GelMA-collagen blends enable drop-on-demand 3D printablility and promote angiogenesis

Abstract

Effective vascularization is crucial for three-dimensional (3D) printed hydrogel-cell constructs to efficiently supply cells with oxygen and nutrients. Till date, several hydrogel blends have been developed that allow the in vitro formation of a capillary-like network within the gels but comparatively less effort has been made to improve the suitability of the materials for a 3D bioprinting process. Therefore, we hypothesize that tailored hydrogel blends of photo-crosslinkable gelatin and type I collagen exhibit favorable 3D drop-on-demand printing characteristics in terms of rheological and mechanical properties and that further capillary-like network formation can be induced by co-culturing human umbilical vein endothelial cells and human mesenchymal stem cells within the proposed blends. Gelatin was methacrylated (GelMA) at a high degree of functionalization, mixed with cells, type I collagen, and the photoinitiator Irgacure 2959 and then subsequently crosslinked with UV light. After 14 d of incubation, cells were immunofluorescently labeled (CD31) and displayed using two-photon laser scanning microscopy. Hydrogels were rheologically characterized and dispensable droplet volumes were measured using a custom built 3D drop-on-demand bioprinter. The cell viability remained high in controllable crosslinking conditions both in 2D and 3D. In general, higher UV light exposure and increased Irgacure concentration were associated with lower cell viabilities. Distinctive capillary-like structures were formed in 3D printable GelMA-collagen hydrogels. The characteristic crosslinking time for GelMA in the range of minutes was not altered when GelMA was blended with type I collagen. Moreover, the addition of collagen led to enhanced cell spreading, a shear thinning behavior of the hydrogel solution and increased the storage modulus of the crosslinked gel. We therefore conclude that GelMA-collagen hydrogels exhibit favorable biological as well as rheological properties which are suitable for the manufacturing of pre-vascularized tissue replacement by 3D bioprinting.

Combination of vascularization and cilia formation for three‐dimensional airway tissue engineering

“…Even though general feasibility was shown, capillary‐like network formation was lower compared to fibrin gels. Since viscosity and hydrogel density are higher in AGR0.5COLL0.5 blends, this might have led to impaired cell activity and vascularization (Kreimendahl et al, ; Stratesteffen et al, ).…”

“…blends, this might have led to impaired cell activity and vascularization Stratesteffen et al, 2017).…”

Photochemically crosslinked cell‐laden methacrylated collagen hydrogels with high cell viability and functionality

“…The photopolymerization process is enabled via a photoinitiator which is a light-sensitive reagent that when exposed to a specific light wavelength will dissociate into free radicals that in turn induce the photopolymerization of the hydrogel. 3 While many different types of photoinitiators have been investigated, [4][5][6][7][8] Irgacure 2959 (I2959) is the most widely used [9][10][11] due to its high free radical generation efficiency and relatively higher water solubility. 3 However, there are concerns related to the cytotoxicity of the free radicals generated using I2959 for fast dividing cell lines.…”

A Biomimetic 3D‐Self‐Forming Approach for Microvascular Scaffolds

“…Being the track in which nutrients and metabolites are continuously transported and circulated, the complex vascular networks are essential for the survival and repair of tissues. [ 4,5 ] Problems, such as flap necrosis, [ 6,7 ] coronary heart disease, [ 8,9 ] and bone necrosis, [ 10,11 ] often arise once the circulation is interrupted. To address these problems, many studies have been devoted to promote the progress of vascularization in which various angiogenic cells migrated to form primary microvessels, which further develop into arterioles and venules.…”

“…GelMA was chosen as the matrix material due to its good biocompatibility, mesoporous structure, and inexpensiveness. [ 4,6 ] Rectangular‐shaped GelMA hydrogel flake (approximately 20 μL GelMA) with the dimensions of 30 mm × 2 mm × 0.20 mm was fabricated by 3D printer (CELLINK AB, Sweden) or glass mould‐followed by immediate UV exposure for solidification. The flake was then dried by air‐blowing at room temperature (RT) or baking at 60 °C.…”