Self-assembled peptide-based nanostructures: Smart nanomaterials toward targeted drug delivery

Biotin–avidin interaction triggers conversion of triskelion peptide nanotori into nanochains

Triskelion biotinylated peptide is self-assembled into nanotorus structures followed by dimerization and chain formation in the presence of avidin.

Amphiphilic polypeptides with prolonged enzymatic stability for the preparation of self-assembled nanobiomaterials

Aib residue distribution in Lys/Aib polymers influences the morphology of forming nanoparticles and the rate of their enzymatic degradation.

Self-assembling dipeptide antibacterial nanostructures with membrane disrupting activity

Peptide-based supramolecular assemblies are a promising class of nanomaterials with important biomedical applications, specifically in drug delivery and tissue regeneration. However, the intrinsic antibacterial capabilities of these assemblies have been largely overlooked. The recent identification of common characteristics shared by antibacterial and self-assembling peptides provides a paradigm shift towards development of antibacterial agents. Here we present the antibacterial activity of self-assembled diphenylalanine, which emerges as the minimal model for antibacterial supramolecular polymers. The diphenylalanine nano-assemblies completely inhibit bacterial growth, trigger upregulation of stress-response regulons, induce substantial disruption to bacterial morphology, and cause membrane permeation and depolarization. We demonstrate the specificity of these membrane interactions and the development of antibacterial materials by integration of the peptide assemblies into tissue scaffolds. This study provides important insights into the significance of the interplay between self-assembly and antimicrobial activity and establishes innovative design principles toward the development of antimicrobial agents and materials.

Peptide-based supramolecular assemblies are a promising class of nanomaterials with important biomedical applications, but their antibacterial properties can be overlooked. Here the authors show the antibacterial activity of self-assembled diphenylalanine, which emerges as the minimal model for antibacterial supramolecular polymers.

Non-Covalent Loading of Anti-Cancer Doxorubicin by Modularizable Peptide Self-Assemblies for a Nanoscale Drug Carrier

We prepared nanoscale, modularizable, self-assembled peptide nanoarchitectures with diameters less of than 20 nm by combining β-sheet-forming peptides tethering a cell-penetrating peptide or a nuclear localization signal sequence. We also found that doxorubicin (Dox), an anti-cancer drug, was non-covalently accommodated by the assemblies at a ratio of one Dox molecule per ten peptides. The Dox-loaded peptide assemblies facilitated cellular uptake and subsequent nuclear localization in HeLa cells, and induced cell death even at low Dox concentrations. This peptide nanocarrier motif is a promising platform for a biocompatible drug delivery system by altering the targeting head groups of the carrier peptides.

Sonochemical synthesis of two nanostructured silver(I) coordination polymers based on semi-rigid bis(benzimidazole) ligands

Nanoparticles of two silver(I) coordination polymers (CPs), [Ag₂(L1)₂(DCTP)]_n (1) and [Ag₂(L2)(DCTP)]_n (2) (L1=1,3-bis(5,6-dimethylbenzimidazol-1-ylmethyl)benzene, L2=1,4-bis(benzimidazol-1-yl)-2-butene, H₂DCTP=2,5-dichloroterephthalic acid), were synthesized by the sonochemical approach and hydrothermal method. Both CPs were characterized by elemental analysis, IR spectra, single-crystal X-ray diffraction, scanning electron microscopy (SEM), and thermogravimetric analyses (TGA). CP 1 exhibits a 2D 4-connected sql net with the point symbol {4⁴.6²}. While CP 2 displays a 2D 3,4-connected 3,4L13 net with the point symbol {4.6²}₂{4².6².8²}. The structural diversity indicates that semi-rigid bis(benzimidazole) co-ligands play important roles in tuning the structures of the mixed Ag(I) CPs. The ultrasound irradiation time, temperature, and power showed significant effects on the morphology and growth process of the nanoparticles of two silver(I) CPs. The luminescence and photocatalytic properties of the nanoparticles of CPs 1-2 on the degradation of methyl blue (MB) were also investigated in detail.

Insight into the binding of a non-toxic, self-assembling aromatic tripeptide with ct-DNA: Spectroscopic and viscositic studies

The report describes the synthesis, self-association and DNA binding studies of an aromatic tripeptide H-Phe-Phe-Phe-OH (FFF). The peptide backbone adopts β-sheet conformation both in solid and solution. In aqueous solution, FFF self-assembles to form nanostructured aggregates. Interactions of this peptide with calf-thymus DNA (ct-DNA) have been studied using various biophysical techniques including ultraviolet (UV) absorption spectroscopy, fluorescence spectroscopy and circular dichroism (CD) spectroscopy. The value of mean binding constant calculated from UV and fluorescence spectroscopic data is (2.914 ± 0.74) x 103 M-1 which is consistent with an external binding mode. Fluorescence intercalator displacement (FID) assay, iodide quenching study, viscosity measurement and thermal denaturation study of DNA further confirm the groove binding mode of peptide, FFF with ct-DNA. MTT cell survival assay reveals very low cytotoxicity of the peptide toward human lung carcinoma cell line A549.

Harnessing self-assembled peptide nanoparticles in epitope vaccine design

Vaccination has been one of the most successful breakthroughs in medical history. In recent years, epitope-based subunit vaccines have been introduced as a safer alternative to traditional vaccines. However, they suffer from limited immunogenicity. Nanotechnology has shown value in solving this issue. Different kinds of nanovaccines have been employed, among which virus-like nanoparticles (VLPs) and self-assembled peptide nanoparticles (SAPNs) seem very promising. Recently, SAPNs have attracted special interest due to their unique properties, including molecular specificity, biodegradability, and biocompatibility. They also resemble pathogens in terms of their size. Their multivalency allows an orderly repetitive display of antigens on their surface, which induces a stronger immune response than single immunogens. In vaccine design, SAPN self-adjuvanticity is regarded an outstanding advantage, since the use of toxic adjuvants is no longer required. SAPNs are usually composed of helical or β-sheet secondary structures and are tailored from natural peptides or de novo structures. Flexibility in subunit selection opens the door to a wide variety of molecules with different characteristics. SAPN engineering is an emerging area, and more novel structures are expected to be generated in the future, particularly with the rapid progress in related computational tools. The aim of this review is to provide a state-of-the-art overview of self-assembled peptide nanoparticles and their use in vaccine design in recent studies. Additionally, principles for their design and the application of computational approaches to vaccine design are summarized.

Enzyme sensitive smart inulin-dehydropeptide conjugate self-assembles into nanostructures useful for targeted delivery of ornidazole

Molecular self-assembly of biodegradable amphiphilic polymers allows rational design of biocompatible nanomaterials for drug delivery. Use of substituted polysaccharides for such applications offers the ease of design and synthesis, and provides higher biofunctionality and biocompatibility to nanomaterials. The present work focuses on the synthesis, characterization and potential biomedical applications of self-assembled polysaccharide-based materials. We demonstrated that the synthesized amphiphilic inulin self-assembled in aqueous medium into nanostructures with average size in the range of 146-486nm and encapsulated hydrophobic therapeutic molecule, ornidazole. Hydrophophic dehydropeptide was conjugated with inulin via a biocompatible ester linkage. Dehydrophenylalanine, an unusual amino acid, was incorporated in the peptide to make it stable at a broader range of pH as well as against proteases. The resulting core-shell type of nanostructures could encapsulate ornidazole in the hydrophobic core and released it in a controlled fashion. By taking the advantage of inulin, which gets degraded in the colon by colonic bacteria, the effect of enzyme, inulinase, present in the microflora of the large intestine, on inulin-peptide degradation followed by drug release has been studied. Altogether, small peptide conjugated to inulin offers novel scaffold for the future design of nanostructures with potential applications in the field of targeted drug delivery.

Thermoresponsive Elastin-b-Collagen-Like Peptide Bioconjugate Nanovesicles for Targeted Drug Delivery to Collagen-Containing Matrices

Over the past few decades, (poly)peptide block copolymers have been widely employed in generating well-defined nanostructures as vehicles for targeted drug delivery applications. We previously reported the assembly of thermoresponsive nanoscale vesicles from an elastin-b-collagen-like peptide (ELP-CLP). The vesicles were observed to dissociate at elevated temperatures, despite the LCST-like behavior of the tethered ELP domain, which is suggested to be triggered by the unfolding of the CLP domain. Here, the potential of using the vesicles as drug delivery vehicles for targeting collagen-containing matrices is evaluated. The sustained release of an encapsulated model drug was achieved over a period of 3 weeks, following which complete release could be triggered via heating. The ELP-CLP vesicles show strong retention on a collagen substrate, presumably through collagen triple helix interactions. Cell viability and proliferation studies using fibroblasts and chondrocytes suggest that the vesicles are highly cytocompatible. Additionally, essentially no activation of a macrophage-like cell line is observed, suggesting that the vesicles do not initiate an inflammatory response. Endowed with thermally controlled delivery, the ability to bind collagen, and excellent cytocompatibility, these ELP-CLP nanovesicles are suggested to have significant potential in the controlled delivery of drugs to collagen-containing matrices and tissues.

Nanoparticles generated from a tryptophan derivative: physical characterization and anti-cancer drug delivery

Surging reports of peptide-based nanosystems and their growing potency in terms of biological utility demand for the search of newer and simpler peptide-based systems that could serve as smart templates for the development of self-assembled nanostructures. Use of simple amino acids as monomeric building blocks for synthesizing ensembles of nanostructures have gained momentum in this direction with some reports focusing on the development of nanosystems from single or modified single amino acids. In this work, we have demonstrated self-assembly and nanoparticle formation ability of a single amino acid derivative, N-alpha-(9-fluorenylmethyloxycarbonyl)-N(in)-tert-butyloxycarbonyl-L-tryptophan [Fmoc-Trp(Boc)-OH]. The nanoparticles formed by the amino acid were found to be stable to various environmental perturbations like temperature, salts and showed responsiveness to pH change. These were capable of loading and releasing different bioactive molecules and were biocompatible. These systems demonstrated high cellular uptake and doxorubicin-loaded nanoparticles were found to be more efficient in killing glioma cells as compared to the drug alone. Thus, their simple amino acid-based origin along with the ability to ferry bioactive molecules to various cells, endows them the suitability for future applications in the field of drug delivery.

Self-assembled PEG-poly(l-valine) hydrogels as promising 3D cell culture scaffolds

Self-assembled polypeptide aggregates have shown great promise in biomedical fields including drug delivery, tissue regeneration and regenerative medicine. In this study, we report self-assembled hydrogels based on mPEG-block-poly(l-valine) (PEV) copolymers. PEV copolymers with varying poly(l-valine) chain lengths were prepared by the ring-opening polymerization of N-carboxy anhydrides of l-valine using mPEG-NH₂ as the initiator. ¹H NMR and GPC confirmed their well-defined chemical structures. FT-IR analysis and DSC curves indicated the combined α-helix and β-sheet secondary polypeptide conformation and the PEG crystallization microphase in bulk solid state, respectively. Moreover, the poly(l-valine) block restricted the crystallization of PEG segment. DLS, TEM and circular dichroism spectra were employed to study the self-assembly profiles of PEV copolymers in aqueous solution. The results manifested that in diluted solution, PEV copolymers showed a combination of typical β-sheet and α-helical polypeptide structures and self-assembled into nanostructures with diverse morphologies and sizes. For concentrated PEV solutions, clear hydrogel phases were observed and dynamic rheological analyses demonstrated that the hydrogel modulus was sensitive to the polypeptide length, angular frequency, shear strain and temperature. The hydrogel formation was possibly dominated by the physical aggregation of PEV nanoassemblies as well as driven by the formation of particular polypeptide secondary structures. Human fibroblast NIH/3T3 cells were encapsulated and cultured within the hydrogel scaffolds. The encapsulated cells exhibited high viability, suggesting that PEV hydrogels have excellent cytocompatibility and could be used as three-dimensional (3D) cell culture matrices. Collectively, self-assembled PEGylated poly(l-valine) conjugate hydrogels represented a new kind of biomaterial scaffold in biomedical fields including but not limited to 3D cell culture.

Self-assemble nanoparticles based on polypeptides containing C-terminal luminescent Pt-cysteine complex

The growing attention to the luminescent nanocarriers is strongly stimulated by their potential application as drug delivery systems and by the necessity to monitor their distribution in cells and tissues. In this communication we report on the synthesis of amphiphilic polypeptides bearing C-terminal phosphorescent label together with preparation of nanoparticles using the polypeptides obtained. The approach suggested is based on a unique and highly technological process where the new phosphorescent Pt-cysteine complex serves as initiator of the ring-opening polymerization of α-amino acid N-carboxyanhydrides to obtain the polypeptides bearing intact the platinum chromophore covalently bound to the polymer chain. It was established that the luminescent label retains unchanged its emission characteristics not only in the polypeptides but also in more complicated nanoaggregates such as the polymer derived amphiphilic block-copolymers and self-assembled nanoparticles. The phosphorescent nanoparticles display no cytotoxicity and hemolytic activity in the tested range of concentrations and easily internalize into living cells that makes possible in vivo cell visualization, including prospective application in time resolved imaging and drug delivery monitoring.

Multifunctional Peptide-Amphiphile End-Capped Mesoporous Silica Nanoparticles for Tumor Targeting Drug Delivery

A tumor targeting redox-responsive drug delivery system (DDS) with bioactive surface was constructed by immobilizing peptide-based amphiphile C12-CGRKKRRQRRRPPQRGDS (defined as ADDA-TCPP) onto the mesoporous silica nanoparticles (MSNs) as an end-capping nanovalve, which consists of two main segments: a hydrophobic alkyl chain ADDA and a hydrophilic amino acid sequence containing a Tat_48-60 peptide sequence with a thiol terminal group and an RGDS targeting ligand, via a disulfide linkage for redox-triggered intracellular drug delivery. A series of characterizations confirmed that the nanosystem had been successfully fabricated. The antitumor drug doxorubicin (DOX) was selected as a model drug and efficiently trapped in the pores of MSNs, and an in vitro release experiment demonstrated that the mesopores of the resulting DOX-loaded MSNs (DOX@MSN-ss-ADDA-TCPP) could be sealed tightly with ADDA-TCPP self-assemblies through hydrophobic interactions between the alkyl chains; the resulting DDS exhibited "zero premature release" of DOX in the physical environment. However, a burst drug release was triggered by a high concentration of glutathione (GSH) in simulated cellular cytosol. Moreover, detailed investigations confirmed that incorporation of RGDS peptide facilitated the active targeting delivery of DOX to α_vβ₃ integrin overexpressed tumor cells, and Tat_48-60 modification on MSNs could enhance intracellular drug delivery, exhibiting an obvious toxicity to tumor cells. The multifunctional nanosystem constructed here can realize the controlled drug release and serve as a platform for designing multifunctional nanocarriers using diversified bioactive peptide-based amphiphile.

Development of poly(lactide-co-glycolide) nanoparticles functionalized with a mitochondria penetrating peptide

The development of mitochondria-targeting cell permeable vectors represents a promising therapeutic approach for several diseases, such as cancer and oxidative pathologies. Nevertheless, access to mitochondria can be difficult. A new hybrid material composed by poly(lactide-co-glycolide) (PLGA) functionalized with a 6-mer mitochondria penetrating peptide (MPP), consisting in alternating arginine and unnatural cyclohexylalanine, was developed. Circular dichroism, FT-IR and DSC studies indicated that the conjugation of the peptide with the polymer led to the obtainment of a more rigid material with respect to both PLGA and MPP as such. In particular, a conformational rearrangement to a helical structure was observed for MPP. MPP-PLGA conjugates were used for the preparation of nanoparticles that showed no cytotoxicity in MTT assay, suggesting their putative use for future studies on mitochondria targeting. Copyright © 2017 European Peptide Society and John Wiley & Sons, Ltd.

Construction of poly(dopamine) doped oligopeptide hydrogel

Incorporation of poly(dopamine) (PDA) into the native oligopeptide hydrogel not only improve the rigidity but also endow the hydrogel with efficient free radical scavenging ability.

Biologically inspired self-assembly of bacitracin-based platinum nanoparticles with anti-tumor effects

The green synthesis of bacitracin-based platinum nanoparticles with excellent antitumor efficacyin vitroandin vivo.

Injectable Self-Assembled Dipeptide-Based Nanocarriers for Tumor Delivery and Effective In Vivo Photodynamic Therapy

Self-assembling peptide-based materials are playing an important role in fabricating drug delivery carriers; however, they are often limited by several challenges, such as precise structure modulation, desirable nanoscale size, and sufficient circulation lifetime in the body. To address this issue, herein one type of injectable dipeptide-based nanocarriers with well-modulated size and structure has been developed by adjusting glutaraldehyde (GA)-assisted cationic dipeptide (CDP) assembly. After loading a model photosensitive drug (Ce6) and further decorating CDP nanoparticles (NPs) with heparin polymers (Hep), the desired dipeptide-based NPs are achieved with an average diameter of 100 nm and surface charge of -25 mV, which are favorable for the enhanced permeability and retention effects. Significantly, the dipeptide-based NPs with Ce6 loading have a longer circulation lifetime against opsonization than free Ce6 solution, and subsequently, they achieve the best anticancer efficiency in vivo. They do not cause body weight loss or induce bad immune activation in organs, implying good biosafety of the designed carriers. Taken together, dipeptide-based delivery carriers through GA-assisted assembly may provide a new alternative for developing precisely controlled nanostructures toward effective antitumor therapy.

Diphenylalanine peptide nanotubes self-assembled on functionalized metal surfaces for potential application in drug-eluting stent

This study focuses on the potential of diphenylalanine self-assembled peptide nanotubes (FF Nts) for delivery of flufenamic acid (FA) from metal implants. Self-assembly of FF Nts was studied in solution and on surfaces of glass, silicone and gold substrates. FA was loaded inside the shell of FF Nts and subsequently FF/FA Nts were attached to gold surfaces. The substrate were characterized by Field Emission Scanning Electron Microscopy (FESEM), fluorescence microscopy, confocal microscopy, and UV-vis spectroscopy. Release of FA from FF Nts were investigated by immersing coated metal substrates in phosphate-buffered saline for 12 days. Self-assembly of FF in water and solvent resulted in formation of nanotubes, which efficiently loaded 98% of FA with concentration of 20 µg/mL. FESEM images confirmed successful attachment of FF/FA Nts to functionalized gold substrates. In vitro release studies indicated using FF Nts has prolonged the release rate of FA for several days. Biocompatibility studied confirmed more than 50% of the cells were alive in concentration of 250-1000 µg/mL of FF Nts thus suggesting the potential of peptide based self-assemble nanostructures as an alternate system for polymer coating in drugs eluting stents. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 104A: 2280-2290, 2016.

Tripeptide consisting of benzyl protected di-cysteine and phenylalanine forms spherical assembly and induces cytotoxicity in cancer cells via apoptosis

Tripeptide self assemblies in cell growth medium induce apoptosis and promoting cancer cell death at submicromolar concentration.