Nanocellulose aerogels as 3D amyloid templates

Abstract

Proteins in solution tend to coat solid surfaces upon exposure. Depending on the nature of the surface, the environmental conditions, and the nature of the protein these adsorbed proteins may self-assemble into ordered, fibre-like structures called amyloids. Nanoparticulate surfaces, with their high surface to volume ratio, are particularly favourable to amyloid formation. Most prior research has focussed on either inorganic or organic nanoparticles in solution. In this research, we instead focus on aerogels created from TEMPO-oxidized cellulose nanofibers (TO-CNF) to serve as bio-based, three-dimensional amyloid templates with a tuneable surface chemistry. Previous research on the use of cellulose as a protein adsorption template has shown no evidence of a change in the secondary protein structure. Herein, however, with the aid of the reducing agent TCEP, we were able to induce the formation of amyloid-like ‘worms’ on the surface of TO-CNF aerogels. Furthermore, we demonstrate that the addition of the TO-CNF aerogel can also induce bulk aggregation under conditions where it previously did not exist. Finally, we show that the addition of the aerogel increases the rate of ‘worm’ formation in conditions where previous research has found a long lag-phase. Therefore, TO-CNF aerogels are shown to be excellent templates for inducing ordered protein aggregation.