Silk-Reinforced Collagen Hydrogels with Raised Multiscale Stiffness for Mesenchymal Cells 3D Culture

Abstract

Type I collagen hydrogels are of high interest in tissue engineering. With the evolution of 3D bioprinting technologies, a high number of collagen-based scaffolds have been reported for the development of 3D cell cultures. A recent proposal was to mix collagen with silk fibroin derived from Bombyx mori silkworm. Nevertheless, due to the difficulties in the preparation and the characteristics of the protein, several problems such as phase separation and collagen denaturation appear during the procedure. Therefore, the common solution is to diminish the concentration of collagen although in that way the most biologically relevant component is reduced. In this study, we present a new, simple, and effective method to develop a collagen-silk hybrid hydrogel with high collagen concentration and with increased stiffness approaching that of natural tissues, which could be of high interest for the development of cardiac patches for myocardial regeneration and for preconditioning of mesenchymal stem cells (MSCs) to improve their therapeutic potential. Sericin in the silk was preserved by using a physical solubilizing procedure that results in a preserved fibrous structure of type I collagen, as shown by ultrastructural imaging. The macro-and micromechanical properties of the hybrid hydrogels measured by tensile stretch and atomic force microscopy, respectively, showed a more than twofold stiffening than the collagen-only hydrogels. Rheological measurements showed improved printability properties for the developed biomaterial. The suitability of the hydrogels for 3D cell culture was assessed by 3D bioprinting bone marrow-derived MSCs cultured within the scaffolds. The result was a biomaterial with improved printability characteristics that better resembled the mechanical properties of natural soft tissues while preserving biocompatibility owing to the high concentration of collagen.

Cartilage Tissue Engineering by Extrusion Bioprinting: Process Analysis, Risk Evaluation, and Mitigation Strategies

“…We focused our analysis on the extrusion-based bioprinting of an MSC-laden collagen 3D scaffold, a process that is currently under development in our lab for potential future applications in the regeneration of cartilage. We chose a standalone collagen bioink, despite the fact that combination with different materials has been generally considered to improve printability [31][32][33][34]. In parallel, we selected a population of solely human MSCs from bone marrow and not a mixture (i.e., MSCs and chondrocytes), which would better foster regenerative processes in the articular microenvironment [35].…”

Harnessing the ECM Microenvironment to Ameliorate Mesenchymal Stromal Cell-Based Therapy in Chronic Lung Diseases

“…The hydrogel properties both had matched biomechanical properties and contained ECM instructive factors from the native lung tissue (De Santis et al, 2020). Hydrogels based on collagen type I, one of the major structural components of tissues, has been extensively explored in combination with other materials such as silk, a highly elastic protein, to improve the mechanical properties to mimic the viscoelastic properties of tissues (Sanz-Fraile et al, 2020). As discussed above, GAGs multiple functions in cell signaling and in tissue homeostasis and have been explored as biomaterials.…”

Silk‐Based Biomaterials for Cardiac Tissue Engineering

“…One study found that silk‐reinforced collagen hydrogels had excellent mechanical properties with a maximum elastic modulus of up to 31 kPa and the stress of up to 1.8 kPa, matching with the native ventricular muscle (elastic modulus of 20 kPa, stress of 4 kPa). [ 52 ] Compared to the cells cultured within soft collagen hydrogels, BM‐derived mesenchymal stem cells (BMSCs) cultured within the silk‐reinforced hydrogels had more elongated morphology and were more evenly distributed. The topographical characteristic, another physical property of the scaffold, can affect the adhesion, alignment, morphology, and size of CMs.…”

“…And the stiffness was close to normal heart tissue, which was beneficial for the utilization of CTE. [ 52 ]…”