Abstract
For the generation of multi-layered full thickness osteochondral tissue substitutes with an individual geometry based on clinical imaging data, combined extrusion-based 3D printing (3D plotting) of a bioink laden with primary chondrocytes and a mineralized biomaterial phase was introduced. A pasty calcium phosphate cement (CPC) and a bioink based on alginate-methylcellulose (algMC) – both are biocompatible and allow 3D plotting with high shape fidelity – were applied in monophasic and combinatory design to recreate osteochondral tissue layers. The capability of cells reacting to chondrogenic biochemical stimuli inside the algMC-based 3D hydrogel matrix was assessed. Towards combined osteochondral constructs, the chondrogenic fate in the presence of CPC in co-fabricated and biphasic mineralized pattern was evaluated. Majority of expanded and algMC-encapsulated cells survived the plotting process and the cultivation period, and were able to undergo redifferentiation in the provided environment to produce their respective extracellular matrix (ECM) components (i.e. sulphated glycosaminoglycans, collagen type II), examined after 3 weeks. The presence of a mineralized zone as located in the physiological calcified cartilage region suspected to interfere with chondrogenesis, was found to support chondrogenic ECM production by altering the ionic concentrations of calcium and phosphorus in in vitro culture conditions.
Highlights
For the generation of multi-layered full thickness osteochondral tissue substitutes with an individual geometry based on clinical imaging data, combined extrusion-based 3D printing (3D plotting) of a bioink laden with primary chondrocytes and a mineralized biomaterial phase was introduced
We aim for the application of patient-derived cells in a spatially defined manner, according to a design defined by internal and external architecture detected via magnetic resonance imaging (MRI), along with materials enabling matrix formation
For chondrogenic bioprinting, human chondrocytes (hCh) were mixed into the blend and open-porous 3D constructs were fabricated by 3D plotting and subsequent crosslinking via 100 mM CaCl2
Summary
For the generation of multi-layered full thickness osteochondral tissue substitutes with an individual geometry based on clinical imaging data, combined extrusion-based 3D printing (3D plotting) of a bioink laden with primary chondrocytes and a mineralized biomaterial phase was introduced. A balance is needed between shear-thinning, viscoelastic behavior for printability and a network density allowing both high shape fidelity and biocompatibility for embedded cells[2] This can be achieved by applying different strategies for the generation of volumetric constructs which utilize internal (via material blending), external (via material combinations to hybrid scaffolds) or technological (through additional components of the technical printing environment) stabilization concepts[3,4]. Our group introduced the concept of multichannel plotting for co-extrusion of a mineralized biomaterial ink and bioprinting of cells: We combined the algMC-based bioink laden with hMSC with a clinically approved pasty CPC21 This material consists of a precursor powder with α-tricalcium phosphate (α-TCP) as main component and an oil-based carrier liquid to create an ink suitable for plotting without time limitation[22]
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