Correlating network structure with functional properties of capillary alginate gels for muscle fiber formation

Capillary alginate gels have the potential to be used as scaffold for the growth of muscle cells for cultured meat owing to the formation of aligned skeletal muscle cells along the length of self-assembled micro-capillaries within the calcium alginate gel. The functional properties (mechanical and permeability) of the gels were determined and correlated to the nano-lengthscale of the gel network using small-angle X-ray scattering. Calcium ions were let to diffuse into the alginate solution in order to obtain spontaneously formed capillaries. We show that the resulting calcium alginate network is isotropic in the plane perpendicular to the inflow of cross linking ions while anisotropic in the parallel plane. The structural anisotropicity is reflected in the mechanical properties (measured via uniaxial stress relaxation) of the gel, where a larger force is required to compress the gel in the isotropic plane than in the anisotropic plane. The findings suggest that the network is layered, or composed of “sheets” with denser regions of alginate, sheets that are weakly attached to each other, similar to the structure of bacterial cellulose. Such structure would further explain the increased permeability of labeled dextran (as determined using fluorescence recovery after photo-bleaching) that we observed in the alginate gels used in this study, as compared to internally set calcium alginate gel