Role of temperature on bio-printability of gelatin methacryloyl bioink in two-step cross-linking strategy for tissue engineering applications

Abstract

Additive manufacturing has shown promising results in reconstructing three-dimensional (3D) living tissues for various applications, including tissue engineering, regenerative medicine, drug discovery, and high-throughput drug screening. In extrusion-based bioprinters, stable formation of filaments and high-fidelity deposition of bioinks are the primary challenges in fabrication of physiologically relevant tissue constructs. Among various bioinks, gelatin methacryloyl (GelMA) is known as a photocurable and physicochemically tunable hydrogel with a demonstrated biocompatibility and tunable biodegradation properties. The two-step crosslinking of GelMA (reversible thermal gelation and permanent photo-crosslinking) has attracted researchers to make complex tissue constructs. Despite promising results in filament formation and printability of this hydrogel, the effect of temperature on physicochemical properties, cytocompatibility, and biodegradation of the hydrogel are to be investigated. This work studies the effect of thermoreversible, physical crosslinking on printability of GelMA. The results of 3D printing of GelMA at different temperatures followed by irreversible chemical photo-crosslinking show that the decrease in temperature improves the filament formation and shape fidelity of the deposited hydrogel, particularly at the temperatures around 15 °C. Time dependant mechanical testing of the printed samples revealed that decreasing the extruding temperature increases the elastic properties of the extruded filaments. Furthermore, our novel approach in minimizing the slippage effect during rheological study enabled to measure changes in linear and non-linear viscoelastic properties of the printed samples at different temperatures. A considerable increase in storage modulus of the extruded samples printed at lower temperatures confirms their higher solid behavior. Scanning electron microscopy revealed a remarkable decrease in porosity of the extruded hydrogels by decreasing the temperature. Chemical analysis by Fourier-transform infrared spectroscopy and circular dichroism showed a direct relationship between the coil-helix transition in hydrogel macromers and its physical alterations. Finally, biodegradation and cytocompatibility of the extruded hydrogels decreased at lower extruding temperatures.

Long-Term Sustained Drug Delivery via 3D Printed Masks for the Development of a Heparin-Loaded Interlayer in Vascular Tissue Engineering Applications

“…The reduction in UV light exposure from mask 1 and mask 2 correspond to a decrease in elastic modulus, which affirms the previously established correlation between UV exposure and modulus. , Elastic modulus is proportional to the density of crosslinks; , therefore, the use of masks during UV crosslinking results in a decrease in crosslinking density as well. The masks developed in this work provide a means to spatially control crosslinking across the graft with a single-step process, as opposed to more traditional methods of controlling crosslinking. ,, Furthermore, the inverse relationship between elastic modulus and pore size has been well characterized in the literature, − which suggests that the masks increase pore size and may contribute to differences in drug release, as well.…”

Structured Ultra‐Flyweight Aerogels by Interfacial Complexation: Self‐Assembly Enabling Multiscale Designs

“…It is worth mentioning that the tubules' formation and their mechanical integrity stem solely from the rapid GO/POSS interfacial skin formation, rather than the bulk rheology of the suspensions, which is the primary origin of the typical filament formation in direct ink writing/printing of hydrogels. [49][50][51][52] Figure 1d and Video S3 (Supporting Information) clearly show the flowability of the GO suspensions at four different concentrations. Following a recent work by Russell and co-workers [] and for simplicity, we named these structured liquids as "sculpted emulsions."…”

Magnetic resonance imaging as a tool for quality control in extrusion‐based bioprinting

“…The hydrogel network of the alginate ink (see Figure 3A and B The viscosity of the GelMA ink is sensitive to changes in temperature as well as the storage time in the cartridge. [33][34][35] With the optimal extrusion properties being in the interphase between liquid and gelled state of the ink, the extruded mass flow is sensitive to changes of the ambient conditions. For the application of the scaffolds, differing strand diameters have a huge impact on the scaffold geometry as well as the diffusive distances in the strands.…”