Tris(bipyridine)ruthenium(II)-functionalized metal-organic frameworks for the ratiometric fluorescence determination of aluminum ions.

A novel ratiometric fluorescence probe was designed for the determination of Al3+ by self-assembling of NH2-MIL-101(Fe) and [Ru(bpy)3]2+. Under the excitation wavelength of 360 nm, the NH2-MIL-101(Fe)@[Ru(bpy)3]2+ presented a dual-emitting luminescent property at 440 and 605 nm, respectively. In the presence of Al3+, the blue fluorescence of NH2-MIL-101(Fe)@[Ru(bpy)3]2+ at 440 nm was enhanced remarkably, while the red emission at 605 nm was almost not influenced. Therefore, taking the fluorescence at 440 nm as the report signal and 605 nm as the reference signal, quantitative determination was achieved for Al3+ concentration in the ranges 0.2-25 µM and 25-250 µM. The limit of detection (LOD) and limit of quantification (LOQ) were calculated to be 73 nM and 244 nM, respectively. The sensing mechanisms were studied by theoretical calculation and optical spectra. The analysis of real food samples confirmed the suitability of the proposed method. More importantly, portable fluorescent test papers were successfully manufactured to provide a strategy for visual, rapid, and on-site detection of Al3+.

On-off-on fluorescent sensor for glutathione based on bifunctional vanadium oxide quantum dots induced spontaneous formation of MnO2 nanosheets.

Fluorescence sensing of glutathione by tailor-made chemical sensors is a prospective technique, which could provide simple, fast, and visual detection. Herein, a fluorescence sensor based on vanadium oxide quantum dots (VOx QDs) and permanganate (MnO4-) has been designed for monitoring glutathione. The bifunctional VOx QDs, possessing rich redox chemistry and robust fluorescence (exhibiting fluorescence near 505 nm upon excitation at 450 nm), were synthesized via cryogenic-mediated liquid-phase exfoliation. In the presence of MnO4-, VOx QDs induced the spontaneous formation of MnO2 nanosheets which caused the fluorescence quenching. However, the subsequent introduction of glutathione could trigger MnO2 reduction to Mn2+, and the fluorescence was recovered. Based on this phenomenon, an "on-off-on" fluorescence sensor for glutathione detection was established. Under the optimal conditions, this sensor allowed detection of glutathione in the linear range of 0.5-100 µM with a detection limit of 0.254 µM. Additionally, the proposed strategy revealed the selectivity toward glutathione and the potential of practical application in the analysis of human serum, vegetable, and fruit samples.

Intermittent proton bursts of single lactic acid bacteria.

Lactic acid bacteria are a kind of probiotic microorganisms that efficiently convert carbohydrates to lactic acids, thus playing essential roles in fermentation and food industry. While conventional wisdom often suggests continuous release of protons from bacteria during acidification, here we developed a methodology to measure the dynamics of proton release at the single bacteria level, and report on the discovery of a proton burst phenomenon, i.e., the intermittent efflux of protons, of single Lactobacillus plantarum bacteria. When placing an individual bacterium in an oil-sealed microwell, efflux and accumulation of protons consequently reduced the pH in the confined extracellular medium, which was monitored with fluorescent pH indicators in a high-throughput and real-time manner. In addition to the slow and continuous proton release behavior (as expected), stochastic and intermittent proton burst events were surprisingly observed with a typical timescale of several seconds. It was attributed to the regulatory response of bacteria by activating H+-ATPase to compensate the stochastic and transient depolarizations of membrane potential. These findings not only revealed an unprecedented proton burst phenomenon in lactic acid bacteria, but also shed new lights on the intrinsic roles of H+-ATPase in membrane potential homeostasis, with implications for both fermentation industry and bacterial electrophysiology.

Subjective well-being among Chinese breast cancer patients: The unique contributions of death anxiety, self-esteem, and social support.

Previous studies have indicated that cancer patients may have a lower level of subjective well-being (SWB); nevertheless, the underlying factors for this phenomenon remain insufficiently investigated. Based on the characteristics of Chinese breast cancer patients and the unique culture, this study explored the independent contributions of death anxiety, self-esteem, and social support to SWB from the protective and risk perspectives. A cross-sectional survey recruited 514 females with breast cancer and collected participants' demographic and the above variables. The results found that death anxiety independently predicted SWB in a negative direction (ß = -0.36, p < 0.001). In addition, self-esteem (ß = 0.38, p < 0.001) and social support (ß = 0.14, p < 0.001) also had the unique positive effects on SWB. These findings offer new insights into strengthening breast cancer patients' SWB, for instance, using relevant interventions to reduce death anxiety and improve self-esteem and social support.

An ingenious turn-on ratiometric fluorescence sensor for sensitive and visual detection of tetracyclines.

To achieve facile and rapid detection of tetracyclines (TCs), herein, we fabricated an ingenious turn-on ratiometric fluorescence sensor (Ru@ZIF-8) based on embedding red-emitting Ru(bpy)32+ into zeolitic imidazolate framework-8 (ZIF-8). With the introduction of TCs, Ru@ZIF-8 system held the impervious red fluorescence, and generated green fluorescence which originated from the interaction between ZIF-8 and TCs, thereby achieving ratiometric fluorescence strategy through turn-on response signal and stable reference signal. Moreover, the ratiometric response accompanied discernible color change from red to green-yellow, which facilitated detection by naked eyes. The developed sensor exhibited prominent specificity and sensitivity, with detection limits of 2.4, 4.2, 1.6 and 7.2 nM for tetracycline, chlortetracycline, oxytetracycline and doxycycline, respectively. In addition, the satisfactory recoveries were obtained during detecting TCs in drink water, milk and beef, and the test paper-based sensor was successfully applied in real-time visual detection of TCs. All results indicated the feasibility and potential application of Ru@ZIF-8.

Fluorescence and Colorimetric Dual-Mode Ratiometric Sensor Based on Zr-Tetraphenylporphyrin Tetrasulfonic Acid Hydrate Metal-Organic Frameworks for Visual Detection of Copper Ions.

As a special heavy metal ion, copper ions (Cu2+) play an indispensable role in the fields of environmental protection and safety. Their excessive intake not only easily leads to diseases but also affects human health. Therefore, it is particularly important to construct a facile, effective, and highly selective Cu2+ probe. Herein, a novel Zr-tetraphenylporphyrin tetrasulfonic acid hydrate (TPPS) metal-organic framework (ZTM) was fabricated using TPPS as the ligand and exhibited strong red fluorescence with a high quantum yield of 12.22%. In addition, we designed a ratiometric fluorescent probe by introducing green fluorescein isothiocyanate (FITC), which was not subject to environmental interference and had high accuracy. When exposed to different amounts of Cu2+, the fluorescence emission at 667 nm from ZTMs is remarkably quenched, while that at 515 nm from FITC is enhanced, accompanied by a change in the solutions' fluorescence color from red to green under a UV lamp. Besides, the ZTMs solutions display an excellent ratiometric colorimetric response for Cu2+ and produce an obvious color change (from green to colorless) that is visible to the naked eye. The fabricated ZTMs@FITC fluorescent probe exhibits distinguished performance for Cu2+ detection with linear ranges of 0.1 to 5 µM and 5 to 50 µM, as well as a low detection limit of 5.61 nM. Moreover, a colorimetric sensor based on ZTMs exhibits a good linear range from 0.1 to 20 µM for Cu2+ with the detection limit of 4.96 nM. Furthermore, the dual-signal ratiometric sensor has significant specificity for Cu2+ and is successfully applied for monitoring Cu2+ in water samples, which proves its practical application value in the environment and biological systems.

Innovative ratiometric optical strategy: Nonconjugated polymer dots based fluorescence-scattering dual signal output for sensing mercury ions.

A new ratiometric platform was developed for sensing Hg2+, which combined fluorescence and scattering simultaneously. This ratiometric strategy reflected superiorities over conventional methods, since the two independent signals at irrelevant categories meet the requirements of sufficient wavelength separation, stimulation under one excitation, and collection on single instrument. Herein, nonconjugated polymer dots (N-PDs) were served as the recognition unit for Hg2+ with turn-off fluorescence and turn-on scattering. Additionally, two signal collection tactics were proposed to achieve fluorescence and scattering in a window: one was to record down-conversion fluorescence and second-order scattering spectra (FL@SOS), and the other was to gather the fluorescence excited by second-order diffraction light and first-order scattering (SODL-FL@FOS). This ratiometric sensor exhibited outstanding performance toward Hg2+ in the range of 0.1-50 µM with the detection limit of 27 nM. By contrast, the present proposal provided a more ingenious and scalable way to construct ratiometric sensor than traditional approach.

Ingenious dual-emitting Ru@UiO-66-NH2 composite as ratiometric fluorescence sensor for detection of mercury in aqueous.

The increasing deterioration of ecosystem derived from heavy metals residues brings about the environmental and food contamination, which presses the exploration of facile platform for monitoring heavy metals. Herein, a ratiometric fluorescence sensor was designed for Hg2+ detection based on the compound of UiO-66-NH2 and Ru(bpy)32+ (Ru@UiO-66-NH2) which was synthesized by situ encapsulation. The innovative composite displayed two emission peaks at 437 and 604 nm, and the addition of Hg2+ could only quench the blue fluorescence due to static quenching and photo-induced electron transfer mechanism, providing an internal standard to promote the precision. Under optimal conditions, the ratiometric Ru@UiO-66-NH2 probe revealed outstanding anti-interference capability and performed with a great limit of detection (LOD) of 0.053 µM for Hg2+, which was 2-fold lower than that of single-color UiO-66-NH2. By merit of Ru@UiO-66-NH2, test hydrogels were fabricated to provide a tactics for visual, rapid and on-site detection of Hg2+. Additionally, the dual-emitting sensing platform presented satisfactory recoveries and reliabilities in lake water, tap water, and drink water, demonstrating the application potential of this proposed ratiometric fluorescence sensor for monitoring Hg2+.

Immunochromatographic Assay Based on Polydopamine-Decorated Iridium Oxide Nanoparticles for the Rapid Detection of Salbutamol in Food Samples.

Salbutamol (SAL), a ß-2 adrenoreceptor agonist, is an unpopular addition to livestock and poultry, causing several side effects to human health. Thus, it is very important to develop a simple and rapid analytical method to screen SAL in the field of food safety. Here, we present an immunochromatographic assay (ICA) method for sensitively detecting SAL with polydopamine-decorated iridium oxide nanoparticles (IrO2@PDA NPs) as a signal tag. The IrO2@PDA with excellent hydrophilicity, biocompatibility, and stability was synthesized by oxidating self-polymerization of dopamine hydrochloride (DAH) on the surface of IrO2 NPs and used to label monoclonal antibodies (mAbs) through simple physical adsorption. Compared with IrO2 NPs, the IrO2@PDA also possessed superior optical properties and higher affinity with mAbs. With the proposed method, the limit of detection for SAL was 0.002 ng/mL, which was improved at least 24-fold and 180-fold compared with the IrO2 NPs-based ICA and conventional gold nanoparticles-based ICA, respectively. Furthermore, the SAL residuals in pork, pork liver, and beef were successfully detected by the developed biosensor and the recoveries ranged from 85.56% to 115.56%. Briefly, this work indicated that the powerful IrO2@PDA-based ICA can significantly improve detection sensitivity and has huge potential for accurate and sensitive detection of harmful small molecules analytes in food safety fields.

Neural correlates of social well-being: gray matter density in the orbitofrontal cortex predicts social well-being in emerging adulthood.

Social well-being reflects the perception of one's social functioning, which plays an important role in physical and psychological health. However, the exact neuroanatomical substrate for social well-being remains unclear. To address the issue, we employed the voxel-based morphometry method to probe the neuroanatomical basis of individual variation in social well-being in young healthy adults (n = 136). The results revealed a significant negative association between social well-being and regional gray matter density (rGMD) in an anatomical cluster that mainly includes the left orbitofrontal cortex (OFC) that has been involved in emotion regulation and social cognition. Furthermore, a balanced 4-fold cross-validation using the machine learning approach revealed that rGMD in the left OFC could be reliably related to social well-being. More importantly, the multiple mediation analysis revealed that neuroticism and dispositional forgiveness independently mediated the association between rGMD in the left OFC and social well-being. In addition, all these results remained stable when subjective socioeconomic status was controlled. Together, our results provide the initial evidence that the OFC is a neuroanatomical substrate for social well-being and demonstrate that the OFC is a crucial neural site linking neuroticism and dispositional forgiveness to social well-being.