Sn-Triggered Two-Dimensional Fast Protein Assembly with Emergent Functions

Protein-Based 2D Nanoarchitectures Constructed by Heterochiral π-Stacking Dimerization of Helical Foldamers

In this study, we focus on the designability and controllability of the interaction interface between secondary structures, and discover an important interface interaction between helical secondary structures by non-covalent synthesis along the helical axis. The formation of discrete heterochiral dimers consisting of left-handed helix and right-handed helix not only helps to discover nonclassical supramolecular chirality phenomena, but also enables controllable protein assembly. Highly ordered nanostructures were thus constructed using π-stacking dimerization of helical foldamers to control tetrameric avidin proteins. The designable and modifiable primitives of artificial folded molecules enable the modification of secondary structure interfaces through non-covalent interactions, leading to the generation of unique structures and functions. These findings are of fundamental importance to the understanding of the precise assembly process of helical foldamers and can provide insights to facilitate the rational design of abiotic protein-like tertiary structures and further functionalization.

Preparation and Formation Mechanism Study of Antibiofilm Coating Based on Phase Transition of Glutenin

The surface of food processing equipment is easily affected by biofilm-forming bacteria, leading to cross-contamination and food safety hazards. The critical issue is how to endow the surface of contact materials with antibacterial and antibiofilm abilities. A sustainable, stable, and antibiofilm coating was prepared by phase transition of glutenin. The disulfide bonds in glutenin were reduced by tris(2-carboxyethyl)phosphine, triggering the phase transition of glutenin. Hydrophobic interactions and intermolecular disulfide bonds may be the primary forces. Furthermore, the phase-transited products formed a nanoscale coating on the surface of stainless steel and glass under their own adhesion force and gravity. The coating exhibited good stability in harsh environments. More importantly, after 3 h of direct contact, the colony of Escherichia coli and Staphylococcus aureus decreased by one logarithm. The amount of biofilm was observed to be significantly decreased through optical microscopy and scanning electron microscopy. This article provides a foundational module for developing novel coatings.

Synthesis and functionalization of scalable and versatile 2D protein films via amyloid-like aggregation

Two-dimensional (2D) protein films can be used to modify the properties of surfaces, and find applications predominantly in the fields of biomaterials, lithography, optics and electronics. However, it is difficult to produce scalable homogeneous and robust protein films with an easy, low-cost, green and efficient method. Further challenges include encapsulating and releasing functional building blocks in the film without inactivating them, and maintaining or improving the bioactivities of proteins used for the formation of the films. Here we detail the process to prepare large 2D protein films with user-defined features and structures via the amyloid-like aggregation of commonly synthesized proteins. These films can be synthesized at meter scales, have high interface adhesion, high functional expansibility and tunable functional properties, obtained by controlling the position of the disulfide bond breakage. For example, we can retain or even enhance the natural antibacterial, biomineralization and antifouling activity of proteins involved in film formation, and the properties can also be expanded through the physical blending or chemical grafting of additional functional blocks on the surface of the film. A 2D protein film can be prepared in ~3 h using four alternative coating techniques: immersion, transfer, hydrogel stamping and spraying. The characterization process of the film requires ~5 d. The procedure can be carried out by users with basic expertise in materials science.

Zwitterionic polymers-armored amyloid-like protein surface combats thrombosis and biofouling

Proteins, cells and bacteria adhering to the surface of medical devices can lead to thrombosis and infection, resulting in significant clinical mortality. Here, we report a zwitterionic polymers-armored amyloid-like protein surface engineering strategy we called as "armored-tank" strategy for dual functionalization of medical devices. The "armored-tank" strategy is realized by decoration of partially conformational transformed LZM (PCTL) assembly through oxidant-mediated process, followed by armoring with super-hydrophilic poly-2-methacryloyloxyethyl phosphorylcholine (pMPC). The outer armor of the "armored-tank" shows potent and durable zone defense against fibrinogen, platelet and bacteria adhesion, leading to long-term antithrombogenic properties over 14 days in vivo without anticoagulation. Additionally, the "fired" PCTL from "armored-tank" actively and effectively kills both Gram-positive and Gram-negative bacterial over 30 days as a supplement to the lacking bactericidal functions of passive outer armor. Overall, this "armored-tank" surface engineering strategy serves as a promising solution for preventing biofouling and thrombotic occlusion of medical devices.

Engineering Immunomodulatory Stents Using Zinc Ion-Lysozyme Nanoparticle Platform for Vascular Remodeling

Rapid endothelialization of cardiovascular materials can enhance the vascular remodeling performance. In this work, we developed a strategy for amyloid-like protein-assembly-mediated interfacial engineering to functionalize a biomimetic nanoparticle coating (BMC). Various groups (e.g., hydroxyl and carboxyl) on the BMC are responsible for chelating Zn2+ ions at the stent interface, similar to the glutathione peroxidase-like enzymes found in vivo. This design could reproduce the release of therapeutic nitric oxide gas (NO) and an aligned microenvironment nearly identical with that of natural vessels. In a rabbit abdominal aorta model, BMC-coated stents promoted vascular healing through rapid endothelialization and the inhibition of intimal hyperplasia in the placement sites at 4, 12, and 24 weeks. Additionally, better anticoagulant activity and immunomodulation in the BMC stents were also confirmed, and vascular healing was mainly dependent on cell signaling through the cyclic guanosine monophosphate-protein kinase G (cGMP-PKG) cascade. Overall, a metal-polypeptide-coated stent was developed on the basis of its detailed molecular mechanism of action in vascular remodeling.

Controllably Self-Assembled Antibacterial Nanofibrils Based on Insect Cuticle Protein for Infectious Wound Healing

Developing self-assembled biomedical materials based on insect proteins is highly desirable due to their advantages of green, rich, and sustainable characters as well as excellent biocompatibility, which has been rarely explored. Herein, salt-induced controllable self-assembly, antibacterial performance, and infectious wound healing performance of an insect cuticle protein (OfCPH-2) originating from the Ostrinia furnacalis larva head capsule are investigated. Interestingly, the addition of salts could trigger the formation of beaded nanofibrils with uniform diameter, whose length highly depends on the salt concentration. Surprisingly, the OfCPH-2 nanofibrils not only could form functional films with broad-spectrum antibacterial abilities but also could promote infectious wound healing. More importantly, a possible wound healing mechanism was proposed, and it is the strong abilities of OfCPH-2 nanofibrils in promoting vascular formation and antibacterial activity that facilitate the process of infectious wound healing. Our exciting findings put forward instructive thoughts for developing innovative bioinspired materials based on insect proteins for wound healing and related biomedical fields.

Amyloid-Like Assembly to Form Film at Interfaces: Structural Transformation and Application

Protein-based biomaterials are attracting broad interest for their remarkable structural and functional properties. Disturbing the native protein's three-dimensional structural stability in vitro and controlling subsequent aggregation is an effective strategy to design and construct protein-based biomaterials. One of the recent developments in regulating protein structural transformation to ordered aggregation is amyloid assembly, which generates fibril-based 1D to 3D nanostructures as functional materials. Especially, the amyloid-like assembly to form films at interfaces has been reported, which is induced by the effective reduction of the intramolecular disulfide bond. The main contribution of this amyloid-like assembly is the large-scale formation of protein films at interfaces and excellent adhesion to target substrates. This review presents the research progress of the amyloid-like assembly to form films and related applications and thereby provides a guide to exploiting protein-based biomaterials.

Microfluidic electrospray generation of porous magnetic Janus reduced graphene oxide/carbon composite microspheres for versatile adsorption

HYPOTHESIS

Graphene-based microparticles materials are broadly utilized in all sorts of fields owing to their outstanding properties. Despite great progress, the present graphene microparticles still face challenges in the aspects of size uniformity, motion flexibility, and tailorable surface chemistry, which limit their application in some specific fields, such as versatile adsorption. Hence, the development of novel graphene microparticles with the aforementioned characteristics is urgently required.

EXPERIMENTS

We presented a simple microfluidic electrospray strategy to generate magnetic Janus reduced graphene oxide/carbon (rGO/C) composite microspheres with a variety of unique features. Specifically, the microfluidic electrospray method endowed the obtaiend microspheres with sufficient size uniformity as well as magnetic responsive motion ability. Additionally, magnetic-mediated surface assembly of phase transition lysozyme (PTL) nanofilm on the microspheres rendered the deposited area hydrophilic while non-deposited area hydrophobic.

FINDINGS

Such magnetic Janus rGO/C composite microspheres with regionalized wettability characteristics not only showed prominent performance in adsorbing organic liquids with high adsorption capacity and remarkable reusability but also displayed satisfying biocompatibility for the efficient uptake of bilirubin. More encouragingly, the microspheres could serve as adsorbents in a simulative hemoperfusion setup, which further demonstrated the clinical application potential of the magnetic Janus rGO/C microspheres. Thus, we anticipate that the obtained magnetic Janus rGO/C composite microspheres could show multifunctional properties toward water treatment and blood molecule cleaning.

Bioinspired nanopillar surface for switchable mechano-bactericidal and releasing actions

Constructing safe and effective antibacterial surfaces has continuously received great attention, especially in healthcare-related fields. Bioinspired mechano-bactericidal nanostructure surfaces could serve as a promising strategy to reduce surface bacterial contamination while avoiding the development of antibiotic resistance. Although effective, these nanostructure surfaces are prone to be contaminated by the accumulation of dead bacteria, inevitably compromising their long-term antibacterial activity. Herein, a bioinspired nanopillar surface with both mechano-bactericidal and releasing actions is developed, via grafting zwitterionic polymer (poly(sulfobetaine methacrylate) (PSBMA)) on ZnO nanopillars. Under dry conditions, this nanopillar surface displays remarkable mechano-bactericidal activity, because the collapsed zwitterionic polymer layer makes no essential influence on nanopillar structure. Once being incubated with aqueous solution, the surface could readily detach the killed bacteria and debris, owing to the swelling of the zwitterionic layer. Consequentially, the surface antibacterial performances can be rapidly and controllably switched between mechano-bactericidal action and bacteria-releasing activity, guaranteeing a long-lasting antibacterial performance. Notably, these collaborative antibacterial behaviors are solely based on physical actions, avoiding the risk of triggering bacteria resistance. The resultant nanopillar surface also enjoys the advantages of substrate-independency and good biocompatibility, offering potential antibacterial applications for biomedical devices and hospital surfaces.

Biocompatible mechano-bactericidal nanopatterned surfaces with salt-responsive bacterial release

Bio-inspired nanostructures have demonstrated highly efficient mechano-bactericidal performances with no risk of bacterial resistance; however, they are prone to become contaminated with the killed bacterial debris. Herein, a biocompatible mechano-bactericidal nanopatterned surface with salt-responsive bacterial releasing behavior is developed by grafting salt-responsive polyzwitterionic (polyDVBAPS) brushes on a bio-inspired nanopattern surface. Benefiting from the salt-triggered configuration change of the grafted polymer brushes, this dual-functional surface shows high mechano-bactericidal efficiency in water (low ionic strength condition), while the dead bacterial residuals can be easily lifted by the extended polymer chains and removed from the surface in 1 M NaCl solution (high ionic strength conditions). Notably, this functionalized nanopatterned surface shows selective biocidal activity between bacterial cells sand eukaryotic cells. The biocompatibility with red blood cells (RBCs) and mammalian cells was tested in vitro. The histocompatibility and prevention of perioperative contamination activity were verified by in vivo evaluation in a rat subcutaneous implant model. This nanopatterned surface with bacterial killing and releasing activities may open new avenues for designing bio-inspired mechano-bactericidal platforms with long-term efficacy, thus presenting a facile alternative in combating perioperative-related bacterial infection. STATEMENT OF SIGNIFICANCE: Bioinspired nanostructured surfaces with noticeable mechano-bactericidal activity showed great potential in moderating drug-resistance. However, the nanopatterned surfaces are prone to be contaminated by the killed bacterial debris and compromised the bactericidal performance. In this study, we provide a dual-functional antibacterial conception with both mechano-bactericidal and bacterial releasing performances not requiring external chemical bactericidal agents. Additionally, this functionalized antibacterial surface also shows selective biocidal activity between bacteria and eukaryotic cells, and the excellent biocompatibility was tested in vitro and in vivo. The new concept for the functionalized mechano-bactericidal surface here illustrated presents a facile antibiotic-free alternative in combating perioperative related bacterial infection in practical application.

Controlling the Structure and Function of Protein Thin Films through Amyloid-like Aggregation

Protein thin films (PTFs) with tunable structure and function can offer multiple opportunities in various fields such as surface modification, biomaterials, packaging, optics, electronics, separation, energy, and environmental science. Although nature may offer a variety of examples of high-level control of structure and function, e.g., the S layer of cells, synthetic alternatives for large-area protein-based thin films with fine control over both biological function and material structure are a key challenge, especially when aiming for facile, low-cost, green, and large-scale preparation as well as a further extension of function, such as the encapsulation and release of functional building blocks.Therefore, regarding the structure and function of PTFs, we will first briefly comment on the problems associated with PTF fabrication, and then, regarding the basis of our long-term research on protein-based thin films, we will summarize the new strategies that we have developed in recent years to explore and control the structure and function of PTFs for frontier research and practical applications.Inspired by naturally occurring protein amyloid fibrillization, we proposed the amyloid-like protein aggregation strategy to assemble proteins into supramolecular 2D films with extremely large sizes and enduring interfacial adhesion stability. This approach opened a new window for PTF fabrication in which the spontaneous interfacial 2D aggregation of protein oligomers instead of traditional 1D protofibril elongation directs the assembly of proteins. As a result, the film morphology, thickness, porosity, and function can be tailored by simply tuning the interfacial aggregation pathways.We further modified amyloid-like protein aggregation to develop chemoselective reaction-induced protein aggregation (CRIPA). It is well known that chemoselective reactions have been employed for protein modification. However, the application of such reactions in PTF fabrication has been overlooked. We initiated this new strategy by employing thiol-disulfide exchange reactions. These reactions are chemoselective toward proteins containing specific disulfide bonds with high redox potentials, resulting in amyloid-like aggregation and thin film formation. Functional proteins with immunity to such reactions can be encapsulated in thin films and released on demand without a loss of activity, opening a new avenue for the development of functional PTFs and coatings.Finally, the resultant amyloid-inspired PTFs, as a new type of biomimetic materials, provide a good platform for integration with various biomedical functions. Here, the creation of bioactive surfaces on virtually arbitrary substrates by amyloid-like PTFs will be discussed, highlighting antimicrobial, antifouling, molecular separation, and interfacial biomineralization activities that exceed those of their native protein precursors and synthetic alternatives.

Engineering Biomolecular Self-Assembly at Solid-Liquid Interfaces

Biomolecular self-assembly is a key process used by life to build functional materials from the "bottom up." In the last few decades, bioengineering and bionanotechnology have borrowed this strategy to design and synthesize numerous biomolecular and hybrid materials with diverse architectures and properties. However, engineering biomolecular self-assembly at solid-liquid interfaces into predesigned architectures lags the progress made in bulk solution both in practice and theory. Here, recent achievements in programming self-assembly of peptides, proteins, and peptoids at solid-liquid interfaces are summarized and corresponding applications are described. Recent advances in the physical understandings of self-assembly pathways obtained using in situ atomic force microscopy are also discussed. These advances will lead to novel strategies for designing biomaterials organized at and interfaced with inorganic surfaces.

Porous assembly of an antifungal protein mediated by zinc and sulfonato-calix[8]arene

Controlled protein assembly holds great potential in the fabrication of biohybrid materials. However, the structural diversity and complexity of proteins present an obstacle to controlled assembly. Supramolecular chemistry is a possible solution as it offers tools to mediate self-assembly with molecular precision. This paper deals with the calixarene- and zinc-mediated assembly and crystallization of the histidine-rich Penicillium chrysogenum antifungal protein B (PAFB). We report crystal structures of pure PAFB, PAFB in complex with Zn²⁺, and the ternary complex of PAFB, Zn²⁺ and sulfonato-calix[8]arene (sclx₈). A comparison of the three crystal structures revealed the structural plasticity of PAFB. While the flexible and highly anionic sclx₈ resulted in large molecular weight aggregates of PAFB in solution, diffraction-quality crystals of PAFB-sclx₈ were not obtained. We report crystals of PAFB-Zn²⁺-sclx₈ in which a trinuclear zinc cluster occurred adjacent to a calixarene binding site. Interestingly, the combination of sclx₈ complexation and zinc coordination resulted in a porous framework with channels of circa 2 nm diameter. Detailed analysis of the crystal structure highlighted novel molecular recognition features. This research enriches the set of supramolecular interactions available to promote protein assembly.

Metal-Protein Hybrid Materials with Desired Functions and Potential Applications

Metal nanohybrids are fast emerging functional nanomaterials with advanced structures, intriguing physicochemical properties, and a broad range of important applications in current nanoscience research. Significant efforts have been devoted toward design and develop versatile metal nanohybrid systems. Among numerous biological components, diverse proteins offer avenues for making advanced multifunctional systems with unusual properties, desired functions, and potential applications. This review discusses the rational design, properties, and applications of metal-protein nanohybrid materials fabricated from proteins and inorganic components. The construction of functional biomimetic nanohybrid materials is first briefly introduced. The properties and functions of these hybrid materials are then discussed. After that, an overview of promising application of biomimetic metal-protein nanohybrid materials is provided. Finally, the key challenges and outlooks related to this fascinating research area are also outlined.

Redox responsive activity regulation in exceptionally stable supramolecular assembly and co-assembly of a protein

Supramolecular assembly of biomolecules/macromolecules stems from the desire to mimic complex biological structures and functions of living organisms. While DNA nanotechnology is already in an advanced stage, protein assembly is still in its infancy as it is a significantly difficult task due to their large molecular weight, conformational complexity and structural instability towards variation in temperature, pH or ionic strength. This article reports highly stable redox-responsive supramolecular assembly of a protein Bovine serum albumin (BSA) which is functionalized with a supramolecular structure directing unit (SSDU). The SSDU consists of a benzamide functionalized naphthalene-diimide (NDI) chromophore which is attached with the protein by a bio-reducible disulfide linker. The SSDU attached protein (NDI-BSA) exhibits spontaneous supramolecular assembly in water by off-set π-stacking among the NDI chromophores, leading to the formation of spherical nanoparticles (diameter: 150-200 nm). The same SSDU when connected with a small hydrophilic wedge (NDI-1) instead of the large globular protein, exhibits a different π-stacking mode with relatively less longitudinal displacement which results in a fibrillar network and hydrogelation. Supramolecular co-assembly of NDI-BSA and NDI-1 (3 : 7) produces similar π-stacking and an entangled 1D morphology. Both the spherical assembly of NDI-BSA or the fibrillar co-assembly of NDI-BSA + NDI-1 (3 : 7) provide sufficient thermal stability to the protein as its thermal denaturation could be completely surpassed while the secondary structure remained intact. However, the esterase like activity of the protein reduced significantly as a result of such supramolecular assembly indicating limited access by the substrate to the active site of the enzyme located in the confined environment. In the presence of glutathione (GSH), a biologically important tri-peptide, due to the cleavage of the disulfide bond, the protein became free and was released, resulting in fully regaining its enzymatic activity. Such supramolecular assembly provided excellent protection to the protein against enzymatic hydrolysis as the relative hydrolysis was estimated to be <30% for the co-assembled protein with respect to the free protein under identical conditions. Similar to bioactivity, the enzymatic hydrolysis also became prominent after GSH-treatment, confirming that the lack of hydrolysis in the supramolecularly assembled state is indeed related to the confinement of the protein in the nanostructure assembly.

Universal Antibacterial Surfaces Fabricated from Quaternary Ammonium Salt-Based PNIPAM Microgels

Because of the excellent film-forming ability of poly(N-isopropylacrylamide) (PNIPAM) microgel and high-efficient bactericidal property of quaternary ammonium salt (QAS), QAS-based PNIPAM (QAS-PNIPAM) microgels are synthesized and employed to modify the surface of a range of commonly used materials including metal, plastic, and elastomer. Bacterial culture is carried out on such QAS-PNIPAM microgel-modified surfaces to examine the viability of the attached bacteria. It is found that the bactericidal efficiency is nearly 100% on the modified surfaces of all the studied materials. We attribute the high-efficient bactericidal performance of QAS-PNIPAM microgel film to the QAS component rather than the topography of the microgel film itself. In addition, the microgel film is robust and shows great integrity even after culture of the bacteria and repeated rinses, and the cell experiment demonstrates that this microgel film is cyto-compatible. Therefore, such a simple, versatile method of preparing antibacterial films paves the way for future bactericidal applications.