Session: 05-04-01: Biomaterials and Tissue: Modelling, Synthesis, Fabrication and Characterization - I

Paper Number: 94733

94733 - Developing a Multi-Functional Sensor for Cell Traction Force, Matrix Remodeling and Biomechanical Assays in Self-Assembled 3d Tissues in Vitro 

Introduction

Cell-matrix interactions, mediated by cellular force and matrix remodeling, result in a dynamic reciprocity that drives numerous biological processes and disease progression [1]. Currently, there is no available method for direct quantification cell traction force and matrix remodeling in 3D matrices as a function of time. To address this long-standing need, we recently developed a high-resolution microfabricated sensor that measures cell force, tissue-stiffness and can apply mechanical stimulation to the tissue [2].

Method

The sensor is made with PDMS and it integrates a tissue with cell(s) that is connected to a sensitive spring that reads cell force using force equilibrium laws. We used an innovative technique for overcoming surface tension challenges during self-assembly of the tissue from cell-extracellular matrix (ECM) mixture [3]. Brightfield imaging with a simple microscope is sufficient for observation of the cells and measuring force. In addition, the sensor can be used as an actuator for applying known tension and compression loads on the tissue sample for measurement of mechanical properties such as viscoelasticity. 

Results

With primary fibroblasts, cancer cells and neurons, we demonstrated the efficiency of the sensor by measuring single/multiple cell force (with 1 nN resolution) and change in tissue stiffness due to matrix remodeling by the cells. Compared to 2D, traction force dynamics from single cells is dramatically different in three-dimensional fibrous matrices. For example, average single cell force in 3D is lower than on 2D substrates of similar elastic modulus (~0.5 kPa). However, as the cells go through periodic contraction and relaxation, the duration of time in contraction is longer in 3D collagen compared to 2D collagen coated polyacrylamide gels. As a result, actomyosin activity and rate of force generation in 3D is also slower. Our results indicate that such difference in traction force dynamics is responsible for different cell signaling in 3D.

Utilizing the sensor, we also applied stretch and compression to the tissue by applying a prescribed motion on the supporting spring using a piezo stage. The ECM was thus subjected to tensile and compressive strains, which transferred the strains to the cell embedded in the matrix. Our results showed that the cell strain is about 93% of the tissue strain in tension and only 52% in compression. Using mechanics of fibrous matrices, such difference in response can be explained. 

Multi-cellular systems, such as cancer cells and stromal fibroblasts coculture tissue (FET human colorectal cancer cells/CAF05 human cancer associated fibroblasts) that mimics tumor microenvironment, increased tissue stiffness by three times within 24 hours. Moreover, 3D tissues made with primary mouse neurons demonstrated that these cells connect with each other, possibly by forming synapses, and generate tension with time [3]. Whether such increased force results in elevated signal transmission through synapses is yet to be explored.

Discussion

The uniaxial sensor can measure cellular forces, matrix remodeling in 3D and apply strain to cells. The system can be translated into a high-throughput system for clinical assays such as patient-specific drug and phenotypic screening. Here, we present the detailed methods for manufacturing the sensors, preparing experimental setup, developing assays with different tissues, and some new results with primary cancer associated fibroblasts and neurons.

References

[1]         Emon B, Bauer J, Jain Y, Jung B, Saif T. Biophysics of Tumor Microenvironment and Cancer Metastasis - A Mini Review. Computational and Structural Biotechnology Journal 2018;16:279–87. https://doi.org/10.1016/j.csbj.2018.07.003.

[2]         Emon B, Li Z, Joy MSH, Doha U, Kosari F, Saif MTA. A novel method for sensor-based quantification of single/multicellular force dynamics and stiffening in 3D matrices. Science Advances 2021;7:eabf2629. https://doi.org/10.1126/sciadv.abf2629.

[3]         Emon B, M Saddam H J, M Taher A S. Developing a multi-functional sensor for cell traction force, matrix remodeling and biomechanical assays in self-assembled 3D tissues in vitro. Protocol Exchange 2021. https://doi.org/10.21203/RS.3.PEX-1540/V1.

Presenting Author: Bashar Emon University of Illinois at Urbana-Champaign

Presenting Author Biography: Bashar Emon is a Ph.D. candidate in the Department of Mechanical Science and Engineering at University of Illinois at Urbana-Champaign. He earned his B.Sc. in Civil Engineering in 2012 and M.Sc. in Structural Engineering in 2014 from Bangladesh University of Engineering and Technology (BUET). Bashar is also a Beckman Institute Graduate Fellow, and he was awarded the CCIL TiME Traineeship (NIH T32) and MAVIS Future Faculty Fellowship in 2018 and 2020, respectively. Currently he is working with Prof. Taher Saif to investigate the dynamic interaction between biophysical and chemical signaling within the tumor microenvironment.

Authors:

Bashar Emon University of Illinois at Urbana-Champaign
M Saddam H Joy University of Illinois at Urbana-Champaign
M Taher A Saif University of Illinois at Urbana-Champaign