Probing cellular mechanics with acoustic force spectroscopy

Abstract

A large number of studies demonstrate that cell mechanics and pathology are intimately linked. In particular, deformability of red blood cells (RBCs) is key to their function and is dramatically altered in the time course of diseases such as anemia and malaria. Due to the physiological importance of cell mechanics, many methods for cell mechanical probing have been developed. While single-cell methods provide very valuable information, they are often technically challenging and lack the high data throughput needed to distinguish differences in heterogeneous populations, while fluid-flow high-throughput methods miss the accuracy to detect subtle differences. Here we present a new method for multiplexed single-cell mechanical probing using acoustic force spectroscopy (AFS). We demonstrate that mechanical differences induced by chemical treatments of known effect can be measured and quantified. Furthermore, we explore the effect of extracellular vesicles (EVs) uptake on RBC mechanics and demonstrate that EVs uptake increases RBC deformability. Our findings demonstrate the ability of AFS to manipulate cells with high stability and precision and pave the way to further new insights into cellular mechanics and mechanobiology in health and disease, as well as potential biomedical applications.

An acoustic platform for single-cell, high-throughput measurements of the viscoelastic properties of cells

“…For the assay described here, the best contrast is given by 9.2 µm Silica particles with at least an 0.75 NA objective ( Supplementary Figure S2). At this magnification, our field of view typically captures 10 to 40 cells (Figure 2e), however, depending on cell size, objective magnification and NA, several hundred cells can potentially be recorded simultaneously with potentially single-digit nanometer resolution 13 . On average, a single 60-minute experiment yields 80 -180 creep-force curves (Figure 2f) with a cell confluence of 60-80%.…”

“…Many techniques have been developed to study the mechanical properties of cells 6,7 , these include magnetic twisting cytometry (MCT) 8 , atomic force microscopy (AFM) 9 , optical tweezers (OT) 2 , micropipette aspiration and particle tracking microrheology (PTMR) 11 . Recently, acoustic force spectroscopy (AFS) has emerged as an alternative method for providing high-throughput tracking at single-cell resolution 12,13 . Conceptually, the AFS is similar in operation to Optical Tweezers.…”

“…When optically trapped, membrane-attached single particles (a.k.a handles) are pulled away from the cell surface, a thin tether is formed. Likewise, the AFS utilizes acoustically driven, membrane-attached particles as "handles" for pulling tethers from 30 to 50 cells simultaneously 13 . As such, the AFS has great potential as a diagnostic tool for characterizing the mechanical properties of adherent cells.…”

“…As such, the AFS has great potential as a diagnostic tool for characterizing the mechanical properties of adherent cells. Previously, the AFS was used to characterize the mechanical properties of red blood cells exposed to a variety of chemical treatments, including changes to the lipid membrane by vesicle fusion 13 . Recently, the AFS was used to measure the complex shear modulus of human umbilical vein endothelial cells 14 .…”

Microchip based microrheology via Acoustic Force Spectroscopy shows that endothelial cell mechanics follows a fractional viscoelastic model

“…41,42 Recently, the AFS has been used to stretch red blood cells under a constant force on attached particles to measure their static spring constant. 43 In our work, we apply a custom, time-varying, oscillatory force on particles that are attached on a monolayer of primary human umbilical vein endothelial cells (HUVEC). With this new method the results using the AFS can be compared with other techniques, such as AFMs.…”