Self-assembly Of Particles Research Articles

Self-Assembled Virus-Like Particle Vaccines via Fluorophilic Interactions Enable Infection Mimicry and Immune Protection.

Influenza epidemics persistently threaten global health. Vaccines based on virus-like particles (VLPs), which resemble the native conformation of viruses, have emerged as vaccine candidates. However, the production of VLPs via genetic engineering remains constrained by challenges such as low yields, high costs, and being time consuming. In this study, a novel VLP platform is developed that could mimic infection and confer influenza protection through fluorination-driven self-assembly. The VLPs closely mimick the key steps in viral infection including dendritic cell (DC) attachment and pH-responsive endo-lysosomal escape, which enhances DC maturation and antigen cross-presentation. It is also observed that the VLPs migrate from the injection site to the draining lymph nodes efficiently. Immunization with VLPs triggers both Th1 and Th2 cellular responses, thereby inducing an improved CD8+ T cell response along with strong antigen-specific antibody responses. In several infected mouse models, VLP vaccines ameliorate weight loss, lung virus titers, pulmonary pathologies, and confer full protection against H1N1, H6N2, H9N2, and mixed influenza viruses. Therefore, the results support the potential of VLPs as an effective influenza vaccine with improved immune potency against infection. A methodology to generate VLPs based on fluorophilic interactions, which can be a general approach for development of pathogenic VLPs, is reported.

Assembly of Covalent Organic Frameworks into Colloidal Photonic Crystals.

Self-assembly of colloidal particles into ordered superstructures is an important strategy to discover new materials, such as catalysts, plasmonic sensing materials, storage systems, and photonic crystals (PhCs). Here we show that porous covalent organic frameworks (COFs) can be used as colloidal building particles to fabricate porous PhCs with an underlying face-centered cubic (fcc) arrangement. We demonstrate that the Bragg reflection of these can be tuned by controlling the size of the COF particles and that species can be adsorbed within the pores of the COF particles, which in turn alters the Bragg reflection. Given the vast number of existing COFs, with their rich properties and broad modularity, we expect that our discovery will enable the development of colloidal PhCs with unprecedented functionality.

Exploring the Landscape of the PP7 Virus-like Particle for Peptide Display.

Self-assembling virus-like particles (VLPs) can tolerate a wide degree of genetic and chemical manipulation to their capsid protein to display a foreign molecule polyvalently. We previously reported the successful incorporation of foreign peptide sequences in the junction loop and onto the C-terminus of PP7 dimer VLPs, as these regions are accessible for surface display on assembled capsids. Here, we report the implementation of a library-based approach to test the assembly tolerance of PP7 dimer capsid proteins to insertions or terminal extensions of randomized 15-mer peptide sequences. By performing two iterative rounds of assembly-based selection, we evaluated the degree of favorability of all 20 amino acids at each of the 15 randomized positions. Deep sequencing analysis revealed a distinct preference for the inclusion of hydrophilic peptides and negatively charged amino acids (Asp and Glu) and the exclusion of positively charged peptides and bulky and hydrophobic amino acid residues (Trp, Phe, Tyr, and Cys). Within the libraries tested here, we identified 4000 to 22,000 unique 15-mer peptide sequences that can successfully be displayed on the surface of the PP7 dimer capsid. Overall, the use of small initial libraries consisting of no more than a few million members yielded a significantly larger number of unique and assembly-competent VLP sequences than have been previously characterized for this class of nucleoprotein particle.

Super-Radiant SERS Enhancement by Plasmonic Particle Gratings.

Despite recent developments, surface-enhanced Raman spectroscopy (SERS) applications face challenges in achieving both high sensitivity and uniform Raman signals over a large area. Using the directional self-assembly of plasmonic nanoparticles in lattice structures, we show how one can increase the SERS signal 43-fold over randomly aligned gold nanoparticles without relying on the photoluminescence of Rhodamine 6G. For this study, we have chosen the lattice constant for an off-resonant case that matches the lattice resonance and super-radiant plasmon mode along the particle chain. Supported by electromagnetic simulations, we systematically analyze the radiative components of the plasmon modes by varying the particle size while keeping the lattice periodicity constant. We perform polarization-dependent SERS measurements and compare them with other standard SERS excitation wavelengths. Using the self-assembled plasmonic particle lattice, we have developed an effective SERS substrate that provides a significantly higher signal with 73% less surface coverage. This colloidal approach enables the cost-effective and scalable fabrication of highly sensitive, uniform, and polarization-dependent SERS substrates.

GraphVAMPnets for uncovering slow collective variables of self-assembly dynamics.

Uncovering slow collective variables (CVs) of self-assembly dynamics is important to elucidate its numerous kinetic assembly pathways and drive the design of novel structures for advanced materials through the bottom-up approach. However, identifying the CVs for self-assembly presents several challenges. First, self-assembly systems often consist of identical monomers, and the feature representations should be invariant to permutations and rotational symmetries. Physical coordinates, such as aggregate size, lack high-resolution detail, while common geometric coordinates like pairwise distances are hindered by the permutation and rotational symmetry challenges. Second, self-assembly is usually a downhill process, and the trajectories often suffer from insufficient sampling of backward transitions that correspond to the dissociation of self-assembled structures. Popular dimensionality reduction methods, such as time-structure independent component analysis, impose detailed balance constraints, potentially obscuring the true dynamics of self-assembly. In this work, we employ GraphVAMPnets, which combines graph neural networks with a variational approach for Markovian process (VAMP) theory to identify the slow CVs of the self-assembly processes. First, GraphVAMPnets bears the advantages of graph neural networks, in which the graph embeddings can represent self-assembly structures in high-resolution while being invariant to permutations and rotational symmetries. Second, it is built upon VAMP theory, which studies Markov processes without forcing detailed balance constraints, which addresses the out-of-equilibrium challenge in the self-assembly process. We demonstrate GraphVAMPnets for identifying slow CVs of self-assembly kinetics in two systems: the aggregation of two hydrophobic molecules and the self-assembly of patchy particles. We expect that our GraphVAMPnets can be widely applied to molecular self-assembly.

Understanding the formation of particle bands and fingering patterns during evaporation of a sessile droplet containing colloids

Sessile droplets containing dispersed colloids evaporate on substrates leaving distinct deposition patterns. Applications using the droplets technique require a critical understanding of the complex particle dynamics that affect the deposition pattern. The fingering-like pattern formed when surfactant-laden droplets containing dispersed colloids evaporate is not yet well understood. The lateral imbalanced capillary meniscus forces (CMFs) between particles moving along the Marangoni vortex (MV) cluster particles into bands that deposit to form the fingering-like pattern. This work investigates the effect of particle shape, particle, and surfactant concentration on the phenomenon. Further, the importance of the contact angle and contact line (CL) dynamics of the droplet is also discussed. The results demonstrate that manipulating these parameters can control the band formation and the resulting deposition pattern. The findings of this work would be pivotal for a critical understanding of particle self-assembly and pattern morphologies of evaporating surfactant-laden droplets.

Porous Self-Assemblies Mediated by Dumbbell Particles as Cross-Linking Agents.

Self-assembly of colloidal particles is emerging as a promising approach for producing novel materials. These colloidal particles can be synthesized with protrusions (lobes) on their surfaces that allow the formation of porous structures with a wide range of applications. Using Langevin dynamics simulations, we studied self-assembly in the binary mixtures of lobed colloidal particles with variations in their lobe sizes to investigate the feasibility of using dumbbell particles (with two lobes) as cross-linkers to increase the porosity in self-assembled morphologies. Each binary system was formed by mixing the dumbbell particles with one of the following types of particles: trigonal planar (three lobes), tetrahedral (four lobes), trigonal bipyramidal (five lobes), and octahedral (six lobes). We observed that the lobe size on each particle can be tuned to favor the formation of random aggregates and spherical aggregates when the lobes are larger and well-ordered crystalline structures when the lobes are smaller. We also observed that these polydisperse systems form self-assembled structures characterized by porosities higher than those of the structures formed by the monodisperse systems. These results indicate that the lobe size is an important design feature that can be optimized to achieve desired structures with distinct morphologies and porosities, and the dumbbell particles are effective cross-linking agents to enhance the porosity in self-assembled structures.

Non-Classical Self-Assembly of Anisotropic Magneto-Organosilica Janus Particles Possessing Surfactant Properties and the Field-Triggered Breakdown of Surface Activity and Amphiphilic Properties.

Using colloidal particles as models to understand processes on a smaller scale is a precious approach. Compared to molecules, particles are less defined, but their architecture can be more complex and so is their long-range interaction. One can observe phenomena that are unknown or much more difficult to realize on the molecular level. The current paper focuses on particle-based surfactants and reports on numerous unexpected properties. The main goal is creating an amphiphilic system with responsiveness in surface activity and associated self-organization phenomena depending on applying an external trigger, preferably a physical field. A key step is the creation of a Janus-type particle characterized by two types of dipoles (electric and magnetic) which geometrically stand orthogonal to each other. In a field, one can control which contribution and direction dominate the interparticle interactions. As a result, one can drastically change the system's properties. The features of ferrite-core organosilica-shell particles with grain-like morphology modified by click chemistry are studied in response to spatially isotropic and anisotropic triggers. A highly unusual aggregation-dissolution-reaggregation sequence w as discovered. Using a magnetic field, one can even switch off the amphiphilic properties and use this for the field-triggered breaking of multiphase systems such as emulsions.

Heterogeneous Dynamics of Sheared Particle-Laden Fluid Interfaces with Janus Particle Doping.

The formation of particle clusters can substantially modify the dynamics and mechanical properties of suspensions in both two and three dimensions. While it has been well established that large network-spanning clusters increase the rigidity of particle systems, it is still unclear how the presence of localized nonpercolating clusters affects the dynamics and mechanical properties of particle suspensions. Here, we introduce self-assembled localized particle clusters at a fluid-fluid interface by mixing a fraction of Janus particles in a monolayer of homogeneous colloids. Each Janus particle binds to a few nearby homogeneous colloids, resulting in numerous small clusters uniformly distributed across the interface. Using a custom magnetic rod interfacial stress rheometer, we apply linear oscillatory shear to the particle-laden fluid interface. By analyzing the local affine deformation of particles from optical microscopy, we show that particles in localized clusters experience substantially lower shear-induced stretching than their neighbors outside clusters. We hypothesize that such heterogeneous dynamics induced by particle clusters increase the effective surface coverage of particles, which in turn enhances the shear moduli of the interface, as confirmed by direct interfacial rheological measurements. Our study illustrates the microscopic dynamics of small clusters in a shear flow and reveals their profound effects on the macroscopic rheology of particle-laden fluid interfaces. Our findings open an avenue for designing interfacial materials with improved mechanical properties via the control of formation of localized particle clusters.

Particle Network Self-Assembly of Similar Size Sub-Micron Calcium Alginate and Polystyrene Particles Atop Glass.

Particle-mediated self-assembly, such as nanocomposites, microstructure formation in materials, and core-shell coating of biological particles, offers precise control over the properties of biological materials for applications in drug delivery, tissue engineering, and biosensing. The assembly of similar-sized calcium alginate (CAG) and polystyrene sub-micron particles is studied in an aqueous sodium nitrate solution as a model for particle-mediated self-assembly of biological and synthetic mixed particle species. The objective is to reinforce biological matrices by incorporating synthetic particles to form hybrid particulate networks with tailored properties. By varying the ionic strength of the suspension, the authorsalter the energy barriers for particle attachment to each other and to a glass substrate that result from colloidal surface forces. The particles do not show monotonic adsorption trend to glass with ionic strength. Hence, apart from DLVO theory-van der Waals and electrostatic interactions-the authors further consider solvation and bridging interactions in the analysis of the particulate adsorption-coagulation system. CAG particles, which support lower energy barriers to attachment relative to their counterpart polystyrene particles, accumulate as dense aggregates on the glass substrate. Polystyrene particles adsorb simultaneously as detached particles. At high electrolyte concentrations, where electrostatic repulsion is largely screened, the mixture of particles covers most of the glass substrate; the CAG particles form a continuous network throughout the glass substrate with pockets of polystyrene particles. The particulate structure is correlated with the adjustable energy barriers for particle attachment in thesuspension.

Dynamics Simulation of Self-assembly of Disc-like Nanoparticles

Brownian dynamics of self-assembly of disklike nanoparticles is simulated with a generalized aspherical model using tabulated method of force field parameters. The present model uses the force field of all-atom objects using tabulated table parameters which inherently reflects the specification of shape and component of nanoparticle. We study the self-assembly of disc-like particles. The transition mechanism is analyzed and discussed.

Osteopontin targeted non-invasive nanoprobes with amplified surface plasmon resonance for photothermally enhanced multimodal precision imaging of vulnerable atherosclerotic plaques

Effective strategies for accurate differentiation of the vulnerable atherosclerosis (AS) plaques at molecular level for clinical diagnosis have yet been developed. Herein, a versatile SAmOCP nanoprobe, is constructed by sealing up the multinuclear gold self-assembled nanospheres by hollow mesoporous silicon shell and then decorating the surfaces with Chlorine e6 (Ce6)-conjugated osteopontin antibody (OPN Ab), followed by filling the internal cavity with perfluoropentane (PFP) for precise in vivo targeting and multi-modal imaging of the vulnerable AS plaques. SAmOCP nanoprobes actively recognize the foam cells and specifically target the vulnerable AS plaques in vivo. Relying on the exceptional photo-to-heat conversion properties resulting from enhanced localized surface plasmon resonance (LSPR) effects of Au self-assembled particles, the encapsulated liquid PFP could transform into abundant microbubbles when AS plaque-rich regions were overheated by 808-nm laser irradiation, enabling hyperthermia-enhanced microbubbles generation, thereby endowing nanoprobes with significantly enhanced ultrasonic imaging capacity. SAmOCP nanoprobes exhibit a triple-modality diagnostic efficacy of ultrasound/fluorescence/photothermal imaging for in vivo precise detection of vulnerable AS plaques at molecular level. Together, SAmOCP nanoprobes overcome the difficulty in identifying the vulnerable AS plaque for clinic practice, holding great promise for vulnerable AS diagnosis.

A Novel Family of Stable Polyelectrolyte Complexes Based on Mixed Olefins-Maleic Anhydride Copolymer.

In the present study, the copolymer of mixed olefins included in unetherified gasoline and maleic anhydride (PUGM) was prepared by self-stabilized precipitation polymerization (2SP) and employed for the synthesis of a new family of stable polyelectrolyte complexes (PECs). Polyanionic saponified PUGM partially grafted with methoxy poly(ethylene glycol) (PUGMS-g-mPEG) and polycationic quaternized PUGM (PUGMQ) were both derived from PUGM via the facile modification of anhydride groups. The particle size, zeta potential, morphology, and stability of self-assembled PEC particles were investigated thoroughly. Strikingly, the introduction of long mPEG side chains (Mn = 4000) had a remarkable effect on the self-assembled particles, which displayed a constant particle size of ∼200 nm regardless of varying n+/n-. Moreover, it also enhanced the salt tolerance and long-term stability of PEC particles significantly. Our work not only provides an effective approach to PECs from petroleum resources with low cost but also deepens the understanding of the relationship between the chain structure of polyelectrolytes and the stability of PECs.

Spatial characterization of peptide nucleic acid molecularly imprinted inverse opal

The combination of molecularly imprinted polymers (MIPs) and inverse opals (IO) have been a point of interest in the past few years due to their potential in sensing applications. At the same time, peptide nucleic acid (PNA) is a stable analogue to natural occurring genetic material. In this study, we describe the preparation and characterization of a PNA imprinted matrix, based on the controlled self-assembly of organized silica particles (SiPs) arrays. The degree of organization of the silica arrays are compared to the organization of the cavities after the removal of the SiPs, using spatial statistical analysis. This analysis of the Voronoi tessellations, pair correlation functions and bond order showed that the successfully formed arrays contain a high degree of quasi-hexagonal (hexatic) organization of the cavities, with both global and local order. The adsorption analysis of the materials show potential for developing future materials with tunable structural reflective properties, such as on-site, color- changing genetic material sensor.Graphical abstract

Self-assembled mesoporous particles of Antheraea pernyi silk fibroin for encapsulation and sustained release of 5-fluorouracil

Mesoporous particles have attracted considerable attention in drug delivery system, because they can offer fast mass transport and overcome the diffusion restriction as occurred in micro/nano- porous particles. Conventional mesoporous particles are generally dominated by inorganic compounds, little concern has been raised over biodegradable organic polymers, especially silk fibroin. Here, we show that Antheraea pernyi (A. pernyi) silk fibroin, rich in Arg-Gly-Asp (RGD) moiety, can be developed into mesoporous particles via self-assembly in a direct and eco-friendly (without any organic solvents) manner for sustained release of 5-fluorouracil (5-FU). By cultivating a mild condition at 40 ℃, a mesoporous structure was successfully achieved without any foreign organic solvents. The self-assembled mesoporous particles were quasi-spherical in shape with an average diameter of 1.58 µm. Mesopores ran through the entire particles to construct a divergent structure with external pore diameters ranging from 30 to 60 nm and internal pore width of 6.225 nm. The mesoporous particles were predominated by β-sheet conformation (∼45%), which effectively reduced the weight-loss ratio to 2.6%. 5-FU was encapsulated into the mesoporous particles by hydrogen bonding and van der Waals force as well as ionic interactions. Drug loading efficiency and encapsulation efficiency were found to be 26.24% and 50.36%, respectively. The mesoporous particles enabled sustained drug release, with approximately 90% release after 110 h. After a small burst release (20%) of the surface-bound 5-FU, a slower linear release dominated by Fickian-diffusion occurred. These features together with the excellent biocompatibility of A. pernyi silk indicated that the self-assembled mesoporous particles would be an ideal carrier for sustained drug release to meet critical requirements of biomaterials. Furthermore, without any foreign materials, this one-step strategy may offer new green chemistry approaches as well as options to load bioactive drugs.

Erratum to: Self-Assembly of Gel-Like Particles and Vesicles in Solutions of Polymers with Amphiphilic Repeat Unit

Erratum to: Self-Assembly of Gel-Like Particles and Vesicles in Solutions of Polymers with Amphiphilic Repeat Unit

Zeta potential and nanodiamond self assembly assisted diamond growth on lithium niobate and lithium tantalate single crystal

This study focuses on the self-assembly and subsequent diamond growth on SiO2 buffered lithium niobate (LNO) and lithium tantalate (LTO) single crystals. The zeta-potential of LNO and LTO single crystal were measured as a function of pH. They were found to be negative in the pH range 3.5–9.5. The isoelectric point for LNO was found to be at pH ∼ 2.91 and that of LTO to be at pH ∼ 3.20. X-ray photoelectron spectroscopy performed on the surfaces show presence of oxygen groups which may be responsible for the negative zeta potential of the crystals. Self-assembly of nanodiamond particles on LTO and LNO, using nanodiamond colloid, were studied. As expected, high nanodiamond density was seen when self-assembly was done using a positively charged nanodiamond particles. Diamond growth was attempted on the nanodiamond coated substrates but they were found to be unsuitable for direct growth due to disintegration of substrates in diamond growth conditions. A ∼100 nm thick silicon dioxide layer was deposited on the crystals, followed by nanodiamond self assembly and diamond growth. Thin diamond films were successfully grown on both coated crystals. The diamond quality was analysed by Raman spectroscopy and atomic force microscopy.

Self-Assembly and Sorting of Graphene Nanoplatelets and Spherical Colloidal Particles via Sessile Droplet Evaporation in Saturated Alcohol Vapor

We investigated the dried deposit patterns of quasi-two-dimensional graphene nanoplatelets (GNP) on hydrophilic glass via aqueous sessile droplet evaporation in a saturated alcohol vapor atmosphere. In addition, we studied both the size- and shape-dependent self-assembly and self-sorting of colloids by employing droplets containing bidispersed suspensions comprising GNP and bulk three-dimensional colloidal particles, e.g., polystyrene microspheres (PS). We report distinct self-sorting regimes as the PS diameter Dp varies between 0.1 and 6.4 μm. Under ambient air, the droplet evaporation does not yield discernible self-sorting between GNP and PS. Under saturated alcohol vapor, a critical Dp = 1.1 μm exists, for which the self-sorting does not occur. For Dp < 1.1 μm, the PS sort out from the bidispersed suspension to form the outermost ring of the deposit. The deposit pattern reverses for Dp > 1.1 μm, and GNP deposit on the outermost edge. We corroborate experimental observations with a theoretical model based on the size- and shape-dependent interfacial forces between the colloids.

What is the role of PEO chains in the assembly of core-corona supraparticles in aqueous dispersions?

Hypothesis The assembly of core-corona supraparticles in aqueous dispersions has been regularly assisted by auxiliary monomers/oligomers which modify the individual particles with, e.g., surface grafting of polyethylene oxide (PEO) chains or other hydrophilic monomers. However, this modification complicates the preparation and purification procedures and increases potential upscaling efforts. Hybrid polymer-silica core-corona supracolloids could be more simply assembled if the PEO chains from surfactants, typically used by default as polymer stabilizers, concomitantly act as assembly promotors. The supracolloids assembly could therefore be more easily achieved without requiring particles functionalization or post-purification steps. Methods The self-assembly of supracolloidal particles prepared with PEO-surfactant stabilized (Triton X-405) and/or PEO-grafted polymer particles is compared to differentiate the roles of the PEO chains in the assembly of core-corona supraparticles. Using time-resolved dynamic light scattering (DLS) and cryogenic transmission electron microscopy(cryo-TEM), the effect of concentration of PEO chains (from surfactant) on the kinetics and dynamics of supracolloids assembly is investigated. Self-consistent field (SCF) lattice theory was used to numerically study the distribution of PEO chains at the interfaces present in the supracolloidal dispersions. Findings The PEO based surfactant can be used as assembly promoter of core-corona hybrid supracolloids due to its amphiphilic nature and via establishing hydrophobic interactions. The concentration of the PEO surfactant, and especially the PEO chains distribution over the different interfaces, crucially affect the supracolloids assembly. A simplified pathway for preparing hybrid supracolloidal particles with a well-controlled corona coverage over polymer cores is presented.

Polyhedral zeolitic imidazolate frameworks three-dimensional photonic crystals for highly sensitive chlorinated vapors sensing

Chlorinated vapors, as one of the poisonous volatile organic compounds (VOCs), seriously pollute the environment and threaten human health. It still remains a major challenge for designing reliable chlorinated vapors sensing materials with high sensitivity. Herein, we propose a simple yet powerful optical sensor based on zeolitic imidazolate frameworks ZIF-8 three-dimensional photonic crystals (3D PCs), which keeps high efficiency in vapor sensing through varying their effective refractive index (RI). ZIF-8 3D PCs sensors with tunable crystal facets and photonic bandgap were prepared by self-assembly of monodisperse polyhedral ZIF-8 particles, which are truncated rhombic dodecahedral (TRD)-, rhombic dodecahedral (RD)-, truncated cubic (TC)-, and spherical (Sphere) ZIF-8 3D PCs sensors. The application of polyhedral ZIF-8 3D PCs sensors for chlorinated vapors detection was investigated. The selectivity was found to be closely related to the exposed crystal facets, and the TRD ZIF-8 3D PCs sensor exhibited excellent selectivity, sensitivity (0.514 nm ppm−1), and sensing performance for chlorobenzene (C6H5Cl) vapor, the ultrafast response time (≤1 s) and remarkable long-term stability and recyclability, which might ultimately benefit for practical VOCs sensing applications.