Polymer Shell Research Articles

Polymeric materials for ultrasound imaging and therapy.

Ultrasound (US) is routinely used for diagnostic imaging and increasingly employed for therapeutic applications. Materials that act as cavitation nuclei can improve the resolution of US imaging, and facilitate therapeutic US procedures by promoting local drug delivery or allowing temporary biological barrier opening at moderate acoustic powers. Polymeric materials offer a high degree of control over physicochemical features concerning responsiveness to US, e.g. via tuning chain composition, length and rigidity. This level of control cannot be achieved by materials made of lipids or proteins. In this perspective, we present key engineered polymeric materials that respond to US, including microbubbles, gas-stabilizing nanocups, microcapsules and gas-releasing nanoparticles, and discuss their formulation aspects as well as their principles of US responsiveness. Focusing on microbubbles as the most common US-responsive polymeric materials, we further evaluate the available chemical toolbox to engineer polymer shell properties and enhance their performance in US imaging and US-mediated drug delivery. Additionally, we summarize emerging applications of polymeric microbubbles in molecular imaging, sonopermeation, and gas and drug delivery, based on refinement of MB shell properties. Altogether, this manuscript provides new perspectives on US-responsive polymeric designs, envisaging their current and future applications in US imaging and therapy.

Fluorescent core-shell magnetic nanoparticles by type II photoinitiated polymerisation.

We report a fluorescent monomer-free method for the synthesis of fluorescent and stable magnetic nanocomposites using a benzophenone/rhodamine B bimolecular photoinitiator system. The method allows the synthesis of a fluorescent polymer shell layer around magnetic nanoparticles in one step by UV irradiation at ambient temperature.

Construction of consumer-friendly essential oil microcapsules with viscous cores to provide extra long-lasting release

Essential oil microcapsules with viscous cores were formulated by encapsulating oil droplets with intermediate non-crosslinked polymer shells and crosslinked polymer outer shells, followed by dissolution of the intermediate shells with essential oil to form viscous cores. The study found that when the core/shell ratios of the intermediate shell = 3:2, the rotational speed = 500 rpm, the concentration of the protective colloid = 1.0 wt%, the concentration of the crosslinking agent = 20 wt% and the core/shell ratio of the outer shell = 10:1 by using three times' addition method, caprylic/capric triglyceride (GTCC) microcapsules with viscous cores were obtained. The release profile, mechanical strength and adsorption performance of GTCC microcapsules were evaluated in comparison with melamine-formaldehyde microcapsules. It was found that the viscous cores microcapsules had better heat resistance, extreme long-lasting release property, viscoelasticity and been more adhesive to cotton fabrics, which were more consumer-friendly compared with that of melamine-formaldehyde microcapsules. • Construction of essential oil (GTCC) microcapsule with the viscous core structure. • Polystyrene (PS) was used as wall material, which is safe and consumer-friendly. • MF (Melamine-formaldehyde)-GTCC and PS-GTCC microcapsules were compared. • The release, viscoelasticity and adsorption property of microcapsule was enhanced.

Permanent irreversible structural color based on core-shell chemically bonded SiO2@P(St-BA) particles.

Novel core-shell chemically bonded SiO2@P(St-BA) particles were designed and self-assembled to prepare photonic crystals. Due to the irreversible collapse of polymer shells during hot-pressing, SiO2@P(St-BA) particles could provide new ideas for high-stability and bright red-shifted structural color patterns.

Magnetic delivery and ultrasound-responsive release of chelating microcapsules for selective removal of urolithiasis.

A novel urolithiasis treatment in which a chelating solution encapsulated in poly(lactic-co-glycolic acid); PLGA-based microcapsules was delivered magnetically to specific urolithiasis sites and then subjected to ultrasound (US) to release the chelating solution and dissolve the stones. Using a double-droplet microfluidics method, a hexametaphosphate (HMP) chelating solution was encapsulated in an Fe3O4 nanoparticle (Fe3O4 NP)-loaded PLGA polymer shell with a thickness of <15 μm, forming homogenous microcapsules of 319 ± 14 μm in size. The obtained microcapsules (HMP/Fe3O4@PLGA) exhibited efficient magnetic mobility and US-responsive solution release. Moreover, in a Ψ-shaped flow chip, selective delivery of HMP from the microcapsules was achieved with high magnetic delivery efficiency (>90%), and an effective removal efficacy (>95%, 7 repeat cycles) of artificial calcium oxalate (5 mm in size) via a chelating effect. Eventually, the potential removal of urolithiasis in the body was verified using a PDMS-based kidney urinary flow-imitating chip with a human kidney stone (CaOx 100%, 5-7 mm in size) located in the minor calyx under an artificial urine counter flow (0.5 mL min-1). In the end, more than 50% of the stone, even in surgically tricky regions, was removed by 10 repeated treatments. Therefore, the selective approach of stone-dissolution capsules will help to develop alternative urolithiasis treatments to conventional surgical and systemic dissolution approaches.

Ag@imidazolium functionalized polymeric yolk–shell hybrid nanoparticles for economical CO2 photoreduction

Yolk–shell nanoparticles (AIDNPs) with Ag nanoparticle core and imidazolium functionalized polymeric shell were prepared for CO2 photo-catalytic reduction in a competitive and economical manner in absence of photo-sensitizer or sacrifice reducing agent.

Capsules with responsive polymeric shells for applications beyond drug delivery

This minireview addresses responsive polymer capsules and their applications beyond drug delivery, focusing on structure–property relationships.

Heat storage and increasing the rate of heat transfer in polymer electrolyte membrane fuel cell by adding nano-encapsulated phase change material to water in the cooling process

Polymer electrolyte membrane fuel cell (PEMFC) is a promising technology in the field of renewable energy production, especially in electric transportation systems. High heat produced and the temperature sensitivity of the expensive membrane have always reduced the lifespan and efficiency of PEMFCs and prevented their commercialization. Choosing an optimal cooling method is always one of the best solutions studied by researchers. Phase change cooling with nePCM particles is one of the newest microchannel cooling methods, which in addition to good heat transfer and uniform cooling, capability waste heat recovery (WHR) by heat storage. Nano-encapsulated of phase change material (nePCM) is a new type of PCMs that can absorb high heat without noticeable temperature change due to high latent heat during the phase change process while improving heat transfer. These particles consist of a phase change material in the core and a polymer shell, which, significantly improves its heat transfer properties when added to the base fluid. Based on computational fluid dynamics (CFD) simulation, the performance of water-nePCM suspension with an n-nonadecane core and polyurethane shell as a new cooling nanofluid in the microchannel of a PEMFC was evaluated for the first time. The governing equations are solved numerically using the finite volume method (FVM), PIMPLE algorithm, and C++ code development, by OpenFoam software. After examining the effect of different heat transfer parameters, the results show that using 4 % of nePCM particles increases the Nusselt number and heat storing (ηNEPCM %), by 20 % and 18 % respectively. Also, lower Reynolds numbers cause more heat storage in nePCM particles. As a result, this has led to more uniform cooling of the PEMFC plates and the thermal stability of the system.

Ways to ensure the attenuation coefficient within the limits of normal values of single shielded twisted pair cables for industrial Ethernet networks

In recent years, the concept of Industry 4.0 and IioT has seen an intensive transition of industrial networks to wired data transmission based on the Ethernet family of technologies. The given chronology of the development of international standards of industrial Ethernet and corresponding cables based on twisted pairs proves the perspective of using a single twisted pair with the possibility of transmitting a power signal, which significantly reduces the number, weight and cost of cables in the network. According to international standards on cables for industrial Ethernet, shielded solutions based on a single shielded twisted pair must ensure the transmission of digital signals in the frequency range of up to 20 MHz over a distance of up to 1 kilometre. The need to use a shielded twisted pair is due to operating conditions under the influence of strong electromagnetic interference. An analytical review of scientific publications shows that shielded cable designs have increased values of electrical capacity. On the basis of numerical modelling of the electric field in the twisted pair, the value of the electrical capacity is determined depending on the design of the screen. It is shown that the shielded twisted pair has significantly larger (by 80 %), electrical capacity values compared to the unshielded one, provided the insulation, screen and protective polymer shell are of the same thickness. The effectiveness of the use of a two-layer aluminium polymer screen is substantiated. It has been proven that varying the thickness and dielectric permeability of the screen film material allows optimizing the cable design to ensure lower values of the working capacity compared to an unshielded pair. On the basis of numerical calculations, it is shown that when the two-layer screen is placed with the film outwards, the working capacity increases significantly and does not differ from the capacity shielded with a solid metal screen. The validity and adequacy of the performed numerical calculations of the electrical capacity of twisted pairs is confirmed by experimental results of measurements of the attenuation coefficient in the frequency range up to 20 MHz of unshielded and shielded twisted pair with a two-layer laminated screen.

Cadmium Sulfide—Reinforced Double-Shell Microencapsulated Phase Change Materials for Advanced Thermal Energy Storage

Phase change materials (PCMs) are widely used to improve energy utilization efficiency due to their high energy storage capacity. In this study, double-shell microencapsulated PCMs were constructed to resolve the liquid leakage issue and low thermal conductivity of organic PCMs, which also possess high thermal stability and multifunctionality. We used assembly to construct an inorganic-organic double shell for microencapsulate PCMs, which possessed the unprecedented synergetic properties of a cadmium sulfide (CdS) shell and melamine-formaldehyde polymeric shell. The scanning electron microscopy (SEM) and transmission electron microscopy (TEM) images confirmed the well-designed double-shell structure of the microcapsules, and the CdS was successfully assembled as the second shell on the surface of the polymer shell. The differential scanning calorimeter (DSC) showed that the double-shell microcapsules had a high enthalpy of 114.58 J/g, which indicated almost no changes after experiencing 100 thermal cycles, indicating good thermal reliability. The microcapsules also showed good shape stability and antileakage performance, which displayed no shape change and leakage after heating at 60 °C for 30 min. In addition, the photothermal conversion efficiency of the double-shell microcapsules reached 91.3%. Thus, this study may promote the development of microencapsulated PCMs with multifunctionality, offering considerable application prospects in intelligent temperature management for smart textiles and wearable electronic devices in combination with their solar thermal energy conversion and storage performance.

Effect of hydrophobic silica aerogels in-situ on encapsulation the stability of CsPbBr3 quantum dots for white light-emitting diodes

Despite the outstanding optical features of lead halide perovskite quantum dots (QDs), they are troubled by stability issues that hinder their prospects in practical applications. Herein, the CsPbBr3 QDs generated here were grown in situ in hydrophobic silica aerogels (SiO2 AGs). More importantly, the photoinitiated cross-linking reaction of the capping ligands, conjugated linoleic acids (CLA), forms hydrophobic polymer shells from CsPbBr3 QDs@SiO2 AGs-poly. And these polymer shells further improve the water stability of QDs. The composite retains 83 % photoluminescence (PL) intensity after being dispersed in water for five days. And SiO2 AGs also act as confined templates owing to their unique porous structure to avoid aggregation and regrowth of QDs in the polymerization process of CLA. With the combined effects of SiO2 AGs and polymer shells, the composite shows remarkable optical performance with a high absolute quantum yield (QY) (89.08 %). And this green-emitting composite was applied as a luminescent material in a white light-emitting diode (WLED), which exhibited excellent luminescence with the color coordinates of (0.3344, 0.3253) and light efficiency of 28.8 lm/W at 20 mA, and light stability under large current.

Scaling Up Magnetic Nanobead Synthesis with Improved Stability for Biomedical Applications.

The growing interest in multifunctional nano-objects based on polymers and magnetic nanoparticles for biomedical applications motivated us to develop a scale-up protocol to increase the yield of polymeric magnetic nanobeads while aiming at keeping the structural features at optimal conditions. The protocol was applied to two different types of magnetic ferrite nanoparticles: the Mn-ferrite selected for their properties as contrast agents in magnetic resonance imaging and iron oxide nanostar shaped nanoparticles chosen for their heat performance in magnetic hyperthermia. At the same time, some experiments on surface functionalization of nanobeads with amino modified polyethyelene glycol (PEG) molecules have provided further insight into the formation mechanism of magnetic nanobeads and the need to cross-link the polymer shell to improve the stability of the beads, making them more suitable for further manipulation and use. The present work summarizes the most important parameters required to be controlled for the upscaling of nanobead synthesis in a bench protocol and proposes an alternative cross-linking strategy based on prefunctionalization of the polymer prior to the nanobead formation as a key parameter to improve the nanobead structural stability in solutions at different pHs and during surface functionalization.

Co-Delivery System of Curcumin and Colchicine Using Functionalized Mesoporous Silica Nanoparticles Promotes Anticancer and Apoptosis Effects.

Many natural agents have a high anticancer potential, and their combination may be advantageous for improved anticancer effects. Such agents, however, often are not water soluble and do not efficiently target cancer cells, and the kinetics of their action is poorly controlled. One way to overcome these barriers is to combine natural agents with nanoparticles. Our aim in the current study was to fabricate an anticancer nanoformulation for co-delivery of two natural agents, curcumin (CR) and colchicine (CL), with a core-shell structure. Using cancer cell lines, we compared the anticancer efficacy between the combination and a nanoformulation with CL alone. For the single-drug nanoformulation, we used phosphonate groups to functionalize mesoporous silica nanoparticles (MSNs) and loaded the MSNs with CL. Additional loading of this nanoformulation with CR achieved the co-delivery format. To create the structure with a core shell, we selected a chitosan-cellulose mixture conjugated with targeting ligands of folic acid for the coating. For evaluating anticancer and apoptosis effects, we assessed changes in important genes and proteins in apoptosis (p53, caspase-3, Bax, Bcl-2) in several cell lines (MCF-7, breast adenocarcinoma; HCT-116, colon carcinoma; HOS, human osteosarcoma; and A-549, non-small cell lung cancer). Nanoformulations were successfully synthesized and contained 10.9 wt.% for the CL single-delivery version and 18.1 wt.% for the CL+CR co-delivery nanoformulation. Anticancer effects depended on treatment, cell line, and concentration. Co-delivery nanoformulations exerted anticancer effects that were significantly superior to those of single delivery or free CL or CR. Anticancer effects by cell line were in the order of HCT-116 &gt; A549 &gt; HOS &gt; MCF-7. The lowest IC50 value was obtained for the nanoformulation consisting of CL and CR coated with a polymeric shell conjugated with FA (equivalent to 4.1 ± 0.05 µg/mL). With dual delivery compared with the free agents, we detected strongly increased p53, caspase-3, and Bax expression, but inhibition of Bcl-2, suggesting promotion of apoptosis. Our findings, although preliminary, indicate that the proposed dual delivery nanoformulation consisting of nanocore: MSNs loaded with CL and CR and coated with a shell of chitosan-cellulose conjugated folic acid exerted strong anticancer and apoptotic effects with potent antitumor activity against HCT-116 colon cells. The effect bested CL alone. Evaluating and confirming the efficacy of co-delivery nanoformulations will require in vivo studies.

Temperature-Triggered Release of Chromium Chloride from Nanocapsules for Controlled Burst Release and Gelation of Hydrolyzed Polyacrylamide to Plug High-Permeability Channels

Summary Chromium(III) (Cr3+)-hydrolyzed polyacrylamide (HPAM) gels have been applied extensively as blocking agents for sweep efficiency improvement. Previous studies focused on delaying the gelation time and ignored the diffusion of the crosslinkers during the transportation process. The gelation time of Cr3+-HPAM was too long to be controlled. This study systematically describes a novel approach of using thermoresponsive nanocapsules to precisely control the release of Cr3+. The nanocapsules are successfully prepared by a controlled nanoprecipitation of hydrophobic polymers [poly (methyl methacrylate)] (PMMA) and Pluronic® P-123 onto stable aqueous Cr3+ solution nanodroplets. The stable aqueous nanodroplets are obtained by double inverse miniemulsions with oil-soluble surfactant Span® 80. The nanoprecipitation occurs when heating the mixture at 50℃, which leads to the evaporation of solvent and precipitation of the PMMA into the interface of the aqueous droplets to form the shells. Pluronic P-123 is introduced to stabilize the double miniemulsion and enhance the precipitation efficiency of the shell polymer during the fabrication process. The fabricated nanocapsules show a size range from 211.9 to 297.2 nm depending on the feed contents of the Cr3+. The thermoresponsive function of Pluronic P-123 is studied and applied as a temperature-trigger on the shell. Gelation results show that the thermoresponsivity of Pluronic P-123 dominates the release rate rather than the diffusion rate through PMMA, which could be used to shorten the gelation interval time.

In-Situ Spectro-Electrochemistry of Conductive Polymers Using Plasmonics to Reveal Doping Mechanisms.

Conducting polymers are a key component for developing wearable organic electronics, but tracking their redox processes at the nanoscale to understand their doping mechanism remains challenging. Here we present an in-situ spectro-electrochemical technique to observe redox dynamics of conductive polymers in an extremely localized volume (<100 nm3). Plasmonic nanoparticles encapsulated by thin shells of different conductive polymers provide actively tuned scattering color through switching their refractive index. Surface-enhanced Raman scattering in combination with cyclic voltammetry enables detailed studies of the redox/doping process. Our data intriguingly show that the doping mechanism varies with polymer conductivity: a disproportionation mechanism dominates in more conductive polymers, while sequential electron transfer prevails in less conductive polymers.

Solvent-sensitive nanoparticle-enhanced PCR assay for the detection of enterotoxigenic Escherichia coli

Stimulus-responsive nanoparticles are among the most utilized nanoscale materials in biomedical applications. As these nanoparticles exhibit a manipulable response to a particular stimulus, such as pH, heat, and organic solvent, they are potential signalling units in diagnostic assays. This study aims to enhance the limit of detection and reduce the turnaround time of magnetic nanoparticle polymerase chain reaction (PCR) enzyme-linked gene assay (MELGA), an advanced PCR-based technique termed the solvent-sensitive nanoparticle (SSNP)-enhanced PCR assay. This technique was proposed to detect pathogenic enterotoxigenic Escherichia coli (ETEC) through applying stimulus-responsive nanoparticles. The SSNPs were elaborated with three main components, including mesoporous silica nanoparticles as a structural unit, organic dye (Nile red) as a payload, and the corresponding organic solvent-sensitive polymer shell as “gatekeeper” (poly(maleic anhydride-alt-methyl vinyl ether, PMAMVE). A suitable organic solvent capable of inducing polymer swelling and dye dissolution was investigated by considering a solubility parameter. Using ethanol, the encapsulated Nile red can diffuse out of the SSNPs faster than other solvents and reach a constant concentration within 15 min. For the PCR inhibition study, various SSNPs concentrations (10–30 μg/reaction) were mixed with the ETEC gene and PCR reagent. The results showed that the particles in this concentration range did not inhibit PCR. By comparing the efficacy of conventional PCR, MELGA, and SSNP-enhanced PCR assay, the proposed technique showed a better detection limit than that of PCR, whereas that of MELGA was the lowest. Moreover, compared to MELGA or conventional PCR, this technique provided remarkably faster results in the postamplification process.

Effect of Polymer Shell Structure of a Gamma-ray Shielding Film Prepared Using Composite Material on Shielding Performance

Medical protective clothing should be flexible to ensure free movement of healthcare personnel. This study aimed to investigate the effects of a polymer’s physical properties on the particle composition of a shielding material, constituent component miscibility, and shielding performance. To ensure flexibility by reducing the thickness of the shielding garment, polymer-based composite materials are mainly used as shielding materials. The shielding performance varies depending on whether the polymer used is in an emulsion or powder state. In this study, we found that a shielding film manufactured through an injection process after mixing a polymer in a powder form with tungsten powder exhibited 0.95%–2.5% higher shielding performance than that manufactured using the calendering process with an emulsion polymer. The shell structure formed when using the powder polymer maintains the spacing between the particles owing to the double coating of the tungsten particles and improves their dispersion. Additionally, the primary issue when combining an emulsion polymer and shielding material, that is the aggregation between the shielding material particles and between the polymer particles, could be alleviated, resulting in improved shielding performance. We concluded that the polymer-powder mixing method contributes to the reproducibility of the process technology when manufacturing shielding films.

Multifunctional Waterborne Polyurethane Microreactor-Based Approach to Fluorocarbon Composite Latex Coatings with Double Self-Healing and Excellent Synergistic Performances.

In this article, chlorotrifluoroethylene (CTFE)-based fluorocarbon composite latexes and their coatings are successfully fabricated by an environmentally friendly preparation method based on a new multifunctional waterborne polyurethane (MFWPU) dispersion. It is worth noting that the MFWPU acts as the sole system stabilizer as well as microreactor and simultaneously endows the composite coating with excellent double self-healing performance and adhesion. Moreover, the introduction of a dynamic disulfide bond in the polyurethane dispersion entrusts the coating with excellent scratch self-healing performance. Simultaneously, carbon-carbon double bonds in the polyurethane dispersion increase the compatibility between the core polymer and shell polymer. The fluorine-containing chain segments can be distributed in the coating evenly during the self-assembly film-forming process of composite particles so that the original element composition of the worn coating surface can restore the original element composition after heating, and the coating presents a regeneration ability, which further and verifies the usefulness of the double self-healing model of the coating. Afterward, efficient recovery and durability, which are two contradictory properties of scratch self-healing polymers, are optimized to obtain a composite coating with excellent comprehensive performance. The research results regarding the composite system may provide a valuable reference for the structural design and application of waterborne fluorocarbon functional coatings in the future.

Development of iron-vitamin multilayer encapsulates using 3 fluid nozzle spray drying

Considering the growing concern of iron and folic acid deficiency, encapsulation of these nutrients and fortification into foods is emerging as an effective counter-strategy. The present work focuses on a scalable approach for the production of iron, ascorbic acid, and folic acid core–shell encapsulates using novel 3-fluid nozzle (3FN) spray drying with whey protein as core and either pectin or hydroxypropyl methylcellulose (HPMC) as shell polymers. The effect of shell formation was observed by comparing core–shell encapsulates with conventional 2-fluid nozzle (2FN) encapsulates. Also, the effect of pH of whey protein on the color of encapsulates is noteworthy; reducing the pH to 4.0 significantly improved the lightness value (52.91 ± 0.13) when compared with the encapsulates with native pH (38.91 ± 0.58). Furthermore, sample with pectin as shell polymer exhibited fair flowability with lowest values of Hausner ratio (1.25 ± 0.04) and Carr’s index (20.06 ± 2.71) and highest encapsulation efficiency for folic acid (86.07 ± 5.24%). Whereas, encapsulates having HPMC as shell polymer showed highest lightness value (60.80 ± 0.32) and highest encapsulation efficiency for iron (87.28 ± 4.15%). The formation of core–shell structure was confirmed by evaluation of the surface composition which showed reduced amine bonds and increased aliphatic and carbonyl bonds in the encapsulates prepared by 3FN spray drying. The encapsulates prepared without adjusting whey protein pH showed the least release (∼51 % in 24 h) and bioaccessibility (∼56%) of iron indicating the iron-whey protein complex formation. Based on appearance, smooth surface morphology, flowability, and release behavior, a combination of whey protein and pectin is recommended for co-encapsulation of iron, folic acid and ascorbic acid.

Formulation of Lipid-Based Nanoparticles for Simultaneous Delivery of Lapatinib and Anti-Survivin siRNA for HER2+ Breast Cancer Treatment.

In this work, lipid-based nanoparticles (LBNP) were designed to combine tyrosine kinase inhibitor (TKI) Lapatinib (LAPA) with siRNA directed against apoptosis inhibitor protein Survivin (siSurvivin) in an injectable form. This nanosystem is based on lipid nanocapsules (LNCs) coated with a cationic polymeric shell composed of chitosan grafted through a transacylation reaction. The hydrophobic LAPA is solubilized in the inner oily core, while hydrophilic siRNA is associated electrostatically onto the nanocarrier's surface. The co-loaded LBNP showed a narrow size distribution (polydispersity index (PDI) &lt; 0.3), a size of 130 nm, and a slightly positive zeta potential (+21 mV). LAPA and siRNA were loaded in LBNP at a high rate of &gt;90% (10.6 mM) and 100% (4.6 µM), respectively. The siRNA-LAPA_LBNP was readily uptaken by the human epidermal growth factor receptor 2 overexpressed (HER2+) breast cancer cell line SK-BR-3. Moreover, the cytotoxicity studies confirmed that the blank chitosan decorated LBNP is not toxic to the cells with the tested concentrations, which correspond to LAPA concentrations from 1 to 10 µM, at different incubation times up to 96 h. Furthermore, siCtrl.-LAPA_LBNP had a more cytotoxic effect than Lapatinib salt, while siSurvivin-LAPA_LBNP had a significant synergistic cytotoxic effect compared to siCtrl.-LAPA_LBNP. All these findings suggested that the developed modified LBNP could potentiate anti-Survivin siRNA and LAPA anti-cancer activity.