NIR Fluorescent/Photoacoustic Bimodal Imaging of Ferroptosis in Pancreatic Cancer Using Biothiols-Activable Probes.

Ferroptosis modulation is a powerful therapeutic option for pancreatic ductal adenocarcinoma (PDAC) with a low 5-year survival rate and lack of effective treatment methods. However, due to the dual role of ferroptosis in promoting and inhibiting pancreatic tumorigenesis, regulating the degree of ferroptosis is very important to obtain the best therapeutic effect of PDAC. Biothiols are suitable as biomarkers of imaging ferroptosis due to the dramatic decreases of biothiol levels in ferroptosis caused by the inhibited synthesis pathway of glutathione (GSH) and the depletion of biothiol by reactive oxygen species. Moreover, a very recent study reported that cysteine (Cys) depletion can lead to pancreatic tumor ferroptosis in mice and may be employed as an effective therapeutic strategy for PDAC. Therefore, visualization of biothiols in ferroptosis of PDAC will be helpful for regulating the degree of ferroptosis, understanding the mechanism of Cys depletion-induced pancreatic tumor ferroptosis, and further promoting the study and treatment of PDAC. Herein, two biothiol-activable near-infrared (NIR) fluorescent/photoacoustic bimodal imaging probes (HYD-BX and HYD-DX) for imaging of pancreatic tumor ferroptosis were reported. These two probes show excellent bimodal response performances for biothiols in solution, cells, and tumors. Subsequently, they have been employed successfully for real-time visualization of changes in concentration levels of biothiols during the ferroptosis process in PDAC cells and HepG2 cells. Most importantly, they have been further applied for bimodal imaging of ferroptosis in pancreatic cancer in mice, with satisfactory results. The development of these two probes provides new tools for monitoring changes in concentration levels of biothiols in ferroptosis and will have a positive impact on understanding the mechanism of Cys depletion-induced pancreatic tumor ferroptosis and further promoting the study and treatment of PDAC.

Equivalent Response Strategy for Sensing Total Biothiols in Human Serums and Living Cells Using a Hemicyanine-Based Self-Immolative Probe.

Biothiols including cysteine (Cys), homocysteine (Hcy), and glutathione (GSH) are crucial in maintaining the redox balance in the body, and the metabolism and transportation of biothiols rely on the coreaction of diverse proteins and enzymes. The abnormal concentrations and metabolism of biothiols are closely associated with many diseases. However, due to the same active reaction site of the sulfydryl group in biothiols, it is inevitable to bear a confused signal of mutual influence on both nonselective detection and discriminate detection, which presents a serious challenge of accurately sensing or imaging the three biothiols. By assigning an α,ß-unsaturated ketone moiety as a Michael acceptor to trigger thiols to complete the irreversible equivalent domino response processes of nucleophilic addition, olefinic bond migration, and self-immolation, a targeted strategy was rationally pointed out, and herein, a hemicyanine-based probe CyOCy was prepared as a proof of strategy demonstration. The new probe could be equivalently lit up by Cys, Hcy, GSH, and even biothiol combinations (Cys/Hcy, Cys/GSH, Hcy/GSH, or Cys/Hcy/GSH) with unified linear ranges, detection limits, and response times. The probe CyOCy has been successfully used for the accurate quantification of total biothiols in the serum samples of healthy persons and coronary heart disease patients. In addition, the probe has been applied for cell screening, exogenous biothiol imaging, and monitoring drug-induced biothiol fluctuations. The purposive thinking of this work may provide an effective avenue for the accurate sensing of multicomponent samples.

Reaction-Activated Disassembly of the NIR-II Probe Enables Fast Detection and Ratiometric Photoacoustic Imaging of Glutathione In Vivo.

Glutathione (GSH), the most abundant nonprotein biothiol, is a significant endogenous molecule that plays a key role in redox equilibrium in vivo and is regarded as a critical biomarker of cancer. Currently, various fluorescent probes have been designed and synthesized for imaging GSH at the cellular level in the visible range and the first near-infrared window (NIR-I, 750-900 nm). However, the application of these fluorescent probes for bioimaging and biosensing in vivo has been extremely hindered by the high biobackground and low tissue penetration. Herein, based on the self-assembly and disassembly of J-aggregation, we designed and synthesized a GSH-activatable probe MC-PSE for second near-infrared window (NIR-II) fluorescence and ratiometric photoacoustic imaging of GSH in vivo. The anionic cyanine-based MC-PSE tends to form stable J-aggregates in an aqueous solution. Upon the reaction with GSH, the J-aggregates of MC-PSE disassembled, the emission peak intensity of MC-PSE at 940 nm significantly increased by about 20 times, and the PA900/PA980 ratio increased by 4 times within 15 min in vitro. Notably, we used MC-PSE to visualize GSH in tumor-bearing mice and to distinguish normal and tumor areas successfully by virtue of NIR-II FL and PA dual-modal imaging. The design strategy of MC-PSE provides a novel method for ratiometric photoacoustic imaging, and MC-PSE is expected to be a powerful tool for the accurate detection of GSH in cancer diagnosis.

Clinical application value of Inhibin B alone or in combination with other hormone indicators in subfertile men with different spermatogenesis status: A study of 324 Chinese men.

BACKGROUND: In this study, we investigated the clinical value of serum Inhibin B alone or in combination with other hormone indicators in subfertile men. METHODS: This is a multicenter study involving 324 men from different cities in China. Testicular volume, routine semen analysis, serum Inhibin B, anti-Müllerian hormone (AMH), follicle-stimulating hormone (FSH), luteinizing hormone (LH), testosterone, estradiol, and prolactin were measured. Testicular tissue samples were also analyzed in 78 of 129 patients with azoospermia to distinguish impaired spermatogenesis from obstructive azoospermia. RESULTS: The concentration of Inhibin B, FSH, and AMH is related to spermatogenesis. For men with impaired spermatogenesis, including mild-to-moderate oligozoospermia (IMO) and severe oligozoospermia (ISO), serum levels of Inhibin B and FSH are highly correlated with sperm counting. However, in patients with idiopathic moderate oligozoospermia or severe oligozoospermia, there was no significant correlation between Inhibin B (or FSH) and sperm concentration. The upper cutoff value of Inhibin B to diagnose ISO is 58.25 pg/ml with a predictive accuracy of 80.65%. To distinguish between nonobstructive azoospermia (NOA) and obstructive azoospermia (OA), the area under the curve (AUC) for AMH + Inhibin B + FSH is very similar to Inhibin B (0.943 vs. 0.941). The cutoff level of Inhibin B to diagnose nonobstructive azoospermia is 45.9 pg/ml with a positive and negative prediction accuracy of 97.70% and 85.71%, respectively. CONCLUSION: In summary, Inhibin B is a promising biomarker alone or in combination with other hormone indicators for the diagnosis of testicular spermatogenesis status, helping clinical doctors to distinguish NOA from OA.

Efficacy of Chemiluminescence Immunoassays on VCA-IgA and EBNA1-IgA Antibodies of Epstein-Barr Virus in Diagnosing Nasopharyngeal Carcinoma.

Background: IgA antibodies against Epstein-Barr virus (EBV) capsid antigen (VCA) and nuclear antigen 1 (EBNA1) have been proposed to facilitate the diagnosis and early detection of nasopharyngeal carcinoma (NPC) in high-incidence regions. However, while new methodologies and new platforms for the detection of VCA-IgA and EBNA1-IgA have become available, proper interassay simultaneous comparisons have not been carried out. The study was to compare the performance of the chemiluminescent immunoassays (CLIA) and enzyme-linked immunosorbent assay (ELISA) for VCA-IgA and EBNA1-IgA antibodies, and to evaluate the levels of EBV antibodies in healthy population from different areas of China. Methods: CLIA and ELISA for VCA-IgA and EBNA1-IgA were performed in NPC and healthy populations from high-incidence areas of NPC in South China (N=555), medium-incidence areas of NPC in Central China (N=318) and low-incidence areas of NPC in North China (N=379), and the results were compared and analyzed. Results: (1) The highest sensitivity in total, early and advanced NPC were 91.5% (CLIA for VCA-IgA), 86.4% (CLIA and ELISA-2 for EBNA1-IgA) and 93.6% (CLIA for VCA-IgA). However, the specificity of EBV-IgA measured by CLIA was relatively lower than ELISA. The top three seromarkers with the largest AUC was CLIA for VCA-IgA (AUC: 0.929, 95% CI: 0.905-0.953), ELISA-2 for EBNA1-IgA (AUC: 0.922, 95% CI: 0.896-0.947) and CLIA for EBNA1-IgA (AUC:0.919, 95% CI: 0.893-0.945), respectively. The positive and negative coincidence rates of the two EBNA1-IgA kits were 69.5% and 91.9%, respectively. However, the coincidence rates of VCA-IgA were relatively low. CLIA kits had good repeatability between different laboratories. (2) The positive rates of EBV-IgA antibodies were relatively high in high-incidence areas of NPC (P < 0.017), while there was no significant difference in the antibody positive rates between medium-incidence areas and low-incidence areas of NPC (P > 0.05). Conclusions: The performance of EBV-IgA antibodies measured by CLIA has good repeatability, higher sensitivity and similar specificity. The higher EBV-IgA positive rate in healthy subjects by CLIA raises concern about its suitability for NPC-risk screening and requires further analysis.

Development and multicenter performance evaluation of fully automated SARS-CoV-2 IgM and IgG immunoassays.

Objectives: The outbreak of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has rapidly spread globally. The laboratory diagnosis of SARS-CoV-2 infection has relied on nucleic acid testing; however, it has some limitations, such as low throughput and high rates of false negatives. Tests of higher sensitivity are needed to effectively identify infected patients. Methods: This study has developed fully automated chemiluminescent immunoassays to determine IgM and IgG antibodies to SARS-CoV-2 in human serum. The assay performance has been evaluated at 10 hospitals. Clinical specificity was evaluated by measuring 972 hospitalized patients and 586 donors of a normal population. Clinical sensitivity was assessed on 513 confirmed cases of SARS-CoV-2 by RT-PCR. Results: The assays demonstrated satisfied assay precision with coefficient of variation of less than 4.45%. Inactivation of specimen did not affect assay measurement. SARS-CoV-2 IgM showed clinical specificity of 97.33 and 99.49% for hospitalized patients and the normal population respectively, and SARS-CoV-2 IgG showed clinical specificity of 97.43 and 99.15% respectively. SARS-CoV-2 IgM showed clinical sensitivity of 82.54, 92.93, and 84.62% before 7 days, 7-14 days, and after 14 days respectively, since onset of symptoms, and SARS-CoV-2 IgG showed clinical sensitivity of 80.95, 97.98, and 99.15% respectively at the same time points above. Conclusions: We have developed fully automated immunoassays for detecting SARS-CoV-2 IgM and IgG antibodies in human serum. The assays demonstrated high clinical specificity and sensitivity, and add great value to nucleic acid testing in fighting against the global pandemic of the SARS-CoV-2 infection.

Naked-Eye Readout of Analyte-Induced NIR Fluorescence Responses by an Initiation-Input-Transduction Nanoplatform.

Fluorescence visualization (FV) in the near-infrared (NIR) window promises to break through the signal-to-background ratio (SBR) bottleneck of traditional visible-light-driven FV methods. However, straightforward NIR-FV has not been realized, owing to the lack of methods to readily transduce NIR responses into instrument-free, naked eye-recognizable outputs. Now, an initiation-input-transduction platform comprising a well-designed NIR fluorophore as the signal initiator and lanthanide-doped nanocrystals as the transducer for facile NIR-FV is presented. The analyte-induced off-on NIR signal serves as a sensitizing switch of transducer visible luminescence for naked-eye readout. The design is demonstrated for portable, quantitative detection of phosgene with significantly improved SBR and sensitivity. By further exploration of initiators, this strategy holds promise to create advanced NIR-FV probes for broad sensing applications.

A near-infrared fluorescent probe based on photostable Si-rhodamine for imaging hypochlorous acid during lysosome-involved inflammatory response.

Hypochloric acid (HClO) is mainly distributed in acidic lysosomes of phagocytes and closely associated with numerous physiological and pathological processes, especially inflammatory response. Fluorescent probe has become an important tool for imaging HClO in lysosomes, but suffered from interference from autofluorescence in vivo, phototoxicity to biosamples and photobleaching phenomenon due to their short-wavelength excitation and emission. Unfortunately, up to now, no near-infrared (NIR) lysosome-targetable fluorescent probe has been reported for imaging HClO. In this paper, a near-infrared fluorescent probe Lyso-NIR-HClO for imaging lysosomal HClO was reported for the first time. Lyso-NIR-HClO based on Si-rhodamine is consisted of a morpholine unit as a lysosome-targetable group and a HClO-mediated cyclization reaction site as a response group, which was applied for highly selective and sensitive detection and imaging for endogenous and exogenous HClO in lysosomes, with a linear range from 5.0 × 10-8 to 1.0 × 10-5 M and a detection limit of 2.0 × 10-8 M in vitro. Attributed to NIR emission and excellent photostability of Si-rhodamine, Lyso-NIR-HClO exhibits excellent performances in vivo, such as low interference from intracellular autofluorescence, stable and persistent fluorescence signal and good tissue penetration, which are in favor of accurate, time-lapse and long-term imaging for HClO. Finally, we applied the probe Lyso-NIR-HClO to visualize endogenous HClO during lysosome-involved inflammatory response including bacteria-infected cells and inflamed mouse model with satisfactory results. The above results proved that Lyso-NIR-HClO would be a potentially useful tool for the study of biological functions and pathological roles of HClO in lysosomes, especially role of lysosome in the inflammatory response.

A novel two-photon fluorescent probe with long-wavelength emission for monitoring HClO in living cells and tissues.

Hypochlorous acid (HClO), one of the most important reactive oxygen species (ROS), is a potent antimicrobial agent for the immune system against invasive bacteria and a wide range of pathogens. Therefore, it is critical to develop sensitive and selective methods for visualization of HClO in biological samples. In this work, a two-photon fluorescent probe HN2-TP) with long-wavelength emission (far-red: 630 nm) based on rhodamine analogue for bioimaging HClO was developed. Owing to a specific HClO induced cyclization reaction, the new probe shows large fluorescence enhancement (about 106-fold), good linear range with high sensitivity (detection limit: 40 nM), high selectivity and fast response when monitoring HClO in vitro. More importantly, by successfully imaging HClO in living cells and tissues, this kind of two-photon fluorescent probe with long-wavelength emission is expected for accurate sensing in complex biosystems, which could eliminate undesired autofluorescence and self-absorption.

The prevalence, subtypes and associated factors of hyperuricemia in lupus nephritis patients at chronic kidney disease stages 1-3.

There is a high prevalence of hyperuricemia (HUA) in the chronic kidney disease (CKD) population. However, there's a dearth of research on HUA's prevalence, subtypes, early detection, and treatment strategies of HUA in lupus nephritis (LN) patients. The aim of this study is to address these knowledge gaps. LN patients presenting to the Department of Nephrology at Shanghai Rui Jin Hospital from January 2011 to January 2016 were recruited. The effective sample size was derived using the power analysis. The demographic, clinical and laboratory characteristics of the LN patients with HUA were compared with those of patients without HUA. Two statistical models for analyzing HUA were built and compared using the receiver operating characteristic (ROC) curve analysis. The total prevalence of HUA in the cohort was 40.11%. The subtypes of HUA included urate underexcretion-type, overproduction-type and combined-type, which proportion being 67.7%, 9.7% and 22.6% respectively. The CKD stage was closely associated with the prevalence of HUA in patients with LN. The other significant associated factors were hypertension, triglycerides, serum creatinine, serum albumin, hemoglobin, parathyroid hormone, phosphorus, calcium, etc. The statistical algorithm successfully identified LN patients at risk of HUA. In conclusion, there was a high prevalence of HUA in LN patients at CKD stages 1-3, and renal underexcretion hyperuricemia was the most prevalent subtype. The occurrence of HUA in LN may be related to renal insufficiency, metabolic disorder and lupus itself. Early care coordination programs can employ risk models to improve HUA prevention and target interventions in LN patients.

The peroxidase and oxidase-like activity of NiCo2O4 mesoporous spheres: Mechanistic understanding and colorimetric biosensing.

The synthesized NiCo2O4 mesoporous spheres (MS) displayed intrinsic peroxidase and oxidase-like activity were firstly reported. The catalytic mechanism of the oxidase-like activity of NiCo2O4 MS was analyzed in detail using the electron spin resonance (ESR) method. It is found that NiCo2O4 MS could directly oxidize 3,3',5,5'-tetramethylbenzidine (TMB) but did not produce 1O2 and ·OH. And the mechanism of the peroxidase-like activity of NiCo2O4 MS was also verified that the oxidation of TMB stemmed from not only ·OH but also 1O2. Based on the NiCo2O4 MS showed excellent peroxidase-like activity over a broad temperature range, especially at normal body temperature, a detection tool was designed for glucose determination in diabetics' serum samples. And this detection method based on NiCo2O4 MS gave a lower limit of detection than the method using Co3O4 NPs and NiO NPs, as the single-component oxides of NiCo2O4. Our study may open up the possibility to make a great influence on the next generation of enzyme mimetics system.

Highly sensitive and selective fluorescent assay for guanine based on the Cu(2+)/eosin Y system.

A fluorescent probe has been developed for the determination of guanine based on the quenched fluorescence signal of Cu(2+)/eosin Y. Cu(2+) interacted with eosin Y, resulting in fluorescence quenching. Subsequently, with the addition of guanine to the Cu(2+)/eosin Y system, guanine reacted with Cu(2+) to form 1:1 chelate cation, which further combined with eosin Y to form a 1:1 ternary ion-association complex by electrostatic attraction and hydrophobic interaction, resulting in significant decrease of the fluorescence. Hence, a fluorescent system was constructed for rapid, sensitive and selective detection of guanine with a detection limit as low as 1.5 nmol L(-1) and a linear range of 3.3-116 nmol L(-1). The method has been applied satisfactorily to the determination of guanine in DNA and urine samples with the recoveries from 98.7% to 105%. This study significantly expands the realm of application of ternary ion-association complex in fluorescence probe.

A unique approach toward near-infrared fluorescent probes for bioimaging with remarkably enhanced contrast.

Near-infrared (NIR) fluorescent probes are attractive molecular tools for bioimaging because of their low autofluorescence interference, deep tissue penetration, and minimal damage to sample. However, most previously reported NIR probes exhibit small Stokes shift, typically less than 30 nm, and low fluorescence quantum yield, strictly limited contrast and spatial resolution for bioimaging. Herein, by expanding the π-conjugated system of rhodamine B, while, at the same time, keeping its rigid and planar structure, we reported an efficient NIR dye, HN7, with large stokes shift of 73 nm and fluorescence quantum yield as high as 0.72 in ethanol, values superior to those of such traditional cyanine NIR dyes as Cy5. Using HN7, living cells, tissues and mice were imaged, and the results showed significantly enhanced contrast, improved spatial resolution, and satisfactory tissue imaging depth when compared to Cy5. Moreover, the nonfluorescent spirocyclic structure of rhodamine B is an inherent component of HN7; therefore, our strategy provided a universal platform for the design of efficient NIR turn-on bioimaging probes for various targets. As a proof-of-concept, two different NIR probes, HN7-N2 and HN7-S for NO and Hg2+, respectively, were designed, synthesized, and successfully applied for the imaging of NO and Hg2+ in living cells, tissues and mice, respectively, demonstrating the potential bioimaging applications of the new probes. In sum, this new type of dye may present new avenues for the development of efficient NIR fluorescent probes for contrast-enhanced imaging in biological applications.

Rhodamine-based fluorescent probe for direct bio-imaging of lysosomal pH changes.

Intracellular pH plays a pivotal role in various biological processes. In eukaryotic cells, lysosomes contain numerous enzymes and proteins exhibiting a variety of activities and functions at acidic pH (4.5-5.5), and abnormal variation in the lysosomal pH causes defects in lysosomal function. Thus, it is important to investigate lysosomal pH in living cells to understand its physiological and pathological processes. In this work, we designed a one-step synthesized rhodamine derivative (RM) with morpholine as a lysosomes tracker, to detect lysosomal pH changes with high sensitivity, high selectivity, high photostability and low cytotoxicity. The probe RM shows a 140-fold fluorescence enhancement over a pH range from 7.4 to 4.5 with a pKa value of 5.23. Importantly, RM can detect the chloroquine-induced lysosomal pH increase and monitor the dexamethasone-induced lysosomal pH changes during apoptosis in live cells. All these features demonstrate its value of practical application in biological systems.

A simple and pH-independent and ultrasensitive fluorescent probe for the rapid detection of Hg2+.

Development of fluorescent probes for Hg(2+) has become a hot topic in modern chemical research due to its high toxicity. In this paper, we for the first time report the synthesis and application of a thioether spirocyclic rhodamine B derivative (TR) as an efficient fluorescent probe for Hg(2+). TR was synthesized using a simple procedure under mild condition. By employing a thioether spirocycle instead of classic spirolactam as recognition unit, our proposed probe TR is acidity-insensitive, and exhibits a pH-independent and ultrasensitive response to Hg(2+). The probe works well within a wide pH range from 3.5 to 11.5, and exhibits a 350-fold fluorescence enhancement upon 0.5 equiv of Hg(2+) triggered, with a detection limit of 2.5 nM estimated for Hg(2+). In virtue of the strong thiophilic characteristic of Hg(2+), the response of the probe to Hg(2+) is instantaneous and highly selective, which make it favorable for cellular Hg(2+) imaging applications. It has been preliminarily used for highly sensitive monitoring of Hg(2+) level in living cells with satisfying resolution, demonstrating its value of the practical applications in biological systems.

Through bond energy transfer: a convenient and universal strategy toward efficient ratiometric fluorescent probe for bioimaging applications.

Fluorescence resonance energy transfer (FRET) strategy has been widely applied in designing ratiometric probes for bioimaging applications. Unfortunately, for FRET systems, sufficiently large spectral overlap is necessary between the donor emission and the acceptor absorption, which would limit the resolution of double-channel images. The through-bond energy transfer (TBET) system does not need spectral overlap between donor and acceptor and could afford large wavelength difference between the two emissions with improved imaging resolution and higher energy transfer efficiency than that of the classical FRET system. It seems to be more favorable for designing ratiometric probes for bioimaging applications. In this paper, we have designed and synthesized a coumarin-rhodamine (CR) TBET system and demonstrated that TBET is a convenient strategy to design an efficient ratiometric fluorescent bioimaging probe for metal ions. Such TBET strategy is also universal, since no spectral overlap between the donor and the acceptor is necessary, and many more dye pairs than that of FRET could be chosen for probe design. As a proof-of-concept, Hg(2+) was chosen as a model metal ion. By combining TBET strategy with dual-switch design, the proposed sensing platform shows two well-separated emission peaks with a wavelength difference of 110 nm, high energy transfer efficiency, and a large signal-to-background ratio, which affords a high sensitivity for the probe with a detection limit of 7 nM for Hg(2+). Moreover, by employing an Hg(2+)-promoted desulfurization reaction as recognition unit, the probe also shows a high selectivity to Hg(2+). All these unique features make it particularly favorable for ratiometric Hg(2+) sensing and bioimaging applications. It has been preliminarily used for a ratiometric image of Hg(2+) in living cells and practical detection of Hg(2+) in river water samples with satisfying results.

Bifunctional fluoroionphore-ionic liquid hybrid for toxic heavy metal ions: improving its performance via the synergistic extraction strategy.

Several heavy metal ions (HMIs), such as Cd(2+), Pb(2+), and Hg(2+), are highly toxic even at very low concentrations. Although a large number of fluoroionphores have been synthesized for HMIs, only a few of them show detection limits that are below the maximum contamination levels in drinking water (usually in the nM range), and few of them can simultaneously detect and remove HMIs. In this work, we report a new fluoroionphore-ionic liquid hybrid-based strategy to improve the performance of classic fluoroionphores via a synergistic extraction effect and realize simultaneous instrument-free detection and removal of HMIs. As a proof-of-concept, Hg(2+) was chosen as a model HMI, and a rhodamine thiospirolactam was chosen as a model fluoroionphore to construct bifunctional fluoroionphore-ionic liquid hybrid 1. The new sensing system could provide obviously improved sensitivity by simply increasing the aqueous-to-ionic liquid phase volume ratio to 10:1, resulting in a detection limit of 800 pM for Hg(2+), and afford extraction efficiencies larger than 99% for Hg(2+). The novel strategy provides a general platform for highly sensitive detection and removal of various HMIs in aqueous samples and holds promise for environmental and biomedical applications.

An efficient rhodamine thiospirolactam-based fluorescent probe for detection of Hg2+ in aqueous samples.

This paper described the optimized design, synthesis and application of a novel rhodamine thiospirolactam derivative as an 'off-on' fluorescent probe for the detection of Hg(2+) in aqueous samples. The 'off-on' fluorescence and color signal change of the probe is based on an Hg(2+)-triggered domino reaction which brings on the opened-ring form of the rhodamine spirolactam to regain the conjugated system of the rhodamine skeleton. In the well designed probe, the thiospirolactam serves as both Hg(2+) binding unit and electron-defect carbon centre, a phenolic hydroxyl with very strong nucleophilicity after deprotonation is chosen as the attacking unit, and a benzene ring is introduced on the linker to afford steric effects, which benefits an efficient nucleophilic reaction, with a high sensitivity towards Hg(2+). It exhibits a stable response for Hg(2+) from 1.0 × 10(-8) to 1.0 × 10(-6) M, with a detection limit of 3.0 × 10(-9) M. The response of the probe to Hg(2+) is highly selective and pH-insensitive, with a fast response time. All these unique features make it particularly favorable for cellular Hg(2+) imaging applications. It has been preliminarily used for highly sensitive monitoring of Hg(2+) levels in living cells with satisfying resolution.

Clicking fluoroionophores onto mesoporous silicas: a universal strategy toward efficient fluorescent surface sensors for metal ions.

Mesoporous SBA-15 silica is an excellent support for constructing fluorescent surface sensors. In this letter, we reported a two-step surface reaction involved strategy to construct efficient fluorescent surface sensors for metal ions by clicking fluoroionophores onto azide-functionalized SBA-15. Our experimental results indicate that such a strategy exhibits an obviously higher loading efficiency within commercial SBA-15 than a previously reported strategy. As a proof-of-concept, a newly designed alkyne-functionalized Hg(2+) fluoroionophore was grafted onto SBA-15 to form a fluorescent Hg(2+) surface sensor. It shows improved sensitivity and selectivity than the fluoroionophore itself working in the solution phase with a detection limit of 2.0 x 10(-8) M for Hg(2+).

Efficient fluorescence resonance energy transfer-based ratiometric fluorescent cellular imaging probe for Zn(2+) using a rhodamine spirolactam as a trigger.

This letter described the design and synthesis of a novel fluorescein-appended rhodamine spirolactam derivative and its preliminary application as a ratiometric fluorescent cellular imaging probe for Zn(2+). The ratiometric fluorescent signal change of the probe is based on an intramolecular fluorescence resonance energy transfer (FRET) mechanism modulated by a specific metal ion induced ring-opening process of the rhodamine spirolactam (acting as a trigger). In the new developed sensing system, the emission peaks of the two fluorophores are well-resolved, which can avoid the emission spectra overlap problem generally met by spectra-shift type probes and benefits for observation of fluorescence signal change at two different emission wavelengths with high resolution. It also benefits for a large range of emission ratios, thereby a high sensitivity for Zn(2+)detection. Under optimized experimental conditions, the probe exhibits a stable response for Zn(2+) over a concentration range from 2.0 x 10(-7) to 2.0 x 10(-5) M, with a detection limit of 4.0 x 10(-8) M. Most importantly, the novel probe has well solved the problem of serious interferences from other transition metal ions generally met by previously reported typical fluorescent probes for Zn(2+) with the di(2-picolyl)amine moiety as the receptor (in this case, the fluorescence response induced by Cd(2+)is even comparable to that of Zn(2+)) and shows a reversible and fast response toward Zn(2+). All these unique features make it particularly favorable for ratiometric cellular imaging investigations. It has been preliminarily used for ratiometric imaging of Zn(2+) in living cells with satisfying resolution.