“Next generation gelatin-based bio-ink.”
X EASYGEL INX© is a gelatin-based shear thinning, cell-interactive ECM mimicking ink. X EASYGEL INX combines all the benefits of conventional gelatin/gel-MA based inks in combination with a highly improved printing process thanks to its shear thinning behavior, as schematically presented in Figure 1a. At high shear rates, it exhibits a low viscosity which is favourable for an easy injection from the printing nozzle. However, at low shear rates it reveals a high viscosity, which is required for shape retention after deposition. As a result, it can be printed in a straightforward and reproducible way at 37°C both in the presence or absence of cells (Figure 2). In this respect, it overcomes the narrow processing range limitations associated with printing a conventional gel-Ma based ink.
Figure 1: Typical flow curve for a shear thinning fluid: A decreasing viscosity profile as a function of shear rate indicates a shear-thinning behavior
Since X EASYGEL INX© is gelatin-based it is characterized by all the favourable gelatin properties including cell interactivity, biodegradability and the potential for cell encapsulation with high viability. Therefore, it acts as an ideal mimic of the natural extracellular environment, making it suitable for a whole range of tissues in combination with unprecedented processing ease. After printing, the material can be photo-crosslinked, resulting in a physiologically stable hydrogel.
Figure 2: Comparison of flow behavior of X EASYGEL INX© vs conventional gel-MA based inks at 37°C.
X EASYGEL INX is a transparent gel at room temperature. The physical characteristics of X Stable INX is listed in Table 1.
X EASYGEL INX reveals a shear-thinning behavior as shown in Figure 3 (a). This is favorable for extrusion-based 3D printers as the printing ink should easily be injected through the printing nozzle and the post-injection flow should be minimized in order to prevent structural deformation. These properties are very rarely seen in conventional gelatin-based inks, making there processing rather complicated.
To enable an optimal printing process ensuring shape fidelity, an ink should not only exhibit shear-dependent viscosity, but also its viscosity must exhibit a rapid decrease and rapid recovery upon an instant change in the shear conditions. After ejecting from the printing needle, an ink solution should regain quickly its viscosity upon deposition on the printing surface. The rate of viscosity recovery was studied via rotational step shear tests at shear rates of 0.1 s-1, 100s-1 and 0.1 s-1 in the sequential order. As seen in figure 3 (b), X EASYGEL INX exhibits a rapid mechanical recovery when the external forces are removed.
Figure 3: (a) Flow curve of X EASYGEL INX as a function of shear rate, (b) Storage and loss modulus of X EASYGEL INX tested in transient shear rate conditions and (c) storage and loss moduli of X EASYGEL INX recorded via a rheometer during UV irradiation
X EASYGEL INX is photo-curable, and therefore the structures can be illuminated with UV irradiation during or after printing process. After switching on the UV light source, the ink exhibits a fast crosslinking reaction as indicated by the steep increase of storage modulus (Figure 3 (c)). At the end of the irradiation process, the ink reached a storage modulus of approximately 3 kPa. This allows for sufficient mechanical integrity while being ideal for soft tissue culture.
- Easy Printing: shear thinning behavior enables easy deposition at 37°C
- Biodegradability: enables cellular remoddeling of the printed matrix
- Easy Handling: Delivered in a Ready-to-use cartridge
- UV-Curable: Efficient UV-based crosslinking
- Reproducibility: Production under strict quality control
Table 2: Typical benefits of X EASYGEL INX© over conventional bioinks
Figure 4: Examples of printed structures
Version June 2021