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Carfilzomib (CFZ) is a second-generation proteasome inhibitor showing great efficacy in multiple myeloma treatment, yet its clinical applications for other diseases such as solid cancers are limited due to low aqueous solubility and poor biostability. Ternary polypeptide nanoparticles (tPNPs) are drug carriers that we previously reported to overcome these pharmaceutical limitations by entrapping CFZ in the core of the nanoparticles and protecting the drugs from degradation in biological media. However, preclinical studies revealed that tPNPs would require further improvement in particle stability to suppress initial burst drug release and thus achieve prolonged inhibition of proteasome activity with CFZ against tumor cells in vivo. In this study, CFZ-loaded tPNPs are stabilized by polycations which have varying pKa values and thus differently modulate nanoparticle stability in response to solution pH. Through polyion complexation, the polycations appeared to stabilize the core of tPNPs entrapping CFZ-cyclodextrin inclusion complexes while allowing for uniform particle size before and after freeze drying. Interestingly, CFZ-loaded tPNPs (CFZ/tPNPs) showed pH-dependent drug release kinetics, which accelerated CFZ release as solution acidity increased (pH < 6) without compromising particle stability at the physiological condition (pH 7.4). In vitro cytotoxicity and proteasome activity assays confirmed that tPNPs stabilized with cationic polymers improved bioactivity of CFZ against CFZ-resistant cancer cells, which would be greatly beneficial in combination with pH-dependent drug release for treatment of solid cancers with drug resistance and tumor microenvironment acidosis by using CFZ and other proteasome inhibitors. [ABSTRACT FROM AUTHOR]

Functionalized mesoporous silica particles offer excellent chemical and morphological properties, making them ideal adsorbents or drug carriers. However, their synthesis involves several energy- and resource-intensive steps, resulting in high economic and environmental costs. In this study, we report a strategy for the direct design of mesoporous silica with ordered mesopores densely functionalized by polyacid chains. The aqueous process relies on polyion complex micelles acting as pH-responsive multifunctional agents. They are first associated to direct the mesostructure of silica, and are then dissociated by a change in pH to reveal the material's mesoporosity and yield functional pores. Ordered mesoporous particles with controlled structure and particle size were obtained, showing dense functionalization of up to 2.1 mmol.g SiO2 −1 of carboxylic acid functions, which were fully accessible to ionic exchange in aqueous solution. These highly functionalized materials were then evaluated as reversible adsorbents for the removal of a cationic dye (auramine O). The results revealed high dye uptakes, from 130 to 237 mg.g SiO2 −1, which were up to 193 % higher than those achieved with non-functional calcined mesoporous silica particles. These uptakes correlated with the mesoporous volume of the materials, with an average density of around one auramine molecule per nm3 of pore. In addition, the materials exhibited excellent dye adsorption/desorption cyclability by pH stimuli in aqueous solutions under mild conditions, with an average desorption efficiency of 96 % in just 30 min. These results therefore represent an attractive strategy for the design of efficient and sustainable adsorbents for water purification. [Display omitted] • Eco design of ordered mesoporous silica functionalized with poly(acrylic acid) chains. • Direct formation of functionalized mesopores in one pot and two steps. • Highly accessible acid functions are located in hexagonal and cubic mesostructures. • Particle size is controlled by steric stabilization of the surface. • High cationic dye uptake in water, excellent cyclability in response to pH stimuli. [ABSTRACT FROM AUTHOR]

[Display omitted] • Carboxylated trithiocarbonate mediates RAFT polymerization of a bisphosphonic acrylate. • Two RAFT methodologies lead to phosphonated double hydrophilic block copolymers. • DHBCs interact with lanthanide ions (Gd, Eu) to form polyionic complexes. • Bisphosphonated polyionic complexes enhance the stability of MRI contrast agents. The synthesis of double hydrophilic block copolymers (DHBCs) with one block containing bisphosphonic acid groups was performed by aqueous RAFT polymerization with two approaches, either starting from a PEO-based macro-chain transfer agent (macro-CTA) or by chain extension of a RAFT-capped bisphosphonic acrylate homopolymer with oligo(ethylene glycol) methyl ether acrylate (OEGA). By complexation with gadolinium and europium ions, these polymers are prone to form hybrid polyionic complexes (HPICs) as evidenced by mono- and multi-angle DLS, TEM and luminescence measurements. The obtained HPICs showed better chemical stability at low pH values compared to previously reported counterparts based on carboxylic and monophosphonic acid groups (i.e., PEO- b -PAA and PEO- b -PVPA respectively). Due to their high relaxivity values, the proposed HPICs show potential as contrast agents for magnetic resonance imaging (MRI). [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Heparin is a versatile building block to construct biomedical polyion complex(PIC). • PIC's morphologies are tuned from micelle to vesicle by heparin content. • The PIC drug carrier with high DLC is prepared by very simple manipulation. • pH sensitive release is spontaneously endowed without additional modification. • Heparin PIC drug carrier has significant cytotoxicity against tumor cell in vitro. Abstract Heparin as negative polysaccharide is a universal building block to form polyion complex with different cationic counterparts. In this paper, three different cations, including chitosan, benzyldodecyldimethyl ammonium bromide and doxorubicin hydrochloride, were used to prepare heparin-based polyion complexes (HPICs). Their morphologies could be tuned by heparin content in HPIC, and they also showed pH-sensitive decomposition. Doxorubicin was further encapsulated into micelle and vesicle carrier made from heparin-benzyldodecyl dimethyl ammonium bromide PIC, whereas heparin-doxorubicin PIC could be directly used as drug carrier. In vitro drug release proved the drug carriers exhibit obvious pH sensitive release behaviour. Cytotoxicity indicated the drug carrier possessed significant cytotoxicity to tumor cells. The cell uptake observed by CLSM showed the carrier was able to deliver antitumor drug into tumor cell's nucleus. Consequently, these results showed the promising potential of HPIC in drug carrier application. [ABSTRACT FROM AUTHOR]

Abstract Cancer stem-like cells (CSCs) treatment is a plausible strategy for enhanced cancer therapy. Here we report a glucose-installed sub-50-nm nanocarrier for the targeted delivery of small interfering RNA (siRNA) to CSCs through selective recognition of the glucose ligand to the glucose transporter 1 (GLUT1) overexpressed on the CSC surface. The siRNA nanocarrier was constructed via a two-step assembling process. First, a glucose-installed poly(ethylene glycol)- block -poly(l -lysine) modified with lipoic acid (LA) at the ω-end (Glu-PEG-PLL-LA) was associated with a single siRNA to form a unimer polyion complex (uPIC). Second, a 20 nm gold nanoparticle (AuNP) was decorated with ~65 uPICs through Au S bonding. The glucose-installed targeted nanoparticles (Glu-NPs) exhibited higher cellular uptake of siRNA payloads in a spheroid breast cancer (MBA-MB-231) cell culture compared with glucose-unconjugated control nanoparticles (MeO-NPs). Notably, the Glu-NPs became more efficiently internalized into the CSC fraction, which was defined by aldehyde dehydrogenase (ALDH) activity assay, than the other fractions, probably due to the higher GLUT1 expression level on the CSCs. The Glu-NPs elicited significantly enhanced gene silencing in a CSC-rich orthotopic MDA-MB-231 tumor tissue following systemic administration to tumor-bearing mice. Ultimately, the repeated administrations of polo-like kinase 1 (PLK1) siRNA-loaded Glu-NPs significantly suppressed the growth of orthotopic MDA-MB-231 tumors. These results demonstrate that Glu-NP is a promising nanocarrier design for CSC-targeted cancer treatment. Graphical abstract Unlabelled Image Highlights • Glucose-installed nanoparticle (Glu-NP) was made for cancer stem cell-targeted siRNA delivery. • Glu-NP was made by conjugating unimer polyion complexes on Au nanoparticle. • Enhanced cellular uptake of Glu-NP was observed in cancer stem cells in spheroid culture. • Glu-NP loaded with PLK1 siRNA suppressed growth of orthotopic breast tumor model. [ABSTRACT FROM AUTHOR]

In this work, a tight polyethersulfone (PES) -based ultrafiltration (UF) membrane was fabricated to separate dye and salt of textile wastewater via a novel polyion complex assisted phase inversion method in one step. Thereinto, sulfonated polysulfone (SPSF) and poly-(diallyl dimethylammonium chloride) (PDADMAC) were added into the PES dope and coagulation bath, respectively. During the phase inversion process of the precast PES/SPSF film, polycation PDADMAC could assemble with anionic SPSF and facilitate SPSF enrichment on membrane surface, forming a dense barrier layer via the electrostatic interaction between quaternary ammonium and sulfonate groups. Morphology, chemical composition, surface charges and pore size analysis characterized via SEM, FTIR, XPS, Zeta potential and Dextran filtration experiment, respectively, testified that a nonporous skin layer comprising of polyion complex and enriched SPSF was successfully constructed on the top of the PES matrix with an effective pore radius of 1.44 nm, which is smaller than that of the reference membrane prepared without using polyion complex assisted phase inversion (2.74 nm). This resultant membrane exhibited a high pure water permeance of 94 LMH/bar. When it was utilized to separate a dye/salt mixture of 100 ppm Congo red (CR) and 2 g/L Na 2 SO 4 at 1 bar, the rejection of CR could reach 99.7%, alongside a very low Na 2 SO 4 rejection of 8.4%, while the water permeance of dye solution maintained 61 LMH/bar. In addition, the membrane also possessed excellent stability in the pH range of 1–13 due to the strong electrostatic interaction between SPSF and PDADMAC and long-term operation stability, demonstrating its application potential in textile wastewater treatment. [Display omitted] • Tight UF membranes were prepared via polyion complex assisted phase inversion. • The assembly between SPSF and PDADMAC made a thin and nonporous skin layer. • The membrane exhibited 99.7% and 8.4% of Congo red and Na 2 SO 4 rejections, respectively, alongside 61 LMH/bar water permeance. • The separation performance can maintain in the pH range of 1–13 and 12-h stability testing. [ABSTRACT FROM AUTHOR]

For high-valued application of natural DNA as raw materials, we prepared nanocarriers by using salmon sperm DNA and chitosan to encapsulate water-insoluble bioactives. Here, water dispersible astaxanthin/DNA/chitosan nano-aggregates (ADC-NAs) were prepared by co-assemble evaporation method. The key point for preparing well formed ADC-NAs was specifically discussed. The resultant ADC-NAs were spherical with 100–300 nm diameter measured by dynamic light scattering (DLS) and transmission electron microscopy (TEM), and their homogeneous dispersions were sufficiently stable at room temperature. One important feature of these nanocarriers is enormously high loading amount of cargo (about 40 wt%). According to the UV–Vis spectra of the nanosuspension, we deduced that astaxanthin was encapsulated as uniquely structured J-aggregates. Fourier transform infra-red (FTIR) spectroscopy proved fabrication was successfully and astaxanthin was embedding in DNA/chitosan nanocarriers. Cytotoxicity was examined in vitro using cell culture in L929 cell lines. When necessary, these nano-aggregates can be degraded by DNase I. Homogeneous dispersions of other non-charged guest molecules are also prepared by using DNA/chitosan nanocarriers. These dispersions are cheaply and easily obtainable from naturally occurring DNA and chitosan, and should be useful for versatile applications. [ABSTRACT FROM AUTHOR]

Herein, we report the fabrication of a polyion complex hydrogel from two oppositely charged derivatives of cellulose nanofibrils (CNF). CNF was produced from dissolving pulp through subsequent periodate oxidation, chemical modification, and microfluidization. Three different durations for periodate oxidation (30 min, 120 min, and 180 min) resulted in three different aldehyde contents. Further, two types of chemical modifications were introduced to react with the resulting aldehydes: chlorite oxidation to yield anionic CNF with carboxylic acid groups (DCC) and imination with Girard’s reagent T to yield cationic CNF containing quaternary ammonium groups (CDAC). Functional group contents were assessed using conductometric titration and elemental analysis, while nanofibril morphologies were assessed using atomic force microscopy (AFM). Longer durations of periodate oxidation did not yield different width profile but was found to decrease fibril length. The formation of self-standing hydrogel through mixing of DCC and CDAC dispersions was investigated. Oscillatory rheology was performed to assess the relative strengths of different gels. Self-standing hydrogels were obtained from mixture of DCC180 and CDAC180 dispersions in acetate buffer at pH 4 and 5 at a low concentration of 0.5% w/w that displayed approximately 10-fold increase in storage and loss moduli compared to those of the individual dispersions. Self-standing gels containing doxorubicin (an anticancer drug) displayed pH-responsive release profiles. At physiological pH 7.4, approximately 65% of doxorubicin was retained past a burst release regime, while complete release was observed within 5 days at pH 4. Biocompatibility of DCC180, CDAC180, and their mixture were investigated through quantification of the metabolic activity of NIH3T3 cells in vitro . No significant cytotoxicity was observed at concentrations up to 900 µg/mL. In short, the nanocellulose-based polyion complex hydrogels obtained in this study are promising nature-derived materials for biomedical applications. Statement of Significance We demonstrate that polyion complex can be formed between two cellulose nanofibrils containing complementary charges. To the best of our knowledge, this is the first time that polyion complex formation between complementarily-modified cellulose nanofibrils has been reported, and the results may lead to new ideas on applications of the very promising nanocellulosic materials. The polyion complex helps form a self-standing network that is demonstrated to provide controlled and pH-responsive release of doxorubicin. Particularly, the report explores the connection between the physical properties of functionalizable nanocellulosic materials and their potential biomedical applications. Thus, the study encompasses several broad fields of materials science and engineering, chemistry, and biomedical science that we believe is in line with the readers’ interests. [ABSTRACT FROM AUTHOR]

The high affinity of positively charged nanoparticles to biological interfaces makes them easily taken up by tumor cells but limits their tumor permeation due to non-specific electrostatic interactions. In this study, polyion complex coated nanoparticles with different charge reversal profiles were developed to study the influence of charge reversal profile on tumor penetration. The system was constructed by polyion complex coating using micelles composed of poly (lysine)- b -polycaprolactone (PLys- b -PCL) as the cationic core and poly (glutamic acid)- g - methoxyl poly (ethylene glycol) (PGlu- g -mPEG) as the anionic coating material. Manipulation of charge reversal profile was achieved by controlling the polymer chain entanglement and electrostatic interaction in the polyion complex layer through glutaraldehyde-induced shell-crosslinking. The delayed charge reversal nanoparticles (CTCL30) could maintain negatively charged in pH 6.5 PBS for at least 2 h and exhibit pH-responsive cytotoxicity and cellular uptake in an extended time scale. Compared with a faster charge reversal counterpart (CTCL70) with similar pharmacokinetic profile, CTCL30 showed deeper penetration, higher in vivo tumor cell uptake and stronger antitumor activity in vivo (tumor inhibition rate: 72.3% vs 60.2%, compared with CTCL70). These results indicate that the delayed charge reversal strategy could improve therapeutic effect via facilitating tumor penetration. Statement of Significance Here, the high tumor penetration capability of PEG-coated nanoparticles and the high cellular uptake of cationic nanoparticles were combined by a delayed charge reversal drug delivery system. This drug delivery system was composed of a drug-loading cationic inner core and a polyion complex coating. Manipulation of charge reversal profile was realized by varying the crosslinking degree of the shell of the cationic inner core, through which changed the strength of the polyion complex layer. Nanoparticles with delayed charge reversal profile exhibited improved tumor penetration, in vivo tumor cell uptake and in vivo tumor growth inhibition effect although they have similar pharmacokinetic and biodistribution behaviors with their instant charge reversal counterpart. [ABSTRACT FROM AUTHOR]

Nonconventional stimuli-responsive luminescent polymers without aromatic units have garnered considerable attention. In this study, luminescent ampholytic block copolymer (BCP) and random copolymer (RCP) consisting of nonconjugated vinyl amine (VAm) and N -acryloyl-L-threonine (AThrOH) were synthesized by reversible addition-fragmentation chain transfer (RAFT) polymerization and subsequent deprotection. The ampholytic BCP and RCP display concentration-enhanced emissions, which are apparently higher than those of the VAm homopolymer and polyion complex, and wavelength-dependent emissions, thus validating clusterization-triggered emission (CTE). The intrinsic photoluminescence properties of the primary amine-containing ampholytic copolymers and corresponding polyion complexes were investigated in aqueous solution in response to the change in pH. Two noncovalent interactions, which involve electrostatic interactions between cationic VAm and anionic AThrOH units and hydrogen bonds (e.g., the amino group in VAm/hydroxyl and amide groups in AThrOH), contribute to the achievement of unique self-assembled structures and stimuli-responsive and fluorescent properties of VAm-containing BCP and RCP, which were verified by dynamic light scattering, circular dichroism, and fluorescence measurements. The ability of the copolymers to form clusterized states of the VAm unit can be governed by the comonomer sequence and external stimuli (e.g., pH change, the addition of salt and urea), leading to the manipulation of the assembled structures with CTE features. [Display omitted] • Luminescent ampholytic block and random copolymers without aromatic units were developed. • Copolymers consisting of vinyl amine (VAm) and N -acryloyl-L-threonine were synthesized by RAFT polymerization. • The ampholytic copolymers exhibited concentration-enhanced emissions and wavelength-dependent emissions. • Unique assembled structures and VAm-based clusterization-triggered emission (CTE) were confirmed. • The comonomer sequence and external stimuli led to the manipulation of the assembled structures with CTE features. [ABSTRACT FROM AUTHOR]

The rapid developments of tough hydrogels have promoted the applications of this kind of soft materials in loading bearing systems. However, tough gels usually have poor processibility, which is crucial for the construction of complex structures with gels. In this paper, we demonstrate the processing of tough polyion complex (PIC) hydrogels by simple compression moulding or extruding, which relies on the distinct strength of ionic bonds during and after the processing. The PIC precipitates formed by mixing the solutions of polycation and polyanion, poly(3-(methacryloylamino)propyl-trimethylammonium chloride) and poly(sodium p-styrenesulfonate), are plasticized by saline solution with selected concentration. These raw materials, initially weak and viscoelastic, are easily processed into different shapes. After swelling the as-prepared gels in water to dialyze out the salt and counterions of PIC, tough equilibrated gels are obtained with the imposed shapes during processing. These gels with 50–70 wt% water show good mechanical properties, with tensile fracture stress, fracture strain and tearing fracture energy being 3.7 MPa, 700% and 8 × 10 3 J/m 2 , respectively. These mechanical properties can be effectively tailored by tuning the charge ratio of PIC. However, the concentration of saline water has negligible influence on the mechanical properties of final equilibrated gels. The resultant PIC gels also exhibit stimuli-triggered healing properties owing to the dynamic and reversible nature of the ionic bonds. This study should promote the applications of tough PIC gels in structural elements of soft actuators and synthetic tissues. [ABSTRACT FROM AUTHOR]

The aim of the present study was to evaluate a library of poly- l -lysine (PLL)-graft (g)-polyethylene glycol (PEG) copolymers for the ability to encapsulate effectively a model protein, bovine serum albumin (BSA), and to characterize the stability and protein function of the resulting nanoparticle. A library of nine grafted copolymers was produced by varying PLL molecular weight and PEG grafting ratio. Electrostatic self-assembly of the protein and the grafted copolymer drove encapsulation. The formation of protein/polymer nanoparticles with a core/shell structure was confirmed using PAGE, dynamic light scattering, and electron microscopy. Encapsulation of the BSA into nanoparticles was strongly dependent on the copolymer-to-protein mass ratio, PEG grafting ratio, and PLL molecular weight. A copolymer-to-protein mass ratio of 7:1 and higher was generally required for high levels of encapsulation, and under these conditions, no loss of protein activity was observed. Copolymer characteristics also influenced nanoparticle resistance to polyanions and protease degradation. The results indicate that a copolymer of 15–30 kDa PLL, with a PEG grafting ratio of 10:1, is most promising for protein delivery. [ABSTRACT FROM AUTHOR]

A polymer film composed of a mixture of chitosan (Ch) and carboxymethyl cellulose sodium salt (CMC) nanofibers was deposited on a glass surface. The thin film of the Ch–CMC mixture obtained was stable, and fibroblast adhesion to the film was lowest when the weight ratio of Ch to CMC was 4:6. The ζ-potential and contact angle of the mixture film indicated that a polyion complex of Ch and CMC was formed. The mechanical strength of the film composed of Ch–CMC nanofiber complexes was much higher than that of the film composed of Ch–water-soluble CMC complexes (non-nanofiber), likely because the entanglement of nanofibers was enhanced by electrostatic attractions. These results indicate that the charge-neutralized nanofiber film was highly effective in suppressing cell adhesion and therefore is a promising material for biomedical applications. [ABSTRACT FROM AUTHOR]

Humic substances (HS) coexisting with colloidal particles are inevitable in water bodies. Since the cationic flocculant used for flocculation treatment in such water bodies interacts electrostatically with HS and colloidal particles, the efficiency of the flocculant tends to be lower than in water bodies containing only colloidal particles. The colloidal flocculation mechanism by polycation with low charge density is dominated by bridging effects rather than charge neutralization effects. Furthermore, the polyionic complex formation of low charge density polycations with HS is not stoichiometric, based on the oppositely charged groups. Therefore, it was unclear how HS affects the flocculation of colloidal particles by polycation with low charge density. In this study, the effects of two naturally occurring HS and two synthetic polyanions on the flocculation behavior of negatively charged polystyrene latex (PSL) particles induced by polycationic flocculant with low charge density (4 %) were investigated under standardized mixed fluid conditions. Considering the flocculation inhibition effect in terms of the molar concentration ratio of flocculant-derived cations to polyanion-derived anions, it was found that polyanions less inhibit the flocculation of PSL particles by flocculant with low charge density compared to flocculant with high charge density. The relationship between the degree of inhibition of flocculation and the affinity of polyanions for polycations obtained from electrophoretic mobility experiments was verified, and the effectiveness of using low charge density polycations as particle flocculants in water bodies containing particles and HS was discussed. [Display omitted] • Polycationic flocculants were used to flocculate anionic colloidal particles. • Colloidal flocculation is inhibited by synthetic and naturally occurring polyanions. • Flocculation inhibition is due to the interaction between flocculant and polyanion. • Flocculation inhibition was suppressed by polycation with lower charge density. [ABSTRACT FROM AUTHOR]

Free-standing films of natural polysaccharides were prepared using hot press techniques. Polyion complexes (PICs) made of acidic polysaccharides such as chondroitin sulfate C and chitosan were formed into thin films by hot pressing. The times needed to conduct the process from PIC formation using polysaccharide solutions of two kinds to obtaining films were 30 min or less under appropriate conditions. The resulting films swelled in distilled water to some degree but were not dissolved despite being made of water-soluble polysaccharides. Contact angle measurements supported dense surface structure of the films because of the effects of hot pressing. The films had sufficient mechanical properties to be used as structural materials. Polysaccharide species and film preparation processes affected some film properties. [ABSTRACT FROM AUTHOR]

Ordered assembly of imogolite clay nanotubes was achieved by the spatiotemporal regulation of imogolite complex formation using an organic polyelectrolyte. In a confined reaction space, imogolites formed assemblies with anisotropic birefringence and distinct optical texture under uni-directional diffusion. In assemblies with anisotropic birefringence, imogolite nanotubes uniformly aligned along the longitudinal axis of the assemblies. The ordered structure of imogolites drastically changed with the size of the reaction space and the concentration of components that control a number of nuclei in the assembly. The perfectly rigid rod-like nature of imogolite clay nanotubes induces their ordered alignment. [ABSTRACT FROM AUTHOR]

An amperometric urea biosensor based on urease and metal catalysts (Pt and Rh) has been synthesized on a multiwalled carbon nanotube (MWCNT)-modified ITO glass. A sequential coating of the metal catalysts and urease over the surface of the MWCNT-modified ITO glass was adopted for the electrode preparation by entrapment with a polyion complex (PIC). The activity of the immobilized enzyme for urea hydrolysis and the metal catalysts for the electrochemical oxidation of the ammonia generated during the enzymatic reaction were investigated. The electrochemical performance of the bioelectrode was characterized by a cyclic voltammetry technique. The sensor exhibited a linear amperometric response to urea concentration ranging from 0.05 mM to 20 mM, with a linear correlation coefficient of 0.995. A sensitivity of 1.7 μA mM −1 cm −2 and a response time of approximately 10 s were achieved for the hybrid electrode. The biosensor retained half of its initial activity after 20 days of storage under ambient conditions. The urea sensor employing an enzyme and metal catalysts exhibited excellent electroactivity and sensor efficiency. [ABSTRACT FROM AUTHOR]

Cationic flocculants with varying branching structure sometimes exert dramatically different flocculating abilities on oppositely charged particles. However, their flocculation mechanisms and performances under aqueous conditions in the presence of oppositely charged colloidal particles and polyanions, which commonly exist in natural systems, have not yet been fully elucidated. In this work, three cationic flocculants with different branches per molecule and similar charge densities were used to flocculate negatively charged colloidal particles coexisting with synthetic and naturally occurring polyanions. The electrophoretic mobility of the polymer-coated particles revealed that the branched flocculants required a higher optimum dosage than the linear ones. Under all tested conditions, flocculation was remarkably enhanced by increasing the number of branches in the flocculant. Electrophoretic titrations showed that the interactions between the flocculants and the polyanions to form a polyion complex (PIC) were mainly driven by electrostatic attractions. Hence, the number of branches had no significant effect on PIC formation. These results suggest that unlike the PIC formed by flexible linear flocculants that adopt a flat conformation upon adsorption onto the particle surface, the rigid branched-polyanion PIC tends to retain its shape. This effect is due to the presence of branches that are less prone to undergo relaxation. As a result, a thick adsorbed layer was formed on the particle surface, which improved the effective collision between particles and facilitated bridging flocculation. [Display omitted] • Three cationic flocculants were used to flocculate negatively charged colloidal particles. • These particles coexisted with synthetic and naturally occurring polyanions. • Flocculation was enhanced by increasing the degree of flocculant branching. • A thick adsorbed layer was formed on the particle surface. • This promoted collisions between particles and facilitated bridging flocculation. [ABSTRACT FROM AUTHOR]

Polyion complex (PIC) layers are formed via self-assemble ion pairing by alternately placing polycation/polyanion solutions on platinum electrodes. Their molecular sieving behavior for electrochemically reactive species through the layers is examined by electrochemical methods. Different molecular-sieve sizes are achieved by the selection of polycations with different intramolecular distances of neighboring cationic groups. Amperometric glucose sensing electrodes are fabricated by immobilizing glucose oxidase in a PIC double-layer. The proper double-layer configuration is efficient to improve the glucose response, blocking interferents due to the molecular sieving effect. [ABSTRACT FROM AUTHOR]

Natural polysaccharides are promising candidates for the component of polymer materials for sustainable societies. Here, the preparation of composite films using high- and low-molecular weight (MW) of hyaluronic acid (H-HYA and L-HYA), carboxymethylated HYA (CM-HYA), and high- and low-MW of chitosan (H–CHI and L-CHI) was performed to clarify the effects of the polysaccharide species on formability, mechanical properties, and water-responsive properties of the resulting films. The films prepared using CM-HYA and H–CHI (CM-HYA/H–CHI films) exhibited the highest maximum stress due to more electrostatic interactions between COO− in CM-HYA and NH 3 + in H–CHI. Swelling ratio of CM-HYA/H–CHI films was the lowest both in water and phosphate buffer saline (PBS). Meanwhile, CM-HYA/H–CHI films exhibited the highest moisture absorption ratio and moisture retention capacities, indicating water absorption ability of CM-HYA could be maintained even in the film state. Accordingly, CM-HYA/H–CHI films may be advantageous for applications such as moisture-retaining sheets and biomaterials. [Display omitted] • Composite films with hyaluronic acid and chitosan were successfully prepared. • Effects of chemical species on these film properties are discussed. • Carboxymethylated hyaluronic acid (CM-HYA) improved the mechanical properties. • CM-HYA provided the highest moisture absorption ratio and retention capacity. • The composite films may become a candidate for moisturizing sheets. [ABSTRACT FROM AUTHOR]

Abstract: Oppositely charged polyelectrolytes can be used to form various types of self-assembled structures directed by multivalent ionic interactions. The supramolecular architectures that result are often referred to as polyion complexes (PICs). Synthetic polyion complexes are exciting candidates for biomedical applications. Their self-assembly capabilities give rise to hierarchical mesoscopic platforms such as micelles, membranes, and capsules through simple mixing processes. These complexes are also ideal candidates for the transport and delivery of biological agents since biomolecules, such as DNA and proteins can be easily incorporated through ionic interactions. PICs have therefore found use in drug delivery, diagnostics, gene therapy, biosensors and microreactors. In this paper, we briefly review examples of polymeric supramolecular assemblies based on multivalent ionic interactions for biomedical applications. [Copyright &y& Elsevier]

Abstract: Reactive oxygen species (ROS) scavengers have not been widely used for treatment of local inflammatory reactions such as arthritis and periodontal disease because they are rapidly eliminated from the inflamed site, which results in a low therapeutic effect. Therefore, to enhance the local retention time of ROS scavengers, we developed a redox-active injectable gel (RIG) system by using poly[4-(2,2,6,6-tetramethylpiperidine-N-oxyl)aminomethylstyrene]-b-poly(ethylene glycol)-b-poly[4-(2,2,6,6-tetramethylpiperidine-N-oxyl)aminomethylstyrene] (PMNT-PEG-PMNT) triblock copolymer, which possesses ROS scavenging nitroxide radicals as side chains of the PMNT segment. Cationic PMNT segment in PMNT-PEG-PMNT forms polyion complexes with anionic poly(acrylic acid) (PAAc) to form a flower-like micelle (ca. 79nm), which exhibits in situ thermo-irreversible gelation under physiological conditions. We confirmed the prolonged site-specific retention time of RIG by performing in vivo noninvasive electron spin resonance imaging and quantitative evaluation. In contrast to low-molecular-weight nitroxide radical compounds that disappeared from injection sites in less than 1h after subcutaneous injection, 40% of the RIG remained even at 3days. We also found that RIG inhibits neutrophil infiltration and cytokine production, which leads to suppression of hyperalgesia. These findings indicate the potential of RIG as an innovative approach for treatment of local inflammation. [Copyright &y& Elsevier]

Abstract: Janus-like co-assemblies are expected if non-centrosymmetric host macromolecules are used as precursors. As a natural choice, bis-hydrophilic ionic/non-ionic macromolecules can be complexed with linear homopolyelectrolytes, generating interpolyelectrolyte complexes (IPECs). At the same time, complexation-induced aggregation could result in centrosymmetric species, thereby masking the original non-centrosymmetric character of the IPECs. Thus, water-soluble IPECs would possess Janus-like character if their particles would contain only one non-centrosymmetric host in a co-assembled entity. This goal can be achieved by using miktoarm stars, as star-shaped polyelectrolytes provide higher tendency toward the formation of molecularly-dispersed IPECs. Therefore, water-soluble IPECs with different charge-to-charge ratios were prepared. An excess of miktoarm stars possessing ∼3 polycation arms (quaternized poly(dimethylaminoethyl methacrylate) PDMAEMAQ) and 1 poly(ethylene oxide) PEO arm was mixed with poly(styrene sulfonate) PSS. Then, sedimentation velocity analysis was performed by help of Analytical Ultracentrifugation (AUC). These measurements were supplemented by dynamic light scattering, density measurements and 2D NOESY NMR to determine the molar mass of the co-assembled structures and to learn about the internal structure. As shown by AUC, the IPECs consist of one star per co-assembled structure, when having excess star as host. At the same time, the non-centrosymmetric character of miktoarm stars is kept, leading to Janus-like IPECs. [Copyright &y& Elsevier]

Abstract: Recently, colloidal carrier systems have been receiving much attention in the field of drug targeting because of their high loading capacity for drugs as well as their unique disposition characteristics in the body. This paper highlights the utility of polymeric micelles formed through the multimolecular assembly of block copolymers as novel core–shell typed colloidal carriers for drug and gene targeting. The process of micellization in aqueous milieu is described in detail based on differences in the driving force of core segregation, including hydrophobic interaction, electrostatic interaction, metal complexation, and hydrogen bonding of constituent block copolymers. The segregated core embedded in the hydrophilic palisade is shown to function as a reservoir for genes, enzymes, and a variety of drugs with diverse characteristics. Functionalization of the outer surface of the polymeric micelle to modify its physicochemical and biological properties is reviewed from the standpoint of designing micellar carrier systems for receptor-mediated drug delivery. Further, the distribution of polymeric micelles is described to demonstrate their long-circulating characteristics and significant tumor accumulation, emphasizing their promising utility in tumor-targeting therapy. As an important perspective on carrier systems based on polymeric micelles, their feasibility as non-viral gene vectors is also summarized in this review article. [Copyright &y& Elsevier]

Abstract: A new family of block ionomer complexes (BIC) formed by poly(ethylene glycol)-block-poly(4-vinylbenzylphosphonate) (PEG-b-PVBP) and various cationic surfactants was prepared and characterized. These complexes spontaneously self-assembled in aqueous solutions into particles with average size of 40–60nm and remained soluble over the entire range of the compositions of the mixtures including stoichiometric electroneutral complexes. Solution behavior and physicochemical properties of such BIC were very sensitive to the structure of cationic surfactants. Furthermore, such complexation was used for incorporation of cationic anti-cancer drug, doxorubicin (DOX), into the core of BIC with high loading capacity and efficiency. The DOX/PEG-b-PVBP BIC also displayed high stability against dilution, changes in ionic strength. Furthermore, DOX release at the extracellular pH of DOX/PEG-b-PVBP BIC was slow. It was greatly increased at the acidic pH mimicking the endosomal/lysosomal environment. Confocal fluorescence microscopy using live MCF-7 breast cancer cells suggested that DOX/PEG-b-PVBP BICs are transported to lysosomes. Subsequently, the drugs are released and exert cytotoxic effect killing these cancer cells. These findings indicate that the obtained complexes can be attractive candidates for delivery of cationic drugs to tumors. [Copyright &y& Elsevier]

Abstract: The delivery of siRNA therapeutics owes its success to the development of carrier systems with high efficacy and minimum toxicity. Here, cationic polyaspartamide derivatives with a regulated number and spacing of positively charged amino groups in the side chain were prepared from a single platform polymer of poly(β-benzyl l-aspartate) to assess their availability as siRNA carriers through polyion complex (PIC) formation. These polymers have 1,2-diaminoethane, 1,3-diaminopropane, and N,N’-bis(2-aminoethyl)-1,2-diaminoethane moieties in the side chain, and are termed as PAsp(DET), PAsp(DPT), and PAsp(TEP), respectively. siRNA-loaded PICs stable in serum-containing media were formed from PAsp(TEP) and PAsp(DPT) with two positive charges in the side chain at pH 7.4, whereas no such stable PIC was obtained from PAsp(DET) with only a single charge in the side chain, suggesting facilitated multivalent interactions with siRNA molecules to increase the PIC stability. The PAsp(DPT) and PAsp(TEP) PICs stable in the serum-containing media underwent an appreciably enhanced uptake into cultured cells through endocytosis, and subsequently exerted effective endosomal escape for the significant silencing of target gene expression. Notably, PAsp(TEP) PIC displayed negligible cytotoxicity in sharp contrast to the highly toxic feature of PAsp(DPT) PIC. This cytotoxicity is apparently correlated with the minimal damage to the cytoplasmic membrane of cells exposed to PAsp(TEP) at pH 7.4 evidenced from the fluorescent dye (YO-PRO-1) permeation assay. There was, in turn, a significant increase in YO-PRO-1 permeability at endosomal pH of 5.5 for PAsp(TEP)-exposed cells, indicating that PAsp(TEP) exerts membrane damage in a pH-selective manner, and eventually facilitates the translocation of siRNA-loaded PIC from the acidic endosomal compartment into the cytoplasm for effective gene silencing without any severe toxicity at physiological conditions. This acidic pH modulated enhancement in membrane damage of PAsp(TEP) may be explained by an increased protonation of the arrayed amino groups in the side chain that strongly perturb the endosomal membrane integrity. Eventually, PAsp(TEP) with a side chain array of pH-sensitive amino groups was demonstrated to be a promising component for constructing siRNA carriers exerting effective gene silencing in a less toxic context. [Copyright &y& Elsevier]

Abstract: This study demonstrated that gel-like polyion complexes obtained by mixing of aqueous solution of chondroitin sulfate, heparin, and hyaluronic acid with that of chitosan were able to form their free-standing films using hot press treatments. These films, having thicknesses ca. 50 and 100μm, depending on the spacer thickness, were homogeneous and non-porous at the microscopic level, and were not water-soluble. The present fabrication process required neither cross-coupling agents nor introduction of other functional groups to the polysaccharides. Hydroxyapatite deposition on the film surfaces under body fluid conditions was also achieved. [Copyright &y& Elsevier]

Abstract: Polymeric micelles, as drug delivery vehicles, must achieve specific targeting and high stability in the body for efficient drug delivery. We recently reported the preparation of polyanion-coated biodegradable polymeric micelles by coating positively charged polymeric micelles consisting of poly(l-lysine)-block-poly(l-lactide) (PLys-b-PLLA) AB diblock copolymers with anionic hyaluronic acid (HA) by polyion complex (PIC) formation. The obtained HA-coated micelles showed significantly higher stability in aqueous solution. In this study, to evaluate the HA-coated polymeric micelles as a drug carrier, model drug release from the micelles and cytotoxicity of the micelles were investigated. The HA-coated micelles showed sustained release of model drugs and low cytotoxicity. It is known that there are receptors for HA on liver sinusoidal endothelial cells (LSEC). Specific interactions of HA-coated micelles with LSECs and Kupffer cells were investigated and compared with polymeric micelles coated with other polyanionic polysaccharides, i.e., heparin (Hep) and carboxymethyl-dextran (CMDex). Although Hep-coated micelles and CMDex-coated micelles were incorporated into both Kupffer cells and LSECs, HA-coated micelles were taken up only into LSECs. These results suggest HA-coated micelles have potential utility as drug delivery vehicles exhibiting specific accumulation into LSECs. [Copyright &y& Elsevier]

Abstract: Biocompatible polymer–magnetite hybrid nanoparticles were prepared by means of in situ synthesis of magnetite within polysaccharide hydrogel nanoparticles. Hydrogel nanoparticles were first fabricated by blending high-molecular-weight carboxymethyl cellulose as an anionic polymer, and low-molecular-weight chitosan as a cationic polymer to form polyion complexes (CC particles). These polyion complexes were then chemically crosslinked using genipin, a bio-based cross-linker, to form stable nanoparticles having a semi-IPN structure (CCG particles). Magnetite was lastly synthesized within CCG particles by the coprecipitation method to obtain polymer–magnetite hybrid nanoparticles (CCGM particles). The formations of CC, CCG and CCGM particles were mainly observed by transmittance, absorbance of genipin and TEM, respectively, and their hydrodynamic diameters and zeta-potentials were analyzed. It was confirmed that the hydrodynamic diameters and the zeta-potentials of these particles were significantly influenced by pH of the suspension, which was attributed to the charges of polymers. The diameters of CCGM particles were smaller than 200nm at any pH conditions, suggesting the possibility to apply them as drug delivery carriers. CCGM particles exhibited the responsiveness to a magnetic field in addition to their high dispersion stability, indicating their potential to be utilized as a biomaterial for hyperthermia. [Copyright &y& Elsevier]

Abstract: This review describes the design of polymeric micelles from block copolymers and their performances as nano-scale drug delivery systems, with emphasis on our recent work. The basic drug delivery system platform developed by our group consists of polymeric micelles comprising a core–shell structure with a versatile drug-loading hydrophobic core and biocompatible hydrophilic shell, and are several tens to one hundred nanometer in size. These characteristics are preferable to bypass both renal clearance and entrapment by the reticuloendothelial system, thus allowing subsequent accumulation within tumor tissues by the enhanced permeability and retention effect. Furthermore, polymeric micelles may be designed for enhanced biological performance by modification of the block copolymers to contain chemistries that can sense a specific biological environment. These “smart” micelles allow for target site-triggered drug release by reversible stabilization of the micelle structure and controlled intracellular trafficking (efficient endosomal release). Smart micelles designed with responsive features have demonstrated the utility in many cases compared to controls lacking such functionality. Additionally, the ability to control the size of polymeric micelles in the range of several tens to hundreds of nanometer significantly affects their longevity in the blood stream and efficiency of tumor tissue accumulation and penetration. In hypovascular tumor tissues, smaller polymeric micelles are more effective for tissue accumulation/penetration, bringing about stronger anti-tumor activity. All together, fine-tuning the structure of block copolymers enables preparation of polymeric micelles with versatile functions for treatment of many diseases including intractable cancer. [Copyright &y& Elsevier]

Abstract: The current study synthesized macromolecular magnetic resonance imaging (MRI) contrast agents constituted of the poly(ethylene glycol)-b-poly(l-lysine) block copolymer (PEG-P(Lys)). A chelate group, 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA), was attached to the primary amino group of the block copolymer in desired contents. Gd-DOTA-based macromolecular contrast agents were prepared from PEG-P(Lys) having DOTA (PEG-P(Lys-DOTA) and Gd(III) ions. All of the PEG-P(Lys) block copolymers having gadolinium ions (PEG-P(Lys-DOTA-Gd)) showed higher T 1 relaxivity (per gadolinium), r 1 =5.6–7.3mM−1 s−1, than that of a low-molecular-weight gadolinium-chelate, diethylenetriaminepentaacetic acid-gadolinium(III) (Gd-DTPA) at 9.4T. The study prepared the polyion complex (PIC) micelles from the amino groups of the lysine units and an oppositely charged polyanion, poly(methacrylic acid) or dextran sulfate, in an aqueous medium. In contrast, the fully DOTA-attached PEG-P(Lys-DOTA-Gd) formed a PIC with a polycation. Compared with partially DOTA-attached cationic PEG-P(Lys-DOTA-Gd), this PIC micelle yielded a forty percent decrease of r 1. This r 1 decrease was considered to result from a change in the accessibility of water molecules to gadolinium ions in the micelles'' inner core. The r 1 was decreased upon formation of the PIC micelle, and this change proved that our concept worked in vitro. Blood-circulation characteristics of PIC micelles were controlled by means of changing the molecular weight of the counter anion. The PIC micelles accumulated in tumor tissues, and MRI study showed T1W image of axial slice of tumor area was significantly enhanced at 24h after the injection. [Copyright &y& Elsevier]

Abstract: An siRNA-grafted polymer through disulfide linkage was prepared to improve the physicochemical properties and transfection efficacies of the polyion complexes (PICs) as a nanocarrier of siRNA. The siRNA-grafted polymer formed stable PICs due to its larger numbers and higher density of anionic charges compared with monomeric siRNA, leading to effective internalization by cultured cells. Following the endosomal escape of the PIC, the disulfide linkage of the siRNA-grafted polymer allowed efficient siRNA release from the PIC under intracellular reductive conditions. Consequently, the PIC from the siRNA-grafted polymer showed a potent gene silencing effect without cytotoxicity or immunogenicity, demonstrating a promising feature of the siRNA-grafted polymer to construct the PIC-based nanocarrier for in vivo siRNA delivery. [ABSTRACT FROM AUTHOR]

Abstract: For the development of an siRNA delivery system using polyion complexes (PICs) based on PEGylated nanogel consisting of a cross-linked poly[2-(N,N-diethylaminoethyl) methacrylate] (PEAMA) gel core and tethered poly(ethylene glycol) (PEG) chains, quaternary ammonium groups were introduced in the polyamine gel core to enhance the binding ability with siRNA and the stability of the PICs. Consequently, the quaternization of the polyamine core of the nanogel facilitated the binding ability with siRNA at a low N/P ratio, and the stability against polyanion displacement was enhanced as the degree of quaternization (DQ) of the nanogel increased. Although the installation of the positively charged quaternary ammonium moieties in the core of the nanogel resulted in the increment of the ξ-potential of the PICs (e.g. +23mV for DQ=100%), the cytotoxicity was reduced with the increase of DQ presumably due to the hydrophilic character of the quaternary ammonium groups. The installation of quaternary ammonium groups in the core of the nanogel enhanced the endogenous gene silencing activity against the survivin gene in human hepatocarcinoma (HuH-7 cells), especially, the partly quaternized polyamine nanogel (DQ=10%) showed the highest gene silencing ability among the quaternized polyamine nanogels, including the tertiary amine nanogel. The cellular uptake analysis of the Rhodamine B-labeled Q-nanogel/fluorescein-labeled siRNA complex revealed that the quaternization of PEAMA moieties enhanced the cellular uptake level of fluorescein-labeled siRNA with the increase in DQ, whereas the cellular uptake of the Rhodamine B-labeled Q-nanogels was almost of the same level regardless of the DQ value, indicating that significant cellular uptake of the fluorescein-labeled siRNA is most likely due to the enhancement of the binding ability with siRNA in the serum-containing medium. Note that the endosomal escape efficiency was reduced with increase in the DQ value due to the decrease in the buffering capacity (tertiary amino groups) of the PEAMA core. On the basis of these results, the ratio of quaternary ammonium groups to tertiary amino groups in the core of the nanogel plays a pivotal role in the achievement of significant gene silencing through enhanced cellular uptake (quaternary ammonium groups) and subsequent endosomal escape (tertiary amino groups). [Copyright &y& Elsevier]

Abstract: Palladium nanoparticles stabilized by a polyion complex composed of poly{4-chloromethylstyrene-co-(4-vinylbenzyl) tributylammonium chloride} and poly(acrylic acid) were easily recovered by filtration after pH treatment. The polyion complex stabilized palladium nanoparticles have high catalytic activity for the Suzuki and Heck reactions in water. [ABSTRACT FROM AUTHOR]

Abstract: We have developed a rapid and simple gas toxicity evaluation system based on bioluminescence inhibition of a marine-derived wild luminous bacterium, Vibrio fischeri. The luminous bacteria were trapped using a thin polyion complex membrane in order to allow semi direct contact between the bacteria and toxic gases. Bioluminescence inhibition ratios of the present system to six reference gases, including benzene, trichloroethylene, acetone, NO2, SO2, and CO, were evaluated, and dose–response relationships were successfully obtained after 15min of gas exposure, except for CO gas. The sensitivity to the five gases except for CO gas of the present system was 1–3 orders of magnitude higher than that in acute animal tests. The present system also allowed for the evaluation of overall toxicity of some environmental gases containing various chemicals. These results clearly demonstrated that the present system would be a valuable prototype for rapid and on-site acute toxicity detection of a gas mixture, such as environmental gases. [Copyright &y& Elsevier]

Abstract: Poly(vinylamine), the simplest polycation with primary amines, was applied to interpenetrating polymer networks (IPN) with poly(acrylic acid). N-Vinylformamide (NVF) was employed for amino-protected monomers to control electrostatic balance. pH-responsivities of IPNs varied, depending on the hydrolysis conditions and acrylic acid (AAc) concentration of the second network. Poly(N-vinylacetamide)-co-poly(N-vinylformamide) (4/6, mol/mol) was employed for the first network, subsequently hydrolyzed with 50% amide groups, and the second network was polymerized with 0.25molL−1 AAc, extremely shrunken hydrogels with polyion complex were formed at pH 7, showing that the controlled amount of highly active primary amines are available in IPN. [Copyright &y& Elsevier]

Abstract: The microencapsulation of islets of Langerhans (islets) has been studied as a safe and simple technique for islet transplantation without the need for immuno-suppressive therapy. However, thinner membranes are desired, because the increased total volume of the implant led to limited transplantation sites. Here, we propose a novel method for microencapsulation by polyion complex membrane formation on islets. Amino group-terminated poly(ethylene glycol)-conjugated phospholipids (PEG-lipids, M w: 5000) spontaneously formed a thin layer on cells existing in the outer layer of islets when they were added to islet suspension. This layer-by-layer membrane could be further formed on the PEG-lipid layer through polyion complex formation between amino groups at the end of PEG chains, sodium alginate and poly(l-lysine). Islets could be microencapsulated by this method without volume increase. Encapsulation of the islet surface with PEG-lipids and polyion complex membranes did not impair the insulin release function in response to glucose stimulation. Our method is promising to encapsulate islets without affecting cell viability or increasing volume. [Copyright &y& Elsevier]

Abstract: Two kinds of urease-immobilized polymer membranes were prepared. One was prepared by bulk-copolymerizing a mixture consisting of vinylized urease (VU), acrylamide (AAm), 2-hydroxylethylmethacrylate (HEMA) and a cross-linker (urease-immobilized poly(VU-AAm-HEMA) membrane) and another was prepared by ultrafiltrating a mixture composed of urease, quaternized chitosan and sodium carboxymethylcellulose in an aqueous sodium bromide solution (urease-immobilized polyion complex membrane). The permeation and hydrolytic characteristics of aqueous urea solutions were kinetically investigated under various conditions through urease-immobilized membranes. The hydrolysis of urea through urease-immobilized membranes followed Michaelis–Menten kinetics and is discussed herein. [Copyright &y& Elsevier]

Abstract: This aim of this study was to encapsulate retinol into chitosan nanoparticles and reconstitute it into aqueous solution. Retinol-encapsulated chitosan nanoparticles were prepared for application of cosmetic and pharmaceutical applications. Retinol-encapsulated chitosan nanoparticle has a spherical shape and its particle sizes were around 50–200nm according to the drug contents. Particle size was increased according to the increase of drug contents. Solubility of retinol is able to increase by encapsulation into chitosan nanoparticles more than 1600-fold. It was suggested that retinol was encapsulated into chitosan nanoparticles by ion complex as a result of FT-IR spectra. Specific peak of chitosan at 1590cm−1 was divided to semi-doublet due to the electrostatic interaction between amine group of chitosan and hydroxyl group of retinol. At 1H NMR spectra, specific peaks of retinol disappeared when retinol-encapsulated chitosan nanoparticles were reconstituted into D2O while specific peaks both of retinol and chitosan appeared at D2O/DMSO (1/4, v/v) mixture. XRD patterns also showed that crystal peaks of retinol were disappeared by encapsulation into chitosan nanoparticles. Retinol-encapsulated nanoparticles were completely reconstituted into aqueous solution as same as original aqueous solution and zeta potential of reconstituted chitosan nanoparticles was similar to their original solution. At HPLC study, retinol was stably and efficiently encapsulated into chitosan nanoparticles. [Copyright &y& Elsevier]

Abstract: The aim of this comparative study was to investigate the in vivo drug release property of hydrophilic dextran tablets with or without swelling in the upper gastrointestinal tract (GIT) in humans. Two kinds of theophylline (TH) tablets were prepared by direct compression from a mixture of carboxymethyldextran and [2-(diethylamino)ethyl]dextran as a matrix capable of forming polyion complex (PIC-tablet), and a mixture of low and medium molecular weight hydroxypropylcellulose as a representative hydrophilic matrix (HPC-tablet). In these tablets, in vitro drug release behaviors and saliva TH level profiles after oral administration to humans were similar to each other, indicating equivalent AUC value. The tablets were then coated with Eudragit® S100, enteric-coating polymer, by a dipping method in order to reveal drug release without full swelling in the upper GIT. Although the two enteric-coated tablets showed a similar in vitro release pattern, saliva level profiles were quite different as reflected in AUC values of 16.4 and 4.68 μg h/ml for enteric-coated PIC- and enteric-coated HPC-tablet, respectively. These results demonstrated that HPC-tablet could not release sufficiently without swelling in the upper GIT. In contrast, enteric-coated PIC-tablet showed an equivalent AUC value to PIC-tablet, indicating that TH was released well even in the lower GIT. [Copyright &y& Elsevier]

Abstract: In this review we present an overview of the developments of (self-)assembly of linear block copolymers containing one or more polyelectrolyte blocks in aqueous solution. Different micellar structures and phase behaviour are described. The role of inter- and intramolecular complex coacervation is emphasised. Recent developments in applications of assembly of polyelectrolyte-containing copolymers are presented. [Copyright &y& Elsevier]

Abstract: Biological phosphate ester (phosphoric ester) substances, e.g. ATP, ADP, AMP, pyrophosphate and deoxyribonucleic acid, play important roles as either energy-carrying substances or substances carrying biological information. The author has designed and synthesized an artificial enzyme PMP complex (Cu) which dephosphorylates phosphate ester substances. The synthesized PMP complex (Cu) showed a prominent dephosphorylating effect on biological phosphate ester substances, e.g. ATP, ADP, AMP and pyrophosphate. A PMP complex (Cu)-coated electrode was employed as a sensor device. A current response could be obtained as a reaction to the application of phosphate ester substances on the sensor when a constant potential of −250mV versus Ag/AgCl was applied. In the case of ATP, the sensor could determine the ATP concentration within the range between 1nM and 20mM, and could also determine the presence of other biological phosphate ester substances. [Copyright &y& Elsevier]

Abstract: To separate the cell population in whole blood using microcanal, the surface was covered with a polyion complex (PIC) composed of electrically charged phospholipid polymers. The phospholipids polymers were prepared by the polymerization of 2-methacryloyloxyethyl phosphorylcholine (MPC) and n-butyl methacrylate with 3-(methacryloyloxypropyl)-trimethyl ammonium iodide as the cationic unit or potassium 3-methacryloyloxypropyl sulfonate as the anionic unit. The PIC was formed at the solid-liquid interface, that is, first, the cationic polymer was coated on the substrate and an aqueous solution containing the anionic polymer with different concentrations was applied to the polymer-coated substrate. The formation of the PIC was followed using a quartz crystal microbalance (QCM), and the PIC surfaces were analyzed by both ζ-potential measurement and X-ray photoelectron spectroscopic measurement. The surface electrical potential on the PIC was controllable from +40 to −40mV by increasing the amount of the adsorbed anionic polymer. The PIC surface was prepared in microcanal. The surface electrical potential was sequentially changed. When the whole blood was introduced into the microcanal, the cells adhered on the positively charged surface, but could not adhere to the negatively charged surface. Even when the cells adhere to the surface, the morphology of cells was maintained. This is due to MPC units at the surface, which show a good biocompatibility. These results indicated that the change in the surface electrical potential will be a useful method to separate the cells from whole blood. [Copyright &y& Elsevier]

Abstract: Unicellular microalga Chlorella vulgaris was entrapped in an alginate gel or a polyion complex membrane immobilized directly on the surface of a transparent indium tin oxide electrode. Photosynthetically generated oxygen of the immobilized algae was monitored amperometically. Responses of the algal biosensor to four toxic compounds, 6-chloro-N-ethyl-N-isopropyl-1,3,5-triazine-2,4-diamine (atrazine), 3-(3,4-dichlorophenyl)-1,1-diethylurea (DCMU), toluene and benzene, were evaluated as inhibition ratios of the reduction current. The concentrations that give 50% inhibition of the oxygen reduction current () for atrazine, DCMU, toluene and benzene were 2.0, 0.05, 1550 and 3000μmoldm-3, respectively. There was a good correlation between these data and those of the conventional standard growth test. In comparison with the conventional algal biosensors based on the Clark-type oxygen electrode, the present sensor is much smaller and less expensive, and its assay time is much shorter (≤200s). [Copyright &y& Elsevier]

Poly(ethylene glycol) (PEG) derivative having both carboxylic acid-, and lactose-side chains (Lac-PEG-C) deposited onto the surface of DNA/protamine (PRT) complex, and the self-assembled ternary complex was obtained. The diameter of the complexes was 180–200 nm, and they showed good size stability even in the high ionic strength solutions. Lac-PEG-C coating reduced their surface electric potential, and effectively avoided the albumin-induced aggregation. DNA/PRT/Lac-PEG-C complex did not coagulate the red blood cells, and their cytotoxicity evaluated by WST-1 was very low. Lac-PEG-C added to the plasmid/PRT complex prior to the incubation with HepG2 cells extremely enhanced the gene-expression, and by the plasmid/PRT/Lac-PEG-C complex prepared at 1:1.5:8 in weight, 56-fold higher expression of luciferase than that without Lac-PEG-C was observed. The treatment with asialofetuin or phenylarsine oxide evidently interfered with the gene-expression. The high gene expression by the plasmid/PRT/Lac-PEG-C ternary complex on the hepatocyte would be attributed to the asialoglycoprotein receptor-mediated endocytosis. [Copyright &y& Elsevier]

We have constructed a cell-based assessing system for chemicals using a probe-type electrochemical nitric oxide (NO) sensor. This system can be used to assess the effects of chemicals on the nitric oxide signaling pathway in immune systems. NO was used as an indicator of a cellular immune response due to chemical exposure. RAW264.7 cells, a macrophage-like cell line, were used as a model immune cell. The novel probe-type electrochemical NO sensor, consisting of a Pt counter electrode, an Ag/AgCl reference electrode, and a gold electrode coated with a polyion complex layer, was constructed for this study. The NO sensor probe measures NO without the drawback of electrochemical interference. The detection limit of the sensor was 8.4 nM NO. The cell-based system was able to assess the immuno-activating effects of lipopolysaccharide and interferon-γ, and the inhibiting effects of l-NMMA in a dose-dependent manner. [Copyright &y& Elsevier]

Polyion complex (PIC) micelles composed of the poly(ethylene glycol)–poly(l-lysine) (PEG–PLL) block copolymer and plasmid DNA (pDNA) were investigated in this study from a physicochemical viewpoint to get insight into the structural feature of the PIC micellar vector system to show practical gene transfection efficacy particularly under serum-containing medium. The residual ratio (r) of the lysine units in PEG–PLL to the phosphate units of pDNA in the system significantly affects the size of the PIC micelles evaluated from dynamic light scattering, being decreased from approximately 120 to 80 nm with an increase in the r value for the region with r&ges;1.0. The zeta potential of the complexes slightly increased with r in the same region, yet maintained a very small absolute value and leveled off to a few mV at r&ap;2.0. These results suggest that the micelles are most likely to take the core-shell structure with dense PEG palisades surrounding the PIC core to compartmentalize the condensed pDNA. Furthermore, an increasing r value in the region of r&ges;1 induces a rearrangement of the stoichiometric complex formed at r=1.0 to the non-stoichiometric complex composed of the excess block copolymer. The association number of pDNA and the block copolymer in the micelle was estimated from the apparent micellar molecular weight determined by static light scattering measurements, indicating that a single pDNA molecule was incorporated in each of the micelles prepared from the PEG (Mw=12,000 g/mol)–PLL (polymerization degree of PLL segment: 48) (12-48) block copolymer at r=2.0. These 12-48/pDNA micelles showed a gene expression comparable to the lipofection toward cultured 293 cells, though 100 μm chloroquine was required in the transfection medium. Notably, even in the presence of serum, the PIC micelles achieved appreciable cellular association to attain a high gene expression, which is in sharp contrast with the drastic decrease in the gene expression for lipoplex system in the presence of serum. A virus-comparable size (∼100 nm) with a serum-tolerable property of the PIC micelles indeed suggests their promising feasibility as non-viral gene-vector systems used for clinical gene therapy. [Copyright &y& Elsevier]

The aim of this study was to investigate the effects of polyion complex formation on in vivo performance of hydrophilic matrix tablets. Three kinds of controlled release theophylline tablets were prepared by direct compression using carboxymethyldextran (CMD), a mixture of CMD and [2-(diethylamino)ethyl]dextran (EA), and a mixture of dextran sulfate (DS) and EA. According to a conventional dissolution test, in vitro drug release profiles of these tablets were similar to each other. In vivo absorption profiles of theophylline after oral administration to beagle dogs, however, were quite different and were not consistent with in vitro release profiles. Thus, we applied a modified in vitro release test considering destructive forces. An excellent in vitro/in vivo correlation was obtained in the cases of CMD/EA- and DS/EA-tablets. The results suggested that the drug was released constantly in the overall gastrointestinal tract, and even in the colon. Then, hydrophilic matrices were characterized by swelling rate, matrix density and strength in a wet state. DS/EA-tablets showed limited swelling, higher density and a larger value of wet strength than the others. These findings indicated that polyion complex formation in gel layer contributes to prevent over-swelling and strengthen the wetted matrices. [Copyright &y& Elsevier]

The objective of this study was to evaluate mucoadhesive properties and gastrointestinal transit of microspheres made of oppositely charged dextran derivatives and cellulose acetate butyrate (CAB). The microspheres were prepared by emulsion solvent evaporation method. A reference microsphere was made of lactose instead of dextran derivatives. Microspheres with a diameter of 425–710 μm were examined for in vitro mucoadhesion by the everted sac method. The results indicated that the percentage of adherence to the rat small intestine was affected by the amount of dextran derivatives in the microspheres. After 1.5 h, the adhering percent of the reference microspheres and the microspheres containing 50% of dextran derivatives were 34 and 74%, respectively. Then gastrointestinal transit after oral administration to rats was evaluated by counting the microspheres remaining in the stomach and small intestine. The microspheres containing 40% of dextran derivatives adhered to the stomach rather than the small intestine. Mathematical analysis revealed that the time required for 50% of microspheres to leave the stomach was 1.42 h, three times longer than the reference. These findings suggest that the microsphere is a promising device as a multiple-unit mucoadhesive system. [Copyright &y& Elsevier]