Water-Floating Giant Nanosheets from Helical Peptide Pentamers

A TLR4-Targeting Bioactive Peptide Hydrogel to Regulate Immune-Microenvironment for Diabetic Wound Repair

Persistent inflammation and disrupted immunoregulation are critical factors in impeding diabetic wound healing. While immunoregulatory hydrogel dressings hold significant promise for clinical applications in diabetic wound healing, the current application often demands intricate interventions and high-cost treatments involving cytokines and cell therapies. The development of single component immunoregulatory hydrogels remains a complex challenge. To address this issue, an active peptide hydrogel with immunoregulatory properties targeting the TLR4/NF-kB pathway, aiming to promote rapid diabetic wound healing, is engineered. The hydrogel sequence comprises naphthalene derivative, phenylalanine, and glycine to modulate hydrophilic/hydrophobic characteristics. The amino group on arginine contributes to tissue adhesion and regulation of intermolecular forces, ultimately yielding stable gels. The results underscore the formation of the peptide hydrogel (NFA) via the physical crosslinking of self-assembled nanofibers in water, thereby affording both excellent injectability and tissue adhesion. Notably, NFA demonstrates significant potential in promoting wound healing in a mouse model with full-thickness wounds by regulating macrophage responses in the inflammatory microenvironment through the TLR4/NF-kB pathway.

Small Peptide-Based Nanodelivery Systems for Cancer Therapy and Diagnosis

Developing nano-biomaterials with tunable topology, size, and surface characteristics has shown tremendously favorable benefits in various biologic and clinical applications. Among various nano-biomaterials, peptide-based drug delivery systems offer multiple merits over other synthetic systems due to their enhanced bio- and cytocompatibility and desirable biochemical and biophysical properties. Currently, around 100 peptide-based drugs are clinically available for numerous therapeutic purposes. In conjugation with chemotherapeutic moieties, peptides demonstrate a remarkable ability to reduce nonspecific drug effects by improving drug targetability at cancer sites. This review encompasses a wide-ranging role played by different peptide-based nanostructures in cancer theranostics. Section 1 introduces the rising concern about cancer as a disease and further describes peptide-based nanomaterials as biomedical agents to tackle the ailment. The subsequent section explores the mechanistic pathways behind the self-assembly of peptides to form hierarchically distinct assemblies. The crux of our review lies in an exhaustive exploration of the applications of various types of peptide-based nanostructures in cancer therapy and diagnosis. SIGNIFICANCE STATEMENT: Peptide-based drug delivery systems possess superior biocompatibility, biochemical, and biophysical properties compared to other synthetic alternatives. The development of these nano-biomaterials with customizable topology, size, and surface characteristics have shown promising outcomes in biomedical contexts. Peptides in conjunction with chemotherapeutic agents exhibit the ability to enhance drug targetability at cancer sites, reducing nonspecific drug effects. This comprehensive review emphasizes the pivotal role of diverse peptide-based nanostructures as cancer theranostics, elucidating their potential in revolutionizing cancer therapy and diagnosis.

Controlling the Assembly of Cellulose-Based Oligosaccharides through Sequence Modifications

Peptides and nucleic acids with programmable sequences are widely explored for the production of tunable, self-assembling functional materials. Herein we demonstrate that the primary sequence of oligosaccharides can be designed to access materials with tunable shapes and properties. Synthetic cellulose-based oligomers were assembled into 2D or 3D rod-like crystallites. Sequence modifications within the oligosaccharide core influenced the molecular packing and led to the formation of square-like assemblies based on the rare cellulose IVII allomorph. In contrast, modifications at the termini generated elongated aggregates with tunable surfaces, resulting in self-healing supramolecular hydrogels.

Photochemical synthesis of pink silver and its use for monitoring peptide nitration via surface enhanced Raman spectroscopy (SERS)

Oxidative stress may cause extended tyrosine posttranslational modifications of peptides and proteins. The 3-nitro-L-tyrosine (Nit), which is typically formed, affects protein behavior during neurodegenerative processes, such as Alzheimer's and Parkinson's diseases. Such metabolic products may be conveniently detected at very low concentrations by surface enhanced Raman spectroscopy (SERS). Previously, we have explored the SERS detection of the Nit NO₂ bending vibrational bands in a presence of hydrogen chloride (Niederhafner et al., Amino Acids 53:517-532, 2021, ibid). In this article, we describe performance of a new SERS substrate, "pink silver", synthesized photochemically. It provides SERS even without the HCl induction, and the acid further decreases the detection limit about 9 times. Strong SERS bands were observed in the asymmetric (1550-1475 cm^-1) and symmetric (1360-1290 cm^-1) NO stretching in the NO₂ group. The bending vibration was relatively weak, but appeared stronger when HCl was added. The band assignments were supported by density functional theory modeling.

Peptide Design and Self-assembly into Targeted Nanostructure and Functional Materials

Peptides have been extensively utilized to construct nanomaterials that display targeted structure through hierarchical assembly. The self-assembly of both rationally designed peptides derived from naturally occurring domains in proteins as well as intuitively or computationally designed peptides that form β-sheets and helical secondary structures have been widely successful in constructing nanoscale morphologies with well-defined 1-d, 2-d, and 3-d architectures. In this review, we discuss these successes of peptide self-assembly, especially in the context of designing hierarchical materials. In particular, we emphasize the differences in the level of peptide design as an indicator of complexity within the targeted self-assembled materials and highlight future avenues for scientific and technological advances in this field.

Intravenous Delivery of Lung-Targeted Nanofibers for Pulmonary Hypertension in Mice

Pulmonary hypertension is a highly morbid disease with no cure. Available treatments are limited by systemic adverse effects due to non-specific biodistribution. Self-assembled peptide amphiphile (PA) nanofibers are biocompatible nanomaterials that can be modified to recognize specific biological markers to provide targeted drug delivery and reduce off-target toxicity. Here, PA nanofibers that target the angiotensin I-converting enzyme and the receptor for advanced glycation end-products (RAGE) are developed, as both proteins are overexpressed in the lung with pulmonary hypertension. It is demonstrated that intravenous delivery of RAGE-targeted nanofibers containing the targeting epitope LVFFAED (LVFF) significantly accumulated within the lung in a chronic hypoxia-induced pulmonary hypertension mouse model. Using 3D light sheet fluorescence microscopy, it is shown that LVFF nanofiber localization is specific to the diseased pulmonary tissue with immunofluorescence analysis demonstrating colocalization of the targeted nanofiber to RAGE in the hypoxic lung. Furthermore, biodistribution studies show that significantly more LVFF nanofibers localized to the lung compared to major off-target organs. Targeted nanofibers are retained within the pulmonary tissue for 24 h after injection. Collectively, these data demonstrate the potential of a RAGE-targeted nanomaterial as a drug delivery platform to treat pulmonary hypertension.

Recent Progress in the Design and Medical Application of In Situ Self-Assembled Polypeptide Materials

Inspired by molecular self-assembly, which is ubiquitous in natural environments and biological systems, self-assembled peptides have become a research hotspot in the biomedical field due to their inherent biocompatibility and biodegradability, properties that are afforded by the amide linkages forming the peptide backbone. This review summarizes the biological advantages, principles, and design strategies of self-assembled polypeptide systems. We then focus on the latest advances in in situ self-assembly of polypeptides in medical applications, such as oncotherapy, materials science, regenerative medicine, and drug delivery, and then briefly discuss their potential challenges in clinical treatment.

Molecular design of stapled pentapeptides as building blocks of self-assembled coiled coil-like fibers

Peptide self-assembly inspired by natural superhelical coiled coils has been actively pursued but remains challenging due to limited helicity of short peptides. Side chain stapling can strengthen short helices but is unexplored in design of self-assembled helical nanofibers as it is unknown how staples could be adapted to coiled coil architecture. Here, we demonstrate the feasibility of this design for pentapeptides using a computational method capable of predicting helicity and fiber-forming tendency of stapled peptides containing noncoded amino acids. Experiments showed that the best candidates, which carried an aromatically substituted staple and phenylalanine analogs, displayed exceptional helicity and assembled into nanofibers via specific head-to-tail hydrogen bonding and packing between staple and noncoded side chains. The fibers exhibited sheet-of-helix structures resembling the recently found collapsed coiled coils whose formation was sensitive to side chain flexibility. This study expands the chemical space of coiled coil assemblies and provides guidance for their design.

Coassembly Generates Peptide Hydrogel with Wound Dressing Material Properties

Multicomponent self-assembly of peptides is a powerful strategy to fabricate novel functional materials with synergetic properties that can be used for several nanobiotechnological applications. In the present study, we used a coassembly strategy to generate an injectable ultrashort bioactive peptide hydrogel formed by mixing a dipeptide hydrogelator with a macrophage attracting short chemotactic peptide ligand. Coassembly does not impede hydrogelation as shown by cryo-transmission electron microscopy (cryo-TEM), scanning electron microscopy, and rheology. Biocompatibility was shown by cytotoxicity assays and confocal microscopy. The hydrogels release the entrapped skin antibiotic ciprofloxacin, among others, in a slow and continuous manner. Such bioinspired advanced functional materials can find applications as wound dressing materials to treat chronic wound conditions like diabetic foot ulcer.

Bioinspired Toolkit Based on Intermolecular Encoder toward Evolutionary 4D Chiral Plasmonic Materials

Over the last two decades, nanophotonics, including plasmonics and metamaterials, have promised compelling opportunities for exotic control over light-matter interactions. The strong chiral light-matter interaction is a representative example. Three-dimensional (3D) chirality has existed naturally only in organic molecules and bio-organisms, but a negligible chiroptic effect was attained with these naturally occurring materials because of their small absorption cross sections. However, inspired by biological chirality, nanophotonic chiral materials have greatly expanded the design space of accessible chiroptic effects (e.g., pushing the chiral light-matter interaction to an exceptional regime, such as a broad-band circular polarizer, negative refractive index, and sensitive chiral sensing). Nevertheless, it is still a challenge to achieve precisely defined and dynamically reconfigurable chiral morphologies that further increase the chiroptic effect. Biological systems continue to inspire approaches to the design and synthesis of precisely defined 3D nanostructures. In particular, a living organism can program the evolutionary pathway of highly complexed 3D chiral morphology precisely from the molecular scale to the macroscopic scale while simultaneously enabling dynamic reconfiguration of their chirality. What if we could harness the power of biological selectivity and evolutionary capability in synthesizing chiral plasmonic materials? We envisioned that platform technology mimicking biological principles would enable control of 3D chiral structures for effective plasmonic interactions with polarized light and further impart the concept of time-dependent evolution (3D + 1D = 4D) to bring about responsive and dynamic changes in chiral plasmonics. In this Account, we review our efforts to develop the biomolecule-based synthesis of 3D chiral plasmonic materials and share the vision that as in biological systems, chirality can be programmed at the molecular level and hierarchically transferred at multiple scales to develop macroscopic chirality. Accompanied by a biomimetic time-dependent chirality of singular plasmonic nanometals, we also summarize recent achievements in the chemistry and nanophotonics communities pursuing 4D plasmonics that are closely related to our research. The biomimetic and bioinspired approaches discussed in this Account will provide new synthetic insights into implementing chiral nanomaterials and extend the range of accessible nanophotonic design. We hope that the molecular encoding approach will be useful to achieve dynamic light-matter interactions at unprecedented dimensions, time scales, and chirality.

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

The discovery of a general strategy for organizing functional proteins into stable nanostructures with the desired dimension, shape, and function is an important focus in developing protein-based self-assembled materials, but the scalable synthesis of such materials and transfer to other substrates remain great challenges. We herein tackle this issue by creating a two-dimensional metal-protein hybrid nanofilm that is flexible and cost-effective with reliable self-recovery, stability, and multifunctionality. As it differs from traditional metal ions, we discover the capability of Sn²⁺ to initiate fast amyloid-like protein assembly (occurring in seconds) by effectively reducing the disulfide bonds of native globular proteins. The Sn²⁺-initiated lysozyme aggregation at the air/water interface leads to droplet flattening, a result never before reported in a protein system, which finally affords a multifunctional 2D Sn-doped hybrid lysozyme nanofilm with an ultralarge area (e.g., 0.2 m²) within a few minutes. The hybrid film is distinctive in its ease of coating on versatile material surfaces with endurable chemical and mechanical stability, optical transparency, and diverse end uses in antimicrobial and photo-/electrocatalytic scaffolds. Our approach provides not only insights into the effect of tin ions on macroscopic self-assembly of proteins but also a controllable and scalable synthesis of a potential biomimic framework for biomedical and biocatalytic applications.

DNA translocation through a nanopore in an ultrathin self-assembled peptide membrane

Here, we explore the possibility of using peptide-based materials as a membrane in solid-state nanopore devices in an effort to develop a sequence-specific, programmable biological membrane platform. We use a recently developed tyrosine-mediated self-assembly peptide sheet. At the air/water interface, the 5mer peptide YFCFY self-assembles into a uniform and robust two-dimensional (2D) structure, and the peptide sheet is easily transferred to a low-noise glass substrate. The thickness of the peptide membrane can be adjusted to approximately 5 nm (or even to 2 nm) by an etching process, and the diameters of the peptide nanopores can be precisely controlled using a focused electron beam with an attuned spot size. The ionic current noise of the peptide nanopore is comparable to those of typical silicon nitride nanopores or multilayer 2D materials. Using this membrane, we successfully observe translocation of 1000 bp double-stranded DNA with a sufficient signal-to-noise ratio of ∼30 and an elongated translocation speed of ∼1 bp μs^-1. Our results suggest that the self-assembled peptide film can be used as a sensitive nanopore membrane and employed as a platform for applying biological functionalities to solid-state substrates.

Hierarchical nanomaterials via biomolecular self-assembly and bioinspiration for energy and environmental applications

Bioinspired synthesis offers potential green strategies to build highly complex nanomaterials by utilizing the unique nanostructures, functions, and properties of biomolecules, in which the biomolecular recognition and self-assembly processes play important roles in tailoring the structures and functions of bioinspired materials. Further understanding of biomolecular self-assembly for inspiring the formation and assembly of nanoparticles would promote the design and fabrication of functional nanomaterials for various applications. In this review, we focus on recent advances in bioinspired synthesis and applications of hierarchical nanomaterials based on biomolecular self-assembly. We first discuss biomolecular self-assembly towards biological nanomaterials, in which the mechanisms and ways of biomolecular self-assembly as well as various self-assembled biomolecular nanostructures are demonstrated. Secondly, the bioinspired synthesis strategies including molecule-molecule interaction, molecule-material recognition, molecule-mediated nucleation and growth, and molecule-mediated reduction/oxidation are introduced and discussed. Meanwhile, typical examples and discussions on how biomolecular self-assembly inspires the formation of hierarchical hybrid nanomaterials are presented. Finally, the applications of bioinspired nanomaterials in biofuel cells, light-harvesting systems, batteries, supercapacitors, catalysis, water/air purification, and environmental monitoring are presented and discussed. We believe that this review will be very helpful for readers to understand the self-assembly of biomolecules and the biomimetic/bioinspired strategies for synthesizing hierarchical nanomaterials on the one hand, and on the other hand to design novel materials for extended applications in nanotechnology, materials science, analytical science, and biomedical engineering.

Tyrosine-Rich Peptides as a Platform for Assembly and Material Synthesis

The self-assembly of biomolecules can provide a new approach for the design of functional systems with a diverse range of hierarchical nanoarchitectures and atomically defined structures. In this regard, peptides, particularly short peptides, are attractive building blocks because of their ease of establishing structure-property relationships, their productive synthesis, and the possibility of their hybridization with other motifs. Several assembling peptides, such as ionic-complementary peptides, cyclic peptides, peptide amphiphiles, the Fmoc-peptide, and aromatic dipeptides, are widely studied. Recently, studies on material synthesis and the application of tyrosine-rich short peptide-based systems have demonstrated that tyrosine units serve as not only excellent assembly motifs but also multifunctional templates. Tyrosine has a phenolic functional group that contributes to π-π interactions for conformation control and efficient charge transport by proton-coupled electron-transfer reactions in natural systems. Here, the critical roles of the tyrosine motif with respect to its electrochemical, chemical, and structural properties are discussed and recent discoveries and advances made in tyrosine-rich short peptide systems from self-assembled structures to peptide/inorganic hybrid materials are highlighted. A brief account of the opportunities in design optimization and the applications of tyrosine peptide-based biomimetic materials is included.

The design and biomedical applications of self-assembled two-dimensional organic biomaterials

Self-assembling 2D organic biomaterials exhibit versatile abilities for structural and functional tailoring, as well as high potential for biomedical applications.

Self-assembly of Functional Nanostructures by Short Helical Peptide Building Blocks

The self-assembly of short peptide building blocks into well-ordered nanostructures is a key direction in bionanotechnology. The formation of β -sheet organizations by short peptides is well explored, leading to the development of a wide range of functional assemblies. Likewise, many natural proteinaceous materials, such as silk and amyloid fibrils, are based on β-sheet structures. In contrast, collagen, the most abundant protein in mammals, is based on helical arrangement. Similar to β-sheet structures, short helical peptides have been recently discovered to possess a diverse set of functionalities with the potential to fabricate artificial self-assembling materials. Here, we outline the functional roles of self-assembled nanostructures formed by short helical peptides and their potential as artificial materials. We focus on the association between self-assembled mesoscale structures and their material function and demonstrate the way by which this class of building blocks bears the potential for diverse applications, such as the future fabrication of smart devices.

Multicomponent peptide assemblies

Self-assembled peptide nanostructures have been increasingly exploited as functional materials for applications in biomedicine and energy. The emergent properties of these nanomaterials determine the applications for which they can be exploited. It has recently been appreciated that nanomaterials composed of multicomponent coassembled peptides often display unique emergent properties that have the potential to dramatically expand the functional utility of peptide-based materials. This review presents recent efforts in the development of multicomponent peptide assemblies. The discussion includes multicomponent assemblies derived from short low molecular weight peptides, peptide amphiphiles, coiled coil peptides, collagen, and β-sheet peptides. The design, structure, emergent properties, and applications for these multicomponent assemblies are presented in order to illustrate the potential of these formulations as sophisticated next-generation bio-inspired materials.

Tuning peptide self-assembly by an in-tether chiral center

The self-assembly of peptides into ordered nanostructures is important for understanding both peptide molecular interactions and nanotechnological applications. However, because of the complexity and various self-assembling pathways of peptide molecules, design of self-assembling helical peptides with high controllability and tunability is challenging. We report a new self-assembling mode that uses in-tether chiral center-induced helical peptides as a platform for tunable peptide self-assembly with good controllability. It was found that self-assembling behavior was governed by in-tether substitutional groups, where chirality determined the formation of helical structures and aromaticity provided the driving force for self-assembly. Both factors were essential for peptide self-assembly to occur. Experiments and theoretical calculations indicate long-range crystal-like packing in the self-assembly, which was stabilized by a synergy of interpeptide π-π and π-sulfur interactions and hydrogen bond networks. In addition, the self-assembled peptide nanomaterials were demonstrated to be promising candidate materials for applications in biocompatible electrochemical supercapacitors.

Molecular co-assembly as a strategy for synergistic improvement of the mechanical properties of hydrogels

Molecular self-assembly is a key direction for the fabrication of advanced materials. Yet, the physical properties of the formed assemblies are limited by the inherent characteristics of the specific building blocks. Here, we have applied a co-assembly approach to synergistically modulate the mechanical properties of peptide hydrogels, thereby forming extremely stable and rigid hydrogels.

Flat Drops, Elastic Sheets, and Microcapsules by Interfacial Assembly of a Bacterial Biofilm Protein, BslA

Protein adsorption and assembly at interfaces provide a potentially versatile route to create useful constructs for fluid compartmentalization. In this context, we consider the interfacial assembly of a bacterial biofilm protein, BslA, at air-water and oil-water interfaces. Densely packed, high modulus monolayers form at air-water interfaces, leading to the formation of flattened sessile water drops. BslA forms elastic sheets at oil-water interfaces, leading to the production of stable monodisperse oil-in-water microcapsules. By contrast, water-in-oil microcapsules are unstable but display arrested rather than full coalescence on contact. The disparity in stability likely originates from a low areal density of BslA hydrophobic caps on the exterior surface of water-in-oil microcapsules, relative to the inverse case. In direct analogy with small molecule surfactants, the lack of stability of individual water-in-oil microcapsules is consistent with the large value of the hydrophilic-lipophilic balance (HLB number) calculated based on the BslA crystal structure. The occurrence of arrested coalescence indicates that the surface activity of BslA is similar to that of colloidal particles that produce Pickering emulsions, with the stability of partially coalesced structures ensured by interfacial jamming. Micropipette aspiration and flow in tapered capillaries experiments reveal intriguing reversible and nonreversible modes of mechanical deformation, respectively. The mechanical robustness of the microcapsules and the ability to engineer their shape and to design highly specific binding responses through protein engineering suggest that these microcapsules may be useful for biomedical applications.

Homogenous graphene oxide-peptide nanofiber hybrid hydrogel as biomimetic polysaccharide hydrolase

Cellulose, an impressive potential sustainable fuel, is difficult to hydrolyze because of the protection of β-1,4-glycosidic bonds through the tight hydrogen bonding network. In this study, homogenous graphene oxide (GO)-peptide nanofiber hybrid hydrogels (GO-PNFs) were designed as a β-glycosyl hydrolase mimetic to achieve efficient degradation of cellobiose and cellopentaose. For comparison, free peptides, graphene oxide mixed with free peptides (GO-peptdies) and self-assembled peptide nanofibers (PNFs) were also studied for their activity as a hydrolase mimetics for degradation of cellobiose. Among these materials, GO-PNFs showed the highest hydrolysis activity. Transmission electron microscopy, atomic force microscopy, fluorescence analysis, circular dichroism spectroscopies, X-ray diffraction, Raman spectra and computational modeling were used to interpret the difference in activity mechanism in these artificially designed enzymes. These investigations suggested that high catalytic performance of GO-PNFs toward cellobiose and cellopentaose hydrolysis could be attributed to the formation of nanofiber structures of peptides, optimal molecular conformation and less steric hindrance to access the substrate. More importantly, GO not only served as a platform for attaching PNFs, but also created a hydrophobic microenvironment and facilitated proton transfer, an essential step in catalytic hydrolysis, thus enhancing catalytic activity. All these provided insights into the potential use of peptides and GO hybrid composite nanoenzymes in efficient cellulose hydrolysis.

Reversible Shape Transformation of Ultrathin Polydopamine-Stabilized Droplet

Here we report on the flattening of water droplets using an ultrathin membrane of autopolymerized polydopamine at the air/water interface. This has only been previously reported with the use of synthetic or extracted peptides, two-dimensional designed synthetic peptide thin films with thicknesses of several tens of nanometers. However, in the previous study, the shape of the water droplet was changed irreversibly and the phenomenon was observed only at the air/water interface. In the present study, an ultrathin polydopamine membrane-stabilized droplet induced the flattening of a water droplet at the air/liquid and liquid/liquid interfaces because a polydopamine membrane was spontaneously formed at these interfaces. Furthermore, a reversible transformation of the droplet to flat and dome shape droplets were discovered at the liquid/liquid interface. These are a completely new system because the polydopamine membrane is dynamically synthesized at the interface and the formation speed of the polydopamine membrane overcomes the flattening time scale. These results will provide new insight into physical control of the interfacial shapes of droplets.

Probing the structure-activity relationship of a novel artificial cellobiose hydrolase

The remarkable catalytic properties of enzymes contribute to their unique 3D structures and arrangement of amino acid residues, which provide a blueprint for the design of artificial enzymes. Here, a series of peptide catalysts (PCs) that mimic the unique orientation and function of β-glycosyl hydrolases were designed. Transmission electron microscopy (TEM), fluorescence analysis, circular dichroism spectroscopy, X-ray diffraction and computational modeling were used to investigate and compare the relationship of the fibrinous structure of PCs with its glycoside hydrolysis activity. These results indicated that the catalytic activity of PCs was not only related to their amyloid-like structures, but it can also be influenced by the site, species, molecular arrangement and steric hindrance of the amino acid sequence. What's more, this is the first report on peptide-inspired catalysts that mimic the natural cellobiose hydrolases. All this provided insights into the potential use of peptide nanoenzymes in the generation of efficient artificial enzymes.