Abstract
Mechanical forces are integral to cellular migration, differentiation and tissue morphogenesis; however, it has proved challenging to directly measure strain at high spatial resolution with minimal perturbation in living sytems. Here, we fabricate, calibrate, and test a fibronectin (FN)-based nanomechanical biosensor (NMBS) that can be applied to the surface of cells and tissues to measure the magnitude, direction, and strain dynamics from subcellular to tissue length-scales. The NMBS is a fluorescently-labeled, ultra-thin FN lattice-mesh with spatial resolution tailored by adjusting the width and spacing of the lattice from 2–100 µm. Time-lapse 3D confocal imaging of the NMBS demonstrates 2D and 3D surface strain tracking during mechanical deformation of known materials and is validated with finite element modeling. Analysis of the NMBS applied to single cells, cell monolayers, and Drosophila ovarioles highlights the NMBS’s ability to dynamically track microscopic tensile and compressive strains across diverse biological systems where forces guide structure and function.
Highlights
Mechanical forces are integral to cellular migration, differentiation and tissue morphogenesis; it has proved challenging to directly measure strain at high spatial resolution with minimal perturbation in living sytems
The nanomechanical biosensor (NMBS) is fabricated using an adaptation of surfaceinitiated assembly (SIA), which is a technique to microcontact print extracellular matrix (ECM) proteins onto a thermo-responsive poly(N-isopropylacrylamide) (PIPAAm) surface and release the ECM proteins (e.g., FN, laminin, collagen type IV, and fibrinogen) as an assembled, insoluble network with defined geometry[31]
Computeraided design (CAD) software is used to define the geometry of the mesh, and in this initial work, we selected a square-lattice mesh because we can change the width and spacing of the fibers based on the experimental purpose
Summary
Mechanical forces are integral to cellular migration, differentiation and tissue morphogenesis; it has proved challenging to directly measure strain at high spatial resolution with minimal perturbation in living sytems. Advanced optical techniques have been developed including live cell imaging-based optical sensors (Förster resonance energy transfer, FRET)[26], fluorescence based oil microdroplets21, 2D and 3D traction force microscopy[24,25,27], birefringence[28], and force inference[29] Together, these methods have advanced the fields of biomechanics and mechanobiology, and provided insights into the role of biological forces in cell and tissue development and function. There remains a need for a method that can combine (i) direct measurement of strain, (ii) high spatial and temporal resolution, (iii) tracking and mapping in both 2D and 3D, and (iv) minimal perturbation of the cell or tissue system. We demonstrate the ability to directly quantify cellgenerated 3D tensile and compressive mechanical strains at both cellular and multicellular resolution by applying the FN-based NMBS to the surface of single cells, cell monolayers, and developing tissues
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