Peptide Self-assembly: From Ordered to Disordered.

Biomolecular self-assembly is a ubiquitous occurrence in nature that gives rise to sophisticated superstructures that enable the implementation of complex biological functions. It encompasses both ordered structures, such as the DNA double helix, and disordered structures, such as the nucleolus and other nonmembranous organelles. In contrast to these highly organized ordered structures, which exhibit specific patterns or symmetry, disordered structures are characterized by their flexible and randomized molecular organization, which provides versatility, dynamicity, and adaptability to biological systems and contributes to the complexity and functionality of living organisms. However, these disordered structures usually exist in a thermodynamically metastable state. This means that these disordered structures are unstable and difficult to observe due to their short existence time. Achieving disordered structures through precise control of the assembly process and ensuring their stability and integrity pose significant challenges. Currently, ongoing research efforts are focused on the self-assembly of proteins with intrinsically disordered regions (IDRs). However, the structural complexity and instability of proteins present prohibitive difficulties in elucidating the multiscale self-assembly process. Therefore, simple peptides, as a segment of proteins, hold great promise in constructing self-assembly systems for related research. Since our finding on droplet-like disordered structures that occur transiently during the peptide self-assembly (PSA), our research is centered around the dynamic evolution of peptide supramolecular systems, particularly the modulation of a variety of assembled structures ranging from ordered to disordered.In this Account, we narrate our recent research endeavors on supramolecular structures formed by PSA, spanning from ordered structures to disordered structures. We delve into the mechanisms of structural regulation, shedding light on how these peptide-based structures can be controlled more precisely. Moreover, we emphasize the functional applications that arise from these structures. To begin, we conduct a comprehensive overview of various types of ordered structures that emerge from PSA, showcasing their diverse applications. Following, we elaborate on the discovery and development of droplet-like disordered structures that arise during PSA. A mechanistic study on multistep self-assembly processes mediated by liquid-liquid phase separation (LLPS) is critically emphasized. Ordered structures with different morphologies and functions can be obtained by subtly controlling and adjusting the metastable liquid droplets. In particular, we have recently developed solid glasses with long-range disorder, including noncovalent biomolecular glass based on amino acid and peptide derivatives, as well as high-entropy glass based on cyclic peptides. This demonstrates the great potential of using biologically derived molecules to create green and sustainable glassy materials.

Spatiotemporal-Dependent Confinement Effect of Bubble Swarms Enables a Fractal Hierarchical Assembly with Promoted Chirality.

The submarine-confined bubble swarm is considered an important constraining environment for the early evolution of living matter due to the abundant gas/water interfaces it provides. Similarly, the spatiotemporal characteristics of the confinement effect in this particular scenario may also impact the origin, transfer, and amplification of chirality in organisms. Here, we explore the confinement effect on the chiral hierarchical assembly of the amphiphiles in the confined bubble array stabilized by the micropillar templates. Compared with the other confinement conditions, the assembly in the bubble scenario yields a fractal morphology and exhibits a unique level of the chiral degree, ordering, and orientation consistency, which can be attributed to the characteristic interfacial effects of the rapidly formed gas/water interfaces. Thus, molecules with a balanced amphiphilicity can be more favorable for the promotion. Not limited to the pure enantiomers, chiral amplification of the enantiomer-mixed assembly is observed only in the bubble scenario. Beyond the interfacial mechanism, the fast formation kinetics of the confined liquid bridges in the bubble scenario endows the assembly with the tunable hierarchical morphology when regulating the amphiphilicity, aggregates, and confined spaces. Furthermore, the chiral-induced spin selectivity (CISS) effect of the fractal hierarchical assembly was systematically investigated, and a strategy based on photoisomerization was developed to efficiently modulate the CISS effect. This work provides insights into the robustness of confined bubble swarms in promoting a chiral hierarchical assembly and the potential applications of the resulting chiral hierarchical patterns in solid-state spintronic and optical devices.

Effective Treatment of Helicobacter pylori Infection Using Supramolecular Antimicrobial Peptide Hydrogels.

Helicobacter pylori can cause various gastric conditions including stomach cancer in an acidic environment. Although early H. pylori infections can be treated by antibiotics, prolonged antibiotic administrations may lead to the development of antimicrobial resistance, compromising the effectiveness of the treatments. Antimicrobial peptides (AMPs) have been reported to possess unique advantages against antimicrobial-resistant bacteria due to their rapid physical membrane disruptions and anti-inflammation/immunoregulation properties. Herein, we have developed an AMP hydrogel, which can be orally administered for the treatment of H. pylori infection. The hydrogel has potent antimicrobial activity against H. pylori, achieving bacterial eradication within minutes of action. Compared with the AMP solution, the hydrogel formulation significantly reduced the cytotoxicity and enhanced proteolytic stability. In vivo experiments suggested that the hydrogel formed at pH 4 had superior therapeutic effects to those at pH 7 and 10 hydrogels, attributed to its rapid release and bactericidal action within the acidic stomach environment. Compared to conventional antibiotic treatments, the AMP hydrogel had the advantages of fast bacterial killing in the gastric juice and obviated proton pump inhibitors during the treatment. Although both the AMP hydrogel and antibiotics suppressed the expression of pro-inflammatory cytokines, the former uniquely promoted inflammation resolution. These results indicate that the AMP hydrogels with effectiveness and biosafety may be potential candidates for the clinical treatment of H. pylori infections.

Functional chromopeptide nanoarchitectonics: molecular design, self-assembly and biological applications.

Chromoproteins are a class of delicate natural compounds that elegantly complex photosensitive species with proteins and play a central role in important life processes, such as photosynthesis. Inspired by chromoproteins, researchers integrate simple peptides and photosensitive molecular motifs to generate chromopeptides. Compared with chromoproteins, chromopeptides exhibit a relatively simple molecular structure, flexible and adjustable photophysical properties, and a capability of programmable self-assembly. Chromopeptide self-assembly has attracted great attention as the resultant high-level architectures exhibit an ingenious combination of photofunctions and biofunctions. This review systematically summarizes recent advances in chromopeptide nanoarchitectonics with particular focus on the design strategy, assembly mechanism, and structure-function relationship. Among them, the effect of peptide sequences and the variation in photophysical performance are critically emphasized. On this basis, various applications, including biomedicine and artificial photosynthesis, are discussed together with the future prospects of chromopeptide nanoarchitectonics. This review will provide insights into chromopeptide nanoarchitectonics and corresponding materials with precise designs, flexible nanostructures and versatile functions. In addition, knowledge involving chromopeptide nanoarchitectonics may aid in the development of many other kinds of supramolecular biological materials and bioengineering techniques.

Supramolecular Nanoarchitectonics Based on Antagonist Peptide Self-Assembly for Treatment of Liver Fibrosis.

Therapeutic peptides have attracted increasing attention as anti-fibrotic drug candidates. However, the rapid degradation and insufficient liver accumulation of therapeutic peptides have seriously hampered their clinical translation. Here, the use of supramolecular nanoarchitectonics is reported to fabricate nanodrugs from therapeutic peptides for treating liver fibrosis. Self-assembling antagonist peptides are rationally designed and manipulated into uniform peptide nanoparticles with well-defined nanostructures and uniform sizes. Significantly, the peptide nanoparticles show enhanced accumulation in liver sites and limited distribution in other tissues. In vivo results show that the peptide nanoparticles exhibit greatly enhanced anti-fibrotic activity compared to the pristine antagonist along with good biocompatibility. These results indicate that self-assembly is a promising nanoarchitectonics approach to enhance the anti-fibrotic activity of therapeutic peptides for treating liver fibrosis.

Molecular Engineering of Ordered Piezoelectric Sulfonic Acid-Containing Assemblies.

Sulfonic acid-containing bioorganic monomers with wide molecular designability and abundant hydrogen bonding sites hold great potential to design diverse functional biocrystals but have so far not been explored for piezoelectric energy harvesting applications due to the lack of strategies to break the centrosymmetry of their assemblies. Here, a significant molecular packing transformation from centrosymmetric into non-centrosymmetric conformation by the addition of an amide terminus in the sulfonic acid-containing bioorganic molecule is demonstrated, allowing a high electromechanical response. The amide-functionalized molecule self-assembles into a polar supramolecular parallel ß-sheet-like structure with a high longitudinal piezoelectric coefficient d11 = 15.9 pm V-1 that produces the maximal open-circuit voltage of >1 V and the maximal power of 18 nW in nanogenerator devices pioneered. By contrast, molecules containing an amino or a cyclohexyl terminus assemble into highly symmetric 3D hydrogen bonding diamondoid-like networks or 2D double layer structures that show tunable morphologies, thermostability, and mechanical properties but non-piezoelectricity. This work not only presents a facile approach to achieving symmetry transformation of bioorganic assemblies but also demonstrates the terminal group and the property correlation for tailor-made design of high-performance piezoelectric biomaterials.

Biosynthesis of Multifunctional Transformable Peptides for Inducing Tumor Cell Apoptosis.

Engineered nanomaterials hold great promise to improve the specificity of disease treatment. Herein, a fully protein-based material is obtained from nonpathogenic Escherichia coli (E. coli), which is capable of morphological transformation from globular to fibrous in situ for inducing tumor cell apoptosis. The protein-based material P1 is comprised of a ß-sheet-forming peptide KLVFF, pro-apoptotic protein BAK, and GFP along with targeting moieties. The self-assembled nanoparticles of P1 transform into nanofibers in situ in the presence of cathepsin B, and the generated nanofibrils favor the dimerization of functional BH3 domain of BAK on the mitochondrial outer membrane, leading to efficient anticancer activity both in vitro and in vivo via mitochondria-dependent apoptosis through Bcl-2 pathway. To precisely manipulate the morphological transformation of biosynthetic molecules in living cells, a spatiotemporally controllable anticancer system is constructed by coating P1-expressing E. coli with cationic conjugated polyelectrolytes to release the peptides in situ under light irradiation. The biosynthetic peptide-based enzyme-catalytic transformation strategy in vivo would offer a novel perspective for targeted delivery and shows great potential in precision disease therapeutics.

Phthalocyanine-Triggered Helical Dipeptide Nanotubes with Intense Circularly Polarized Luminescence.

Nanotubes with circularly polarized luminescence (CPL) are attracting much attention due to many potential applications, such as chiroptical materials, displays, and sensing. However, it remains a challenge to change the assemblies of ordinarily molecular building blocks into CPL supramolecular nanotubes. Herein, the regulation of quite common dipeptide (Fmoc-FF) assemblies into unprecedented helical nanotubes exhibiting intense CPL is reported by simply doping a few phthalocyanine (octakis(carboxyl)phthalocyaninato zinc complex (Pc)) molecules. Interestingly, altering the Fmoc-FF/Pc molar ratios over a wide range cannot change the nanotubes structures according to transmission electron microscopy (TEM) and atomic force microscope (AFM) measurements. Although molecular dynamics simulations suggest that the noncovalent interactions between Fmoc-FF and Pc are quite weak, few Pc molecules can still change the secondary structures of a large number of Fmoc-FF assemblies, which hierarchically form helical supramolecular nanotubes with long-range ordered molecular packing, leading to intense CPL signals with large luminescence dissymmetry factor (glum  = 0.04). Consequently, the chiral reorganization of Fmoc-FF assemblies is dependent on the coassembly between Pc molecule and Fmoc-FF supramolecular architectures. These results open the possibility for the fine-tuning of helix and supramolecular nanotubes with CPL properties by using a small number of cofactors.

Schiff Base Mediated Dipeptide Assembly toward Nanoarchitectonics.

Dynamic covalent chemistry (DCC) is fascinating because of its dual nature. It perfectly combines the reversible nature of noncovalent bonds with the robustness of covalent bonds, effectively enhancing the stability of assemblies and meanwhile giving rise to unprecedented properties. Therefore, integration of DCC with supramolecular chemistry has emerged as a versatile and an extraordinarily useful approach in directing peptide assembly. This Minireview focuses on a recent strategy, which exploits dynamic Schiff base chemistry in combination with supramolecular chemistry, to mediate dipeptide assembly toward nanoarchitectonics. Diversified structures, new emergent properties, and their related applications are highlighted. Lastly, the opportunities and prospects in this exciting field are also introduced.

Biomimetic Nanozymes Based on Coassembly of Amino Acid and Hemin for Catalytic Oxidation and Sensing of Biomolecules.

Nanoassemblies based on self-assembly of biological building blocks are promising in mimicking the nanostructures, properties, and functionalities of natural enzymes. However, it remains a challenge to design of biomimetic nanozymes with tunable nanostructures and enhanced catalytic activities starting from simple biomolecules. Herein, the construction of nanoassemblies through coassembly of an amphiphilic amino acid and hemin is reported. The nanostructures and morphologies of the resulting nanoassemblies are readily controlled by tuning the molar ratio between the amino acid and hemin, thus leading to tailored peroxidase-mimicking activities of the nanoassemblies. Importantly, the optimized nanoassemblies exhibit a remarkable catalytic efficiency that is comparable to the natural counterpart when considering molecular mass along with good robustness in multiple catalytic cycles. The nanoassemblies are effectively integrated as biomimetic nanozymes in a sensing system for catalytic detection of glucose. Therefore, this work demonstrates that nanozymes with advanced catalytic capabilities can be constructed by self-assembly of minimalist biological building blocks and may thus promote the rational design and catalytic applications of biomimetic nanozymes.

A Bubble-Assisted Approach for Patterning Nanoscale Molecular Aggregates.

We demonstrate a new approach to pattern functional organic molecules with a template of foams, and achieve a resolution of sub 100 nm. The bubble-assisted assembly (BAA) process is consisted of two periods, including bubble evolution and molecular assembly, which are dominated by the Laplace pressure and molecular interactions, respectively. Using TPPS (meso-tetra(4-sulfonatophenyl) porphyrin), we systematically investigate the patterns and assembly behaviour in the bubble system with a series of characterizations, which show good uniformity in nanoscale resolution. Theoretical simulations reveal that TPPS's J-aggregates contribute to the ordered construction of molecular patterns. Finally, we propose an empirical rule for molecular patterning approach, that the surfactant and functional molecules should have the same type of charge in a two-component system. This approach exhibits promising feasibility to assemble molecular patterns at nanoscale resolution for micro/nano functional devices.

Multifunctional Antimicrobial Biometallohydrogels Based on Amino Acid Coordinated Self-Assembly.

There is a real need for new antibiotics against self-evolving bacteria. One option is to use biofriendly broad-spectrum and mechanically tunable antimicrobial hydrogels that can combat multidrug-resistant microbes. Whilst appealing, there are currently limited options. Herein, broad-spectrum antimicrobial biometallohydrogels based on the self-assembly and local mineralization of Ag+ -coordinated Fmoc-amino acids are reported. Such biometallohydrogels have the advantages of localized delivery and sustained release, reduced drug dosage and toxicity yet improved bioavailability, prolonged drug effect, and tunable mechanical strength. Furthermore, they can directly interact with the cell walls and membrane, resulting in the detachment of the plasma membrane and leakage of the cytoplasm. This leads to cell death, triggering a significant antibacterial effect against both Gram-negative (Escherichia coli) and Gram-positive (Staphylococcus aureus) bacteria in cells and mice. This study paves the way for developing a multifunctional integration platform based on simple biomolecules coordinated self-assembly toward a broad range of biomedical applications.

Photoactive properties of supramolecular assembled short peptides.

Bioinspired nanostructures can be the ideal functional smart materials to bridge the fundamental biology, biomedicine and nanobiotechnology fields. Among them, short peptides are among the most preferred building blocks as they can self-assemble to form versatile supramolecular architectures displaying unique physical and chemical properties, including intriguing optical features. Herein, we discuss the progress made over the past few decades in the design and characterization of optical short peptide nanomaterials, focusing on their intrinsic photoluminescent and waveguiding performances, along with the diverse modulation strategies. We review the complicated optical properties and the advanced applications of photoactive short peptide self-assemblies, including photocatalysis, as well as photothermal and photodynamic therapy. The diverse advantages of photoactive short peptide self-assemblies, such as eco-friendliness, morphological and functional flexibility, and ease of preparation and modification, endow them with the capability to potentially serve as next-generation, bio-organic optical materials, allowing the bridging of the optics world and the nanobiotechnology field.

Porphyrin/Ionic-Liquid Co-assembly Polymorphism Controlled by Liquid-Liquid Phase Separation.

Understanding and controlling multicomponent co-assembly is of primary importance in different fields, such as materials fabrication, pharmaceutical polymorphism, and supramolecular polymerization, but these aspects have been a long-standing challenge. Herein, we discover that liquid-liquid phase separation (LLPS) into ion-cluster-rich and ion-cluster-poor liquid phases is the first step prior to co-assembly nucleation based on a model system of water-soluble porphyrin and ionic liquids. The LLPS-formed droplets serve as the nucleation precursors, which determine the resulting structures and properties of co-assemblies. Co-assembly polymorphism and tunable supramolecular phase transition behaviors can be achieved by regulating the intermolecular interactions at the LLPS stage. These findings elucidate the key role of LLPS in multicomponent co-assembly evolution and enable it to be an effective strategy to control co-assembly polymorphism as well as supramolecular phase transitions.

Supramolecular Photothermal Effects: A Promising Mechanism for Efficient Thermal Conversion.

Supramolecular assemblies have been very successful in regulating the photothermal conversion efficiency of organic photothermal materials in a simple and flexible way, compared with conventional molecular synthesis. In these assemblies, it is the inherent physiochemical mechanism that determines the photothermal conversion, rather than the assembly strategy. This Minireview summarizes supramolecular photothermal effects, which refer to the unique features of supramolecular chemistry for regulating the photothermal conversion efficiency. Emphasis is placed on the mechanisms of how self-assembly affects the photothermal performance. The supramolecular photothermal effects on various types of light-harvesting species are discussed in detail. The timely interpretation of supramolecular photothermal effects is promising for the future design of the photothermal materials with high efficiency, precision, and multiple functionalities for a wide array of applications.

Ferric Ion Driven Assembly of Catalase-like Supramolecular Photosensitizing Nanozymes for Combating Hypoxic Tumors.

A facile approach to assemble catalase-like photosensitizing nanozymes with a self-oxygen-supplying ability was developed. The process involved Fe3+ -driven self-assembly of fluorenylmethyloxycarbonyl (Fmoc)-protected amino acids. By adding a zinc(II) phthalocyanine-based photosensitizer (ZnPc) and the hypoxia-inducible factor 1 (HIF-1) inhibitor acriflavine (ACF) during the Fe3+ -promoted self-assembly of Fmoc-protected cysteine (Fmoc-Cys), the nanovesicles Fmoc-Cys/Fe@Pc and Fmoc-Cys/Fe@Pc/ACF were prepared, which could be disassembled intracellularly. The released Fe3+ could catalyze the transformation of H2 O2 enriched in cancer cells to oxygen efficiently, thereby ameliorating the hypoxic condition and promoting the photosensitizing activity of the released ZnPc. With an additional therapeutic component, Fmoc-Cys/Fe@Pc/ACF exhibited higher in vitro and in vivo photodynamic activities than Fmoc-Cys/Fe@Pc, demonstrating the synergistic effect of ZnPc and ACF.

Acid-Activatable Transmorphic Peptide-Based Nanomaterials for Photodynamic Therapy.

Inspired by the dynamic morphology control of molecular assemblies in biological systems, we have developed pH-responsive transformable peptide-based nanoparticles for photodynamic therapy (PDT) with prolonged tumor retention times. The self-assembled peptide-porphyrin nanoparticles transformed into nanofibers when exposed to the acidic tumor microenvironment, which was mainly driven by enhanced intermolecular hydrogen bond formation between the protonated molecules. The nanoparticle transformation into fibrils improved their singlet oxygen generation ability and enabled high accumulation and long-term retention at tumor sites. Strong fluorescent signals of these nanomaterials were detected in tumor tissue up to 7 days after administration. Moreover, the peptide assemblies exhibited excellent anti-tumor efficacy via PDT in vivo. This in situ fibrillar transformation strategy could be utilized to design effective stimuli-responsive biomaterials for long-term imaging and therapy.

Supramolecular Protein Nanodrugs with Coordination- and Heating-Enhanced Photothermal Effects for Antitumor Therapy.

Supramolecular protein nanodrugs provide opportunities for improving antitumor therapeutic efficiency and lowering toxicity. However, protein nanodrugs that have robust structural stability and enhanced therapeutic efficiency are still in infancy. In this study, photothermal protein nanodrugs are constructed through a supramolecular approach along with heating by using proteins, photosensitizers, and metal ions as the building blocks. The metal coordination and heating improve not only the structural stability but also photothermal performance of the resulting nanodrugs. By virtue of the first integration of coordination- and heating-enhanced photothermal effects, the nanodrugs show superior photothermal conversion efficiency, enhanced tumor accumulation, and improved tumor inhibition. Metal coordination and heating are versatile to be applied for various protein nanodrugs. Hence, this study provides insights for the construction of highly efficient photothermal nanodrugs and thus will be beneficial to precision theranostics.

Covalently Assembled Dipeptide Nanoparticles with Adjustable Fluorescence Emission for Multicolor Bioimaging.

Peptide self-assembly, inspired by the naturally occurring fabrication principle, remains the most attractive in constructing fluorescent nanoagents towards bioimaging. However, the noncovalent interactions that drive peptide self-assembly are usually susceptible to the complex physiological environment; thus leading to disassembly and dysfunction of fluorescent nanoagents. Herein, a covalently crosslinked assembly strategy for fabrication of stable peptide-based nanoparticles with adjustable emission is introduced. In the process of cationic diphenylalanine peptide (H-Phe-Phe-NH2 ⋅HCl) self-assembly, glutaraldehyde is used as a crosslinker and the resulting product of the Schiff base reaction can be fluorescent. More importantly, the emission wavelength can be readily tuned by controlling the covalent reaction time. It has been demonstrated that the nanoparticles are stable, even after intracellular uptake, and can be used for sustainable multicolor fluorescent imaging. The strategy with integrating peptide self-assembly and covalent crosslinking could be promising for the design and engineering of functional fluorescent nanoparticles with robust physiological stability and adjustable emission towards improved bioimaging applications.

Spatiotemporally Coupled Photoactivity of Phthalocyanine-Peptide Conjugate Self-Assemblies for Adaptive Tumor Theranostics.

Spatiotemporally coupled tumor phototheranostic platforms offer a flexible and precise system that takes the biological interaction between tumors and photoactive agents into consideration for optimizing treatment, which is highly consistent with precision medicine. However, the fabrication of monocomponent-based photoactive agents applicable to multifold imaging techniques and multiple therapies in a facile way remains challenging. In this study, we developed simple phthalocyanine-peptide (PF) conjugate-based monocomponent nanoparticles with spatiotemporally coupled photoactivity for adaptive tumor theranostics. The self-assembled PF nanoparticles possess well-defined spherical nanostructures and excellent colloidal stability along with supramolecular photothermal effects. Importantly, the PF nanoparticles showed switchable photoactivity triggered by their interactions with the cell membrane, which enables an adaptive transformation from photothermal therapy (PTT) and photoacoustic imaging (PAI) to photodynamic therapy (PDT) and corresponding fluorescence imaging (FI). Theranostic modalities are integrated in a spatiotemporally coupled manner, providing a facile, biocompatible and effective route for localized tumor phototherapy. This study offers a flexible and versatile strategy to integrate multiple theranostic modalities into a single component so that it can realize its full potential and thereby amplify its therapeutic efficacy, creating promising opportunities for the design of theranostics and further highlighting their clinical prospects to the diagnosis and treatment of cancers.