Creating microvasculature using 3D printing of hydrogels

3D printing has gained significant interest in recent years as a tool in additive manufacturing. Within the medical field, bioprinting has been used to develop synthetic tissues. Despite significant advances in 3D bioprinting technologies, there is a lack of understanding of various factors such as nozzle diameter in relation to cell size, nozzle length and flow rates. One other barrier is the inability to create microvasculature that exists within our tissues, to be able to go below 0.1 mm diameter during bioprinting. Printing cell-laden structures is also not widely tested, as in most cases, a fiber is printed and then cells are randomly introduced. In this study, I proposed a chitosan-gelatin hydrogel and first printed a single fiber to test how it affects cells. I investigated different concentrations of the hydrogel mixture. Different nozzle sizes were tested with the cells, analyzed them for cell area, and shape. Also, I used previously obtained data to show how nozzle size to cell size ratio affects cell morphology. Next, I created hollow fibers with 0.1 mm that can be used to form microvasculature network by using a custom-made coaxial nozzle. Using the factorial design of experiments, I tested the effect differing printing speeds and nozzle lengths, reaching a repeatable and optimal process for creating fibers with average dimensions of < 0.1 mm. I used liver sinusoidal endothelial cells during printing to mimic blood vessels. Cells survived the printing process even after 5-7 days incubation, both within the core and the shell. Although fibers were stable, there was very little cell spreading. I evaluated a different alginate-based hydrogel to check the usability of the coaxial nozzle. Every other parameter was kept the same. The alginate-gelatin mixture showed a significant increase both in cell spreading, but also in size.