Tuning luminescence of the fluorescent molecule 2-(2-hydroxyphenyl)-1H-benzimidazole via zeolitic imidazolate framework-8.

Zeolitic imidazolate framework-8 (ZIF-8) is one of the most promising metal-organic frameworks because of its excellent high porosity, stability and geometrically well-defined structure. However, the application of ZIF-8 in the field of fluorescent molecular sensing has not been intensively explored. Our work demonstrates the versatility of ZIF-8 as a carrier material, which can be used for small molecule [2-(2-hydroxyphenyl)-1H-benzimidazole (HPBI)] capture and fluorescence enhancement. ZIF-8 displays luminescent behavior changes when combined with HPBI, as the emission peaks of ZIF-8 and HPBI are located in the same range for resonance enhancement of fluorescence. The results of the experiment indicate that the fluorescence enhancement effect will change in the presence of different concentrations of HPBI. We propose that the pore structure of ZIF-8 could provide an opportunity for the adsorption of HPBI molecules, and eventually the adsorption would saturate. The high porosity of ZIF-8 provides the path to HPBI aggregation or entrance into the ZIF-8 internal structure. Our results suggest that ZIF-8 may offer great promise for molecular fluorescence sensing.

Fluorescence of CoTPP Mediated by the Plasmon-Exciton Coupling Effect in the Tunneling Junction.

CoTPP, as a common hypsoporphyrin, is usually not a luminescent molecule because of the open-shell Co ion. In this paper, well-defined multilayer CoTPP molecules self-assembled on Au(111) surface are characterized layer by layer with scanning tunneling microscope (STM) induced luminescence. By using the highly localized STM tunneling current, we not only investigate the influence of bias polarity on the amplitude of distinct plasmonic emission resulted from the interaction between the metal substrate and the metal ions but also first obtain the light emission from the hypsoporphyrins in the tunneling junction. The density-matrix method and the combined approach of classical electrodynamics and first-principles calculation are used to explain the mechanism of the light emission. These findings may expand the underlying physics of plasmon-exciton coupling in STM nanocavity and reveal a new possible path to overcome the fluorescent potential of hypsoporphyrins by the intense localized electric fields.

Distance-Dependent Plasmon-Enhanced Fluorescence of Submonolayer Rhodamine 6G by Gold Nanoparticles.

We investigate the fluorescence from submonolayer rhodamine 6G molecules near gold nanoparticles (NPs) at a well-controlled poly (methyl methacrylate) (PMMA) interval thickness from 1.5 to 21 nm. The plasmonic resonance peaks of gold NPs are tuned from 530 to 580 nm by the PMMA spacer of different thicknesses. Then, due to the plasmonic resonant excitation enhancement, the emission intensity of rhodamine 6G molecules at 562 nm is found to be enhanced and shows a decline as the PMMA spacer thickness increases. The variation of spectral intensity simulated by finite-difference time-domain method is consistent with the experimental results. Moreover, the lifetime results show the combined effects to rhodamine 6G fluorescence, which include the quenching effect, the barrier effect of PMMA as spacer layer and the attenuation effect of PMMA films.

Protective effect of glycyrrhizin on osteoarthritis cartilage degeneration and inflammation response in a rat model.

This study was conducted to investigate the protective effects of glycyrrhizin on a rat model of osteoarthritis and elucidate the underlying mechanism. Rat osteoarthritis was established by using medial meniscectomy (MMx) and an anterior cruciate ligament transaction (ACLT). Glycyrrhizin (2, 4, and 10 mg/kg) was administered by intra-articular knee injection for 12 weeks. Incapacitance test was performed to determine mechanical hyperalgesia. Enzyme-linked immunosorbent assay (ELISA) was performed to measure cartilage degradation and inflammation-related markers. Quantitative reverse transcription PCR (RT-qPCR) and Western blot were performed to determine the mRNA and protein levels of genes, respectively. The results demonstrated that treatment with glycyrrhizin ameliorated mechanical hyperalgesia and bilateral joints oedema in a rat model of osteoarthritis. Treatment with 10 mg/kg glycyrrhizin also suppressed serum enzymes including matrix metalloproteinase (MMP)-1, MMP-3, prostaglandin E2, and C-telopeptide of type II collagen (CTX-II). In addition to inhibition of cartilage matrix catabolic related markers, treatment with glycyrrhizin also decreased the levels of interleukin (IL)-1ß, IL-6, tumor necrosis factor (TNF)-α, and iNOS in serum and cartilage. The underlying mechanism study demonstrated that treatment with glycyrrhizin inhibited HMGB1 and the TLR4/NF-κB signaling pathway. In summary, treatment with glycyrrhizin ameliorated cartilage degeneration and inflammation in osteoarthritis rats by the regulation of HMGB1 and the TLR4/NF-κB signaling pathway.

Resveratrol-mediated SIRT1 activation attenuates ovalbumin-induced allergic rhinitis in mice.

Resveratrol (RSV) is one kind of polyphenol that possesses anti-inflammatory effect. The effect of RSV in allergic rhinitis (AR) remains unclear. In this study, we investigated the protective effect of RSV against AR and explored the related signaling pathways. AR mouse model was successfully established by intraperitoneal injection with Ovalbumin (OVA). RSV administration was performed in a diet with different doses (5, 30, 50 mg/kg). Allergic symptoms were indicated by sneezing and nasal rubbing. Cytokines in serum and nasal lavage fluid (NLF) were determined by ELISA. mRNA and protein levels were detected by RT-PCR and Western blot. Our results show that RSV treatment attenuated sneezing and nasal rubbing in AR mice. It decreased histamine release, OVA-specific IgE, IgG1, IL-4 and LTC4, inflammatory cell numbers (leucocytes, eosinophils, lymphocytes, and neutrophils), and inflammatory cytokines secretion (TNF-α, IL-6, IL-10, IL-5, IL-13, and IL-17). Mechanically, RSV treatment suppressed HMGB1 and TLR4 expression and promoted SIRT1 expression in the nasal mucosa. In conclusion, RSV is able to attenuate OVA-induced AR in mice.

Effect of artemisinin and neurectomy of pterygoid canal in ovalbumin-induced allergic rhinitis mouse model.

BACKGROUND: Allergic rhinitis (AR), characterized by sneezing, nasal itching and rhinorrhea, affects a large number of population. This study aimed to explore the effects of artemisinin alone or combined with neurectomy of pterygoid canal in ovalbumin-induced AR mouse model and illustrate the underlying mechanisms. METHODS: Allergic symptoms were evaluated to verify inhibitory effect of artemisinin alone or combined with neurectomy of pterygoid canal on AR. Serum levels of histamine, immunoglobulin E (IgE) and inflammatory factors TNF, INF-γ, IL-1ß IL-10, IL-4 and IL-5 were measured by ELISA. The mRNA levels of TNF, INF-γ, IL-1ß and IL-10 in local lymph nodes were measured by RT-qPCR. The total and phosphorylated levels of ERK and JNK were assessed by Western blot. CD4+CD25+Foxp3+ T (Treg) cells were analyzed by flow cytometry. RESULTS: Artemisinin significantly relieved the behavior symptoms of AR mice. The administration of artemisinin strikingly suppressed the expression of histamine, IgE and inflammatory factors. An increased Treg cell proportion and inhibited ERK phosphorylation were observed in artemisinin-treated groups as compared to those in the AR group. Moreover, artemisinin plus neurectomy of pterygoid almost abolished the behavioral score increase in AR mice. CONCLUSIONS: These results indicated that artemisinin exhibited anti-allergic effect by inhibiting ERK activation and increasing Treg cell proportion, which subsequently decreased the expressions of allergic mediators. In addition, artemisinin combined with neurectomy of pterygoid showed better efficacy than artemisinin alone.