In a significant breakthrough, researchers have successfully combined volumetric bioprinting with melt electrowriting for the first time, as revealed in a study published in Advanced Materials. Led by the biofabrication lab of Regenerative Medicine Center Utrecht (RMCU), this innovative approach merges the speed and cell-friendly nature of volumetric printing with the structural strength required for the creation of functional blood vessels.

Volumetric printing, a technique pioneered by the RMCU biofabrication lab in 2019, offers rapid printing while enabling cells to survive the process. However, the resulting prints lack structural integrity due to the use of cell-friendly gels. This poses a challenge for blood vessels, which must endure high pressures and bending. To overcome this limitation, researchers aimed to combine volumetric bioprinting with melt electrowriting.

Melt electrowriting is a highly precise 3D printing method that utilizes a narrow filament of molten biodegradable plastic. It can produce intricate scaffolds with excellent mechanical strength capable of withstanding external forces. However, the high temperatures involved prevent the direct printing of cells. To address this, volumetric bioprinting was employed to solidify cell-laden gels onto the scaffolds.

The process begins by creating a tubular scaffold using melt electrowriting, followed by submerging it into a vial containing photoactive gel and placing it in the volumetric bioprinter. The printer’s laser selectively solidifies the gel within, on, and/or around the scaffold. First author Gabriël Größbacher explains the challenge of aligning the scaffold perfectly in the vial, stating that any deviation from the center would misalign the volumetric print. The team achieved precise centering by printing the scaffold on a mandrel customized to fit the vial.

In the study, Größbacher and colleagues tested different scaffold thicknesses, resulting in tubes of varying strength. They also explored different placements of the bioprinted gels—either on the inner side, inside the scaffold, or on the outside. By using two distinctively labeled stem cells, the researchers successfully printed a proof-of-concept blood vessel with two layers of stem cells and seeded epithelial cells in the center to cover the vessel’s lumen. The design even allowed for the incorporation of holes in the vessel’s side, enabling controlled permeability for blood functionality. The team further created complex structures such as forked vessels and vessels with functional venous valves to maintain unidirectional flow.

According to Größbacher, this study serves as a proof of principle. The next step involves replacing the stem cells with functional cells found in actual blood vessels, including muscle cells and fibrous tissue surrounding the epithelial cells. The ultimate goal is to successfully bioprint a functional blood vessel, marking a significant advancement in the field of regenerative medicine.

By Impact Lab