Development of a GelMA-based bioink enhanced with minimally-processed tissue for the fabrication of skeletal muscle

Abstract

Bioprinting, an emerging technology that uses living cells and biomaterials for fabricating engineered tissues with complex three-dimensional (3D) architecture, has become popular as an alternative to conventional 3D-culture techniques. In typical extrusion bioprinting, a bioink (i.e., generally a suspension of cells in a hydrogel) is extruded through a printing head to build an artificial 3D tissue in a layer-by-layer-fashion. Bioinks are key components of a bioprinting process. Bioinks have to meet appropriate biological and rheological characteristics to be printable and to provide a proper microenvironment to cells. Here, we present a simple strategy to develop cost-effective bioinks based on gelatin methacryloyl (GelMA) enhanced with fetal minimally processed muscle tissue (MPT). This strategy is intended to supplement bioinks with growth factors, glycosaminoglycans and proteins from fetal tissue, due to its biochemical composition rich in growth factors and peptides. As a first demonstrative model, we supplemented GelMA hydrogels with 0.5, 1, 2% dried and powdered MPT derived from a goat or calf fetus. The biochemical characterization of MPT showed that our minimally processed technique preserves more than 65% of GAG content compared to traditional methods (i.e. decellularization). The rheological profile of our hydrogels was analyzed to determine a suitable working-window of printing parameters, all inks have shear thinning behavior. Cell-culture experiments showed that the incorporation of MPT in the hydrogels influences the metabolic activity of the myoblast cells (C2C12) and confers structural stability to the hydrogels for cultures of up to 28 days in comparison to pristine GelMA hydrogels. The cell orientation of the GelMA-MPT bioprinted constructs (measured with image analysis) was up to 60% resembling the tissue coherence and architecture of native tissue. Our results demonstrate that our materials can be used as cost-effective bioinks for the bioprinting of skeletal muscle models.