Assembly Behavior Research Articles

Mesoscale simulation of the compression and small-strain elastic shear behavior of illite nanoparticle assemblies

Mesoscale simulation of the compression and small-strain elastic shear behavior of illite nanoparticle assemblies

Adsorption and Bulk Assembly of Quaternized Hydroxyethylcellulose–Anionic Surfactant Complexes on Negatively Charged Substrates

This study examines the adsorption and bulk assembly behaviour of quaternized hydroxyethylcellulose ethoxylate (QHECE)–sodium dodecyl sulphate (SDS) complexes on negatively charged substrates. Due to its quaternized structure, QHECE, which is used in several industries, including cosmetics, exhibits enhanced electrostatic interactions. The phase behaviour and adsorption mechanisms of QHECE–SDS complexes are investigated using model substrates that mimic the wettability and surface charge of damaged hair fibres. Two preparation methodologies, high-concentration mixing and gradient-free mixing, were employed to examine their impact on the complex equilibrium, phase behaviour, and adsorption properties of the complexes. The measurements of turbidity, electrophoretic mobility, and conductivity demonstrate the existence of nonequilibrium dynamics during the mixing process, which exert a significant influence on the structural and functional characteristics of the complexes. The quartz crystal microbalance with dissipation monitoring (QCM-D) was employed to investigate the adsorption of the complexes onto the substrates. The results demonstrated the critical role of intermediate SDS concentrations in enhancing deposition. The findings emphasise the importance of formulation and preparation protocols in designing stable, high-performance cosmetic products. This research advances our understanding of polyelectrolyte–surfactant interactions and provides insights into optimising QHECE-based formulations.

Context-Dependent Heterotypic Assemblies of Intrinsically Disordered Peptides.

Despite their critical role in context-dependent interactions for protein functions, intrinsically disordered regions (IDRs) are often overlooked for designing peptide assemblies. Here, we exploit IDRs to enable context-dependent heterotypic assemblies of intrinsically disordered peptides, where "context-dependent" refers to assembly behavior driven by interactions with other molecules. By attaching an aromatic segment to oppositely charged intrinsically disordered peptides, we achieve a nanofiber formation. Although the same-charged peptides cannot self-assemble, oppositely charged peptides form heterotypic nanofibers. Cryo-EM analysis reveals a β-sheet arrangement within the ordered core of these nanofibers, conformational heterogeneity, and a disorder-to-order continuum and shows a high number of hydrogen bonds between tyrosine and lysine ε-amine. Additionally, this work demonstrates a post-assembly morphological change resulting from local conformational flexibility. While equal molar mixtures of the charged intrinsically disordered peptides yield nanofibers, doubling the positively charged peptides after assembly produces bundles of nanofibers. Furthermore, reducing the number of aromatic amino acid residues reduces bundle formation. Demonstrating context-dependent self-assembly of intrinsically disordered peptides and revealing atomistic insights into heterotypic assemblies of intrinsically disordered peptides for the first time, this work illustrates a straightforward approach to enable heterotypic intrinsically disordered peptides to self-assemble for the design of adaptive, multifunctional peptide nanomaterials.

Living Cell-Mediated Self-Assembly: From Monomer Design and Morphology Regulation to Biomedical Applications.

The self-assembly of molecules into highly ordered architectures is a ubiquitous and natural process, wherein molecules spontaneously organize into large structures to perform diverse functions. Drawing inspiration from the formation of natural nanostructures, cell-mediated self-assembly has been developed to create functional assemblies both inside and outside living cells. These techniques have been employed to regulate the cellular world by leveraging the dynamic intracellular and extracellular microenvironment. This review highlights the recent advances and future trends in living cell-mediated self-assembly, ranging from their cytocompatible monomer designs, synthetic strategies, and morphological control to functional applications. The assembly behaviors are also discussed based on the dimensionality of the self-assembled morphologies from zero to three dimensions. Finally, this review explores its promising potential for biomedical applications, clarifying the relationship between initial morphological regulation and the therapeutic effects of subsequent artificial assemblies. Through rationally designing molecular structures and precisely controlling assembly morphologies, living cell mediated self-assembly would provide an innovative platform for executing biological functions.

Sub-5 Ångstrom Porosity Tuning in Calixarene-Derived Porous Liquids via Supramolecular Complexation Construction.

Precise sub-Ångstrom-level porosity engineering, which is appealing in gas separations, has been demonstrated in solid carbon, polymer, and framework materials but rarely achieved in the liquid phase. In this work, a gas molecular sieving effect in the liquid phase at sub-5 Ångstrom scale is created via sophisticated porosity tuning in calixarene-derived porous liquids (PLs). Type II PLs are constructed via supramolecular complexation between the sodium salts of calixarene derivatives and crown ether solvents. The chemical structure variation and assembly behavior of the porous host upon PL construction are monitored by spectroscopy-, X-ray-, and neutron-scattering techniques. The presence of permanent porosity in calixarene-derived PLs is verified by pressure swing gas uptake, altered CO2 physisorption behavior, and dynamic theoretical simulation. Sub-5 Ångstrom porosity tuning within the PL phase is achieved by introducing bulky substituted groups on the benzene ring of the calixarene host, which then greatly affects the dynamic motion and transport behavior of CO2 molecules and the Xe uptake performance. The approach being demonstrated in this work represents a promising pathway to tune and leverage the porosity effect for enhanced gas uptake capacity and selectivity in liquid sorbents.

A computational method for the component screening of carrier-free nanodrugs: exemplified by berberine

The emergence of carrier-free nanodrugs as a promising drug delivery system is a significant development in the field of pharmaceutical research. The research on molecules that can form carrier-free nanodrugs can facilitate the expansion of their applications. The capacity of molecules to self-assemble with other molecules is the foundation upon which their formation of carrier-free nanodrugs is based. In this paper, we present a computational method for evaluating the assembly ability of molecules in aqueous environments. The method begins with screening the optimal conformation of a single molecule in water, then simulates the assembly behavior of two molecules in water, and finally calculates the optimal conformation of dimer in water. In comparison to the original computational method, this method describes the effect of water on molecular assembly behavior with the greatest possible realism by utilizing high-precision water environments in each step. The accuracy of the method has been validated by classical experiments, while its rationality has been demonstrated by electronic structure calculations of single molecules and assemblies. Furthermore, we employ the method to investigate the assembly capabilities of 54 molecules in the presence of berberine. The results demonstrate that anthraquinone and flavonoid molecules readily form robustly bound assemblies with berberine. This method offers a relatively efficient approach to compositional screening of carrier-free nanodrugs, thereby contributing to the advancement of the field.

Two sides of the coin: synthesis and applications of Janus particles.

Named after the two-faced Roman god, Janus particles (JPs) are defined by their distinct dual chemical compositions on a single particle. Research on micron-sized JPs has yielded remarkable insights, showcasing their unique assembly behaviors both in bulk and at interfaces. However, significant challenges persist, particularly in the synthesis of smaller (<500 nm) JPs, which remains complex and difficult to scale up. To date, there has been no commercial success with JPs. Recently, seeded synthesis methods, such as emulsion polymerization that is already employed in industrial-scale manufacturing, have shown great promise. These methods enable the production of high-quality JPs with different sizes, morphologies, and functionalities. This advancement has inspired more efforts in exploring JP applications across various fields, including emulsion stabilization, drug delivery, electronic devices, and coatings. This review provides a comprehensive overview of the recent progress in the synthesis and application of polymeric JPs, with an emphasis on the seeded synthesis approach. It discusses the underlying reaction mechanisms and explores different strategies for controlling JP morphology. Serving as a roadmap, this review aims to guide the design of novel functional JPs and their potential future applications. The successful implementation of JPs will require careful consideration and a deep understanding of both synthesis and applications, as these are indeed two sides of the same coin.

Dimer Is Not Double: The Unexpected Behavior of Two-Floor Peptide Nanosponge.

Using the framework of an investigation of the stimuli-responsive behavior of peptide assembly on a solid surface, this study on the behavior of a chemisorbed peptide on a gold surface was performed. The studied peptide is a dimeric form of the antimicrobial peptide Trichogin GAIV, which was also modified by substituting the glycine with lysine residues, while the N-terminus octanoyl group was replaced by a lipoic one that was able to bind to the gold surface. In this way, a chemically linked peptide assembly that is pH-responsive was obtained because of the protonation/deprotonation of the sidechains of the Lys residues. Information about the effect of protonation/deprotonation equilibria switching the pH from acid (pH = 3) to basic (pH = 11) conditions was obtained macroscopically by performing Quartz crystal microbalance with dissipation monitoring (QCM-D), Surface Plasmon Resonance (SPR), Nanoplasmonic Sensing (NPS), and FTIR techniques. Using molecular dynamics (MD) simulations, it is possible to explain, at the molecular level, our main experimental results: (1) pH changes induce a squeezing behavior in the system, consisting in thickness and mass variations in the peptide layer, which are mainly due to the pH-driven hydrophilic/hydrophobic character of the lysine residues, and (2) the observed hysteresis is due to small conformational rearrangements from helix to beta sheets occurring mainly on the first half of the peptide, closer to the surface, while the second half remains almost unaffected. The latter result, together with the evidence that the layer thickness is not simply double the assembly of the monomeric analog, indicates that the dimeric peptide does not behave as a double monomer, but assumes very peculiar features.

Binding of a Co(III) Metalloporphyrin to Amines in Water: Influence of the pKa and Aromaticity of the Ligand, and pH-Modulated Allosteric Effect.

Metalloporphyrins have been widely utilized as building blocks for molecular self-assembly in organic solvents, but their application in water is less common due to competition from water molecules for the metal center. However, Co(III) metalloporphyrins are notable for their strong binding to two aromatic amine ligands in aqueous buffers. In this study, we present a comprehensive investigation of the binding behavior of Co(III) tetraphenyl sulfonic acid porphyrin with selected aromatic and aliphatic amines in aqueous solution. Our findings reveal that the ligand affinity is influenced by the pKa values of both the ligand and the porphyrin, as well as the hybridization state of the nitrogen atom, with binding to sp3-hybridized nitrogen being significantly weaker than to sp2-hybridized nitrogen. DFT calculations further suggest that the variations in binding affinities are due to differences in the electrostatic potential at the nitrogen atoms, with aromatic ligands generally exhibiting stronger Co-N coordination due to greater electrostatic attraction. Moreover, our study and the binding model we developed demonstrate that changes in pH affect the affinity for each ligand to varying degrees, sometimes resulting in an allosteric cooperative effect. This effect is linked to electronic changes introduced by the binding of the first ligand. Our model provides a predictive tool for understanding the assembly behavior of these porphyrins in aqueous buffers, with potential applications in developing more efficient catalysts and in the creation of smart materials for fields ranging from catalysis to nanomedicine and optoelectronics.

From Frustration to Order: Role of Fluid-Fluid Interfaces in Precision Assembly of Nanoparticles.

Fluid-fluid interfaces are an attractive platform for self-assembling nanoparticles into low-dimensional materials. In this Perspective, we review recent developments in the use of interfaces to direct the assembly of spherical and anisotropic nanoparticles into diverse and sophisticated architectures. We illustrate how nanoparticle clusters, strings, networks, superlattices, chiral lattices, and quasicrystals can be self-assembled by harnessing the frustration between interfacial and interparticle forces. We highlight the role of polymeric ligands attached to the surface of nanoparticles in modulating assembly behavior by directly altering particle-fluid and particle-particle interactions or by deforming at interfaces and junctions between particles. We conclude by providing a roadmap of key questions and opportunities in this exciting field of interfacial assembly.

Mechanical Behavior of Flexible Fiber Assemblies: Review and Future Perspectives.

Flexible fibers, such as biomass particles and glass fibers, are critical raw materials in the energy and composites industries. Assemblies of the fibers show strong interlocking, non-Newtonian and compressible flows, intermittent avalanches, and high energy dissipation rates due to their elongation and flexibility. Conventional mechanical theories developed for regular granular materials, such as dry sands and pharmaceutical powders, are often unsuitable for modeling flexible fibers, which exhibit more complex mechanical behaviors. This article provides a comprehensive review of the current state of research on the mechanics of flexible fiber assemblies, focusing on their behavior under compression, shear flow, and gas-fiber two-phase flow processes. Finally, the paper discusses open issues and future directions, highlighting the need for advancements in granular theories to better accommodate the unique characteristics of flexible fibers, and suggesting potential strategies for improving their handling in industrial applications.

Modulating the assembly of starch-lecithin inclusion complexes and its underlying mechanism for controlling starch digestibility under the dense system

Starch-lipid inclusion complexes were used to regulate starch digestibility by changing the binding affinity of digestive enzymes such as α-amylase and α-glucosidase. However, when above a critical aggregation concentration (CAC) of starch and lipid molecules, they tended to self-assemble into double helices or normal micelles respectively, rather than interacting with each other to form starch-lipid complexes. Thus, how to enhance the complexation efficiency under a dense system is the key approach for the improvement of starch bioaccessibility and nutritional function. Herein, based on the dimethyl sulfoxide (DMSO) reverse solvent method, the effect of water/DMSO ratios and starch chain structures on the interaction and assembly behaviors between starch and lecithin molecules in high concentrations were systematically investigated. The results revealed that water/DMSO in a ratio of 1.5:1 promoted the interactions between cavities of starch helices and long alkyl chains of lecithin molecules, with higher level of complexed lecithin content, relative crystallinity (RC), enthalpy (ΔH) (Tp＞100°C), ordered-aggregation structures and resistant starch (RS) content. In this kind of solvent, starch samples with higher content of amylose and longer chains (degree of polymerization (DP) of B2 chains and B3+ chains) is advantageous to the formation of VII-type inclusion starch-lecithin complexes, with a rise in RS from 14.17% to 43.64%. It provided an effective method to modulate starch digestibility under the dense system of starch and lecithin via modulating the water/DMSO ratios and starch fine structures and lay the foundation for the large-scale preparation and application of starch-lecithin complexes.

Assembly landscape of the complete B-repeat superdomain from Staphylococcus epidermidis strain 1457.

The accumulation-associated protein (Aap) is the primary determinant of Staphylococcus epidermidis device-related infections. The B-repeat superdomain is responsible for intercellular adhesion that leads to the development of biofilms occurring in such infections. It was recently demonstrated that Zn-induced B-repeat assembly leads to formation of functional amyloid fibrils, which offer strength and stability to the biofilm. Rigorous biophysical studies of Aap B-repeats from S. epidermidis strain RP62A revealed Zn-induced assembly into stable, reversible dimers and tetramers, prior to aggregation into amyloid fibrils. Genetic manipulation is not tractable for many S. epidermidis strains, including RP62A; instead, many genetic studies have used strain 1457. Therefore, to better connect findings from biophysical and structural studies of B-repeats to in vivo studies, the B-repeat superdomain from strain 1457 was examined. Differences between the B-repeats from strain RP62A and 1457 include the number of B-repeats, which has been shown to play a critical role in assembly into amyloid fibrils, as well as the distribution of consensus and variant B-repeat subtypes, which differ in assembly competency and thermal stability. Detailed investigation of the Zn-induced assembly of the full B-repeat supderdomain from strain 1457 was conducted using analytical ultracentrifugation. Whereas the previous construct from RP62A (Brpt5.5) formed a stable tetramer prior to aggregation, Brpt6.5 from 1457 forms extremely large stable species on the order of ∼28-mers, prior to aggregation into similar amyloid fibrils. Our data suggest that both assembly pathways may proceed through the same mechanism of dimerization and tetramerization, and both conclude with the formation of amyloid-like fibrils. Discussion of assembly behavior of B-repeats from different strains and of different length is provided with considerations of biological implications.

Particle-morphology-based characterization of the breakage behavior of particle assemblies under one-dimensional compression

Particle-morphology-based characterization of the breakage behavior of particle assemblies under one-dimensional compression

Mechanical Behavior of Plasma-Treated Metal-Rubber Assemblies.

Metal-elastomer assemblies, such as aluminum-NBR and stainless steel-FKM, widely used for sealing or damping functions in various fields, are currently prepared with highly toxic bonding agents. To substitute the use of these liquids, plasma technologies were applied. The chemical nature of the plasma polymerized adhesives is found to have no influence on the viscoelastic properties of the elastomer. Furthermore, cohesive assemblies were prepared with acetylene, acrylic acid or maleic anhydride as plasma polymerized layers. Their adhesive performances were evaluated thanks to a tack-like test. Their adhesion mechanisms, even if complex, are namely identified as the interdiffusion of elastomer chains within the plasma-based polymer film and the thermodynamic adhesion. Specifically, we propose that the adhesiveness of metal-rubber assemblies, correlated to the maximum stress at failure in the tack-like test, is proportional to an energy per unit volume. This new variable is determined as the ratio of the surface tension to the thinness of the plasma adhesive.

Recent Advances of Stimuli-Responsive Liquid-Liquid Interfaces Stabilized by Nanoparticles.

Liquid-liquid interfaces offer highly controlled, flexible, and adaptable platforms for precise molecular assemblies, enabling the construction of sophisticated functional materials. Interfacial assemblies of specific nanoparticles (NPs) and ligands can alter their physicochemical states under external stimuli, leading to macroscopic dynamic transformations at the interface. This Review summarizes and analyzes the recent advances of the assembly and disassembly behaviors of various stimuli-responsive nanoparticle surfactants (NPSs) at liquid-liquid interfaces, focusing on their responsive behaviors when exposed to external stimuli and the interaction forces between interfacial molecules. Additionally, we outline recent advancements in applications such as reconfigurable all-liquid devices, all-liquid 3D printing, and chemical reaction platforms. Finally, we discuss current challenges and future prospects for the development of applications in this rapidly evolving field.

Synergistic Phototherapy Using Zwitterionic Crystalline Nanoaggregates of Orthogonal Donor–Acceptor Small‐Molecule Dyads

AbstractDeveloping nanophotosensitizer (nanoPS) for synergistic phototherapy by leveraging the aggregation of small‐molecule dyes is compelling frontier in precision medicine, but challenges remain due to the limited understanding of the interactions between molecular structure, assembly behavior, and theranostic function. Here, the concept of “spin‐orbit charge‐transfer intersystem crossing (SOCT‐ISC) in crystalline aggregates” is introduced, which significantly enhances photodynamic (PD) and photothermal (PT) properties of small‐molecule‐based nanoPS. Specifically, a cationic pyridine (Py) group is incorporated at the meso‐position of a tricyanofuran (TCF)‐containing anionic heptamethine cyanine (TCF‐Cy7‐TCF) dye to construct an orthogonal charge‐transfer dyad (TCF‐Cy7(Py)‐TCF), boosting triplet state formation through SOCT‐ISC mechanism to enhance the PD properties. Remarkably, the zwitterion moieties impart TCF‐Cy7(Py)‐TCF with high crystallinity even at ultralow concentrations, dictating its stacking behavior within aggregates and enhancing both PT and PD properties. The TCF‐Cy7(Py)‐TCF nanoaggregates exhibit superior singlet oxygen quantum yield (0.8% vs 0.2%) and photothermal conversion efficiency (55.06% vs 7.78%) compared to TCF‐Cy7‐TCF. Impressively, TCF‐Cy7(Py)‐TCF preferentially accumulates at tumor sites, yielding high signal‐to‐background ratios for tumor imaging in NIR‐I and NIR‐II windows, with minimal nonspecific binding. Finally, in vivo experiments confirm TCF‐Cy7(Py)‐TCF nanoaggregates function as nanoPS for synergistic phototherapy, offering a simple yet effective strategy to design single‐component PS for clinical translation.

Crystallization Control of Anionic Thiacalixarenes on Silicon Surface Coated with Cationic Poly(ethyleneimine).

Surface modification of solid substrates with organic molecules and polyelectrolytes is a promising strategy toward advanced soft materials due to the control of molecular arrangement and supramolecular organization; however, understanding the nature of interactions within the assembly is challenging. Here a facile approach to the control of the architecture of calixarene macrocycles on soft surfaces is presented through the interplay of weak interactions involving a solid silicon substrate, a cationic polyelectrolyte layer, and anionic sulfonatothiacalix[4]arene (STCA). Topological analysis of atomic force microscopy (AFM) images of STCA on silicon, as well as silicon wafers modified with neutral polyethylenimine (PEI) and cationic PEI-H+, indicates different surface morphology and assembly behavior of STCA on such substrates. Drop-casting a calixarene solution onto silicon induces the formation of chaotically oriented needle crystals. When there is globular PEI, a nucleation point for the STCA crystals is formed on the polyelectrolyte surface, which grows into rosette structures. In contrast, protonated PEI with a chain-like structure alters the self-organization of STCA on silicon surfaces, leading to a dense uniform fiber-like network. Density functional theory modeling of the system components' self-assembly reveals thermodynamically favorable face-to-face antiparallel aggregation of STCA monomers and contribution of H-bonding into PEI(PEI-H+)-STCA and Si-STCA association.

Exploring the potential of fibrinogen hydrolysates as enhancers for myofibrillar protein gelation: Insights into molecular assembly behavior

This study explored the use of pig blood fibrinogen hydrolysates, enzymatically hydrolyzed with trypsin and flavorzyme, to enhance myofibrillar protein gels, addressing issues like poor gel strength and water loss in meat products. By incorporating varying concentrations of fibrinogen hydrolysates into myofibrillar proteins, heat-induced gels were prepared. The composite gels showed improved textural properties, rheological characteristics and water-holding capacity. Scanning electron microscopy and atomic force microscopy analyses revealed a uniform, dense surface and an orderly internal structure in the composite gels. The study also noted decreased α-helix and random coil and increased β-sheet and β-turn contents, indicating a more ordered secondary structure. Hydrophobic interactions and disulfide bonds were identified as key factors in enhancing gelation, and a model was proposed to explain these molecular effects. This research demonstrates a potential of fibrinogen hydrolysates to improve quality and structure of myofibrillar protein gels designed for high-quality meat products.

Giant dimeric donors for all-giant-oligomer organic solar cells with efficiency over 16% and superior photostability

Increasing the molecular weight while maintaining mono-dispersity has been proved crucial in innovating high-performance photovoltaic materials in giant oligomeric acceptors. However, developing efficient giant oligomeric donors to replace the batch-varied polymers remains challenging due to a lack of design principles. Here, by designing two unique isomeric rhodanine-based linkers, we successfully regulate the assembly behaviors of giant dimeric donors (G-Dimer-Ds) and fabricate the first all-giant-oligomer OSCs pairing with giant dimeric acceptor DY. Multiple characterizations demonstrate the small homo-molecular interaction with strong thermal-driven assembly capability in G-Dimer-D2 simultaneously facilitates reducing energetic disorder, improving charge transport and obtaining stable morphology, resulting in a satisfactory efficiency of 15.70% and long-term photostability with an extrapolated T80 of ca.10,000 hours, and further enhancing thermal-driven assembly promotes efficiency of 16.05%. Our results provide construction approaches on efficient giant donors, and propose a promising type of OSC with completely definite structures, high efficiency and superior stability.