A Flexible Microdevice for Mechanical Cell Stimulation and Compression in Microfluidic Settings

Abstract

Evidence continues to emerge that cancer is a disease not only of genetic mutations, but also of altered mechanobiological profiles of the cells and microenvironment. This mutation-independent element might be a key factor in promoting development and spread of cancer. Biomechanical forces regulate tumor microenvironment by solid stress, matrix mechanics, interstitial pressure, and flow. Compressive stress by tumor growth and stromal tissue alters cell deformation and recapitulates the biophysical properties of cells to grow, differentiate, spread, or invade. Such solid stress can be introduced externally to change the cell response and to mechanically induce cell lysis by dynamic compression. In this work, we report a microfluidic cell culture platform with an integrated, actively modulated actuator for the application of compressive forces on cancer cells. Our platform is composed of a control microchannel in a top layer for introducing external force and a polydimethylsiloxane (PDMS) membrane with monolithically integrated actuators. The integrated actuator, herein called micro-piston, was used to apply compression on SKOV-3 ovarian cancer cells in a dynamic and controlled manner by modulating applied gas pressure, localization, shape, and size of the micro-piston. We report fabrication of the platform, characterization of the mechanical actuator experimentally and computationally, and cell loading and culture in the device. We further show the use of the actuator to perform both repeated dynamic cell compression at physiological pressure levels and end point mechanical cell lysis, demonstrating suitability for mechanical stimulation to study the role of compressive forces in cancer microenvironments. Finally, we extend cell compression applications in our device to investigating mechanobiologically related protein and nuclear profiles in cyclically compressed cells.

Application of sequential cyclic compression on cancer cells in a flexible microdevice

“…To extend on what is possible with existing systems and increase robustness of cyclic cell compression results, control of the pressure application was optimized by evaluating the effect of device fabrication variations. To recall dimensions of the micro-piston device we developed in [5], the height of the cell culture channel was on average 313 µm, while micro-pistons were measured as around 206 µm in PDMS replicas. Once assembled, the gap these layers created between the bottom of the micro-piston and the glass surface was measured as on average 108 µm.…”

“…A previously developed finite element model (FEM) based on hyperelastic Saint Venant-Kirchhoff theory for actuation of the flexible microdevice [5] SKOV-3 cells at a seeding density of 1.5 × 10 6 cells/ml were loaded using piston-retracted loading. In this method of chip loading with cells, the PDMS membrane with the attached micro-piston was retracted out of the culture channel towards the top control channel using an applied negative pressure of 615 (-615) mbar to favour flow of seeding solution for homogenous distribution of cells.…”

“…While some cells experience permanent plastic deformation after a repetitive mechanical tensile loading and unloading, the impact of such repetitive compression on plastic deformation of cells remains unknown [1,2]. As such, the ability to apply cyclic compression is crucial for any experimental setup aimed at the study of mechanical compression taking place in cell and tissue microenvironments [3][4][5]. For instance, in ovarian cancer, cells are exposed to chronic compressive stress from different sources such as tumour growth, displacement within stromal tissue and hydrostatic pressure out January 8, 2022 1/18 of ascitic fluid in peritoneal cavity [3,6].…”

“…With the purpose of applying compression in a cyclic, dynamic, and controlled manner for the investigation of cell deformation and recovery, we have developed a robust cyclic compression microfluidic method based on a flexible microdevice, which provides extensive control of the amount, duration, and mode within a pressure profile. Fabrication and characterization of the multilayer microfluidic platform, the observation of directional growth of cells and mechanical cell lysis as an end point assay under static state and highly pressurized state within this platform were demonstrated previously [4,5].…”

Modeling the Tumor Microenvironment of Ovarian Cancer: The Application of Self-Assembling Biomaterials

“…Several strategies have been developed to add biomechanical cues into microfluidic devices, such as the application of shear stresses or compression forces, to better study cancer progression and chemoresistance. For example, Onal et al created a microfluidic device integrated with actuators to apply compression on SKOV-3 cells [ 172 ]. It has been reported that cells under compression stimulation displayed invasive morphology, increased proliferation and chemoresistance [ 173 ].…”