Understanding Biomolecular Crystallization on Amyloid‐Like Superhydrophobic Biointerface

Abstract

biohybrids. [6] With respect to the crystallization, a protein-based biopolymer substrate is typically utilized in nature to develop excellent biomineralization system. [7] Vice versa, the utilization of mineral substrates, [8] chemically modified mica, [9] gel, [10] silanized polystyrene wells, [11] lipid layers, [12] polymeric film surfaces [13] as well as porous media, [14] etc. have contributed a lot to protein crystallization. Some conjectures have been made from these studies, typically including concentration effect-induced change of supersaturation extent near a surface, [15] adsorption of solutes on a surface, [16] specific interaction between solutes and chemically modified surfaces, [17] the presence of surface microtopography, and spatial characteristics to guide nucleation and crystalline lattice. [18] However, despite immense progress, understanding the crystallization mechanism of proteins and peptides on solid surface remains elusive, and more fundamental clues to reveal this process should be discovered. In this regard, a superhydrophobic surface would be an ideal platform for the crystallization design, since such an interface exhibits great feasibility to concentrate solutes in the sessile droplet [19] and this simplified model induces efficient crystallization of salts, [20] colloidal assembly [21] as well as detection enhancement. [22] Such a platform actually has found a wide range of important applications in current medicine and biotechnology, [23] such as protein adsorption, [24a] drug release, [24b,c] cellular interaction, [24d] and so on. [24e]

Tailoring Materials with Specific Wettability in Biomedical Engineering

“…As a heterogeneous nucleation platform, superhydrophobic surfaces have demonstrated values in facilitating the biocrystallization process and endowing the products with high quality. [172,173] Especially the biomolecule-assembled superhydrophobic surfaces have intrinsic advantages of biocompatibility, nontoxicity, and biodegradability, which make them suitable for biomedical applications. Based on the self-assembly of lysozyme, Gao et al fabricated a superhydrophobic surface and applied it for protein crystallization.…”

“…Wu et al also took advantage of a superhydrophobic proteinaceous platform to facilitate preferential crystallization of proteins and peptides. [173] These typical examples reveal that surfaces with special wettability would open a new chapter in fundamental research of biomolecules.…”

Developing Biopolymer Mesocrystals by Crystallization of Secondary Structures

“…It has been reported that an intramolecular disulfide bond is critical to stabilize protein tertiary or quaternary structures. , As a result, a reduction in the number of disulfide bonds led to a mild unfolding of the proteins, which subsequently induced the transformation of chain secondary structures into predominant β-sheets in insulin single crystals . In this regard, Yang et al developed a strategy to realize the nucleation–crystallization of proteins by unfolding native lysozyme, insulin, bovine serum albumin (BSA), or α-lactalbumin via the reduction of their intramolecular disulfide bonds. − Tris­(2-carboxyethyl)­phosphine (TCEP) reduced disulfide bonds effectively in lysozyme, ,− which consequently induced protein unfolding and then self-assembly of unfolded protein chains into short-range β-sheets without complex pre-steps (Figure A). The reduction of disulfide bonds was clearly reflected through Raman spectra and N -(1-pyrenyl)­maleimide (NPM) assay (Figure B), and the transformation to β-sheets was then characterized by circular dichroism (CD) and Fourier transform infrared (FTIR) spectroscopy (Figure C).…”

“…The unfolded protein aggregates containing short-range interchain alignments were sensitive to the solvent environment, so the structures of such short-range β-sheet assemblies could be tuned by using different conditions. ,− Under quasi-equilibrium conditions, short-range β-sheets could be further crystallized to form vast protein nanocrystals (Figure F). These nanocrystals had typical “core–shell” structures, in which crystalline cores, orderly packed from β-sheets, were embedded into amorphous flexible chain shells, similar to the structure of organic–inorganic nanocrystals in biomineralization, and could assemble with a specific orientation into mesocrystals (vide infra).…”

“…In contrast to the nucleation at quasi-equilibrium condition, a rapid nonequilibrium assembly of short-range β-sheet aggregates (superfast amyloid-like protein assembly) could produce a 2D protein nanofilm at the air/water interface and sub-micrometer-scale particles in bulk solution at the same time. − As a photoresist, the 2D protein nanofilm could support a facile and green photolithography strategy, which could give tunable patterns through a short-time UV/e-beam exposure under a covered mask, followed by removal of the photoresist with water. , Like amyloid structures in nature, the protein nanofilm has the ability to adhere to different material surfaces due to multiplex binding (including hydrogen bonding, hydrophobic interaction, electrostatic interaction, metal–S interaction, and surface roughness) and has antibacterial properties due to the positively charged and hydrophobic residues exposed on the film surface. − Furthermore, the protein nanofilm could be an ideal intermediate-layer material for guiding electroless deposition, hydroxy­apatite mineralization, and chemical modification on inorganic, organic, and even living cell surfaces. ,− On the other hand, the sub-micrometer particles aggregate into network structures, which could provide a platform with emerging applications including a superhydrophobic surface for facilitating protein crystallization, a smart surface for capturing or releasing drug-loaded cell-sized lipid vesicles, and a biochip for detecting small molecules and macromolecules. − …”