(B-65) Controlled surface micropatterning method using shrinkable hydrogel

Introduction:: Controlling surface patterns in hydrogels is an essential aspect in the development of hydrogel-based biomaterials. These structures have been widely used for different applications from sensors and microfluidic devices to controlling cellular behavior in tissue regeneration purposes. Various techniques have been used to create controlled surface patterns, including microfabrication and electrospinning. In this paper, we proposed a novel low-cost strategy for controlling surface micropatterns using polyethylene glycol diacrylate (PEGDA) hydrogel. The surface topography of low concentrations of PEGDA after shrinking and the mechanical properties of this hydrogel allowed us to be able to transform these random patterns into controlled and aligned micropatterns using confined polydimethylsiloxane (PDMS) molds.

Materials and Methods:: The fabrication process consists of 3-D printing hollow structures in different sizes. The next step would be making PDMS molds out of the printed structures with different pillar sizes and then using the molds to make PEGDA blocks. PEGDA is a hydrogel that can be photocrosslinked with UV light and its size could change significantly after the dehydration and drying process. In low-concentration PEGDA the shrinking process causes formation of random patterns on the surface of samples. Using the confined PDMS molds and the best concentration of PEGDA, we were able to align these patterns in a controlled linear structure. We were then able to induce alignment in cultured cells. Different cell lines were cultured on the patterned surfaces and demonstrated a linear organization corresponding to the substrate’s patterns.

Results, Conclusions, and Discussions:: In this project, we were able to control the patterns of the hydrogel surface in a linear way. First, we were able to characterize the random surface patterns of PEGDA blocks changing contributing factors, including PEGDA concentration, photoinitiator concentration, crosslinking time, and the hydrogel block thickness. For example, by changing the concentration of PEGDA, we could show that these patterns are formed on the surface of 8% to 22% PEGDA blocks, however, the length and intensity of the patterns are increased and then decreased for concentrations higher than 16%. Increasing the concentration of the photoinitiator, though, had a significant increasing effect on the intensity and length of these patterns. Then we used the best conditions to form confined hydrogel blocks for controlled surface patterning. We were able to demonstrate that the forces applied on PEGDA blocks during dehydration and shrinking allows the random patterns to be aligned on the surface of samples. Then we showed linear cell organization caused by the patterns of our substrate’s surface. We were able to show change in the cellular behavior of Human Dermal Fibroblasts and C2C12 myoblasts, which play crucial roles in the regeneration of muscle and skin tissue.

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