Printability and bio-functionality of a shear thinning methacrylated xanthan–gelatin composite bioink

Abstract

3D bioprinting is a recent technique that can create complex cell seeded scaffolds and therefore holds great promise to revolutionize the biomedical sector by combining materials and structures that more closely mimic the 3D cell environment in tissues. The most commonly used biomaterials for printing are hydrogels, however, many of the hydrogels used still present issues of printability, stability, or poor cell-material interactions. We propose that bioinks with intrinsic self-assembling and shear thinning properties, such as xanthan gum, can be methacrylated (XGMA) and combined with a bio-functional material such as gelatin methacryloyl (GelMa) to create a stable, cell-interactive bioink with improved properties for 3D bioprinting. These biomaterials have reduced viscosity under high shear and recover their viscosity rapidly after the shear is removed, retaining their shape, which translates to easier extrusion whilst maintaining accurate fidelity after printing. This was confirmed in printing studies, with measured normalized strand widths of 1.2 obtained for high gel concentrations (5+5 % XGMA-GelMA). Furthermore, the introduction of a secondary photo-cross-linking method allowed tuning of the mechanical properties of the hydrogel with stiffness between 15 and 30 kPa, as well as improving the stability of the hydrogel with retention of 75 % of its mass after 90 d. The hydrogel was shown to be biocompatible and bio-active with 97 % cell viability, and cell spreading after 7 d of culture for low gel concentrations (3+3 % XGMA-GelMA). Shear stresses were relatively low while printing (1 kPa) as a result of the shear thinning property of the material, which supported cell viability during extrusion. Finally, printed hydrogels retained high cell viability for lower gel concentrations, and showed improved cell viability for more concentrated hydrogels when compared to cells cultured in bulk hydrogels, presumably due to improved nutrient/oxygen diffusion and cell migration. In conclusion, stability and formulation of a XGMA-GelMA shear thinning composite hydrogel has been optimized to create a bio-functional bioink, with improved printability, and in vitro culture stability via secondary photo-induced cross-linking, making this composite a promising bioink for 3D bioprinting.

Preparation and characterization of biomimetic gradient multi-layer cell-laden scaffolds for osteochondral integrated repair

“…Shear-thinning hydrogel solutions can improve injectability of cell-loaded hydrogel solutions 40 and reduce damage to cells when the hydrogel solution passes through a pinhole or pipette tip. 41 However, more damage could be induced by fluid shear stress due to the addition of nHA.…”

Proteolytic remodeling of 3D bioprinted tumor microenvironments

“…To improve printability, we instead added XG to the HA-BCN solution prior addition of cross-linkers (figure 1(d)). XG is well tolerated by cells and widely used in bioinks to modulate their viscosity [40][41][42][43]. The effect of increasing XG concentration from 0 to 1.5% (w/v) were investigated.…”

Bioink Formulation and Machine Learning-Empowered Bioprinting Optimization

“…Xanthan gum has also been used to minimize cell settling in bioinks with a lower viscosity ( Dubbin et al, 2017 ) and to improve shape fidelity ( Garcia-Cruz et al, 2021 ). Bioprinting applications do not typically include xanthan in a gel form.…”