Capsule Interior Research Articles

Coupling dynamics of capsule interior defects and its impact on hydrodynamic instabilities at ablation fronts for inertial confinement fusion implosions

The micrometer-scale internal defect in the capsule is one of the most important factors that limit implosion performance in inertial confinement fusion (ICF) experiments, which creates instability seeds as shocks propagate through the capsule shell. Here, we report the generation mechanism of vortex pairs resulting from the interaction of shock waves with multiple bubbles, as well as the origin of more intricate perturbation waves than those observed in the case of single defects. Based on the subsequent evolution of hydrodynamic instability, it is evident that the vortex pairs induce the emergence of low-density (light-bubble case) or high-density (referred to as heavy-bubble case) jets on the ablative front. The presence of multiple side-by-side defects can rapidly amplify the dimensions of the jet. These jets could be responsible for the “meteor shower” observed in implosion experiments. Converging disturbed waves between vertically aligned defects lead to a more complex nonlinear flow field evolution compared to the scenario with a single defect. A systematic study of localized perturbation growth as a function of defect placement is presented. We investigate the dependence of circulation in the flow field on the locations of the defects. The scanning results of defect scenes with different sizes revealed the reason why the depth of fluid penetration is affected by the position and size, and found that the effects of the position and size on the perturbation expansion width can be equivalent to a certain extent. The extension of the perturbation width when the defect is off-axis limits the degree of penetration of the perturbation depth. The results contribute to a more comprehensive understanding of physical processes, such as the seeding mechanism, shell integrity, and mass injection into the central region, which may be applied to inform the development of more effective strategies to mitigate implosion degradation in ICF implosion experiments.

Dynamic of shock–bubble interactions and nonlinear evolution of ablative hydrodynamic instabilities initialed by capsule interior isolated defects

It is believed that isolated defects within the capsule (e.g., void, high-density inclusion) can be one of the essential factors for implosion performance degradation by seeding hydrodynamic instabilities in implosions. Nonetheless, a systematic study on how the isolated defects evolve and why they are not stabilized by ablation given the length scale comparable with the typical cutoff wavelength is still lacking. This paper addresses the above concerns by looking into a simplified model where a planar shell (without convergent geometry) is driven by laser direct-drive, with a single defect (low/high density) of micrometer or sub-micrometer scale residing at different locations inside. The underlying dynamics of two key physical processes are analyzed, i.e., the shock–bubble interactions as well as the subsequent nonlinear evolution of ablative hydrodynamic instabilities initiated by the direct interaction of the deformed defect and ablation front, revealing that compressibility and baroclinic effects drive vorticity production during the interactions between the shock wave and the isolated defect. In the “light-bubble” case, the vortex pair generated in the first process is further strengthened by the laser ablation. Hence, a directed flow is formed in companion with the persistent flow entering the bubble of the surrounding ablator. The bubble exhibits a remarkable growth both laterally and deeply, seriously threatening the shell's integrity. The positive feedback mechanism of the vortex pair is absent in the “heavy-bubble” counterpart, and the ablation stabilization manifested itself in the reduction of spike amplitude. A systematic study of localized perturbation growth as a function of defect placement, size, and preheating intensity is presented.

Antibacterial drug;Carboxy methyl cellulose;Chitosan;Colloidal particles;Drug delivery

Nanotechnology has provided numerous cutting-edge applications in drug delivery, biosensors, nanorobots, biomedical devices and nanocarriers. Polyelectrolyte mediated nanocapsules contributes a significant development as drug carriers for more than a decade. Majority of the nanocapsules employed in the drug delivery system are fabricated using synthetic materials leading to many health complications. In this research, natural polyelectrolyte capsules are prepared using carboxy methyl cellulose (CMC) and chitosan by dip coating technique. The capsules are used for the delivery of antibacterial drug by encapsulating ciprofloxacin hydrochloride into the capsule interiors. The drug release study has been carried out by altering the permeability of the capsule shell. The optimal pH for the drug encapsulation has been established at 2.3 pH and 381 μg of drug is loaded in 60 min. The drug release study is performed at three different pH conditions of 2.0 pH, 6.0 pH, and 7.2 pH respectively and the release media chosen is water and PBS. Maximum amount of drug release (367 μg) is achieved at pH 2.0 within 48 hours. The study demonstrates an easy and effective delivery of antibacterial drug from natural polyelectrolyte capsules.

Swellable hollow periodic mesoporous organosilica capsules with ultrahigh loading capacity for hydrophobic drugs.

As a new kind of drug carrier, practical applications of hollow periodic mesoporous organosilica (HPMO) have been greatly limited by their low loading capacity for hydrophobic drugs. In this work, we demonstrated the preparation of HPMO capsules with tunable shell thickness by using 1,2-bis(triethoxysilyl)ethane as the precursor. The capsules with thin shells and thus low Young's modulus showed excellent swellability to organic solvents containing hydrophobic drugs. As a result, hydrophobic drugs, i.e., paclitaxel (PTX) could be loaded into the hollow interior of the HPMO capsules with 4nm shell at an efficiency of ca. 120%. The as-prepared PTX-loaded HPMO capsules were dispersible in aqueous media and showed improved performance in killing cancer cells compared to free PTX.

Radiochemical capabilities for astrophysics experiments at the national ignition facility

The Nuclear and Radiochemistry Group at Lawrence Livermore National Laboratory (LLNL) has developed a suite of diagnostics and techniques that can be used for astrophysics experiments at the National Ignition Facility (NIF). Capabilities have been developed to add material to the outside of NIF hohlraum assemblies as well as to the interior of NIF target capsules or the fill gas. The ability to place very small amounts of material close to the NIF target enables activation with very large, short-pulse neutron fluxes. The Solid Radiochemistry Diagnostic can be used to collect solid debris from a NIF shot within 2 h of the execution of a shot, and this can be analyzed for radioactive signatures with or without post-shot chemical processing. The Radiochemical Analysis of Gaseous Samples diagnostic system can be used to collect gaseous products produced during a NIF shot. Capsule doping and radiochemical analysis capabilities at NIF will be discussed. The application of these techniques to astrophysical measurements will be discussed as well as some preliminary results.

Bioinspired Ether Cyclizations within a π-Basic Capsule Compared to Autocatalysis on π-Acidic Surfaces and Pnictogen-Bonding Catalysts.

While the integration of supramolecular principles in catalysis attracts increasing attention, a direct comparative assessment of the resulting systems catalysts to work out distinct characteristics is often difficult. Herein is reported how the broad responsiveness of ether cyclizations to diverse inputs promises to fill this gap. Cyclizations in the confined, π‐basic and Brønsted acidic interior of supramolecular capsules, for instance, are found to excel with speed (exceeding general Brønsted acid and hydrogen‐bonding catalysts by far) and selective violations of the Baldwin rules (as extreme as the so far unique pnictogen‐bonding catalysts). The complementary cyclization on π‐acidic aromatic surfaces remains unique with regard to autocatalysis, which is shown to be chemo‐ and diastereoselective with regard to product‐like co‐catalysts but, so far, not enantioselective.

PH-Responsive Capsules with a Fibril Scaffold Shell Assembled from an Amyloidogenic Peptide.

Peptides and proteins have evolved to self-assemble into supramolecular entities through a set of non-covalent interactions. Such structures and materials provide the functional basis of life. Crucially, biomolecular assembly processes can be highly sensitive to and modulated by environmental conditions, including temperature, light, ionic strength and pH, providing the inspiration for the development of new classes of responsive functional materials based on peptide building blocks. Here, it is shown that the stimuli-responsive assembly of amyloidogenic peptide can be used as the basis of environmentally responsive microcapsules which exhibit release characteristics triggered by a change in pH. The microcapsules are biocompatible and biodegradable and may act as vehicles for controlled release of a wide range of biomolecules. Cryo-SEM images reveal the formation of a fibrillar network of the capsule interior with discrete compartments in which cargo molecules can be stored. In addition, the reversible formation of these microcapsules by modulating the solution pH is investigated and their potential application for the controlled release of encapsulated cargo molecules, including antibodies, is shown. These results suggest that the approach described here represents a promising venue for generating pH-responsive functional peptide-based materials for a wide range of potential applications for molecular encapsulation, storage, and release.

Encapsulation of BSA/alginate water–in–water emulsions by polyelectrolyte complexation

Water-in-Water (W/W) emulsions were prepared in aqueous mixtures of an anionic polyelectrolyte (sodium alginate, NaAlg), with a globular protein (bovine serum albumin, BSA). This combination showed phase separation at two different intervals of pH, and their phase behavior was studied. BSA-in-alginate emulsions were obtained and dropped into Ca2+, Fe3+ or chitosan solutions, forming capsules with diameters around 2–4 mm, by ionic complexation of sodium alginate, located in the continuous phase of the emulsions. The results showed a strong dependence on the cation or polycation. Capsules prepared with Ca2+ were not robust and collapsed during freeze-drying, while Fe3+ induced the gelation of the interior of capsules, even at short (5 min) contact time. Better results were obtained when encapsulating with chitosan and applying longer immersion times. In these capsules, the liquid interior contained well-preserved BSA-in-alginate emulsions droplets, identical to the initial emulsions before encapsulating. Freeze-dried spherical capsules prepared with alginate/Fe3+ or alginate/chitosan shells had smooth surfaces, and a highly porous interior, templated by the presence of W/W emulsion droplets.

Aromaticity and Chemical Bonding of Chalcogen-Bonded Capsules Featuring Enhanced Magnetic Anisotropy.

We present a theoretical study of chalcogen bonded container capsules (AX +AX ) where X=O, S, Se, and Te, and their encapsulation complexes with n-C9 H20 (n-C9 H20 @AX +AX ). Both Se and Te encapsulation complexes have significant experimental and computed binding energies, analogous to the hydrogen bonded counterparts, while the S and O capsules and their encapsulation complexes show only weak binding energies, which are attributed to different types of bonding: chalcogen S⋅⋅⋅N bonds for S-capsules and π-π stacking and weak hydrogen bonds for the O case. All AX +AX and C9 H20 @AX +AX present unusually high magnetic anisotropies in their interiors. The 1 H NMR spectra of the encapsulation complexes display the proton signals of the encapsulated n-nonane highly upfield shifted, in agreement with the available experimental data for the Se capsule. We found that different factors contribute to the observed magnetic anisotropy of the capsule's interior: for the Te capsule the most important factor is Te's large polarizability; for the O analogue the inductive effects produced by the electronegative nature of the O and N heteroatoms; and for the S and Se capsules, the polarizability of the heteroatoms combines with electric field effects.

Encapsulation of Enzymes in Porous Capsules via Particle Templating.

The entrapment of enzymes in capsules is a smart strategy to concentrate them in confined spaces and control their exposure to outside environments. Enzymes can be caged in the interior of capsules during their formation (preloading) or postloaded within prefabricated and permeable hollow shells. On the other hand, enzymes can also be deposited within the shell or on the surface of the capsules. Each of these strategies has intrinsic limitations, and a common enemy is the undesired desorption of enzymes.Here, we describe the formation of enzyme-loaded polymeric capsules prepared with the Layer-by-Layer method and the template-assisted entrapment of enzymes through coprecipitation (preloading) within calcium carbonate particles, as an example of an efficient preloading strategy, and draw attention at the key parameters that influence this immobilization method.

Phagocyte-Inspired Smart Microcapsules.

Phagocytes protect the organism by ingesting harmful foreign particles and cells. We use mesoscale computer simulations to design a phagocyte-inspired active microcapsule that is capable of selectively capturing nanoparticles dispersed in solvent. Our fully synthetic microdevice is actuated by a temperature-sensitive microgel enclosed inside a perforated spherical shell. The shell pores are decorated with a copolymer brush that regulates the transport of solutes into the capsule interior. When exposed to an external stimulus, the microgel swells, expanding through the shell pores to make contact with the nanoparticle-rich solution surrounding the capsule. Upon removal of the external stimulus, the gel retracts back into the shell, bringing along with it captured nanoparticles. We probe how periodic application of the stimulus combined with nanoparticle-microgel adhesion enable selectivity and enhance capturing efficiency of our nature-inspired microdevice.

In situ redox reactions facilitate the assembly of a mixed-valence metal-organic nanocapsule

C-alkylpyrogallol[4]arenes (PgCs) have been studied for their ability to form metal-organic nanocapsules (MONCs) through coordination to appropriate metal ions. Here we present the synthesis and characterization of an MnII/MnIII-seamed MONC in addition to its electrochemical and magnetic behavior. This MONC assembles from 24 manganese ions and 6 PgCs, while an additional metal ion is located on the capsule interior, anchored through the introduction of bridging nitrite ions. The latter originate from an in situ redox reaction that occurs during the self-assembly process, thus representing a new route to otherwise unobtainable nanocapsules.

Bioinspired capsules based on nanocellulose, xyloglucan and pectin – The influence of capsule wall composition on permeability properties

Materials based on renewable biopolymers, selective permeability and stimuli-responsive release/loading properties play an important role in biomedical applications. Here, in order to mimic the plant primary cell-wall, microcapsules have been fabricated using cell wall polysaccharides, namely pectin, xyloglucan and cellulose nanofibers. For the first time, a large amount of xyloglucan was successfully included in such capsules. These capsules demonstrated stimuli-responsive (ON/OFF) permeability and biocompatibility. The live cell staining revealed that the microcapsules’ surface enhanced cell growth and also the non-toxic nature of the microcapsules. In water, the microcapsules were completely and partially permeable to fluorescent dextrans with an average molecular weight of 70 kDa (hydrodynamic diameter of ca. 12 nm) and 2000 kDa (ca. 54 nm), respectively. On the other hand, the permeability dropped quickly when the capsules were exposed to 250 mM NaCl solution, trapping a fraction of the 70 kDa dextrans in the capsule interior. The decrease in permeability was a direct consequence of the capsule-wall composition, i.e. the presence of xyloglucan and a low amount of charged molecules such as pectin. The low permeability of capsules in saline conditions (and in a model biological medium), combined with a capsule wall that is made from dietary fibers only, potentially enables their use in biological applications, such as colon targeted delivery in the gastro-intestinal tract. Statement of SignificanceFor the first time, microcapsules have been prepared that possess capsule walls that mimic the primary cell wall found in natural plant cells. The capsules were assembled using pectin, xyloglucan and cellulose in the form of cellulose nanofibers. The capsules demonstrated stimuli-responsive (ON/OFF) permeability and biocompatibility. The low permeability of capsules in saline conditions (and in a model biological medium), combined with a capsule wall that is made from dietary fibers only, potentially enables their use in biological applications, such as colon targeted delivery in the gastro-intestinal tract. Such model plant cell capsules might also further improve the understanding for the digestion and release of nutrients from natural plant cells found in vegetables and fruits.

Constraints on oxygen fugacity within metal capsules

Experiments were conducted with olivine encapsulated or wrapped in five different metals (Pt, Ni, $$\hbox {Ni}_{70}\hbox {Fe}_{30}$$ , Fe, and Re) to determine the oxygen fugacity in the interior of large capsules used for deformation and seismic property experiments. Temperature ( $$1200\,^{\circ }\hbox {C}$$ ), pressure (300 MPa), and duration (24 h) were chosen to represent the most common conditions in these experiments. The oxygen fugacity was determined by analysing the Fe content of initially pure Pt particles that were mixed with the olivine powder prior to the experiments. Oxygen fugacities in the more oxidizing metal containers are substantially below their respective metal-oxide buffers, with the $$\hbox {fO}_2$$ of sol–gel olivine in Ni about 2.5 orders of magnitude below Ni–NiO. Analysis of olivine and metal blebs reveals three different length-, and hence diffusive time scales: (1) Fe loss to the capsule over $$\sim$$ 100 $$\upmu \hbox {m}$$ , (2) $$\hbox {fO}_2$$ gradients at the sample–capsule interface up to 2 mm into the sample, and (3) constant interior $$\hbox {fO}_2$$ values with an ordering corresponding to the capsule material. The inferred diffusive processes are: Fe diffusion in olivine with a diffusivity $$\sim \,10^{-14}\,\hbox {m}^2\hbox {/s}$$ , diffusion possibly of oxygen along grain boundaries with a diffusivity $$\sim \,10^{-12}\,\hbox {m}^2\hbox {/s}$$ , and diffusion possibly involving pre-existing defects with a diffusivity $$\sim \,10^{-10}\,\hbox {m}^2\hbox {/s}$$ . The latter, fast adjustment to changing $$\hbox {fO}_2$$ may consist of a rearrangement of pre-existing defects, representing a metastable equilibrium, analogous to decoration of pre-existing defects by hydrogen. Full adjustment to the external $$\hbox {fO}_2$$ requires atomic diffusion.

Strong cation···π interactions promote the capture of metal ions within metal-seamed nanocapsule.

Thallium ions are transported to the interior of gallium-seamed pyrogallol[4]arene nanocapsules. In comparison to the capture of Cs ions, the extent of which depends on the type and position of the anion employed in the cesium salt, the enhanced strength of Tl···π vs Cs···π interactions facilitates permanent entrapment of Tl+ ions on the capsule interior. “Stitching-up” the capsule seam with a tertiary metal (Zn, Rb, or K) affords new trimetallic nanocapsules in solid state.

Entrapment of elusive guests within metal-seamed nanocapsules.

Anions play a crucial role in locking alkali metals on the interior of metal-organic capsules that contain structural water gates. This role is further evidenced when stitching-up the capsule seam, resulting in either expulsion or trapping of cesium ions depending on the anion employed.

The effects of early time laser drive on hydrodynamic instability growth in National Ignition Facility implosions

Defects on inertial confinement fusion capsule surfaces can seed hydrodynamic instability growth and adversely affect capsule performance. The dynamics of shocks launched during the early period of x-ray driven National Ignition Facility (NIF) implosions determine whether perturbations will grow inward or outward at peak implosion velocity and final compression. In particular, the strength of the first shock, launched at the beginning of the laser pulse, plays an important role in determining Richtmyer-Meshkov (RM) oscillations on the ablation front. These surface oscillations can couple to the capsule interior through subsequent shocks before experiencing Rayleigh-Taylor (RT) growth. We compare radiation hydrodynamic simulations of NIF implosions to analytic theories of the ablative RM and RT instabilities to illustrate how early time laser strength can alter peak velocity growth. We develop a model that couples the RM and RT implosion phases and captures key features of full simulations. We also show how three key parameters can control the modal demarcation between outward and inward growth.

Rattle-type hierarchical particles containing multilevel cores (Ag@AgCl@SiO2 and Au/Ag@AgCl@SiO2) as versatile catalysts

A protocol for the synthesis of rattle-type core@shell particles containing Ag@AgCl or Au/Ag@AgCl core structures was developed, and the use of these particles as catalysts for the decomposition of toxic materials was demonstrated. A monometallic Ag or bimetallic Au/Ag core was incorporated into the interior of SiO2 capsules via controlled heat treatment of metal nanoparticle/SiO2-coated polymer particles, resulting in the formation of rattle-type core@shell structures. By appropriate treatments, it was possible to transform the Ag or Au/Ag core into multilevel cores (Ag@AgCl or Au/Ag@AgCl) within the SiO2 capsules (Ag@AgCl@SiO2 or Au/Ag@AgCl@SiO2). This method for the synthesis of rattle-type core@shell particles is useful for further introducing AgCl fused with plasmonic materials into the capsule structures. The rattle-type core@shell structures were used as photocatalysts for the decomposition of organic pollutants such as methyl orange. Furthermore, these nanocatalysts containing semiconductors such as AgCl were also applied toward the reduction of nitrophenol (NPh) to aminophenol (APh). The Ag@AgCl@SiO2 or Au/Ag@AgCl@SiO2 catalysts showed excellent catalytic properties in the decomposition of toxic substances in terms of their activity and reusability.

Direct Delivery of Functional Proteins and Enzymes to the Cytosol Using Nanoparticle-Stabilized Nanocapsules

Intracellular protein delivery is an important tool for both therapeutic and fundamental applications. Effective protein delivery faces two major challenges: efficient cellular uptake and avoiding endosomal sequestration. We report here a general strategy for direct delivery of functional proteins to the cytosol using nanoparticle-stabilized capsules (NPSCs). These NPSCs are formed and stabilized through supramolecular interactions between the nanoparticle, the protein cargo, and the fatty acid capsule interior. The NPSCs are ~130 nm in diameter and feature low toxicity and excellent stability in serum. The effectiveness of these NPSCs as therapeutic protein carriers was demonstrated through the delivery of fully functional caspase-3 to HeLa cells with concomitant apoptosis. Analogous delivery of green fluorescent protein (GFP) confirmed cytosolic delivery as well as intracellular targeting of the delivered protein, demonstrating the utility of the system for both therapeutic and imaging applications.

Lessons in Microcapsule Assembly from Imaging Delivery of a Bioluminescent Enzyme

Layer-by-layer assembled microcapsules have potential applications as delivery and biosensing systems, which make them attractive tools for use in various aspects of nanomedicine. We examined the effect of microcapsule location on activity of the bioluminescent enzyme luciferase in both intact capsules and following cell uptake. In intact capsules, the rate of reaction of luciferase was greatest for luciferase in the outer layer and least in the core. Following cell uptake, luciferase in the outer layer was rapidly reactive, and a similar rate of reaction and activity was observed for luciferase placed in capsule interior (core). By contrast, there was minimal activity detected when microcapsules with luciferase sandwiched between polyelectrolytes in a middle layer were delivered to cells. This study informs us of the availability of bioactive molecules located in different positions within microcapsules and will enable better microcapsule construction in line with the intended application, particularly delivery of functional proteins to cells.