Self-assembling Peptide Nanomaterials Research Articles

Active immunotherapy for C5a-mediated inflammation using adjuvant-free self-assembled peptide nanofibers

The terminal protein in the complement cascade C5a is a potent inflammatory molecule and chemoattractant that is involved in the pathology of multiple inflammatory diseases including sepsis and arthritis, making it a promising protein to target with immunotherapies. Active immunotherapies, in which patients are immunized against problematic self-molecules and generate therapeutic antibodies as a result, have received increasing interest as an alternative to traditional monoclonal antibody treatments. In previous work, we have designed supramolecular self-assembling peptide nanofibers as active immunotherapies with defined combinations of B- and T-cell epitopes. Herein, the self-assembling peptide Q11 platform was employed to generate a C5a-targeting active immunotherapy. Two of three predicted B-cell epitope peptides from C5a were found to be immunogenic when displayed within Q11 nanofibers, and the nanofibers were capable of reducing C5a serum concentrations following immunization. Contrastingly, C5a's precursor protein C5 maintained its original concentration, promising to minimize side effects heretofore associated with C5-targeted therapies. Immunization protected mice against an LPS-challenge model of sepsis, and it reduced clinical severity in a model of collagen-antibody induced arthritis. Together, this work indicates the potential for targeting terminal complement proteins with active immunotherapies by leveraging the immunogenicity of self-assembled peptide nanomaterials. Statement of significanceChronic inflammatory diseases such as rheumatoid arthritis, psoriasis, and inflammatory bowel disease are currently treated primarily with monoclonal antibodies against key inflammatory mediators. While helpful for many patients, they have high non-response rates, are costly, and commonly fail as anti-drug antibodies are raised by the patient. The approach we describe here explores a fundamentally different treatment paradigm: raising therapeutic antibody responses with an active immunotherapy.We employ innovative supramolecular peptide nanomaterials to elicit neutralizing antibody responses against complement component C5a and demonstrate therapeutic efficacy in preclinical mouse models of sepsis and rheumatoid arthritis. The strategy reported may represent a potential alternative to monoclonal antibody therapies.

Self-assembly of peptide nanomaterials at biointerfaces: molecular design and biomedical applications.

Self-assembly is an important strategy for constructing ordered structures and complex functions in nature. Based on this, people can imitate nature and artificially construct functional materials with novel structures through the supermolecular self-assembly pathway of biological interfaces. Among the many assembly units, peptide molecular self-assembly has received widespread attention in recent years. In this review, we introduce the interactions (hydrophobic interaction, hydrogen bond, and electrostatic interaction) between peptide nanomaterials and biological interfaces, summarizing the latest advancements in multifunctional self-assembling peptide materials. We systematically demonstrate the assembly mechanisms of peptides at biological interfaces, such as proteins and cell membranes, while highlighting their application potential and challenges in fields like drug delivery, antibacterial strategies, and cancer therapy.

Peptide-Based Nanoarchitectonics for the Treatment of Liver Fibrosis.

Liver fibrosis is a process of excessive accumulation of extracellular matrix caused by liver injury. Liver fibrosis can progress to cirrhosis or even liver cancer without proper intervention. Until now, no effective therapeutic drugs have been clinically approved for treating liver fibrosis. Hence, the development of safe and effective antifibrotic drugs is particularly important. As a representative biomaterial, peptides have been investigated as key components for constructing antifibrotic nanomaterials given their advantages of biological origination, synthetic availability, and good biocompatibility. Peptides serve as multifunctional motifs in antifibrotic nanomaterials, such as liver-targeting molecules, antifibrotic molecules, and self-assembling building blocks for the formation of the nanomaterials. In this review, we focus on peptide-based nanoarchitectonics for treating liver fibrosis, including nanomaterials modified with liver-targeting peptides, nanomaterials for the efficient delivery of antifibrotic peptides, and self-assembled peptide nanomaterials for the delivery of antifibrotic drugs. The design rules of these peptide-based nanomaterials are described. The antifibrotic mechanisms and effects of these peptide-based nanomaterials in treating liver fibrosis and related diseases are highlighted. The challenges and future perspectives of using peptide-based nanoarchitectonics for the treatment of liver fibrosis are discussed. These results are expected to accelerate the rational design and clinical translation of antifibrotic nanomaterials.

Advances in Self-Assembled Peptides as Drug Carriers.

In recent years, self-assembled peptide nanotechnology has attracted a great deal of attention for its ability to form various regular and ordered structures with diverse and practical functions. Self-assembled peptides can exist in different environments and are a kind of medical bio-regenerative material with unique structures. These materials have good biocompatibility and controllability and can form nanoparticles, nanofibers and hydrogels to perform specific morphological functions, which are widely used in biomedical and material science fields. In this paper, the properties of self-assembled peptides, their influencing factors and the nanostructures that they form are reviewed, and the applications of self-assembled peptides as drug carriers are highlighted. Finally, the prospects and challenges for developing self-assembled peptide nanomaterials are briefly discussed.

Two-dimensional peptide nanosheets functionalized with gold nanorods for photothermal therapy of tumors.

Self-assembled peptide nanomaterials exhibit great potential for applications in materials science, energy storage, nanodevices, analytical science, biomedicine, tissue engineering, and others due to their tailorable ordered nanostructures and unique physical, chemical, and biological properties. Although one-dimensional peptide nanofibers and nanotubes have been widely used for biomedical applications, the design and synthesis of two-dimensional (2D) peptide nanostructures for cancer therapy remain challenging. In this work, we describe the creation of 2D biocompatible peptide nanosheets (PNSs) through molecular self-assembly, which can provide support matrixes for conjugating gold nanorods (AuNRs) to form high-performance 2D nanomaterials for photothermal conversion. After molecular modification, AuNRs can be chemically conjugated onto the surface of 2D PNSs, and the created PNS-AuNR nanohybrids serve as a potential nanoplatform for photothermal therapy of tumor cells. The obtained results indicate that both PNSs and AuNRs contribute to the improved efficiency of photothermal therapy (PTT) of tumors, in which 2D PNSs provide high biocompatibility and a large surface area for binding AuNRs, and AuNRs show a high PTT ability towards tumors. The strategies of molecular design and functional tailoring of self-assembled peptide nanomaterials shown in this study are valuable and inspire the synthesis of biomimetic nanomaterials for biomedicine and tissue engineering applications.

Mitochondria-Targeted Self-Assembly of Peptide-Based Nanomaterials.

Mitochondria are well known to serve as the powerhouse for cells and also the initiator for some vital signaling pathways. A variety of diseases are discovered to be associated with the abnormalities of mitochondria, including cancers. Thus, targeting mitochondria and their metabolisms are recognized to be promising for cancer therapy. In recent years, great efforts have been devoted to developing mitochondria-targeted pharmaceuticals, including small molecular drugs, peptides, proteins, and genes, with several molecular drugs and peptides enrolled in clinical trials. Along with the advances of nanotechnology, self-assembled peptide-nanomaterials that integrate the biomarker-targeting, stimuli-response, self-assembly, and therapeutic effect, have been attracted increasing interest in the fields of biotechnology and nanomedicine. Particularly, in situ mitochondria-targeted self-assembling peptides that can assemble on the surface or inside mitochondria have opened another dimension for the mitochondria-targeted cancer therapy. Here, we highlight the recent progress of mitochondria-targeted peptide-nanomaterials, especially those in situ self-assembly systems in mitochondria, and their applications in cancer treatments.

Self-Assembling Peptides as an Emerging Platform for the Treatment of Metabolic Syndrome.

Metabolic syndrome comprises a cluster of comorbidities that represent a major risk of developing chronic diseases, such as type II diabetes, cardiovascular diseases, and stroke. Alarmingly, metabolic syndrome reaches epidemic proportions worldwide. Today, lifestyle changes and multiple drug-based therapies represent the gold standard to address metabolic syndrome. However, such approaches face two major limitations: complicated drug therapeutic regimes, which in most cases could lead to patient incompliance, and limited drug efficacy. This has encouraged scientists to search for novel routes to deal with metabolic syndrome and related diseases. Within such approaches, self-assembled peptide formulations have emerged as a promising alternative for treating metabolic syndrome. In particular, self-assembled peptide hydrogels, either as acellular or cell-load three-dimensional scaffoldings have reached significant relevance in the biomedical field to prevent and restore euglycemia, as well as for controlling cardiovascular diseases and obesity. This has been possible thanks to the physicochemical tunability of peptides, which are developed from a chemical toolbox of versatile amino acids enabling flexibility of designing a wide range of self-assembled/co-assembled nanostructures forming biocompatible viscoelastic hydrogels. Peptide hydrogels can be combined with several biological entities, such as extracellular matrix proteins, drugs or cells, forming functional biologics with therapeutic ability for treatment of metabolic syndrome-comorbidities. Additionally, self-assembly peptides combine safety, tolerability, and effectivity attributes; by this presenting a promising platform for the development of novel pharmaceuticals capable of addressing unmet therapeutic needs for diabetes, cardiovascular disorders and obesity. In this review, recent advances in developing self-assembly peptide nanostructures tailored for improving treatment of metabolic syndrome and related diseases will be discussed from basic research to preclinical research studies. Challenges facing the development of approved medicinal products based on self-assembling peptide nanomaterials will be discussed in light of regulatory requirement for clinical authorization.

Self-Assembled Peptide Drug Delivery Systems.

Over the past several decades, rapid advances have been made in the application of nanomaterials in the biomedical field including bioimaging and drug delivery. Owing to the natural biocompatibility, diverse design, and dynamic self-assembly, peptides can be used as modules to construct self-assembled peptide-based nanomaterials, which have a high potential in reducing drug toxicity, improving drug targeting, and enhancing drug delivery efficiency. In this review, three typical design strategies of self-assembled peptide nanomaterials for drug delivery have been summarized including ex situ construction, in situ morphological transformation, and in situ construction of peptide drug delivery systems (PDDs). Drugs can be loaded to peptide nanomaterials by physical encapsulation or chemical conjugation methods, showing enhanced retention effects at tumor sites to increase the uptake rate of drugs. Interestingly, drug-free peptide nanomaterials also can be nanomedicines for delivery. These advances implicate the bright prospect of the self-assembled peptide in intelligent nanomedicine and clinical translation.

Enzyme-instructed self-assembly of peptides: Process, dynamics, nanostructures, and biomedical applications

Biomolecular self-assembly provides a potential way for the design and synthesis of functional biomaterials with uniform structure and unique properties, in which the self-assembly of peptide molecules is especially important ascribed to the controllable structural design and functional tailoring of peptide motifs. The self-assembly of peptides can be instructed by internal and external physical, chemical, and biological stimulations. Compared to both physical and chemical stimulations including light/thermal treatment, pH/ionic strength adjustment, and others, the biological mediation with enzymes exhibited great advantages due to its high bioactivity, excellent biocompatibility, high specificity, and in vivo reaction. Herein we summarize the advance in the enzyme-instructed peptide self-assembly for biomedical applications. For this aim, we introduce and discuss the self-assembly of peptide that controlled by both kinetics and dynamics, and then demonstrate the enzyme-induced preparation of peptide nanostructures such as nanofibers, nanotubes, vesicles, networks, and hydrogels. Finally, the biomedical applications of enzyme-induced self-assembled peptide nanomaterials for cancer diagnostics, cancer therapy, bioelectronic devices, and biosensors are presented. It is expected this work will inspire more studies on the using of bioactive enzymes for triggering the self-assembly of peptides to create various novel bionanomaterials, which could extend this interesting research field to others such as tissue engineering, biocatalysis, energy storage, and environmental science.

Neglected Hydrophobicity of Dimethanediyl Group in Peptide Self-Assembly: A Hint from Amyloid-like Peptide GNNQQNY and Its Derivatives.

Besides typical hydrophobic amino acids providing hydrophobic interactions, glutamine as a hydrophilic amino acid has also been known to be an important element in many self-assembling peptides, but it is still not clear how this particular amino acid contributes to the self-assembling process. We supposed that the dimethanediyl group in the side chain of glutamine could provide hydrophobic interaction for peptide self-assembly. To prove this hypothesis, we used the GNNQQNY peptide and its derivatives as examples to show the importance of the dimethanediyl group for peptide self-assembly. We found a very close relationship between the number of dimethanediyl groups, the strength of hydrophobic interaction, and the self-assembling ability of the peptides, indicating the hydrophobicity of the dimethanediyl group and its important role for self-assembly. This new finding might be instructive for clarifying the self-assembling mechanism of many natural peptides, as well as for developing novel self-assembling peptide nanomaterials.

Supramolecular self assembly of nanodrill-like structures for intracellular delivery

Despite recent advances in the supramolecular assembly of cell-penetrating peptide (CPP) nanostructures, the tuning of size, shape, morphology and packaging of drugs in these materials still remain unexplored. Herein, through sequential ligation of peptide building blocks, we create cell-penetrating self-assembling peptide nanomaterials (CSPNs) with the capability to translocate inside cells. We devised a triblock array of Tat48–59 [HIV-1 derived transactivator of transcription48–59] based CPPs, conjugated to up to four Phenylalanine (Phe) residues through an amphiphilic linker, (RADA)2. We observed that the sequential addition of Phe leads to the transition of CSPN secondary structures from a random coil, to a distorted α-helix, a β-sheet, or a pure α-helix. This transition occurs due to formation of a heptad by virtue of even number of Phe. Atomic force microscopy revealed that CSPNs form distinct shapes reminiscent of a “drill-bit”. CSPNs containing two, three or four Phe, self-assemble into “nanodrill-like structures” with a coarse-twisted, non-twisted or fine-twisted morphology, respectively. These nanodrills had a high capacity to encapsulate hydrophobic guest molecules. In particular, the coarse-twisted nanodrills demonstrate higher internalization and are able to deliver rapamycin, a hydrophobic small molecule that induced autophagy and are capable of in vivo delivery. Molecular dynamics studies provide microscopic insights into the structure of the nanodrills that can contribute to its morphology and ability to interact with cellular membrane. CSPNs represent a new modular drug delivery platform that can be programmed into exquisite structures through sequence-specific fine tuning of amino acids.

Self-assembled peptide nanomaterials for biomedical applications: promises and pitfalls.

Over the last several decades, a great number of advances have been made in the area of self-assembled supramolecules for regenerative medicine. Such advances have involved the design, preparation, and characterization of brand new self-assembled peptide nanomaterials for a variety of applications. Among all biomolecules considered for self-assembly applications, peptides have attracted a great deal of attention as building blocks for bottom-up fabrication, due to their versatility, ease of manufacturing, low costs, tunable structures, and versatile properties. Herein, some of the more exciting new designs of self-assembled peptides and their associated unique features are reviewed and several promising applications of how self-assembled peptides are advancing drug delivery, tissue engineering, antibacterial therapy, and biosensor device applications are highlighted.

Progress in Self-assembling Peptide-based Nanomaterials for Biomedical Applications

Self-assembled peptide nanomaterials display the advantageous properties of injectability, biodegradability and biocompatibility. These peptide nanomaterials, by self-assembling, can be widely applied in such fields as drug delivery (small molecules and large molecules), regenerative medicine and nanobiotechnology. In this review, we mainly discuss the properties of these peptide nanomaterials in their physical, chemical and biological aspects. Also discussed are recent advances in their potential applications as drug delivery systems and for uses in regenerative medicine. These current advances show a bright future for the development and clinical applications of self-assembled peptide-based nanotechnology and nanomedicine. However, there are still some big challenges for us to face before these peptide nanomaterials eventually can be used for the treatment of human diseases.

Beta-Sheet-Forming, Self-Assembled Peptide Nanomaterials towards Optical, Energy, and Healthcare Applications.

Peptide self-assembly is an attractive route for the synthesis of intricate organic nanostructures that possess remarkable structural variety and biocompatibility. Recent studies on peptide-based, self-assembled materials have expanded beyond the construction of high-order architectures; they are now reporting new functional materials that have application in the emerging fields such as artificial photosynthesis and rechargeable batteries. Nevertheless, there have been few reviews particularly concentrating on such versatile, emerging applications. Herein, recent advances in the synthesis of self-assembled peptide nanomaterials (e.g., cross β-sheet-based amyloid nanostructures, peptide amphiphiles) are selectively reviewed and their new applications in diverse, interdisciplinary fields are described, ranging from optics and energy storage/conversion to healthcare. The applications of peptide-based self-assembled materials in unconventional fields are also highlighted, such as photoluminescent peptide nanostructures, artificial photosynthetic peptide nanomaterials, and lithium-ion battery components. The relation of such functional materials to the rapidly progressing biomedical applications of peptide self-assembly, which include biosensors/chips and regenerative medicine, are discussed. The combination of strategies shown in these applications would further promote the discovery of novel, functional, small materials.

Ethanol induced the formation of β‐sheet and amyloid‐like fibrils by surfactant‐like peptide A6K

Self-assembly of natural or designed peptides into fibrillar structures based on β-sheet conformation is a ubiquitous and important phenomenon. Recently, organic solvents have been reported to play inductive roles in the process of conformational change and fibrillization of some proteins and peptides. In this study, we report the change of secondary structure and self-assembling behavior of the surfactant-like peptide A6K at different ethanol concentrations in water. Circular dichroism indicated that ethanol could induce a gradual conformational change of A6K from unordered secondary structure to β-sheet depending upon the ethanol concentration. Dynamic light scattering and atomic force microscopy revealed that with an increase of ethanol concentration the nanostructure formed by A6K was transformed from nanosphere/string-of-beads to long and smooth fibrils. Furthermore, Congo red staining/binding and thioflavin-T binding experiments showed that with increased ethanol concentration, the fibrils formed by A6K exhibited stronger amyloid fibril features. These results reveal the ability of ethanol to promote β-sheet conformation and fibrillization of the surfactant-like peptide, a fact that may be useful for both designing self-assembling peptide nanomaterials and clarifying the molecular mechanism behind the formation of amyloid fibrils.

FORMATION OF REVERSED MICELLE NANORING BY A DESIGNED SURFACTANT-LIKE PEPTIDE

Designing self-assembling peptides as nanomaterials has been an attractive strategy in recent years, however, these peptides were usually studied in aqueous solutions for their self-assembling behaviors and applications. In this study, we have designed a surfactant-like peptide AGD with a wedge-like shape and studied its self-assembling behaviors in aqueous solution or nonpolar system. By analyzing the intermolecular hydrogen bond using FT-IR and characterizing the nanostructures with DLS, AFM and TEM, it was confirmed that AGD could not undergo self-assembly in aqueous solution while could self-assemble into well-ordered nanorings in nonpolar system. A molecular model has been proposed to explain how the nanorings were formed in the manner of reversed micelle. These results suggested a novel strategy to fabricate self-assembling peptide nanomaterials in nonpolar system, which could have potential applications in many fields.

Cell-adhesive hydrogels composed of peptide nanofibers responsive to biological ions

Novel calcium ion (Ca2+)-responsive hydrogels composed of designed β-sheet peptides were constructed. As the novel designed peptide, E1Y9, has a Glu residue to interact with Ca2+, the peptide in the sol-state self-assembled into hydrogels in the presence of Ca2+. The hydrogelation did not occur in the absence of Ca2+; therefore, Ca2+-dependent hydrogelation was achieved by the molecular design. The hydrogelation from the viscous sol-state solution can be induced by a slower self-assembly process of the β-sheet peptide involving a rapid process of Ca2+binding. When the sol-state peptide solution was injected with Ca2+, gel drops and strings with desired shapes could be constructed. Different cell lines can be cultured on the hydrogel, demonstrating its low toxicity, which is comparable to commercially available microtiter plate surfaces for cell culture. Furthermore, the hydrogels showed a high cell-adhesive ability that was similar in magnitude to fibronectin, which is a native cell-adhesive protein. The Ca2+-responsive peptide nanofiber-based hydrogelation system will facilitate novel studies exploiting self-assembling peptide nanomaterials that will lead to cell-based technology, such as three-dimensional cell culturing. Newly designed β-sheet peptides bearing the calcium ion binding Glu residue were self-assembling into self-supporting hydrogels. The hydrogelation from the viscous sol-state solution can be induced by a slower self-assembly process followed by a rapid injection to Ca2+ solution. Peptide gel strings can be easily constructed. Cell culture experiments demonstrated low toxicity and high-adhesive abilities of the peptide hydrogels.

Dense surface functionalization using peptides that recognize differences in organized structures of self-assembling nanomaterials

We obtained novel peptides that selectively bind to self-assembling peptide nanomaterials from a random peptide library displayed on phages. Affinity-dependent peptide screening gave phage clones displaying peptides with selective affinities against two kinds of highly networked nanofibers constructed of β-sheet peptides. Both peptide nanofibers have similar primary structures. Binding analyses of phage-displayed peptides by enzyme-linked immunosorbent assays demonstrated that the screened peptides specifically bind to the target nanofibers rather than to non-target nanofibers. Dot blot assays using chemically-synthesized peptides revealed that one screened peptide with the sequence Thr-Tyr-Leu-Pro-Trp-Pro-Ala has an affinity constant of 2.6 × 10(6) M(-1) against the target nanofibers. This affinity is 350 times greater than its affinity for non-target nanofibers and 90 times greater than its affinity for mixed nanofibers that contain 50% target nanofibers. These results suggest that this screened peptide can recognize organized fine-structures. Surface modification of the peptide nanofibers with the screened peptide demonstrated that the peptide specifically binds to discrete binding sites on the target nanofibers. Cell adhesion assays on the nanofibers by means of RGDS-conjugated screened peptides showed that the number of adhered cells is largely dependent on the amount of bound RGDS-peptide. These results suggest that screened peptides can recognize the organization of self-assembled peptide nanomaterials, and that the conjugation of functional groups to the peptides can be used to functionalize the target nanomaterials. Furthermore, simultaneous use of individual specific peptides that have specificities for nanomaterials can generate highly dense functionalized self-assembling peptide nanomaterials.

Affinity-Based Screening of Peptides Recognizing Assembly States of Self-Assembling Peptide Nanomaterials

Novel peptides capable of binding to self-assembled peptide nanomaterials were identified from a random heptapeptide library displayed on phages. Affinity-dependent peptide screening against helically coiled nanofibers constructed of beta-sheet peptides gave phage clones displaying peptides with a variety of affinities and selectivities. An enzyme-linked immunosorbent assay using phage-displayed peptides revealed that the screened peptides specifically bind to target nanofibers, in contrast to reference nanofibers comprised of peptides with slightly different amino acid sequences. A Dot blot assay using chemically synthesized peptides demonstrated that peptide 01 (p01), with the sequence Thr-Gly-Val-Lys-Gly-Pro-Gly, showed an affinity constant (3.7 x 10(5) M(-1)) for the target nanofibers 200 times greater than its affinity for monomeric peptides and 60 times greater than for short nanofibers. These results suggested that p01 selectively recognizes the assembly state of the target peptide. ATR/IR secondary structure analyses clearly showed that when p01 binds to target nanofibers, it undergoes a structural transition from random-coil to parallel beta-sheet structures, resulting in greater affinity and high specificity for the target fiber. Surface modification of the peptide nanofibers by p01 demonstrated that the peptide specifically binds to the edge of the nanofibers. Using p01, uniform arrays of gold nanoparticles (proteins) could be generated on the peptide nanomaterials.