Polyacrylamide Bead Sensors for in vivo Quantification of Cell-Scale Stress in Zebrafish Development

Abstract

Mechanical stress exerted and experienced by cells during tissue morphogenesis and organ formation plays an important role in embryonic development. While techniques to quantify mechanical stresses in vitro are available, few methods exist for studying stresses in living organisms. Here, we describe and characterize cell-like polyacrylamide (PAAm) bead sensors with well-defined elastic properties and size for in vivo quantification of cell-scale stresses. The beads were injected into developing zebrafish embryos and their deformations were computationally analyzed to delineate spatio-temporal local acting stresses. With this computational analysis-based cell-scale stress sensing (COMPAX) we are able to detect pulsatile pressure propagation in the developing neural rod potentially originating from polarized midline cell divisions and continuous tissue flow. COMPAX is expected to provide novel spatio-temporal insight into developmental processes at the local tissue level and to facilitate quantitative investigation and a better understanding of morphogenetic processes.

Under pressure: Hydrogel swelling in a granular medium

“…We use these measurements, summarized in fig. S3B, to calculate the hydrogel shear modulus G via the relation G = E /2(1 + ν), using ν ≈ 0.45 as previously measured ( 59 ). We compare the measured values to the prediction from network elasticity ( 30 ), G = k B TN c / V , where N c is the number of polymer chains in a hydrogel particle of volume V , which yields N c ≈ 5 × 10 18 .…”

Mechanical properties of cell- and microgel bead-laden oxidized alginate-gelatin hydrogels

“…PAAm microgel beads have shown the potential to mimic cells with respect to their diameter and elasticity, and to allow for a comparison between different mechanical assessment techniques, such as atomic force microscopy (AFM) and real-time deformability cytometry (RT-DC). 91 Due to their mechanical similarities to cells, PAAm beads have been used as stress sensors, [91][92][93] for the calibration of RT-DC measurements, 94 and to build 3D colloidal scaffolds with spatially differing mechanical layers for cell growth, migration and mechanosensitivity studies. 95 Here, we investigate the mechanical properties of hydrogels containing PAAm microgel beads and embryo mouse fibroblast (NIH/ 3T3) cells for small and large deformations under compression, tension, and torsional shear loadings.…”

Revisiting tissue tensegrity: Biomaterial-based approaches to measure forces across length scales

“… 152 While certain sensors rely on pressure-induced fluorophore diffusion 213 or local FRET-based changes in fluorescence due to deformations 215 to quantify stresses, they require extensive characterization and calibration to be used in vivo . Tracking the deformation of beads within multi-layered cell sheets, 216 spheroids, 152,211,216 and zebrafish embryos 214,216 has been shown to resolve tissue pressure and cell-generated force profiles throughout tissues and development. Lee et al used this system to demonstrate that a “skin” of tension forms on the periphery, while compressive stresses build up towards the core of fibroblast spheroids [ Fig.…”