Tyramine-Functionalized Alginate-Collagen Hybrid Hydrogel Inks for 3D-Bioprinting

Abstract

Extrusion-based 3D-bioprinting using hydrogels has exhibited potential in precision medicine; however, researchers are beset with several challenges. A major challenge of this technique is the production of constructs with sufficient height and fidelity to support cellular behavior in vivo. In this study, we present the 3D-bioprinting of cylindrical constructs with tunable gelation kinetics by controlling the covalent crosslinking density and gelation time of a tyramine-functionalized alginate hydrogel (ALG-TYR) via enzymatic reaction by horseradish peroxidase (HRP) and hydrogen peroxide (H2O2). The extruded filament was crosslinked for a second time on a support bath containing H2O2 to increase fidelity after printing. The resulting tubular construct, with a height of 6 mm and a wall thickness of 2 mm, retained its mechanical properties and had a maximum 2-fold swelling after 2 d. Furthermore, collagen (COL) was introduced into the ALG-TYR hydrogel network to increase the mechanical modulus and cell cytocompatibility, as the encapsulated fibroblast cells exhibited a higher cell viability in the ALG-TYR/COL construct (92.13 ± 0.70%) than in ALG-TYR alone (68.18 ± 3.73%). In summary, a vascular ECM-mimicking scaffold was 3D-bioprinted with the ALG-TYR/COL hybrid hydrogel, and this scaffold can support tissue growth for clinical translation in regenerative and personalized medicine.

Alginate–Gelatin Self-Healing Hydrogel Produced via Static–Dynamic Crosslinking

“…However, slight differences in swelling trends are observable at pH 7.4 and pH 8.5 due to the contribution of boronate–diol interaction linkages that stabilize the hydrogels, showing comparable behavior in both static and static–dynamic conditions. Furthermore, the weight did not change significantly as reported in the literature for similar hydrogels [ 26 , 37 , 38 ].…”

“…Alginate contains 1,2-diol sequences suitable for a dynamic crosslinking with boronic acid residues, once inserted in the polymeric chains. For static crosslinking, we decided to engage the few tyrosine residues (<1%) of gelatin, exploiting the horseradish peroxidase (HRP)-catalyzed [ 26 ] enzymatic coupling with tyramine residues inserted in the alginate backbone ( Scheme 1 ). In detail, tyramine and 3-aminophenylboronic acid (3APBA) randomly attach to the carboxylic acid group of mannuronic or guluronic residues of alginate, allowing the static–dynamic linkages between alginate and gelatin ( Scheme 1 a).…”

“…Alginate was the only hydrogel component that needed functionalization. It was double functionalized in one step with tyramine [ 26 ] and 3-aminophenylboronic acid (3APBA) [ 27 ], requiring only one final purification step. To this purpose, the carboxylic acid groups of alginate were activated with N-(3-dimethylaminopropyl)-N’-ethylcarbodiimide hydrochloride (EDC) and N-hydroxysuccinimide (NHS) to react with the amine group present in both 3APBA and tyramine.…”

“…It is noteworthy that not all the carboxylic acid groups of alginate must be converted into amides, being fundamental to guarantee the physical properties and solubility of the polymer. Experimentally, the addition of tyramine was dosed to reach a degree of functionalization of about 10% [ 26 , 28 ], and the subsequent addition of 3APBA reached a degree of functionalization of about 6%.…”

Design of a New 3D Gelatin—Alginate Scaffold Loaded with Cannabis sativa Oil

“…Bioinks are a critical component during the artificial tissue fabrication, and their selection depends on the specific application [ 10 , 11 ]. Although they can be made of synthetic polymers [ 12 ], most bioinks are prepared with naturally-derived biomaterials [ 13 , 14 , 15 ] as they provide a suitable environment for cell adhesion, proliferation, differentiation and the formation of a new tissue. For example, alginate and gelatin are some of the most frequently used bioinks for 3D printing of tissue models due to their high biocompatibility, low cost, good biodegradability, abundance and availability [ 16 , 17 , 18 ].…”