Hybrid Polyelectrolyte Research Articles

Layer-by-Layer Engineered Superparamagnetic Polyelectrolyte Hybrid Hollow Microspheres With High Magnetic Content as Drug Delivery System

Polyelectrolyte hybrid hollow microspheres with sandwich structure of about 450 nm have been accomplished by layer-by-layer self-assembling of two modified ferroferric oxide nanoparticles, lysine modified ferroferric oxide nanoparticles (Fe3O4-LYs) and citrate modified ferroferric oxide nanoparticles (Fe3O4-CA), as the main assembling materials via electrostatic interaction for the first time. They are superparamagnetic with saturation magnetization of 45.69 emu/g, revealing their high magnetic content of 70%. As drug delivery system, they also exhibited pH-stimuli responsive controlled release of an anticancer drug doxorubicin, following the Fickian diffusion model. Their unique structure and high magnetic content make them good candidate for targeted delivery.

Tumor Imaging: Tumor‐Responsive Fluorescent Light‐up Probe Based on a Gold Nanoparticle/Conjugated Polyelectrolyte Hybrid (Small 10/2014)

A tumor-responsive nanoprobe is reported on page 1967 by B. Liu and co-workers based on a conjugated polyelectrolyte and a gold nanoparticle (AuNP) hybrid is designed to fluoresce in response to the low pH extracellular microenvironment in tumors. AuNPs with positive surface charges are prepared by directly reducing Au salt with sodium borohydride and stabilization by cystamine. A pH-triggered, charge-reversible polymer and a water-soluble cationic conjugated polyelectrolyte (CPE) are sequentially deposited onto the AuNP surface through electrostatic interaction. Under physiological conditions (pH ≈ 7.4), the hybrid probe is almost non-fluorescent due to the quenching of CPE by AuNPs. When exposed to acidic extracellular microenvironments in tumors (pHe ≈ 6.5), the acid-labile amides hydrolyze into primary amines. The generated amine groups result in strong electrostatic repulsion between CPE and AuNPs, leading to recovered probe fluorescence. The fluorescence turnon is further utilized for extracellular acidic tumor microenvironment imaging in vivo, which provides new opportunities for easy tumor imaging and identification.

Tumor‐Responsive Fluorescent Light‐up Probe Based on a Gold Nanoparticle/Conjugated Polyelectrolyte Hybrid

A tumor-responsive nanoprobe based on a conjugated polyelectrolyte and gold nanoparticle (AuNP) hybrid was designed to response to the low pH extracellular microenvironment in tumor with light-up fluorescence. AuNPs with positive surface charges were prepared by direct reducing Au salt with sodium borohydride and stabilized by cystamine. A pH triggered charge-reversible polymer and a water-soluble cationic conjugated polyelectrolyte (CPE) were sequentially deposited onto the AuNP surface through electrostatic interaction. The obtained hybrid probe is monodispersed with an average diameter of 68.3 nm by dynamic light scattering measurement. In physiological conditions (pH ≈ 7.4), the hybrid probe is almost non-fluorescent due to the super-quenching of CPE by AuNPs via energy/charge transfer and efficient exciton migration along the polymer backbone. When exposed to acidic extracellular microenvironments in tumor (pH(e) ≈ 6.5), the acid-labile amides hydrolyze into primary amines. The generated amine groups result in strong electrostatic repulsion between CPE and AuNPs, leading to recovered probe fluorescence. The fluorescence turn-on is further utilized for tumor extracellular acidic microenvironment imaging. In addition, under in vivo conditions, the nanosized hybrid probe exhibits specific accumulation in tumor tissue with light-up fluorescence, which provides new opportunities for easy tumor imaging and identification.

Layer-by-layer assembly of polymersomes and polyelectrolytes on planar surfaces and microsized colloidal particles

Hybrid polyelectrolyte multilayer systems were fabricated on top of planar surfaces and colloidal particles via layer by layer (LbL) assembly of polystyrene sulphonate (PSS) and polybenzyl methacrylate-block-poly(dimethylamino)ethyl methacrylate (PBzMA-b-PDMAEMA) polymersomes. Polymersomes were prepared by self assembly of PBzMA-b-PDMAEMA copolymer, synthesised by group transfer polymerisation. Polymersomes display a diameter of 270nm and a shell thickness of 11nm. Assembly on planar surfaces was followed by means of the Quartz Crystal Microbalance with Dissipation (QCM-D) and Atomic Force Microscopy (AFM). Detailed information on the assembly mechanism and surface topology of the polymersome/polyelectrolyte films was thereby obtained. The assembly of polymersomes and PSS on top of silica particles of 500nm in diameter was confirmed by ζ-potential measurements. Confocal laser scanning microscopy (CLSM), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) revealed that polymersome/PSS coated silica particles increase in total diameter up to 3–5μm. This hints toward the formation of densely packed polymersome layers. In addition, CLSM showed that polymersome/PSS films exhibit a high loading capacity that could potentially be used for encapsulation and delivery of diverse chemical species. These results provide an insight into the formation of multilayered films with compartmentalised hydrophilic/hydrophobic domains and may lead to the successful application of polymersomes in surface-engineered colloidal systems.

Poly(ionic liquid)s-based nanocomposite polyelectrolytes with tunable ionic conductivity prepared via SI-ATRP

In this study, a novel kind of organic–inorganic core–shell SiO2-poly(p-vinylbenzyl) trimethylammonium tetrafluoroborate (SiO2–P[VBTMA][BF4]) nanoparticle was well designed and successfully synthesized via surface-initiated atom transfer radical polymerization (SI-ATRP). Fourier transform infrared spectroscopy (FT-IR), 1H nuclear magnetic resonance (1H NMR), X-ray photoelectron spectroscopy (XPS), dynamic light scattering (DLS) and scanning electron microscopy (SEM) were used to confirm the formation of the core–shell nanoparticles and the surface modification. In order to overcome the challenge of the characterization of the number average molecular weight of poly(ionic liquid)s, “sacrificial initiator” method was used here employing a trimethylsilyl (TMS)-labeled initiator as the NMR marker for integration. In addition, good thermal stability of the new hybrid polyelectrolyte was proved by thermogravimetric analysis. The electrochemical impedance measurements revealed that the room temperature conductivity reached 10−4 S cm−1, which is much higher than that of the pure poly(ionic liquid)s and varies with the amount of the grafted polymer and the test temperature. The X-ray diffraction (XRD) tests further investigated the crystal structure of the nanocomposite and pure P[VBTMA][BF4]. The temperature dependence of ionic conductivity conforms to Arrhenius behavior for both of the nanocomposites and the pure polymer. The results indicated that the SI-ATRP approach provided a simple and versatile route to tune the ionic conductivity of the hybrid nanoparticles by changing the chain length of the grafted polymer, which can be potentially used in a variety of electrochemical devices.

Glucose-sensitive polyelectrolyte nanocapsules based on layer-by-layer technique for protein drug delivery

The glucose-responsive nanocapsules [CS-NAC/p(GAMA-r-AAPBA)] were readily fabricated with modified chitosan (CS-NAC) and random glycopolymer poly(D-gluconamidoethyl methacrylate-r-3-acrylamidophenylboronic acid) p(GAMA-r-AAPBA) as the alternant multilayered polyelectrolyte hybrid shell via layer-by-layer self-assembly after etching the amino functionalized SiO2 spheres by NH4F/HF. The spherical and hollow structure of nanocapsules was confirmed by TEM analysis and there was no clear collapse found after removal of the sacrificial cores. The reversible zeta potential changes of the nanocapsule materials evaluated the reversible glucose sensitivity. Besides, this system demonstrated a good capacity for encapsulation and loading insulin entrapped in nanocapsules as model protein drug. A good biocompatibility of the material was confirmed by the cell viability. In vitro release of insulin experiments revealed that no obvious release was found in acidic condition and the release could be normally conducted at physiological pH. These results implied that it was feasible for nanocapsules to be used in controlled release drug delivery system.

Hybrid polyelectrolytes based on stable sulfonated polynorbornene with higher proton conductivity and lower methanol permeability

We report preparation of hybrid cross-linked proton exchange membranes (PEMs), which are synthesized from sulfonated copoly(norbornene)s bearing sultone pendant (SPBN) and a zwitterionic silica containing sulfonic acid and ammonium groups, 3-[[3-(triethoxysilyl)-propyl]amino]butane-1-sulfonic acid (TPABS), using a sol–gel process. As these membranes are well processed as self-supporting film, they show high stabilities, proton conductivity and low methanol permeability. Reported SPBN/TPABS-50 (50 wt % of TPABS to SPBN in the matrix) shows the best performance with proton conductivity of 6.34 × 10−2 S cm−1, methanol permeability of 3.64 × 10−7 cm2 s−1, ion-exchange capacity value of 1.21 mequiv g−1 and comparable selectivity parameter of 1.74 × 104 S cm−3 s. While the membrane electrode assembly (MEA) is fabricated using the SPBN/TPABS-50 as PEM, the open circuit voltage of SPBN/TPABS-50 at 1.0 M methanol (80 °C) and its power density of the devices are 0.563 V and 50.2 mW cm−2, respectively, though which is lower than that of Nafion117 (124.2 mW cm−2). The new designed cross-linked membranes can thus be a promising candidate to satisfy the requirements of PEMs for direct methanol fuel cells, especially the simple and low cost preparation of the membranes.

Biocompatible Magnetic and Molecular Dual-Targeting Polyelectrolyte Hybrid Hollow Microspheres for Controlled Drug Release

Well-defined biocompatible magnetic and molecular dual-targeting polyelectrolyte hybrid hollow microspheres have been accomplished via the layer-by-layer (LbL) self-assembly technique. The hybrid shell was fabricated by the electrostatic interaction between the polyelectrolyte cation, chitosan (CS), and the hybrid anion, citrate modified ferroferric oxide nanoparticles (Fe3O4-CA), onto the uniform polystyrene sulfonate microsphere templates. Then the magnetic hybrid core/shell composite particles were modified with a linear, functional poly(ethylene glycol) (PEG) monoterminated with a biotargeting molecule (folic acid (FA)). Afterward the dual targeting hybrid hollow microspheres were obtained after etching the templates by dialysis. The dual targeting hybrid hollow microspheres exhibit exciting pH response and stability in high salt-concentration media. Their pH-dependent controlled release of the drug molecule (anticancer drug, doxorubicin (DOX)) was also investigated in different human body fluids. As expected, the cell viability of the HepG2 cells which decreased more rapidly was treated by the FA modified hybrid hollow microspheres rather than the unmodified one in the in vitro study. The dual-targeting hybrid hollow microspheres demonstrate selective killing of the tumor cells. The precise magnetic and molecular targeting properties and pH-dependent controlled release offers promise for cancer treatment.

Ultrathin cellulose film coating of porous alumina membranes for adsorption of superoxide dismutase.

The non-toxic and biocompatible cellulose possesses nonspecific binding properties for many protein molecules. But its abundant inter- and intra-molecular hydrogen bonds induce spontaneous self-assembly of cellulose into a random fibrous morphology and cellulose film coating is usually just available for two-dimensional flat substrates, which severely limits its protein adsorption performance. In this study, direct self-assembly of an ultrathin cellulose film on hybrid polyelectrolyte multilayer pre-coated pore surfaces of an anodic aluminum oxide membrane was achieved through the dissolution and precipitation of cellulose from N-methylmorpholine oxide solution. Each pore channel surface pre-coated with a uniform polyelectrolyte hybrid layer (thickness ∼5.0 nm) was covered by a cellulose film (∼15.0 nm) consisting of dense cellulose nanoparticles with a diameter of 5.5 ± 1.4 nm. The three-dimensional porous structure of the aluminum oxide membrane was well-preserved and micrometre-long flexible nanotubes with an average outer diameter of ∼200 nm were obtained after further aluminum oxide template dissolution treatment in an acidic environment. Moreover, the cellulose film coated pore channel surfaces presented sufficient hydrogen bonds and exhibited a high adsorption capacity rate of ∼1.45 mg m-2 for superoxide dismutase. This facile cellulose deposition approach enabled ultrathin cellulose film coating on three-dimensional structured substrates for enhanced adsorption performance for protein molecules.

Aggregation-Resistant Superparamagnetic Noncovalent Hybrid Multilayer Hollow Microcapsules in High Ionic Strength Media

In order to avoid the aggregation and/or fusion of the polyelectrolyte multilayer hollow microcapsules self-assembled via the noncovalent bonds, superparamagnetic polyelectrolyte hybrid hollow microcapsules surface-modified with polyethylene glycol (PEG) brushes were designed and fabricated. After the layer-by-layer (LbL) self-assembly of chitosan (CS) and citric acid-modified magnetic nanoparticles (Fe3O4–CA) as the polycation and the hybrid anion on the polystyrene sulfonate microsphere (PSS) templates, respectively, the aldehyde group terminated polyethylene glycol-4000 (APEG) was grafted onto the surface of the superparamagnetic polyelectrolyte hybrid multilayer coated template microspheres via the nucleophilic addition between the aldehyde groups of APEG and the amino groups of CS. Then, the modified superparamagnetic polyelectrolyte hybrid hollow microcapsules were obtained after the templates were removed by dialysis. It was found that the surface PEGylation could prevent aggregation among the hollow microcapsules in the media with high salt concentration by dynamic light scattering (DLS), besides the increase in biocompatibility. The technique developed is expected to realize the application of the polyelectrolyte multilayer hollow microcapsules in real physiological environments.

Preparation of Aggregation-Resistant Biocompatible Superparamagnetic Noncovalent Hybrid Multilayer Hollow Microspheres for Controlled Drug Release

Biocompatible superparamagnetic polyelectrolyte hybrid hollow microspheres ((CS/Fe(3)O(4)-CA)(3)-CS-NH-CH(2)-PEG) were successfully prepared by PEGylation of multilayered polyelectrolyte hybrid shell encapsulated polystyrene sulfonate (PSS) microsphere templates fabricated by the layer-by-layer self-assembly of chitosan (CS) and citrate modified ferroferric oxide magnetic nanoparticles (Fe(3)O(4)-CA), after etching the templates by dialysis. Their hollow structure with diameter of about 200 nm was confirmed by TEM analysis. The pH and ionic strength responsive properties were retained after the PEGylation of the hollow microspheres. Furthermore, their biocompatibility and stability against aggregation and fusion in media with high ionic strength were distinctly improved. A typical anti-inflammatory drug, ibuprofen, was used for drug loading, and the release behaviors of ibuprofen in a simulated body fluid (SBF) were studied. The results indicate that the biocompatible superparamagnetic polyelectrolyte hybrid hollow microspheres ((CS/Fe(3)O(4)-CA)(3)-CS-NH-CH(2)-PEG) have a high drug loading capacity and favorable release property for ibuprofen; thus, they are very promising for application in drug delivery.

High performance polymer light-emitting diodes with N-type metal oxide/conjugated polyelectrolyte hybrid charge transport layers

We present an interfacial engineering strategy employing n-type-metal-oxide/conjugated-polyelectrolyte (CPE) hybrid charge-transport layers for highly efficient polymer light-emitting diodes (PLEDs). The hybrid metal-oxide/CPE layer facilitates electron-injection, while blocking hole-transport, and thereby maximizes electron-hole recombination within the emitting layer. A series of metal-oxide/CPE combinations were tested in inverted PLEDs (FTO/metal-oxide/CPE/F8BT/MoO3/Au). Specifically, HfO2/CPE double layer achieved an electroluminescence (EL) efficiency of up to 25.8 cd/A (@ 6.4 V, one of the highest values reported for fluorescent PLEDs).

Preparation and electrochemical properties of gold nanoparticles containing carbon nanotubes-polyelectrolyte multilayer thin films

Multi-walled carbon nanotubes (MWCNT)/polyelectrolyte (PE) hybrid thin films were fabricated by alternatively depositing negatively charged MWCNT and positively charged (diallyldimethylammonium chloride) (PDDA) via layer-by-layer (LbL) assembly technique. The stepwise growth of the multilayer films of MWCNT and PDDA was characterized by UV–vis spectroscopy. Scanning electron microscopy (SEM) images indicated that the MWCNT were uniformly embedded in the film to form a network and the coverage density of MWCNT increased with layer number. Au nanoparticles (NPs) could be further adsorbed onto the film to form PE/MWCNT/Au NPs composite films. The electron transfer behaviour of multilayer films with different compositions were studied by cyclic voltammetry using [Fe(CN) 6] 3−/4− as an electrochemical probe. The results indicated that the incorporation of MWCNT and Au NPs not only greatly improved the electronic conductivity of pure polyelectrolyte films, but also provided excellent electrocatalytic activity towards the oxidation of nitric oxide (NO).

Investigation of tribological behavior of lanthanum hybrid polyelectrolyte molecular deposition films

Poly(allylamine hydrochloride) (PAH) and poly(styrene sulfonic acid) sodium salt (PSS) polyelectrolyte molecular deposition films were prepared on quartz substrate by the layer-by-layer method. Lanthanum was deposited in the polyelectrolyte molecular deposition film, making use of the chemisorption ability of –SO 3 − group of PSS, and heating for 2 h at 120 °C to make the lanthanum element chemically bond with PSS. Atomic force microscopy (AFM), ultraviolet–visible (UV–vis) light spectroscope, X-ray photoelectron spectroscopy (XPS), and contact angle measurements were used to characterize the thin films. The tribological behaviors of the polyelectrolyte molecular deposition film and lanthanum hybrid polyelectrolyte molecular deposition film were evaluated on a micro-tribometer by sliding against a steel ball. Tribological experiments show that the friction coefficient of polyelectrolyte molecular deposition film decreases from 0.19 to 0.08 after the rare-earth (RE) self-assembled in the polyelectrolyte molecular deposition film. The lanthanum hybrid polyelectrolyte molecular deposition films have a longer wear life than that for the pure polyelectrolyte molecular deposition film. It is demonstrated that the lanthanum hybrid polyelectrolyte molecular deposition film exhibits a good wear-resistant property.

Enhanced electrochemistry of nanoparticle-embedded polyelectrolyte films: Interfacial electronic coupling and distance dependence

Factors affecting the electronic communication believed to be responsible for the enhanced solution electrochemistry observed at electrodes modified with hybrid polyelectrolyte–nanoparticle (PE–NP) film assemblies were systematically investigated. Specifically, the faradaic current and voltammetric peak splitting recorded for cyclic voltammetry of ferricyanide redox species (Fe(CN) 6 3−/4−) at films constructed with various architectures of citrate-stabilized gold NPs embedded in polyelectrolyte films composed of poly- l-lysine and poly-S-styrene were used to establish the relative importance of both distance and electronic coupling. Layer-by-layer construction of PE–NP films allowed for the position and density of NPs to be varied within the film to assess electronic coupling between particles (interparticle coupling) as well as at the electrode–film interface. The cumulative results observed at these films suggest that, while distance dependence prevails in nearly every case and interparticle coupling can contribute to facilitating the Fe(CN) 6 3−/4− electrochemistry, interfacial electronic coupling of the PE–NP films is of critical importance and decoupling is easily achieved by disengaging NP–electrode interactions.

An all-solid-state electrochromic device based on NiO/WO 3 complementary structure and solid hybrid polyelectrolyte

An all-solid-state electrochromic (EC) device based on NiO/WO 3 complementary structure and solid polyelectrolyte was manufactured for modulating the optical transmittance. The device consists of WO 3 film as the main electrochromic layer, single-phase hybrid polyelectrolyte as the Li + ion conductor layer, and NiO film as the counter electrochromic layer. Indium tin oxide- (ITO) coated glass was used as substrate and ITO films act as the transparent conductive electrodes. The effective area of the device is 5×5 cm 2. The device showed an optical modulation of 55% at 550 nm and achieved a coloration efficiency of 87 cm 2 C −1. The response time of the device is found to be about 10 s for coloring step and 20 s for bleaching step. The electrochromic mechanism in the NiO/WO 3 complementary structure with Li + ion insertion and extraction was investigated by means of cyclic voltammograms (CV) and X-ray photoelectron spectroscopy (XPS).

Highly Active TiO2/Polyelectrolytes Hybrid Multilayered Hollow Nanofibrous Photocatalyst Prepared from Electrouspun Fibers Using Electrostatic Layer-by-Layer Technique

Compared to conventional film photocatalysts, fiber photocatalyst has a greater surface-to-volume ratio and a 3-D open structure that allows its surface active sites to be accessible for reactants more easily and effectively. However, TiO 2 powder (Degussa P25), by itself, cannot be prepared in the form of fibers, but with the help of a polymer nanofiber, TiO 2 particles can be immobilized in a fibrous network of polyelectrolyte. Here, hybrid multilayered hollow nanofibers (HMHNFs) composed of TiO 2 /polyelectrolyte (PE) have been prepared by a combination of a electrospinning method and layer-by-layer (LBL) technology. The results show that both the average diameter and the wall thickness of the HMHNFs can be well controlled by the template, as well as the number of coating layers. The dried morphology of the obtained HMHNFs is dependent on the inner deposited numbers of the polyelectrolyte layers. When compared with other nanostructured TiO 2 materials, such as commercial TiO 2 nanoparticles (P25, Degussa) and TiO 2 films, the hollow TiO 2 /PE hybrid nanofibers exhibited higher photocatalytic activities.

Palladium–polyelectrolyte hybrid nanoparticles for hydrogen sensor in fuel cells

We prepared palladium–polyelectrolyte hybrid nanoparticles by using a metallization of polyelectrolyte. In this study, we selected polyacrylic acid (PAA) as a polyelectrolyte and reduced the palladium ions on the PAA by using ascorbic acids in order to form a unique spherically shaped mosslike hybrid nanoparticle. Palladium (Pd) can absorb hydrogen to become PdHx, and the storage of hydrogen increases the electrical resistance and volume of Pd materials. The use of this material is attracting growing interest as a reliable, cheap, ultracompact, and safe hydrogen sensor for use in fuel cells. We showed the utilization of the Pd–PAA hybrid nanoparticles as a highly sensitive hydrogen sensor that exhibited a switch response depending on volume expansion in a cyclic atmosphere exchange.

Functionalized Organic−Inorganic Nanostructured N-p-Carboxy Benzyl Chitosan−Silica−PVA Hybrid Polyelectrolyte Complex as Proton Exchange Membrane for DMFC Applications

Chitosan was modified into N-p-carboxy benzyl chitosan (NCBC) by introducing an aromatic ring grafted with carboxylic acid as the proton conducting group. A preparation procedure of highly conductive and stable organic-inorganic nanostructured NCBC-silica-poly(vinyl alcohol) (PVA), proton exchange membrane (PEM) for direct methanol fuel cell (DMFC), by the sol-gel method in aqueous media has been reported. These PEMs were developed by cross-linking and designed to consist of weak proton conducting (-COOH) groups at organic segments and strong proton conducting (-SO3H) groups at inorganic segments to achieve high charge density and stabilities. Cross-linking density and NCBC-silica content in the membrane matrix were systematically optimized to control their nanostructure, thermal, mechanical, and chemical stabilities, as well as proton and fuel transport properties. Developed PEMs were extensively characterized by studying their physicochemical and electrochemical properties under DMFC operating conditions. As these PEMs were well processed as self-supporting film, they showed high stabilities and proton conductivity and low methanol permeability. Moreover, among all synthesized membranes, PCS-3-3 hybrid PEM exhibited quite a high selectivity parameter in comparison to Nafion117 membrane for DMFC applications.

Ion Relaxation Dynamics in a Decoupled Hybrid Polyelectrolyte

On the hop: Conductivity spectra indicate a single ion-transport mechanism that is governed by ion hopping dynamics and is responsible for the nearly constant loss behavior. These contributions to ac conductivity are observed in a hybrid polyelectrolyte, whose ion-transport mechanism is governed by ion hopping above the glass transition temperature (see picture).