Tuning Alginate-Gelatin Bioink Properties by Varying Solvent and Their Impact on Stem Cell Behavior

Abstract

Bioink optimization is considered as one of main challenges in cell-laden 3D bioprinting. Alginate-Gelatin (Alg-Gel) hydrogel have been extensively used as bioink. However, its properties could be influenced by various parameters, and little is known about the evidence featuring the impact of solvent. Here we investigated four Alg-Gel bioink by varying solvent ionic strength (named B-1, B-2, B-3 and B-4). Mechanical properties and printability of bioink samples and their impacts on behaviors of encapsulated epidermal stem cells (ESCs) were tested. Bioink with increased ionic strength of solvent showed decreased stiffness and viscosity, and increased swelling and degradation by printability and mechanical property tests. Due to the increased swelling and degradation was associated with shape-maintenance of post-printing constructs, B-3 and B-4 were hardly observable after 14 days. Cellular behaviors were assessed through viability, proliferation, aggregation and differentiation tests. B-2 with optimal properties resulted in higher viability and proliferation of ESCs, and further facilitated cellular aggregation and lineage differentiation. We demonstrated that the solvent can be tuned by ionic strength to control the properties of Alg-Gel bioink and post-printing constructs, which represented a promising avenue for promotion of therapeutic stem cell behaviors in 3D bioprinting.

Gelatin‐polysaccharide composite scaffolds for 3D cell culture and tissue engineering: Towards natural therapeutics

“…Human corneal epithelial cells (HCECs) were bioprinted in collagen–gelatin–alginate composite hydrogels, and the scaffolds were exposed to sodium citrate, yielding controlled degradation, which in turn resulted in high cell viability (>90%), proliferation, and cytokeratin 3 (CK3) expression . Alginate–gelatin bioinks can also be engineered by tailoring the ionic strength . The storage and loss moduli of bioprinted constructs decreased using 1× (165 mM) and 2× (328 mM) phosphate‐buffered saline (PBS), resulting in mechanically weak, fast‐swelling, and unstable scaffolds, incapable of hosting epidermal stem cells.…”

“…Similarly, without PBS, the cells remained isolated from each other and were not able to proliferate. The optimum concentration of PBS (82 mM, 0.5×) resulted in improved cell function in terms of viability, proliferation, glandular morphology, and differentiation to epithelium and sweat glands, while providing a decent printability of epidermal stem cell‐laden constructs, setting the stage for the regeneration of sweat glands …”

“…215 Alginate-gelatin bioinks can also be engineered by tailoring the ionic strength. 216 The storage and loss moduli of bioprinted constructs decreased using 1× (165 mM) and 2× (328 mM) phosphate-buffered saline (PBS), resulting in mechanically weak, fastswelling, and unstable scaffolds, incapable of hosting epidermal stem cells. Similarly, without PBS, the cells remained isolated from each other and were not able to proliferate.…”

“…The optimum concentration of PBS (82 mM, 0.5×) resulted in improved cell function in terms of viability, proliferation, glandular morphology, and differentiation to epithelium and sweat glands, while providing a decent printability of epidermal stem cell-laden constructs, setting the stage for the regeneration of sweat glands. 216 Developing clinically relevant models of tumors has been a prime impetus for emerging 3D culture systems. 217,218 A bioink consisting of gelatin, alginate, and fibrinogen hydrogels combined with HeLa cells was used to 3D print cervical tumor models and investigate disease pathogenesis and drug resistance.…”

Beyond 2D: 3D bioprinting for skin regeneration

“…On the other hand, properties of bioink can be influenced by various parameters, which significantly impact cell behaviour and tissue formation within printed constructs. In our previous work, we modulated bioink properties by varying the solvent ionic strength of Alg‐Gel hydrogel and indicated that this modulation had a profound effect on stem cell behaviours in 3D bioprinting …”