Pectin as Rheology Modifier of a Gelatin-Based Biomaterial Ink

Gelatin is a natural biopolymer extensively used for tissue engineering applications due to its similarities to the native extracellular matrix. However, the rheological properties of gelatin formulations are not ideal for extrusion-based bioprinting. In this work, we present an approach to improve gelatin bioprinting performances by using pectin as a rheology modifier of gelatin and (3-glycidyloxypropyl)trimethoxysilane (GPTMS) as a gelatin-pectin crosslinking agent. The preparation of gelatin-pectin formulations is initially optimized to obtain homogenous gelatin-pectin gels. Since the use of GPTMS requires a drying step to induce the completion of the crosslinking reaction, microporous gelatin-pectin-GPTMS sponges are produced through freeze-drying, and the intrinsic properties of gelatin-pectin-GPTMS networks (e.g., porosity, pore size, degree of swelling, compressive modulus, and cell adhesion) are investigated. Subsequently, rheological investigations together with bioprinting assessments demonstrate the key role of pectin in increasing the viscosity and the yield stress of low viscous gelatin solutions. Water stable, three-dimensional, and self-supporting gelatin-pectin-GPTMS scaffolds with interconnected micro- and macroporosity are successfully obtained by combining extrusion-based bioprinting and freeze-drying. The proposed biofabrication approach does not require any additional temperature controller to further modulate the rheological properties of gelatin solutions and it could furthermore be extended to improve the bioprintability of other biopolymers.