Freestanding vascular scaffolds engineered by direct 3D printing with Gt-Alg-MMT bioinks

There is an urgent need for vascular scaffolds as a treatment option for cardiovascular diseases in the clinic. Here, we developed a simple and effective method to fabricate vascular scaffolds by direct 3D printing in air with gelatine (Gt) - alginate (Alg) - montmorillonite (MMT) nanocomposite bioinks. This work includes the optimization of key 3D printing parameters and the characterization of microscopic morphology, physicochemical properties, mechanical properties and preliminary biological properties. Successful 3D printing of linear and branched vascular scaffolds showed that the addition of nano-MMT improved the printability and shape accuracy. Scanning electron microscopy revealed that the inner and outer surfaces of the vascular scaffolds exhibited interconnected microporous structures favourable for nutrient delivery and cell infiltration. Axial and radial tensile tests indicated that the tensile strength and elastic modulus were similar to those of the native artery. The burst pressure of Gt-4%Alg-MMT was also in good accordance with the physiological pressure of natural blood vessels. In addition, a haemolysis test demonstrated that the haemolysis rate of Gt-4%Alg-MMT matched the gold standard of blood vessel substitution. A Live & Dead stain and a CCK-8 test confirmed the safe applicability of Gt-Alg-MMT as a biomaterial. Overall, the 3D-printed vascular scaffolds are promising candidates for in situ vascular tissue regeneration.