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We report development and preparation of synthetic polypeptide based, coacervate core polyelectrolyte complex micelles, PCMs, in aqueous media, which were characterized and evaluated for the encapsulation and in vitro release of a model single-stranded RNA, polyadenylic acid, poly(A). Cationic, α-helical polypeptides pegylated at their N-termini, PEG113-b-5bn and PEG113-b-5cn, were designed to form coacervate core PCMs upon mixing with multivalent anions in aqueous media. Sodium tripolyphosphate (TPP) and poly(A) were used as model multivalent anions that allowed optimization of polypeptide composition and chain length for formation of stable, nanoscale PCMs. PEG113-b-5c27 was selected for preparation of PCMs that were characterized under different environmental conditions using dynamic light scattering, atomic force microscopy and cryoelectron microscopy. The PCMs were found to efficiently encapsulate poly(A), were stable at physiologically relevant pH and solution ionic strength, and were able to release poly(A) in the presence of excess polyvalent anions. These PCMs were found to be a promising model system for further development of polypeptide based therapeutic delivery vehicles. [ABSTRACT FROM AUTHOR]

Biomaterials hold promise for therapeutic applications in the central nervous system (CNS). Little is known about molecular factors that determine CNS foreign body responses (FBRs) in vivo, or about how such responses influence biomaterial function. Here, we probed these factors in mice using a platform of injectable hydrogels readily modified to present interfaces with different physiochemical properties to host cells. We found that biomaterial FBRs mimic specialized multicellular CNS wound responses not present in peripheral tissues, which serve to isolate damaged neural tissue and restore barrier functions. We show that the nature and intensity of CNS FBRs are determined by definable properties that significantly influence hydrogel functions, including resorption and molecular delivery when injected into healthy brain or stroke injuries. Cationic interfaces elicit stromal cell infiltration, peripherally derived inflammation, neural damage and amyloid production. Nonionic and anionic formulations show minimal levels of these responses, which contributes to superior bioactive molecular delivery. Our results identify specific molecular mechanisms that drive FBRs in the CNS and have important implications for developing effective biomaterials for CNS applications. Implantable biomaterials evoke foreign body responses in the central nervous system. The authors compare hydrogel-based biomaterials to identify cellular interactions and molecular mechanisms that drive different types of foreign body responses that have different effects on biomaterial function. [ABSTRACT FROM AUTHOR]

A simple approach for producing supramolecular nanohybrids was developed allowing preparation of soluble hybrid two‐dimensional nanosheets in water through spontaneous organization of two‐dimensional Cu(II) rubeanate hydrate (which by itself does not dissolve in water or common organic solvents) and cationic diblock copolypeptide amphiphiles. These components self‐assembled into nanosheets with thicknesses of about several nm and widths on the order of several micrometers. Notably, the nanostructures were dependent on polypeptides containing leucine, suggesting that both cationic and hydrophobic polypeptide components are involved in generating the two‐dimensional (2D) nanosheet structures. The supramolecular hybrids exhibited excellent stability, and made it possible to control spectroscopic properties including ligand‐to‐metal‐charge‐transfer (LMCT), d‐d transition, electrochemical behavior, and electrooxidation reactions with ethanol in aqueous media. [ABSTRACT FROM AUTHOR]

Introduction: Surgical resection and systemic chemotherapy with temozolomide remain the mainstay for treatment of glioblastoma. However, many patients are not candidates for surgical resection given inaccessible tumor location or poor health status. Furthermore, despite being first line treatment, temozolomide has only limited efficacy. Methods: The development of injectable hydrogel-based carrier systems allows for the delivery of a wide range of chemotherapeutics that can achieve high local concentrations, thus potentially avoiding systemic side effects and wide-spread neurotoxicity. To test this modality in a realistic environment, we developed a diblock copolypeptide hydrogel (DCH) capable of carrying and releasing paclitaxel, a compound that we found to be highly potent against primary gliomasphere cells. Results: The DCH produced minimal tissue reactivity and was well tolerated in the immune-competent mouse brain. Paclitaxel-loaded hydrogel induced less tissue damage, cellular inflammation and reactive astrocytes than cremaphor-taxol (typical taxol-carrier) or hydrogel alone. In a deep subcortical xenograft model of glioblastoma in immunodeficient mice, injection of paclitaxel-loaded hydrogel led to local tumor control and improved survival. However, the tumor cells were highly migratory and were able to eventually escape the area of treatment. Conclusions: These findings suggest this technology may be ultimately applicable to patients with deep-seated inoperable tumors, but as currently formulated, complete tumor eradication would be highly unlikely. Future studies should focus on targeting the migratory potential of surviving cells. [ABSTRACT FROM AUTHOR]

Biologically occurring non‐canonical di‐α‐amino acids were converted into new di‐N‐carboxyanhydride (di‐NCA) monomers in reasonable yields with high purity. Five different di‐NCAs were separately copolymerized with tert‐butyl‐l‐glutamate NCA to obtain covalently crosslinked copolypeptides capable of forming hydrogels with varying crosslinker density. Comparison of hydrogel properties with residue structure revealed that different di‐α‐amino acids were not equivalent in crosslink formation. Notably, l‐cystine was found to produce significantly weaker hydrogels compared to l‐homocystine, l‐cystathionine, and l‐lanthionine, suggesting that l‐cystine may be a sub‐optimal choice of di‐α‐amino acid for preparation of copolypeptide networks. The di‐α‐amino acid crosslinkers also provided different chemical stability, where disulfide crosslinks were readily degraded by reduction, and thioether crosslinks were stable against reduction. This difference in response may provide a means to fine tune the reduction sensitivity of polypeptide biomaterial networks. Biologically occurring non‐canonical di‐α‐amino acids were converted into new di‐N‐carboxyanhydride, di‐NCA, monomers in reasonable yields with high purity. These new building blocks enabled synthesis of covalent copolypeptide biomaterial hydrogels with tunable properties. [ABSTRACT FROM AUTHOR]

Transected axons fail to regrow across anatomically complete spinal cord injuries (SCI) in adults. Diverse molecules can partially facilitate or attenuate axon growth during development or after injury1-3, but efficient reversal of this regrowth failure remains elusive4. Here we show that three factors that are essential for axon growth during development but are attenuated or lacking in adults—(i) neuron intrinsic growth capacity2,5-9, (ii) growth-supportive substrate10,11 and (iii) chemoattraction12,13—are all individually required and, in combination, are sufficient to stimulate robust axon regrowth across anatomically complete SCI lesions in adult rodents. We reactivated the growth capacity of mature descending propriospinal neurons with osteopontin, insulin-like growth factor 1 and ciliary-derived neurotrophic factor before SCI14,15; induced growth-supportive substrates with fibroblast growth factor 2 and epidermal growth factor; and chemoattracted propriospinal axons with glial-derived neurotrophic factor16,17 delivered via spatially and temporally controlled release from biomaterial depots18,19, placed sequentially after SCI. We show in both mice and rats that providing these three mechanisms in combination, but not individually, stimulated robust propriospinal axon regrowth through astrocyte scar borders and across lesion cores of non-neural tissue that was over 100-fold greater than controls. Stimulated, supported and chemoattracted propriospinal axons regrew a full spinal segment beyond lesion centres, passed well into spared neural tissue, formed terminal-like contacts exhibiting synaptic markers and conveyed a significant return of electrophysiological conduction capacity across lesions. Thus, overcoming the failure of axon regrowth across anatomically complete SCI lesions after maturity required the combined sequential reinstatement of several developmentally essential mechanisms that facilitate axon growth. These findings identify a mechanism-based biological repair strategy for complete SCI lesions that could be suitable to use with rehabilitation models designed to augment the functional recovery of remodelling circuits. Stimulating the intrinsic growth capacity of neurons and providing growth-supportive substrate and chemoattraction can allow axon regrowth across anatomically complete spinal cord injuries in adult rodents. [ABSTRACT FROM AUTHOR]

Homoallylglycine N-carboxyanhydride, Hag NCA, monomers were synthesized and used to prepare polypeptides containing Hag segments with controllable lengths of up to 245 repeats. Poly(l-homoallylglycine), GHA, was found to adopt an α-helical conformation, which provided good solubility in organic solvents and allowed high yield functionalization of its alkene side-chains via radical promoted addition of thiols. The conformations of these derivatives were shown to be switchable between α-helical and disordered states in aqueous media using thioether alkylation or oxidation reactions. Incorporation of GHA segments into block copolymers with poly(l-methionine), M, segments provided a means to orthogonally modify thioether side-chains different ways in separate copolypeptide domains. This approach allows preparation of functional polypeptides containing discrete domains of oxidized and alkylated thioether containing residues, where chain conformation and functionality of each domain can be independently modified. [ABSTRACT FROM AUTHOR]

ABSTRACT In effort to address challenges in the efficient synthesis of highly functional block copolypeptides, we report use of a combination of functional monomer polymerization and postpolymerization modification to obtain new double hydrophilic block copolypeptides with desirable properties. We prepared copolymers that contain discrete hydrophilic, nonionic poly( l-methionine sulfoxide) and Ca2+ ion binding poly( l-phosphonohomoalanine) segments. The facile and selective postpolymerization conversion of inexpensive, readily prepared poly( l-methionine) segments into nonionic, hydrophilic poly( l-methionine sulfoxide) segments reduces the need for use of combinations of protecting groups. The complex copolypeptides prepared using this strategy were able to promote formation of CaCO3 microspheres with tunable polymorphism. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016, 54, 3707-3712 [ABSTRACT FROM AUTHOR]

We have developed a facile method for preparation of ionic copolypeptide vesicles that requires no protecting groups or expensive components. We prepared amphiphilic copolypeptides containing segments of water-soluble methionine sulfonium residues. These were derived by aqueous phase, direct alkylation of a fully hydrophobic precursor diblock copolypeptide, poly(L-methionine)65- block-poly(L-leucine0.5- stat-L-phenylalanine0.5)20 (M65[L0.5/F0.5]20), with simple alkylating reagents. Methylation of M65(L0.5/F0.5)20 gave the cationic methyl-methionine sulfonium derivative MM65(L0.5/F0.5)20, and carboxymethylation gave the zwitterionic carboxymethyl-methionine sulfonium derivative MC65(L0.5/F0.5)20. Assembly of MM65(L0.5/F0.5)20 or MC65(L0.5/F0.5)20 in water gave rise to vesicles with average diameters of a few microns, which could then be extruded to nanoscale diameters. While the cationic MM-based vesicles were found to be cytotoxic, the zwitterionic MC-based vesicles were found to possess minimal cytotoxicity. [ABSTRACT FROM AUTHOR]

A methodology was developed for efficient, chemoselective transformation of methionine residues into stable, functional homocysteine derivatives. Methionine residues can undergo highly chemoselective alkylation reactions at low pH to yield stable sulfonium ions, which could then be selectively demethylated to give stable alkyl homocysteine residues. This mild, two-step process is chemoselective, efficient, tolerates many functional groups, and provides a means for creation of new functional biopolymers, site-specific peptide tagging, and synthesis of biomimetic and structural analogs of peptides. [ABSTRACT FROM AUTHOR]

There have been many recent advances in the controlled polymerization of α-amino acid- N-carboxyanhydride ( NCA) monomers into well-defined block copolypeptides. Transition metal initiating systems allow block copolypeptide synthesis with excellent control over number and lengths of block segments, chain length distribution, and chain-end functionality. Using this and other methods, block copolypeptides of controlled dimensions have been prepared and their self-assembly into organized structures studied by many research groups. The ability of well-defined block copolypeptides to assemble into supramolecular copolypeptide vesicles and hydrogels has led to the development of these materials for use in biological and medical applications. These assemblies have been found to possess unique properties that are derived from the amino acid building blocks and ordered conformations of the polypeptide segments. Recent work on the incorporation of active and stimulus-responsive functionality in these materials has tremendously increased their potential for use in biological and medical studies. For further resources related to this article, please visit the . Conflict of interest: The author has declared no conflicts of interest for this article. [ABSTRACT FROM AUTHOR]

The previously reported amphiphilic block copolypeptide, poly(l-lysine)60- block-poly(l-leucine)20 (K60L20), is able to form vesicles that can be manipulated to different sizes and be prepared in large quantities. This study expands upon that work by varying the length of the hydrophobic segment to optimize the vesicles so that they are monodisperse and low in toxicity. Copolypeptides with longer oligoleucine segments are found to have fewer toxic micelles, small aggregates, and unstable vesicles, and exhibit lower toxicity than vesicles formed from copolypeptides with shorter hydrophobic domains. Oligoleucine segments that are too long, however, result in rigid hydrophobic membranes that prevent the vesicular assemblies from being extruded into a monodisperse population of nanoscale vesicles. [ABSTRACT FROM AUTHOR]

The integration of discrete metal complexes has been attracting significant interest due to the potential of these materials for soft metal-metal interactions and supramolecular assembly. Additionally, block copolypeptide amphiphiles have been investigated concerning their capacity for self-assembly into structures such as nanoparticles, nanosheets and nanofibers. In this study, we combined these two concepts by investigating the self-assembly of discrete metal complexes in aqueous solution using block copolypeptides. Normally, discrete metal complexes such as [Au(CN)2]-, when molecularly dispersed in water, cannot interact with one another. Our results demonstrated, however, that the addition of block copolypeptide amphiphiles such as K183L19 to [Au(CN)2]- solutions induced one-dimensional integration of the discrete metal complex, resulting in photoluminescence originating from multinuclear complexes with metal-metal interactions. Transmission electron microscopy (TEM) showed a fibrous nanostructure with lengths and widths of approximately 100 and 20 nm, respectively, which grew to form advanced nanoarchitectures, including those resembling the weave patterns of Waraji (traditional Japanese straw sandals). This concept of combining block copolypeptide amphiphiles with discrete coordination compounds allows the design of flexible and functional supramolecular coordination systems in water. [ABSTRACT FROM AUTHOR]

Cell-penetrating peptides (CPPs), such as the HIV TAT peptide, are able to translocate across cellular membranes efficiently. A number of mechanisms, from direct entry to various endocytotic mechanisms (both receptor independent and receptor dependent), have been observed but how these specific amino acid sequences accomplish these effects is unknown. We show how CPP sequences can multiplex interactions with the membrane, the actin cytoskeleton, and cell-surface receptors to facilitate different translocation pathways under different conditions. Using "nunchuck" CPPs, we demonstrate that CPPs permeabilize membranes by generating topologically active saddle-splay ("negative Gaussian") membrane curvature through multidentate hydrogen bonding of lipid head groups. This requirement for negative Gaussian curvature constrains but underdetermines the amino acid content of CPPs. We observe that in most CPP sequences decreasing arginine content is offset by a simultaneous increase in lysine and hydrophobic content. Moreover, by densely organizing cationic residues while satisfying the above constraint, TAT peptide is able to combine cytoskeletal remodeling activity with membrane translocation activity. We show that the TAT peptide can induce structural changes reminiscent of macropinocytosis in actin-encapsulated giant vesicles without receptors. [ABSTRACT FROM AUTHOR]

Water-in-oil-in-water emulsions are examples of double emulsions, in which dispersions of small water droplets within larger oil droplets are themselves dispersed in a continuous aqueous phase. Emulsions occur in many forms of processing and are used extensively by the foods, cosmetics and coatings industries. Because of their compartmentalized internal structure, double emulsions can provide advantages over simple oil-in-water emulsions for encapsulation, such as the ability to carry both polar and non-polar cargos, and improved control over release of therapeutic molecules. The preparation of double emulsions typically requires mixtures of surfactants for stability; the formation of double nanoemulsions, where both inner and outer droplets are under 100 nm, has not yet been achieved. Here we show that water-in-oil-in-water double emulsions can be prepared in a simple process and stabilized over many months using single-component, synthetic amphiphilic diblock copolypeptide surfactants. These surfactants even stabilize droplets subjected to extreme flow, leading to direct, mass production of robust double nanoemulsions that are amenable to nanostructured encapsulation applications in foods, cosmetics and drug delivery. [ABSTRACT FROM AUTHOR]

Polymeric vesicles are a relatively new class of nanoscale self-assembled materials that show great promise as robust encapsulants. Compared with liposomes, use of polymeric building blocks for membrane formation allows increased stability, stimuli responsiveness and chemical diversity, which may prove advantageous for drug-delivery applications . A major drawback of most polymeric vesicles is the lack of biofunctionality, which restricts their ability to interact with cells and tissues. We have prepared vesicles composed of polyarginine and polyleucine segments that are stable in media, can entrap water soluble species, and can be processed to different sizes and prepared in large quantities. The remarkable feature of these materials is that the polyarginine segments both direct structure for vesicle formation and provide functionality for efficient intracellular delivery of the vesicles. This unique synergy between nanoscale self-assembly and inherent peptide functionality provides a new approach for design of multifunctional materials for drug delivery. [ABSTRACT FROM AUTHOR]

This article summarizes recent developments in the synthesis of polypeptides and hybrid peptide copolymers. Traditional methods used to polymerize α-amino acid-N-carboxyanhydrides (NCAs) are described, and limitations in the utility of these systems for the preparation of polypeptides are discussed. Recently developed initiators and methods are also discussed that allow polypeptide synthesis with good control over chain length, chain length distribution, and chain-end functionality. The latter feature is particularly useful for the preparation of polypeptide hybrid copolymers. The methods and strategies for the preparation of such hybrid copolymers are described, as well as analysis of the synthetic scope of the different methods. Finally, issues relating to obtaining these highly functional copolymers in pure form are detailed. [ABSTRACT FROM AUTHOR]

We report the synthesis of a variety of polylysine- b -polyleucine- b -polylysine, K m L n K o triblock copolypeptides and compare their gel forming properties to diblock copolypeptides. The architecture of the K m L n K o triblock copolypeptides forces the hydrophobic α-helical oligoleucine segments to pack perpendicular to extended fibrils in lamellar structure, and the similarity in properties between diblock and triblock copolymers supports the hypothesis that both systems assemble in a similar manner. The triblock architecture, however, allows preparation of samples with greater gel strength and better salt tolerance than diblock samples at similar concentrations. We have found that block architecture provides a means for fine adjustment of hydrogel properties beyond variation of polypeptide composition, concentration, and chain length. [ABSTRACT FROM AUTHOR]

Examines the synthesis of diblock copolypeptide amphiphiles containing charged and hydrophobic segments in hydrogel scaffolds. Description of the mechanical properties formed from dilute solutions of copolypeptides; Benefits of using synthetic materials in hydrogel formation; Factors affecting gelation.

Presents research which described a polymerization strategy that used organonickel initiators which suppress chain-transfer and termination side reactions. Structure of natural polymeric materials; Block copolymers; Synthesis of polymeric components; Value of new approach; Potential applications.

Reagents were developed to allow chemoselective tagging of methionine residues in peptides and polypeptides, subsequent bioorthogonal functionalization of the tags, and cleavage of the tags when desired. This methodology can be used for triggered release of therapeutic peptides, or release of tagged protein digests from affinity columns. [ABSTRACT FROM AUTHOR]

The article offers author's views on hydrogels derived from peptide amphiphile suspensions avoiding the need for high strain or flow rates and helping in cells growth. He states that this technique generates aligned nanofibre bundles that gel on addition of salts. He further states how this system helps in cells growth and alignment. He also highlights several aspects related to the origin of this surgery.