Fabrication of highly perfusable gelatin-methacryloyl (GelMA) constructs using flow-based strategies

Abstract

One of the most important challenges when engineering tissues in vitro is the creation of viable thick constructs. The diffusion of gas and nutrients severely limits the size of engineered constructs. Therefore, the incorporation of perfusable lumen structures within thick engineered tissues is needed for enabling gas exchange, perfusion of nutrients, and waste removal down to the depth of the tissue. Current biofabrication techniques used to create perfusable networks in thick 3D constructs are limited in resolution and control, and they require sophisticated or expensive tools. In this work, we propose a simple technique to develop perfusable hydrogel constructs based on the use of a 3D flow-based biofabrication technique, namely the mini Journal Bearing (mJB), and by employing sacrificial inks. Through the action of regular flows induced in a mJB and the flow-advection of two different hydrogels, we created constructs with an internal sacrificial structure. We used gelatin methacryloyl (GelMA) as a permanent hydrogel matrix, and a drop (100 µL) of gelatin as a fugitive ink/bioink. Here we present a thorough characterization of the microarchitecture and porosity of these constructs. Especially, we demonstrated how permeability increased within these constructs. Additionally, aiming to mimic the architectural complexity of natural tissues, we added nanotopographical cues to our constructs by the incorporation of elongated flexuous plant viruses, namely Turnip Mosaic Virus (TuMV). We conducted our in vitro experiments using myoblasts cells as a biological model and characterized their biological response through time. We fabricated three different types of cell-laden-constructs: GelMA with suspended cells, GelMA with a gelatin ink loaded with cells, and GelMA with a gelatin ink loaded with cells and TuMV. Cells were able to grow faster and for longer in GelMA/gelatin constructs than in pristine-GelMA constructs. While an intricate network of cells was developed after 28 days of culture within permeabilized GelMA/gelatin constructs, only surface proliferation was observed in dense constructs made exclusively with GelMA. The use of GelMA/gelatin-TuMV had an evident morphological effect on cell attachment and proliferation. TuMV 3D meshes providing additional scaffolding within the lumina. While myoblast alignment was strongly evident in GelMA/gelatin where cells adhered mainly to the lamellae walls, in GelMA/gelatin-TuMV constructs, cells alignment was attenuated by interaction with the 3D micromesh of TuMV.