Development and characterisation of a new bioink for additive tissue manufacturing

Abstract

Additive manufacturing forms a potential route towards economically viable production of cellular constructs for tissue engineering. Hydrogels are a suitable class of materials for cell delivery and 3D culture, but are generally unsuitable as construction materials. Gelatine-methacrylamide is an example of such a hydrogel system widely used in the field of tissue engineering, e.g. for cartilage and cardiovascular applications. Here we show that by the addition of gellan gum to gelatinemethacrylamide and tailoring salt concentrations, rheological properties such as pseudo-plasticity and yield stress can be optimised towards gel dispensing for additive manufacturing processes. In the hydrogel formulation, salt is partly substituted by mannose to obtain isotonicity and prevent a reduction in cell viability. With this, the potential of this new bioink for additive tissue manufacturing purposes is demonstrated.

Tailoring Hydrogel Viscoelasticity with Physical and Chemical Crosslinking

“…MC was included to dilute the mix during processing, with MC reported to diffuse out after crosslinking and subsequent immersion in medium [33]. The use of MC did not achieve this outcome, in contrast to the very effective N+M, with low ion concentrations maintaining GG in a loosely crosslinked state that remained pipettable due to the pseudoplasticity of the material [23].…”

“…Hydrogel groups (detailed in Table 1; mixed in phosphate buffered saline (PBS; Invitrogen, Carlsbad, CA, USA) or an isotonic blend of NaCl and D-mannose (24 and 252 mM, respectively [23]; henceforth N+M) were analyzed using a Rotational Rheometer RHEOTEST RN 4.1 (RHEOTEST Medingen GmbH, Ottendorf-Okrilla, Germany) with a precise thermal control unit. Testing consisted of multiple measures on each sample for analysis of gelation temperature (T C) and viscosity (ηq across the temperature sweep.…”

“…GG forms aqueous solutions of low viscosities at high temperatures (>70˝C is required to fully hydrate the structure [19]), and forms strong, hard and brittle gels upon cooling through a coil-helix transition, with helical aggregation and hydrogel stability dependent on the presence, concentration and valence of cations in the solution [20][21][22]. GG is also a highly suitable material for three dimensional (3D) printing due to its relatively prominent pseudoplasticity and ionic tailorability [23]. Modification of GG with methacrylic anhydride yields the photocrosslinkable gellan gum methacrylate (GGMA).…”

Ex vivo model unravelling cell distribution effect in hydrogels for cartilage repair_suppl

“…A promising hydrogel for the biofabrication of such implants is gelatin methacryloyl (gelMA) with gellan gum, which can be UV cross-linked, retains its shape during crosslinking and culture, and was demonstrated to support chondrogenesis of embedded chondrocytes (Mouser et al, 2016b). Additionally, gelMA/gellan is compatible with 3D printing techniques, which facilitate accurate positioning of the (cell-laden) biomaterial (Mouser et al, 2016b;Melchels et al, 2014).…”

“…To fill the defects, gelMA was synthesized from porcine gelatin and 10% gelMA + 0.5% gellan gum solution was freshly prepared, both as previously described (Mouser et al, 2016b;Melchels et al, 2014). GelMA/gellan (10 µl per defect) was dispensed into the defect without chondrocytes (conditions A, E) or with embedded chondrocytes (conditions B, C, D; Fig.…”