Volume-by-volume bioprinting of chondrocytes-alginate bioinks in high temperature thermoplastic scaffolds for cartilage regeneration

Abstract

Background & Aim Biofabrication technologies with layer-by-layer simultaneous deposition of a polymeric matrix and cell-laden bioinks (also known as bioprinting) offer an alternative to conventional treatments to regenerate cartilage tissue. Thermoplastic polymers, like poly-lactic acid, are easy to print using fused deposition modeling, and the shape, mesh structure, biodegradation time, and stiffness can be easily controlled. Besides some of them being clinically approved, the high manufacturing temperatures used in bioprinting applications with these clinically available thermoplastics decrease cell viability. Geometric restriction prevents cell contact with the heated printed fibers, increasing cell viability but comprising the mechanical performance and biodegradation time of the printed parts. The objective of this study was to develop a novel volume-by-volume 3D-biofabrication process that divides the printed part into different volumes and injects the cells after each volume has been printed, once the temperature of the printed thermoplastic fibers has decreased. Methods, Results & Conclusion A bioprinter with three syringes and one FDM extruder (REGEMAT 3D, Granada, Spain), was configured for PLA and used two syringes with needles to inject embedded chondrocytes in alginate bioink and a calcium solution . The Designer software can be set up to print anatomical structures, selecting how and when the bioinks are deposited. In order to avoid cell contact with the high temperature thermoplastic printed parts, VbVallows the deposition of x layers of the thermoplastic and afterwards the filling of the resulting volume with chondrocytes. The syringe containing the cell-loaded hydrogel solution will penetrate into the scaffold in different points (N points), filling it up uniformly. Human articular chondrocytes were isolated. Chondrocytes were grown and incubated at 37࿽C humidified atmosphere and expanded in a monolayer for 7–10 days before the experiment. This new procedure avoids the contact between the thermoplastic and the cells at a higher temperature than is normally physiologically viable, it can be used with already clinically approve biomaterials and does not have restrictions in geometries that could limit the clinical application of 3D bioprinting in cartilage TE. The use of a VbV 3D-biofabrication process might accelerate the clinical application of the technology and overcome the current limitation when using thermoplastics as scaffolds.