Cubosome lipid nanocarriers for delivery of ultra-short antimicrobial peptides.

Hypothesis: Although antimicrobial peptides (AMPs) are a promising class of new antibiotics, their inherent susceptibility to degradation requires nanocarrier-mediated delivery. While cubosome nanocarriers have been extensively studied for delivery of AMPs, we do not currently understand why cubosome encapsulation improves antimicrobial efficacy for some compounds but not others. This study therefore aims to investigate the link between the mechanism of action and permeation efficiency of the peptides, their encapsulation efficacy, and the antimicrobial activity of these systems.

Implications of In Vitro Multi-Serine Phosphorylation of Alpha-Synuclein in Aggregation and Cytotoxicity.

Post-translational modifications guide the functional diversity and identity of proteins. Phosphorylation is one such post-translational modification that has been reported in pathological proteins related to various neurodegenerative disorders such as α-synuclein (α-syn) phosphorylation in Parkinson's disease and other synucleinopathies. In α-syn, the phosphorylation has mostly been observed at S129; however, the occurrence of other serine modifications at S9, S42, and S87 is partially explored.

A promising new oral delivery mode for insulin using lipid-filled enteric-coated capsules.

The treatment of diabetes requires daily administration of the peptide insulin via subcutaneous (SC) injection due to poor stability following oral administration. Enteric capsules, designed to protect against low pH conditions in the stomach by providing a polymeric coating which only breaks down in the small intestine, have failed to significantly increase oral bioavailability for insulin. In parallel, amphiphilic lipid mesophases are versatile carrier materials which can protect encapsulated proteins and peptides from undesirable enzymatic degradation.

Rational design of potent ultrashort antimicrobial peptides with programmable assembly into nanostructured hydrogels.

Microbial resistance to common antibiotics is threatening to cause the next pandemic crisis. In this context, antimicrobial peptides (AMPs) are receiving increased attention as an alternative approach to the traditional small molecule antibiotics. Here, we report the bi-functional rational design of Fmoc-peptides as both antimicrobial and hydrogelator substances.

Lipid membrane-mediated assembly of the functional amyloid-forming peptide Somatostatin-14.

Membrane-mediated assembly has been well characterised for toxic amyloid species such as the amyloid-β peptide implicated in Alzheimer's disease. However, little is known about the membrane-mediated assembly of functional-amyloid forming peptides, recently identified as a natural storage state for neuropeptide hormones in vivo. Here, we study the aggregation of somatostatin-14 (SST-14) co-incubated with model lipid membranes.

Reduction of enzymatic degradation of insulin via encapsulation in a lipidic bicontinuous cubic phase.

Oral delivery of the protein drug insulin is not currently possible due to rapid degradation of the secondary structure in low pH conditions in the stomach and under the influence of digestive enzymes in the gastrointestinal tract. Effective oral delivery of insulin and other protein- or peptide-based drugs will, therefore, require encapsulation in a material or nanoparticle. Herein we investigate the ability of the lipid bicontinuous cubic phase formed by two lipids, monoolein (MO) and phytantriol (PT), to protect encapsulated insulin from degradation by the enzyme chymotrypsin, typically found in the small intestine.

Molecular engineering of antimicrobial peptides: microbial targets, peptide motifs and translation opportunities.

The global public health threat of antimicrobial resistance has led the scientific community to highly engage into research on alternative strategies to the traditional small molecule therapeutics. Here, we review one of the most popular alternatives amongst basic and applied research scientists, synthetic antimicrobial peptides. The ease of peptide chemical synthesis combined with emerging engineering principles and potent broad-spectrum activity, including against multidrug-resistant strains, has motivated intense scientific focus on these compounds for the past decade.

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.

Toxicity and cellular uptake of lipid nanoparticles of different structure and composition.

Cubosomes form part of the next generation of lipid nanoparticle drug delivery vehicles, enabling higher drug encapsulation efficiency, particularly for lipophilic drugs, compared to traditional liposome formulations. However, the mechanism of interaction of cubosome lipid nanoparticles with cells and their resultant cytotoxicity is not yet well characterised. We hypothesise that the uptake mechanism is dependent on the cell-type, and that cellular toxicity will be controlled by both the lipid composition and the uptake mechanism.

Sub-Ångstrom structure of collagen model peptide (GPO) shows a hydrated triple helix with pitch variation and two proline ring conformations.

Collagens are large structural proteins that are prevalent in mammalian connective tissue. Peptides designed to include a glycine-proline-hydroxyproline (GPO) amino acid triad are biomimetic analogs of the collagen triple helix, a fold that is a hallmark of collagen-like sequences. To inform the rational engineering of collagen-like peptides and proteins for food systems, we report the crystal structure of the (GPO) peptide at 0.

pH-Dependent Self-Assembly of Human Neuropeptide Hormone GnRH into Functional Amyloid Nanofibrils and Hexagonal Phases.

Gonadotropin-releasing hormone (GnRH) is a short human neuropeptide involved in the regulation of sex hormones. We report that GnRH self-assembles into reversible β-sheet-based nanofibrils, with pH-dependent kinetics. At high concentrations, these nanostructures form arrays arranged in liquid crystalline hexagonal phases.

Battacin-Inspired Ultrashort Peptides: Nanostructure Analysis and Antimicrobial Activity.

Peptides can serve as versatile therapeutics with a highly modular structure and tunable biophysical properties. In particular, the efficacy of peptide antibiotics against drug-resistant pathogens is of great promise, as few new classes of antibiotics are being developed to overcome the ever-increasing bacterial resistance to contemporary drugs. This work reports biophysical and antimicrobial studies of a designed library of ultrashort peptides that self-assemble into hydrogels at concentrations as low as 0.

Heparin assisted assembly of somatostatin amyloid nanofibrils results in disordered precipitates by hindrance of protofilaments interactions.

Amyloid nanofibrils are β-sheet rich protein or peptide assemblies that have pathological roles in over 20 neurodegenerative diseases, but also can have essential physiological roles. This wide variety of functions is likely to be due to subtle differences in amyloid structure and assembly mechanisms. Glycosaminoglycans (GAGs), like heparin, are frequently used in vitro to increase the kinetics of assembly of amyloid fibrils.

Release kinetics of somatostatin from self-assembled nanostructured hydrogels.

Somatostatin-14 is a native neuropeptide with widespread functions in the body. Self-assembly of somatostatin-14 into amyloid-like nanofibrils has been previously demonstrated in aqueous media. We here hypothesize that the somatostatin nanofibrils can form a stable depot that release monomers in a controlled manner.

Molecular interactions of amyloid nanofibrils with biological aggregation modifiers: implications for cytotoxicity mechanisms and biomaterial design.

Amyloid nanofibrils are ubiquitous biological protein fibrous aggregates, with a wide range of either toxic or beneficial activities that are relevant to human disease and normal biology. Protein amyloid fibrillization occurs via nucleated polymerization, through non-covalent interactions. As such, protein nanofibril formation is based on a complex interplay between kinetic and thermodynamic factors.

Atomic view of the histidine environment stabilizing higher-pH conformations of pH-dependent proteins.

External stimuli are powerful tools that naturally control protein assemblies and functions. For example, during viral entry and exit changes in pH are known to trigger large protein conformational changes. However, the molecular features stabilizing the higher pH structures remain unclear.

Therapeutic uses of somatostatin and its analogues: Current view and potential applications.

Somatostatin is an endogeneous cyclic tetradecapeptide hormone that exerts multiple biological activities via five ubiquitously distributed receptor subtypes. Classified as a broad inhibitory neuropeptide, somatostatin has anti-secretory, anti-proliferative and anti-angiogenic effects. The clinical use of native somatostatin is limited by a very short half-life (1 to 3min) and the broad spectrum of biological responses.

Stability and cytotoxicity of crystallin amyloid nanofibrils.

Previous work has identified crystallin proteins extracted from fish eye lenses as a cheap and readily available source for the self-assembly of amyloid nanofibrils. However, before exploring potential applications, the biophysical aspects and safety of this bionanomaterial need to be assessed so as to ensure that it can be effectively and safely used. In this study, crude crystallin amyloid fibrils are shown to be stable across a wide pH range, in a number of industrially relevant solvents, at both low and high temperatures, and in the presence of proteases.

Peroxiredoxin is a versatile self-assembling tecton for protein nanotechnology.

The potential for protein tectons to be used in nanotechnology is increasingly recognized, but the repertoire of stable proteins that assemble into defined shapes in response to an environmental trigger is limited. Peroxiredoxins (Prxs) are a protein family that shows an amazing array of supramolecular assemblies, making them attractive tectons. Human Prx3 (hPrx3) forms toroidal oligomers characteristic of the Prx family, but no structure has been solved to date.

Protein β-interfaces as a generic source of native peptide tectons.

Motifs of 7-8 amino acids were designed from the β-continuous interfaces of non-related homo-oligomeric proteins. These peptides intrinsically self-assembled into nanoarchitectures in water, while retaining some properties of their parent interfaces, especially reversibility of assembly. These results reveal a novel source of native peptide tectons.

Experimental observation of double-walled peptide nanotubes and monodispersity modeling of the number of walls.

Self-assembled nanoarchitectures based on biological molecules are attractive because of the simplicity and versatility of the building blocks. However, size control is still a challenge. This control is only possible when a given system is deeply understood.

Lamination and spherulite-like compaction of a hormone's native amyloid-like nanofibrils: spectroscopic insights into key interactions.

The native hierarchical self-assembly process of natural somatostatin-14, a highly aromatic and charged peptide hormone involved in various inhibitory functions, was investigated mainly using vibrational spectroscopy (ATR-FTIR and Raman scattering) combined with electron microscopy. Generic kinetic features of amyloid fibrillogenesis were confirmed for the somatostatin-14 case, together with new insights into key interactions involved in the further hierarchical assembly of the somatostatin-14 nanofibrils into i) laterally associated nanofibers and ii) spherulite-like amyloid droplets resulting from the compaction of the nanofibers. In particular, the key role of aromatic side-chains in both fibrillogenesis and the association of the nanofibrils into higher order structures could be followed.

Structural role of counterions adsorbed on self-assembled peptide nanotubes.

Among noncovalent forces, electrostatic ones are the strongest and possess a rather long-range action. For these reasons, charges and counterions play a prominent role in self-assembly processes in water and therefore in many biological systems. However, the complexity of the biological media often hinders a detailed understanding of all the electrostatic-related events.

Control of peptide nanotube diameter by chemical modifications of an aromatic residue involved in a single close contact.

Supramolecular self-assembly is an attractive pathway for bottom-up synthesis of novel nanomaterials. In particular, this approach allows the spontaneous formation of structures of well-defined shapes and monodisperse characteristic sizes. Because nanotechnology mainly relies on size-dependent physical phenomena, the control of monodispersity is required, but the possibility of tuning the size is also essential.

Elucidation of the self-assembly pathway of lanreotide octapeptide into beta-sheet nanotubes: role of two stable intermediates.

Nanofabrication by molecular self-assembly involves the design of molecules and self-assembly strategies so that shape and chemical complementarities drive the units to organize spontaneously into the desired structures. The power of self-assembly makes it the ubiquitous strategy of living organized matter and provides a powerful tool to chemists. However, a challenging issue in the self-assembly of complex supramolecular structures is to understand how kinetically efficient pathways emerge from the multitude of possible transition states and routes.