Hollow Polyelectrolyte Research Articles

Rapid, Highly-Efficient and Selective Removal of Anionic and Cationic Dyes from Wastewater Using Hollow Polyelectrolyte Microcapsules

Herein, poly (allylamine hydrochloride) (PAH)/ poly (styrene sulfonic acid) sodium salt (PSS) microcapsules of (PAH/PSS)2PAH (P2P MCs) and (PAH/PSS)2 (P2 MCs) were obtained by a layer-by-layer method. The P2 MCs show high adsorption capacity for Rhodamine B (642.26 mg/g) and methylene blue (909.25 mg/g), with an extremely low equilibrium adsorption time (~20 min). The P2P MCs exhibited high adsorption capacities of reactive orange K-G (ROKG) and direct yellow 5G (DY5G) which were 404.79 and 451.56 mg/g. Adsorption processes of all dyes onto microcapsules were best described by the Langmuir isotherm model and a pseudo-second-order kinetic model. In addition, the P2P MCs loaded with reactive dyes (P2P-ROKG), could further adsorb rhodamine B (RhB) dye, and P2 MCs that had adsorbed cationic MB dyes could also be used for secondary adsorption treatment of direct dye waste-water, respectively. The present work confirmed that P2P and P2 MCs were expected to become an excellent adsorbent in the water treatment industry.

Structure of swollen hollow polyelectrolyte nanogels with inhomogeneous cross-link distribution

Hypothesis: Recently, it has become possible to synthesize hollow polyelectrolyte nano- and microgels. The shell permeability can be controlled by external stimuli, while the cavity can serve as a storage place for guest molecules. However, there is a lack of a detailed understanding at the molecular level regarding the role of the network topology, inhomogeneities of the distribution of cross-links, and the impact of the electrostatics on the structural response of hollow microgel to external stimuli. To bridge these gaps, molecular dynamics (MD) of computer simulations are used.Experiments: Here, we propose a fresh methodology to create realistic hollow microgel particles in silico. The technique involves a gradual change in the average local length of subchains depending on the distance to the center of mass of the microgel particles resulting in the microgels with a non-uniform distribution of cross-linking species. In particular, a series of microgels with (i) a highly cross-linked inner part of the shell and gradually decreased cross-linker concentration towards the periphery, (ii) microgels with loosely cross-linked inner and outer parts, as well as (iii) microgels with a more-or-less homogeneous structure, have been created and validated. Counterions and salt ions are taken into account explicitly, and electrostatic interactions are described by the Coulomb potential.Findings: Our studies reveal a strong dependence of the microgel swelling response on the network topology. Simple redistribution of cross-links plays a significant role in the structure of the microgels, including cavity size, microgel size, fuzziness, and extension of the inner and outer parts of the microgels. Our results indicate the possibilities of qualitative justification of the structure of the hollow microgels in the experiments by measuring the relative change in the size of the sacrificial core to the size of the cavity and by estimation of a power law function, RH∼csα, of the hydrodynamic radius of the hollow microgels as a function of added salt concentration.

Biocompatible hydroxyapatite nanoparticles as templates for the preparation of thin film polyelectrolyte multilayer nanocapsules

Thin films called polyelectrolyte multilayers could be formed by alternate adsorption of positively and negatively charged polyelectrolytes. In the case of adsorption on nanoparticles followed by the dissolution of the template, it is possible to prepare hollow polyelectrolyte capsules. Due to a large number of available polymeric compounds and easily tunable multilayer properties, these systems find their application in various fields such as biomedicine and catalysis. In this study we focused on the design, synthesis and characterization of capsules of nanometer dimensions made of nontoxic weak polyelectrolytes, poly(allylamine) and poly(acrylic acid) in a water medium using fully biocompatible hydroxyapatite nanoparticles as template. The formation of the polyelectrolyte multilayer was monitored by measuring the electrophoretic mobility of particles. After the optimization of the core decomposition conditions, hollow polyelectrolyte capsules were prepared by dissolution of the template in the presence of HCl. Further characterization was performed using Fourier-transform infrared spectroscopy, energy dispersion X-ray spectroscopy, dynamic light scattering, scanning electron microscopy, and atomic force microscopy. With these techniques, the chemical composition, structure, size, morphology and stability of obtained nanocapsules were determined. It was found that the capsules are of a rather narrow size distribution ranging from 100 to 250 nm with a flexible capsule wall being only a few tens of nanometers thick which is very important in the case of future applications in the field of drug delivery. Moreover, the dispersions of nanocapsules were stable for at least 40 days. This extreme stability of nanocapsules could be probably attributed to their low mass, small dimensions, and high surface charge.

Open and dense hollow fiber nanofiltration membranes through a streamlined polyelectrolyte-based spinning process

Polyelectrolyte composite hollow fiber membranes show a high potential to become applied in industrial nanofiltration applications such as water purification or downstream processing in several industries. This material platform allows multiple routes to achieve tailored selectivities and high permeances. Hollow fiber membranes promise a higher process efficiency due to higher packing densities and their backwash stability. However, the fabrication of composite polyelectrolyte hollow fiber nanofiltration membranes is more challenging compared to state of the art spiral wound modules. While the Layer-by-Layer deposition has proven versatile opportunities and is recently entering the commercial market, the multi-step post-treatment is elaborate. In this work, we streamline the fabrication of polyelectrolyte composite hollow fiber membranes. We extend our recently presented ”chemistry-in-a-spinneret” approach with a membrane modification in a subsequent coating bath. The additional modification can be incorporated in the composite hollow fiber membrane manufacturing process without additional process steps. Sulfonated polyethersulfone as a polyanionic additive is used in the polymer solution which complexates with the polycations polyethylenimine (PEI) or poly(diallyldimethylammonium chloride (PDADMAC) in the bore fluid during fiber spinning. The extruded fibers have a positively charged lumen surface which allows a subsequent modification with the polyanion poly(sodium 4-styrenesulfonate) (PSS) in the coating bath. The spun fibers reveal with 16-4 LMH/bar pure water permeance (PWP) and 2000-1100 Dalton (Da) molecular weight cut-off (MWCO) open nanofiltration characteristics, while the PEI+PSS modified fibers show dense nanofiltration characteristics (0.6 LMH/bar PWP and 360 Da MWCO). The fibers are backwash stable and the PDADMAC and PDADMAC+PSS fibers show a significantly higher sodium hypochlorite (NaOCl) stability compared to the PEI and PEI+PSS fibers. This new technique creates composite hollow fiber nanofiltration membranes with a polyelectrolyte bilayer without multi-step post-treatment. Therefore, it provides a promising alternative to the Layer-by-Layer post-modification, where two coating steps and one water washing post-treatment step are required to create a polyelectrolyte bilayer on a porous hollow fiber membrane support. • Composite hollow fiber nanofiltration membranes without multi-step post-treatment. • The chemistry in a spinneret technique is extended with a polyanion coating step. • Backwash stable hollow fibers feature open or dense NF characteristics. • PDADMAC and PDADMAC+PSS show higher NaOCl stability compared to PEI and PEI+PSS. • Fibers with open NF characteristics are competitive with commercial nanofiltration membranes.

New approach to develop functionalized polyelectrolyte tube using bacteria as template

AbstractHerein, we propose a new approach consisting of using bacteria as a starting point for the development of new material of interest. Indeed, we are interested in using bacteria as a template. We focus on Escherichia coli which are one of the best studied microorganisms. They are in the micrometer range size and present a tubular shape. We thus use E. coli cells as biotemplate for the design of polyelectrolyte tubes. Indeed, E. coli presents a negatively charged surface (−17 mV) which is then coated by charged polymer via the layer‐by‐layer process. We use chitosan as a polycation and a dextran sulfate as polyanion. First, we evidence the controlled coating of the surface of the bacteria via the measurement of zeta potential (+25 mV to −20 mV) and also by fluorescent microscopy using a fluorescently tagged polysaccharide (fluorescein isothiocyanate‐dextran). Secondly, we remove the bacteria core by using sodium hypochlorite and thus we obtain hollow polyelectrolyte tubes (dimensions of 1.1–1.5 μm × 2.0–6.0 μm). Such bioinspired materials are of major interest for a wide range of applications for the fabrication of polymeric tubes.

Protein loading studies using polyelectrolyte microcapsules

In this study, PSS doped CaCO3 microparticles were used as sacrificial templates for the fabrication of hollow polyelectrolyte microcapsules. The lysozyme loading studies of two systems - chitosan/polymethacrylic acid (CHI/PMA) and chitosan/polystyrene sulfonate (CHI/PSS) microcapsules were carried out. The influences of feed and deposition pH on loading were investigated. Feed pH 8.8 showed more than 97% loading. The study suggests that loading of lysozyme depends upon both feed and deposition pH of the medium. The microcapsules were characterized by Attenuated Total Reflectance Fourier Transform Infrared spectrometer (ATR-FTIR), Scanning Electron Microscope (SEM), Transmission Electron Microscope (TEM) and optical microscope.

A microfluidic strategy to fabricate ultra-thin polyelectrolyte hollow microfibers as 3D cellular carriers.

Microfluidics-based microfibers have been widely used as bottom-up scaffolds for tissue engineering applications. Different forms of microfibers with certain thickness of shell have been developed during the past decade. Ultra-thin microfiber, as a special and promising carrier of cells, was less explored. In this work, by using the interfacial ionic interaction between sodium alginate (NaA) and chitosan (CS), a novel ultra-thin polyelectrolyte hollow microfiber with the diameter of ~200 μm and the shell thickness of 1.3 ± 0.3 μm was fabricated via a microfluidic device for liver tissue engineering. The fluorescence of FITC labeled CS confirmed the inner CS layer of the fabricated microfiber and the SEM results illustrated its ultra-thin characteristic. Although there are only two layers in the ultra-thin polyelectrolyte hollow microfiber, the following cells encapsulation experiments indicated that it could bear cells loading and the hollow space of the microfibers could encapsulate sufficient number of cells for tissue engineering applications. The presence of inner CS layer in the microfiber promoted cell adhesion and ultra-thin shell characteristic facilitated the exchange of nutrient substance and O2 and thus promoted cell proliferation. HepG2 cells encapsulated in the microfibers maintained favorable viability, proliferation ability and hepatic specific functions during 10 days' culture. These results suggest that the established polyelectrolyte microfibers hold great potential applications in the field of liver tissue engineering. We believe this work will lead to the development of innovative methodologies and materials for both cell culture and biomedical application.

Fabrication of polyelectrolyte microspheres using porous manganese carbonate as sacrificial template for drug delivery application

Abstract

Enzymatically Disulfide-Crosslinked Chitosan/Hyaluronic Acid Layer-by-Layer Self-Assembled Microcapsules for Redox-Responsive Controlled Release of Protein.

Disulfide-crosslinked hollow polyelectrolyte microcapsules composed of thiolated chitosan (CS-SH) and hyaluronic acid (HA-SH) were prepared by combining the layer-by-layer (LBL) technique and horseradish peroxidase (HRP)-mediated oxidative cross-linking reaction in mild conditions. FITC-dextran-doped CaCO3 microspheres were used as template core and removed after LBL depositing CS-SH and HA-SH on the surface. The disulfide-crosslinked (CS/HA) microcapsules were readily fabricated by HRP-mediated oxidative coupling of the thiol groups in CS/HA shell layer in the presence of HRP (10 units/mL) and Tyramine hydrochloride (Tyr, 35 mmol/L). The kinetics of enzymatic disulfide-crosslinking reaction was investigated through the real-time monitoring of the consumption of thiol groups by UV absorption spectra. It found that the formation of disulfide linkages by the enzymatic thiol oxidation reaction showed a gradual acceleration. The disulfide-crosslinked CS/HA hydrogel were rapidly formed in gelation time between approximately 17 and 30 min, which were dependent on the concentrations of HRP and Tyr. The disulfide linkages endowed the microcapsule-enhanced physical stability and low permeability under physiological conditions and redox-responsive degradability in reducing environments. The structural stability of disulfide-crosslinked (CS/HA) microcapsules was visualized by confocal laser scanning microscopy in phosphate-buffered saline containing 5.0 mmol/L dithiothreitol (DTT) to evaluate the redox-responsive disassembly process. Redox-responsive controlled release of encapsulated FITC-dextran from the disulfide-crosslinked (CS/HA) microcapsules were obtained. The release profiles of FITC-dextran could be manipulated by controlling the shell thickness and the concentration of DTT. The conformational stability analyses and more than 94% esterase activity of released bovine serum albumin (BSA) from (CS/HA) microcapsules conformed that the structural integrity and bioactivity were well preserved during the encapsulation and release process. The microcapsules exhibited excellent cytocompatibility for HEK 293 cells up to a concentration of 1.0 mg/mL. The microcapsules efficiently delivered loaded FITC-BSA into HeLa cells and released the protein in the reducing cytosol. This study proposed a novel approach for producing disulfide-crosslinked microcarriers for intracellular delivery and redox-responsive controlled release of protein.

Live-Cell Imaging by Confocal Raman and Fluorescence Microscopy Recognizes the Crystal Structure of Calcium Carbonate Particles in HeLa Cells.

Porous calcium carbonate (CaCO3 ) vaterite particles are very attractive templates for the encapsulation of pharmaceuticals and for the construction of hollow polyelectrolyte capsules, sensors, and enzyme-catalyzed reactors. Although CaCO3 is biocompatible and biodegradable, little is known about the intercellular behavior and properties of vaterite particles in the cytoplasm of cells. In this work, the authors combine confocal Raman and fluorescent microscopy for the imaging of porous CaCO3 vaterite particles in HeLa cells to study the uptake and status of the particles inside the cells in real time. Analysis of the fluorescence images shows that the particles penetrated the plasma membrane 3 h after being added to the cell culture and that the internalization of the particles continued up to 48 h. The crystal structure of individual vaterite particles in the cytoplasm of HeLa cells did not obviously change for 144 h. For clusters of particles, however, the authors identify Raman spectroscopic signatures of the stable calcite phase after 72 h of incubation, confirming an ion-exchange mechanism of vaterite transformation to calcite. The results indicate that these imaging approach to examining inorganic particles in living cells may have theranostic applications.

Distribution of PEG-coated hollow polyelectrolyte microcapsules after introduction into the circulatory system and muscles of zebrafish.

ABSTRACTThe use of polyelectrolyte multilayer microcapsules as carriers for fluorescent molecular probes is a prospective technique for monitoring the physiological characteristics of animal vasculature and interstitial environment in vivo. Polyelectrolyte microcapsules have many features that favor their use as implantable carriers of optical sensors, but little information is available on their interactions with complex living tissues, distribution or residence time following different routes of administration in the body of vertebrates. Using the common fish model, the zebrafish Danio rerio, we studied in vivo the distribution of non-biodegradable microcapsules covered with polyethylene glycol (PEG) over time in the adults and evaluated potential side effects of their delivery into the fish bloodstream and muscles. Fluorescent microcapsules administered into the bloodstream and interstitially (in concentrations that were sufficient for visualization and spectral signal recording) both showed negligible acute toxicity to the fishes during three weeks of observation. The distribution pattern of microcapsules delivered into the bloodstream was stable for at least one week, with microcapsules prevalent in capillaries-rich organs. However, after intramuscular injection, the phagocytosis of the microcapsules by immune cells was manifested, indicating considerable immunogenicity of the microcapsules despite PEG coverage. The long-term negative effects of chronic inflammation were also investigated in fish muscles by histological analysis.

One-Step Generation of Salt-Responsive Polyelectrolyte Microcapsules via Surfactant-Organized Nanoscale Interfacial Complexation in Emulsions (SO NICE).

Polyelectrolyte microcapsules are versatile compartments for encapsulation, protection, and controlled/triggered release of active agents. Conventional methods of polyelectrolyte microcapsule preparation require multiple steps or do not allow for efficient encapsulation of active agents in the lumen of the microcapsule. In this work, we present the fabrication of hollow polyelectrolyte microcapsules with a salt-responsive property based on surfactant organized nanoscale interfacial complexation in emulsions (SO NICE). In SO NICE, polyelectrolyte microcapsules are templated by water-in-oil-in-water (W/O/W) double emulsions. One polyelectrolyte is dissolved in the inner water droplet of the W/O/W double emulsions, whereas the second polyelectrolyte is dissolved in the organic phase by hydrophobic ion paring with an oppositely charged hydrophobic surfactant. Interfacial complexation of the two polyelectrolytes generates a few hundred-nanometer thick film at the inner water-oil interface of the W/O/W double emulsions. SO NICE microcapsules can be triggered to release their cargo by increasing the ionic strength of the solution, which is a hallmark of polyelectrolyte-based microcapsules. By enabling dissolution and interfacial complexation of polyelectrolytes in organic solvents, SO NICE widens the pallet of polymers that can be used to generate functional polyelectrolyte microcapsules with high encapsulation efficiency for applications in encapsulation and controlled/triggered release.

Hollow Polyelectrolyte Microcapsules as Advanced Drug Delivery Carriers.

Polyelectrolyte microcapsules based layer-by-layer assembly method have many applications in biomedical field. This review mainly focuses on the recent development of polyelectrolyte microcapsules addressing the potential challenge regarding efficient drug delivery. Firstly, the paper describes the new design criteria of polyelectrolyte microcapsules for advanced functionality, especially stimuli-responsive capsules. Secondly, the surface decoration of capsules is discussed with respect to the requirement of improved biocompatibility and specific targeting. Thirdly, the mutual interaction between capsules and cells such as cell uptake are discussed. Finally, the applications of capsules in vitro and even in vivo are presented.

Highly active antibody-modified magnetic polyelectrolyte capsules

Polyelectrolyte hollow capsules are versatile platforms typically used for encapsulation of a wide variety of macromolecules in their cavity. The polymer shell of these capsules as composed by alternating layers of oppositely charged polyelectrolytes also allows for adding additional functionalities. The properties of the shell can be for example engineered by trapping different nanoparticles in-between the shell layers and/or by attaching bioactive molecules such as antibodies to the outermost layer. Herein, iron oxide NPs were inmobilized into the shell of polyelectrolyte capsules and the outermost layer of the shell was covalently modified with anti peroxidase antibodies. These capsules act as prototype model system, aiming to obtain a microstructure with the potential capability to specifically recognize and separate macromolecules. Due to the magnetic nanoparticles in the capsule shell, the capsules together with the attached target might be extracted by magnetic field gradients. Here we verified this approach by extracting horseradish peroxidase from a solution through magnetic separation with capsules bearing antibodies against horseradish peroxidase. The bioactivity of the capsules and the high degree of specific antibody functionalization were confirmed and quantified through an enzymatic reaction mediated by the extracted horseradish peroxidase.

Highly sensitive electrochemical detection of genomic DNA based on stem loop probes structured for magnetic collection and measurement via metalised hollow polyelectrolyte shells.

We report a highly sensitive method for the electrochemical detection of genomic DNA, based on the employment of two sub-micron oligonucleotide labels - one for magnetic collection and the other for voltammetric detection - and their incorporation onto a stem loop DNA probe. The magnetic label consists of a latex particle of mean diameter 441±6 nm, bearing magnetic Fe3O4 particles and approx. 3.5×10(5) anti-DIG antibodies. The voltammetric label is a hollow polyelectrolyte shell containing approx. 1.0×10(11) Au atoms in the form of well dispersed Au nanoparticles. A DIG tag on one arm of the stem loop enables binding to the magnetic label, while a thiol tag on the other arm enables attachment to the Au nanoparticles. Due to steric hindrance from the two relatively large labels, attachment of both moieties is dependant on target-probe hybridisation straightening the loop. Once attached, sensitive DNA measurement is facilitated by magnetic collection of the DNA into a small volume and by the high quantity of Au atoms available for detection. Using differential pulse anodic stripping voltammetry we calibrated a 30 mer sequence common to 71 strains of Escherichia coli across the concentration range from 0.1 aM to 100 pM with a LOD of 1.8 aM. Three strains of E. coli, BL 21, ATCC8739, O157:H7, when spiked into UHT milk and fermented palm juice, could be detected with LODs of approx. 2-4 CFU mL(-1) in an assay time of approx. 140 min.

Single- and multicompartment hollow polyelectrolyte complex microcapsules by one-step spraying.

Polyelectrolyte complex microcapsules are prepared using a novel template- and surfactant-free method. The microcapsules are produced spontaneously by ultrasonically spraying a solution of complex into a hot water reservoir, which enhances diffusion and relaxation of the polymer. The size and wall thickness of the microcapsules are precisely controlled. Encapsulation of polymers and nanoparticles by mixing them with polyelectrolyte solutions is demonstrated.

Encapsulation of photoactive porphyrinoids in polyelectrolyte hollow microcapsules viewed by fluorescence lifetime imaging microscopy (FLIM)

Fluorescence Lifetime Imaging Microscopy (FLIM) was used to investigate the encapsulation of porphyrinoids in multilayer hollow microcapsules assembled layer by layer with poly(styrene sulfonate) (PSS) and poly(allylamine hydrochloride) (PAH).

Carrier-inside-carrier: polyelectrolyte microcapsules as reservoir for drug-loaded liposomes

Conventional liposomes have a short life-time in blood, unless they are protected by a polymer envelope, most often polyethylene glycol. However, these stabilizing polymers frequently interfere with cellular uptake, impede liposome-membrane fusion and inhibit escape of liposome content from endosomes. To overcome such drawbacks, polymer-based systems as carriers for liposomes are currently developed. Conforming to this approach, we propose a new and convenient method for embedding small size liposomes, 30–100 nm, inside porous calcium carbonate microparticles. These microparticles served as templates for deposition of various polyelectrolytes to form a protective shell. The carbonate particles were then dissolved to yield hollow polyelectrolyte microcapsules. The main advantage of using this method for liposome encapsulation is that carbonate particles can serve as a sacrificial template for deposition of virtually any polyelectrolyte. By carefully choosing the shell composition, bioavailability of the liposomes and of the encapsulated drug can be modulated to respond to biological requirements and to improve drug delivery to the cytoplasm and avoid endosomal escape.

Loading and protection of hydrophilic molecules into liposome-templated polyelectrolyte nanocapsules.

Compartmentalized systems produced via the layer-by-layer (LbL) self-assembly method have been produced by alternatively depositing alginate and chitosan layers onto cores of liposomes. The combination of dynamic light scattering (DLS), ζ potential, and transmission electron microscopy (TEM) techniques provides detailed information on the stability, dimensions, charge, and wall thickness of these polyelectrolyte globules. TEM microphotographs demonstrate the presence of nanocapsules with an average diameter of below 300 nm and with a polyelectrolyte wall thickness of about 20 nm. The possibility of encapsulating and releasing molecules from this type of nanocapsule was demonstrated by loading FITC-dextrans of different molecular weights in the liposome system. The release of the loaded molecules from the nanocapsule was demonstrated after liposome core dissolution. Even at low molecular weight (20 kDa), the nanocapsules appear to be appropriate for prolonged molecule compartmentalization and protection. By means of the Ritger-Peppas model, non-Fickian transport behavior was detected for the diffusion of dextran through the polyelectrolyte wall. Values of the diffusion coefficient were calculated and yield useful information regarding chitosan/alginate hollow nanocapsules as drug-delivery systems. The influence of the pH on the release properties was also considered. The results indicate that vesicle-templated hollow polyelectrolyte nanocapsules show great potential as novel controllable drug-delivery devices for biomedical and biotechnological applications.

PH-Sensitive Fluorescent Hepatocyte-Targeting Multilayer Polyelectrolyte Hollow Microspheres as a Smart Drug Delivery System

Novel multilayer polyelectrolyte hollow microspheres with pH-sensitive fluorescence and hepatocyte-targeting functions were successfully fabricated via a layer-by-layer (LbL) assembly of fluorescein isothiocyanate (FITC)-modified chitosan (CSFITC) and sodium hyaluronate (HA) (as the polycation and polyanion, respectively) on polystyrene sulfonate (PSS) templates with galactosylated chitosan (GC) as the outermost layer; after etching the templates by dialysis, the aim was to use the microspheres to target hepatocytes specifically. TEM analysis revealed that they have a hollow structure with a particle size of about 260 nm, and DLS analysis demonstrated that they have pH and ionic strength dual-responsive characteristics. The hollow microspheres showed pH-sensitive fluorescence at a very low concentration by fluorescent emission spectra. MTT assays revealed that doxorubicin (a water-insoluble anticancer drug)-loaded (CSFITC/HA)4/GC hollow microspheres can specifically target hepatocytes and exhibit favorable cytocompatibility. Three typical model drugs were loaded into the (CSFITC/HA)4/GC hollow microspheres, and their drug-release kinetics in simulated body fluid (SBF) were estimated with different mathematical models. The results demonstrated that the drug-loading mechanism is chemosorption and the primary governing force for drug release is diffusion. Thus, the designed hollow microspheres are expected to be used for the diagnosis and therapy of hepatic cancer.