Biomimetic organization: Octapeptide self-assembly into nanotubes of viral capsid-like dimension

Partial AUCs in Long-Acting Injectables: Rationale, Challenges, Variability, Usefulness, and Clinical Relevance

Regulatory authorities typically require bioequivalence to be demonstrated by comparing pharmacokinetic parameters like area under the plasma concentration-time curve (AUC) and maximum plasma concentration (Cmax). Because in certain cases, AUC and Cmax alone may not be adequate to identify formulation differences in early and/or late segments of the dosing interval, partial AUCs (pAUCs) have been proposed as additional metrics to evaluate bioequivalence. Even though cut-off points for pAUCs are usually decided based on clinical relevance, the identification of the correct cut-off range remains elusive in many other cases and tends to contribute to increased pAUC estimate variabilities. The choice of meaningful cut-off points in pAUC estimates can be especially difficult in the case of long-acting injectable (LAI) products, where long dosing intervals and complex pharmacokinetic (PK) and pharmacodynamic (PD) profiles apply, but most importantly, because there is not always a clear PK/PD relationship established. In this communication, authors discuss the usefulness and challenges associated with the estimation of pAUCs in the development of generic LAI products through the review of six case studies under the lens of regulatory requirements from the two major authorities, namely the FDA and EMA.

Liquid Crystal Behavior of Uniform Short Rods Made from Computationally Designed Parallel Coiled Coil Building Blocks

Parallel, homotetrameric coiled coils were computationally designed using 29 amino acid peptides. These parallel coiled coils, called "bundlemers", have C2 symmetry, with all N-termini displayed from one end of the nanoparticle and all C-termini from the opposite end. This anisotropic display of the peptide termini allowed for the functionalization of two sets of nanoparticles with either maleimide or thiol functionality at the N-terminal region of the constituent peptides. The thiol-Michael conjugation reaction between the N-terminal end of complementary bundlemer nanoparticles formed monodisperse, rigid bundlemer dimer, called "dibundlemer", rods. The constituent, individual bundlemer nanoparticles were characterized with small-angle X-ray scattering (SAXS), Förster resonance energy transfer (FRET), and circular dichroism (CD) spectroscopy to confirm the parallel assembly of the coiled coils, consistent with the computational design. The dibundlemer rods were characterized with SAXS to reveal the uniform dibundlemer nature of the rods. Optical birefringence is observed in concentrated samples of the rods, with polarized optical microscopy (POM) revealing a nematic liquid crystalline behavior.

Long-Acting Antibacterial Hydrogels Constructed by Interface-Induced Directional Assembly

Self-assembled supermolecular hydrogels of therapeutic agents without structural modification are of great significance in biomedical applications. Nevertheless, the complex conformations and elusive interactions of therapeutic molecules limit the controlled assembly of hydrogels. Molecules at the interface might have different arrangements and assemblies compared to those in bulk aqueous solution, which could potentially alter the selectivity of supramolecular polymorphs. However, this effect is still not well understood. Here, we demonstrate the interface-induced self-assembly of fibers for hydrogels, which is distinct from the spherical aggregates in the bulk aqueous solution, using cephradine (CEP) as a model compound. This phenomenon is caused by the packing of anisotropic molecules at the interface, and it can be applied to control the supramolecular polymorphism for the direct self-assembly of hydrogels of therapeutic agents. The interface-induced hydrogel exhibits a high degree of adjustable release and a long-acting bactericidal effect.

Quantitative analysis of therapeutic peptides by CZE using multiple sample injection in hydrodynamically closed separation system

Therapeutic peptides have emerged as an innovative and promising class of therapeutic compounds in modern medicine. Synthetic peptide analogs triptorelin and lanreotide are known for their pronounced clinical versatility and potency. In this study, we present the development and validation of novel methods based on capillary zone electrophoresis performed in hydrodynamically closed system (HCS) and paired with ultraviolet detection and repeated injection sample introduction. To the best of our knowledge, we developed the first capillary electrophoresis-based method for the determination of lanreotide, and concurrently, the first HCS method for the determination of triptorelin. Maximal separation efficiency and signal intensity were achieved using background electrolytes composed of 50 mM formic acid with the addition of 0.05% (v/v) methyl-hydroxyethyl cellulose. The proposed methods exhibit favorable performance characteristics, namely, calibration curve (r2 exceeding 0.99), low limits of detection (0.25 µg/mL in a water matrix and 0.5 µg/mL in synthetic urine), acceptable precision (relative standard deviation ranging from 2.2% to 9.6% for intraday repeatability and between 5.2% and 14.9% for interday reproducibility), and accuracy (relative errors falling within the 91.1%-107.8% range). The method for triptorelin determination was then used for its quantification in a commercially available drug dosage form (powder for injection) and in spiked synthetic urine samples. The developed methods were also evaluated according to the novel blue applicability grade index, revealing their superior applicability. The results collectively point out the potential of the proposed methods for both quality control and clinical investigations.

Advances in MRI: Peptide and peptidomimetic-based contrast agents

Magnetic resonance imaging (MRI) is a common medical imaging technique that provides three-dimensional body images. MRI contrast agents improve image contrast by raising the rate of water proton relaxation in specific tissues. Peptides and peptidomimetics act as scaffolds for MRI imaging agents because of their increased size and offer the possibility to engine a higher hydration value within the design. The design of a new Gd-based contrast agent must take into account high stability constants to avoid free Gd(III), with the subsequent nephrotoxicity, and high relaxivity values. This review analyzes various synthetic approaches, reports studies of relaxometric parameters, and focuses on the description and application of Gd(III)-chelates based on peptide and peptidomimetic scaffolds. In addition, the X-ray molecular structures of three DOTA complexes will be reported to emphasize the necessity of using the X-ray diffraction analysis to identify the coordination sphere of the metals and the mechanism of action of the compounds.

Investigating the complexation propensity of self-assembling dipeptides with the anticancer peptide-drug Bortezomib: a computational study

The investigation of potential self-assembled peptides as carriers for the delivery of anticancer drug Bortezomib is the topic of the present study. The self-assembly of Bortezomib in water is examined using all-atom molecular dynamics simulations and corresponding experimental results from FESEM experiments. In addition, a series of dipeptides with a similar chemical formula to Bortezomib with hydrogel-forming ability are being investigated for their propensity to bind to the drug molecule. Dipeptides are divided into two classes, the protected FF (Fmoc-FF and Z-FF) and the LF-based (Cyclo-LF and LF) ones. The thermodynamic stability of the complexes formed in an aqueous environment, as well as key morphological features of the nanoassemblies are investigated at the molecular level. Binding enthalpy between Bortezomib and dipeptides follows the increasing order: LF < Cyclo-LF < Fmoc-FF < Z-FF under both van der Waals and electrostatic contributions. Protected FF dipeptides have a higher affinity for the drug molecule, which will favor its entrapment, giving them an edge over the LF based dipeptides. By evaluating the various measures, regarding both the binding between the two components and the eventual ability of controlled drug release, we conclude that the protected FF class is a more suitable candidate for drug release of Bortezomib, whereas among its two members, Fmoc-FF appears to be more promising. The selection of the optimal candidates based on the present computational study will be a stepping stone for future detailed experimental studies involving the encapsulation and controlled release of Bortezomib both in vitro and in vivo.

Enantiomeric Virus-Inspired Oncolytic Particles for Efficient Antitumor Immunotherapy

Synthesizing biomimetic systems with stereospecific architectures and advanced bioactivity remains an enormous challenge in modern science. To fundamentally eliminate biosafety issues of natural oncolytic viruses, the development of synthetic virus-inspired particles with high oncolytic activity is urgently needed for clinical antitumor treatments. Here, we describe the design and synthesis of enantiomeric virus-inspired particles for efficient oncolytic therapy from homochiral building blocks to stereospecific supramolecular constructions. The L-virus-inspired oncolytic particles (L-VOPs) and D-VOPs possess similar biomimetic nanostructures but mirror-imaged enantiomeric forms. It is important that both L-VOPs and D-VOPs successfully mimic the pharmacological activity of oncolytic viruses, including direct tumor lysis and antitumor immune activation. D-VOPs provide quite better oncolytic efficacy than that of clinical-grade oncolytic agents (LTX-315, IC50 = 53.00 μg mL-1) with more than 5-fold decrease in IC50 value (10.93 μg mL-1) and close to 100% tumor suppression (98.79%) against 4T1 tumor-bearing mice, attributed to the chirality-dependent tumor recognition, interaction, antidegradation, and immunotherapy. This work provides a strategy for the synthesis of stereospecific biomimetic material systems as well as develops an advanced candidate for biomimetic oncolytic agents without biosafety risks.

Small-angle scattering techniques for peptide and peptide hybrid nanostructures and peptide-based biomaterials

The use of small-angle scattering (SAS) in the study of the self-assembly of peptides and peptide conjugates (lipopeptides, polymer-peptide conjugates and others) is reviewed, highlighting selected research that illustrates different methods and analysis techniques. Both small-angle x-ray scattering (SAXS) and small-angle neutron scattering (SANS) are considered along with examples that exploit their unique capabilities. For SAXS, this includes the ability to perform rapid measurements enabling high throughput or fast kinetic studies and measurements under dilute conditions. For SANS, contrast variation using H2O/D2O mixtures enables the study of peptides interacting with lipids and TR-SANS (time-resolved SANS) studies of exchange kinetics and/or peptide-induced structural changes. Examples are provided of studies measuring form factors of different self-assembled structures (micelles, fibrils, nanotapes, nanotubes etc) as well as structure factors from ordered phases (lyotropic mesophases), peptide gels and hybrid materials such as membranes formed by mixing peptides with polysaccharides or peptide/liposome mixtures. SAXS/WAXS (WAXS: wide-angle x-ray scattering) on peptides and peptide hybrids is also discussed, and the review concludes with a perspective on potential future directions for research in the field.

Cysteine Redox Chemistry in Peptide Self-Assembly to Modulate Hydrogelation

Cysteine redox chemistry is widely used in nature to direct protein assembly, and in recent years it has inspired chemists to design self-assembling peptides too. In this concise review, we describe the progress in the field focusing on the recent advancements that make use of Cys thiol-disulfide redox chemistry to modulate hydrogelation of various peptide classes.

Compressional stress stiffening & softening of soft hydrogels - how to avoid artefacts in their rheological characterisation

Hydrogels have been successfully employed as analogues of the extracellular matrix to study biological processes such as cells' migration, growth, adhesion and differentiation. These are governed by many factors, including the mechanical properties of hydrogels; yet, a one-to-one correlation between the viscoelastic properties of gels and cell fate is still missing from literature. In this work we provide experimental evidence supporting a possible explanation for the persistence of this knowledge gap. In particular, we have employed common tissues' surrogates such as polyacrylamide and agarose gels to elucidate a potential pitfall occurring when performing rheological characterisations of soft-materials. The issue is related to (i) the normal force applied to the samples prior to performing the rheological measurements, which may easily drive the outcomes of the investigation outside the materials' linear viscoelastic regime, especially when tests are performed with (ii) geometrical tools having unbefitting dimensions (i.e., too small). We corroborate that biomimetic hydrogels can show either compressional stress softening or stiffening, and we provide a simple solution to quench these undesired phenomena, which would likely lead to potentially misleading conclusions if they were not mitigated by a good practice in performing rheological measurements, as elucidated in this work.

Design, synthesis, and characterization of protein origami based on self-assembly of a brick and staple artificial protein pair

A versatile strategy to create an inducible protein assembly with predefined geometry is demonstrated. The assembly is triggered by a binding protein that staples two identical protein bricks together in a predictable spatial conformation. The brick and staple proteins are designed for mutual directional affinity and engineered by directed evolution from a synthetic modular repeat protein library. As a proof of concept, this article reports on the spontaneous, extremely fast and quantitative self-assembly of two designed alpha-repeat (αRep) brick and staple proteins into macroscopic tubular superhelices at room temperature. Small-angle X-ray scattering (SAXS) and transmission electron microscopy (TEM with staining agent and cryoTEM) elucidate the resulting superhelical arrangement that precisely matches the a priori intended 3D assembly. The highly ordered, macroscopic biomolecular construction sustains temperatures as high as 75 °C thanks to the robust αRep building blocks. Since the α-helices of the brick and staple proteins are highly programmable, their design allows encoding the geometry and chemical surfaces of the final supramolecular protein architecture. This work opens routes toward the design and fabrication of multiscale protein origami with arbitrarily programmed shapes and chemical functions.

Metallogels: a novel approach for the nanostructuration of single-chain magnets

In this study we demonstrate that single-chain magnets (SCMs) can be assembled in gel phase and transferred intact on surface. We take advantage of a family of SCMs based on Tb^III ions and nitronyl-nitroxides radicals functionalized with short alkyl chains known to form crystalline supramolecular nanotubes interacting with heptane acting as crystallizing solvent. When the radicals are functionalized with long aliphatic chains a robust gel is formed with similar structural and functional properties respect to its crystalline parent. Indeed, a small-angle X-ray scattering (SAXS) study unambiguously demonstrates that the gel is made of supramolecular nanotubes: the high stability of the gel allows the determination from SAXS data of precise nanotube metrics such as diameter, helical pitch and monoclinic cell of the folded 2D crystal lattice along the tube direction. Additionally, static and dynamic magnetic investigations show the persistence of the SCM behavior in the metallogel. Last, on-surface gelation provides thick films as well as sub-monolayer deposits of supramolecular nanotubes on surface as evidenced by atomic force microscopy (AFM) observations. This paves the road toward magnetic materials and devices made of SCMs profiting of their isolation on surface as individual chains.

Cell Adhesion Motif-Functionalized Lipopeptides: Nanostructure and Selective Myoblast Cytocompatibility

The conformation and self-assembly of four lipopeptides, peptide amphiphiles comprising peptides conjugated to lipid chains, in aqueous solution have been examined. The peptide sequence in all four lipopeptides contains the integrin cell adhesion RGDS motif, and the cytocompatibility of the lipopeptides is also analyzed. Lipopeptides have either tetradecyl (C₁₄, myristyl) or hexadecyl (C₁₆, palmitoyl) lipid chains and peptide sequence WGGRGDS or GGGRGDS, that is, with either a tryptophan-containing WGG or triglycine GGG tripeptide spacer between the bioactive peptide motif and the alkyl chain. All four lipopeptides self-assemble above a critical aggregation concentration (CAC), determined through several comparative methods using circular dichroism (CD) and fluorescence. Spectroscopic methods [CD and Fourier transform infrared (FTIR) spectroscopy] show the presence of β-sheet structures, consistent with the extended nanotape, helical ribbon, and nanotube structures observed by cryogenic transmission electron microscopy (cryo-TEM). The high-quality cryo-TEM images clearly show the coexistence of helically twisted ribbon and nanotube structures for C₁₄-WGGRGDS, which highlight the mechanism of nanotube formation by the closure of the ribbons. Small-angle X-ray scattering shows that the nanotapes comprise highly interdigitated peptide bilayers, which are also present in the walls of the nanotubes. Hydrogel formation was observed at sufficiently high concentrations or could be induced by a heat/cool protocol at lower concentrations. Birefringence due to nematic phase formation was observed for several of the lipopeptides, along with spontaneous flow alignment of the lyotropic liquid crystal structure in capillaries. Cell viability assays were performed using both L929 fibroblasts and C2C12 myoblasts to examine the potential uses of the lipopeptides in tissue engineering, with a specific focus on application to cultured (lab-grown) meat, based on myoblast cytocompatibility. Indeed, significantly higher cytocompatibility of myoblasts was observed for all four lipopeptides compared to that for fibroblasts, in particular at a lipopeptide concentration below the CAC. Cytocompatibility could also be improved using hydrogels as cell supports for fibroblasts or myoblasts. Our work highlights that precision control of peptide sequences using bulky aromatic residues within "linker sequences" along with alkyl chain selection can be used to tune the self-assembled nanostructure. In addition, the RGDS-based lipopeptides show promise as materials for tissue engineering, especially those of muscle precursor cells.

Emergence of Elastic Properties in a Minimalist Resilin-Derived Heptapeptide upon Bromination

Bromination is herein exploited to promote the emergence of elastic behavior in a short peptide-SDSYGAP-derived from resilin, a rubber-like protein exerting its role in the jumping and flight systems of insects. Elastic and resilient hydrogels are obtained, which also show self-healing behavior, thanks to the promoted non-covalent interactions that limit deformations and contribute to the structural recovery of the peptide-based hydrogel. In particular, halogen bonds may stabilize the β-sheet organization working as non-covalent cross-links between nearby peptide strands. Importantly, the unmodified peptide (i.e., wild type) does not show such properties. Thus, SDSY(3,5-Br)GAP is a novel minimalist peptide elastomer.

Designer peptides as versatile building blocks for functional materials

Peptides and pseudopeptides show distinct self-assembled nanostructures such as fibers, nanotubes, vesicles, micelles, toroids, helices and rods. The formation of such molecular communities through the collective behavior of molecules is not fully understood at a molecular level. All these self-assembled nanostructured materials have a wide range of applications such as drug delivery, gene delivery, biosensing, bioimaging, catalysis, tissue engineering, nano-electronics and sensing. Self-assembly is one of the most efficient and a simple strategy to generate complex functional materials. Owing to its significance, the last few decades witnessed a remarkable advancement in the field of self-assembling peptides with a plethora of new designer synthetic systems being discovered. These systems range from amphiphilic, cyclic, linear and polymeric peptides. This article presents only selected examples of such self-assembling peptides and pseudopeptides.

The industrial design, translation, and development strategies for long-acting peptide delivery

INTRODUCTION

Peptides are widely recognized as therapeutic agents in the treatment of a wide range of diseases, such as cancer, diabetes etc. However, their use has been limited by their short half-life, due to significant metabolism by exo- and endo-peptidases as well as their inherent poor physical and chemical stability. Research with the aim of improving their half-life in the body, and thus improving patient compliance (by decreasing the frequency of injections) has gained significant attention.

AREAS COVERED

This review outlines the current landscape and industrial approaches to achieve extended peptide exposure and reduce dosing frequency. Emphasis is placed on identifying challenges in drug product manufacturing and desirable critical quality attributes that are essential for activity and safety, providing insights into chemistry and design aspects impacting peptide release, and summarizing important considerations for CMC developability assessments of sustained release peptide drugs.

EXPERT OPINION

Bring the patient and disease perspective early into development. Substantial advances have been made in the field of sustained delivery of peptides despite their complexity. The article will also highlight considerations for early-stage product design and development, providing an industrial perspective on risk mitigation in developing sustained release peptide drug products.

Aromatic interactions directing peptide nano-assembly

Self-assembly is a process of spontaneous organization of molecules as a result of non-covalent interactions. Organized self-assembly at the nano level is emerging as a powerful tool in the bottom-up fabrication of functional nanostructures for targeted applications. Aromatic π-π stacking plays a significant role by facilitating the persistent supramolecular association of individual subunits to the self-assembled structures of high stability. Understanding, the supramolecular chemistry of the materials interacting through aromatic interactions, is of tremendous interest in not only constructing functional materials but also in revealing the mechanism of molecular assembly in living organisms. This chapter aims to focus on understanding the potential role of π-π interactions in directing and regulating the self-assembly of peptide nanostructures. The scope of the chapter starts with an outline of the history and mechanism of the aromatic π-π interactions. It progresses through the design strategy for the assembly of peptides containing aromatic rings, the conditions affecting the aromatic stacking interactions, their resulting nanoassemblies, properties, and applications. The properties and applications of the supramolecular materials formed through the aromatic stacking interactions are highlighted to provide an increased understanding of the role of weak interactions in the design and construction of novel functional materials.

Recent Updates on Supramolecular-Based Drug Delivery - Macrocycles and Supramolecular Gels

Supramolecules-based drug delivery has attracted significant recent research attention as it could enhance drug solubility, retention time, targeting, and stimuli responsiveness. Among the different supramolecules and assemblies, the macrocycles and the supramolecular hydrogels are the two important categories investigated to a greater extent. Here, we provide the most recent advancements in these categories. Under macrocycles, reports on drug delivery by cyclodextrins, cucurbiturils, calixarenes/pillararenes, crown ethers and porphyrins are detailed. The second category discusses the supramolecular hydrogels of macrocycles/polymers and low molecular weight gelators. The updated information provided could be helpful to advance R & D in this vital area.

Structures of synthetic helical filaments and tubes based on peptide and peptido-mimetic polymers

Synthetic peptide and peptido-mimetic filaments and tubes represent a diverse class of nanomaterials with a broad range of potential applications, such as drug delivery, vaccine development, synthetic catalyst design, encapsulation, and energy transduction. The structures of these filaments comprise supramolecular polymers based on helical arrangements of subunits that can be derived from self-assembly of monomers based on diverse structural motifs. In recent years, structural analyses of these materials at near-atomic resolution (NAR) have yielded critical insights into the relationship between sequence, local conformation, and higher-order structure and morphology. This structural information offers the opportunity for development of new tools to facilitate the predictable and reproduciblede novodesign of synthetic helical filaments. However, these studies have also revealed several significant impediments to the latter process – most notably, the common occurrence of structural polymorphism due to the lability of helical symmetry in structural space. This article summarizes the current state of knowledge on the structures of designed peptide and peptido-mimetic filamentous assemblies, with a focus on structures that have been solved to NAR for which reliable atomic models are available.

Atomic structure of Lanreotide nanotubes revealed by cryo-EM

The spectacular developments in cryoelectron microscopy involving new cameras, new microscopes, and new software make it possible today to routinely determine the atomic structures of a large range of molecular assemblies. This has allowed us to solve the atomic structure of nanotubes formed from a peptide, Lanreotide. Its gel, Somatuline, is used as a synthetic growth hormone inhibitor in the treatment of both acromegaly and cancers. The self-assembled nanotube results in a slow release form of the peptide, important pharmacologically. The nanotube structure shows an unexpected complexity and highlights the still unpredictable chemical and physicochemical determinants driving peptide self-assembly.

Functional and versatile nano- and microassemblies formed by biological molecules are found at all levels of life, from cell organelles to full organisms. Understanding the chemical and physicochemical determinants guiding the formation of these assemblies is crucial not only to understand the biological processes they carry out but also to mimic nature. Among the synthetic peptides forming well-defined nanostructures, the octapeptide Lanreotide has been considered one of the best characterized, in terms of both the atomic structure and its self-assembly process. In the present work, we determined the atomic structure of Lanreotide nanotubes at 2.5-Å resolution by cryoelectron microscopy (cryo-EM). Surprisingly, the asymmetric unit in the nanotube contains eight copies of the peptide, forming two tetramers. There are thus eight different environments for the peptide, and eight different conformations in the nanotube. The structure built from the cryo-EM map is strikingly different from the molecular model, largely based on X-ray fiber diffraction, proposed 20 y ago. Comparison of the nanotube with a crystal structure at 0.83-Å resolution of a Lanreotide derivative highlights the polymorphism for this peptide family. This work shows once again that higher-order assemblies formed by even well-characterized small peptides are very difficult to predict.

Ordered Packing of β-Sheet Nanofibrils into Nanotubes: Multi-hierarchical Assembly of Designed Short Peptides

Although it is well-known proteins and their complexes are hierarchically organized and highly ordered structures, it remains a major challenge to replicate their hierarchical self-assembly process and to fabricate multihierarchical architectures with well-defined shapes and monodisperse characteristic sizes via peptide self-assembly. Here we describe an amphiphilic short peptide Ac-I₃GGHK-NH₂ that first preassembles into thin, left-handed β-sheet nanofibrils, followed by their ordered packing into right-handed nanotubes. The key intermediate morphology and structures featuring the hierarchical process are simultaneously demonstrated. Further mechanistic exploration with the variants Ac-I₃GGGK-NH₂, Ac-I₃GGFK-NH₂, and Ac-I₃GG^DH^DK-NH₂ reveals the vital role of multiple His-His side chain interactions between nanofibrils in mediating higher-order assembly and architectures. Altogether, our findings not only advance current understanding of hierarchical assembly of peptides and proteins but also afford a paradigm of how to take advantage of side chain interactions to construct higher-order assemblies with enhanced complexities.

Self-Assembling Peptides: From Design to Biomedical Applications

Self-assembling peptides could be considered a novel class of agents able to harvest an array of micro/nanostructures that are highly attractive in the biomedical field. By modifying their amino acid composition, it is possible to mime several biological functions; when assembled in micro/nanostructures, they can be used for a variety of purposes such as tissue regeneration and engineering or drug delivery to improve drug release and/or stability and to reduce side effects. Other significant advantages of self-assembled peptides involve their biocompatibility and their ability to efficiently target molecular recognition sites. Due to their intrinsic characteristics, self-assembled peptide micro/nanostructures are capable to load both hydrophobic and hydrophilic drugs, and they are suitable to achieve a triggered drug delivery at disease sites by inserting in their structure's stimuli-responsive moieties. The focus of this review was to summarize the most recent and significant studies on self-assembled peptides with an emphasis on their application in the biomedical field.

Systematic Method for the Exploration, Representation, and Classification of the Diphenylalanine Solvatomorphic Space

An understanding of the conditions that govern the self-assembly process of peptides is a fundamental step toward the design of new nanostructures that possess interesting properties. In this work, we first synthesize and explore extensively diphenylalanine (FF) self-assembling crystals formed in different solvents (i.e., solvatomorphs) using polarized optical microscopy and transmission electron microscopy. Then, we develop a numerical method that allows an unambiguous classification of the solvatomorphs through a K-means automatic clustering method. In addition, we generate a two-dimensional (2D) representation of the solvatomorphic space together with the clustering results via a principal component analysis (PCA). The classification is based on structural similarities of solvatomorphs as revealed by the analysis of their respective infrared spectra. Among the 20 samples considered, 4 clear clusters are extracted within which the compounds show very similar crystalline structures. The information extracted allows us to assign many of the peaks that appear in the complex IR spectra of the samples considered. The implementation of the overall procedure we propose, i.e., "GAULOIS" and "REFRACT-R", is transferable to other types of spectra and paves the way for a systematic, fast, and accurate classification method applicable to various types of experimental spectroscopic data.

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.

Enhanced Delivery of Neuroactive Drugs via Nasal Delivery with a Self-Healing Supramolecular Gel

This paper reports the use of a self-assembling hydrogel as a delivery vehicle for the Parkinson's disease drug l-DOPA. Based on a two-component combination of an l-glutamine amide derivative and benzaldehyde, this gel has very soft rheological properties and self-healing characteristics. It is demonstrated that the gel can be formulated to encapsulate l-DOPA. These drug-loaded gels are characterized, and rapid release of the drug is obtained from the gel network. This drug-loaded hydrogel has appropriate rheological characteristics to be amenable for injection. This system is therefore tested as a vehicle for nasal delivery of neurologically-active drugs-a drug delivery strategy that can potentially avoid first pass liver metabolism and bypass the blood-brain barrier, hence enhancing brain uptake. In vitro tests indicate that the gel has biocompatibility with respect to nasal epithelial cells. Furthermore, animal studies demonstrate that the nasal delivery of a gel loaded with 3 H-labeled l-DOPA out-performed a simple intranasal l-DOPA solution. This is attributed to longer residence times of the gel in the nasal cavity resulting in increased blood and brain concentrations. It is demonstrated that the likely routes of brain penetration of intranasally-delivered l-DOPA gel involve the trigeminal and olfactory nerves connecting to other brain regions.

Covalently Crosslinked Hydrogels via Step-Growth Reactions: Crosslinking Chemistries, Polymers, and Clinical Impact

Hydrogels are an important class of biomaterials with the unique property of high-water content in a crosslinked polymer network. In particular, chemically crosslinked hydrogels have made a great clinical impact in past years because of their desirable mechanical properties and tunability of structural and chemical properties. Various polymers and step-growth crosslinking chemistries are harnessed for fabricating such covalently crosslinked hydrogels for translational research. However, selecting appropriate crosslinking chemistries and polymers for the intended clinical application is time-consuming and challenging. It requires the integration of polymer chemistry knowledge with thoughtful crosslinking reaction design. This task becomes even more challenging when other factors such as the biological mechanisms of the pathology, practical administration routes, and regulatory requirements add additional constraints. In this review, key features of crosslinking chemistries and polymers commonly used for preparing translatable hydrogels are outlined and their performance in biological systems is summarized. The examples of effective polymer/crosslinking chemistry combinations that have yielded clinically approved hydrogel products are specifically highlighted. These hydrogel design parameters in the context of the regulatory process and clinical translation barriers, providing a guideline for the rational selection of polymer/crosslinking chemistry combinations to construct hydrogels with high translational potential are further considered.

Enhanced ordering in length-polydisperse carbon nanotube solutions at high concentrations as revealed by small angle X-ray scattering

Carbon nanotubes (CNTs) are stiff, all-carbon macromolecules with diameters as small as one nanometer and few microns long. Solutions of CNTs in chlorosulfonic acid (CSA) follow the phase behavior of rigid rod polymers interacting via a repulsive potential and display a liquid crystalline phase at sufficiently high concentration. Here, we show that small-angle X-ray scattering and polarized light microscopy data can be combined to characterize quantitatively the morphology of liquid crystalline phases formed in CNT solutions at concentrations from 3 to 6.5% by volume. We find that upon increasing their concentration, CNTs self-assemble into a liquid crystalline phase with a pleated texture and with a large inter-particle spacing that could be indicative of a transition to higher-order liquid crystalline phases. We explain how thermal undulations of CNTs can enhance their electrostatic repulsion and increase their effective diameter by an order of magnitude. By calculating the critical concentration, where the mean amplitude of undulation of an unconstrained rod becomes comparable to the rod spacing, we find that thermal undulations start to affect steric forces at concentrations as low as the isotropic cloud point in CNT solutions.

Multiscale Structural Elucidation of Peptide Nanotubes by X-Ray Scattering Methods

This mini-review presents the structural investigations of the self-assembled peptide nanotubes using X-ray scattering techniques. As compared to electron microscopy, scattering methods enable studies of nanotubes in solution under the appropriate physicochemical conditions and probe their formation mechanism. In addition, a combination of X-ray scattering methods allow the elucidation of structural organization from the molecular scale to the dimension of nanotubes.

Alpha helical surfactant-like peptides self-assemble into pH-dependent nanostructures

A designed surfactant-like peptide is shown, using a combination of cryogenic-transmission electron microscopy and small-angle X-ray scattering, to have remarkable pH-dependent self-assembly properties. Peptide Arg₃-Leu₁₂ (R₃L₁₂) forms a network of peptide nanotubes at pH 9 and below. These are associated with α-helical conformation in a "cross-α" nanotube structure, in which peptide dimers lie perpendicular to the nanotube axis, with arginine coated inner and outer nanotube walls. In contrast, this peptide forms decorated vesicular aggregates at higher pH values, close to the pK_a of the arginine residues. These structures are associated with a loss of α-helical order as detected through X-ray scattering, circular dichroism and FTIR spectroscopy, the latter technique also revealing a loss of ordering of leucine side chains. This suggests a proposed model for the decorated or patchy vesicular structures that comprises disordered peptide as the matrix of the membrane, with small domains of ordered peptide dimers forming the minority domains. We ascribe this to a lipid-raft like phase separation process, due to conformational disordering of the leucine hydrophobic chains. The observation of the self-assembly of a simple surfactant-like peptide into these types of nanostructure is remarkable, and peptide R₃L₁₂ shows unique pH-dependent morphological and conformational behaviour, with the potential for a range of future applications.

Patient and Healthcare Provider Perspectives of First-Generation Somatostatin Analogs in the Management of Neuroendocrine Tumors and Acromegaly: A Systematic Literature Review

Introduction

Somatostatin analogs (SSAs) are used to treat neuroendocrine tumors (NETs) and acromegaly. Two first-generation SSAs, octreotide long-acting release (OCT LAR) and lanreotide autogel/depot (LAN), are available. A systematic literature review (SLR) was conducted to investigate which characteristics beyond efficacy are most important in patient and healthcare practitioner (HCP) experience of LAN and OCT when used to treat acromegaly and NETs.

Methods

MEDLINE, Embase, the Cochrane Library, and Database of Abstracts of Reviews of Effect were searched from database inception to January 2019 with terms for first-generation SSAs, NETs, acromegaly, preferences, decision-making, and human factors. Key congresses in 2016–2018 and SLR bibliographies were hand-searched. Two independent reviewers screened articles at title/abstract and full-text stage. Publications fulfilling pre-specified inclusion criteria reported patient or HCP perspectives of LAN or OCT, or any factors affecting treatment perspectives for NETs or acromegaly.

Results

A total of 1110 unique records were screened, of which 21 studies were included, reporting from the perspectives of patients (n = 18) and/or HCPs (n = 9). Perspectives were collected using shared decision-making frameworks, questionnaires, informal patient opinion, and a Delphi panel. Where patient preference was specifically reported, LAN was preferred in 4/5 studies and OCT LAR in 1/5. Common factors underlying treatment experience included technical problems with injections and associated pain, emotional quality/anxiety of injections, time and convenience of treatment administration, and independence. Immediate aspects of injections appeared most important to patients, though the possibilities of extended dosing intervals and self-/partner-injection with LAN were also notable factors.

Conclusions

Study outcomes favored LAN in this SLR, with factors surrounding injection administration most influential in treatment experience. The findings of this SLR provide a basis that could inform development of decision-making criteria, with patient and HCP treatment perspectives considered. Future studies should utilize a common method to report preference and associated drivers.

Supplementary Information

The online version contains supplementary material available at 10.1007/s12325-020-01600-x.

Structural analysis of cross α-helical nanotubes provides insight into the designability of filamentous peptide nanomaterials

The exquisite structure-function correlations observed in filamentous protein assemblies provide a paradigm for the design of synthetic peptide-based nanomaterials. However, the plasticity of quaternary structure in sequence-space and the lability of helical symmetry present significant challenges to the de novo design and structural analysis of such filaments. Here, we describe a rational approach to design self-assembling peptide nanotubes based on controlling lateral interactions between protofilaments having an unusual cross-α supramolecular architecture. Near-atomic resolution cryo-EM structural analysis of seven designed nanotubes provides insight into the designability of interfaces within these synthetic peptide assemblies and identifies a non-native structural interaction based on a pair of arginine residues. This arginine clasp motif can robustly mediate cohesive interactions between protofilaments within the cross-α nanotubes. The structure of the resultant assemblies can be controlled through the sequence and length of the peptide subunits, which generates synthetic peptide filaments of similar dimensions to flagella and pili.

Human neuropeptide substance P self-assembles into semi-flexible nanotubes that can be manipulated for nanotechnology

Substance P neuropeptide is here reported to self-assemble into well-defined semi-flexible nanotubes. Using a blend of synchrotron small angle X-ray scattering, atomic force microscopy and other biophysical techniques, the natural peptide is shown to self-assemble into monodisperse 6 nm wide nanotubes, which can closely associate into nano-arrays with nematic properties. Using simple protocols, the nanotubes could be precipitated or mineralised while conserving their dimensions and core-shell morphology. Our discovery expands the small number of available monodisperse peptide nanotube systems for nanotechnology, beyond direct relevance to biologically functional peptide nanostructures since the substance P nanotubes are fundamentally different from typical amyloid fibrils.

Multiconformational analysis of tripeptides upon consideration of implicit and explicit hydration effects

During the last two decades, numerous observed data obtained by various physical techniques, also supported by molecular modeling approaches, have highlighted the structuring features of tripeptides, as well as their aggregation properties. Herein, we focus on the structural dynamics of four trimers, i.e., Gly-Gly-Gly, Gly-Ala-Gly, Ala-Ala-Ala and Ala-Phe-Ala, in an aqueous environment. Density functional theory calculations (DFT) were carried out to assess the stability of four types of secondary structures, i.e., β-strand, polyproline-II (pP-II), α-helix and γ-turn, of which the formation had been described in these tripeptides. Both implicit and explicit hydration effects were analyzed on the conformational and energetic features of trimers. It has been shown that the use of M062X functional (versus B3LYP) improve the stability of intramolecular H-bonds, especially in inverse γ-turn structures, as well as the energetic and conformational equilibrium in all tripeptides. Explicit hydration reflected by the presence of five water molecules around the backbone polar sites (NH₃⁺, N-H, CO and NH₂) considerably changes the conformational landscapes of the trimers. Characteristic intramolecular and intermolecular interactions evidenced by the calculations, were emphasized.

Force-Field Simulations of a Hydrated Lanreotide-Based Derivative: Hydration, Dynamics, and Numerical Evidence of Self-Assembly in Dimers

Recently, self-organization of the cyclic octapeptide lanreotide and lanreotide-based derivatives in a nanotube to from a dimer structure has been experimentally evidenced. While the nature of the interactions between both monomers has been strongly investigated no molecular details of the hydration of the monomer and the formation of the dimer have been provided. Using molecular dynamics simulations, this work focuses on the structure, hydration, and dynamics of water and an analog of lanreotide. To do so, several models of monomers based on different schemes of partial charges and electrostatic interaction calculations are considered. By comparison with the experiments, we show that the model based on the combination of the AMBER force-field, CHELPG charge calculation, Ewald sum is the most relevant. Additionally, by mapping the interfacial hydration of the lanreotide monomer we evidence a heterogeneous surface in terms of hydrophilicity involving heterogeneous hydration. Furthermore, we show a slowdown in the translational dynamics of water molecules located close to the lanreotide surface. We also provide the molecular details of the self-assembly in the dimer in terms of structure, hydration, and energy.

Spatially dependent H-bond dynamics at interfaces of water/biomimetic self-assembled lattice materials

Understanding hydrogen-bond interactions in self-assembled lattice materials is crucial for preparing such materials, but the role of hydrogen bonds (H bonds) remains unclear. To gain insight into H-bond interactions at the materials' intrinsic spatial scale, we investigated ultrafast H-bond dynamics between water and biomimetic self-assembled lattice materials (composed of sodium dodecyl sulfate and β-cyclodextrin) in a spatially resolved manner. To accomplish this, we developed an infrared pump, vibrational sum-frequency generation (VSFG) probe hyperspectral microscope. With this hyperspectral imaging method, we were able to observe that the primary and secondary OH groups of β-cyclodextrin exhibit markedly different dynamics, suggesting distinct H-bond environments, despite being separated by only a few angstroms. We also observed another ultrafast dynamic reflecting a weakening and restoring of H bonds between bound water and the secondary OH of β-cyclodextrin, which exhibited spatial uniformity within self-assembled domains, but heterogeneity between domains. The restoration dynamics further suggest heterogeneous hydration among the self-assembly domains. The ultrafast nature and meso- and microscopic ordering of H-bond dynamics could contribute to the flexibility and crystallinity of the material--two critically important factors for crystalline lattice self-assemblies--shedding light on engineering intermolecular interactions for self-assembled lattice materials.

Biomimetic peptide self-assembly for functional materials

Natural biomolecular systems have evolved to form a rich variety of supramolecular materials and machinery fundamental to cellular function. The assembly of these structures commonly involves interactions between specific molecular building blocks, a strategy that can also be replicated in an artificial setting to prepare functional materials. The self-assembly of synthetic biomimetic peptides thus allows the exploration of chemical and sequence space beyond that used routinely by biology. In this Review, we discuss recent conceptual and experimental advances in self-assembling artificial peptidic materials. In particular, we explore how naturally occurring structures and phenomena have inspired the development of functional biomimetic materials that we can harness for potential interactions with biological systems. As our fundamental understanding of peptide self-assembly evolves, increasingly sophisticated materials and applications emerge and lead to the development of a new set of building blocks and assembly principles relevant to materials science, molecular biology, nanotechnology and precision medicine.

Peptide nanotubes self-assembled from leucine-rich alpha helical surfactant-like peptides

The designed arginine-rich surfactant-like peptide R₃L₁₂ (arginine₃-leucine₁₂) is shown to form a remarkable diversity of self-assembled nanostructures in aqueous solution, depending on pH, including nanotubes, mesh-like tubular networks in three-dimensions and square planar arrays in two-dimensions. These structures are built from α-helical antiparallel coiled-coil peptide dimers arranged perpendicular to the nanotube axis, in a "cross-α" nanotube structure. The aggregation behavior is rationalized based on the effects of dimensionality, and the balance of hydrophobic and electrostatic interactions. The nanotube and nanomesh structures display arginine at high density on their surfaces, which may be valuable for future applications.

Tube to ribbon transition in a self-assembling model peptide system

Peptides that self-assemble into β-sheet rich aggregates are known to form a large variety of supramolecular shapes, such as ribbons, tubes or sheets. However, the underlying thermodynamic driving forces for such different structures are still not fully understood, limiting their potential applications. In the A_nK peptide system (A = alanine, K = lysine), a structural transition from tubes to ribbons has been shown to occur upon an increase of the peptide length, n, from 6 to 8. In this work we analyze this transition by means of a simple thermodynamic model. We consider three energy contributions to the total free energy: an interfacial tension, a penalty for deviating from the optimal β-sheet twist angle, and a hydrogen bond deformation when the β-sheets adopt a specific self-assembled structure. Whilst the first two contributions merely provide similar constant energy offsets, the hydrogen bond deformations differ depending on the studied structure. Consequently, the tube structure is thermodynamically favored for shorter A_nK peptides, with a crossover at n≈ 13. This qualitative agreement of the model with the experimental observations shows, that we have achieved a good understanding of the underlying thermodynamic features within the self-assembling A_nK system.

Structure of Nanotubes Self-Assembled from a Monoamide Organogelator

Some organic compounds are known to self-assemble into nanotubes in solutions, but the packing of the molecules into the walls of the tubes is known only in a very few cases. Herein, we study two compounds forming nanotubes in alkanes. They bear a secondary alkanamide chain linked to a benzoic acid propyl ester (HUB-3) or to a butyl ester (HUB-4). They gel alkanes for concentrations above 0.2 wt.%. The structures of these gels, studied by freeze fracture electron microscopy, exhibit nanotubes: for HUB-3 their external diameters are polydisperse with a mean value of 33.3 nm; for HUB-4, they are less disperse with a mean value of 25.6 nm. The structure of the gel was investigated by small- and wide-angle X-ray scattering. The evolution of the intensities show that the tubes are metastable and transit slowly toward crystals. The intensities of the tubes of HUB-4 feature up to six oscillations. The shape of the intensities proves the tubular structure of the aggregates, and gives a measurement of 20.6 nm for the outer diameters and 11.0 nm for the inner diameters. It also shows that the electron density in the wall of the tubes is heterogeneous and is well described by a model with three layers.

Hierarchically Chiral Lattice Self-Assembly Induced Circularly Polarized Luminescence

Biomaterials in nature often exhibit hierarchical chiral structures with an intriguing mechanism involving hierarchical chirality transfer from molecular to supramolecular and the nano- or microscale level. To mimic the cross-level chirality transfer, we present here one kind of host-guest complex system built of β-cyclodextrin (β-CD), sodium dodecyl sulfate (SDS), and fluorescent dyes, which show multilevel chirality, including molecular chirality of β-CD, induced supramolecular chirality of β-CD/SDS host-guest complexes, a chiral lattice self-assembled nanosheet, mesoscopic chirality of an assembled helical tube, induced chirality of a dye-doped chiral tube. The hierarchical chirality involved a chiral lattice self-assembly process, which can be identified by small-angle X-ray scattering, optical studies, circular dichroism, and circularly polarized luminescence spectral measurements. Benefiting from the chiral lattice self-assembly, intense circularly polarized luminescence was observed from the achiral dye-doped complexes with a large dissymmetry factor up to +0.1. This work thus provides a feasible insight for developing hierarchical chiroptical materials based on the lattice self-assembly.

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.

Biomimetic self-assembly of subcellular structures

This article summarizes recent progress on biomimetic subcellular structures and discusses integration of these isolated systems.

Anomalous dynamics of water at the octopeptide lanreotide surface

This work reports the study of water dynamics close to the cyclic octapeptide lanreotide from atomistic simulations of hydrated lanreotide, a cyclic octapeptide. Calculation of the hydrogen bonds between water molecules allows mapping of the hydrophilic regions of lanreotide. Whereas a super-diffusivity of the interfacial water molecules is established, a slowdown in rotational dynamics is observed, involving a decoupling between both processes. Acceleration in translation dynamics is connected to the hopping process between hydrophilic zones. Microscopically, this is correlated with the weakness of the interfacial hydrogen bonding network due to a hydrophobic interface at the origin of the interfacial sliding of water molecules. Heterogeneous rotational dynamics of water molecules close the lanreotide surface is evidenced and connected to heterogeneous hydration.

Molecular dynamics simulations of a hydrated mutated lanreotide, a cyclic octapeptide, were carried out to characterize its hydration state. We studied the water dynamics close to the peptide using atomistic simulations.

PEGylation affects the self-assembling behaviour of amphiphilic octapeptides

Surfactant-like peptides are a class of amphiphilic macromolecules, which are able to self-assemble in water forming different supramolecular structures. Among them, octapeptides composed of six hydrophobic and two hydrophilic residues have attracted interest since they have a length similar to those of natural phospholipids. Supramolecular structures of different amphiphilic octapeptides have been widely reported, but no study has been performed aimed at investigating the effect of PEGylation on their self-assembling behaviour. The aim of the present work was to synthesize and characterise the self-assembling behaviour of PEGylated alanine- or valine based amphiphilic octapeptides (mPEG_1.9kDa-DDAAAAAA and mPEG_1.9kDa-DDVVVVVV) in comparison to the non-PEGylated ones (DDAAAAAA and DDVVVVVV). The self-aggregation process in ultrapure water was investigated by fluorescence spectroscopy, small angle neutron scattering (SANS), dynamic light scattering (DLS), while the secondary structure was assessed by circular dichroism. PEGylation markedly affects the self-assembling behaviour of these amphiphilic octapeptides in terms of both critical aggregation concentration (CAC) and shape of the formed supramolecular aggregates. Indeed, PEGylation increases CAC and prevents the self-aggregation into fibrillary supramolecular aggregates (as observed for non-PEGylated peptides), by promoting the formation of micelle-like structures (as demonstrated for valine-based octapeptide). On the other side, the secondary structure of peptides seems not to be affected by PEGylation. Overall, these results suggest that self-assembling behaviour of amphiphilic octapeptides can be modified by PEGylation, with a great potential impact for the future applications of these nanomaterials.

Hierarchically oriented organization in supramolecular peptide crystals

Hierarchical self-assembly and crystallization with long-range ordered spatial arrangement is ubiquitous in nature and plays an essential role in the regulation of structures and biological functions. Inspired by the multiscale hierarchical structures in biology, tremendous efforts have been devoted to the understanding of hierarchical self-assembly and crystallization of biomolecules such as peptides and amino acids. Understanding the fundamental mechanisms underlying the construction and organization of multiscale architectures is crucial for the design and fabrication of complex functional systems with long-range alignment of molecules. This Review summarizes the typical examples for hierarchically oriented organization of peptide self-assembly and discusses the thermodynamic and kinetic mechanisms that are responsible for this specific hierarchical organization. Most importantly, we propose the concept of hierarchically oriented organization for self-assembling peptide crystals, distinct from the traditional growth mechanism of supramolecular polymerization and crystallization based on the Ostwald ripening rule. Finally, we assess critical challenges and highlight future directions towards the mechanistic understanding and versatile application of the hierarchically oriented organization mechanism.

Organic Nanoscrolls from Electrostatic Interactions between Peptides and Lipids: Assembly Steps and Structure

An important aspect of cells is their shape flexibility that gives them motion but also a high adaptation versatility to their environment. This shape versatility is mediated by different types of protein-membrane interactions among which electrostatic plays an important role. In the present work we examined the interaction between a small dicationic peptide, that possesses self-assembly properties, and lipid model membranes. The peptide, lanreotide, spontaneously forms nanotubes in water that have a strictly uniform diameter. In the current work, we show that the interaction between the cationic peptide and negatively charged bilayers of lipids induces the formation of myelin sheath-like structures that we call nanoscrolls. By deciphering the different steps of formation and the molecular structure of the self-assembly, we show how electrostatics modify the spontaneous peptide and lipid way of packing.