Spontaneous Formation of a Vesicular Assembly by a Trimesic Acid Based Triple Tailed Amphiphile

Cooperative dissolution of peptidomimetic vesicles and amyloid β fibrils

The aggregation of amyloid proteins in the brain is a significant neurotoxic event that contributes to neurodegenerative disorders. The aggregation of amyloid beta (Aβ), particularly Aβ42 monomers, into various forms such as oligomers, protofibrils, fibrils, and amyloid plaques is a key pathological feature in Alzheimer's disease. As a result, Aβ42 is a primary target and the development of molecular strategies for the dissolution of Aβ42 aggregates is considered a promising approach to mitigating Alzheimer's disease pathology. A set of pyrene-conjugated peptidomimetics derived from Aβ14-23 (AkdcPy, AkdmPy, and AkdnPy) by incorporating an unnatural amino acid [kd: cyclo(Lys-Asp)] were studied for their ability to modulate Aβ42 aggregation. AkdcPy and AkdmPy formed vesicular structures in aqueous media. The vesicles of AkdmPy loaded with the neuroprotective compound berberine (Ber), dissipated mutually in the presence of preformed Aβ42 fibrils. During this process, the active drug Ber was released. This work is expected to inspire the development of drug-loaded peptidomimetic-based therapeutic formulations to modulate disorders associated with amyloid toxicity.

ATP-Assisted Protocellular Membrane Formation with Ethanolamine-Based Amphiphiles

Prebiotic membranes are one of the essential elements of the origin of life because they build compartments to keep genetic materials and metabolic machinery safe. Since modern cell membranes are made up of ethanolamine-based phospholipids, prebiotic membrane formation with ethanolamine-based amphiphiles and phosphates might act as a bridge between the prebiotic and contemporary eras. Here, we report the prebiotic synthesis of O-lauroyl ethanolamine (OLEA), O-lauroyl methyl ethanolamine (OLMEA), and O-lauroyl dimethylethanolamine (OLDMEA) under wet-dry cycles. Turbidimetric, NMR, DLS, fluorescence, microscopy, and glucose encapsulation studies highlighted that OLEA-ATP and OLMEA-ATP form protocellular membranes in a 3:1 ratio, where ATP acts as a template. OLDMEA with a dimethyl group did not form any membrane in the presence of ATP. ADP can also template OLEA to form vesicles in a 2:1 ratio, but the ADP-templated vesicles were smaller. This suggests the critical role of the phosphate backbone in controlling the curvature of supramolecular assembly. The mechanisms of hierarchical assembly and transient dissipative assembly are discussed based on templated-complex formation via electrostatic, hydrophobic, and H-bonding interactions. Our results suggest that N-methylethanolamine-based amphiphiles could be used to form prebiotic vesicles, but the superior H-bonding ability of the ethanolamine moiety likely provides an evolutionary advantage for stable protocell formation during the fluctuating environments of early earth.

Self-assembly of amphiphilic amino acid derivatives for biomedical applications

Amino acids are one of the simplest biomolecules and they play an essential role in many biological processes. They have been extensively used as building blocks for the synthesis of functional nanomaterials, thanks to their self-assembly capacity. In particular, amphiphilic amino acid derivatives can be designed to enrich the diversity of amino acid-based building blocks, endowing them with specific properties and/or promoting self-assembly through hydrophobic interactions, hydrogen bonding, and/or π-stacking. In this review, we focus on the design of various amphiphilic amino acid derivatives able to self-assemble into different types of nanostructures that were exploited for biomedical applications, thanks to their excellent biocompatibility and biodegradability.

Naphthalimide-Based Azo-Functionalized Supramolecular Vesicle in Hypoxia-Responsive Drug Delivery

Supramolecular materials that respond to external triggers are being extensively utilized in developing spatiotemporal control in biomedical applications ranging from drug delivery to diagnostics. The present article describes the development of self-assembled vesicles in 1:9 (v/v), tetrahydrofuran (THF)-water by naphthalimide-based azo moiety containing amphiphile (NI-Azo) where azo moiety would act as the stimuli-responsive junction. The self-assembly of NI-Azo took place through H-type of aggregation. Microscopic and spectroscopic analyses confirmed the formation of supramolecular vesicles with a dimension of 200-250 nm. Azo (-N═N-) moiety is known to get reduced to amine derivatives in the presence of the azoreductase enzyme, which is overexpressed in the hypoxic microenvironment. The absorbance intensity of this characteristic azo (-N═N-) moiety of NI-Azo (1:9 (v/v), THF-water) at 458 nm got diminished in the presence of both extracellular and intracellular bacterial azoreductase extracted from Escherichia coli bacteria. The same observation was noted in the presence of sodium dithionite (mimic of azoreductase), indicating that azoreductase/sodium dithionite induced azo bond cleavage of NI-Azo, which was confirmed by matrix-assisted laser desorption ionization time-of-flight spectrometric data of the corresponding aromatic amine fragments. The anticancer drug, curcumin, was encapsulated inside NI-Azo vesicles that successfully killed B16F10 cells (cancer cells) in CoCl₂-induced hypoxic environment owing to the azoreductase-responsive release of drug. The cancer cell killing efficiency by curcumin-loaded NI-Azo vesicles in the hypoxic condition was 2.15-fold higher than that of the normoxic environment and 2.4-fold higher compared to that of native curcumin in the hypoxic condition. Notably, cancer cell killing efficiency of curcumin-loaded NI-Azo vesicles was 4.5- and 1.9-fold higher than that of noncancerous NIH3T3 cells in normoxic and hypoxic environments, respectively. Cell killing was found to be primarily through the early apoptotic pathway.

The effect of amide bond orientation and symmetry on the self-assembly and gelation of discotic tripeptides

A series of discotic tripeptides containing a rigid aromatic core and l-phenylalanine have been developed. The orientation of the amide bonds yielded variations of the structure and self-assembly properties of the compounds. The aggregation behavior of the discotic tripeptides was studied by various spectroscopic techniques. The morphology of the resulting aggregates was studied by field emission electron microscopy and atomic force microscopy. These studies showed that the orientation of the amide bonds has a strong influence on the intermolecular interactions, resulting in huge differences in the aggregation properties, and morphology of the discotic tripeptides. Only the C₃-symmetric discotic tripeptides formed organogels. The supramolecular aggregation mechanism of N-centered and C[double bond, length as m-dash]O-centered discotic tripeptides for forming 3-fold intermolecular H-bonded helical column were the same, there was only a smaller enthalpy change due to the occurrence of longer distances for the N-HO[double bond, length as m-dash]C bonds of the N-centered discotic tripeptide. Whereas, the C₂-symmetric discotic tripeptides 2 and 3 adopted a 6-fold intermolecular H-bonded dimer structure. Thus, this report presents a valuable approach for the fine-tuning of the discotic tripeptide based functional material.

Tunable morphologies and emission of photosensitive supramolecular self-assemblies through positional and trans-cis isomerization

Cyanostilbene units are widely attractive as photoresponsive supramolecular building blocks whose structures and emission can be modulated by trans-cis isomerization. Generally, the change of properties is related to the molecular structure of cyanostilbene, which is still unpredictable and needs to be explored. Herein, two benzene-1,3,5-tricarboxamide (BTA) based cyanostilbene derivatives with different cyano positions have been designed to investigate the emission as well as structural changes during the trans-cis photoisomerization process in monomer and aggregation states, respectively. In the monomer state, the derivative with cyano groups at the outer position, β-BTTPA, exhibits obvious emission enhancement upon UV irradiation, while the other derivative (α-BTTPA) shows emission quenching. In addition, upon the formation of aggregates, β-BTTPA forms nano-level fibers with blue-green emission, but α-BTTPA forms micron-level flat ribbons with blue emission. More importantly, also driven by the trans-cis photoisomerization, the self-assemblies show morphological transitions (ribbons/fibers to spheres) due to the fact that the equilibrium of the system is broken by the photoreactions. Such changes further contribute to emission switching as well as enhanced hydrophobic properties.

Self-assembly of surface functionalized amphiphilic carbon dots: tuning in morphological manifestations

Despite the continuous surge of interest in supramolecular chemistry, the design and synthesis of building blocks to develop diverse examples of self-assemblies is still challenging. During the past decades, formation of self-assemblies such as micelles, vesicles, and gels with a fibril network using amphiphiles has been investigated at length. Considering the increasing applications of these self-aggregates across the scientific domain, it is crucial to adopt an alternative strategy for the preparation of self-aggregates using a new building block that has been applied in diverse domains. With this aim, surface functionalized carbon dots (CDs) with varying aliphatic/aromatic (cholesteryl, palmitoyl, naphthyl) substitutions linked with spacers such as ethylenediamine, p-phenylenediamine, 2,2'-(ethylenedioxy)bis(ethylamine) were developed. The surface passivated CDs formed self-assemblies in dimethylsulfoxide-water (DMSO-H₂O, 2 : 1, v/v). The roles of surface functionalities and spacer units in the formation of self-assemblies using the synthesized CDs were investigated by microscopic and spectroscopic studies. Progressive morphological transition was found from vesicle-to-fiber in DMSO-H₂O (2 : 1, v/v) which was dependent on surface passivating substitutions of the CDs from cholesteryl to naphthyl to palmitoyl. Together with the exclusive formation of self-assemblies using amphiphilic CDs, the present study enabled the tuning of self-organization behaviour of the CD by alteration of its surface functionality.

Glucose-triggered dissolution of phenylboronic acid-functionalized cholesterol-based niosomal self-assembly for tuneable drug release

Cholesterol-containing phenylboronic acid-based niosomal self-assemblies showed glucose-responsive dissolution and release of an encapsulated drug.

Tailor-Made Self-Assemblies from Functionalized Amphiphiles: Diversity and Applications

The objective of this feature article is to coalesce our recent advancements on different expressions of tailor-made supramolecular self-assemblies and to explore them as a function of molecular architecture. In the last decade, we have developed a library of elegant and simple functional amphiphilic small molecules, which have very interesting abilities to form diverse manifestations of supramolecular self-assemblies such as micelles, reverse micelles, vesicles, fibers, supramolecular gels, and so on. Each of the expressions of the self-aggregated structures has its individual prominence and finds important applications in the fields of chemistry, physics, biology, and others. In this feature article, the major emphasis is mostly on how to attain precise control over the development of various well-defined supramolecular self-assemblies through the judicious design of low-molecular-weight amphiphiles. By tuning only the functional moieties of the amphiphilic structure, diverse supramolecular architectures can be constructed with task-specific applications. We expect that this article will provide a general and conceptual demonstration of various approaches to the development of different functional supramolecular systems and their prospective applications in numerous domains.

Multicomponent peptide assemblies

Self-assembled peptide nanostructures have been increasingly exploited as functional materials for applications in biomedicine and energy. The emergent properties of these nanomaterials determine the applications for which they can be exploited. It has recently been appreciated that nanomaterials composed of multicomponent coassembled peptides often display unique emergent properties that have the potential to dramatically expand the functional utility of peptide-based materials. This review presents recent efforts in the development of multicomponent peptide assemblies. The discussion includes multicomponent assemblies derived from short low molecular weight peptides, peptide amphiphiles, coiled coil peptides, collagen, and β-sheet peptides. The design, structure, emergent properties, and applications for these multicomponent assemblies are presented in order to illustrate the potential of these formulations as sophisticated next-generation bio-inspired materials.

Glucose oxidase mediated targeted cancer-starving therapy by biotinylated self-assembled vesicles

Glucose oxidase (GOx) mediated targeted cancer-starving therapy, by blocking the energy supply to cancer cells, has been demonstrated using GOx encapsulating monolayer vesicles of a trimesic acid based biotinylated amphiphile (TMB). GOx, loaded within the TMB vesicles, was selectively delivered inside the cancer cells, resulting in ∼6-fold higher killing of cancer cells compared to normal cells.

First in situ vesicular self-assembly of ‘binols’ generated by a two-component aerobic oxidation reaction

Generation of vesicular self-assemblies from natural and synthetic components has been in the frontiers of research in recent years for an improved understanding of the self-assembly process and also because of its prospective and realized applications in the areas of advanced materials, biotechnology and medicine. In the present work, we report the first example of the in situ generation of vesicular self-assemblies during an aerobic coupling reaction. The two precursor 2-naphthol units, having hydrogen bond donor–acceptor groups with appended alkyl chains, yielded binol (2,2′-dihydroxy-1,1′-binaphthyl) derivatives by aerobic coupling that spontaneously self-assembled in situ, yielding vesicular self-assemblies and gels. The morphology of the self-assemblies has been characterized by various optical, electron and atomic force microscopic techniques. The vesicular self-assemblies obtained in the liquids were capable of entrapping fluorophores such as rhodamine-B and carboxy fluorescein including the anticancer drug doxorubicin. The entrapped fluorophores could also be released by sonication or by rupture of vesicles. The supramolecular gels obtained in binary solvent mixtures showed improved gelation abilities with increase in the alkyl chain lengths as reflected by their minimum gelator concentration (mgcs) values, gel to sol transition temperatures (T_gel) and rheology properties. The results described here are also the first demonstration of gelation during an aerobic coupling reaction.

Binol derivatives, obtained by aerobic coupling of two 2-naphthol derivatives having H-bond donor–acceptor groups and appended alkyl chains, spontaneously self-assembled in situ yielding vesicular self-assemblies and gels.

l-Phenylalanine-Tethered, Naphthalene Diimide-Based, Aggregation-Induced, Green-Emitting Organic Nanoparticles

The present article delineates the formation of green fluorescent organic nanoparticle through supramolecular aggregation of naphthalene diimide (NDI)-based, carboxybenzyl-protected, l-phenylalanine-appended bola-amphiphile, NDI-1. The amphiphilic molecule is soluble in DMSO, and, with gradual addition of water within the DMSO solution, the amphiphile starts to self-assemble via H-type aggregation to form spherical nanoparticles. These self-assembly of NDI-1 in the presence of a high amount of water exhibited aggregation-induced emission (AIE) through excimer formation. Notably, in the presence of 99% water content, the amphiphile forms spherical aggregated nanoparticles as confirmed from microscopic investigations and dynamic light scattering study. Interestingly, the emission maxima of molecularly dissolved NDI-1 (weak blue fluorescence) red-shifted upon aggregation with increase in water concentration and led to the formation of green-emitting fluorescent organic nanoparticles (FONPs) at 99% water content. These green-emitting FONPs were utilized in cell imaging as well as for efficient transportation of anticancer drug curcumin inside mammalian cells.

Nanoarchitectures by hierarchical self-assembly of ursolic acid: entrapment and release of fluorophores including anticancer drug doxorubicin

Ursolic acid, a naturally occurring 6-6-6-6-6 monohydroxy triterpenic acid, extractable from the leaves ofPlumeria rubra, spontaneously self-assemble in aqueous liquids yielding nanoarchitectures capable of entrapping guest molecules including anticancer drug.

Synergistic Anticancer Effect of Peptide-Docetaxel Nanoassembly Targeted to Tubulin: Toward Development of Dual Warhead Containing Nanomedicine

Microtubule dynamics play a crucial role in cancer cell division. Various drugs are developed to target microtubule. Although a few of them show potential in treatment of cancer, but success rate is limited due to their poor bioavailability and lack of specificity. Thus, development of highly bioavailable and target specific anticancer drug is extremely necessary. To address these key issues, here, a combination of approaches such as development of a dodecapeptide-docetaxel nanoassembly targeted to tubulin and MUC1 (mucin 1, cell surface associated glycoprotein) targeting oligonucleotide aptamer conjugated liposome for delivering peptide-docetaxel nanoassembly into the breast cancer cell have been demonstrated. These studies reveal that the peptide forms nanoassembly and entraps docetaxel drug. Further, the liposomal formulation of peptide-docetaxel exerts synergistic anticancer effect, activates key mitotic check point proteins, and inhibits bipolar spindle formation, metastatic cancer cell migration, and growth of tumor mimicking 3D multicellular spheroid.