Oral gene delivery with cyclo-(D-Trp-Tyr) peptide nanotubes

Exploring Cyclic Peptide Nanotube Stability Across Diverse Lipid Bilayers and Unveiling Water Transport Dynamics

Cyclic Peptide Nanotubes (CPNTs) have emerged as compelling candidates for various applications, particularly as nanochannels within lipid bilayers. In this study, the stability of two CPNTs, namely 8 × [(Cys-Gly-Met-Gly)2] and 8 × [(Gly-Leu)4], are comprehensively investigated across different lipid bilayers, including 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC), a mixed model membrane (POPE/POPG), and a realistic yeast model membrane. The results demonstrate that both CPNTs maintain their tubular structures in all lipid bilayers, with [(Cys-Gly-Met-Gly)2] showing increased stability over an extended period in these lipid membranes. The insertion of CPNTs shows negligible impact on lipid bilayer properties, including area per lipid, volume per lipid, and bilayer thickness. The study demonstrates that the CPNT preserves its two-line water movement pattern within all the lipid membranes, reaffirming their potential as water channels. The MSD curves further reveal that the dynamics of water molecules inside the nanotube are similar for all the bilayer systems with minor differences that arise due to different lipid environments.

Morphological studies of self-assembled cyclotides extracted from Viola odorata as novel versatile platforms in biomedical applications

Self-assembling peptides have attracted researchers' attention recently. They are classified as biomedical materials with unique properties formed in response to environmental conditions. Cyclotides are macrocyclic plant-derived peptides containing 28-37 amino acids that have the ability to self-assemble. Herein, we investigated the effect of pH, time, and temperature on the self-assembling properties of the cyclotides extracted from Viola odorata. For this purpose, the cyclotides were dispersed in aqueous trifluoroacetic acid at pH 2, 4, or 6 and incubated at 25 or 37 °C for 1, 2, 3, 5, 7 or 10 days, and the morphology of the self-assembled structures was identified by optical microscopy, polarized optical microscopy, scanning electron microscopy, transmission electron microscopy, and fluorescence microscopy. At pH 2 and 4, the self-assembly process of cyclotides comprises a number of steps, starting with the formation of spherical peptide nanostructures followed by hierarchically assembled nanotubes, and then shifting to nanofibers after 10 days. At pH 6, amorphous structures were produced even after 10 days. The temperature also could affect the self-assembly mechanism of the cyclotides. At 25 °C, the spherical peptide micelles formed firstly and then merged to form nanotubes, while at 37 °C the cyclotides showed crystallization followed by an increase in length with time. The fluorescence microscopy images showed that the nanotubes could efficiently entrap the hydrophobic molecules of coumarin. This comparative study on the self-assembly of the cyclotides extracted from Viola odorata is the first example exploring the capacity of these cyclotides to adopt precise nanostructures. The nanotubes and nanofibers obtained with these cyclotides might find interesting applications in drug delivery and tissue engineering.

Molecular Self-Assembly and Supramolecular Chemistry of Cyclic Peptides

This Review focuses on the establishment and development of self-assemblies governed by the supramolecular interactions between cyclic peptides. The Review first describes the type of cyclic peptides able to assemble into tubular structures to form supramolecular cyclic peptide nanotubes. A range of cyclic peptides have been identified to have such properties, including α-peptides, β-peptides, α,γ-peptides, and peptides based on δ- and ε-amino acids. The Review covers the design and functionalization of these cyclic peptides and expands to a recent advance in the design and application of these materials through their conjugation to polymer chains to generate cyclic peptide-polymer conjugates nanostructures. The Review, then, concentrates on the challenges in characterizing these systems and presents an overview of the various analytical and characterization techniques used to date. This overview concludes with a critical survey of the various applications of the nanomaterials obtained from supramolecular cyclic peptide nanotubes, with a focus on biological and medical applications, ranging from ion channels and membrane insertion to antibacterial materials, anticancer drug delivery, gene delivery, and antiviral applications.

Amino Acids, Peptides, and Proteins: Implications for Nanotechnological Applications in Biosensing and Drug/Gene Delivery

Over various scientific fields in biochemistry, amino acids have been highlighted in research works. Protein, peptide- and amino acid-based drug delivery systems have proficiently transformed nanotechnology via immense flexibility in their features for attaching various drug molecules and biodegradable polymers. In this regard, novel nanostructures including carbon nanotubes, electrospun carbon nanofibers, gold nanoislands, and metal-based nanoparticles have been introduced as nanosensors for accurate detection of these organic compounds. These nanostructures can bind the biological receptor to the sensor surface and increase the surface area of the working electrode, significantly enhancing the biosensor performance. Interestingly, protein-based nanocarriers have also emerged as useful drug and gene delivery platforms. This is important since, despite recent advancements, there are still biological barriers and other obstacles limiting gene and drug delivery efficacy. Currently available strategies for gene therapy are not cost-effective, and they do not deliver the genetic cargo effectively to target sites. With rapid advancements in nanotechnology, novel gene delivery systems are introduced as nonviral vectors such as protein, peptide, and amino acid-based nanostructures. These nano-based delivery platforms can be tailored into functional transformation using proteins and peptides ligands based nanocarriers, usually overexpressed in the specified diseases. The purpose of this review is to shed light on traditional and nanotechnology-based methods to detect amino acids, peptides, and proteins. Furthermore, new insights into the potential of amino protein-based nanoassemblies for targeted drug delivery or gene transfer are presented.

Synthesis, Characterization and Evaluation of Peptide Nanostructures for Biomedical Applications

There is a challenging need for the development of new alternative nanostructures that can allow the coupling and/or encapsulation of therapeutic/diagnostic molecules while reducing their toxicity and improving their circulation and in-vivo targeting. Among the new materials using natural building blocks, peptides have attracted significant interest because of their simple structure, relative chemical and physical stability, diversity of sequences and forms, their easy functionalization with (bio)molecules and the possibility of synthesizing them in large quantities. A number of them have the ability to self-assemble into nanotubes, -spheres, -vesicles or -rods under mild conditions, which opens up new applications in biology and nanomedicine due to their intrinsic biocompatibility and biodegradability as well as their surface chemical reactivity via amino- and carboxyl groups. In order to obtain nanostructures suitable for biomedical applications, the structure, size, shape and surface chemistry of these nanoplatforms must be optimized. These properties depend directly on the nature and sequence of the amino acids that constitute them. It is therefore essential to control the order in which the amino acids are introduced during the synthesis of short peptide chains and to evaluate their in-vitro and in-vivo physico-chemical properties before testing them for biomedical applications. This review therefore focuses on the synthesis, functionalization and characterization of peptide sequences that can self-assemble to form nanostructures. The synthesis in batch or with new continuous flow and microflow techniques will be described and compared in terms of amino acids sequence, purification processes, functionalization or encapsulation of targeting ligands, imaging probes as well as therapeutic molecules. Their chemical and biological characterization will be presented to evaluate their purity, toxicity, biocompatibility and biodistribution, and some therapeutic properties in vitro and in vivo. Finally, their main applications in the biomedical field will be presented so as to highlight their importance and advantages over classical nanostructures.

Assessment of the Oral Delivery of a Myelin Basic Protein Gene Promoter with Antiapoptotic bcl-xL (pMBP-bcl-xL) DNA by Cyclic Peptide Nanotubes with Two Aspect Ratios and Its Biodistribution in the Brain and Spinal Cord

Cyclo-(D-Trp-Tyr) peptide nanotubes (PNTs) were reported to be potential carriers for oral gene delivery in our previous study; however, the effect of the aspect ratio (AR) of these PNTs on gene delivery in vivo could affect penetration or interception in biological environments. The aim of this study was to assess the feasibility of cyclo-(D-Trp-Tyr) PNTs with two ARs as carriers for oral pMBP-bcl-x_L-hRluc delivery to the spinal cord to treat spinal cord injury (SCI). We evaluated the biodistribution of oligodendrocyte (OLG)-specific myelin basic protein gene promoter-driven antiapoptotic DNA (pMBP-bcl-x_L) to the brain and spinal cord delivered with cyclo-(D-Trp-Tyr) PNTs with large (L) and small (S) PNTs with two ARs. After complex formation, the length, width, and AR of the L-PNTs/DNA were 77.86 ± 3.30, 6.51 ± 0.28, and 13.75 ± 7.29 μm, respectively, and the length and width of the S-PNTs/DNA were 1.17 ± 0.52 and 0.17 ± 0.05 μm, respectively, giving an AR of 7.12 ± 3.17 as detected by scanning electron microscopy. Each of these three parameters exhibited significant differences (p < 0.05) between L-PNTs/DNA and S-PNTs/DNA. However, there were no significant differences (p > 0.05) between the L-PNTs and S-PNTs for either their DNA encapsulation efficiency (29.72 ± 14.19 and 34.31 ± 16.78%, respectively) or loading efficiency (5.15 ± 2.58 and 5.95 ± 2.91%). The results of the in vitro analysis showed that the S-PNT/DNA complexes had a significantly higher DNA release rate and DNA permeation in the duodenum than the L-PNT/DNA complexes. Using Cy5 and TM-rhodamine to individually and chemically conjugate the PNTs with plasmid DNA, we observed, using laser confocal microscopy, that the PNTs and DNA colocalized in complexes. We further confirmed the complexation between DNA and the PNTs using fluorescence resonance energy transfer (FRET). Data from an in vivo imaging system (IVIS) showed that there was no significant difference (p > 0.05) in PNT distribution between L-PNTs/DNA and S-PNTs/DNA within 4 h. However, the S-PNT/DNA group had a significantly higher DNA distribution (p < 0.05) in several organs, including the ilium, heart, lungs, spleen, kidneys, testes, brain, and spinal cord. Finally, we determined the bcl-x_L protein expression levels in the brain and spinal cord regions for the L-PNT/DNA and S-PNT/DNA complex formulations. These results suggested that either L-PNTs or S-PNTs may be used as potential carriers for oral gene delivery to treat SCI.

Peptide-Based Nanoassemblies in Gene Therapy and Diagnosis: Paving the Way for Clinical Application

Nanotechnology approaches play an important role in developing novel and efficient carriers for biomedical applications. Peptides are particularly appealing to generate such nanocarriers because they can be rationally designed to serve as building blocks for self-assembling nanoscale structures with great potential as therapeutic or diagnostic delivery vehicles. In this review, we describe peptide-based nanoassemblies and highlight features that make them particularly attractive for the delivery of nucleic acids to host cells or improve the specificity and sensitivity of probes in diagnostic imaging. We outline the current state in the design of peptides and peptide-conjugates and the paradigms of their self-assembly into well-defined nanostructures, as well as the co-assembly of nucleic acids to form less structured nanoparticles. Various recent examples of engineered peptides and peptide-conjugates promoting self-assembly and providing the structures with wanted functionalities are presented. The advantages of peptides are not only their biocompatibility and biodegradability, but the possibility of sheer limitless combinations and modifications of amino acid residues to induce the assembly of modular, multiplexed delivery systems. Moreover, functions that nature encoded in peptides, such as their ability to target molecular recognition sites, can be emulated repeatedly in nanoassemblies. Finally, we present recent examples where self-assembled peptide-based assemblies with "smart" activity are used in vivo. Gene delivery and diagnostic imaging in mouse tumor models exemplify the great potential of peptide nanoassemblies for future clinical applications.

A molecular dynamics investigation on transporting mechanism of glucose through a cyclic peptide nanotube

Cyclic peptide nanotubes (CPNTs) are open-ended, hollow, and tubular structures that are made of several cyclic peptide rings. These structures can act as a transmembrane channel and transport ions or small molecules. In this work, we studied the stability of a cyclic peptide nanotube 8 × [(Trp-D-Leu)4-Gln-D-Leu] into a fully hydrated membrane composed of DPPC/POPC/POPS/cholesterol and also the transport mechanism of β-D-glucose through this nanotube was investigated. Our findings revealed that the CPNT was stable in the lipid bilayer during the simulation time and non-bonded interactions, especially hydrogen bonding have an important role to form a stable CPNT in the membrane. The glucose jumps from a Cα-region into the mid-Cα region and spends more time in this region because of its more desirable interactions with water molecules and the CPNT. In the transport pathway, non-bonded interactions between glucose, water molecules and the CPNT facilitate the transport of the glucose through the CPNT. The collaboration of hydrogen bonds, electrostatic and van der Waals interactions change the pulling force and lead to transport glucose through the CPNT. Potential of mean force (PMF) calculations revealed that the glucose has a minimum value of binding free energy and maximum configurational entropy in MPR regions. These findings can be used to design more CPNTs with different goals such as drug delivery.Communicated by Ramaswamy H. Sarma.

Soft-Matter Nanotubes: A Platform for Diverse Functions and Applications

Self-assembled organic nanotubes made of single or multiple molecular components can be classified into soft-matter nanotubes (SMNTs) by contrast with hard-matter nanotubes, such as carbon and other inorganic nanotubes. To date, diverse self-assembly processes and elaborate template procedures using rationally designed organic molecules have produced suitable tubular architectures with definite dimensions, structural complexity, and hierarchy for expected functions and applications. Herein, we comprehensively discuss every functions and possible applications of a wide range of SMNTs as bulk materials or single components. This Review highlights valuable contributions mainly in the past decade. Fifteen different families of SMNTs are discussed from the viewpoints of chemical, physical, biological, and medical applications, as well as action fields (e.g., interior, wall, exterior, whole structure, and ensemble of nanotubes). Chemical applications of the SMNTs are associated with encapsulating materials and sensors. SMNTs also behave, while sometimes undergoing morphological transformation, as a catalyst, template, liquid crystal, hydro-/organogel, superhydrophobic surface, and micron size engine. Physical functions pertain to ferro-/piezoelectricity and energy migration/storage, leading to the applications to electrodes or supercapacitors, and mechanical reinforcement. Biological functions involve artificial chaperone, transmembrane transport, nanochannels, and channel reactors. Finally, medical functions range over drug delivery, nonviral gene transfer vector, and virus trap.

Strategic use of nanotechnology in drug targeting and its consequences on human health: A focused review

Since the development of first lipid-based nanocarrier system, about 15% of the present pharmaceutical market uses nanomedicines to achieve medical benefits. Nanotechnology is an advanced area to meliorate the delivery of compounds for improved medical diagnosis and curing disease. Nanomedicines are gaining significant interest due to the ultra small size and large surface area to mass ratio. In this review, we discuss the potential of nanotechnology in delivering of active moieties for the disease therapy including their toxicity evidences. This communication will help the formulation scientists in understanding and exploring the new aspects of nanotechnology in the field of nanomedicine.

Applications of cyclic peptide nanotubes (cPNTs)

Self-assembled cyclic peptide nanotubes (cPNTs) have recently drawn particular attention as one of the most intriguing nanostructures in the field of nanotechnology. Given their unique features including high surface area, increased drug loading, environmental stability, enhanced permeation, and modifiable drug release, these hollow tubular structures can be constructed with cyclic di-, tri-, tetra-, hexa-, octa-, and decapeptides with various amino acid sequences, enantiomers, and functionalized side chains and can be applied for antiviral and antibacterial drugs, drug delivery and gene delivery vectors, organic electronic devices, and ionic or molecular channels. Recent publications have presented promising results regarding the use of cPNTs as drugs or biomedical devices. However, there is an urgent need for the further in vivo nanotoxicity and safety testing of these nanotubes to evaluate their suitability in different fields.

Supramolecular functional assemblies: dynamic membrane transporters and peptide nanotubular composites

The fabrication of functional molecular devices constitutes one of the most important current challenges for chemical sciences. The complex processes accomplished by living systems continuously demand the assistance of non-covalent interactions between molecular building blocks. Additionally, these building blocks (proteins, membranes, nucleotides) are also constituted by self-assembled structures. Therefore, supramolecular chemistry is the discipline required to understand the properties of the minimal self-assembled building blocks of living systems and to develop new functional smart materials. In the first part of this feature article, we highlight selected examples of the preparation of supramolecular membrane transporters with special emphasis on the application of dynamic covalent bonds. In the second section of the paper we review recent breakthroughs in the preparation of peptide nanotube hybrids with functional applications. The development of these devices constitutes an exciting process from where we can learn how to understand and manipulate supramolecular functional assemblies.

Recent advances in controlling the internal and external properties of self-assembling cyclic peptide nanotubes and dimers

Tuning the internal and external properties of self-assembling cyclic peptide nanotubes.

Non-viral gene therapy: Gains and challenges of non-invasive administration methods

Gene therapy is becoming an influential part of the rapidly increasing armamentarium of biopharmaceuticals for improving health and combating diseases. Currently, three gene therapy treatments are approved by regulatory agencies. While these treatments utilize viral vectors, non-viral alternative technologies are also being developed to improve the safety profile and manufacturability of gene carrier formulations. We present an overview of gene-based therapies focusing on non-viral gene delivery systems and the genetic therapeutic tools that will further revolutionize medical treatment with primary focus on the range and development of non-invasive delivery systems for dermal, transdermal, ocular and pulmonary administrations and perspectives on other administration methods such as intranasal, oral, buccal, vaginal, rectal and otic delivery.

Anti-Apoptotic Gene Delivery with cyclo-(d-Trp-Tyr) Peptide Nanotube via Eye Drop Following Corneal Epithelial Debridement

Corneal keratocyte apoptosis triggered by cornel debridement is one mechanism of corneal disorders. In this study, the feasibility of cyclo-(d-Trp-Tyr) peptide nanotubes (PNTs) as carriers of caspase 3 silence shRNA delivery was assessed. A model of epithelial injury by epithelial debridement was applied to investigate the feasibility of PNTs as gene delivery carriers on corneal injury. First, the PNTs were found within 2 μm in length and 300 nm in width by an atomic force microscope and confocal laser microscope system. Plasmid DNAs were observed to be associated with PNTs by atomic force microscope and confocal laser scanning microscope. The plasmids were associated with tyrosine of PNTs with a binding constant of 2.7 × 108 M-1. The stability of plasmid DNA with PNTs against the DNase was found at 60 min. Using thioflavin T pre-stained PNTs on the corneal eye drop delivery, the distribution of PNTs was in the epithelial and stroma regions. After corneal debridement, the rhodamine-labeled plasmid DNA and thioflavin T pre-stained PNTs were also delivered and could be observed in the stroma of cornea. PNTs complexed with anti-apoptotic plasmid caspase 3 silencing shRNA eye drop delivery decreased 41% of caspase 3 activity after the first dose by caspase 3 activity and Western blot analysis.

Effects of PEGylation on the physicochemical properties and in vivo distribution of organic nanotubes

Application of organic nanotubes (ONTs) into drug nanocarriers ultimately requires validation in live animals. For improving the dispersibility in biological media and in vivo distribution, the outer surface of an ONT was functionalized with polyethylene glycol (PEG) via the coassembly of an ONT-forming lipid with 5-20 mol% of a PEG-tethered lipid analogue (PEG-lipid). Firstly, the effect of PEGylation on the psysicochemical properties of ONTs, such as morphology and dispersibility, was investigated. PEGylation of ONTs slightly reduced the average length and effectively prevented the aggregation in phosphate-buffered saline (PBS). The PEGylated ONTs even showed high thermal stability in aqueous dispersion at least up to 95°C. Secondly, differential scanning calorimetry and powder X-ray diffraction indicated that ~10 mol% of PEG-lipid was completely incorporated into the ONTs, while 20 mol% of PEG-lipid encountered a partial phase separation during coassembly. In the heating differential scanning calorimetry runs, the resultant PEGylated ONTs with 5 mol% PEG-lipid showed no sign of phase separation up to 180°C under lyophilized condition, while those with 10 mol% and 20 mol% PEG-lipid showed some phase separation of the PEG-lipid above 120°C. Finally, PEGylation significantly affected the tissue distribution and prolonged the persistence time in the blood in mice. Non-PEGylated ONTs was quickly cleared from the circulation after intravenous infusion and preferentially accumulated in the lung, while PEGylated ONTs was mainly trapped in the liver and could circulate in the blood up to 24 hours. This study provided valuable information of physicochemical properties and the in vivo distribution behavior of PEGylated ONTs for their potential application into drug nanocarriers.

Evaluation of progesterone permeability from supercritical fluid processed dispersion systems

The aim of this study was to investigate the permeability of unique dispersion systems prepared by supercritical fluid (SCF) processing, to deliver bioidentical progesterone (PGN) across mouse skin. Semisolid dispersions of PGN were made up of either polyethylene glycol (PEG) 400/4000, Gelucire 44/14, d-α-tocopheryl PEG 1000 succinate (TPGS), tanscutol P or myritol 318. SCF dispersion systems were compared with various control formulations; a market cream, aqueous suspension, and three conventionally prepared dispersions – comelted, cosolvent and physically mixed systems. The permeability coefficient in the absence or presence of a permeation enhancer was evaluated using ex vivo mouse skin. The permeation study results for the TPGS/myritol/transcutol P dispersion system prepared using supercritical carbon dioxide (SC-CO2) had a two-fold improvement in transdermal permeation over 24 h compared to the control formulation, 245.7 and 126 µg cm(-2), respectively (p value < 0.05). In this study, the skin integrity and morphology was also investigated for changes due to the formulation constituents using histological examination and Fourier transform infrared spectroscopy. The particles from the gas-saturated suspension method and SC-CO2 together with TPGS/myritol/transcutol P may offer potential advantages over the available cream on the market based on the vastly improved lag time and flux of PGN across the skin.

Biological applications of peptides nanotubes: an overview

Recently, self-assemblies of peptide nanotubes (PNTs) have appeared as one of the most interesting nanostructures to be explored in the field of nanotechnology. These smart assemblies can have diverse applications, such as in the design of nanoreactors, sensors, electronics, and stimulus-responsive materials. Recent publications indicate that PNT synthesis and production are under extensive study. However, a more detailed safety and nanotoxicology evaluation of these materials is still necessary. This is of paramount importance since interesting and novel biomedical applications based on the use of PNTs, including the development of smart nanodevices and drug delivery systems, are under way. To this end, the aim of this mini-review is to discuss the recent biomedical applications of PNTs and, it hopes, to be a source of inspiration for researchers in different areas of expertise related to nanotechnology.