The manufacture and application of joint-on-a-chip via 3D bioprinting

Abstract

Osteoarthritis (OA), the commonest joint disorder, is a primary cause of chronic disability and pain in the elderly. OA affects over 500 million people worldwide; unluckily, there is no cure for OA till now. With the development of tissue engineering technology, in vitro three-dimensional (3D) model provides a new approach for understanding of OA pathology and paves a road for drug discovery. Among these 3D tissue model, organ-on-a-chip attracts lots of research interest due to its high-throughput and reproducible characters. However, pre-existing joint-on-a-chip systems are lacking a circulation system comprising of a blood flow circulation system (nutrient transportation for bone) and a synovial flow circulation system (nutrient transportation for cartilage). Herein, we design and bio-fabricate a novel prototype of double-circulation joint-on-a-chip via 3D bioprinting. To set up this joint-on-a-chip device, we purposely design and synthesize two kinds of bioinks, these are bone/cartilage bioink [methacrylated Alg (AlgMA)/methacrylated ε-polylysine (ε-PLMA)] and blood vessel bioink [granular methacrylated gelatin (G-GelMA)]. 1) Bone/cartilage bioink: The incorporation of ε-PLMA in AlgMA bioinks enhances their operability and stability because of the covalent bonding and electrostatic interaction link between the two components. This improvement surpasses the performance of using single molecular Ca2+ or large molecular methacrylated gelatin as a pre-crosslinker. Moreover, the AlgMA/PLMA constructs regulate a charged microenvironment (from -345.25 mV to 121.55 mV) and exhibit enhanced hydrophilicity (26.64° to 52.00°). As a result, cells within the plotted AlgMA/PLMA structures demonstrate enhanced viability and vitality. 2) Blood vessel bioink: Due to the intermolecular bridge force between each independent microgel, the G-GelMA gain a great rheological property which significantly improve its printability. Furthermore, this physical modification does not change the chemical structure of the polymer chain. In other words, it remains the high biocompatibility of gelatin to provide a cell benefit environment. After the design of bioink system, we use Rhinoceros to establish the 3D model and related G-code of this joint-on-a-chip. We put bone/cartilage bioink and blood vessel bioink into single-nozzle channel and coaxial-nozzle channel, respectively. Controlled by a computer, the bioprinter process the movement and the pressure on/off to fabricate this chip layer by layer according to the G-code. To support the joint tissue and provide a seamless perfusable chip system, we further design a flow chamber for long-time culture. Finally, through using multichannel bioprinting and coaxial bioprinting techniques, we successfully set up this joint tissue system and correlated flow chamber in vitro. In the future, we will use this joint-on-a-chip system to discover the relationship between endothelial dysfunction and OA pathophysiology. Furthermore, we will conduct drug screening test for potential compounds. We believed that this joint model is a promising start for joint disease study and could be used as a high throughput drug screening platform in future.