High-resolution three-dimensional imaging of topological textures in nanoscale single-diamond networks.

Topological defects-extended lattice deformations that are robust against local defects and annealing-have been exploited to engineer novel properties in both hard and soft materials. Yet, their formation kinetics and nanoscale three-dimensional structure are poorly understood, impeding their benefits for nanofabrication. We describe the fabrication of a pair of topological defects in the volume of a single-diamond network (space group Fd 3 ¯ m) templated into gold from a triblock terpolymer crystal. Using X-ray nanotomography, we resolve the three-dimensional structure of nearly 70,000 individual single-diamond unit cells with a spatial resolution of 11.2 nm, allowing analysis of the long-range order of the network. The defects observed morphologically resemble the comet and trefoil patterns of equal and opposite half-integer topological charges observed in liquid crystals. Yet our analysis of strain in the network suggests typical hard matter behaviour. Our analysis approach does not require a priori knowledge of the expected positions of the nodes in three-dimensional nanostructured systems, allowing the identification of distorted morphologies and defects in large samples.

Correction: Expanding analytical tools for characterizing ultrasmall silica-based nanoparticles.

[This corrects the article DOI: 10.1039/C7RA01349C.].

Expanding Analytical Tools for Characterizing Ultrasmall Silica-based Nanoparticles.

C' dots are fluorescent inorganic-organic hybrid nanoparticles synthesized in water comprised of a silica core with a covalently embedded near infrared dye, and a polyethylene glycol (PEG) outer layer. C' dots containing the integrin specific ligand, cycloRGDyC, are the first of their kind particles approved for human clinical trials. In the continued clinical development of these nanoparticles, high-resolution analytical approaches are needed. Here we investigate the use of reversed phase high performance liquid chromatography (RP-HPLC) to analyze cycloRGDyC-Cy5-C' dots. Given the stability and protein-like size, we reasoned that these nanoparticles would be compatible under RP-HPLC conditions typically used to characterize peptides and proteins. Our results show that RP-HPLC provides excellent resolution, showing significant heterogeneity of these nanoparticles. C' dots also exhibit unusual peak profiles where RP-HPLC chromatogram peak shapes change from run to run, possibly due to the conformational heterogeneity or charge distribution of the particle surface due to the PEG groups. In addition we describe a novel thiol-mediated release of C' dot ligands to directly estimate cycloRGDyC by exposing the particles to organic thiols. Ligand release is presumably afforded by a reverse Michael reaction mechanism.

Allergic sensitization to pegylated interferon-α results in drug eruptions.

BACKGROUND: The introduction of pegylated interferon (PEG-IFN)-α in the treatment of chronic hepatitis C has led to an increase in sustained virological response. Despite reduced immunogenicity of the pegylated form in comparison with native interferon (IFN)-α, a high frequency of adverse cutaneous reactions has been reported with pegylated IFN-α. Here, we aimed to investigate the immunological mechanisms underlying pegylated IFN-α-induced drug eruptions. METHODS: Hepatitis C patients suffering from drug eruptions in association with administration of pegylated interferons were enrolled in the study (n = 22). Subjects were tested for sensitivity to pegylated IFN-α2a , pegylated IFN-α2b , or ribavirin using intradermal, scratch, and/or patch tests, as well as lymphocyte activation tests (LATs). Skin biopsies obtained from pegylated IFN-α-associated exanthemas, as well as from localized inflammatory skin reactions at pegylated IFN-α injection sites, were analyzed for the expression of relevant chemokines by quantitative real-time PCR and immunohistochemistry. RESULTS: A subset of patients suffering from pegylated IFN-α-associated exanthemas displayed positive intradermal tests to PEG-IFNs but not to conventional IFN (11/22). In selected patients, this observation correlated with the presence of pegylated IFN-specific T cells (3/11). Chemokine profiles of inflammatory skin reactions at the injection sites reflected an IFN-α-signature, whereas lesional skin of exanthemas showed induction of TH2-associated chemokines. CONCLUSIONS: Our results indicate that specific sensitizations are one cause of exanthemas under therapy with PEG-IFNs. Clinical proof-of-concept analyses demonstrate that affected patients may benefit from a switch to conventional, nonpegylated drugs, enabling IFN-α therapy continuation without drug-associated skin eruptions.

Demonstration of a spaser-based nanolaser.

One of the most rapidly growing areas of physics and nanotechnology focuses on plasmonic effects on the nanometre scale, with possible applications ranging from sensing and biomedicine to imaging and information technology. However, the full development of nanoplasmonics is hindered by the lack of devices that can generate coherent plasmonic fields. It has been proposed that in the same way as a laser generates stimulated emission of coherent photons, a 'spaser' could generate stimulated emission of surface plasmons (oscillations of free electrons in metallic nanostructures) in resonating metallic nanostructures adjacent to a gain medium. But attempts to realize a spaser face the challenge of absorption loss in metal, which is particularly strong at optical frequencies. The suggestion to compensate loss by optical gain in localized and propagating surface plasmons has been implemented recently and even allowed the amplification of propagating surface plasmons in open paths. Still, these experiments and the reported enhancement of the stimulated emission of dye molecules in the presence of metallic nanoparticles lack the feedback mechanism present in a spaser. Here we show that 44-nm-diameter nanoparticles with a gold core and dye-doped silica shell allow us to completely overcome the loss of localized surface plasmons by gain and realize a spaser. And in accord with the notion that only surface plasmon resonances are capable of squeezing optical frequency oscillations into a nanoscopic cavity to enable a true nanolaser, we show that outcoupling of surface plasmon oscillations to photonic modes at a wavelength of 531 nm makes our system the smallest nanolaser reported to date-and to our knowledge the first operating at visible wavelengths. We anticipate that now it has been realized experimentally, the spaser will advance our fundamental understanding of nanoplasmonics and the development of practical applications.

Mesophase structure-mechanical and ionic transport correlations in extended amphiphilic dendrons.

We have studied the self-assembly of amphiphilic dendrons extended with linear polyethylene oxide (PEO) chains and their ion complexes. Keeping the dendron core and linear PEO chain compatible allows for the combination of dendritic core-shell and conventional blockcopolymer characteristics for complex mesophase behavior. An unexpected sequence of crystalline lamellar, cubic micellar (Pm3n), hexagonal columnar, continuous cubic (Ia3d), and lamellar mesophases is observed. Multiple phase behavior within single compounds allows for the study of charge transport and mechanical property correlations as a function of structure. The results suggest an advanced molecular design concept for the next generation of nanostructured materials in applications involving charge transport.

Self-Assembly of Ionically End-Capped Diblock Copolymers.

The self-assembly of ionically end-capped, symmetric polystyrene-polyisoprene diblock copolymers (PS-b-PI) has been studied. Structural data obtained from small-angle X-ray scattering (SAXS) and transmission electron microscopy (TEM) were correlated with the aggregation behavior of charged chain ends as evidenced by a spin probe using electron paramagnetic resonance (EPR) spectroscopy. The resulting mesomorphic structures were shown to be determined by the chain end topology, i.e., the site where the ionic chain end has been introduced chemically: For omega-functionalized diblock copolymers (monofunctional species) microphase separation is significantly stabilized due to the presence of ionic aggregates within the respective phase separated homopolymer domains. In contrast, for salt-free alpha,omega-macrozwitterionic diblock copolymers a marked perturbation of the block copolymer superstructure was found. In this case, the formation of a network of mixed ionic aggregates creates an additional microdomain interface by joining the chemically distinct blocks at their chain ends. The alteration of the degree of microphase separation as observed for the different functionalities can be attributed to conformational changes of the copolymer chain. Chain end association in the present system is reminiscent of certain covalently joined star and graft copolymers.

Organically modified aluminosilicate mesostructures from block copolymer phases

Organically modified aluminosilicate mesostructures were synthesized from two metal alkoxides with the use of poly(isoprene-b-ethyleneoxide) block copolymers (PI-b-PEO) as the structure-directing molecules. By increasing the fraction of the inorganic precursors with respect to the polymer, morphologies expected from the phase diagrams of diblock copolymers were obtained. The length scale of the microstructures and the state of alignment were varied using concepts known from the study of block copolymers. These results suggest that the use of higher molecular weight block copolymer mesophases instead of conventional low-molecular weight surfactants may provide a simple, easily controlled pathway for the preparation of various silica-type mesostructures that extends the accessible length scale of these structures by about an order of magnitude.

Strain differences in tissue concentrations of mercury in inbred mice treated with mercuric chloride.

Tissue concentrations of mercury were determined by cold vapor atomic absorption spectrometry in different inbred mouse strains after continuous treatment with HgCl2 (3 weekly sc injections of 0.5 mg/kg bw) for up to 12 weeks. Except for the thymus, in which steadily increasing mercury concentrations were found, in steady state levels of mercury were reached in blood and liver after 4 weeks and in spleen and kidney after 8 weeks. In the closely related strains C57BL/6, B10.D2, and B10.S, which differ only or primarily at the major histocompatibility complex, mercury concentrations in blood and liver were about twofold lower and renal concentrations were about three- to fivefold lower than those detected in strains A.SW and DBA/2. Another strain difference was observed in the spleen: after 8 and 12 weeks of continuous HgCl2 treatment, mercury concentrations in the spleen of strains A.SW, C57BL/6, and B10.S were significantly higher than those in strains DBA/2 and B10.D2. The strain difference in the spleen, an organ of the immune system, correlates with the susceptibility to the HgCl2-induced systemic autoimmune syndrome in mice in that the strains showing a higher mercury accumulation in the spleen are susceptible to this form of chemically induced autoimmunity, whereas the strains with lower mercury concentrations in the spleen are resistant.

A new approach to determining homopolymer domain sizes in polycarbonate-polyether dialysis membranes by solid-state NMR.

The size of micro-separated domains of polyether (PEO), -[CH2CH2O]n-, and polycarbonate (PC), -[(C6H4)-C(CH3)2-(C6H4)-OCO2]m-, in the dialysis membrane 'Gambrane' have been determined using an advanced solid-state NMR technique which exploits differences in 1H spin diffusion. The characteristic diameter of a PEO domain is 4.8 +/- 1.4 nm and that of PC is 5.2 +/- 1.4 nm with a mixed phase region of 0.8 +/- 0.5 nm.