Probing the coupled adhesion and deformation characteristics of suspension cells

Abstract

By combining optical trapping with fluorescence imaging, the adhesion and deformation characteristics of suspension cells were probed on single cell level. We found that, after 24 h of co-culturing, stable attachment between non-adherent K562 cells and polystyrene beads coated with fibronectin, collagen I, or G-actin can all be formed with an adhesion energy density in the range of 1–3×10−2 mJ/m2, which is about one order of magnitude lower than the reported values for several adherent cells. In addition, it was observed that the formation of a stronger adhesion is accompanied with the appearance of a denser actin cell cortex, especially in the region close to the cell-bead interface, resulting in a significant increase in the apparent modulus of the cell. Findings here could be important for our understanding of why the aggregation of circulating cells, like that in leukostasis, takes place in vivo as well as how such clusters of non-adherent cells behave. The method proposed can also be useful in investigating adhesion and related phenomena for other cell types in the future. This work was supported by a grant from the Research Grants Council (Project No. HKU 7143/12E) of the Hong Kong Special Administration Region as well as a seed fund (Project No. 201211159001) from The University of Hong Kong. J.Q. acknowledges support from the National Natural Science Foundation of China (Nos. 11202184 and 11321202).