Hydroxyapatite-modified gelatin bioinks for bone bioprinting

Abstract

In bioprinting approaches, the choice of bioink plays an important role since it must be processable with the selected printing method, but also cytocompatible and biofunctional. Therefore, a crosslinkable gelatin-based ink was modified with hydroxyapatite (HAp) particles, representing the composite buildup of natural bone. The inks’ viscosity was significantly increased by the addition of HAp, making the material processable with extrusion-based methods. The storage moduli of the formed hydrogels rose significantly, depicting improved mechanical properties. A cytocompatibility assay revealed suitable ranges for photoinitiator and HAp concentrations. As a proof of concept, the modified ink was printed together with cells, yielding stable three-dimensional constructs containing a homogeneously distributed mineralization and viable cells

Improved vasculogenesis and bone matrix formation through coculture of endothelial cells and stem cells in tissue‐specific methacryloyl gelatin‐based hydrogels

“…To create the precursor solution for bone hydrogels, 13% polymer (containing 6% [w/w] GM5, 6% [w/w] GM2, and 1% [w/w] HAM) and the photoinitiator lithium phenyl‐2,4,6‐trimethylbenzoylphosphinate (LAP; synthesized according to Fairbanks, Schwartz, Bowman, and Anseth, ) in a concentration proven to be cytocompatible before (0.135% [w/w] of biopolymer mass; Wenz et al, ) were dissolved in phosphate buffered saline containing divalent cations (PBS + ; Sigma, Steinheim, Germany) and filtered sterile (cellulose acetate membrane; pore size = 0.2 µm; Sartorius Stedim, Göttingen, Germany). HAp particles (5% [w/w] of total ink mass; Sigma‐Aldrich, Taufkirchen, Germany) with a mean diameter (single particle) of 200 nm were added, and the suspension was sonicated to break down aggregates.…”

Beyond the Modification Degree: Impact of Raw Material on Physicochemical Properties of Gelatin Type A and Type B Methacryloyls

“…Additional modification of gelatin with inert acetyl functions (GMA) has been introduced by our group to tune viscosity and gelation of aqueous GM solutions independently from its cross‐linking potential . Formulations of GM(A) with adjusted properties are also increasingly used for sophisticated fabrication techniques such as inkjet‐printing, robotic dispensing, fused deposition modeling, or two‐photon polymerization . Differences in mechanical properties of resulting GM hydrogels and tissue‐specific additives are utilized to emulate most diverse tissues such as bone, cartilage, adipose tissue, cardiac tissue, and as matrix for formation of capillary structures .…”

Photoinduced Cleavage and Hydrolysis of o‐Nitrobenzyl Linker and Covalent Linker Immobilization in Gelatin Methacryloyl Hydrogels

“…Control samples with nonirradiated gels were performed as well. [76] The irradiation with the UV-lamp used in this study has been proofed to be cytocompatible in other studies from our group for human adipose derived stem cells at irradiation with 1.08 J cm −2 [77] and primary human mature adipocytes at irradiation with 1.62 J cm −2 , [78] higher doses were not tested in both cases, and porcine chondrocytes at irradiation energies up to 4.47 J cm −2 . The data show that the photoinduced release of the StrepHRP was possible similarly to results published for BSA release out of PEG-based hydrogels with a similar photocleavable linker.…”

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of many beneficial properties of the ECM and the possibility to adjust the crosslinking density of GM hydrogels with the degree of methacryloylation (DM), GMbased hydrogels were used to prepare scaffolds for a broad variety of tissues, e.g., adipose tissue, [14] cartilage, [15] or bone, [16,17] and were utilized for controlled release applications as well. [18][19][20] There are three common concepts to immobilize, e.g., proteins in hydrogels for controlled release applications: Covalent immobilization, immobilization by physical entrapment, or noncovalent immobilization via affinity interactions.

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