3D Printing of Porous Cell-Laden Hydrogel Constructs for Potential Applications in Cartilage Tissue Engineering

Abstract

Hydrogels are particularly attractive as scaffolding materials for cartilage tissue engineering because their high water content closely mimics the native extracellular matrix (ECM). Hydrogels can also provide a threedimensional (3D) microenvironment for homogeneously suspended cells that retains their rounded morphology and thus facilitates chondrogenesis in cartilage tissue engineering. However, fabricating hydrogel scaffolds or cellladen hydrogel constructs with a predesigned external shape and internal structure that does not collapse remains challenging because of the low viscosity and high water content of hydrogel precursors. Here, we present a study on the fabrication of (cell-laden) alginate hydrogel constructs using a 3D bioplotting system supplemented with a submerged cross-linking process. Swelling, mechanical properties and protein release profiles were examined and tuned by controlling the initial cross-linking density. Porous cell-laden alginate hydrogel constructs were also fabricated and cell viability, cell proliferation, and cartilaginous ECM deposition were investigated. The fabrication technique and the hydrogel scaffolds obtained supported high cell viability and the deposition of cartilaginous ECM, demonstrating their potential for applications in the field of cartilage tissue engineering.

Influence of crosslinking on the mechanical behavior of 3D printed alginate scaffolds: Experimental and numerical approaches

“…In some tissue engineering applications, such as peripheral nerve (Ning et al, 2016), bone (Naghieh et al, 2016b), and articular cartilage (You et al, 2016b) regeneration, scaffolds undergo compressive force exerted by over-and underlying tissues in one direction. In such cases, the compressive elastic modulus is important in one direction while the scaffold mechanical behavior in other directions might be different; indeed, bioprinted scaffolds are not isotropic (Olubamiji et al, 2016).…”

“…Among various divalent ions, Ca 2+ ions facilitate superb printability for alginate precursors while maintaining reasonable cell viability (Swioklo et al, 2016). Mechanically stable alginate scaffolds can be successfully fabricated using CaCl2 solution at higher concentrations (You et al, 2016a), but the incorporated cells can be adversely affected (Cao et al, 2012). Therefore, extruding the alginate precursor into a lower concentration CaCl2 solution has been recommended to limit effects on cell viability (Tabriz et al, 2015).…”

Recent cell printing systems for tissue engineering

“…The submerged-in-crosslinker cell printing process, referred to as drop-on-demand printing, has been applied to the inkjet [39,40] , laser-assisted [41] , and extrusion-based [42,43] cell printing processes to build 3D structures with relatively low-viscosity bioinks. Xu et al [39] and Boland et al [40] built the drop-on-demand printing apparatus shown in , which uses a layer-by-layer-sinking plate in the crosslinker-filled chamber, and the alginate-based bioink was printed on the surface of the crosslinking liquid.…”

“…applied a similar method to the laser-assisted cell printing process, which contains the same limitations in printing 3D structures, and they were able to fabricate a 3D structure with a height of 9.5 mm. Conversely, You et al [42] fabricated a 3D lattice structure with cell-laden alginate hydrogel via an extrusion-based cell printing process with submerged crosslinking. They coated the surface of a printing plate, instead of using a lifting stage, and printed the bioink in a CaCl 2 solution to build a biaxially porous 3D scaffold, which created pores between the deposited layers.…”

Tissue-Specific Bioink from Xenogeneic Sources for 3D Bioprinting of Tissue Constructs

“…This precise positioning of multiple cell types in an organized manner can be achieved with 3D bioprinting [4]. Plenty of natural materials, such as gelatin [5,6], alginate [7][8][9], collagen [10,11], and synthetic materials like polycaprolactone (PCL) [12][13][14][15][16] and polyethylene glycol (PEG) [17][18][19][20][21][22], come in handy while printing a structure. Although the abovementioned natural materials are biocompatible, disadvantages such as mechanical instability, limited degradability, restricted cell proliferation, and differentiation challenged researchers to investigate more on natural materials [23][24][25].…”