Plant Protein Amyloid Fibrils for Multifunctional Sustainable Materials

Abstract

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 ≈100 nm and rigid fibrils of several micrometers are discovered in 7S/8S and 11S subunits dominated protein, respectively. Structural evolution toward the β‐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.

Amine‐Functionalized Amyloid Aerogels for CO2 Capture

“…To better understand the interaction between the AFs and aminosilane, transmission electron microscopy (TEM) was employed to observe the nanofilaments suspended in water before and after amine modification. The morphology of the three AFs varied, with BLG and lysozyme forming long and straight fibrils, while black bean protein formed short and curly fibrils (Figure S1a, c and e), consistent with previous reports on the morphology characterization of these three classes of protein fibrils [14] . Since silanol groups generated after aminosilane hydrolysis can easily self‐condensate and react with surface hydroxyl groups of the support scaffold, it was observed that BLG and lysozyme fibrils (0.1 wt%) were coated by silica nanoparticles (Figure S1b, d, and Figure S2 and S3).…”

“…Preparation of amyloid fibrils β-lactoglobulin from whey protein isolate and black bean protein were purified according to our previous protocol. [13][14] Lysozyme from chicken egg white was purchased from Sigma-Aldrich. βlactoglobulin amyloid fibrils were prepared by incubation of 2 wt% protein solution at pH 2 and 90 °C for 6 h with magnetic stirring of 300 rpm.…”

“…β ‐lactoglobulin from whey protein isolate and black bean protein were purified according to our previous protocol [13–14] . Lysozyme from chicken egg white was purchased from Sigma–Aldrich.…”

“…As illustrated in Figure 1, AFs from β-lactoglobulin (BLG), lysozyme, and black bean protein were prepared at high temperatures (90 °C) and acidic pH conditions (pH 2). [13][14] The surface of the AFs was then modified with aminosilanes (APTMS, diAPTMS or triAPTMS) through a sol-gel process, developing a self-supporting amine-loaded fibril-silica core-shell structure. Finally, supercritical drying was employed to produce the amine-functionalized AF-templated aerogels.…”

“…The morphology of the three AFs varied, with BLG and lysozyme forming long and straight fibrils, while black bean protein formed short and curly fibrils (Figure S1a, c and e), consistent with previous reports on the morphology characterization of these three classes of protein fibrils. [14] Since silanol groups generated after aminosilane hydrolysis can easily self-condensate and react with surface hydroxyl groups of the support scaffold, it was observed that BLG and lysozyme fibrils (0.1 wt%) were coated by silica nanoparticles (Figure S1b, d, and Figure S2 and S3). In contrast, silica was unevenly deposited onto the surface of black bean fibrils (Figure S1f), possibly due to a low density of accessible surface hydroxyl groups on the short black bean AFs.…”