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It is necessary to install a damping energy absorbing structure for a certain type of naval gun test shell without projectile belt. Applicable high-performance dampers currently include viscoelastic colloidal damper and magnetorheological damper, and two kinds of special dampers for test shells have been designed and manufactured. In order to evaluate the mechanical properties of these two dampers under dynamic impact, a one-way coupling numerical method was proposed for simulation and analysis. Quasi-static experiments were used to verify the model based on magnetic field finite element (FE) and computational fluid dynamics (CFD). The model is also characterized by passive dynamic mesh and user-defined functions (UDF) based on C language. The results showed that the CFD models of both dampers were accurate. Though the colloidal damper is simpler in structure and lower in the cost, the MR damper has more significant damping and higher energy absorption ratio under impact. Compared with colloidal damper, MR damper is characterized by long working time, multiple vortices, chaotic streamlines and more uniform temperature distribution. When the power was continuously applied, the velocity of the impacted MR damper dropped to zero within 80ms, and the piston finally stopped at a stroke of 1.3mm. The colloidal damper reset within 8ms, and the reset velocity was 1.1m/s. In this study, the performance evaluation results of the two dampers were obtained, and the latest numerical methods for the mechanical performance analysis of colloidal dampers and MR dampers under dynamic impact were provided.

Pickering foams are foams stabilized by particles and are generally known to have good stability. A special subclass of particle-stabilized foams includes stimuli-responsive Pickering foams that can be formed or deconstructed by applying an external stimuli or changing the environmental conditions; such intelligent particles could find use in many practical applications. Here, we synthesized surfactant-free biocompatible poly[2(diethylamino)ethyl methacrylate] (PDEAEMA) hydrogel particles (HGPs) by emulsion polymerization. The morphology, structure, and surface charge of the HGPs were characterized by TEM, DLS, and the zeta potential, respectively. We have observed that the pH values of the aqueous solution have a strong influence on the formation of the Pickering foams in the presence of PDEAEMA HGPs. Namely, at pH values ≤4.0 no Pickering foams were produced, while at pH values >4.0 stable Pickering foams were formed. Moreover, the height, size and bubble size distribution of Pickering foams are strongly influenced by the pH values of aqueous solution and PDEAEMA HGPs concentration. The formed Pickering foams in basic aqueous solution can all be conveniently deconstructed by changing the pH values to below 4.0. Interestingly, the dried lamellas of the Pickering foams were constituted by either monolayers or multilayers of PDEAEMA HGPs as demonstrated by SEM.

Nanotheranostics is an emerging field that brings together nanoscale-engineered materials with biological systems providing a combination of therapeutic and diagnostic strategies. However, current theranostic nanoplatforms have serious limitations, mainly due to a mismatch between the physical properties of the selected nanomaterials and their functionalization ease, loading ability, or overall compatibility with bioactive molecules. Herein, a nanotheranostic system is proposed based on nanocompartment clusters composed of two different polymersomes linked together by DNA. Careful design and procedure optimization result in clusters segregating the therapeutic enzyme human Dopa decarboxylase (DDC) and fluorescent probes for the detection unit in distinct but colocalized nanocompartments. The diagnostic compartment provides a twofold function: trackability via dye loading as the imaging component and the ability to attach the cluster construct to the surface of cells. The therapeutic compartment, loaded with active DDC, triggers the cellular expression of a secreted reporter enzyme via production of dopamine and activation of dopaminergic receptors implicated in atherosclerosis. This two-compartment nanotheranostic platform is expected to provide the basis of a new treatment strategy for atherosclerosis, to expand versatility and diversify the types of utilizable active molecules, and thus by extension expand the breadth of attainable applications.

Functionalized nanoparticles (NPs) are critical to a wide-ranging of applications. The more versatile use of the NPs hinges on the capability to readily modify them to perform different functions. For example functionalized polymeric nanomaterials bearing ligands can be employed in metal ion extraction and recovery. However, obtaining ion-imprinted particles via ligand copolymerization can be difficult to scale-up. We therefore present an alternative method to obtain ligand-carrying polymeric nanoparticles (LC-NPs) for metal ion absorption. Branched polyethyleneimine (b-PEI) was used to modify the negatively charged surfactant-free polystyrene (PS) NPs obtained via surfactant-free emulsion polymerization by employing “surfmers”. The obtained PEI-PS NPs were further cross-linked with phthaldialdehyde to form cross-linked PEI-PS (CPEI-PS). Both PEI-PS and CPEI-PS were capable of absorbing chromium, nickel, cobalt and copper ions, as evident in the color change upon absorption. Furthermore, the ion absorption capacity of both types of particles was comparable, but with a greater selectivity toward copper ions. The selectivity towards copper ions of CPEI-PS increased with the degree of dialdehyde cross-linking. Repeated absorption-desorption cycles showed no loss in the absorption capacity of CPEI-PS as compared to the non-crosslinked PEI-PS. Finally, both were further reacted with two different aldehydes, which ascertained that the primary amine groups were present for further reaction with aldehydes and thereby enabling further functionalization of these particles.

A targeted drug delivery nanosystem for glioblastoma multiforme (GBM) based on polymersomes (Ps) made of poly(dimethylsiloxane)-poly(2-methyloxazoline) (PDMS-PMOXA) diblock copolymers was developed to evaluate their potential to actively target brain cancer cells and deliver anticancer drugs. Angiopep2 was conjugated to the surface of preformed Ps to target the low density lipoprotein receptor-related protein 1 that are overexpressed in blood brain barrier (BBB) and glioma cells. The conjugation efficiency yield for angiopep2 was estimated to be 24%. The angiopep2-functionalized Ps showed no cellular toxicity after 24h and enhanced the cellular uptake around 5 times more in U87MG glioblastoma cells compared to the non-targeted Ps. The encapsulation efficiency of doxorubicin (DOX) in Ps was 13% by co-solvent method, compared to a film rehydration method (4%). The release profiles of the DOX from Ps showed a release of 42% at pH 5.5 and 40% at pH 7.4 after 24h, indicating that Ps can efficiently retain the DOX with a slow release rate. Furthermore, the in vitro antiproliferative activity of DOX-loaded Ps-Angiopep2 showed enhanced toxicity to U87MG glioblastoma cells, compared to non-targeted Ps. Overall, our in vitro results suggested that angiopep2-conjugated Ps can be used as nanocarriers for efficient targeted DOX delivery to glioblastoma cells.

The ability of amphiphilic Janus nanoparticles (JNPs) to partition at the oil–water and air–water interfaces can be especially attractive for a plethora of new applications. Unlike molecular surfactants, the JNPs could act as “bulk-to-surface” carriers of different small molecules/actives or bulklike properties—magnetic, optic, or electric—without a dramatic effect on their ability to partition at interfaces. Here we report surfactant-free JNPs with pH-triggered switchable amphiphilicity that could be used in such interfacial applications. The polarity balance of the JNPs can be tuned by the pH such that the amphiphilicity of JNPs is switched on or off at low (pH 7.0) pH values, respectively. When the amphiphilicity of JNPs is switched off, the interfacial activity of JNPs is comparable to that of homogeneous nanoparticles (HNPs), and when switched on, the interfacial activity is enhanced, proving that the amphiphilicity of JNPs plays a role in enhancing the interfacial activity even at...

Elucidating the mechanisms responsible for spontaneous adsorption of nanoparticles (NPs) at interfaces is important for their application as emulsifiers, bubble stabilizers, or foaming agents. In order to investigate the key factors that control the spontaneous adsorption of NPs at liquid-liquid interfaces, we synthesized seven different types of NPs from pH-responsive polymers poly(2-(diethylamino)ethyl methacrylate) (PDEAEMA) and poly(2-dimethylamino)ethyl methacrylate) (PDMAEMA) via surfactant-free emulsion polymerization or via "grafting from" polystyrene (PS) NPs. The dynamic interfacial tension (IFT) measurements at the toluene-water (Tol-H2O) interface reveal that when PDEAEMA and PDMAEMA are grafted from the surface of PS NPs the solubility of the grafted pH-responsive polymers in toluene is the key factor determining the NPs' interfacial adsorption. Under acidic conditions (pH < 6.0), PDEAEMA and PDMAEMA are protonated and show no solubility in toluene, and as a result, the grafted NPs do not adsorb at the Tol-H2O interface. Oppositely, under basic conditions (pH > 7.0), PDMAEMA dissolves in toluene and therefore the PDMAEMA-grafted NPs can adsorb at the Tol-H2O interface. Interestingly, when NPs are constituted of PDEAEMA, they can adsorb spontaneously at the Tol-H2O interface under acidic conditions (pH < 6.0) but not under basic conditions (pH > 7.0). In this case, the key factor determining the NPs' spontaneous adsorption at the Tol-H2O interface is the degree of softness of the NPs rather than the solubility of PDEAEMA in toluene. Furthermore, we found that the adsorption of NPs constituted of PDEAEMA- (pH 2.0-6.0) and PDMAEMA-grafted PS NPs (pH 7.0-10.0) at the Tol-H2O interface is a combination of diffusion-controlled and energy-barrier-controlled. The opposite trends observed for the interfacial attachment ΔE and activation energies Ea for the "constituted of" and "grafted from" NPs with pH suggest an opposite mechanisms of adsorption at the Tol-H2O interface. Finally, the synthesized NPs prove to be effective emulsifiers, where the phase of the Pickering emulsions can be changed dynamically by pH adjustment.

Polymersomes that encapsulate a hydrophilic polymer are prepared by conducting biocatalytic atom transfer radical polymerization (ATRP) in these hollow nanostructures. To this end, ATRPase horseradish peroxidase (HRP) is encapsulated into vesicles self-assembled from poly(dimethylsiloxane)-block-poly(2-methyl-2-oxazoline) (PDMS-b-PMOXA) diblock copolymers. The vesicles are turned into nanoreactors by UV-induced permeabilization with a hydroxyalkyl phenone and used to polymerize poly(ethylene glycol) methyl ether acrylate (PEGA) by enzyme-catalyzed ATRP. As the membrane of the polymersomes is only permeable for the reagents of ATRP but not for macromolecules, the polymerization occurs inside of the vesicles and fills the polymersomes with poly(PEGA), as evidenced by (1) H NMR. Dynamic and static light scattering show that the vesicles transform from hollow spheres to filled spheres during polymerization. Transmission electron microscopy (TEM) and cryo-TEM imaging reveal that the polymersomes are stable under the reaction conditions. The polymer-filled nanoreactors mimic the membrane and cytosol of cells and can be useful tools to study enzymatic behavior in crowded macromolecular environments.

Determining the interfacial energy of nanoparticles is very challenging via traditional methods that first require measuring the contact angle of several liquids of a sessile drop on pellets or capillary rise in powder beds. In this work, we propose an alternative way to model the interfacial energy of nanoparticles directly from emulsion phase inversion data in Pickering emulsions. This could establish itself as a universal and facile way to determine the polarity of nanoparticles relative to a series of standard particles without the need to measure contact angles. Pickering emulsions of several oils in water were generated with a series of snowman-like Janus nanoparticles (JNPs), whose polarity gradually increased with the size of the more polar lobe. Depending on the oil to water ratio and the JNPs lobe size, oil-in-water (o/w) or water-in-oil (w/o) Pickering emulsions were obtained and the affinity of the JNPs to either water or oil can be inferred from the evolution of the emulsion phase inversion curves with these parameters. We further demonstrate that by adopting a simple model for the work of adhesion of JNPs with the water and oil phases, one can quantitatively calculate the relative interfacial energy change of the JNPs with the liquid. In addition, a knowledge of the interfacial energy of nanoparticles is useful for employing these in suspension polymerization to create surface nanostructured materials. The o/w and w/o Pickering emulsions obtained from monomers, such as styrene, could be polymerized, resulting in colloidosomes or hollow-like materials. The hollow materials exhibited a rather high volume storage capacity for the aqueous phase for extended periods of time, which could be released upon microwaving, making them ideal for use in long-term storage applications of various water-soluble actives.

Subcellular compartmentalization of cells, a defining characteristic of eukaryotes, is fundamental for the fine tuning of internal processes and the responding to external stimuli. Reproducing and controlling such compartmentalized hierarchical organization, responsiveness, and communication is important toward understanding biological systems and applying them to smart materials. Herein, a cellular signal transduction strategy (triggered release from subcompartments) is leveraged to develop responsive, purely artificial, polymeric multicompartment assemblies. Incorporation of responsive nanoparticles-loaded with enzymatic substrate or ion channels-as subcompartments inside micrometer-sized polymeric vesicles (polymersomes) allowed to conduct bioinspired signaling cascades. Response of these subcompartments to an externally added stimulus is achieved and studied by using confocal laser scanning microscopy (CLSM) coupled with in situ fluorescence correlation spectroscopy (FCS). Signal triggered activity of an enzymatic reaction is demonstrated in multicompartments through recombination of compartmentalized substrate and enzyme. In parallel, a two-step signaling cascade is achieved by triggering the recruitment of ion channels from inner subcompartments to the vesicles' membrane, inducing ion permeability, mimicking endosome-mediated insertion of internally stored channels. This design shows remarkable versatility, robustness, and controllability, demonstrating that multicompartment polymer-based assemblies offer an ideal scaffold for the development of complex cell-inspired responsive systems for applications in biosensing, catalysis, and medicine.

Medical applications of anticancer and antimalarial drugs often suffer from low aqueous solubility, high systemic toxicity, and metabolic instability. Smart nanocarrier-based drug delivery systems provide means of solving these problems at once. Herein, we present such a smart nanoparticle platform based on self-assembled, reduction-responsive amphiphilic graft copolymers, which were successfully synthesized through thiol-disulfide exchange reaction between thiolated hydrophilic block and pyridyl disulfide functionalized hydrophobic block. These amphiphilic graft copolymers self-assembled into nanoparticles with mean diameters of about 30-50 nm and readily incorporated hydrophobic guest molecules. Fluorescence correlation spectroscopy (FCS) was used to study nanoparticle stability and triggered release of a model compound in detail. Long-term colloidal stability and model compound retention within the nanoparticles was found when analyzed in cell media at body temperature. In contrast, rapid, complete reduction-triggered disassembly and model compound release was achieved within a physiological reducing environment. The synthesized copolymers revealed no intrinsic cellular toxicity up to 1 mg mL(-1). Drug-loaded reduction-sensitive nanoparticles delivered a hydrophobic model anticancer drug (doxorubicin, DOX) to cancer cells (HeLa cells) and an experimental, metabolically unstable antimalarial drug (the serine hydroxymethyltransferase (SHMT) inhibitor (±)-1) to Plasmodium falciparum-infected red blood cells (iRBCs), with higher efficacy compared to similar, non-sensitive drug-loaded nanoparticles. These responsive copolymer-based nanoparticles represent a promising candidate as smart nanocarrier platform for various drugs to be applied to different diseases, due to the biocompatibility and biodegradability of the hydrophobic block, and the protein-repellent hydrophilic block.

The ability to finely tune the amphiphilic balance of Janus nanoparticles (JNPs) could represent a step forward toward creating the next generation of solid-state amphiphiles with significant potential for applications. The inherent amphiphilicity of JNPs stemming from an intrinsic polarity contrast between two surface regions is well-acknowledged, but remained difficult to demonstrate experimentally in the absence of surfactants and stabilizers. We have designed two homologous series of surfactant-free polymeric JNPs starting from polystyrene (PS) seed nanoparticles (NPs) on which we grew Janus lobes of different sizes via seed polymerization and phase separation of the 3-(triethoxysilyl)propyl-methacrylate (3-TSPM) monomer. The two series differ only by the radical initiator used in the seed polymerization: polar ionic ammonium persulfate (APS) vs nonpolar oil-soluble 2,2'-azobis(2-methylpropionitrile) (AIBN). To compare the two series, we employed them in the emulsification of water with heptane or molten paraffin wax. A polarity reversal of the JNPs within AIBN-JNP series could be observed from the catastrophic and transitional emulsion phase inversions and occurred when the more polar lobe was larger than the nonpolar seed PS lobe. Furthermore, the AIBN-JNPs appeared to be amphiphilic and adopt preferred orientation within the monolayer at the oil/water interface. We therefore demonstrated that in the absence of surfactants the amphiphilicity of the JNPs depends not only on the relative size of the lobes, but also on the surface polarity contrast, which can be tuned by changing the nature of radical initiator.

Self-organization of nanocomponents was mainly focused on solid nanoparticles, quantum dots, or liposomes to generate complex architectures with specific properties, but intrinsically limited or not developed enough, to mimic sophisticated structures with biological functions in cells. Here, we present a biomimetic strategy to self-organize synthetic nanocompartments (polymersomes) into clusters with controlled properties and topology by exploiting DNA hybridization to interconnect polymersomes. Molecular and external factors affecting the self-organization served to design clusters mimicking the connection of natural organelles: fine-tune of the distance between tethered polymersomes, different topologies, no fusion of clustered polymersomes, and no aggregation. Unexpected, extended DNA bridges that result from migration of the DNA strands inside the thick polymer membrane (about 12 nm) represent a key stability and control factor, not yet exploited for other synthetic nano-object networks. The replacement of the empty polymersomes with artificial organelles, already reported for single polymersome architecture, will provide an excellent platform for the development of artificial systems mimicking natural organelles or cells and represents a fundamental step in the engineering of molecular factories.

Planar solid-supported membranes based on amphiphilic block copolymers represent promising systems for the artificial creation of structural surfaces. Here we introduce a method for engineering functional planar solid-supported membranes through insertion of active biomolecules. We show that membranes based on poly(dimethylsiloxane)-block-poly(2-methyl-2-oxazoline) (PDMS-b-PMOXA) amphiphilic diblock copolymers, which mimic natural membranes, are suitable for hosting biomolecules. Our strategy allows preparation of large-area, well-ordered polymer bilayers via Langmuir-Blodgett and Langmuir-Schaefer transfers, and insertion of biomolecules by using Bio-Beads. We demonstrate that a model membrane protein, the potassium channel from the bacterium Mesorhizobium loti, remains functional after insertion into the planar solid-supported polymer membrane. This approach can be easily extended to generate a platform of functional solid-supported membranes by insertion of different hydrophobic biomolecules, and employing different types of solid substrates for desired applications. (C) 2014 Elsevier Ltd. All rights reserved.