A flexible, quantum dot-labeled cantilever post array for studying cellular microforces

We describe improvements to a passive array of cantilevers, termed the bed of nails (BoN), for detecting cellular microforces and studying in vitro cell mechanics. The BoN consists of vertically-arranged PDMS posts that behave as simple cantilever beams when stressed horizontally by cells cultured on them. We modified the standard SU8 protocols to include a contrast enhancement step that removed air-gap effects and enabled fabrication of 2 μm features using contact I-line UV photolithography. We also contact-printed the tops of each post with quantum dot labels that are easily visualized with fluorescence microscopy and that do not interact with cells. To illustrate these improvements, we focus this paper on human airway smooth muscle (HASM) cells, although the system can be generalized to other cell types. We demonstrate how the BoN is a cost-effective, user-friendly system that can be implemented in a relatively short period of time by researchers in asthma and other fields who wish to conduct short-term and long-term studies to examine cellular microforces in vitro.