Polymer Capsules Research Articles

Hollow Polymeric Capsules from POSS-Based Block Copolymer for Photodynamic Therapy

A novel amphiphilic diblock copolymer, PHEMAPOSS-b-P(DMAEMA-co-CMA), was prepared via reversible addition–fragmentation chain transfer (RAFT) polymerization, where PHEMAPOSS block was first synthesized using a methacrylate monomer based on polyhedral oligomeric silsesquioxane (HEMAPOSS), and PHEMAPOSS was further utilized to prepare the block copolymer via RAFT copolymerization of 2-(dimethylamino)ethyl methacrylate (DMAEMA) and reduction-cleavable coumarin methacrylate (CMA) monomer. PHEMAPOSS-b-P(DMAEMA-co-CMA) could self-assemble in water to form spherical micelles with POSS core and stimuli-responsive shell. The micelles were cross-linked by photodimerization of coumarin, and then hollow polymeric capsules could be finally obtained via etching the POSS core in the solution of hydrofluoric acid (HF). The morphologies of the micelles and hollow polymeric capsules were well characterized by TEM, SEM, and DLS. The hollow polymeric capsules are responsive to typical physiological stimuli such as pH, and re...

CFD Analysis of Coffee Packaging in Capsules using Gas Flushing Modified Atmosphere Packaging

Abstract The aim of this work is to analyze, by means of CFD (Computational Fluid Dynamics), the gas flow in a packaging machine used to fill polymeric capsules with coffee. The final goal is to optimize the geometric shape of some mechanical components in the machine’s sealing station in order to reduce the inert gas consumption achieving an O2 residual which is constantly equal or below 1 % by mass in the center of the capsule. The fluid domain has been obtained starting from the 3D CAD model of the sealing station of the packaging machine. The CAD software SolidWorks has been used to design the system, while Ansys CFX 14.5 software has been used for the CFD analysis. The CFD model has been validated by comparing its results with those obtained by experimental tests. The modified solution allows reducing the average O2 residual from about 3 % to less than 1 %.

Temperature-Controlled Switchable Photochromism in Solid Materials.

A novel strategy to achieve thermally switchable photochromism in solid materials is reported, which relies on the preparation of polymeric core-shell capsules containing solutions of photochromic dyes in acidic phase-change materials. Upon changing the phase (solid or liquid) of the encapsulated medium, one of the two photochromic states of the system is selectively stabilized on demand, allowing for reversible interconversion between direct and reverse photochromism when thermally scanning through the melting temperature of the phase-change material. This strategy, which does not require the addition of external agents or chemical modification of the dyes, proved to be general for different spiropyran photochromes and to be applicable to the fabrication of a variety of functional materials by simply embedding the capsules obtained into a solid matrix of choice.

Block Copolymer Capsules with Structure-Dependent Release Behavior.

Although high-boiling non-solvent induced macrophase separation in emulsion droplets has been widely applied for the fabrication of polymeric capsules, precise control of their structures remains a great challenge. Herein, block copolymer capsules with tunable shell structures were fabricated by employing a non-solvent as a liquid template in emulsion droplets. The properties of the non-solvents dictate the phase separation sequence in the droplets and the capsule formation mechanism. Two different pathways for capsule formation were observed, and could be applied to predict the shell structure. The structured capsules could be transformed into mesoporous capsules, which demonstrated an intriguing structure-dependent release behavior. Capsules with spherical shell structures displayed the best permeability, while those with lamellar shell structures showed the slowest release, but with a stepwise profile. After loading with an anticancer drug, different capsules induced different apoptosis ratios in cancer cell studies.

Block Copolymer Capsules with Structure‐Dependent Release Behavior

AbstractAlthough high‐boiling non‐solvent induced macrophase separation in emulsion droplets has been widely applied for the fabrication of polymeric capsules, precise control of their structures remains a great challenge. Herein, block copolymer capsules with tunable shell structures were fabricated by employing a non‐solvent as a liquid template in emulsion droplets. The properties of the non‐solvents dictate the phase separation sequence in the droplets and the capsule formation mechanism. Two different pathways for capsule formation were observed, and could be applied to predict the shell structure. The structured capsules could be transformed into mesoporous capsules, which demonstrated an intriguing structure‐dependent release behavior. Capsules with spherical shell structures displayed the best permeability, while those with lamellar shell structures showed the slowest release, but with a stepwise profile. After loading with an anticancer drug, different capsules induced different apoptosis ratios in cancer cell studies.

"Killer" Microcapsules That Can Selectively Destroy Target Microparticles in Their Vicinity.

We have developed microscale polymer capsules that are able to chemically degrade a certain type of polymeric microbead in their immediate vicinity. The inspiration here is from the body's immune system, where killer T cells selectively destroy cancerous cells or cells infected by pathogens while leaving healthy cells alone. The "killer" capsules are made from the cationic biopolymer chitosan by a combination of ionic cross-linking (using multivalent tripolyposphate anions) and subsequent covalent cross-linking (using glutaraldehyde). During capsule formation, the enzyme glucose oxidase (GOx) is encapsulated in these capsules. The target beads are made by ionic cross-linking of the biopolymer alginate using copper (Cu2+) cations. The killer capsules harvest glucose from their surroundings, which is then enzymatically converted by GOx into gluconate ions. These ions are known for their ability to chelate Cu2+ cations. Thus, when a killer capsule is next to a target alginate bead, the gluconate ions diffuse into the bead and extract the Cu2+ cross-links, causing the disintegration of the target bead. Such destruction is visualized in real-time using optical microscopy. The destruction is specific, i.e., other microparticles that do not contain Cu2+ are left undisturbed. Moreover, the destruction is localized, i.e., the targets destroyed in the short term are the ones right next to the killer beads. The time scale for destruction depends on the concentration of encapsulated enzyme in the capsules.

Sub-Micrometer Magnetic Nanocomposites: Insights into the Effect of Magnetic Nanoparticles Interactions on the Optimization of SAR and MRI Performance.

There is increasing interest in the development of new magnetic polymeric carriers for biomedical applications such as trigger-controlled drug release, magnetic hyperthermia (MH) for the treatment of cancer, and as contrast agents in magnetic resonance imaging (MRI). This work describes the synthesis of sub-micrometer and magnetic polymer nanocomposite capsules (MPNCs) by combining in one single platform the biodegradable polymer poly-ε-caprolactone (PCL) and different concentrations of ∼8 nm oleic acid (OA)-functionalized magnetite nanoparticles (Fe3O4@OA), employing the oil-in-water emulsion/solvent evaporation method. The MPNCs showed a significant increase in particle size from ∼400 to ∼800 nm as the magnetic loading in the organic-inorganic hybrids increases from 1.0% to 10%. The MPNCs presented high incorporation efficiency of Fe3O4@OA nanoparticles, good colloidal stability, and super-paramagnetic properties. Interestingly, electron microscopy results showed that the Fe3O4@OA nanoparticles were preferentially located at the surface of the capsules. Evaluation of the magnetic properties showed that the saturation magnetization and the blocking temperature of the MPNCs samples increased as a function of the Fe3O4@OA loading. All the MPNCs exhibited heating when subjected to MH, and showed good specific absorption rates. Use of the formulations decreased the longitudinal (T1) and transverse (T2) relaxation times of water protons' nuclei, with excellent transverse relaxivity (r2) values, especially in the case of the formulation with lowest Fe3O4@OA loading. Furthermore, the MPNCs-cell interaction was studied, and MPNCs showed lower cellular toxicity to normal cells compared to cancer cells. These findings help in understanding the relationships between magnetic nanoparticles and polymeric capsules, opening perspectives for their potential clinical uses as simultaneous heating sources and imaging probes in MH and MRI, respectively.

Temperature rise around nanoparticles

Nanoscale heating governs a multitude of processes relevant to molecular states and biomolecular functionality. In this mini-review, we describe application of localized laser–nanoparticle heating for polymeric polyelectrolyte capsules and layers, covering the principles governing the nanoscale laser-induced heat generation, synthesis of nanoparticles and their adsorption on polyelectrolyte multilayer membrane and different applications of these effects. Release of encapsulated materials is considered as one of the methods of release, while its further application is linked, among others, with intracellular delivery and release of encapsulated peptides, remotely controlled reactors, polymeric surface properties and corrosion protection.

Surface Modification of ICF Target Capsules by Pulsed Laser Ablation

Topographical modifications of spherical surfaces are imprinted on National Ignition Facility target capsules by extending the capabilities of a recently developed full-surface (4π) laser ablation and mapping apparatus. The laser ablation method combines the precision, energy density, and long reach of a focused laser beam to preimpose sinusoidal modulations on the outside surface of high-density carbon capsules and the inside surface of glow discharge polymer capsules. Sinusoidal modulations described in this paper have submicron to tens of microns vertical scale and wavelengths as small as 30 μm and as large as 200 μm. The modulated patterns are created by rastering a focused laser fired at discrete capsule surface locations for a specified number of pulses. The computer program developed to create these raster patterns uses inputs such as the laser beam intensity profile, the material removal function, the starting surface figure, and the desired surface figure. The patterns are optimized to minimize surface roughness. In this paper, simulated surfaces are compared with actual ablated surfaces measured using confocal microscopy.

Polymer Capsules for Plaque-Targeted In Vivo Delivery.

Adv. Mater. 2016, 28, 7703–7707 In the originally published article, the authors omitted to add the use of a second targeting ligand (single-chain antibody, scFv, against activated platelets), and the following changes are required to address this. The arguments and conclusions of the original Communication are not affected. The caption of Figure 4 “T-peptide-conjugated PDPA-HIS capsules” should read “single-chain antibody-conjugated PDPA-HIS capsules”. In the figure the word “sequence” should be disregarded. On page 3, paragraph 3 of the article, the following changes are required: (i) The text “and control PDPA-HIS capsules with a randomized sequence (GLGYGWS)” should be changed to “and control PDPA-HIS capsules without the scFv”. (ii) “The T-peptide functionalized capsules could accumulate specifically at sites with an abundance of MMP2 degraded collagen IV, such as plaques.” should read “scFv-functionalized capsules could accumulate specifically in the plaque.” (iii) “The increased accumulation of the capsules in the liver compared to the kidneys suggests higher MMP2 activity in the liver that could present more binding sites for the T-peptide” should read “The increased accumulation of the capsules in the liver compared to the kidneys suggests higher inflammation-related platelet presence in the liver”. On page 4, paragraph 1 of the article, the text “These specialized macrophages produce MMP2 and create more binding sites of collagen IV in the liver. Another possible reason is that the MMP2 mediated cleavage of the ACPP attached to the capsules promotes entry of the capsule into hepatocytes.” should be disregarded. In the conclusion, the sentence “Finally, the capsules were functionalized with a targeting peptide” should read “Finally, the capsules were functionalized with a targeting peptide or scFv”. In the Experimental Section under Plaque-Targeting Experiments, “200 μL of the T-peptide-conjugated PDPA-HIS capsules or random sequence-conjugated control PDPA-HIS capsules” should read “200 μL of the scFv-conjugated PDPA-HIS capsules or control PDPA-HIS capsules”. The authors apologise for any inconvenience caused.

Microfluidics and Macromolecules: Top‐Down Analytics and Bottom‐Up Engineering of Soft Matter at Small Scales

Microfluidics is the art of creating and manipulating small portions of fluids. A typical variant of this art is fluid transport within small channels, either in form of laminar co‐flow of miscible streams or in form of segmented‐flow dripping and jetting of immiscible streams. Either method provides means to expose components of interest to defined local conditions such as spatially controlled concentration profiles that could not be established without the microfluidic auxiliaries. This ability renders microfluidics uniquely useful as both a method for advanced analytics and synthesis. This article sheds a spotlight on the use and utility of this method in macromolecular chemistry and physics. In this field, the synthetic aspect of microfluidics has been widely explored in macromolecular materials engineering, primarily by the use of droplets as templates to form various types of polymeric particles and capsules, whereas the analytical aspect has most prominently been employed for research on biopolymers.image

High accuracy measurement line in microwave range for polymer samples weak doped with BaTiO3

The nowadays tendencies regarding the process of making microprocessors presume architectures that, in the nearby future, it would be possible, to work on a frequency located between the range 5-10 GHz. In this context, it is imperious to know the behaving of the plastic materials that build the microchip in the microwave frequency range, as well as the behaving of the polymeric capsule of the electrical capacitors from the electric circuits. The aim of this contribution is to demonstrate throughout high-level experimental analysis how the main electric parameters of plastic materials, which build the microchip capsule and the one of electric capacitors, depend on the frequencies on which they work from the microwave range.

Targeted Stealth Polymer Capsules Encapsulating Ln3+-Doped LaVO4 Nanoparticles for Bioimaging Applications.

We report synthesis of targeted PEGylated polymer capsules encapsulating Stoke's shift and upconverting LaVO4 nanoparticles by following a unique approach for bioimaging applications. First, LaVO4:Ln3+@silica (Ln3+ = Tb3+, Eu3+, and Yb3+/Er3+) core-shell nanoparticles are prepared by sol-gel method followed by layer-by-layer assembly of polymers and PEGylation over core-shell particles. Second, removal of silica core facilitates the trapping of LaVO4:Ln3+ nanoparticles inside the PEGylated polymer capsules. Finally, capsules are surface modified with antibodies to target cancer cells. The nanoparticles-loaded polymer capsules are found to be internalized and biocompatible with various cells (e.g., HeLa, A498, H460, MCF-7, Schwann, L929, and IC-21) suggesting their applicability in different types of cells. In addition, the capsules modified with antibodies show more specific uptake suggesting their targeting ability by 3-fold for MCF-7 and 10-fold for H460 cancer cells. Moreover, the nanoparticle-loaded polymer capsules were internalized by HeLa cells via macropinocytosis mechanism. We observed localized bright Stoke's shift (Tb3+ ions, λex = 488 nm) and upconversion (Er3+ ions, λex = 980 nm) green fluorescence from cells suggesting their potential use as targeted bioimaging agents.

Inhibitor-loaded conducting polymer capsules for active corrosion protection of coating defects

This work presents the synthesis of nanostructured hollow polyaniline (PANI) capsules and their application for encapsulation of corrosion inhibitor 2-Mercaptobenzothiazole (MBT). The pH-triggered release of MBT from the capsules was evidenced using UV–vis and Surface Enhanced Raman Spectroscopy (SERS). Incorporation of MBT loaded PANI capsules into epoxy ester coating on AA2024-T3 resulted in a protective system with self-healing ability confirmed by Electrochemical Impedance Spectroscopy (EIS) and Scanning Vibrating Electrode Technique (SVET). The results showed that the incorporation of MBT-loaded PANI capsules into the coating has significantly improved its corrosion protection performance due to the interesting smart characteristics of PANI capsules.

Polymer Capsules for Plaque-Targeted In Vivo Delivery.

Targeted polymer capsules can selectively bind to unstable plaques in mice after intravenous injection. Different formulations of the capsules are explored with a synthetic/biopolymer hybrid capsule showing the best stability and small-molecule drug retention. The synthetic polymer is composed of pH-sensitive blocks (PDPA), low-binding blocks (PEG), and click-groups for postfunctionalization with targeting peptides specific to plaques.

Subdiffraction-Resolution Optical Measurements of Molecular Transport in Thin Polymer Films.

The measurement of molecular transport within polymer films yields information about the internal structural organization of the films and is useful in applications such as the design of polymeric capsules for drug delivery. Layer-by-layer assembly of polyelectrolyte multilayer films has been widely used in such applications where the multilayer structure often exhibits anisotropic transport resulting in different diffusivities in the lateral (parallel to the film) and transverse (normal to the film) directions. Although lateral transport can be probed using techniques such as fluorescence recovery after photobleaching (FRAP), it cannot be applied to probing transverse diffusivity in polymer films smaller than the diffraction limit of light. Here we present a technique to probe the transport of molecules tagged with fluorphores in polymer films thinner than the optical diffraction limit using the modulation of fluorescence emission depending on the distance of the tagged molecules from a metal surface. We have used this technique to probe the diffusion of proteins biotin and bovine serum albumin (BSA) in polyelectrolyte multilayer films. We also studied the interdiffusion of chains in multilayer films using this technique. We observed a 3 order of magnitude increase in interdiffusion as a function of the ionic strength of the medium. This technique, along with FRAP, will be useful in studying anisotropic transport in polymer films, even those thinner than the diffraction limit, because the signal in this technique arises only from transverse and not lateral transport. Finally, this technique is also applicable to studying the diffusion of chromophore-labeled species within a polymer film. We demonstrate this aspect by measuring the transverse diffusion of methylene blue in the PAH-PAA multilayer system.

Controlling the Vaterite CaCO3 Crystal Pores. Design of Tailor-Made Polymer Based Microcapsules by Hard Templating.

The spherical vaterite CaCO3 microcrystals are nowadays widely used as sacrificial templates for fabrication of various microcarriers made of biopolymers (e.g., proteins, nucleic acids, enzymes) due to porous structure and mild template elimination conditions. Here, we demonstrated for the first time that polymer microcarriers with tuned internal nanoarchitecture can be designed by employing the CaCO3 crystals of controlled porosity. The layer-by-layer deposition has been utilized to assemble shell-like (hollow) and matrix-like (filled) polymer capsules due to restricted and free polymer diffusion through the crystal pores, respectively. The crystal pore size in the range of few tens of nanometers can be adjusted without any additives by variation of the crystal preparation temperature in the range 7-45 °C. The temperature-mediated growth mechanism is explained by the Ostwald ripening of nanocrystallites forming the crystal secondary structure. Various techniques including SEM, AFM, CLSM, Raman microscopy, nitrogen adsorption-desorption, and XRD have been employed for crystal and microcapsule analysis. A three-dimensional model is introduced to describe the crystal internal structure and predict the pore cutoff and available surface for the pore diffusing molecules. Inherent biocompatibility of CaCO3 and a possibility to scale the porosity in the size range of typical biomacromolecules make the CaCO3 crystals extremely attractive tools for template assisted designing tailor-made biopolymer-based architectures in 2D to 3D targeted at drug delivery and other bioapplications.

Preparation of novel capsosome with liposomal core by layer-by-Layer self-assembly of sodium hyaluronate and chitosan

Multi-compartmentalized capsosomes are polyelectrolyte capsules with liposomes as cargo, and are prepared by combining liposomes and polymer capsules. They offer additional functionality while maintaining the advantages and compensating for the weak points of both systems. In this study, a polyelectrolyte multilayered liposome was prepared by alternating adsorption of negatively charged sodium hyaluronate (HA) and positively charged chitosan (CH) on the surface of a cationic core liposome (CL) via layer-by-layer (LbL) deposition. Then, smaller sized liposomes (L) were coated onto the multilayered liposome. Lastly, the particle surfaces were coated with HA as a capping layer to obtain a novel type of capsosome with a liposomal core. The amount of adsorbed liposome was measured for different pH values (pH 2–10) and with liposome solutions of different concentrations (1–3%). The highest liposome adsorption occurred at pH 10 in the 3% solution, respectively. Finally, capsosomes in the size range of 500nm to 2μm were observed and the attached liposomes were located both on the surface and within the polymer shell. In conclusion, the cell-mimicking, liposome-based capsosomes could have infinite applications in the field of medicine, pharmaceuticals, and cosmetics as compartmentalized microreactors, multi-drug delivery systems with controlled release, or functional artificial cells in the future.

Shape-Dependent Activation of Cytokine Secretion by Polymer Capsules in Human Monocyte-Derived Macrophages.

Particles with tailored geometries have received significant attention due to their specific interactions with biological systems. In this work, we examine the effect of polymer capsule shape on cytokine secretion by human monocyte-derived macrophages. Thiolated poly(methacrylic acid) (PMASH) polymer capsules with different shapes (spherical, short rod-shaped, and long rod-shaped) were prepared by layer-by-layer assembly. The effect of PMASH capsule shape on cellular uptake and cytokine secretion by macrophages differentiated from THP-1 monocytes (dTHP-1) was investigated. PMASH capsules with different shapes were internalized to a similar extent in dTHP-1 cells. However, cytokine secretion was influenced by capsule geometry: short rod-shaped PMASH capsules promoted a stronger increase in TNF-α and IL-8 secretion compared with spherical (1.7-fold in TNF-α and 2.1-fold in IL-8) and long rod-shaped (2.8-fold in TNF-α and 2.0-fold in IL-8) PMASH capsules in dTHP-1 cells (capsule-to-cell ratio of 100:1). Our results indicate that the immunological response based on the release of cytokines is influenced by the shape of the polymer capsules, which could be potentially exploited in the rational design of particle carriers for vaccine delivery.

Fabrication of polyelectrolyte multilayered nano-capsules using a continuous layer-by-layer approach

The layer-by-layer approach is a highly versatile method for the fabrication of multilayered polymeric films and capsules. It has been widely investigated in research for various polyelectrolyte pairs and core template particles. However, the fabrication of nano-sized capsules at the larger scale is difficult and time consuming, due to the necessity of washing and centrifugation steps before the deposition of each polyelectrolyte layer. This results not only in a very long fabrication time, but also in the partial loss of particles during those intermediate steps. In this study, we introduced a continuous approach for the fabrication of multilayer polyelectrolyte based nano-capsules using calcium phosphate core nanoparticles and a tubular flow type reactor with the potential for synthesizing tens of milligrams of capsules per hour. Adsorption of the polyelectrolyte layer occurred in the tubing where particles and polyelectrolyte solution of choice were mixed, creating a layer of polyelectrolyte on the particles. After this, these newly surfaced-modified particles passed into the next segment of tubing, where they were mixed with a second polyelectrolyte of opposite charge. This process can be continuously repeated until the desired number of layers is achieved. One potential problem with this method concerned the presence of any excess polyelectrolyte in the tubing, so careful control of the amount of polymer added was crucial. It was found that slightly under dosing the amount of added polyelectrolyte ensured that negligible unadsorbed polyelectrolyte remained in solution. The particles created at each deposition step were stable, as they all had a zeta potential of greater than ±25mV. Furthermore the zeta potential measurements showed that charge reversal occurred at each stage. Having achieved the necessary number of polyelectrolyte layers, the calcium phosphate cores were easily removed via dissolution in either hydrochloric or acetic acid.