Peptide-based Nanostructures Research Articles

A Matter of Charge: Electrostatically Tuned Coassembly of Amphiphilic Peptides.

Coassembly of peptide biomaterials offers a compelling avenue to broaden the spectrum of hierarchically ordered supramolecular nanoscale structures that may be relevant for biomedical and biotechnological applications. In this work coassemblies of amphiphilic and oppositely charged, anionic and cationic, β-sheet peptides are studied, which may give rise to a diverse range of coassembled forms. Mixtures of the peptides show significantly lower critical coassembly concentration (CCC) values compared to those of the individual pure peptides. Intriguingly, the highest formation of coassembled fibrils is found to require excess of the cationic peptide whereas equimolar mixtures of the peptides exhibited the maximum folding into β-sheet structures. Mixtures of the peptides coassembled sequentially from solutions at concentrations surpassing each peptide's intrinsic critical assembly concentration (CAC), are also found to require a higher portion of the cationic peptide to stabilize hydrogels. This study illuminates a systematic investigation of oppositely charged β-sheet peptides over a range of concentrations, in solutions and in hydrogels. The results may be relevant to the fundamental understanding of such intricate charge-driven assembly systems and to the formulation of peptide-based nanostructures with diverse functionalities.

Vertically Grown Bioinspired Diphenylalanine Nanowire-Coated Fabric for Oil-Water Separation.

Due to the pervasive use of oil for energy and other industrial applications, solutions to oil-water separation have received a great deal of attention lately to address the environmental damage of oil spills and groundwater contamination. However, many of these separation methods are materially expensive and environmentally hazardous, require elaborate fabrication, or rely on large amounts of energy to function. Herein, we provide an effective low-cost method for oil-water separation based on the hydrophobicity induced by self-assembled bioinspired diphenylalanine peptide nanowires grown on polyester fabric. This modified polyester fabric mesh exhibits parahydrophobicity and oleophilicity due to the hierarchical nano-to-microscale surface roughness. This mesh also achieves consistent high water separation efficiencies of over 99% and an ultrahigh oil flux of up to 26.7 ± 5 kLm-2·h-1. The growth of bioinspired peptide-based nanostructures on fabrics using facile technique and their application in oil-water separation presents the potential for using bioinspired materials for environmental remediation while minimizing environmental footprint.

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.

Peptide-Based Optical/Electronic Materials: Assembly and Recent Applications in Biomedicine, Sensing, and Energy Storage.

The unique optical and electronic properties of living systems are impressive. Peptide-based supramolecular self-assembly systems attempt to mimic these properties by preparation optical/electronic function materials with specific structure through simple building blocks, rational molecular design, and specific kinetic stimulation. From the perspective of building blocks and assembly strategies, the unique optical and electronic properties of peptide-based nanostructures, including peptides self-assembly and peptides regulate the assembly of external function subunits, are systematically reviewed. Additionally, their applications in biomedicine, sensing, and energy storage are also highlighted. This bioinspired peptide-based function material is one of the hot candidates for the new generation of green intellect materials, with many advantages such as biocompatibility, environmental friendliness, and adjustable morphology.

Anti-Glioma Activity Achieved by Dual Blood-Brain Barrier/Glioma Targeting Naive Chimeric Peptides-Based Co-Assembled Nanophototheranostics.

Peptide monomers can either self-assemble with themselves enacting a solo-component assembly or they can co-assemble by interacting with other suitable partners to mediate peptide co-assembly. Peptide co-assemblies represent an innovative class of naive, multifunctional, bio-inspired supramolecular constructs that result in the production of nanostructures with widespread functional, structural, and chemical multiplicity. Herein, the co-assembly of novel chimeric peptides (conjugates of T7 (HAIYPRH)/t-Lyp-1 (CGNKRTR) peptides and aurein 1.2 (GLFDIIKKIAESF)) has been explored as a means to produce glioma theranostics exhibiting combinatorial chemo-phototherapy. Briefly, we have reported here the design and solid phase synthesis of a naive generation of twin-functional peptide drugs incorporating the blood-brain barrier (BBB) and glioma dual-targeting functionalities along with anti-glioma activity (G-Anti G and B-Anti G). Additionally, we have addressed their multicomponent co-assembly and explored their potential application as glioma drug delivery vehicles. Our naive peptide drug-based nanoparticles (NPs) successfully demonstrated a heightened glioma-specific delivery and anti-glioma activity. Multicomponent indocyanine green (ICG)-loaded peptide co-assembled NPs (PINPs: with a hydrodynamic size of 348 nm and a zeta-potential of 5 mV) showed enhanced anti-glioma responses in several cellular assays involving C6 cells. These included a mass demolition with no wound closure (i.e., a 100% cell destruction) and around 63% collaborative chemo-phototoxicity (with both a photothermal and photodynamic effect) after near infrared (NIR) 808 laser irradiation. The dual targeting ability of peptide bioconjugates towards both the BBB and glioma cells, presents new opportunities for designing tailored and better peptide-based nanostructures or nanophototheranostics for glioma.

Delivery of a Cancer-Testis Antigen-Derived Peptide Using Conformationally Restricted Dipeptide-Based Self-Assembled Nanotubes.

Use of tumor-associated antigens for cancer immunotherapy is limited due to their poor in vivo stability and low cellular uptake. Delivery of antigenic peptides using synthetic polymer-based nanostructures has been actively pursued but with limited success. Peptide-based nanostructures hold much promise as delivery vehicles due to their easy design and synthesis and inherent biocompatibility. Here, we report self-assembly of a dipeptide containing a non-natural amino acid, α,β-dehydrophenylalanine (ΔF), into nanotubes, which efficiently entrapped a MAGE-3-derived peptide (M3). M3 entrapped in F-ΔF nanotubes was more stable to a nonspecific protease treatment and both F-ΔF and F-ΔF-M3 showed no cellular toxicity for four cancerous and noncancerous cell lines used. F-ΔF-M3 showed significantly higher cellular uptake in RAW 267.4 macrophage cells compared to M3 alone and also induced in vitro maturation of dendritic cells (DCs). Immunization of mice with F-ΔF-M3 selected a higher number of IFN-γ secreting CD8+ T cells and CD4+ T compared to M3 alone. On day 21, a tumor growth inhibition ratio (TGI, %) of 41% was observed in a murine melanoma model. These results indicate that F-ΔF nanotubes are highly biocompatible, efficiently delivered M3 to generate cytotoxic T lymphocytes responses, and able to protect M3 from degradation under in vivo conditions. The F-ΔF dipeptide-based nanotubes may be considered as a good platform for further development as delivery agents.

Sono-Assembly of the [Arg-Phe]4 Octapeptide into Biofunctional Nanoparticles.

High-frequency ultrasound treatment is found to be a one-pot green technique to produce peptide-based nanostructures by ultrasound assisted self-assembly of oligopeptides. [Arg-Phe]4 octapeptides, consisting of alternating arginine (Arg/R) and phenylalanine (Phe/F) sequences, were subjected to 430 kHz ultrasound in aqueous solution in the absence of any external agents, to form [RF]4 nanoparticles ([RF]4-NPs), ~220 nm in diameter. A comprehensive analysis of the obtained nanoparticles demonstrated that the aromatic moieties of the oligopeptides can undergo oxidative coupling to form multiple oligomeric species, which then self-assemble into well-defined fluorescent nanoparticles. [RF]4-NPs were functionalized with polyethylene glycol (PEGylated) to improve their colloidal stability. Unlike the parent peptide, the PEGylated [RF]4-NPs showed limited cytotoxicity towards MDA-MB-231 cells. Furthermore, the intracellular trafficking of PEGylated [RF]4-NPs was investigated after incubation with MDA-MB-231 cells to demonstrate their efficient endo-lysosomal escape. This work highlights that the combined use of ultrasonic technologies and peptides enables easy fabrication of nanoparticles, with potential application in drug delivery.

Coassemble dopamine and GHK tripeptide into fluorescent nanoparticles for pH sensing.

Fluorescent nanostructures have been widely applied to biomedical researches and clinical diagnosis such as biolabeling/imaging/sensing and have even acted as therapy reagents. Peptide-based fluorescent nanostructures attract recent interest from biomedical researchers. Inspired by the natural existence of GHK-Cu complex with a growth factor-like effect in human blood, here we have developed a novel approach for designing nanosensors through the co-assembling of two kinds of biomolecules. By making best use of both π-π stacking between carbon rings and the easy-oxidation property of an important transmitter molecule, dopamine (DA), we successfully built up a supersensitive and robust fluorescent pH nanosensor by co-assembling oxidized DA (DAox ) with a tripeptide GHK. The GHK-DAox nanostructures have a quantum yield of 20.82%, which might be the brightest one among all the current co-assembling structures merely through unmodified biomolecules. We envision this approach could open a new avenue for not only hybrid nanostructure construction, but also may inspire the bioengineering of in vivo luminescent probes.

Amphipathic design dictates self-assembly, cytotoxicity and cell uptake of arginine-rich surfactant-like peptides.

Amphiphilicity is the most critical parameter in the self-assembly of surfactant-like peptides (SLPs), regulating the way by which hydrophobic attraction holds peptides together. Its effects go beyond supramolecular assembly and may also trigger different cell responses of bioactive peptide-based nanostructures. Herein, we investigate the self-assembly and cellular effects of nanostructures based on isomeric SLPs composed by arginine (R) and phenylalanine (F). Two amphipathic designs were studied: a diblock construct F4R4 and its bolaamphiphile analog R2F4R2. A strong sequence-dependent polymorphism emerges with appearance of globules and vesicle-like assemblies, or flat nanotapes and cylindrical micelles. The diblock construct possesses good cell penetrating capabilities and effectiveness to kill SK-MEL-28 melanoma tumor cells, in contrast to reduced intracellular uptake and low cytotoxicity exhibited by the bolaamphiphilic form. Our findings demonstrate that amphipathic design is a relevant variable for self-assembling SLPs to modulate different cellular responses and may assist in optimizing the production of nanostructures based on arginine-enriched sequences in cell penetrating and antimicrobial peptides.

Cyclic peptide-based nanostructures as efficient siRNA carriers

RNA interference shows a great strategy for biological studies; however, delivering of small interfering RNA (siRNA) remains challenging. Although several delivery vehicles, including cell-penetrating peptides, have been developed, their implementation is often restricted because of their endosomal entrapment. Herein, we report the formation of self-assembled nanostructures from rationally designed cyclic peptides and explore them for efficient delivery of functional biomacromolecules such as siRNA into mammalian cells. The newly obtained soft materials make stable complexes with siRNAs, thereby increasing their stability and deliver fluorescent labelled siRNA inside the cells as evident from confocal microscopy analysis. Flow cytometry analysis reveals that significant uptake of FAM-siRNA occurs in the presence of peptide nanostructures compared with siRNA alone. Peptide nanostructure-mediated delivery of very low concentration of siRNA causes significant knockdown of the target gene as observed at protein level by Western blot analysis, which is comparable to lipofectamine, commercially available transfection agent.

Molecular Mechanisms of Tryptophan-Tyrosine Nanostructures Formation and their Influence on PC-12 Cells.

The discovery of self-assembling peptides, which can form well-ordered structures, has opened a realm of opportunity for the design of tailored short peptide-based nanostructures. In this study, a combined experimental and computational approach was utilized to understand the intramolecular and intermolecular interactions contributing to the self-assembly of linear and cyclic tryptophan-tyrosine (WY) dipeptides. The density functional tight binding (DFTB) calculations with empirical dispersive corrections assisted the identification of the lowest energy conformers. Conformer analysis and the prediction of the electronic structure for the monomeric, dimeric, and hexameric forms of the cyclic and linear WY confirmed the contributions of hydrogen bonding, π-π stacking, and CH-π interactions in the stability of the self-assembled nanotubes. The influence of the processing conditions on the morphological and thermal characteristics, as well as the secondary structures of the synthesized nanostructures, were analyzed. Preliminary studies of the influence of the nanotubes on the fate of neuronalcell lines such as, PC-12cells indicate that the nanotubes promote cellular proliferation, and differentiation in the absence of growth factors. The aspect ratio of the nanotubes played an essential role in cellular interactions where a higher cellular uptake was observed in nanotubes of lower aspect ratios. These results provide insight for future applications of such nanotubes as scaffolds for tissue engineering and nerve regeneration and in drug delivery.

Vertical Alignment of Size-Controlled Self-Assembled Diphenylalanine Peptide Nanotubes Using Polyethersulfone Hollow Fiber Membranes On Silicon

The strong piezoelectricity in diphenylalanine peptide develops its technological potential as a smart material. To achieve insight into the vertical alignment of size-controlled self-assembled diphenylalanine peptide nanotubes, an aromatic peptide of diphenylalanine (FF) was applied in this research as the model peptide. Here we found for the first time a vertical alignment of size-controlled self-assembled diphenylalanine peptide nanotubes during the peptide self-assembly process of nanotubes composite using polyethersulfone (PES) membrane in situ and ex situ peregnation of peptide nano tube. The membrane structure was investigated using fluofenamic acid as a fluorescent tag and a first-line solution containing dipeptides and hexafluoropropane (HFP). The results showed a vertical alignment of size-controlled self-assembled diphenylalanine peptide nanotubes formation on silicon. The STM and SEM results indicated the formation of different nanostructures including short nanorods, nanotubes branched nanotubes and dendritic nanostructures of peptide in PES membrane. Our novel approach based on the PES membrane and HFP allows one to controllably fabricate various peptide-based nanostructures on silicon.

Self-assembly of peptide-based nanostructures: Synthesis and biological activity

Peptide-based nanostructures have received much attention in the field of drug targeting. In fact, peptides have many advantages such as simplicity of the structure, biocompatibility, and chemical diversity. Moreover, some peptides, which are called cell-penetrating peptides, can cross cellular membranes and carry small molecules, small interfering RNA, or viruses inside live cells. These molecules are often covalently or noncovalently linked to cargoes, thus forming amphiphilic conjugates that can self-assemble. Supramolecular nanostructures formed from peptides are used in nanomedicine as a carrier to protect a drug and to target cancer cells. This review explores aliphatic-chain–conjugated peptides and drug-conjugated peptides that can self-assemble. Special emphasis is placed on the synthesis procedure, nanostructure formation, and biological activity.

Diphenylalanine-Based Microribbons for Piezoelectric Applications via Inkjet Printing.

Peptide-based nanostructures are very promising for nanotechnological applications because of their excellent self-assembly properties, biological and chemical flexibility, and unique multifunctional performance. However, one of the limiting factors for the integration of peptide assemblies into functional devices is poor control of their alignment and other geometrical parameters required for device fabrication. In this work, we report a novel method for the controlled deposition of one of the representative self-assembled peptides-diphenylalanine (FF)-using a commercial inkjet printer. The initial FF solution, which has been shown to readily self-assemble into different structures such as nano- and microtubes and microrods, was modified to be used as an efficient ink for the printing of aligned FF-based structures. Furthermore, during the development of the suitable ink, we were able to produce a novel type of FF conformation with high piezoelectric response and excellent stability. By using this method, ribbonlike microcrystals based on FF could be formed and precisely patterned on different surfaces. Possible mechanisms of structure formation and piezoelectric effect in printed microribbons are discussed along with the possible applications.

Peptides and their Metal Complexes in Neurodegenerative Diseases: from Structural Studies to Nanomedicine Prospects.

The metal ions dyshomeostasis is increasingly recognized to play a crucial role in the development of aging-related neurodegenerative diseases. Metal trafficking in the brain is related to proteins regulating both uptake and efflux of metals in neurons. Different pathways may occur, depending on specific binding features of metallo-protein complexes. In particular, copper, zinc and iron are recognized to influence the biochemistry of proteins involved in neurodegeneration (for instance Aβ and α-synuclein), as well as those playing a crucial role in neuronal development and efficiency (neurotrophins). Nowadays the application of peptide-based drugs is widespread for different pathologies, but the short lifetime in vivo due to proteolysis and other shortcomings still limit their use. A structured search was performed about the state of the art on: i) peptidomimetic approaches used to obtain peptides mimicking the metal binding activities of proteins involved in neurons survival, ii) peptide-based nanostructures, as promising biomaterials in tissue engineering and substrates for neurites outgrowth and synapses formation. Recent developments on metal-binding peptides and peptide nanostructures for therapeutic application in neurodegenerative diseases are reviewed, showing as metal ions interaction may affect structural and biological properties of different proteins involved in neurodegenerative diseases. This review provides a survey on peptides able to mimic some biofunctional activities of the whole protein, e.g., the binding features to metal ions, thus highlighting their promising potentialities as new, more effective, therapeutics. The integration of such peptides into multifunctional nanoplatforms can be a smart route for the development of biomaterials scaffolds and nanomedicine applications.

Multicomponent self-assembly as a tool to harness new properties from peptides and proteins in material design.

Nature is enriched with a wide variety of complex, synergistic, and highly functional protein-based multicomponent assemblies. As such, nature has served as a source of inspiration for using multicomponent self-assembly as a platform to create highly ordered, complex, and dynamic protein and peptide-based nanostructures. Such an assembly system relies on the initial interaction of distinct individual building blocks leading to the formation of a complex that subsequently assembles into supramolecular architectures. This approach not only serves as a powerful platform for gaining insight into how proteins co-assemble in nature but also offers huge opportunities to harness new properties not inherent in the individual building blocks. In the past decades, various multicomponent self-assembly strategies have been used to extract synergistic properties from proteins and peptides. This review highlights the updates in the field of multicomponent self-assembly of proteins and peptides and summarizes various strategies, including covalent conjugation, ligand-receptor interactions, templated/directed assembly and non-specific co-assembly, for driving the self-assembly of multiple proteins and peptide-based building blocks into functional materials. In particular, we focus on peptide- or protein-containing multicomponent systems that, upon self-assembly, enable the emergence of new properties or phenomena. The ultimate goal of this review is to highlight the importance of multicomponent self-assembly in protein and peptide engineering, and to advocate its growth in the fields of materials science and nanotechnology.

Self-assembly pathways and polymorphism in peptide-based nanostructures.

Dipeptide derivative molecules can self-assemble into space-filling nanofiber networks at low volume fractions (<1%), allowing the formation of molecular gels with tunable mechanical properties. The self-assembly of dipeptide-based molecules is reminiscent of pathological amyloid fibril formation by naturally occurring polypeptides. Fluorenylmethoxycarbonyl-diphenylalanine (Fmoc-FF) is the most widely studied such molecule, but the thermodynamic and kinetic phenomena giving rise to Fmoc-FF gel formation remain poorly understood. We have previously presented evidence that the gelation process is a first order phase transition characterized by low energy barriers to nucleation, short induction times, and rapid quasi-one-dimensional crystal growth, stemming from solvent-solute interactions and highly specific molecular packing. Here, we discuss the phase behavior of Fmoc-FF in different solvents. We find that Fmoc-FF gel formation can be induced in apolar solvents, in addition to previously established pathways in aqueous systems. We further show that in certain solvent systems anisotropic crystals (nanofibers) are an initial metastable state, after which macroscopic crystal aggregates with no preferred axis of growth are formed. The molecular conformation is sensitive to solvent composition during assembly, indicating that Fmoc-FF may be a simple model system to study complex thermodynamic and kinetic phenomena involved in peptide self-assembly.

Multifunctional Self-Assembling Peptide-Based Nanostructures for Targeted Intracellular Delivery: Design, Physicochemical Characterization, and Biological Assessment.

Peptide amphiphiles (PAs), consisting of a hydrophobic alkyl chain covalently bound to a hydrophilic peptide sequence, possess a versatile molecular design due to their combined self-assembling features of amphiphile surfactants and biological functionalities of peptides. Through rational design, PAs can self-assemble into a variety of nanostructures with controlled shape, size, and biological functionality to deliver therapeutic and imaging agents to target cells. Here, we describe principles to design multifunctional PAs for self-assembly into micellar nanostructures and targeted intracellular delivery. The PA micelles are designed to display a tumour targeting sequence on their surfaces and direct their interactions with specific cells. This targeting sequence includes an enzymatic sensitive sequence that can be cleaved upon exposure to matrix metalloproteinase 2 (MMP-2), an enzyme overexpressed in tumor environment, allowing the presentation of a cell-penetrating domain. The presentation of this domain will then facilitate the delivery of therapeutics for cancer treatment inside targeted cells. Methods to characterize the key physicochemical properties of PAs and their assemblies, including secondary structure, critical micelle concentration, shape and size, are described in detail. The enzyme responsiveness of PA assemblies is described with respect to their degradation by MMP-2. Protocols to evaluate the cytotoxicity and cellular uptake of the micellar carriers are also included.

Photoluminescent Peptide-Based Nanostructures as FRET Donor for Fluorophore Dye.

A great interest has been recently generated by the discovery that peptide-based nanostructures (NSs) endowed with cross-β structure may show interesting photoluminescent (PL) properties. It was shown that NSs formed by PEGylated hexaphenylalanine (PEG8 -F6, PEG=polyethylene glycol) are able to emit at 460 nm when excited at 370 or 410 nm. Here, the possibility to transfer the fluorescence of these PEG8 -F6-based NSs by foster resonance electron transfer (FRET) phenomenon to a fluorescent dye was explored. To achieve this aim, the 4-chloro-7-nitrobenzofurazan (NBD) dye was encapsulated in these NSs. Structural data in solution and in solid state, obtained by a variety of techniques (circular dichroism, Fourier-transform infrared spectroscopy, wide-angle X-ray scattering, and small-angle X-ray scattering), indicated that the organization of the peptide spine of PEG8 -F6 NS, which consists of anti-parallel β-sheets separated by a dry interface made of interacting phenylalanine side chains, was maintained upon NBD encapsulation. The spectroscopic characterization of these NSs clearly showed a red-shift of the emission fluorescence peak both in solution and in solid state. This shift from 460 to 530 nm indicated that a FRET phenomenon from the peptide-based to the fluorophore-encapsulated NS occurred. FRET could also be detected in the PEG8 -F6 conjugate, in which the NBD was covalently bound to the amine of the compound. On the basis of these results, it is suggested that the red-shift of the intrinsic PL of NSs may be exploited in the bio-imaging field.

A Molecular Dynamics Study on Controlling the Self-Assembly of β-Sheet Peptides with Designer Nanorings.

Recently, a rational approach for constructing β-barrel protein mimics by the self-assembly of peptide-based building blocks has been demonstrated. We performed molecular dynamics simulations of nanoring formation by means of the self-assembly of designed β-sheet-forming peptides. Several factors contributing to the stability of the nanoring structures with respect to size were investigated. Our simulations predicted that an optimal nanoring size may be achieved by minimizing repulsions due to steric hindrance between bulky groups while maintaining favorable hydrogen-bond interactions between neighboring β-sheet chains. It was shown that mutations in a test peptide, in which all or half of the tryptophan residues were replaced by phenylalanine, could enable the assembly of stable nanoring structures with smaller pore sizes. Insights into the fundamental factors driving the formation of peptide-based nanostructures are expected to facilitate the design of novel functional bionanostructures.