Reduced graphene oxide (RGO) and silver nanoparticle (AgNP) hybrids (RGO-AgNP) were prepared by a facile one-pot method using Poly (N-vinyl-2-pyrrolidone) as reductant and stabilizer. Folic acid (FA) molecules were attached to the RGO-AgNP by physisorption for targeting specific cancer cells with folate receptors (FRs) and using as Raman reporter molecules. The internalization of the FA loaded RGO-AgNP (RGO-AgNP-FA) inside the FRs-positive cancer cell was confirmed by confocal laser scanning and transmission electron microscopy. The Raman signals of the FA in live cancer cells were detected by confocal Raman spectroscope at 514 nm excitation, indicating that the RGO-AgNP-FA material has great potential as a Raman probe for cancer diagnosis in vitro.

BackgroundEnterovirus 71 (EV71) is one of the major causative agents of hand, foot, and mouth disease (HFMD), which is sometimes associated with severe central nervous system disease in children. There is currently no specific medication for EV71 infection. Quercetin, one of the most widely distributed flavonoids in plants, has been demonstrated to inhibit various viral infections. However, investigation of the anti-EV71 mechanism has not been reported to date.MethodsThe anti-EV71 activity of quercetin was evaluated by phenotype screening, determining the cytopathic effect (CPE) and EV71-induced cells apoptosis. The effects on EV71 replication were evaluated further by determining virus yield, viral RNA synthesis and protein expression, respectively. The mechanism of action against EV71 was determined from the effective stage and time-of-addition assays. The possible inhibitory functions of quercetin via viral 2Apro, 3Cpro or 3Dpol were tested. The interaction between EV71 3Cpro and quercetin was predicted and calculated by molecular docking.ResultsQuercetin inhibited EV71-mediated cytopathogenic effects, reduced EV71 progeny yields, and prevented EV71-induced apoptosis with low cytotoxicity. Investigation of the underlying mechanism of action revealed that quercetin exhibited a preventive effect against EV71 infection and inhibited viral adsorption. Moreover, quercetin mediated its powerful therapeutic effects primarily by blocking the early post-attachment stage of viral infection. Further experiments demonstrated that quercetin potently inhibited the activity of the EV71 protease, 3Cpro, blocking viral replication, but not the activity of the protease, 2Apro, or the RNA polymerase, 3Dpol. Modeling of the molecular binding of the 3Cpro-quercetin complex revealed that quercetin was predicted to insert into the substrate-binding pocket of EV71 3Cpro, blocking substrate recognition and thereby inhibiting EV71 3Cpro activity.ConclusionsQuercetin can effectively prevent EV71-induced cell injury with low toxicity to host cells. Quercetin may act in more than one way to deter viral infection, exhibiting some preventive and a powerful therapeutic effect against EV71. Further, quercetin potently inhibits EV71 3Cpro activity, thereby blocking EV71 replication.

BaSi2O2N2:Eu2+ phosphor was successfully synthesized by using a simple solid‐state reaction method. Its properties were systematically investigated utilizing XRD, photoluminescence, excited state decay curve, afterglow emission spectra, and thermoluminescence (TL) glow curve. With increasing temperature, its emission intensity decreases with the broadening full widths at half maximum. Particularly, its temperature‐dependent afterglow emission spectra were investigated for the first time. Based on the information from TL glow curve, temperature‐dependent afterglow decay curves, and afterglow emission spectra, a model was constructed to explain the mechanism of afterglow. This study provides a new perspective to use the temperature‐dependent luminescence properties for studying the afterglow processes of long‐lasting phosphorescence phosphors.

The nitrides Ca2Si5N8:0.5%Eu2+, x%Tm3+(x = 0, 0.5, 1, 2, 4) (CSN:0.5E, xT) phosphors were prepared via the high temperature solid‐sintering method using CaH2 as calcium source. These phosphors exhibited strong orange long‐lasting phosphorescence (LLP) after turning off the activating light. Besides, the CSN:0.5E, 1T phosphor with an afterglow time of more than 200 min (0.32 mcd/m2). Furthermore, the temperature‐dependent emission spectra of CSN:0.5E, 1T were investigated from temperature 80–500 K and an anti‐quenching phenomenon that the emission intensities increased then decreased under excitation at increased temperature was found. Ultimate, the proposed mechanism on temperature dependence of luminescence was analyzed. This study provides a new perspective for the impact of temperature‐dependent problem as a consequence of heating processes in luminescent materials.

Oxynitride long‐lasting phosphorescence (LLP) phosphor SrSi2O2N2:Eu2+ was prepared by a new method using SrSi alloy as a precursor. Its properties were systematically investigated utilizing XRD, photoluminescence, excited‐state decay curve, long‐lasting phosphorescence, and thermoluminescence spectrum. This phosphor was found to be well‐crystallized by calcinations of the Sr1−xEuxSi alloy and the SiO2 mixture at 1400°C for 3 h. After irradiation under the 280 nm UV light, the afterglow emission of Eu2+ (4f65d1 → 4f7) was obviously observed for at least 2 h in the limit of light perception of dark‐adapted human eyes (0.32 mcd/m2). Furthermore, the possible mechanism for the LLP of SrSi2O2N2:Eu2+ phosphor is also discussed in this article.