Independently tunable multi-band terahertz absorber based on graphene sheet and nanoribbons.

A multi-band terahertz (THz) absorber based on graphene sheet and nanoribbons is proposed and investigated. In the studied frequency range, five absorption peaks are observed, with four originate from lateral Fabry-Perot resonance (LFPR) and one originates from guided-mode resonance (GMR). The LFPR and GMR peaks behave differently when geometric parameters are adjusted, which makes independent tuning possible. When period increases, the GMR peak red shifts and the frequencies of LFPR peaks remain almost unchanged. On the contrary, as nanoribbon width increases, the frequency of GMR remains almost unchanged while that of LFPRs decrease significantly. With increasing top dielectric layer thickness, the LFPR peaks blue shift while the GMR peak red shifts. In addition, the absorber has the merit of multi-band high absorptivity and frequency stability under large angle oblique incidence. The proposed terahertz absorber may benefit the areas of medical imaging, sensing, non-destructive testing, THz communications and other applications.

Rhein-based necrosis-avid MRI contrast agents for early evaluation of tumor response to microwave ablation therapy.

PURPOSE: Early evaluation of tumor response to thermal ablation therapy can help identify untreated tumor cells and then perform repeated treatment as soon as possible. The purpose of this work was to explore the potential of rhein-based necrosis-avid contrast agents (NACAs) for early evaluation of tumor response to microwave ablation (MWA). METHODS: 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyl tetrazolium bromide (MTT) assay was performed to test the cytotoxicity of rhein-based NACAs against HepG2 cells. Rat models of liver MWA were used for investigating the effectiveness of rhein-based NACAs in imaging the MWA lesion, the optimal time period for post-MWA MRI examination, and the metabolic behaviors of 68 Ga-labeled rhein-based NACAs. Rat models of orthotopic liver W256 tumor MWA were used for investigating the time window of rhein-based NACAs for imaging the MWA lesion, the effectiveness of these NACAs in distinguishing the residual tumor and the MWA lesion, and their feasibility in early evaluating the tumor response to MWA. RESULTS: Gadolinium 2,2',2''-(10-(2-((4-(4,5-Dihydroxy-9,10-dioxo-9,10-dihydroanthracene-2-carboxamido)butyl)amino)-2-oxoethyl)-1,4,7,10-tetraazacyclododecane-1,4,7-triyl)triacetic acid (GdL2 ) showed low cytotoxicity and high quality in imaging the MWA region. The optimal time period for post-MWA MRI examination using GdL2 was 2 to 24 h after the treatment. During 2.5 to 3.5 h postinjection, GdL2 can better visualize the MWA lesion in comparison with gadolinium 2-[4,7,10-tris(carboxymethyl)-1,4,7,10-tetraazacyclododec-1-yl]acetic acid (Gd-DOTA), and the residual tumor would not be enhanced. The tumor response to MWA as evaluated by using GdL2 -enhanced MRI was consistent with histological examination. CONCLUSION: GdL2 appears to be a promising NACA for the tumor response assessment after thermal ablation therapies.

High salinity effects on the depletion attraction in colloid-polymer mixtures.

HYPOTHESIS: Depletion attraction induced by polymers can be employed across multiple disciplines. Previous studies implied that besides screening the electrostatic repulsion between colloids, adding salt may also affect the polymers even in a nonpolar solvent. Here, we study the depletion-induced gelation of a colloid-polymer model system, focusing on the salt effects on the depletion attraction. EXPERIMENTS: Confocal microscopy was used to quantitatively characterize the colloidal gels formed by the polymethylmethacrylate (PMMA)/polystyrene (PS) model system. The attraction experienced by colloids was estimated by correlating the colloidal dynamics with the local structure. Correspondingly, static light scattering was employed to systematically investigate the polymers. The resulting radius of gyration Rg and osmotic pressure were used to evaluate the depletion attraction offered by polymers. FINDINGS: Salt was discovered to lower the strength of inter-particle attraction, which can be attributed to the salt-induced decrease in Rg. The depletion attraction grew sublinearly with c, owing to the considerable decrease in Rg in the good solvent as c increased. We demonstrated how the close form equations in the framework of renormalization group theory can be employed to predict the depletion interaction using the properly determined zero-concentration radius of gyration.

Design and Evaluation of Rhein-Based MRI Contrast Agents for Visualization of Tumor Necrosis Induced by Combretastatin A-4 Disodium Phosphate.

PURPOSE: Visualization of tumor necrosis can determine tumor response to therapy. Our previous study showed that the rhein-based magnetic resonance imaging (MRI) contrast agent with alkane linker (GdL2) could clearly image tumor necrosis. However, its water solubility and cell safety needed to be improved. Herein, three rhein-based MRI agents with ether or lysine linkers were designed. PROCEDURES: Three rhein-based MRI agents were synthesized with a tetracarbon ether (GdP1), a hexacarbon ether (GdP2), and a lysine (GdP3) linker, respectively. Their octanol-water partition coefficients (log P) and cytotoxicity were determined. Necrosis avidity of the leading agent was explored on HepG2 cells and ischemia reperfusion-induced liver necrosis (IRLN) rats by MRI. The effect of visualization of tumor necrosis was tested on nude mice with W256 tumor treated by combretastatin-A4 phosphate (CA4P). DNA binding assays were applied to evaluate the possible necrosis-avidity mechanism of the leading agent. RESULTS: The log P of three agents (- 1.66 ± 0.09, - 1.74 ± 0.01, - 1.95 ± 0.01) decreased when compared with GdL2, indicating higher water solubility. GdP1 not only presented lower cytotoxicity and good necrotic affinity in vitro and in vivo, but also can be fast excreted by renal. According to MRI results of tumor, distinct visualization of tumor necrosis can be discernible from 3 to 4.5 h post-injection of GdP1. In DNA-binding assays, the fluorescence quenching constant KSV (1.00 × 104 M-1) and the ultraviolet binding constant Kb (1.11 × 104 M-1) suggested that GdP1 may bind to DNA through intercalation. CONCLUSION: GdP1 may serve as a potential candidate for early evaluation of tumor response to CA4P treatment.

Synthesis and Evaluation of Diindole-Based MRI Contrast Agent for In Vivo Visualization of Necrosis.

PURPOSE: Noninvasive imaging of cell necrosis can provide an early evaluation of tumor response to treatments. Here, we aimed to design and synthesize a novel diindole-based magnetic resonance imaging (MRI) contrast agent (Gd-bis-DOTA-diindolylmethane, Gd-DIM) for assessment of tumor response to therapy at an early stage. PROCEDURES: The oil-water partition coefficient (Log P) and relaxivity of Gd-DIM were determined in vitro. Then, its necrosis avidity was examined in necrotic cells in vitro and in rat models with microwave ablation-induced muscle necrosis (MAMN) and ischemia reperfusion-induced liver necrosis (IRLN) by MRI. Visualization of tumor necrosis induced by combretastatin A-4 disodium phosphate (CA4P) was evaluated in rats bearing W256 orthotopic liver tumor by MRI. Finally, DNA binding assay was performed to explore the possible necrosis-avidity mechanism of Gd-DIM. RESULTS: The Log P value and T1 relaxivity of Gd-DIM is - 2.15 ± 0.01 and 6.61 mM-1 s-1, respectively. Gd-DIM showed predominant necrosis avidity in vitro and in vivo. Clear visualization of the tumor necrosis induced by CA4P was achieved at 60 min after administration of Gd-DIM. DNA binding study indicated that the necrosis-avidity mechanism of Gd-DIM may be due to its binding to exposed DNA in necrotic cells. CONCLUSION: Gd-DIM may serve as a promising necrosis-avid MRI contrast agent for early assessment of tumor response to therapy.

The Chinese herbal medicine formula FAHF-2 completely blocks anaphylactic reactions in a murine model of peanut allergy.

BACKGROUND: Peanut allergy is potentially life threatening. There is no curative therapy for this disorder. We previously found that an herbal formula, food allergy herbal formula (FAHF)-1, blocked peanut-induced anaphylaxis in a murine model when challenged immediately posttherapy. OBJECTIVE: To test whether FAHF-2, an improved herbal formula, from which 2 herbs, Zhi Fu Zi (Radix Lateralis Aconiti Carmichaeli Praeparata) and Xi Xin (Herba Asari), were eliminated, is equally effective to FAHF-1, and if so, whether protection persists after therapy is discontinued. METHODS: Mice allergic to peanut treated with FAHF-2 for 7 weeks were challenged 1, 3, or 5 weeks posttherapy. Anaphylactic scores, core body temperatures, vascular leakage, and plasma histamine levels after peanut challenge were determined. Serum peanut-specific antibody levels and splenocyte cytokine profiles were also measured. RESULTS: After challenges, all sham-treated mice developed severe anaphylactic signs, significant decrease in rectal temperatures, significantly increased plasma histamine levels, and marked vascular leakage. In contrast, no sign of anaphylactic reactions, decrease in rectal temperatures, or elevation of plasma histamine levels was observed in FAHF-2-treated mice in 5 separate experiments. IgE levels were significantly reduced by FAHF-2 treatment and remained significantly lower as long as 5 weeks posttherapy. Splenocytes from FAHF-2-treated mice showed significantly reduced IL-4, IL-5, and IL-13, and enhanced IFN-gamma production to recall peanut stimulation in vitro . CONCLUSION: FAHF-2 treatment completely eliminated anaphylaxis in mice allergic to peanut challenged as long as 5 weeks posttherapy. This result was associated with downregulation of T H 2 responses. FAHF-2 may be a potentially effective and safe therapy for peanut allergy.