Diverse Supramolecular Nanofiber Networks Assembled by Functional Low-Complexity Domains

Strategies and Applications for Supramolecular Protein Self-Assembly

Supramolecular chemistry achieves higher-order molecular self-assembly through non-covalent interactions. Utilizing supramolecular methods to explore the polymorphism of proteins, the building blocks of life, from a "bottom-up" perspective is essential for constructing diverse and functional biomaterials. In recent years, significant progress has been achieved in the design strategies and functional applications of supramolecular protein self-assembly, becoming a focal point for researchers. This paper reviews classical supramolecular strategies driving protein self-assembly, including electrostatic interactions, metal coordination, hydrogen bonding, hydrophobic interactions, host-guest interactions, and other mechanisms. We discuss how these supramolecular interactions regulate protein assembly processes and highlight protein supramolecular assemblies' unique structural and functional advantages in constructing artificial photosynthetic systems, protein hydrogels, bio-delivery systems, and other functional materials. The enormous potential and significance of supramolecular protein materials are elucidated. Finally, the challenges in preparing and applying protein supramolecular assemblies are summarized, and future development directions are projected.

Engineering π-Conjugation of Phenylalanine Derivatives for Controllable Chiral Folding and Self-Assemblies

π-π stacking interaction is an attractive interaction that involves aromatic groups containing π-conjugated domains. It is a promising strategy for stabilizing folded structures with interesting chiroptical properties and manipulating the supramolecular chiral self-assembly process. In this study, we report the engineering of π-conjugated amino acids that utilize π-π stacking interactions to manipulate chiral folding as well as self-assembly evolution. Stepwise conjugation of phenyl, naphthyl, and pyrenyl to N-terminal phenylalanine derivatives witnessed the folding through intramolecular π-interactions in solution phase, which facilitated the formation of chiral geometry and the emergence of chiral optics. Introduction of aromatic domains efficiently lowers the critical aggregation concentration in the aqueous media. Molecular folding enables a special concentration-dependent self-assembly, whereby the supramolecular chirality accomplished inversion with the evolution of helical nanoarchitectures. This work develops a strategy to engineer π-conjugated amino acids with controllable folding behaviors, which also offers implications for the rational design of functional chiral materials.

Engineered Living Materials For Sustainability

Recent advances in synthetic biology and materials science have given rise to a new form of materials, namely engineered living materials (ELMs), which are composed of living matter or cell communities embedded in self-regenerating matrices of their own or artificial scaffolds. Like natural materials such as bone, wood, and skin, ELMs, which possess the functional capabilities of living organisms, can grow, self-organize, and self-repair when needed. They also spontaneously perform programmed biological functions upon sensing external cues. Currently, ELMs show promise for green energy production, bioremediation, disease treatment, and fabricating advanced smart materials. This review first introduces the dynamic features of natural living systems and their potential for developing novel materials. We then summarize the recent research progress on living materials and emerging design strategies from both synthetic biology and materials science perspectives. Finally, we discuss the positive impacts of living materials on promoting sustainability and key future research directions.

Biopolymer coating for particle surface engineering and their biomedical applications

Surface engineering of particles based on a polymeric coating is of great interest in materials design and applications. Due to the disadvantages of non-biodegradability and undesirable biocompatibility, the application of petroleum-based synthetic polymers coating in the biomedical field has been greatly limited. In addition, there is lack of a universal surface modification method to functionalize particles of different compositions, sizes, shapes, and structures. Thus, it is imperative to develop a versatile biopolymeric coating with good biocompatibility and tunable biodegradability for the preparation of functional particle materials regardless of their surface chemical and physical structures. Recently, the natural polysaccharide polymers (e.g. chitosan and cellulose), polyphenol-based biopolymers (e.g. polydopamine and tannic acid), and proteins (e.g. amyloid-like aggregates) have been utilized in surface modification of particles, and applications of these modified particles in the field of biomedicine have been also intensively exploited. In this review, the preparation of the above three coatings on particles surface are summarized, and the applications of these materials in drug loading/release, biomineralization, cell immobilization/protection, enzyme immobilization/protection, and antibacterial/antiviral are exemplified. Finally, the challenges and the future research directions on biopolymer coating for particles surface engineering are prospected.

Rational Design of a Zr-MOF@Curli-Polyelectrolyte Hybrid Membrane toward Efficient Chemical Protection, Moisture Permeation, and Catalytic Detoxification

Developing high-performance protective materials is important for soldiers and civilians who are exposed to the atmosphere of highly toxic chemical warfare agents (CWAs). Polyelectrolyte membranes are promising candidates with excellent chemical resistance and moisture permeability, but they cannot efficiently degrade CWAs. Here, we design and prepare a hybrid membrane through in situ growth of catalytically active zirconium-based metal-organic frameworks (Zr-MOFs) on a polyelectrolyte membrane mediated by biofilm-inspired curli nanofibers (CNFs). Superior to the bare polyelectrolyte membrane, the prepared MOF-808@CNF-PQ hybrid membrane exhibits improved rejection of the nerve agent simulant dimethyl methyl phosphonate (DMMP) vapor and permeation of the water vapor by 113 and 45%, respectively. The water/DMMP selectivity of the hybrid membrane reaches 498.6, approximately 13 times that of the commercial polyelectrolyte membrane Nafion 117. In addition, the hybrid membrane possesses appreciable catalytic activity for the hydrolysis of the nerve agent simulant dimethyl 4-nitrophenyl phosphate (DMNP) with a half-life of ∼38 min. Nanomechanical characterization results based on atomic force microscopy (AFM) techniques demonstrate the critical role of CNFs in mediating Zr-MOF nucleation and the dominant effect of electrostatic interactions on self-assembly of CNFs on polyelectrolyte base. It is also confirmed that the Zr-MOF toppings serve as the key components in physically adsorbing and chemically degrading the DMNP molecules through multiple strong intermolecular interactions. Our work offers a rational strategy to develop advanced membranes toward efficient chemical protection, moisture permeation, and catalytic detoxification against CWAs.

Molecular-level insights into the surface-induced assembly of functional bacterial amyloid

Protein coating material is important in many technological fields. The interaction between carbon nanomaterial and protein is especially interesting since it makes the development of novel hybrid materials possible. Functional bacterial amyloid (FuBA) is promising as a coating material because of its desirable features, such as well-defined molecular structure, robustness against harsh conditions, and easily engineerable functionality. Here, we report the systematic assembly of the functional amyloid protein, CsgA, from Escherichia coli (E. coli) on graphite. We characterize the assemblies using scanning tunneling microscopy (STM) and show that CsgA forms assemblies according to systematic patterns, dictated by the graphite lattice. In addition, we show that graphite flakes induce the fibrillization of CsgA, in vitro, suggesting a surface-induced conformational change of CsgA facilitated by the graphite lattice. Using coarse-grained molecular dynamics simulations, we model the adhesion and lamellar formation of a CsgA-derived peptide and conclude that peptides are adsorbed both as monomers and smaller aggregates leading initially to unordered graphite-bound aggregates, which are followed by rearrangement into lamellar structures. Finally, we show that CsgA-derived peptides can be immobilized in very systematic assemblies and their molecular orientation can be tuned using a small chaperone-like molecule. Our findings have implications for the development of FuBA-based biosensors, catalysts, and other technologies requiring well-defined protein assemblies on graphite.

Functional Bacterial Amyloids: Understanding Fibrillation, Regulating Biofilm Fibril Formation and Organizing Surface Assemblies

Functional amyloid is produced by many organisms but is particularly well understood in bacteria, where proteins such as CsgA (E. coli) and FapC (Pseudomonas) are assembled as functional bacterial amyloid (FuBA) on the cell surface in a carefully optimized process. Besides a host of helper proteins, FuBA formation is aided by multiple imperfect repeats which stabilize amyloid and streamline the aggregation mechanism to a fast-track assembly dominated by primary nucleation. These repeats, which are found in variable numbers in Pseudomonas, are most likely the structural core of the fibrils, though we still lack experimental data to determine whether the repeats give rise to β-helix structures via stacked β-hairpins (highly likely for CsgA) or more complicated arrangements (possibly the case for FapC). The response of FuBA fibrillation to denaturants suggests that nucleation and elongation involve equal amounts of folding, but protein chaperones preferentially target nucleation for effective inhibition. Smart peptides can be designed based on these imperfect repeats and modified with various flanking sequences to divert aggregation to less stable structures, leading to a reduction in biofilm formation. Small molecules such as EGCG can also divert FuBA to less organized structures, such as partially-folded oligomeric species, with the same detrimental effect on biofilm. Finally, the strong tendency of FuBA to self-assemble can lead to the formation of very regular two-dimensional amyloid films on structured surfaces such as graphite, which strongly implies future use in biosensors or other nanobiomaterials. In summary, the properties of functional amyloid are a much-needed corrective to the unfortunate association of amyloid with neurodegenerative disease and a testimony to nature's ability to get the best out of a protein fold.

Hydrophobic immiscibility controls self-sorting or co-assembly of peptide amphiphiles

Pairs of peptide amphiphiles with immiscible hydrophobic tails were synthesized and their assembly formation was investigated. These pairs formed self-sorting supramolecular fibres using a standard heating-cooling protocol, while one pair with longer hydrophobic tails formed a co-assembly when an additional heating process was applied.

Engineering of biofilms with a glycosylation circuit for biomaterial applications

Glycosylation is a crucial post-translational modification for a wide range of functionalities. Adhesive protein-based biomaterials in nature rely on heavily glycosylated proteins such as spider silk and mussel adhesive proteins. Engineering protein-based biomaterials genetically enables desired functions and characteristics. Additionally, utilization of glycosylation for biomaterial engineering can expand possibilities by including saccharides to the inventory of building blocks. Here, de novo glycosylation of Bacillus subtilis amyloid-like biofilm protein TasA using a Campylobacter jejuni glycosylation circuit is proposed to be a novel biomaterial engineering method for increasing adhesiveness of TasA fibrils. A C. jejuni glycosylation motif is genetically incorporated to tasA gene and expressed in Escherichia coli containing the C. jejuni pgl protein glycosylation pathway. Glycosylated TasA fibrils indicate enhanced adsorption on the gold surface without disruption of fibril formation. Our findings suggest that N-linked glycosylation can be a promising tool for engineering protein-based biomaterials specifically regarding adhesion.

Conformable self-assembling amyloid protein coatings with genetically programmable functionality

Functional coating materials have found broad technological applications in diverse fields. Despite recent advances, few coating materials simultaneously achieve robustness and substrate independence while still retaining the capacity for genetically encodable functionalities. Here, we report Escherichia coli biofilm-inspired protein nanofiber coatings that simultaneously exhibit substrate independence, resistance to organic solvents, and programmable functionalities. The intrinsic surface adherence of CsgA amyloid proteins, along with a benign solution-based fabrication approach, facilitates forming nanofiber coatings on virtually any surface with varied compositions, sizes, shapes, and structures. In addition, the typical amyloid structures endow the nanofiber coatings with outstanding robustness. On the basis of their genetically engineerable functionality, our nanofiber coatings can also seamlessly participate in functionalization processes, including gold enhancement, diverse protein conjugations, and DNA binding, thus enabling a variety of proof-of-concept applications, including electronic devices, enzyme immobilization, and microfluidic bacterial sensors. We envision that our coatings can drive advances in electronics, biocatalysis, particle engineering, and biomedicine.

A near-infrared fluorescent probe quinaldine red lights up the β-sheet structure of amyloid proteins in mouse brain

In this report, we describe a near-infrared fluorescent probe called quinaldine red (QR) which lights up the β-sheet structure of amyloid fibrils. The photochemical and biophysical properties of QR along with other canonical amyloid probes in the presence of protein fibrils were investigated by using fluorescence spectroscopy, confocal fluorescent microscopy and isothermal titration calorimetry. Moreover, the binding sites and interaction mode between QR and insulin fibrils were calculated based on molecule docking. Among these amyloid probes, QR showed several advantages including strong supramolecular force, near-infrared emission, high sensitivity and resistance to bleaching. A linear response of the fluorescence intensity of QR towards fibril samples in the presence of sera was visualized in the range of 1-30 μM, with the limit of detection (LOD) of 2.31 μM. The recovery and relative standard deviation (RSD) of the proposed method for the determination of protein fibrils was 90.4%-99.2% and 3.05%-3.47%, respectively. Finally, QR can be fluorescently lighted up when meeting the aberrant protein aggregates of pathogenic mice. We recommend QR as a novel and excellent alternative tool for monitoring conformational transition of amyloid proteins.

Bottom-up synthesis of protein-based nanomaterials from engineered β-solenoid proteins

Biomolecular self-assembly is an emerging bottom-up approach for the synthesis of novel nanomaterials. DNA and viruses have both been used to create scaffolds but the former lacks chemical diversity and the latter lack spatial control. To date, the use of protein scaffolds to template materials on the nanoscale has focused on amyloidogenic proteins that are known to form fibrils or two-protein systems where a second protein acts as a cross-linker. We previously developed a unique approach for self-assembly of nanomaterials based on engineering β-solenoid proteins (BSPs) to polymerize into micrometer-length fibrils. BSPs have highly regular geometries, tunable lengths, and flat surfaces that are amenable to engineering and functionalization. Here, we present a newly engineered BSP based on the antifreeze protein of the beetle Rhagium inquisitor (RiAFP-m9), which polymerizes into stable fibrils under benign conditions. Gold nanoparticles were used to functionalize the RiAFP-m9 fibrils as well as those assembled from the previously described SBAFP-m1 protein. Cysteines incorporated into the sequences provide site-specific gold attachment. Additionally, silver was deposited on the gold-labelled fibrils by electroless plating to create nanowires. These results bolster prospects for programable self-assembly of BSPs to create scaffolds for functional nanomaterials.

The Power of Confocal Laser Scanning Microscopy in Supramolecular Chemistry: In situ Real-time Imaging of Stimuli-Responsive Multicomponent Supramolecular Hydrogels

Multicomponent supramolecular hydrogels are promising scaffolds for applications in biosensors and controlled drug release due to their designer stimulus responsiveness. To achieve rational construction of multicomponent supramolecular hydrogel systems, their in-depth structural analysis is essential but still challenging. Confocal laser scanning microscopy (CLSM) has emerged as a powerful tool for structural analysis of multicomponent supramolecular hydrogels. CLSM imaging enables real-time observation of the hydrogels without the need of drying and/or freezing to elucidate their static and dynamic properties. Through multiple, selective fluorescent staining of materials of interest, multiple domains formed in supramolecular hydrogels (e. g. inorganic materials and self-sorting nanofibers) can also be visualized. CLSM and the related microscopic techniques will be indispensable to investigate complex life-inspired supramolecular chemical systems.

Supramolecular Self-Assembly To Control Structural and Biological Properties of Multicomponent Hydrogels

Self-assembled nanofibers are ubiquitous in nature and serve as inspiration for the design of supramolecular hydrogels. A multicomponent approach offers the possibility of enhancing the tunability and functionality of this class of materials. We report on the synergistic multicomponent self-assembly involving a peptide amphiphile (PA) and a 1,3:2,4-dibenzylidene-d-sorbitol (DBS) gelator to generate hydrogels with tunable nanoscale morphology, improved stiffness, enhanced self-healing, and stability to enzymatic degradation. Using induced circular dichroism of Thioflavin T (ThT), electron microscopy, small-angle neutron scattering, and molecular dynamics approaches, we confirm that the PA undergoes self-sorting, while the DBS gelator acts as an additive modifier for the PA nanofibers. The supramolecular interactions between the PA and DBS gelators result in improved bulk properties and cytocompatibility of the two-component hydrogels as compared to those of the single-component systems. The tunable mechanical properties, self-healing ability, resistance to proteolysis, and biocompatibility of the hydrogels suggest future opportunities for the hydrogels as scaffolds for tissue engineering and drug delivery vehicles.

Exploiting mammalian low-complexity domains for liquid-liquid phase separation-driven underwater adhesive coatings

Many biological materials form via liquid-liquid phase separation (LLPS), followed by maturation into a solid-like state. Here, using a biologically inspired assembly mechanism designed to recapitulate these sequential assemblies, we develop ultrastrong underwater adhesives made from engineered proteins containing mammalian low-complexity (LC) domains. We show that LC domain-mediated LLPS and maturation substantially promotes the wetting, adsorption, priming, and formation of dense, uniform amyloid nanofiber coatings on diverse surfaces (e.g., Teflon), and even penetrating difficult-to-access locations such as the interiors of microfluidic devices. Notably, these coatings can be deposited on substrates over a broad range of pH values (3 to 11) and salt concentrations (up to 1 M NaCl) and exhibit strong underwater adhesion performance. Beyond demonstrating the utility of mammalian LC domains for driving LLPS in soft materials applications, our study illustrates a powerful example of how combining LLPS with subsequent maturation steps can be harnessed for engineering protein-based materials.

Modular genetic design of multi-domain functional amyloids: insights into self-assembly and functional properties

Engineering functional amyloids through a modular genetic strategy represents new opportunities for creating multifunctional molecular materials with tailored structures and performance. Despite important advances, how fusion modules affect the self-assembly and functional properties of amyloids remains elusive. Here, using Escherichia coli curli as a model system, we systematically studied the effect of flanking domains on the structures, assembly kinetics and functions of amyloids. The designed amyloids were composed of E. coli biofilm protein CsgA (as amyloidogenic cores) and one or two flanking domains, consisting of chitin-binding domains (CBDs) from Bacillus circulans chitinase, and/or mussel foot proteins (Mfps). Incorporation of fusion domains did not disrupt the typical β-sheet structures, but indeed affected assembly rate, morphology, and stiffness of resultant fibrils. Consequently, the CsgA-fusion fibrils, particularly those containing three domains, were much shorter than the CsgA-only fibrils. Furthermore, the stiffness of the resultant fibrils was heavily affected by the structural feature of fusion domains, with β-sheet-containing domains tending to increase the Young's modulus while random coil domains decreasing the Young's modulus. In addition, fibrils containing CBD domains showed higher chitin-binding activity compared to their CBD-free counterparts. The CBD-CsgA-Mfp3 construct exhibited significantly lower binding activity than Mfp5-CsgA-CBD due to inappropriate folding of the CBD domain in the former construct, in agreement with results based upon molecular dynamics modeling. Our study provides new insights into the assembly and functional properties of designer amyloid proteins with increasing complex domain structures and lays the foundation for the future design of functional amyloid-based structures and molecular materials.

Directing curli polymerization with DNA origami nucleators

The physiological or pathological formation of fibrils often relies on molecular-scale nucleators that finely control the kinetics and structural features. However, mechanistic understanding of how protein nucleators mediate fibril formation in cells remains elusive. Here, we develop a CsgB-decorated DNA origami (CB-origami) to mimic protein nucleators in Escherichia coli biofilm that direct curli polymerization. We show that CB-origami directs curli subunit CsgA monomers to form oligomers and then accelerates fibril formation by increasing the proliferation rate of primary pathways. Fibrils grow either out from (departure mode) or towards the nucleators (arrival mode), implying two distinct roles of CsgB: as nucleation sites and as trap sites to capture growing nanofibrils in vicinity. Curli polymerization follows typical stop-and-go dynamics but exhibits a higher instantaneous elongation rate compared with independent fibril growth. This origami nucleator thus provides an in vitro platform for mechanistically probing molecular nucleation and controlling directional fibril polymerization for bionanotechnology.

Prion-based nanomaterials and their emerging applications

Protein misfolding and aggregation into highly ordered fibrillar structures have been traditionally associated with pathological processes. Nevertheless, nature has taken advantage of the particular properties of amyloids for functional purposes, like in the protection of organisms against environmental changing conditions. Over the last decades, these fibrillar structures have inspired the design of new nanomaterials with intriguing applications in biomedicine and nanotechnology such as tissue engineering, drug delivery, adhesive materials, biodegradable nanocomposites, nanowires or biosensors. Prion and prion-like proteins, which are considered a subclass of amyloids, are becoming ideal candidates for the design of new and tunable nanomaterials. In this review, we discuss the particular properties of this kind of proteins, and the current advances on the design of new materials based on prion sequences.

Targetable Mechanical Properties by Switching between Self-Sorting and Co-assembly with In Situ Formed Tripodal Ketoenamine Supramolecular Hydrogels

A new family of supramolecular hydrogelators are introduced in which self-sorting and co-assembly can be utilised in the tuneability of the mechanical properties of the materials, a property closely tied to the nanostructure of the gel network. The in situ reactivity of the components of the gelators allows for system chemistry concepts to be applied to the formation of the gels and shows that molecular properties, and not necessarily the chemical identity, determines some gel properties in these family of gels.

Minimalist Prion-Inspired Polar Self-Assembling Peptides

Nature provides copious examples of self-assembling supramolecular nanofibers. Among them, amyloid structures have found amazing applications as advanced materials in fields such as biomedicine and nanotechnology. Prions are a singular subset of proteins able to switch between a soluble conformation and an amyloid state. The ability to transit between these two conformations is encoded in the so-called prion domains (PrDs), which are long and disordered regions of low complexity, enriched in polar and uncharged amino acids such as Gln, Asn, Tyr, Ser, and Gly. The polar nature of PrDs results in slow amyloid formation, which allows kinetic control of fiber assembly. This approach has been exploited for fabrication of multifunctional materials because in contrast to most amyloids, PrDs lack hydrophobic stretches that can nucleate their aggregation, their assembly depends on the establishment of a large number of weak interactions along the complete domain. The length and low complexity of PrDs make their chemical synthesis for applied purposed hardly affordable. Here, we designed four minimalist polar binary patterned peptides inspired in PrDs, which include the [Q/N/G/S]-Y-[Q/N/G/S] motif frequently observed in these domains: NYNYNYN, QYQYQYQ, SYSYSYS, and GYGYGYG. Despite their small size, they all recapitulate the properties of full-length PrDs, self-assembling into nontoxic amyloids under physiological conditions. Thus, they constitute small building blocks for the construction of tailored prion-inspired nanostructures. We exploited Tyr residues in these peptides to generate highly stable dityrosine cross-linked assemblies for the immobilization of metal nanoparticles in the fibrils surface and to develop an electrocatalytic amyloid scaffold. Moreover, we show that the shorter and more polar NYNNYN, QYQQYQ, and SYSSYS hexapeptides also self-assemble into amyloid-like structures, consistent with the presence of these tandem motifs in human prion-like proteins.

Adhesive bacterial amyloid nanofiber-mediated growth of metal-organic frameworks on diverse polymeric substrates

Adhesive curli nanofibers, bacterial biofilms' major protein component, were utilized to mediate the growth of MOFs on various polymeric substrates.

The development of a simple, robust, and generalizable approach for spatially controlled growth of metal–organic frameworks (MOFs) on diverse polymeric substrates is of profound technological significance but remains a major challenge. Here, we reported the use of adhesive bacterial amyloid nanofibers, also known as curli nanofibers (CNFs), major protein components of bacterial biofilms, as universal and chemically/mechanically robust coatings on various polymeric substrates to achieve controlled MOF growth with improved surface coverage up to 100-fold. Notably, owing to the intrinsic adhesive attributes of CNFs, our approach is applicable for MOF growth on both 2D surfaces and 3D objects regardless of their geometric complexity. Applying this technique to membrane fabrication afforded a thin-film composite membrane comprising a 760 ± 80 nm ZIF-8 selective layer grown on a microporous polyvinylidene fluoride (PVDF) support which exhibited a C₃H₆/C₃H₈ mixed-gas separation factor up to 10, C₃H₆ permeance up to 1110 GPU and operational stability up to 7 days. Our simple yet robust approach therefore provides new insights into designing new interfaces for mediating MOF growth and opens new opportunities for constructing new MOF-based membranes and devices.

Acorn Barnacles Secrete Phase-Separating Fluid to Clear Surfaces Ahead of Cement Deposition

Marine macrofoulers (e.g., barnacles, tubeworms, mussels) create underwater adhesives capable of attaching themselves to almost any material. The difficulty in removing these organisms frustrates maritime and oceanographic communities, and fascinates biomedical and industrial communities seeking synthetic adhesives that cure and hold steadfast in aqueous environments. Protein analysis can reveal the chemical composition of natural adhesives; however, developing synthetic analogs that mimic their performance remains a challenge due to an incomplete understanding of adhesion processes. Here, it is shown that acorn barnacles (Amphibalanus (=Balanus) amphitrite) secrete a phase-separating fluid ahead of growth and cement deposition. This mixture consists of a phenolic laden gelatinous phase that presents a phase rich in lipids and reactive oxygen species at the seawater interface. Nearby biofilms rapidly oxidize and lift off the surface as the secretion advances. While phenolic chemistries are ubiquitous to arthropod adhesives and cuticles, the findings demonstrate that A. amphitrite uses these chemistries in a complex surface-cleaning fluid, at a substantially higher relative abundance than in its adhesive. The discovery of this critical step in underwater adhesion represents a missing link between natural and synthetic adhesives, and provides new directions for the development of environmentally friendly biofouling solutions.

Painting Supramolecular Polymers in Organic Solvents by Super-resolution Microscopy

Despite the rapid development of complex functional supramolecular systems, visualization of these architectures under native conditions at high resolution has remained a challenging endeavor. Super-resolution microscopy was recently proposed as an effective tool to unveil one-dimensional nanoscale structures in aqueous media upon chemical functionalization with suitable fluorescent probes. Building upon our previous work, which enabled photoactivation localization microscopy in organic solvents, herein, we present the imaging of one-dimensional supramolecular polymers in their native environment by interface point accumulation for imaging in nanoscale topography (iPAINT). The noncovalent staining, typical of iPAINT, allows the investigation of supramolecular polymers' structure in situ without any chemical modification. The quasi-permanent adsorption of the dye to the polymer is exploited to identify block-like arrangements within supramolecular fibers, which were obtained upon mixing homopolymers that were prestained with different colors. The staining of the blocks, maintained by the lack of exchange of the dyes, permits the imaging of complex structures for multiple days. This study showcases the potential of PAINT-like strategies such as iPAINT to visualize multicomponent dynamic systems in their native environment with an easy, synthesis-free approach and high spatial resolution.

How should multicomponent supramolecular gels be characterised?

We discuss the current state of characterising multicomponent low molecular weight gels across all length scales, and the effectiveness of the different techniques that have been used.

Lessons learned from protein aggregation: toward technological and biomedical applications

The close relationship between protein aggregation and neurodegenerative diseases has been the driving force behind the renewed interest in a field where biophysics, neurobiology and nanotechnology converge in the study of the aggregate state. On one hand, knowledge of the molecular principles that govern the processes of protein aggregation has a direct impact on the design of new drugs for high-incidence pathologies that currently can only be treated palliatively. On the other hand, exploiting the benefits of protein aggregation in the design of new nanomaterials could have a strong impact on biotechnology. Here we review the contributions of our research group on novel neuroprotective strategies developed using a purely biophysical approach. First, we examine how doxycycline, a well-known and innocuous antibiotic, can reshape α-synuclein oligomers into non-toxic high-molecular-weight species with decreased ability to destabilize biological membranes, affect cell viability and form additional toxic species. This mechanism can be exploited to diminish the toxicity of α-synuclein oligomers in Parkinson's disease. Second, we discuss a novel function in proteostasis for extracellular glyceraldehyde 3-phosphate dehydrogenase (GAPDH) in combination with a specific glycosaminoglycan (GAG) present in the extracellular matrix. GAPDH, by changing its quaternary structure from a tetramer to protofibrillar assembly, can kidnap toxic species of α-synuclein, and thereby interfere with the spreading of the disease. Finally, we review a brighter side of protein aggregation, that of exploiting the physicochemical advantages of amyloid aggregates as nanomaterials. For this, we designed a new generation of insoluble biocatalysts based on the binding of photo-immobilized enzymes onto hybrid protein:GAG amyloid nanofibrils. These new nanomaterials can be easily functionalized by attaching different enzymes through dityrosine covalent bonds.