Amyloid fibril-directed synthesis of silica core–shell nanofilaments, gels, and aerogels

Abstract

Amyloid fibrils have evolved from purely pathological materials implicated in neurodegenerative diseases to efficient templates for last-generation functional materials and nanotechnologies. Due to their high intrinsic stiffness and extreme aspect ratio, amyloid fibril hydrogels can serve as ideal building blocks for material design and synthesis. Yet, in these gels, stiffness is generally not paired by toughness, and their fragile nature hinders significantly their widespread application. Here we introduce an amyloid-assisted biosilicification process, which leads to the formation of silicified nanofibrils (fibril–silica core–shell nanofilaments) with stiffness up to and beyond ∼20 GPa, approaching the Young’s moduli of many metal alloys and inorganic materials. The silica shell endows the silicified fibrils with large bending rigidity, reflected in hydrogels with elasticity three orders of magnitude beyond conventional amyloid fibril hydrogels. A constitutive theoretical model is proposed that, despite its simplicity, quantitatively interprets the nonmonotonic dependence of the gel elasticity upon the filaments bundling promoted by shear stresses. The application of these hybrid silica–amyloid hydrogels is demonstrated on the fabrication of mechanically stable aerogels generated via sequential solvent exchange, supercriticalCO2removal, and calcination of the amyloid core, leading to aerogels of specific surface area as high as 993m2/g, among the highest values ever reported for aerogels. We finally show that the scope of amyloid hydrogels can be expanded considerably by generating double networks of amyloid and hydrophilic polymers, which combine excellent stiffness and toughness beyond those of each of the constitutive individual networks.

Amyloid Fibrils Aerogel for Sustainable Removal of Organic Contaminants from Water

“…The IEP of amyloid fibrils is ≈5.1 . Thus, they are positively charged at a pH lower than IEP and negatively charged at a pH higher than IEP . As observed in Figure 2F, Bentazone and Bisphenol A adsorption is generally less pH dependent than Ibuprofen.…”

“…The pK a of Bentazone, Bisphenol A, and Ibuprofen is 3.3, 9.6–10.2, and 5.2, respectively . Generally, at a pH lower than pK a and close to the aerogels IEP, as the organic pollutant is in molecular form and the net surface charge density of the aerogel is low, the π–π dispersion interaction is increased, which leads to an increase in the adsorbed amount . At a pH higher than the pK a and aerogel IEP, as the organic pollutant is ionized and in an anionic form and amyloid fibrils have a negative surface charge, the electrostatic repulsion is intensified, and consequently, the adsorbed amount decreases .…”

“…Similar to other protein aerogels, around 50% of the total weight loss occurred in the temperature range of 300–500 °C. The residue obtained after the complete decomposition consisted of remaining salts in the system, added during cross‐linking and adjustment of the pH …”

“…To confirm the binding between organics and amyloid fibrils aerogel, Fourier‑transform infrared (FTIR) spectra of the aerogel before and after adsorption of Bentazone were obtained (see Figure S5, Supporting Information). The relative changes between amide I and II bands and the amide III spectral region could confirm the interaction of Bentazone with the aerogel at the peptide links . We determined the adsorption capacity of amyloid fibrils aerogel for the three organic pollutants (see Equation (S3), Supporting Information) .…”

Light Gold: A Colloidal Approach Using Latex Templates

“…BLG amyloid fibrils are rod‐like structures with a diameter of ≈4 nm and a contour length spanning several micrometers . Due to their positive charges at pH = 2, they can bind AuCl 4 − ions to their surface, and BLG further acts as a reducing agent to form gold single crystals of 10–20 µm at 2.6 × 10 −3 m HAuCl 4 , Figure A.…”