Applying Layer-by-Layer Photo-Crosslinking in Green Bioprinting: Shape Fidelity and Cell Viability of Printed Hydrogel Constructs Containing Algae Cells

Three-dimensional printing of hydrogel constructs containing algae cells, also known as green bioprinting, has many potential applications. Its feasibility has been demonstrated for removing metal contaminants in water and tissue engineering. However, in reported studies on green bioprinting so far, shape fidelity was either not investigated or poor. This paper reports a study to apply layer-by-layer photo-crosslinking in extrusion-based 3D printing of constructs using gelatin methacryloyl (GelMA) bioink containing Chlamydomonas reinhardtii algae cells. Shape fidelity and cell viability are compared between constructs printed by applying layer-by-layer photo-crosslinking and those printed by applying once-post-printing photo-crosslinking. Comparisons of shape fidelity are also made with alginate-methylcellulose constructs printed by applying ionic-crosslinking. Results show that GelMA constructs printed by applying layer-by-layer photo-crosslinking have the highest shape fidelity among all printed constructs, and about three-quarters of the algae cells in all printed GelMA constructs are alive four days post-printing. There are no significant differences in cell viability between the GelMA constructs printed by applying layer-by-layer photo-crosslinking and the GelMA constructs printed by applying once-post-printing photo-crosslinking.