Micro-extrusion 3D printing of articular cartilage substitutes with a multizonal structure using hydrophilic and rapidly curing silicone-based ink materials

Although silicone elastomers have been extensively used for biomedical applications, 3D printing silicone remains challenging due to their long curing-time, low-viscosity, and hydrophobic nature. In this work, hydrophilic and rapidly curing (under three seconds) inks, consisting of aminosilicone, cellulose nanocrystal (CNC), and methacrylate anhydride (MA), are developed for the printing of human articular cartilage (HAC) substitutes, with a biomimetic multizonal structure, for the first time. The developed inks are shown to possess a suitable shear-thinning property and tunable mechanical strengths for 3D micro-extrusion printing. This work demonstrates the printability of high aspect ratio and hemispherical structures without any sacrificial supports. The necessary HAC mechanical stiffnesses can be achieved by printing with aminosilicone inks containing different CNC and MA concentrations. A multilayered HAC with compressive moduli ranging from 0.25 to 1.32 MPa is successfully produced. The 3D-printed HAC's endurance against 400 cyclic compressions is also assessed. Lastly, a customized HAC is also printed to cover human femoral condyles to ensure its gripping and shape compatibility to be used as human substitutes. This study presents a new class of silicone-based inks that can be utilized not only for the fabrication of personalized and biocompatible tissue-mimetic models but also for in-situ surgical applications.