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Methacrylate comb polymers were synthesized that have amphiphilic teeth of ethylene glycol oligomers capped with alkyl groups. Both segments are of exact length to promote self-organization and crystallization. The atactic methacrylate backbone plus close proximity to the polymer backbone inhibits crystallization of the oligoethyelene oxide segments, but the terminal alkyl segments readily crystallize. Wide-angle X-ray diffraction and differential scanning calorimetry were used to characterize polymer side chain crystallization and its evolution as a function of the length of the amphiphilic teeth. An analysis of the d spacings places the oligoethylene glycol segment and the first eight carbon atoms of the alkyl chain in an amorphous phase. An ∼1 Å/carbon atom increase in the d spacing is consistent with the crystalline segments being tilted relative to the polymer backbone. When the number of carbon atoms in alkyl segments is ≥ 14, addition of LiClCO 4 yields an ionic conducting ethylene oxide phase with retention of the alkyl crystallization. These novel polymer electrolytes use crystallization as a structural element to maintain dimensional stability. © 2006 American Chemical Society.

The goal of this article is to present a methodological critique of the 1998 meta-analysis of child sexual abuse outcomes by Rind, Tromovitch, and Bauserman. Seven major concerns are addressed. Rind et al.'s view is, at best, extremely limited. By restricting a supposedly broad meta-analysis to only some of the population in question, the conclusions they drew regarding this complex topic, primarily that adult-child sex is not necessarily harmful, are invalid. [ABSTRACT FROM AUTHOR]

This article presents a review of all types of child sexual abuse research ignored by Rind, Tromovitch, and Bauserman in their 1998 meta-analytic study. Eight major findings are addressed. Altogether, these findings demonstrate the narrow focus of the Rind et al. meta-analysis. By restricting a supposedly broad meta-analysis to only some of the research and population in question, the conclusions Rind et al. drew regarding this complex topic (primarily, that adult-child sex is not necessarily harmful to children) are invalid. [ABSTRACT FROM AUTHOR]

Thermal actuation is a common actuation method for soft robots. However, a major limitation is the relatively slow actuation speed. Here we report significant increase in the actuation speed of a bimorph thermal actuator by harnessing the snap-through instability. The actuator is made of silver nanowire/polydimethylsiloxane composite. The snap-through instability is enabled by simply applying an offset displacement to part of the actuator structure. The effects of thermal conductivity of the composite, offset displacement, and actuation frequency on the actuator speed are investigated using both experiments and finite element analysis. The actuator yields a bending speed as high as 28.7 cm -1 /s, 10 times that without the snap-through instability. A fast crawling robot with locomotion speed of 1.04 body length per second and a biomimetic Venus flytrap were demonstrated to illustrate the promising potential of the fast bimorph thermal actuators for soft robotic applications.

Wearable heaters have garnered significant attention from academia and industry for their great potential in thermotherapy. Silver nanowire (AgNW) is a promising conductive material for flexible and stretchable electrodes. Here, a resistive, biaxially stretchable heater based on AgNW composite is reported for the first time, where a AgNW percolation network is encased in a thin polyimide (PI) film and integrated with a highly stretchable textile. AgNW/PI is patterned with a 2D Kirigami structure, which enables constant resistance under a large tensile strain (up to uniaxial 100% strain and 50% biaxial strain). The heater can achieve a high temperature of ∼140 °C with a low current of 0.125 A, fast heating and cooling rates of ∼16.5 and ∼14.1 °C s -1 , respectively, and stable performance over 400 heating cycles. A feedback control system is developed to provide constant heating temperature under a temperature change of the surrounding environment. Demonstrated applications in applying thermotherapy at the curvilinear surface of the knee using the stretchable heater illustrate its promising potential for wearable applications.

Objective: Ethyltoluenes are isolated during crude oil refinement for use in gasoline and commercial products and are ubiquitous in the environment. However, minimal toxicity data are available. Previously, we identified 2-ethyltoluene (2-ET) as the most potent isomer via nose-only inhalation exposure in rodents. Here, we expanded the hazard characterization of 2-ET in two rodent models using whole-body inhalation exposure and evaluated the role of prenatal exposure., Methods: Time-mated Hsd:Sprague Dawley ® SD ® rats were exposed to 0, 150, 300, 600, 900, or 1200 ppm 2-ET via inhalation starting on gestation day 6 until parturition. Rat offspring ( n  = 8/exposure/sex) were exposed to the same concentrations as the respective dams for 2 weeks after weaning. Adult male and female B6C3F1/N mice ( n  = 5/exposure/sex) were exposed to the same concentrations for 2 weeks., Results and Discussion: Exposure to ≥600 ppm 2-ET produced acute toxicity in rats and mice characterized by large decreases in survival, body weight, adverse clinical observations, and diffuse nasal olfactory epithelium degeneration (rats) or necrosis (mice). Due to the early removal of groups ≥600 ppm, most endpoint evaluations focused on lower exposure groups. In 150 and 300 ppm exposure groups, reproductive performance and littering were not significantly changed and body weights in exposed rats and mice were 9-18% lower than controls. Atrophy of the olfactory epithelium and nerves was observed in all animals exposed to 150 and 300 ppm. These lesions were more severe in mice than in rats., Conclusion: Nasal lesions were observed in all animals after whole-body exposure up to 600 ppm 2-ET for 2 weeks. Future studies should focus on 2-ET metabolism and distribution to better understand species differences and refine hazard characterization of this understudied environmental contaminant.

Background: Increasing evidence from rodent studies indicates that inhaled multi-walled carbon nanotubes (MWCNTs) have harmful effects on the lungs. In this study, we examined the effects of inhalation exposure to MWCNTs on allergen-induced airway inflammation and fibrosis. We hypothesized that inhalation pre-exposure to MWCNTs would render mice susceptible to developing allergic lung disease induced by house dust mite (HDM) allergen. Methods: Male B6C3F1/N mice were exposed by whole-body inhalation for 6 h a day, 5 d a week, for 30 d to air control or 0.06, 0.2, and 0.6 mg/m 3 of MWCNTs. The exposure atmospheres were agglomerates (1.4-1.8 µm) composed of MWCNTs (average diameter 16 nm; average length 2.4 µm; 0.52% Ni). Mice then received 25 µg of HDM extract by intranasal instillation 6 times over 3 weeks. Necropsy was performed at 3 and 30 d after the final HDM dose to collect serum, bronchoalveolar lavage fluid (BALF), and lung tissue for histopathology. Results: MWCNT exposure at the highest dose inhibited HDM-induced serum IgE levels, IL-13 protein levels in BALF, and airway mucus production. However, perivascular and peribronchiolar inflammatory lesions were observed in the lungs of mice at 3 d with MWCNT and HDM, but not MWCNT or HDM alone. Moreover, combined HDM and MWCNT exposure increased airway fibrosis in the lungs of mice. Conclusions: Inhalation pre-exposure to MWCNTs inhibited HDM-induced TH2 immune responses, yet this combined exposure resulted in vascular inflammation and airway fibrosis, indicating that MWCNT pre-exposure alters the immune response to allergens.

ortho-Phthalaldehyde (OPA) is a high-level chemical disinfectant that is commonly used for chemical sterilization of dental and medical instruments as an alternative to glutaraldehyde, a known skin and respiratory sensitizer. Concern for safe levels of human exposure remains due to a lack of toxicity data as well as human case reports of skin and respiratory sensitization following OPA exposure. The present study evaluated the inhalational toxicity of OPA in Harlan Sprague-Dawley rats and B6C3F1/N mice. Groups of 10 male and female rats and mice were exposed to OPA by whole-body inhalation for 3 months at concentrations of 0 (control), 0.44, 0.88, 1.75, 3.5, or 7.0 ppm. Rats and mice developed a spectrum of lesions at sites of contact throughout the respiratory tract (nose, larynx, trachea, lung), as well as in the skin and eye, consistent with a severe irritant response. In general, histologic lesions (necrosis, inflammation, regeneration, hyperplasia and metaplasia) occurred at deeper sites within the respiratory tract with increasing exposure concentration. As a first site of contact, the nose exhibited the greatest response to OPA exposure and resulted in an increased incidence, severity and variety of lesions compared to a previous study of glutaraldehyde exposure at similar exposure concentrations. This increased response in the nasal cavity, combined with extensive lesions throughout the respiratory tract, provides concern for use of OPA as a replacement for glutaraldehyde as a high-level disinfectant.

C60 fullerene (C60), or buckminsterfullerene, is a spherical arrangement of 60 carbon atoms, having a diameter of approximately 1 nm, and is produced naturally as a by-product of combustion. Due to its small size, C60 has attracted much attention for use in a variety of applications; however, insufficient information is available regarding its toxicological effects. The effects on respiratory toxicity and immunotoxicity of C60 aggregates (50 nm [nano-C60] and 1 μm [micro-C60] diameter) were examined in B6C3F1/N mice and Wistar Han rats after nose-only inhalation for 13 weeks. Exposure concentrations were selected to allow for data evaluations using both mass-based and particle surface area-based exposure metrics. Nano-C60 exposure levels selected were 0.5 and 2 mg/m 3 (0.033 and 0.112 m 2 /m 3 ), while micro-C60 exposures were 2, 15 and 30 mg/m 3 (0.011, 0.084 and 0.167 m 2 /m 3 ). There were no systemic effects on innate, cell-mediated, or humoral immune function. Pulmonary inflammatory responses (histiocytic infiltration, macrophage pigmentation, chronic inflammation) were concentration-dependent and corresponded to increases in monocyte chemoattractant protein (MCP)-1 (rats) and macrophage inflammatory protein (MIP)-1α (mice) in bronchoalveolar lavage (BAL) fluid. Lung overload may have contributed to the pulmonary inflammatory responses observed following nano-C60 exposure at 2 mg/m 3 and micro-C60 exposure at 30 mg/m 3 . Phenotype shifts in cells recovered from the BAL were also observed in all C60-exposed rats, regardless of the level of exposure. Overall, more severe pulmonary effects were observed for nano-C60 than for micro-C60 for mass-based exposure comparisons. However, for surface-area-based exposures, more severe pulmonary effects were observed for micro-C60 than for nano-C60, highlighting the importance of dosimetry when evaluating toxicity between nano- and microparticles., Competing Interests: Declaration of Interest This work was supported [in part] by the Intramural Research Program of the National Institutes of Health (NIH), National Institute of Environmental Health Sciences (NIEHS) and by NTP Contracts N01-ES-55538 and N01-ES-5553.

Post-harvest Processing (PHP) methods are viable food processing methods employed to reduce human pathogens in molluscan shellfish that would normally be consumed raw, such as raw oysters on the half-shell. Efficacy of human pathogen reduction associated with PHP varies with respect to time, temperature, salinity, pressure, and process exposure. Regulatory requirements and PHP molluscan shellfish quality implications are major considerations for PHP usage. Food safety impacts associated with PHP of molluscan shellfish vary in their efficacy and may have synergistic outcomes when combined. Further research for many PHP methods are necessary and emerging PHP methods that result in minimal quality loss and effective human pathogen reduction should be explored.

C60 fullerenes (C60) are spherical structures consisting of 60 carbon atoms that are generated via combustion from both natural and anthropogenic sources. C60 are also synthesized intentionally for industrial applications. Individual C60 structures have an approximate diameter of 1nm; however, C60 readily forms aggregates and typically exist as larger particles that range from nanometers to micrometers in diameter. In this report, lung and extrapulmonary tissue deposition and lung clearance of C60 nanoparticles (nano-C60, 50nm) and microparticles (micro-C60, 1μm) were examined in Wistar Han rats and B6C3F1/N mice after nose-only inhalation for 90 days. Exposure concentrations were 0.5 and 2mg/m(3) (nano-C60) and 2, 15, and 30mg/m(3) (micro-C60). For both C60 particle sizes, the C60 lung burden increased proportionally to exposure concentration. The C60 lung burden was greater in both species at all time points following exposure to nano-C60 particle exposure compared to micro-C60 exposure at the common exposure concentration 2mg/m(3). The calculated C60 particle lung retention half-times were similar for both nano-C60 and micro-C60 exposure at 2mg/m(3) in male mice (15-16 days). In contrast, in male rats, the half-time of C60 particles following nano-C60 exposure (61 days) was roughly twice as long as the half-time following micro-C60 exposure (27 days) at the same exposure concentration (2mg/m(3)) and was similar to the clearance following micro-C60 exposure at higher exposure concentrations (15 and 30mg/m(3)). C60 was detected in bronchial lymph nodes but the burden was not quantified due to the high variability in the data. C60 concentrations were below the experimental limit of quantitation (ELOQ) in liver, spleen, blood, brain and kidney tissues. These tissue burden data provide information for comparison between nanometer and micrometer sized C60 particle exposure and will aid in the interpretation of toxicity data., (Published by Elsevier Ireland Ltd.)

Surface initiated atom transfer radical polymerization (ATRP) of substituted styrenes leads to rapid synthesis of uniform and thick substituted polystyrene brushes (>100 nm in 1 hour) from gold surface. High growth rates were observed for styrenes substituted with electron withdrawing groups in meta/para positions. The effects seen in surface and solution polymerizations are similar for styrenes with electron withdrawing groups, and for electron donors in ortho and para positions. However, electron donors at meta sites have surprisingly fast growth rates, which may be due to steric inhibition of termination. The overall surface polymerization rates for substituted styrenes was analyzed and found to follow the Hammett relation with ρ = 0.51. The ratio of k p to k t , is as an indicator of the likelihood that a reaction will reach high degrees of polymerization before termination.

A composite lithium electrolyte composed of polyelectrolyte-grafted nanoparticles and polyethylene glycol dimethyl ether (PEGDME) is synthesized and characterized. Polyanions immobilized by the silica nanoparticles have reduced anion mobility. Composite nanoparticles grafted by poly(lithium 4-styrenesulfonate) only have moderate conductivity at 60 °C. Almost an order increase of the conductivity to ∼10(-6) S/cm is achieved by co-polymerization of the poly(ethylene oxide) methacrylate with sodium 4-styrenesulfonate, which enhances dissociation between lithium cation and polyanion and facilitates lithium ion transfer from the inner part of the polyelectrolyte layer. This composite electrolyte has the potential to suppress lithium dendrite growth and enable the use of lithium metal anode in rechargeable batteries.

Occupational exposure to cobalt is of widespread concern due to its use in a variety of industrial processes and the occurrence of occupational disease. Due to the lack of toxicity and carcinogenicity data following exposure to cobalt, and questions regarding bioavailability following exposure to different forms of cobalt, the NTP conducted two chronic inhalation exposure studies in rats and mice, one on soluble cobalt sulfate heptahydrate, and a more recent study on insoluble cobalt metal. Herein, we compare and contrast the toxicity profiles following whole-body inhalation exposures to these two forms of cobalt. In general, both forms were genotoxic in the Salmonella T98 strain in the absence of effects on micronuclei. The major sites of toxicity and carcinogenicity in both chronic inhalation studies were the respiratory tract in rats and mice, and the adrenal gland in rats. In addition, there were distinct sites of toxicity and carcinogenicity noted following exposure to cobalt metal. In rats, carcinogenicity was observed in the blood, and pancreas, and toxicity was observed in the testes of rats and mice. Taken together, these findings suggest that both forms of cobalt, soluble and insoluble, appear to be multi-site rodent carcinogens following inhalation exposure., (Published by Elsevier Ireland Ltd.)

A new class of clickable and biodegradable polylactide was designed and prepared via bulk polymerization of 3,6-dipropargyloxymethyl-1,4-dioxane-2,5-dione ( 1 ) which was synthesized from easily accessible propargyloxylactic acid ( 5 ). A homopolymer of 1 and random copolymer of 1 with l-lactide were obtained as amorphous materials and exhibit low T g of 8.5 and 34 °C, respectively, indicating their promising potentials for biomedical applications. The statistical nature of random copolymers was investigated by DSC analysis and 13 C NMR spectroscopy, which implies the random distribution of terminal alkyne groups along the back bone of copolymers. The efficient click post-modification of this new class of polylactide with alkyl and mPEG azides affords novel hydrophilic biomaterials, which exhibit reversible thermo-responsive properties as evidenced by their tunable LCST ranging from 22 to 69 °C depending on the balance of the incorporated hydrophilic/hydrophobic side chains. These results indicate the generality of this new class of clickable polylactide in preparing novel smart biomaterials in a simple and efficient manner via click chemistry.

A new simple and practical protocol for scalable synthesis of a novel library of propargylated and PEGylated α-hydroxy acids toward the preparation of "clickable" polylactides was described. The overall synthesis starting from readily available propargyl alcohol, bromoacetaldehyde diethyl acetal, and OEGs or PEGs was developed as a convenient procedure with low cost and no need of column chromatographic purification. The terminal alkyne functionality survives from hydrolysis of the corresponding easily accessible cyanohydrin derivatives in methanolic sulfuric acid. Facile desymmetrization, monofunctionalization, and efficient chain-elongation coupling of OEGs further enable the incorporation of OEGs to α-hydroxy acids in a simple and efficient manner. At the end, synthesis of allyloxy lactic acid indicates that an alkene group is also compatible with the developed method.

Engineered nanoparticles are widely used in commercial products, and yet due to the paucity of safety information, there are concerns surrounding potential adverse health effects, especially from inhaled nanoparticles and their putative contribution to allergic airway disease. The objective of this study was to investigate whether size or surface chemistry of engineered nanoparticles can influence the immune enhancing properties of these agents on antigen-specific T cell responses. Ovalbumin (OVA)-derived peptides were presented to T cells by either spleen-derived endogenous antigen presenting cells or a mouse dendritic cell (DC) line, DC2.4. In all models, interferon (IFN)-γ and interleukin (IL)-2 production by CD8(+) or CD4(+) T cells in response to peptide OVA257-264 or OVA323-339, respectively, was measured by flow cytometry. To address the study objective, silica nanoparticles (SNPs) were modified with alkyne-terminated surfaces and appended with polyethylene glycol chains via "click" chemistry. These modified SNPs were resistant to agglomerate in in vitro culture media, suggesting that their modulation of T cell responses is the result of true nanoscale-mediated effects. Under conditions of suboptimal T-cell activation, modified SNPs (up to 10 µg/ml) enhanced the proportion of CD8(+), but not CD4(+), T cells producing IFN-γ and IL-2. Various functional groups (-COOH, -NH2 and -OH) on modified SNPs enhanced IFN-γ and IL-2 production to different levels, with -COOH SNPs being the most effective. Furthermore, 51 nm -COOH SNPs exhibited a greater enhancing effect on the CD8(+) T cell response than other sized particles. Collectively, our results show that modified SNPs can enhance antigen-specific CD8(+) T cell responses, suggesting that certain modified SNPs exhibit potential adjuvant-like properties.

2-Hydroxy-4-pentynoic acid (1) is a key intermediate towards 'clickable' polylactide which allows for efficient introduction of a broad range of pendant functional groups onto polymers from a single monomer via convenient 'click' chemistry with organic azides. The incorporation of various pendant functional groups could effectively tailor the physicochemical properties of polylactide. The reported synthesis of 1 started from propargyl bromide and ethyl glyoxylate. However, both of starting materials are expensive and unstable; especially, propargyl bromide is shock-sensitive and subjected to thermal explosive decomposition, which makes the preparation of 1 impractical with high cost and high risk of explosion. Herein, we report a simple, economical and safe synthetic route to prepare 1 using cheap and commercially available diethyl 2-acetamidomalonate (4) and propargyl alcohol. The desired product 1 was obtained via alkylation of malonate 4 with propargyl tosylate followed by a one-pot four-step sequence of hydrolysis, decarboxylation, diazotization and hydroxylation of propargylic malonate 5 without work-up of any intermediate.

Engineered nanomaterials (ENM) have desirable properties that make them well suited for many commercial applications. However, a limited understanding of how ENM's properties influence their molecular interactions with biomembranes hampers efforts to design ENM that are both safe and effective. This paper describes the use of a tethered bilayer lipid membrane (tBLM) to characterize biomembrane disruption by functionalized silica-core nanoparticles. Electrochemical impedance spectroscopy was used to measure the time trajectory of tBLM resistance following nanoparticle exposure. Statistical analysis of parameters from an exponential resistance decay model was then used to quantify and analyze differences between the impedance profiles of nanoparticles that were unfunctionalized, amine-functionalized, or carboxyl-functionalized. All of the nanoparticles triggered a decrease in membrane resistance, indicating nanoparticle-induced disruption of the tBLM. Hierarchical clustering allowed the potency of nanoparticles for reducing tBLM resistance to be ranked in the order amine>carboxyl~bare silica. Dynamic light scattering analysis revealed that tBLM exposure triggered minor coalescence for bare and amine-functionalized silica nanoparticles but not for carboxyl-functionalized silica nanoparticles. These results indicate that the tBLM method can reproducibly characterize ENM-induced biomembrane disruption and can distinguish the BLM-disruption patterns of nanoparticles that are identical except for their surface functional groups. The method provides insight into mechanisms of molecular interaction involving biomembranes and is suitable for miniaturization and automation for high-throughput applications to help assess the health risk of nanomaterial exposure or identify ENM having a desired mode of interaction with biomembranes., (© 2013. Published by Elsevier B.V. All rights reserved.)

Layer-by-layer adsorption of protonated poly(allylamine) (PAH) and deprotonated poly(N,N-dicarboxymethylallylamine) (PDCMAA) yields thick films with a high density of iminodiacetic acid (IDA) ligands that bind metal ions. When film deposition occurs at pH 3.0, PAH/PDCMAA bilayer thicknesses reach 200 nm, and Cu(2+) binding capacities are ~2.5 mmol per cm(3) of film. (PAH/PDCMAA)10 films deposited at pH 3.0 are 4-8-fold thicker than films formed at pH 5.0, 7.0, or 9.0, presumably because of the low charge density on PDCMAA chains at pH 3.0. However, with normalization to film thickness, all films bind similar amounts of Cu(2+) from pH 4.1 solutions of CuSO4. In micrometer-thick films, equilibration of binding sites with Cu(2+) requires ~4 h due to a low Cu(2+) diffusion coefficient (~2.6 × 10(-12) cm(2)/s). Sorption isotherms determined at several temperatures show that Cu(2+) binding is endothermic with a positive entropy (binding constants increase with increasing temperature), presumably because metal-ion complexation involves displacement of both a proton from IDA and water molecules from Cu(2+). (PAH/PDCMAA)10 films retain their binding capacity over four absorption/elution cycles and may prove useful in metal-ion scavenging, catalysis, and protein binding.

Background: With the increase in production and use of engineered nanoparticles (NP; ≤ 100 nm), safety concerns have risen about the potential health effects of occupational or environmental NP exposure. Results of animal toxicology studies suggest that inhalation of NP may cause pulmonary injury with subsequent acute or chronic inflammation. People with chronic respiratory diseases like asthma or allergic rhinitis may be even more susceptible to toxic effects of inhaled NP. Few studies, however, have investigated adverse effects of inhaled NP that may enhance the development of allergic airway disease., Methods: We investigated the potential of polyethylene glycol coated amorphous silica NP (SNP; 90 nm diameter) to promote allergic airway disease when co-exposed during sensitization with an allergen. BALB/c mice were sensitized by intranasal instillation with 0.02% ovalbumin (OVA; allergen) or saline (control), and co-exposed to 0, 10, 100, or 400 μg of SNP. OVA-sensitized mice were then challenged intranasally with 0.5% OVA 14 and 15 days after sensitization, and all animals were sacrificed a day after the last OVA challenge. Blood and bronchoalveolar lavage fluid (BALF) were collected, and pulmonary tissue was processed for histopathology and biochemical and molecular analyses., Results: Co-exposure to SNP during OVA sensitization caused a dose-dependent enhancement of allergic airway disease upon challenge with OVA alone. This adjuvant-like effect was manifested by significantly greater OVA-specific serum IgE, airway eosinophil infiltration, mucous cell metaplasia, and Th2 and Th17 cytokine gene and protein expression, as compared to mice that were sensitized to OVA without SNP. In saline controls, SNP exposure did cause a moderate increase in airway neutrophils at the highest doses., Conclusions: These results suggest that airway exposure to engineered SNP could enhance allergen sensitization and foster greater manifestation of allergic airway disease upon secondary allergen exposures. Whereas SNP caused innate immune responses at high doses in non-allergic mice, the adjuvant effects of SNP were found at lower doses in allergic mice and were Th2/Th17 related. In conclusion, these findings in mice suggest that individuals exposed to SNP might be more prone to manifest allergic airway disease, due to adjuvant-like properties of SNP.

Hole-conducting silica/polymer nanocomposites exhibit interesting physical and chemical properties with important applications in the field of energy storage and hybrid solar cells. Although the conventional strategy of grafting hole-conducting polymer onto the surface of silica nanoparticles is to use in situ oxidative polymerization, a promising alternative of using surface-initiated controlled living radical polymerization has arisen to anchor the polymer on the silica. The resulting silica/polymer nanocomposites from the latter method are more chemically and thermally stable because of the strong covalent bonding compared to the electrostatic interaction from in situ polymerization. The use of these nanocomposites mixed with spiro-MeOTAD (2,2',7,7'-tetrakis(N,N-di-p-methoxyphenylamine)-9,9'-spirobifluorene) as a new hole conductor in the application of solid-state dye-sensitized solar cell (ss-DSSC) is reported here. The power conversion efficiency of this ss-DSSC is higher than the full spiro-MeOTAD ss-DSSC. Notably, the short circuit current improves by 26%. It is explained by large size silica/polymer nanocomposites forming an additional light scattering layer on the top of photoanode. This is the first time a conductive light scattering layer is introduced into ss-DSSC to enhance cell performance.

In principle, incorporation of comb-like block copolymers in multilayer polyelectrolyte films can both increase film thickness relative to coatings containing linear polymers and provide more swollen films for increased sorption of proteins. In the absence of added salt, alternating adsorption of 5 bilayers of protonated poly(allylamine) (PAH) and comb-like poly(2-hydroxyethyl methacrylate)-graft-poly(acrylic acid) (PHEMA-g-PAA) leads to ∼2-fold thicker coatings than adsorption of PAH and linear PAA, and the difference in the thicknesses of the two coatings increases with the number of bilayers. Moreover, the (PAH/PHEMA-g-PAA)n films sorb 2- to 4-fold more protein than corresponding films prepared with linear PAA, and coatings deposited at pH 3.0 sorb more protein than coatings adsorbed at pH 5.0, 7.0, or 9.0. In fact changes in deposition pH and addition of 0.5 M NaCl to polyelectrolyte adsorption solutions alter protein sorption more dramatically than variations in the constituent polymer architecture. When deposited from 0.5 M NaCl at pH 3.0, both (PAH/PHEMA-g-PAA)5 and (PAH/PAA)5 films increase in thickness more than 400% upon adsorption of lysozyme. These films contain a high concentration of free -COOH groups, and subsequent deprotonation of these groups at neutral pH likely contributes to increased protein binding. Lysozyme sorption stabilizes these films, as without lysozyme films deposited at pH 3.0 from 0.5 M NaCl desorb at neutral pH. Films deposited at pH 9.0 from 0.5 M NaCl are more stable and also bind large amounts of lysozyme. The high binding capacities of these films make them attractive for potential applications in protein isolation or immobilization of enzymes.

Azidopropyl methacrylate (AzPMA), a functional monomer with a pendent azido group, polymerizes from surfaces and provides polymer brushes amenable to subsequent elaboration via click chemistry. In DMF at 50 °C, click reactions between poly(AzPMA) brushes and an alkynylated dye proceed with >90% conversion in a few minutes. However, in aqueous solutions, reaction with an alkyne-containing poly(ethylene glycol) methyl ether (mPEG, M n =5000) gives <10% conversion after a 12-h reaction at room temperature. Formation of copolymers with AzPMA and polyethylene glycol methyl ether methacrylate (mPEGMA) enables control over the hydrophilicity and functional group density in the copolymer to increase the yield of aqueous click reactions. The copolymers show reaction efficiencies as high as 60%. These studies suggest that for aqueous applications such as bioconjugation via click chemistry, control over brush hydrophilicity is vital.

Layer-by-layer polyelectrolyte adsorption is a simple, convenient method for introducing ion-exchange sites in porous membranes. This study demonstrates that adsorption of poly(acrylic acid) (PAA)-containing films at pH 3 rather than pH 5 increases the protein-binding capacity of such polyelectrolyte-modified membranes 3-6-fold. The low adsorption pH generates a high density of -COOH groups that function as either ion-exchange sites or points for covalent immobilization of metal-ion complexes that selectively bind tagged proteins. When functionalized with nitrilotriacetate (NTA)-Ni(2+) complexes, membranes containing PAA/polyethylenimine (PEI)/PAA films bind 93 mg of histidine(6)-tagged (His-tagged) ubiquitin per cm(3) of membrane. Additionally these membranes isolate His-tagged COP9 signalosome complex subunit 8 from cell extracts and show >90% recovery of His-tagged ubiquitin. Although modification with polyelectrolyte films occurs by simply passing polyelectrolyte solutions through the membrane for as little as 5 min, with low-pH deposition the protein binding capacities of such membranes are as high as for membranes modified with polymer brushes and 2-3-fold higher than for commercially available immobilized metal affinity chromatography (IMAC) resins. Moreover, the buffer permeabilities of polyelectrolyte-modified membranes that bind His-tagged protein are ~30% of the corresponding permeabilities of unmodified membranes, so protein capture can occur rapidly with low-pressure drops. Even at a solution linear velocity of 570 cm/h, membranes modified with PAA/PEI/PAA exhibit a lysozyme dynamic binding capacity (capacity at 10% breakthrough) of ~40 mg/cm(3). Preliminary studies suggest that these membranes are stable under depyrogenation conditions (1 M NaOH).

Microporous membranes are attractive for protein purification because convection rapidly brings proteins to binding sites. However, the low binding capacity of such membranes limits their applications. This work reports a rapid, aqueous procedure to create highly permeable, polymer brush-modified membranes that bind large amounts of protein. The synthetic method includes a 10-min adsorption of a macroinitiator in a hydroxylated nylon membrane and a subsequent 5-min aqueous atom transfer radical polymerization of 2-(methacryloyloxy)ethyl succinate from the immobilized initiator to form poly(acid) brushes. This procedure likely leads to more swollen, less dense brushes than polymerization from silane initiators, and thus requires less polymer to achieve the same binding capacity. The hydraulic permeability of the poly(acid) membranes is 4-fold higher than that of similar membranes prepared by growing brushes from immobilized silane initiators. These brush-containing nylon membranes bind 120 mg/cm(3) of lysozyme using solution residence times as short as 35 ms, and when functionalized with nitrilotriacetate (NTA)-Ni(2+) complexes, they capture 85 mg/cm(3) of histidine(6)-tagged (His-tagged) Ubiquitin. Additionally the NTA-Ni(2+)-functionalized membranes isolate His-tagged myo-inositol-1-phosphate synthase directly from cell extracts and show >90% recovery of His-tagged proteins.

Polymer brushes orthogonally derivatized with oxotitanium and nitrilotriacetate-Fe(III) groups enrich both mono- and multi-phosphorylated peptides for mass spectrometry analysis.

Atom transfer radical polymerization (ATRP) is commonly used to grow polymer brushes from Au surfaces, but the resulting film thicknesses are usually significantly less than with ATRP from SiO(2) substrates. On Au, growth of poly(methyl methacrylate) (PMMA) blocks from poly(tert-butyl acrylate) brushes occurs more rapidly than growth of PMMA from initiator monolayers, suggesting that the disparity between growth rates from Au and SiO(2) stems from the Au surface. Radical quenching by electron transfer from Au is probably not the termination mechanism because polymerization from thin, cross-linked initiators gives film thicknesses that are essentially the same as the thicknesses of films grown from SiO(2) under the same polymerization conditions. However, this result is consistent with termination through desorption of thiols from noncross-linked films, and reaction of these thiols with growing polymer chains. The enhanced stability of cross-linked initiators allows ATRP at temperatures up to ∼100 °C and enables the growth of thick films of PMMA (350 nm), polystyrene (120 nm) and poly(vinyl pyridine) (200 nm) from Au surfaces in 1 h. At temperatures >100 °C, the polymer brush layers delaminate as large area films.

Growth of poly(2-hydroxyethyl methacrylate) brushes on magnetic nanoparticles and subsequent brush functionalization with nitrilotriacetate-Ni(2+) yield magnetic beads that selectively capture polyhistidine-tagged (His-tagged) protein directly from cell extracts. Transmission electron microscopy, Fourier transform infrared (FT-IR) spectroscopy, thermogravimetric analysis, and magnetization measurements confirm and quantify the formation of the brushes on magnetic particles, and multilayer protein adsorption to these brushes results in binding capacities (220 mg BSA/g of beads and 245 mg His-tagged ubiquitin/g of beads) that are an order of magnitude greater than those of commercial magnetic beads. Moreover, the functionalized beads selectively capture His-tagged protein within 5 min. The high binding capacity and protein purity along with efficient protein capture in a short incubation time make brush-modified particles attractive for purification of recombinant proteins.

Clinical applications of genetic therapies, including delivery of short, interfering RNAs (siRNAs) for RNA interference (RNAi), are limited due to the difficulty of delivering nucleic acids to specific cells of interest while at the same time minimizing toxicity and immunogenicity. The use of cationic polymers to deliver nucleic acid therapeutics has the potential to address these complex issues but is currently limited by low-delivery efficiencies. Although cell culture studies have shown that some polymers can be used to deliver siRNAs and achieve silencing, it is still not clear what physical or chemical properties are needed to ensure that the polymers form active polymer-siRNA complexes. In this study, we used multicolor fluorescence confocal microscopy to analyze the cellular uptake of siRNAs delivered by novel propargyl glycolide polymeric nanoparticles (NPs). Delivery by these vehicles was compared with delivery by linear polyethyleneimine (LPEI) and Lipofectamine 2000 (LF2K), which are both known as effective delivery vehicles for siRNAs. Our results showed that when LF2K and LPEI were used, large quantities of siRNA were delivered rapidly, presumably overwhelming the basal levels of mRNA to initiate silencing. In contrast, our novel polymeric NPs showed delivery of siRNAs but at concentrations that were initially too low to achieve silencing. Nonetheless, the exceptionally low cytotoxicity of our NPs, and the simplicity with which they can be modified, makes them good candidates for further study to optimize their delivery profiles and, in turn, achieve efficient silencing.

Asthma is a leading cause of morbidity in children. Risk factors include chronic exposure to allergens and air pollution. While chronically activated mast cells contribute to the pathophysiology of asthma in part through their proteases such as chymase and tryptase, previous studies of airway mast cell abundance and distribution in asthmatics have been inconsistent. To determine whether repeated episodic exposures to environmental pollutants during postnatal lung development alter airway mast cell abundance and distribution, we exposed infant rhesus monkeys to a known human allergen, house dust mite antigen (HDMA), and/or a known environmental pollutant, ozone (O(3)), and quantitatively compared the abundance of tryptase- or chymase-positive mast cells in three airway levels. Mast cells are resident in multiple compartments of the airway wall in infant rhesus monkeys raised from birth in filtered air. Tryptase- and chymase-positive cells were most abundant in trachea and least in terminal bronchioles. The majority of tryptase-positive and almost all chymase-positive cells were in extracellular matrix and smooth muscle bundles. Chronic exposure to HDMA elevated the abundance of both tryptase- and chymase-positive cells in the trachea and intrapulmonary bronchi. Neither exposure to O(3) nor HDMA + O(3) increased mast cell accumulations in the airway wall. We conclude that during postnatal airway development (1) mast cells are a resident airway cell population even in the absence of toxic air contaminants; (2) aeroallergen exposure alters large airway mast cell distribution and abundance, increasing chymase-positive mast cells; and (3) this response is attenuated by exposure to oxidant air pollutants.

Porous nylon membranes modified with poly(acid) brushes and their derivatives can rapidly purify proteins via ion-exchange and metal-ion affinity interactions. Membranes containing poly(2-(methacryloyloxy)ethyl succinate) (poly(MES)) brushes bind 118 +/- 8 mg of lysozyme per cm(3) of membrane and facilitate purification of lysozyme from chicken egg white. Moreover, functionalization of the poly(MES) brushes with nitrilotriacetate (NTA)-Ni(2+) complexes yields membranes that bind poly(histidine)-tagged (His-tagged) ubiquitin with a capacity of 85 +/- 2 mg of protein per cm(3) of membrane. Most importantly, the membranes modified with poly(MES)-NTA-Ni(2+) allow isolation of His-tagged cellular retinaldehyde-binding protein directly from a cell extract in <10 min, and the protein purity is comparable to that achieved with commercial affinity columns. Therefore, porous nylon membranes containing functionalized poly(MES) brushes are attractive candidates for rapid, high-capacity purification of His-tagged proteins from cell extracts.

This review examines the application of polymer brush-modified flat surfaces, membranes, and beads for protein immobilization and isolation. Modification of porous substrates with brushes yields membranes that selectively bind tagged proteins to give 99% pure protein at capacities as high as 100 mg of protein per cubic centimeter of membrane. Moreover, enrichment of phosphopeptides on brush-modified matrix-assisted laser desorption/ionization (MALDI) plates allows detection and characterization of femtomole levels of phosphopeptides by MALDI mass spectrometry. Because swollen hydrophilic brushes can resist nonspecific protein adsorption while immobilizing a high density of proteins, they are attractive as substrates for protein microarrays. This review highlights the advantages of polymer brush-modified surfaces over self-assembled monolayers and identifies some research needs in this area.

Over the last 15 years, the layer-by-layer deposition of polyelectrolytes and the growth of polymer brushes from surfaces have become established techniques for the formation of a wide range of thin films. This article discusses the use of these techniques in creating the skin layer of nanofiltration or gas-separation membranes and in functionalizing the interior of membranes for protein adsorption or catalysis. In the case of separation membranes for nanofiltration, the minimal thickness of layer-by-layer films allows for high flux, and the wide range of available polyelectrolytes that can form these films permits the tailoring of membranes for separations such as water softening, the reduction of F (-) concentrations, and the removal of dyes from wastewater. For gas separation, polymers grown from surfaces are more attractive than layer-by-layer coatings because most polyelectrolyte films are not highly gas-selective. Cross-linked poly(ethylene glycol dimethacrylate) films grown from porous alumina exhibit CO(2)/CH(4) selectivities of around 20, and the careful selection of monomers should further improve the selectivity of similar membranes. Both layer-by-layer methods and polymer brushes can also be employed to modify the interior of membranes, and we have utilized these techniques to create catalysts, antibody arrays in membranes, and membrane absorbers for protein purification. Polymer brushes are particularly attractive because they allow the absorption of multilayers of protein to yield membranes with binding capacities as high as 150 mg protein/cm(3). Some challenges in the practical implementation of these systems, such as the economical formation of membranes using highly permeable polymeric supports, and future directions in research on membrane modification with multilayer films and polymer brushes are also discussed herein.