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

Coassembly of peptide biomaterials offers a compelling avenue to broaden the spectrum of hierarchically ordered supramolecular nanoscale structures that may be relevant for biomedical and biotechnological applications. In this work coassemblies of amphiphilic and oppositely charged, anionic and cationic, β-sheet peptides are studied, which may give rise to a diverse range of coassembled forms. Mixtures of the peptides show significantly lower critical coassembly concentration (CCC) values compared to those of the individual pure peptides.

Decoupling Charge and Side Chain Effects in Hierarchical Organization of Cationic PFX Peptide and Alginate.

We have successfully created self-assembled membranes by combining positively charged (Pro-X-(Phe-X)-Pro) PFX peptides with negatively charged alginate. These PFX/alginate membranes were formed by three different peptides that contain either X = Arginine (R), Histidine (H), or Ornithine (O) as their charged amino acid. The assemblies were compared to membranes that were previously reported by us composed of X = lysine (K).

Bone Endosteal Mimics Regulates Breast Cancer Development and Phenotype.

Bone is a frequent site for metastatic development in various cancer types, including breast cancer, with a grim prognosis due to the distinct bone environment. Despite considerable advances, our understanding of the underlying processes leading to bone metastasis progression remains elusive. Here, we applied a bioactive three-dimensional (3D) model capable of mimicking the endosteal bone microenvironment.

Rational Formulation of targeted ABT-737 nanoparticles by self-assembled polypeptides and designed peptides.

Here we present the development of nanoparticles (NPs) formulations specifically designed for targeting the antiapoptotic Bcl-2 proteins on the outer membrane of mitochondria with the drug agent ABT-737. The NPs which are self-assembled by the natural polypeptide poly gamma glutamic acid (ϒPGA) and a designed cationic and amphiphilic peptide (PFK) have been shown to target drugs toward mitochondria. In this study we systematically developed the formulation of such NPs loaded with the ABT-737 and demonstrated the cytotoxic effect of the best identified formulation on MDA-MB-231 cells.

Staphylococcus aureus functional amyloids catalyze degradation of β-lactam antibiotics.

Antibiotic resistance of bacteria is considered one of the most alarming developments in modern medicine. While varied pathways for bacteria acquiring antibiotic resistance have been identified, there still are open questions concerning the mechanisms underlying resistance. Here, we show that alpha phenol-soluble modulins (PSMαs), functional bacterial amyloids secreted by Staphylococcus aureus, catalyze hydrolysis of β-lactams, a prominent class of antibiotic compounds.

Self-assembly at the interface of λ-carrageenan and amphiphilic and cationic peptides: More than meets the eye.

Self-assembly of macroscopic membranes at the interface between self-assembling peptides and aqueous polymer solutions of opposite charge has been explored mostly due to the membranes' unique hierarchical structure of three distinct regions, including a layer of perpendicular fibers. We report here on the formation and characterization of self-assembled membranes made with λ-carrageenan and the cationic β-sheet peptides, Pro-Lys-(Phe-Lys)-Pro (PFK). Using SAXS, SEM, ITC, and rheology, we compared these membranes' morphology and physical properties to membranes made with alginate.

Intracellular spatially-targeted chemical chaperones increase native state stability of mutant SOD1 barrel.

Amyotrophic lateral sclerosis (ALS) is a progressive neurological disorder with currently no cure. Central to the cellular dysfunction associated with this fatal proteinopathy is the accumulation of unfolded/misfolded superoxide dismutase 1 (SOD1) in various subcellular locations. The molecular mechanism driving the formation of SOD1 aggregates is not fully understood but numerous studies suggest that aberrant aggregation escalates with folding instability of mutant apoSOD1.

Hybrid Hydrogels of FKF-Peptide Assemblies and Gelatin for Sustained Antimicrobial Activity.

The growing resistance of pathogenic bacteria to conventional antibiotics promotes the development of new antimicrobial agents, including peptides. Hydrogels composed of antimicrobial peptides (AMPs) may be applied as topical treatments for skin infection and wound regeneration. The unique antimicrobial and ultrashort-peptide FKF (Phe-Lys-Phe) was recently demonstrated to form bactericidal hydrogels.

Native Glucagon Amyloids Catalyze Key Metabolic Reactions.

Glucagon is a prominent peptide hormone, playing central roles in the regulation of glucose blood-level and lipid metabolism. Formation of glucagon amyloid fibrils has been previously reported, although no biological functions of such fibrils are known. Here, we demonstrate that glucagon amyloid fibrils catalyze biologically important reactions, including esterolysis, lipid hydrolysis, and dephosphorylation.

Amyloid fishing: β-Amyloid adsorption using tailor-made coated titania nanoparticles.

Amyloidoses are a family of diseases characterized by abnormal protein folding that leads to fibril aggregates, amyloids. Extensive research efforts are devoted to developing inhibitors to amyloid aggregates. Here we set to explore functionalized titania (TiO) nanoparticles (NPs) as potential amyloid inhibiting agents.

Comparing the Antimicrobial Effect of Silver Ion-Coated Silicone and Gentamicin-Irrigated Silicone Sheets from Breast Implant Material.

Background: Post-operative infection is a significant complication of breast implant surgery that may require extensive use of antibiotics and surgical interventions. Here, we developed a biomaterial coating that is chemically bonded to silicone implants which delivers antimicrobial ions over time.

Methods: After coating the silicone implants with a "mediator" polymer (γ-PGA), the implants were impregnated with silver (Ag) ions.

Catalytically active peptides affected by self-assembly and residues order.

Amphiphilic peptides that induce catalysis are interesting alternatives to natural enzymes thanks to robustness of their synthesis and the ability to induce certain types of conformations by specific motifs of amino acid sequences. Various studies aimed at mimicking the activity of serine proteases by designed peptides. Here we demonstrate that the order by which the catalytic triad residues are positioned along amphiphilic β-strands influences both assembly structures and catalytic activity.

Assembly of cationic and amphiphilic β-sheet FKF tripeptide confers antibacterial activity.

The race drawn against bacteria facing the evolution of antimicrobial resistance fuels research for new drugs and therapeutic strategies. FKF, a tripeptide that is cationic and amphiphilic was examined in light of its potential antimicrobial activity. Acid titration of purified peptide solution, 6% w/v (136 mM), yielded a hydrogel at pH~ 4.

Aggressiveness of 4T1 breast cancer cells hampered by Wnt production-2 inhibitor nanoparticles: An in vitro study.

Polymeric nanoparticles may enable delivery of drugs with lower systemic toxicity to solid tumors. Wnt signaling are evolutionary conserved pathways, involved in proliferation and fate decisions. Alterations in Wnt signaling play a pivotal role in various cancer types that promote cancer initiation, growth, metastasis and drug resistance.

Mitochondrial responses to organelle-specific drug delivering nanoparticles composed of polypeptide and peptide complexes.

The mechanistic study of the drug carrier-target interactions of mitochondria-unique nanoparticles composed of polypeptide-peptide complexes (mPoP-NPs). The isolated organelles were employed to address the direct effects of mPoP-NPs on dynamic structure and functional wellbeing of mitochondria. Mitochondria morphology, respiration, membrane potential, reactive oxygen species generation, were examined by confocal microscopy, flow cytometry and oxygraphy.

Time matters for macroscopic membranes formed by alginate and cationic β-sheet peptides.

Hierarchically ordered planar and spherical membranes (sacs) were constructed using amphiphilic and cationic β-sheet peptides that spontaneously assembled together with negatively charged alginate solution. The system was found to form either a fully developed membrane structure with three distinct regions including characteristic perpendicular fibers or a non-fully developed contact layer lacking these standing fibers, depending on the peptide age, membrane geometry and membrane incubation time. The morphological differences were found to strongly depend on fairly-long incubation time frames that influenced both the peptide's intrinsic alignment and the reaction-diffusion process taking place at the interface.

Revisiting thioflavin T (ThT) fluorescence as a marker of protein fibrillation - The prominent role of electrostatic interactions.

Thioflavin T (ThT), a benzothiazole-based fluorophore, is a prominent dye widely employed for monitoring amyloid fibril assembly. Despite the near-universal presumption that ThT binds to β-sheet domains upon fibrillar surface via hydrophobic forces, the contribution of the positive charge of ThT to fibril binding and concomitant fluorescence enhancement have not been thoroughly assessed. Here we demonstrate a considerable interdependence between ThT fluorescence and electrostatic charges of peptide fibrils.

Antitumor Effect of Lonidamine-Polypeptide-Peptide Nanoparticles in Breast Cancer Models.

Biomaterials folded into nanoparticles (NPs) can be utilized as targeted drug delivery systems for cancer therapy. NPs may provide a vehicle for the anticancer drug lonidamine (LND), which inhibits glycolysis but was suspended from use at the clinical trial stage because of its hepatotoxicity due to poor solubility and pharmacokinetic properties. The NPs prepared by coassembly of the anionic polypeptide poly gamma glutamic acid (γ-PGA) and a designed amphiphilic and positively charged peptide (designated as mPoP-NPs) delivered LND to the mitochondria in cell cultures.

Quantitative assessment of paraoxon adsorption to amphiphilic β-sheet peptides presenting the catalytic triad of esterases.

Organophosphate compounds that are used as pesticides affect the nervous system by binding irreversibly to the active site of the enzyme acetylcholine esterase (AChE) and disrupting neuro-signaling nerve cells. In this study we characterized adsorption of paraoxon to a set of designed peptides that present different arrangements of the three amino acids of the AChE catalytic site: histidine, glutamic-acid and serine. The peptides set included two β-strands with no net charge and three β-hairpins that differ in their net charge.

RGD-presenting peptides in amphiphilic and anionic β-sheet hydrogels for improved interactions with cells.

The interest in developing functional biomaterials based on designed peptides has been increasing in recent years. The amphiphilic and anionic β-sheet peptide Pro-Asp-(Phe-Asp)-Pro, denoted FD, was previously shown to assemble into a hydrogel that induces adsorption of calcium and phosphate ions and formation of the bone mineral hydroxyapatite. In this study the integrin binding peptide, Arg-Gly-Asp (RGD), was incorporated into the hydrogel to assess its influence on an osteoblast culture.

Membrane Determinants Affect Fibrillation Processes of β-Sheet Charged Peptides.

Assembly of fibrillar peptide structures is dependent both upon their intrinsic propensities toward β-structure formation, as well as on structural modulation by external molecular factors. β-sheet structures may either be designed to form useful assemblies or be the undesired consequence of protein denaturation to toxic amyloid structures in several neurodegenerative diseases. Membrane bilayers have been implicated as primary initiators and modulators of amyloid fibrillation and the reasons for this effect are yet to be elucidated.

Negatively charged polypeptide-peptide nanoparticles showing efficient drug delivery to the mitochondria.

Polymeric nanoparticles (NPs) represent an effective platform for drug delivery systems, albeit with various limitations including low drug loading capacity, cytotoxicity and specificity. NPs composed of the negatively charged Polypeptide, poly gamma glutamic acid (γ-PGA) and a designed amphiphilic and cationic β-sheet Peptide (denoted PoP-NPs) loaded with the drug lonidamine (LND), denoted LND-PoP-NPs were previously used in our lab to successfully target the mitochondria when coated with the peptide (LND-mPoP-NPs). In this study, we improved the drug capacity of the LND-mPoP-NPs in addition to lowering non-specific toxicity associated with the drug deficient mPoP-NPs.

Peptide coating applied on the spot improves osseointegration of titanium implants.

The border between an implant's foreign material and the host tissue poses the most challenging conditions for tissue healing. With proper knowledge of the surface properties of the implant many of the side effects experienced following implantation could be eliminated by specifically designed functional coatings. We have recently demonstrated the design of a bifunctional peptide, composed of a β-strand decorated by two pSer residues that adsorb strongly on the oxide surface layer of titanium (TiO), followed by a Glu-rich 'tail' that induces calcified mineralization.

The assembly state and charge of amphiphilic β-sheet peptides affect blood clotting.

Hydrogels composed of designed β-sheet amphiphilic peptides have been exploited in controlled drug release systems, tissue regeneration and bleeding arrest applications. However the ultimate function of these hydrogels is dependent on a variety of host tissue responses, including blood clotting mechanisms. Here we studied the effect of cationic, anionic and zwitterionic β-sheet amphiphilic peptides on platelet-poor plasma (PPP) coagulation.

Biopolymer-induced calcium phosphate scaling in membrane-based water treatment systems: Langmuir model films studies.

Biofouling and scaling on reverse osmosis (RO) or nanofiltration (NF) membranes during desalination of secondary and tertiary effluents pose an obstacle that limits the reuse of wastewater. In this study we explored the mineral scaling induced by biopolymers originated from bacterial biofilms: bovine serum albumin (BSA), fibrinogen, lysozyme and alginic acid, as well as an extracts of extracellular polymeric substances (EPS) from bio-fouled RO membranes from wastewater treatment facility. Mineralization studies were performed on Langmuir films of the biopolymers deposited at the interface of a solution simulating RO desalination of secondary-treated wastewater effluents.