Micropatterning of hyaluronic acid hydrogels for in vitro models

Abstract: The human body consist of a vast number of cells, and jointly, the cells, form tissues and organs. The cells interact and respond to their local microenvironment. The cellular microenvironment consists of a highly hydrated and compliant extracellular matrix, neighboring cells and circulating biochemical factors; and jointly, provide chemical and physical cues that regulate cell behaviour However, these cues are often not present in traditional in vitro models, where cells experience a stiff and unstructured environment. An approach to better mimic the in vivo microenvironment in vitro is to use hydrogels. Hydrogels are soft and highly hydrated polymers based on materials naturally found in the extracellular matrix of various tissues. Furthermore, these materials can be chemically functionalized to control the physical, chemical, and mechanical properties of the hydrogels. These functionalities can also be used to prepare micrometre sized cell adhesive regions, or micropatterns, on the hydrogel substrate. The micropatterns guide the cell shape and permit the study of the cell response to these changes in shape and function, which has been observed in e.g., endothelial cells from various origins. Taken all together, the aim of this work was to develop a hydrogel-based cell culture substrate that permits the control of the spatial adhesion of brain endothelial cells in order to study the morphological effects on these cells and contribute to the understanding of the function of brain endothelial cells in health and disease. This thesis demonstrates the functionalization of hyaluronic acid, a naturally occurring extracellular matrix polymer, to prepare photocrosslinkable hydrogels. Then, through photolithography, micropatterns of cell adhesive peptides were prepared on these hydrogels. Brain microvascular endothelial cells, a highly specialized type of endothelial cells, adhered to the micropatterns, and the effect on their alignment and cell chirality depending on the micropatterned sized was studied. Furthermore, changes in their alignment were also observed when exposed to different glucose concentration.