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Graphene oxide (GO) membranes have been proposed for water treatment. GO can be used to prepare membranes that remove organic molecules, such as model dyes from contaminated wastewater. In practical applications, wastewater is often acidic or alkaline. The physico-chemical properties of GO are only weakly affected by pH, and this can lead to poor membrane performance for the removal of positively charged model compounds. In this work, we used pH-responsive poly (methacrylic acid) (PMAA) to prepare GO-PMAA materials through chemical crosslinking. GO-PMAA materials with different compositions were used to prepare membranes via physical intercalation. The membranes were tested for removal of five different dyes of different sizes and valency (including those that are positively charged, negatively charged, and neutral at neutral pH). We identify a membrane composition that works well for the removal of negatively charged methyl orange and Evans blue under acidic conditions (with 73.1% and 99.7% rejection, respectively) with improved water permeance compared to membranes prepared with GO alone. In addition, we evaluated the long-term stability of the nanofiltration membrane. After continuous operation for 20 h, the rejection rate of MnB by 5p-nGOM was about 85.37%, and the water permeance relatively stable, while the rejection rate of MnB by nGOM was about 26.59%, and the water permeance changed greatly. These findings indicate that GO membranes modified with pH-responsive polymers can achieve superior performance with respect to separation, water permeance, long-term operation, and pressure resistance, compared to GO membranes. • GO-PMAA composites were prepared by chemical cross-linking method. • GO-PMAA materials with different compositions were used to prepare membranes via physical intercalation. • Preparation of pH-responsive composite membranes. • The pH-responsive composite membrane exhibited good rejection of negatively charged dyes (MO and EB) under acidic conditions. [ABSTRACT FROM AUTHOR]

Ultralow protein fouling behavior is a common target for new high-performance materials. Ultralow fouling is often defined based on the amount of irreversibly adsorbed protein (< 5 ng cm−2) measured by a surface ensemble averaging method. However, protein adsorption at solid interfaces is a dynamic process involving multiple steps, which may include adsorption, desorption, and irreversible protein denaturation. In order to better optimize the performance of antifouling surfaces, it is imperative to fully understand how proteins interact with surfaces, including kinetics of adsorption and desorption, conformation, stability, and amount of adsorbed proteins. Defining ultralow fouling surfaces based on a measurement at or near the limit of detection of a surface-averaged measurement may not capture all of this behavior. Single-molecule microscopy techniques can resolve individual protein-surface interactions with high temporal and spatial resolution. This information can be used to tune the properties of surfaces to better resist protein adsorption. In this work, we demonstrate how combining surface plasmon resonance, X-ray photoelectron spectroscopy, atomic force microscopy, and single-molecule localization microscopy provides a more complete picture of protein adsorption on low fouling and ultralow fouling polyelectrolyte multilayer and polymer brush surfaces, over different regimes of protein concentration. In this case, comparing the surfaces using surface plasmon resonance alone is insufficient to rank their resistance to protein adsorption. Our results suggest a revision of the accepted definition of ultralow fouling surfaces is timely: with the advent of time-resolved studies of protein adsorption kinetics at the single-molecule level, it is neither necessary nor sufficient to rely on a surface averaging techniques to qualify ultralow fouling surfaces. Since protein adsorption is a dynamic process, understanding how surface properties affect the kinetics of protein adsorption will enable the design of future generations of advanced antifouling materials. The design of ultralow fouling surfaces is often optimized based on a single surface-averaging technique measuring the amount of irreversibly adsorbed protein. This work provides a critical comparison of alternative techniques for evaluating protein adsorption on low fouling and ultralow fouling surfaces, and demonstrates how additional information about the dynamics of protein-surface interactions at the interface can be obtained by application of single-molecule microscopy. This approach could be used to better elucidate mechanisms of protein resistance and design principles for advanced ultralow fouling materials. Image, graphical abstract [ABSTRACT FROM AUTHOR]

Blood vessels present a dense, non-uniform, polysaccharide-rich layer, called the endothelial glycocalyx. The polysaccharides in the glycocalyx include polyanionic glycosaminoglycans (GAGs). This polysaccharide-rich surface has excellent and unique blood compatibility. We report new methods for preparing and characterizing dense GAG surfaces that can serve as models of the vascular endothelial glycocalyx. The GAG-rich surfaces are prepared by adsorbing heparin or chondroitin sulfate-containing polyelectrolyte complex nanoparticles (PCNs) to chitosan-hyaluronan polyelectrolyte multilayers (PEMs). The surfaces are characterized by PeakForce tapping atomic force microscopy, both in air and in aqueous pH 7.4 buffer, and by PeakForce quantitative nanomechanics (PF-QNM) mode with high spatial resolution. These new surfaces provide access to heparin-rich or chondroitin sulfate-rich coatings that mimic both composition and nanoscale structural features of the vascular endothelial glycocalyx. [ABSTRACT FROM AUTHOR]

Abstract: Here we present a novel matrix-mimetic nanoassembly based on polysaccharides. Chitosan electrospun fiber networks are decorated with heparin-containing polyelectrolyte complex nanoparticles (PCNs) that present basic fibroblast growth factor (FGF-2), both stably adsorbed to the surfaces and released into solution. These FGF-2/PCN complexes can be released from the fibers with zero-order kinetics over a period of 30days. Further modification of fibers with a single bilayer of polyelectrolyte multilayer (PEM) composed of N,N,N-trimethyl chitosan and heparin completely prevent release, and the FGF-2/PCN complexes are retained on the fibers for the duration of the release experiment (30days). We also compare the mitogenic activity of these FGF-2/PCN complexes delivered in two different states: adsorbed to a surface and dissolved in solution. FGF-2/PCN complexes exhibit mitogenic activity with respect to ovine bone marrow-derived mesenchymal stem cells, even after being preconditioned by incubating for 27days at 37°C in solution. However, when the FGF-2/PCN complexes are adsorbed to chitosan and coated with PEMs, the mitogenic activity of the FGF-2 steadily decreases with increasing preconditioning time. This work demonstrates a new system for stabilizing and controlling the delivery of heparin-binding growth factors, using polysaccharide-based matrix-mimetic nanomaterials. This work also contributes to our understanding of the preferred mode of growth factor delivery from porous scaffolds. [Copyright &y& Elsevier]

Abstract: Nanofiber poly(ε-caprolactone) (PCL) scaffolds were fabricated by electrospinning, and their ability to enhance the osteoblastic behavior of marrow stromal cells (MSCs) in osteogenic media was investigated. MSCs were isolated from Wistar rats and cultured on nanofiber scaffolds to assess short-term cytocompatibility and long-term phenotypic behavior. Smooth PCL substrates were used as control surfaces. The short-term cytocompatibility results indicated that nanofiber scaffolds supported greater cell adhesion and viability compared with control surfaces. In osteogenic conditions, MSCs cultured on nanofiber scaffolds also displayed increased levels of alkaline phosphatase activity for 3weeks of culture. Calcium phosphate mineralization was substantially accelerated on nanofiber scaffolds compared to control surfaces as indicated through von Kossa and calcium staining, scanning electron microscopy and energy-dispersive X-ray spectroscopy. Increased levels of intra- and extracellular levels of osteocalcin and osteopontin were observed on nanofiber scaffolds using immunofluorescence techniques after 3weeks of culture. These results demonstrate the enhanced tissue regeneration property of nanofiber scaffolds, which may be of potential use for engineering osteogenic scaffolds for orthopedic applications. [Copyright &y& Elsevier]

The phase behavior of a biocompatible binary polyanhydride blend system composed of poly[1,6-bis(p-carboxyphenoxy)hexane] (poly(CPH)) and poly(sebacic acid) (poly(SA)) is described. The phase behavior is determined from the CPH-SA segmental interaction parameter, χ, obtained from in situ small angle X-ray scattering (SAXS) experiments. The predicted phase diagram has an upper critical solution temperature (UCST) with a critical point of 114 °C. The phase diagram is validated by optical microscopy (cloud point determination) of blend films. However, the full range of blend compositions is not accessible via cloud point measurements, because the melting point of poly(CPH) is above the critical point. Additionally, the poly(CPH) crystallinity interferes with cloud point determination because the length scale of the amorphous phase separation and that of the crystallinity are both near the limit of resolution of the optical microscope. The poly(CPH)-rich region of the phase diagram was investigated by ex situ atomic force microscopy on thin blend films. Finally, in order to validate the use of molecular simulations to study energetic and structural properties of this system, χ is also computed from molecular dynamics both above and below the critical point. Excellent agreement is obtained for all three experimental methods and the computational technique. The results are compared to a simple group contribution method for computing the solubility parameters of the polymers. This technique fails to accurately predict the phase diagram. [Copyright &y& Elsevier]

A thorough understanding of the factors affecting drug release mechanisms from surface-erodible polymer devices is critical to the design of optimal delivery systems. Poly(sebacic anhydride) (PSA) microspheres were loaded with three model drug compounds (rhodamine B, p-nitroaniline and piroxicam) with a range of polarities (water solubilities). The drug release profiles from monodisperse particles of three different sizes were compared to release from polydisperse microspheres. Each of the model drugs exhibited different release mechanisms. Drug distribution within the polymer was investigated by laser scanning confocal microscopy and scanning electron microscopy. Rhodamine, the most hydrophilic compound investigated, was localized strongly toward the microsphere surface, while the much more hydrophobic compound, piroxicam, distributed more evenly. Furthermore, all three compounds were most uniformly distributed in the smallest microspheres, most likely due to the competing effects of drug diffusion out of the nascent polymer droplets and the precipitation of polymer upon solvent extraction, which effectively “traps” the drug in the polymer matrix. The differing drug distributions were manifested in the drug release profiles. Rhodamine was released very quickly independent of microsphere size. Thus, extended release profiles may not be obtainable if the drug strongly redistributes in the microspheres. The release of p-nitroaniline was more prolonged, but still showed little dependence on microsphere size. Hence, when water-soluble drugs are encapsulated with hydrophobic polymers, it may be difficult to tailor release profiles by controlling microsphere size. The piroxicam-loaded microspheres exhibit the most interesting release profiles, showing that release duration can be increased by decreasing microsphere size, resulting in a more uniform drug distribution. [Copyright &y& Elsevier]

• Chitosan/alginate and N,N- dimethyl chitosan/alginate-based adsorbents are prepared. • An ionic liquid is used to carry out the polysaccharide-based adsorbents. • Adsorbents are produced by precipitating of blends performed in an ionic liquid. • The ionic liquid is recovered and reused to create new adsorbents. • The adsorbents have high capacity for removing Pb(II) ions from aqueous systems. Alginate/chitosan (ALG/CHT) and alginate/ N , N -dimethyl chitosan (ALG/DMC) polyelectrolyte complex (PEC)-based adsorbents with high capacities for removing Pb(II) from aqueous systems are produced in [1-hydrogen-3-methylimidazolium hydrogen sulfate ionic liquid ([Hmim][HSO 4 ―]). The [Hmim][HSO 4 ―] is recovered, characterized by 1H NMR and reused to yield novel polysaccharide-based adsorbents. As-obtained PEC materials are characterized through infrared spectroscopy, scanning electron microscopy, X-ray photoelectron spectroscopy and Zeta potential measurements. Kinetic and equilibrium adsorption studies reveal that the pseudo-second-order Kinetic, as well as the Redlich-Peterson isotherm, provide the best fits for the experimental data, respectively. CHT/ALG and DMC/ALG adsorbents promoted maximum adsorption capacities (q m) of 529.4 mg g−1 and 560.2 mg g−1, respectively. After adsorption, the materials are characterized by infrared spectroscopy and X-ray photoelectron spectroscopy, confirming that the chemisorption prevails upon Pb(II) removal. Also, PECs produced in the recovered [Hmim][HSO 4 ―] have good capacities for removing Pb(II) ions from aqueous systems as well. This study showed that the [Hmim][HSO 4 ―] is an alternative solvent to prepare novel and eco-friendly PEC-based adsorbents. [ABSTRACT FROM AUTHOR]

For humans, companion animals, and food producing animals, vaccination has been touted as the most successful medical intervention for the prevention of disease in the twentieth century. However, vaccination is not without problems. With the development of new and less reactogenic vaccine antigens, which take advantage of molecular recombinant technologies, also comes the need for more effective adjuvants that will facilitate the induction of adaptive immune responses. Furthermore, current vaccine adjuvants are successful at generating humoral or antibody mediated protection but many diseases currently plaguing humans and animals, such as tuberculosis and malaria, require cell mediated immunity for adequate protection. A comprehensive discussion is presented of current vaccine adjuvants, their effects on the induction of immune responses, and vaccine adjuvants that have shown promise in recent literature. © 2008 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 98:1278–1316, 2009 [ABSTRACT FROM AUTHOR]

Abstract: When encapsulating proteins in polymer microspheres for sustained drug delivery there are three stages during which the stability of the protein must be maintained: (1) the fabrication of the microspheres, (2) the storage of the microspheres, and (3) the release of the encapsulated protein. This study focuses on the effects of polymer degradation products on the primary, secondary, and tertiary structure of tetanus toxoid, ovalbumin (Ova), and lysozyme after incubation for 0 or 20 days in the presence of ester (lactic acid and glycolic acid) and anhydride (sebacic acid and 1,6-bis(p-carboxyphenoxy)hexane) monomers. The structure and antigenicity or enzymatic activity of each protein in the presence of each monomer was quantified. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis, circular dichroism, and fluorescence spectroscopy were used to assess/evaluate the primary, secondary, and tertiary structures of the proteins, respectively. Enzyme-linked immunosorbent assay was used to measure changes in the antigenicity of tetanus toxoid and Ova and a fluorescence-based assay was used to determine the enzymatic activity of lysozyme. Tetanus toxoid was found to be the most stable in the presence of anhydride monomers, while Ova was most stable in the presence of sebacic acid, and lysozyme was stable when incubated with all of the monomers studied. [Copyright &y& Elsevier]

• Water-uptake can be suppressed in methacrylate-based dental composites. • Hydrolytic degradation can be suppressed in methacrylate-based dental composites. • All-hydrocarbon nanogels can be incorporated into labile polymer network. • Incorporated nanogels do not change dental resin formulation. • Water-uptake and degradation depends on nanogel loading level. The objective of this study was to demonstrate an approach with potential to increase the life of dental restorative polymers in water, by maintaining their strength and toughness with varied content of inert or reactive styrenic pre-polymeric additives. It was hypothesized that addition of styrene-co-divinylbenzene nanogels to a conventional dimethacrylate resin (e.g. TEGDMA) would reduce its susceptibility towards hydrolytic degradation, while maintaining equivalent mechanical properties. Polymerization kinetics and functional group conversions were determined by Fourier transform infrared spectroscopy. Triple-detection gel permeation chromatography was used for nanogel particle characterization. A goniometer was used to measure water contact angle on experimental and control photocured polymers. Hydrolytic degradation and mass loss evaluation was performed after extended water storage of an intentionally hydrolytically degradable polymer. Resin viscosity was determined rheometrically and polymer mechanical properties were evaluated using three-point flexural testing with TEGDMA-nanogel formulations. The polymer network with highest level of nanogel loading (50 wt%) and the highest level of internal nanogel crosslinking (50 mol%) had the lowest degree of equilibrium swelling ratio and mass loss. The flexural modulus and ultimate strength of polymerized TEGDMA and styrenic nanogel-modified TEGDMA were not statistically different (p > 0.05). Due to improved shielding throughout the bulk of methacrylate-based polymers, including an example with an intentionally hydrolytically labile network structure, and a dramatic decrease of water uptake while maintaining equivalent mechanical properties, styrenic nanogel additives especially in high loading levels provide an excellent alternative to eliminate the adverse effects of water and presumably salivary fluids. [ABSTRACT FROM AUTHOR]

Water-soluble luminescent lanthanide complexes that can be excited with visible light could enable rapid detection of toxic anions and cations in biological systems. Eu3+-induced hyaluronic acid-chitosan aggregates (EIHCA) can improve the stability, biocompatibility, efficiency, and light absorption of luminescent Eu3+ complexes. Visible-range excitation may avoid phototoxicity associated with overexposure to UV light in biological and ecological applications. In this work, we synthesized and characterized series of EIHCA complexes having three N -donor heterocyclic ligands: 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (Dphen), 2,2′: 6′,2″-terpyridine (Tpy) and 1,10-phenanthroline monohydrate (Phen). These complexes possessed bright red fluorescence with a visible range excitation maximum. The photophysical properties of one formulation (we denote as EDL6) include fast quenching response (20 s) of the fluorescence, multi-selectivity, low limit of detection, and high quenching (K sv) values, enabling selective, rapid and sensitive recognition of Cr 2 O 7 2− and Fe3+ in aqueous solution. Furthermore, EDL6 exhibits cytocompatibility with mammalian cells that make these complexes promising biocompatible candidate as a safe replacement of organic fluorophores for fluorescence sensing applications. Thus, these new EIHCA complexes were successfully employed for the selective detection of hazardous materials in biological and aqueous environment samples. [Display omitted] • Eu3+-induced hyaluronic acid-chitosan aggregate containing a combination of N -heterocyclic ligands, were synthesized. • These nanoparticles serve as fluorescent sensors with visible-range excitation, water stability and bio-compatibility. • Eu3+-complexes are fast and multi-responsive fluorescence sensors to detect Cr(VI) and Fe(III) in water. • Eu3+-fluorescent complex exhibits cell membrane permeability enabling detection of ions in live cell cultures. [ABSTRACT FROM AUTHOR]