Design and Development of Cell Stretching Platforms for Mechanobiology Studies

Abstract

Cells within the human body are continuously exposed to various mechanical stimuli due to organ function, movement and growth. Cellular response to such mechanical stimuli is known as a mechanobiological signalling, which is an integral part of the cell homeostasis. It is widely accepted that maladaptation of mechanobiological signalling may lead to dysfunction and/or disease. Thus, better understanding of mechanobiological signalling has become a key area of interest for researchers in the field of regenerative medicine and tissue engineering. However, complexity involved in the in vivo biological systems has been a major hurdle for comprehensive mechanobiological investigations. This technological gap motivates researchers to develop in vitro devices capable of introducing mechanical strain onto a cell culture and to closely mimic the in vivo physiological conditions. For example, various cell stretching approaches have been developed to induce mechanical strain onto a cell culture and trigger cellular responses such as migration, proliferation and orientation. However, very few existing cell stretching platforms fulfil the major requirement of a robust cell stretching tool such as high experimental throughput, well-characterised and controllable strain pattern, ease of operation, compatible with a wide range of imaging systems and most importantly high biological relevance for systematic mechanobiological investigation. Thus, the present thesis focuses on the development of robust cell stretching platforms based on electromagnet and pneumatic actuations to address these existing limitations and subsequently to establish a systematic approach for in-depth mechanobiological investigation. To provide a systematic approach for detailed study, the first necessary step is quantification of the parameter. Thus, in the Chapter three of this thesis, a novel cell stretching platform based on a single sided uniaxial stretching approach was developed to apply tensile strain onto the cell culture and observe cellular response of the cells towards different strains in the same field of view with lower fabrication and operation complexity. The effectiveness of the platform was demonstrated by observing the response of cells in culture under different strain amplitudes. In the Chapter four, a standardised numerical tool was developed for the singlesided uniaxial cell stretching platform. The numerical tool provided guidelines for the optimization parameters and paved way for the development of a double-sided cell stretching platform described in Chapter five. The developed platform was capable of investigating the cellular behaviour for a wide range of homogenous strain amplitudes with cyclic and static stretching conditions. Although the developed electromagnetically cell stretching platforms provided a standardised tool for systematic mechanobiological investigation, the biological relevance could still be improved. Thus, the Chapter six involved the development of a novel pneumatically actuated array-based cell stretching platform, which concurrently induced a range of cyclic strain onto the cell culture. It was developed to achieve cell patterns, which provided an improved biological relevance for mechanobiological studies. The toroidal shaped strain pattern was utilised to achieve circumferential cellular alignment of cells similar to that of in vivo smooth muscle in the vascular wall. Furthermore, the dimensions of the platform followed those of standard 96 well plates. This simple and effective design approach ensured a high compatibility with pre-clinical tools and protocols, which is critical for highthroughput cell-stretching assays. Collectively, the findings for these chapters and the thesis at large, suggest the high clinical compatibility and biological relevance of the cell stretching devices reported in this thesis provide promising platform for systematic mechanobiological investigations.