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Amyloid fibrils from inexpensive food proteins and nanocellulose are renewable and biodegradable materials with broad ranging applications, such as water purification, bioplastics and biomaterials. To improve the mechanical properties of hybrid amyloid-nanocellulose materials, their colloidal interactions need to be understood and tuned. A combination of turbidity and zeta potential measurements, rheology and atomic force microscopy point to the importance of electrostatic interactions. These interactions lead to entropy-driven polyelectrolyte complexation for positively charged hen egg white lysozyme (HEWL) amyloids with negatively charged nanocellulose. The complexation increased the elasticity of the amyloid network by cross-linking individual fibrils. Scaling laws suggest different contributions to elasticity depending on nanocellulose morphology: cellulose nanocrystals induce amyloid bundling and network formation, while cellulose nanofibrils contribute to a second network. The contribution of the amyloids to the elasticity of the entire network structure is independent of nanocellulose morphology and agrees with theoretical scaling laws. Finally, strong and almost transparent hybrid amyloid-nanocellulose gels were prepared in a slow self-assembly started from repulsive co-dispersions above the isoelectric point of the amyloids, followed by dialysis to decrease the pH and induce amyloid-nanocellulose attraction and cross-linking. In summary, the gained knowledge on colloidal interactions provides an important basis for the design of functional biohybrid materials based on these two biopolymers., Journal of Colloid and Interface Science, 641, ISSN:0021-9797, ISSN:1095-7103

Multiple neurodegenerative diseases are caused by the aggregation of the human -Synuclein (-Syn) protein. -Syn possesses high structural plasticity and the capability of interacting with membranes. Both features are not only essential for its physiological function but also play a role in the aggregation process. Recently it has been proposed that -Syn is able to form lipid-protein particles reminiscent of high-density lipoproteins. Here, we present a method to obtain a stable and homogeneous population of nanometer-sized particles composed of -Syn and anionic phospholipids. These particles are called -Syn lipoprotein (nano)particles to indicate their relationship to high-density lipoproteins formed by human apolipoproteins in vivo and of in vitro self-assembling phospholipid bilayer nanodiscs. Structural investigations of the -Syn lipoprotein particles by circular dichroism (CD) and magic angle solid-state nuclear magnetic resonance (MAS SS-NMR) spectroscopy establish that -Syn adopts a helical secondary structure within these particles. Based on cryo-electron microscopy (cryo-EM) and dynamic light scattering (DLS) -Syn lipoprotein particles have a defined size with a diameter of approximate to 23 nm. Chemical cross-linking in combination with solution-state NMR and multiangle static light scattering (MALS) of -Syn particles reveal a high-order protein-lipid entity composed of approximate to 8-10 -Syn molecules. The close resemblance in size between cross-linked in vitro-derived -Syn lipoprotein particles and a cross-linked species of endogenous -Syn from SH-SY5Y human neuroblastoma cells indicates a potential functional relevance of -Syn lipoprotein nanoparticles.