analysis. Cells trapped in it could be exposed to various chemicals by directly immersing it in bulk solutions without the significant loss of cells due to the truncated cone shape of the microwells. As a proof of concept, we demonstrated the ability of our chip for the real-time observation of the apoptosis of single HeLa cells induced by the common anticancer drug doxorubicin. This simple, robust, and efficient approach possesses great potential in diverse applications, such as drug screening, biosensing, and fundamental biological research.