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Protein-based microfibers have potential applications in bioengineering and food but preserving and utilizing the unique nanomechanical properties of their protein building blocks at the micrometer scale remains a challenge. This study investigates the bottom-up fabrication of core-shell fibers by coaxial microfluidic spinning of pectin and β-lactoglobulin in different conformational states (monomeric, amyloid fibrils, shortened amyloid fibrils in their isotropic/nematic phases), gelled in CaCl2 solution. Fiber diameters ranged between 478 and 855 μm (wet state) and 107–135 μm (dry state). They showed clear core-shell cross-sections, except pectin-β-lactoglobulin monomer fibers where the compact protein is presumably understood to diffuse through the pectin matrix. The molecular orientation of the fiber building blocks was expressed as order parameters representing the alignment of pectin chains and amyloid fibrils parallel to the fiber axis calculated from synchrotron wide-angle X-ray scattering (WAXS) with a spatial resolution of 20 μm. Introduction of amyloid fibrils as the protein core increased the Young's modulus from 3.3 to 6.4 GPa and tensile strength from 117 to 182 MPa compared to pure pectin fibers. Increasing the protein core flow rate from 1 to 2 mL/h, however, caused helical bending of the core jet, a decrease in order, and ultimately worsened mechanical performance. Overall, full length amyloid fibrils proved to be more beneficial to the mechanical properties than shortened amyloid fibrils. By providing insight into the relationship between protein conformation, spinning flow rate, and resulting mechanical properties of core-shell microfibers, these results may contribute to the field of novel fibrous protein-based materials., Food Hydrocolloids, 143, ISSN:0268-005X, ISSN:1873-7137

Amyloid fibrils from plant-based food protein sources bear a large unexploited potential for applications in food and other biomaterials due to their techno-functional features. However, their low solubility and highly complex, inhomogeneous protein composition often hamper fibrillization. The objective of this study was to evaluate the feasibility of amyloid fibril production from hemp seed protein, known as a sustainable and low-allergenic protein source. Hemp protein concentrate (HPC), primarily constituted of the 11 S globulin edestin, with 89.0% protein solubility (0.25% w/w HPC, pH 2) was extracted using gentle micellization. Fibrillization of HPC (2% w/w, pH 2, 90 °C, 300 rpm) was monitored over 5 h by ThT fluorescence, exhibiting a steep increase in fluorescence signal after a lag phase of 180 min. SDS-PAGE analysis indicated progressive polypeptide hydrolysis upon heating and the formation of large proteinaceous aggregates after 160 min. Conformational changes towards increased β-sheet content were demonstrated by CD and FTIR. The morphology of the formed fibrillar aggregates was characterized by TEM and AFM. While essentially linear, branching effects of the fibrils became visible and kept increasing with incubation time. After a relatively short incubation time of 4 h, fibrils had an average height of 7.8 nm, a contour length of 1.8 μm, and a persistence length of ∼2.7 μm. These results suggest, that under the chosen conditions for protein extraction and incubation, HPC forms relatively flexible amyloid fibrils with a high aspect ratio and tendency to form branches. By revealing the potential of hemp seed proteins for amyloid fibril formation, these results contribute to expand the understanding of plant protein fibrillization., Food Hydrocolloids, 137, ISSN:0268-005X, ISSN:1873-7137

Artificial functional materials based on amyloid fibrils are proven to be a promising strategy toward functional materials. However, scaling-up applications present sustainability concerns, as animal proteins are the main sources for fabricating amyloid fibrils. Plant-protein-based amyloid fibrils, a more sustainable alternative to animal proteins, are attracting increasing interests as building blocks in functional materials. Herein, 11 different sources from a wide range of plants are evaluated, and a comprehensive analysis of seven species of plant proteins, including kidney bean, black bean, cowpea, mung bean, chickpea, lentil, and pumpkin seed, with an excellent ability to form fibrils, is presented. A universal strategy for a diversity of plant protein extraction and fibrillization is applied. Flexible fibrils with a persistence length of approximate to 100 nm and rigid fibrils of several micrometers are discovered in 7S/8S and 11S subunits dominated protein, respectively. Structural evolution toward the beta-sheet content on these proteinaceous assemblies is characterized by thioflavin T (ThT) intensity, circular dichroism (CD) spectra, attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectra, and typical wide angle X-ray scattering (WAXS) spectra. Finally, their multifunctional applications are further explored and proven that these sustainable protein amyloids demonstrate excellent performance in renewable and degradable bioplastics, and in water purification membranes for heavy metal removal., Advanced Sustainable Systems, 7 (4)

Nanofiber mats can be produced by electrospinning from diverse polymers and polymer blends as well as with embedded ceramics, metals, etc. The large surface-to-volume ratio makes such nanofiber mats a well-suited substrate for tissue engineering and other cell growth experiments. Cell growth, however, is not only influenced by the substrate morphology, but also by the sterilization process applied before the experiment as well as by the chemical composition of the fibers. A former study showed that cell growth and adhesion are supported by polyacrylonitrile/gelatin nanofiber mats, while both factors are strongly reduced on pure polyacrylonitrile (PAN) nanofibers. Here we report on the influence of different PAN blends on cell growth and adhesion. Our study shows that adding ZnO to the PAN spinning solution impedes cell growth, while addition of maltodextrin/pea protein or casein/gelatin supports cell growth and adhesion.