Current status and future developments in preparation and application of nonspherical polymer particles

Morphological Control of Single-Concave Elastomeric Colloid through Cross-Linking and Osmotic Pressure Variations for Chemical Delivery

In this paper, we propose a convenient and simple method for preparing elastomeric buckled spherical shells through double-emulsion solvent evaporation. In this method, polydimethylsiloxane (PDMS) is added to a water-in-oil-in-water emulsion system and stirred. As the solvent evaporates and the colloid solidifies, the aqueous phase inside formed cavity is squeezed out because of cross-linking stress, or this phase permeates the sphere, leading to loss of the internal water phase and the formation of a single-concave, bowl-shaped shell (i.e., a shell with buckling deformation). We could control the morphology of the produced colloidal particles by varying the concentrations of the permeant and cross-linking agent and the molecular weight of the permeant. Moreover, we propose a mechanism explaining the structural changes occurring during the double-emulsion polymerization process, focusing on cross-linking forces and osmotic pressure. Through leveraging of the shells' reversible swelling properties in solvents, the prepared buckled PDMS shells absorbed Nile red molecules into their cavity, which caused their expansion and restoration. Immersing these shells in ethanol resulted in release of the Nile red molecules. Thus, buckled PDMS shells prepared through the proposed method have potential for application in environmental sensing and drug delivery systems.

Preparation of Anisotropic Trimeric Poly(Ionic Liquid) Microspheres via Microwave-Assisted Dual-Crosslinked Seed Emulsion Polymerization

A microwave-assisted dual-crosslinked seed emulsion polymerization method is reported to prepare anisotropic trimeric poly(ionic liquid) (PIL) microspheres. First, ethylene glycol dimethacrylate (EGDMA)-crosslinked PIL (CPIL) seed microspheres are prepared. Then, the CPIL microspheres are swollen with ionic liquid (IL) emulsion containing divinylbenzene (DVB) and polymerized to form dual-crosslinked PIL (D-CPIL) microspheres under microwave irradiation. Finally, the D-CPIL microspheres are swollen with IL monomer emulsion to form trimeric morphology and polymerized to obtain trimeric PIL microspheres under microwave irradiation. The formation process of trimeric PIL microspheres is tracked using an optical microscope and their morphology is observed using scanning electron microscopy. Different from the repeat-swelling seed emulsion polymerization that needs dumbbell-like seed microspheres having gradient crosslinking or gradient surface wettability, this method depends on multiple local contraction forces in D-CPIL microspheres containing lowly crosslinked core and highlycrosslinked shell during swelling to form trimeric PIL microspheres. It is found that microwave polymerization is important because it can well retain trimeric morphology compared to conventional heating polymerization in oil or water baths. The morphology of trimeric PIL microspheres can be adjusted by changing the type and amount of crosslinkers, monomer/seed microsphere ratio, initiator dosage, temperature, etc.

Polymeric Drug Delivery Systems in Biomedicine

Our review examines the key aspects of using polymeric carriers in biomedicine. The section "Polymers for Biomedicine" provides an overview of different types of polymers, their structural features and properties that determine their use as drug delivery vehicles. The section "Polymeric Carriers" characterizes the role of polymeric delivery systems in modern medicine. The main forms of polymeric carriers are described, as well as their key advantages for drug delivery. The section "Preclinical and Clinical Trials of Polymeric Drug Carriers" reviews the examples of clinical and preclinical studies of polymeric forms used for antitumor therapy, therapy for bacterial and infectious diseases. The final section "Targeted Drug Delivery Systems" is devoted to the discussion of approaches, as well as ligands that provide targeted drug delivery using polymeric carriers. We have paid special attention to modern approaches for increasing the efficacy of antibacterial therapy using vector molecules.

Heat: A powerful tool for colloidal particle shaping

Colloidal particles of spherical shape are important building blocks for nanotechnological applications. Materials with tailored physical properties can be directly synthesized from self-assembled particles, as is the case for colloidal photonic crystals. In addition, colloidal monolayers and multilayers can be exploited as a mask for the fabrication of complex nanostructures via a colloidal lithography process for applications ranging from optoelectronics to sensing. Several techniques have been adopted to modify the shape of both individual colloidal particles and colloidal masks. Thermal treatment of colloidal particles is an effective route to introduce colloidal particle deformation or to manipulate colloidal masks (i.e. to tune the size of the interstices between colloidal particles) by heating them at elevated temperatures above a certain critical temperature for the particle material. In particular, this type of morphological manipulation based on thermal treatments has been extensively applied to polymer particles. Nonetheless, interesting shaping effects have been observed also in inorganic materials, in particular silica particles. Due to their much less complex implementation and distinctive shaping effects in comparison to dry etching or high energy ion beam irradiation, thermal treatments turn out to be a powerful and competitive tool to induce colloidal particle deformation. In this review, we examine the physicochemical principles and mechanisms of heat-induced shaping as well as its experimental implementation. We also explore its applications, going from tailored masks for colloidal lithography to the fabrication of colloidal assemblies directly useful for their intrinsic optical, thermal and mechanical properties (e.g. thermal switches) and even to the synthesis of supraparticles and anisotropic particles, such as doublets.

Preparation of Surface-Wrinkled Silica-Polystyrene Colloidal Composite Particles

In this work, we report a facile emulsion swelling route to prepare surface-wrinkled silica-polystyrene (SiO2-PS) composite particles. Submicrometer-sized, near-spherical SiO2-PS composite particles were first synthesized by dispersion polymerization of styrene in an ethanol/water mixture, and then, surface-wrinkled SiO2-PS particles were obtained by swelling the SiO2-PS particles with a toluene/water emulsion and subsequent drying. It is emphasized that no surface pretreatment on the SiO2-PS composite particles is required for the formation of the wrinkled surface, and the most striking feature is that the surface-wrinkled particle was not deformed from a single near-spherical SiO2-PS composite particle but from many ones. The influence of various swelling parameters including toluene/particle mass ratio, surfactant concentration, stirring rate, swelling temperature, swelling time, and silica size on the morphology of the composite particles was studied. This method represents a new paradigm for the preparation of concave polymer colloids.

Polymeric Nanoparticles for Drug Delivery

The recent emergence of nanomedicine has revolutionized the therapeutic landscape and necessitated the creation of more sophisticated drug delivery systems. Polymeric nanoparticles sit at the forefront of numerous promising drug delivery designs, due to their unmatched control over physiochemical properties such as size, shape, architecture, charge, and surface functionality. Furthermore, polymeric nanoparticles have the ability to navigate various biological barriers to precisely target specific sites within the body, encapsulate a diverse range of therapeutic cargo and efficiently release this cargo in response to internal and external stimuli. However, despite these remarkable advantages, the presence of polymeric nanoparticles in wider clinical application is minimal. This review will provide a comprehensive understanding of polymeric nanoparticles as drug delivery vehicles. The biological barriers affecting drug delivery will be outlined first, followed by a comprehensive description of the various nanoparticle designs and preparation methods, beginning with the polymers on which they are based. The review will meticulously explore the current performance of polymeric nanoparticles against a myriad of diseases including cancer, viral and bacterial infections, before finally evaluating the advantages and crucial challenges that will determine their wider clinical potential in the decades to come.

Confinement Effects in Droplet Formation on a Solid Particle

Formation of a droplet around a spherical solid particle in supersaturated vapor is considered. The number and stability of equilibrium solutions in a closed small system are studied in the canonical ensemble in comparison to an open system in the grand canonical ensemble. Depending on the system's parameters, two modes exist in the canonical ensemble: the first one with only one solution and the second one with three solutions; the presence of the third solution is due to confinement. The analysis is conducted first on a macroscopic thermodynamic level of description, and then the results are supported by studies within two versions of classical density functional theory: the square-gradient approximation with the Carnahan-Starling equation of state for hard spheres on a completely wettable particle and the random-phase approximation with the fundamental measure theory on a poorly wettable particle. In the latter case, a solution breaking the spherical symmetry is observed at a small total number of molecules.

Preparation and application of hemostatic microspheres containing biological macromolecules and others

Bleeding from uncontrollable wounds can be fatal, and the body's clotting mechanisms are unable to control bleeding in a timely and effective manner in emergencies such as battlefields and traffic accidents. For irregular and inaccessible wounds, hemostatic materials are needed to intervene to stop bleeding. Hemostatic microspheres are promising for hemostasis, as their unique structural features can promote coagulation. There is a wide choice of materials for the preparation of microspheres, and the modification of natural macromolecular materials such as chitosan to enhance the hemostatic properties and make up for the deficiencies of synthetic macromolecular materials makes the hemostatic microspheres multifunctional and expands the application fields of hemostatic microspheres. Here, we focus on the hemostatic mechanism of different materials and the preparation methods of microspheres, and introduce the modification methods, related properties and applications (in cancer therapy) for the structural characteristics of hemostatic microspheres. Finally, we discuss the future trends of hemostatic microspheres and research opportunities for developing the next generation of hemostatic microsphere materials.

Synthesis of dimpled polymer-silica nanocomposite particles by interfacial swelling-based seeded polymerization

Dimpled polymer-silica nanocomposite particles have the combined advantages of dimpled particles and polymer-silica nanocomposite particles. This study presents a novel approach to prepare these particles by interfacial swelling-based seeded polymerization. Polystyrene-silica (PS-SiO2) nanocomposite particles are first prepared by emulsion polymerization of styrene in the presence of glycerol-functionalized silica sols and then dimpled polymer-SiO2 particles are fabricated by interfacial swelling of butyl acrylate (BA)/toluene and subsequent seeded polymerization of BA with the PS-SiO2 particles as seeds. The effects of different parameters, such as the amount of surfactant used in the PS-SiO2/H2O dispersion, BA/toluene mass ratio, PS-SiO2/H2O mass ratio and stirring rate, on the formation of the dimpled particles are investigated. Optimization of the seeded polymerization conditions allows a relatively high percentage of dimpled particles to be achieved.

Research Status of Dendrimer Micelles in Tumor Therapy for Drug Delivery

Dendrimers are a family of polymers with highly branched structure, well-defined composition, and extensive functional groups, which have attracted great attention in biomedical applications. Micelles formed by dendrimers are ideal nanocarriers for delivering anticancer agents due to the explicit study of their characteristics of particle size, charge, and biological properties such as toxicity, blood circulation time, biodistribution, and cellular internalization. Here, the classification, preparation, and structure of dendrimer micelles are reviewed, and the specific functional groups modified on the surface of dendrimers for tumor active targeting, stimuli-responsive drug release, reduced toxicity, and prolonged blood circulation time are discussed. In addition, their applications are summarized as various platforms for biomedical applications related to cancer therapy including drug delivery, gene transfection, nano-contrast for imaging, and combined therapy. Other applications such as tissue engineering and biosensor are also involved. Finally, the possible challenges and perspectives of dendrimer micelles for their further applications are discussed.

Camptothecin-based prodrug nanomedicines for cancer therapy

Camptothecin (CPT) is a cytotoxic alkaloid that attenuates the replication of cancer cells via blocking DNA topoisomerase 1. Despite its encouraging and wide-spectrum antitumour activity, its application is significantly restricted owing to its instability, low solubility, significant toxicity, and acquired tumour cell resistance. This has resulted in the development of many CPT-based therapeutic agents, especially CPT-based nanomedicines, with improved pharmacokinetic and pharmacodynamic profiles. Specifically, smart CPT-based prodrug nanomedicines with stimuli-responsive release capacity have been extensively explored owing to the advantages such as high drug loading, improved stability, and decreased potential toxicity caused by the carrier materials in comparison with normal nanodrugs and traditional delivery systems. In this review, the potential strategies and applications of CPT-based nanoprodrugs for enhanced CPT delivery toward cancer cells are summarized. We appraise in detail the chemical structures and release mechanisms of these nanoprodrugs and guide materials chemists to develop more powerful nanomedicines that have real clinical therapeutic capacities.

Optically active polymer particles with programmable surface microstructures constructed using chiral helical polyacetylene

Micro/nanoparticles with surface microstructures have attracted tremendous attention due to their fascinating structures and properties. Herein, we present the first strategy for producing optically active polymer particles with varying surface microstructures via a template surface modification process in which achiral particles act as the template and helical substituted polyacetylene acts as the chiral component. To prepare the designed chiral-functionalized particles, template particles were first reacted with propargylamine to produce alkynylated template particles. The alkynylated templates further participated in the polymerization of chiral alkyne monomers through a surface grafting precipitation polymerization approach, resulting in achiral particles with surface microstructures covalently bonded with a chiral helical polymer. SEM images ascertain the production of chiral-functionalized particles showing various shapes (jar-like, golf ball-like, and raspberry-like particles). Furthermore, CD and UV-vis absorption spectra demonstrate that the grafted polyacetylene chains adopt a predominantly single-handed helical conformation, thereby affording composite particles with optical activity. Using the established protocol, numerous advanced chiral-functionalized micro/nanostructures are expected to be designed and constructed.

Manipulating the morphology of colloidal particles via ion beam irradiation: A route to anisotropic shaping

Ion beam irradiation of spherical colloidal particles is a viable route to induce particle deformation, especially to get anisotropic shapes. Even though less common in comparison with dry etching techniques, different types of morphological changes can be attained depending on the process parameters (angle of incidence, energy, fluence of the ion beam, type of ion, temperature) and on particle material and initial particle arrangement (crystalline or disordered, made up of isolated or closely-packed particles). The technique can be harnessed to get anisotropic deformation of spherical colloidal particles into an ellipsoidal shape, but also to tailor the interstices between closely-packed colloidal particles, to get particle necking and coalescence as well as particle rearrangement. As such, particle deformation based on ion irradiation can find diverse applications from synthesis of ellipsoidal particles to modified templates for colloidal lithography. In this review, we examine in detail the principles and models of colloidal particle shaping via ion beam irradiation, the influence of process parameters on particle morphology and the applications of irradiated particles.

Periodic Patchy Spheres Self-Assembled by AmBCAn' Multiblock Terpolymers

We have designed A_mBCA_n^' multiblock terpolymers and studied their self-assembly using self-consistent field theory, aiming to generate the periodically arranged patchy spheres and thus to clarify the regulation mechanism of the number of patches. A number of two-dimensional phase diagrams are constructed for three typical architectures A₂BCA₂^', A₂BCA₃^', and A₃BCA₂^'. Four kinds of stable patchy spheres with the number of patches as 2 (S₂), 4 (S₄), 5 (S₅), and 6 (S₆) are obtained. These phases follow a common transition sequence of S₂ → S₄ → S₅ → S₆ along with the increasing of the volume fraction of C-block (f_C), which forms the core sphere patched with B-domains. Moreover, the S₆ phase exhibits the widest stability window, while S₅ has the narrowest one. The increased arms of A'-blocks in A₂BCA₃^' architecture deflect the phase boundaries toward large f_C and accordingly expand the regions of these patchy spheres due to the amplified effect of spontaneous curvature. In contrast, the increased arms of A-blocks in A₃BCA₂^' remarkably expands the window of S₆ but narrows those of the other patchy spheres, which is mainly caused by increased packing frustration resulting from the reduced extension of the more divided A-blocks. The widest window of the S₆ phase reaches Δf_C ∼ 0.13, which is readily accessed by experiment. Our work not only demonstrates a self-assembly strategy to engineer the patchy spheres, but also sheds light on the regulation mechanism of the patchy number.

Synthetic Strategies for Polymer Particles with Surface Concavities

Over the past decade or so, there has been increasing interest in the synthesis of polymer particles with surface concavities, which mainly include golf ball-like, dimpled and surface-wrinkled polymer particles. Such syntheses generally can be classified into direct polymerization and post-treatment on preformed polymer particles. This review aims to provide an overview of the synthetic strategies of such particles. Some selected examples are given to present the formation mechanisms of the surface concavities. The applications and future development of these concave polymer particles are also briefly discussed. This article is protected by copyright. All rights reserved.

Advances in design and applications of polymer brush modified anisotropic particles

Current advancements in the creation of anisotropy in particles and their surface modification with polymer brushes have established a new class of hybrid materials termed polymer brush modified anisotropic particles (PBMAP). PBMAPs display unique property combinations, e.g., multi-functionality in multiple directions along with smart behavior, which is not easily achievable in traditional hybrid materials. Typically, anisotropic particles can be categorized based on three different factors, such as shape anisotropy (geometry driven), compositional anisotropy (functionality driven), and surface anisotropy (spatio-selective surface modification driven). In this review, we have particularly focused on the synthetic strategies to construct the various type of PBMAPs based on inorganic or organic core which may or may not be isotropic in nature, and their applications in various fields ranging from drug delivery to catalysis. In addition, superior performances and fascinating properties of PBMAPs over their isotropic analogues are also highlighted. A brief overview of their future developments and associated challenges have been discussed at the end.

Preparation of Magnetic-Luminescent Bifunctional Rapeseed Pod-Like Drug Delivery System for Sequential Release of Dual Drugs

Drug delivery systems (DDSs) limited to a single function or single-drug loading are struggling to meet the requirements of clinical medical applications. It is of great significance to fabricate DDSs with multiple functions such as magnetic targeting or fluorescent labeling, as well as with multiple-drug loading for enhancing drug efficacy and accelerating actions. In this study, inspired by the dual-chamber structure of rapeseed pods, biomimetic magnetic–luminescent bifunctional drug delivery carriers (DDCs) of 1.9 ± 0.3 μm diameter and 19.6 ± 4.4 μm length for dual drug release were fabricated via double-needle electrospraying. Morphological images showed that the rapeseed pod-like DDCs had a rod-like morphology and Janus dual-chamber structure. Magnetic nanoparticles and luminescent materials were elaborately designed to be dispersed in two different chambers to endow the DDCs with excellent magnetic and luminescent properties. Synchronously, the Janus structure of DDCs promoted the luminescent intensity by at least threefold compared to single-chamber DDCs. The results of the hemolysis experiment and cytotoxicity assay suggested the great blood and cell compatibilities of DDCs. Further inspired by the core–shell structure of rapeseeds containing oil wrapped in rapeseed pods, DDCs were fabricated to carry benzimidazole molecules and doxorubicin@chitosan nanoparticles in different chambers, realizing the sequential release of benzimidazole within 12 h and of doxorubicin from day 3 to day 18. These rapeseed pod-like DDSs with excellent magnetic and luminescent properties and sequential release of dual drugs have potential for biomedical applications such as targeted drug delivery, bioimaging, and sustained treatment of diseases.

Therapeutic potential of biogenic titanium dioxide nanoparticles: a review on mechanistic approaches

Biogenic titanium dioxide nanoparticles have unique size, shape and biochemical functional corona that embellish them with the potential to perform therapeutic actions such as anticancer, antimicrobial, antioxidant, larvicidal and photocatalysis by adopting various mechanistic or physiological approaches at the molecular level. We have provided a detailed overview of some of these physiological mechanisms, including disruption of the electron transport chain, DNA fragmentation, mitochondrial damage, induction of apoptosis, disorganization of the plasma membrane, inhibition of ATP synthase activity, suspension of cellular signaling pathways and inhibition of enzymatic activity. The biogenic synthesis of customized titanium dioxide nanoparticles has future application potentials to do breakthroughs in the pharmaceutical sectors to advance precision medicine and to better explain the disease prognosis and treatment strategies.

Modulating surface charge of dexamethasone non-spherical microcrystals for improved inner ear delivery

It is important to achieve precise surface charge manipulation of non-spherical drug microcrystals using facile and time-efficient methods for local drug delivery. In this study, silk-coated dexamethasone (DEX) non-spherical microcrystals were synthesized by precipitation technique followed by alternate deposition of poly(allylamine hydrochloride) (PAH) (or PAH-coated Fe₃O₄) and silk fibroin (SF) via layer-by-layer assembly. EDC and glutaraldehyde were employed to manipulate positive or negative charge of particles by simple chemical cross-linking reactions, respectively. In vivo assessment was carried out by intratympanic (IT) injection of DEX non-spherical microcrystals in guinea pigs. In vivo pharmacokinetic results demonstrate that negatively charged DEX microcrystals appeared to improve outcomes of inner ear delivery in comparison to positively-charged counterparts. This is partly because of the adhesive features of the SF. The present study may provide new ideas to construct surface charge-tunable drug delivery vehicles that are capable of crossing biological barriers, especially for inner ear delivery due to the simple and practical strategy.

Multidimensional Anisotropic Architectures on Polymeric Microparticles

Next generation life science technologies will require the integration of building blocks with tunable physical and chemical architectures at the microscale. A central issue is to govern the multidimensional anisotropic space that defines these microparticle attributes. However, this control is limited to one or few dimensions due to profound fabrication tradeoffs, a problem that is exacerbated by miniaturization. Here, a vast number of anisotropic dimensions are integrated combining SU-8 photolithography with (bio)chemical modifications via soft-lithography. Microparticles in a 15-D anisotropic space are demonstrated, covering branching, faceting, fiducial, topography, size, aspect ratio, stiffness, (bio)molecular and quantum dot printing, top/bottom surface coverage, and quasi-0D, 1D, 2D, and 3D surface patterning. The strategy permits controlled miniaturization on physical dimensions below 1 µm and molecular patterns below 1 µm² . By combining building blocks, anisotropic microparticles detect pH changes, form the basis for a DNA-assay recognition platform, and obtain an extraordinary volumetric barcoding density up to 1093 codes µm^-3 in a 3 × 12 × 0.5 µm³ volume.

Ultrasonic De-cross-linking of the pH- and Magneto-Responsive PHEMA/PMMA Microgel to Janus Nanoparticles: A New Synthesis Based on "Grafting from"/"Grafting to" Polymerization

Stimuli-responsive Janus nanoparticles (NPs) with a two-facial structure have been used widely in biomedical applications. Among several methods to prepare these NPs, surface-initiated atom transfer radical polymerization (SI-ATRP) has received much attention due to the precise deposition of polymers on the surface of the substrate. In this study, Janus nanoparticles with asymmetric surface chemistry were prepared through a masking method in three steps involving the covalent deposition of super paramagnetic iron oxide nanoparticles (SPIONs) on the cross-linked substrate based on methotrexate (MTX)-grafted poly(2-hydroxyethyl methacrylate) (CPM), surface functionalization of unreacted sites of immobilized SPIONs with 2-bromoisobutyryl bromide (BIBB) in order to prepare the macro-initiator (Br-Fe3O4-CPM), growing poly(methyl methacrylate) (PMMA) on the surface of the macro-initiator through the SI-ATRP method. Optical microscopy was utilized to monitor the successful modification of SPIONs. Poly(methyl methacrylate)-iron oxide-poly(2-hydroxyethyl methacrylate) (PMMA-Fe3O4-PHEMA) microgel was exposed to optimum ultrasound (US) waves to prepare the PMMA-Fe3O4-PHEMA nanoparticle. Transmission electron microscopy (TEM) was used to confirm the precise deposition of polymers and the Janus structure. The MTX release of US-synthesized Janus NPs was studied in PBS at pH values of 7.4 and 5.8. The release data were analyzed using the Excel add-in DDSolver program to evaluate the kinetics of the drug release process from the nanocarrier under different pH values.

Computational Design of Nanostructured Soft Interfaces: Focus on Shape Changes and Spreading of Cubic Nanogels

Understanding the dynamics of gels at soft interfaces is vital for a range of applications, from biocatalysis and drug delivery to enhanced oil recovery applications. Herein, we use dissipative particle dynamics simulations to focus on the shape changes of a cubic nanogel as it adsorbs from the aqueous phase onto the oil-water interface, effectively acting as a compatibilizer. Upon adsorption at the interface, the hydrogel spreads over the interface, adopting various shapes depending on its size and cross-link density. We characterize these shapes by the shape anisotropy and an effective extent of spreading. We highlight the differences between these characteristics for cubic and spherical nanogels and show that the choice of the cubic shape over the spherical one results in a wider range of topographies that could be dynamically prescribed onto the soft interface due to the gels' adsorption. We first validate our model parameters with respect to the known experimental values for polyacrylamide (PAAm) gels and focus on spreading and shape changes of PAAm nanogels onto the oil-water interfaces. We then probe the behavior of active gels by changing an affinity of the polymer matrix for the solvent, which can be caused by the application of an external stimulus (light, temperature, or change in the chemical composition of solvent). Furthermore, we focus on the interactions between multiple gels placed at the liquid-liquid interface. We show that controlling the shapes and the clustering of the gels at the interfaces via variations in solvent quality result in tailoring the dynamics and topography of soft nanostructured interfaces. Hence, our findings provide insights into the design of soft active nanostructured interfaces with topographies controlled externally via solvent quality.

Smart azobenzene-containing tubular polymersomes: fabrication and multiple morphological tuning

A fundamental challenge in nanomaterial science is to facilely fabricate nonspherical polymersomes. Here, several kinds of novel tubular polymersomes were fabricated via self-assembly of amphiphilic azobenzene-containing block copolymers. Besides, their shape could be tuned by multiple approaches including changes in the chemical structure, self-assembly conditions and external stimuli.

Directed arrangement of siRNA via polymerization-induced electrostatic self-assembly

Herein, polymerization-induced electrostatic self-assembly (PIESA) is conducted to mediate the self-assembly behavior of short interfering RNA (siRNA) for the first time. In PIESA, siRNA not only formed a simple electrostatic polyplex with positively charged polycations, but also facilitated directed self-assembly due to the molecular rigidity of siRNA, leading to appealing nanotubes.

Colloidal molecules and patchy particles: complementary concepts, synthesis and self-assembly

About the latest developments regarding self-assembly of textured colloids and its prospects.

Nonspherical chiral helical polymer particles with programmable morphology prepared by electrospraying

Chirality and chiral materials demonstrate ever-growing importance. As a new type of chiral material, chiral polymer particles hold huge potential in both scientific research and practical applications. Meanwhile, nonspherical polymer particles (NPPs) have witnessed substantial progress in recent years because of their unique structures and especially the properties distinguishable from the corresponding spherical particles. We hypothesize that combining chirality with NPPs will open up an unprecedented category of advanced materials. The present contribution reports the first protocol for preparing electrosprayed nonspherical chiral particles constructed from chiral helical polymers, using helical substituted polyacetylenes as the model. SEM images demonstrate the successful fabrication of nonspherical chiral particles with tunable morphologies (bowl-, golf- and apple-like particles). Circular dichroism (CD) measurement proves the remarkable optical activity of the particles, which is observed in the predominantly one-handed helical polymer chains. The present work establishes a novel, versatile, and powerful platform for preparing nonspherical chiral polymer particles with controllable morphology.

Impact of Surface Amphiphilicity on the Interfacial Behavior of Janus Particle Layers under Compression

Langmuir monolayers of silica/gold Janus particles with two different degrees of amphiphilicity have been examined to study the significance of particle surface amphiphilicity on the structure and mechanical properties of the interfacial layers. The response of the layers to the applied compression provides insight into the nature and strength of the interparticle interactions. Different collapse modes observed for the interfacial layers are linked to the amphiphilicity of Janus particles and their configuration at the interface. Molecular dynamics simulations on nanoparticles with similar contact angles provide insight on the arrangement of particles at the interface and support our conclusion that the interfacial configuration and collapse of anisotropic particles at the air/water interface are controlled by particle amphiphilicity.

Ellipsoidal Artificial Melanin Particles as Building Blocks for Biomimetic Structural Coloration

Inspired by the structural coloration of anisotropic materials in nature, we demonstrate the preparation of structural color materials by the assembly of anisotropic particles. Spherical artificial melanin particles consisting of a polystyrene core and polydopamine shell were stretched asymmetrically to form uniform-sized ellipsoidal particles with different aspect ratios. The aspect ratio and assembly method of the ellipsoidal particles influence the structural coloration, indicating that the particle shape is one of the important parameters for controlling the structural coloration. The discovery of a method to control the structural color using ellipsoidal particles is useful in basic research on structural colors in nature and provides flexibility in material design and extends the application range of structural color materials.

Shape-Preserved Transformation of Biological Cells into Synthetic Hydrogel Microparticles

The synthesis of materials that can mimic the mechanical, and ultimately functional, properties of biological cells can broadly impact the development of biomimetic materials, as well as engineered tissues and therapeutics. Yet, it is challenging to synthesize, for example, microparticles that share both the anisotropic shapes and the elastic properties of living cells. Here, a cell-directed route to replicate cellular structures into synthetic hydrogels such as polyethylene glycol (PEG) is described. First, the internal and external surfaces of chemically fixed cells are replicated in a conformal layer of silica using a sol-gel process. The template is subsequently removed to render shape-preserved, mesoporous silica replicas. Infiltration and cross-linking of PEG precursors and dissolution of the silica result in a soft hydrogel replica of the cellular template as demonstrated using erythrocytes, HeLa, and neuronal cultured cells. The elastic modulus can be tuned over an order of magnitude (≈10-100 kPa) though with a high degree of variability. Furthermore, synthesis without removing the biotemplate results in stimuli-responsive particles that swell/deswell in response to environmental cues. Overall, this work provides a foundation to develop soft particles with nearly limitless architectural complexity derived from dynamic biological templates.

Highly monodisperse zwitterion functionalized non-spherical polymer particles with tunable iridescence

A facile and simple synthetic route towards functionalized non-spherical polymer particles (NSP) with tunable morphologies and iridescence is presented. Monodisperse particles with unique zwitterionic functionality were synthesized via emulsifier-free emulsion polymerization in a single step process. The sulfobetaine comonomer was utilized to induce phase separation in the course of polymerization to achieve anisotropic NSP with controlled morphologies such as quasi-spherical with protruding structures like bulge, eye-ball, and snowman-like nanostructures. Both SEM and TEM analyses revealed anisotropic particles, and phase-separated protrusion morphology with a small increase in aspect ratio. By taking advantage of the monodisperse, colloidally stable NSPs, template free photonic crystal arrays were fabricated through a bottom-up approach. The particles readily self-assemble and exhibit a photonic bandgap with vivid structural colors that arise from ordered structures of different morphologies. Additionally, the salt-responsive photonic crystals also possess tunable color-changing characteristics.

A convenient method to fabricate functional photonic crystal arrays using self-assembled non-spherical particles that form tunable iridescent polymer opal by changing size and morphologies, thereby producing new responsive photonic material.

Preparation of Dimpled Polystyrene-Silica Colloidal Nanocomposite Particles

Preparation of polymer-silica colloidal nanocomposite particles with concave shape is challenging and seldom reported. This paper presents a novel and facile method to prepare dimpled polymer-silica nanocomposite particles with a thin silica shell through the judicious combination of alcoholic dispersion polymerization and the decane evaporation method. Submicrometer-sized polystyrene-silica (PS-SiO₂) nanocomposite particles were first prepared by dispersion polymerization of styrene in methanol in the presence of a methanolic silica sol, and then dimpled PS-SiO₂ particles were prepared by heating the near-spherical PS-SiO₂ particles dispersed in methanol/water media in the presence of decane and subsequent cooling. The effects of different heat treatment parameters, such as methanol/water ratio, stirring temperature, and stirring rate on the formation of the nanocomposite particles were investigated. Optimization of the heating conditions allowed ∼100% of dimpled particles to be achieved with one dimple on each particle. Moreover, calcination of the dimpled PS-SiO₂ nanocomposite particles led to the formation of hollow dimpled particles with a thin silica shell. This method is expected to enrich the shapes of polymer-silica nanocomposite particles.

Continuum percolation-based tortuosity and thermal conductivity of soft superball systems: shape dependence from octahedra via spheres to cubes

Understanding the effect of particle shape on the percolation threshold, tortuosity and thermal conductivity of soft (geometrical overlapping) particle systems is very crucial for the design and optimization of such materials, including colloids, polymers, and porous and fracture media. In this work, we first combine the excluded-volume theory with the Monte Carlo simulations to determine the percolation threshold for a family of soft superballs, the shape of which interpolates between octahedra and cubes via spheres. Then, we propose two continuum percolation-based models to respectively obtain the tortuosity and effective thermal conductivity of soft superball systems considering their percolation behavior, where monodisperse overlapping superballs are uniformly distributed in a homogeneous solid matrix. Specifically, both models cover the whole feasible range of superball volume fractions, including near the percolation threshold. Comparison with extensive experimental, numerical and theoretical results confirms that the present models are capable of precisely predicting the percolation threshold, tortuosity and thermal conductivity of such systems. Furthermore, we apply the proposed models to probe the influence of particle shape on these important parameters. Our results show that the decreasing percolation threshold and tortuosity as soft particles become more anisotropic is consistent with increasing conductivity. It suggests that the anisotropic-shaped inclusion phase is more conducting than the spherical inclusion phase. The present theoretical strategies and conclusions may provide sound guidance for the synthesis of colloidal and polymer superballs.