Recombinant spider silk proteins (spidroins) have multiple potential applications in development of novel biomaterials, but their multimodal and aggregation-prone nature have complicated production and straightforward applications. Here, we report that recombinant miniature spidroins, and importantly also the N-terminal domain (NT) on its own, rapidly form self-supporting and transparent hydrogels at 37 °C. The gelation is caused by NT α-helix to β-sheet conversion and formation of amyloid-like fibrils, and fusion proteins composed of NT and green fluorescent protein or purine nucleoside phosphorylase form hydrogels with intact functions of the fusion moieties. Our findings demonstrate that recombinant NT and fusion proteins give high expression yields and bestow attractive properties to hydrogels, e.g., transparency, cross-linker free gelation and straightforward immobilization of active proteins at high density.

Food 3D printing allows for the production of personalised foods in terms of shape and nutrition. In this study, we examined whether protein-, starch- and fibre-rich fractions extracted from faba beans can be combined to produce fibre- and protein-rich printable food inks for extrusion-based 3D printing. Small amplitude oscillatory shear measurements were used to characterise the inks while compression tests and scanning electron microscopy were used to characterise the freeze-dried samples. We found that rheological parameters such as storage modulus, loss tangent and yield stress were related to ink printability and shape stability. Investigations on the effect of ink composition, infill pattern (honeycomb/grid) and direction of compression on textural and microstructural properties of freeze-dried 3D-printed objects revealed no clear effect of infill pattern, but a strong effect of direction of compression. Microstructure heterogeneity seemed to be correlated with the textural properties of the printed objects.