Ratiometric fluorescence probe based on carbon dots and p-phenylenediamine-derived nanoparticles for the sensitive detection of manganese ions.

A ratiometric fluorescence probe based on carbon quantum dots with 420 nm emission (bCQDs) and a p-phenylenediamine-derived fluorescence probe with 550 nm emission (yprobe) is constructed for the detection of Mn2+. The presence of Mn2+ results in the enhanced absorption band at 400 nm of yprobe, and the fluorescence of yprobe is significantly enhanced based on the chelation-enhanced fluorescence mechanism. The fluorescence of bCQDs is then quenched based on the inner filtration effect. The ratio (I550/I420) linearly increases with the increase of Mn2+ concentration within 2.00 × 10-7-1.50 × 10-6 M, and the limit of detection is 1.76 × 10-9 M. Given the fluorescence color changing from blue to yellow, the visual sensing of Mn2+ is feasible based on bCQDs/yprobe coupled with RGB value analysis. The practicability of the proposed method has been verified in tap water, lake water, and sparkling water beverage, indicating that bCQDs/yprobe has promising application in Mn2+ monitoring.

Investigation of the Application and Mechanism of Nitrogen and Phosphorus Co-doped Carbon Dots for Mercury Ion Detection.

In this paper, we obtained nitrogen and phosphorus co-doped carbon dots through a hydrothermal method using o-phenylenediamine and citric acid in a 40% phosphoric acid environment. The carbon dots emitted fluorescence at 476 nm under excitation at 408 nm and exhibited good selectivity and high sensitivity towards mercury ions. These carbon dots showed excellent dispersibility in water and maintained stable fluorescence even in high concentration salt environments. The interaction between mercury ions and functional groups on the carbon dots surface through electrostatic interaction resulted in static quenching. Simultaneously, by detecting the lifetime and transient absorption spectra of the carbon dots, we observed that the coordination of mercury ions with the carbon dots broadened the band structure of the carbon dots, and the existing photoinduced electron transfer process increased the non-radiative transition channel. The combined effect of dynamic quenching and static quenching significantly reduced the fluorescence intensity of the carbon dots at 476 nm. The carbon dots exhibited linear detection of mercury ions in the range of 0.01-1 µM, with a detection limit as low as 0.0245 µM. In terms of practical water environmental detection applications, these carbon dots were able to effectively detect mercury ions in tap water and lake water, demonstrating their broad application prospects in the field of environmental metal analysis.

o-phenylenediamine Derived Fluorescent Carbon Quantum dots for Detection of Hg(II) in Environmental Water.

With the expansion of human activities, the consequent influx of mercury (Hg) into the food chain and the environment is seriously threatening human life. Herein, nitrogen and sulfur co-doped fluorescent carbon quantum dots (yCQDs) were prepared via a hydrothermal method using o-phenylenediamine (OPD) and taurine as precursors. The morphological characteristics as well as spectral features of yCQDs indicated that the photoluminescence mechanism should be the molecular state fluorophores of 2, 3-diaminophenothiazine (oxOPD), which is the oxide of OPD. The as-synthesized yCQDs exhibited sensitive recognition of Hg2+. According to the investigation in combination of UV-Vis absorption spectra, time-resolved fluorescence spectra and quantum chemical calculations, the abundant functional groups on the surface of yCQDs allowed Hg2+ to bind with yCQDs through various interactions, and the formed complexes significantly inhibited the absorption of excitation light, resulting in the static fluorescence quenching of yCQDs. The proposed yCQDs was utilized for Hg2+ sensing with the limit of detection calculated to be 4.50 × 10- 8 M. Furthermore, the recognition ability of yCQDs for Hg2+ was estimated in tap water, lake water and bottled water, and the results indicated that yCQDs have potential applications in monitoring Hg2+.

Al2O3@Ag composite structure as SERS substrate for sensitive detection of sodium thiocyanate.

Sodium thiocyanate (NaSCN) can be added to fresh milk to enhance the sterilization ability of the lactoperoxidase system (LP system) in milk, extending shelf life. However, excessive intake of NaSCN can be harmful to human health because it can prevent absorption of iodine leading to disease. Also NaSCN can be used as a marker to distinguish smokers from non-smokers. In this work, we successfully synthesized meatball-like Al2O3@Ag composite structures as surface-enhanced Raman scattering (SERS) substrates using a simple wet chemical method adapted to conventional laboratory conditions. The substrate exhibited strong SERS enhancement for NaSCN. Under the optimal experiment conditions, we obtained a detection limit of 0.28 µg L-1 and a quantification limit of 1 µg L-1, R2 = 0.992. Based on the analysis of the intensity of SERS characteristic peak, the substrate had good reproducibility and uniformity. In summary, the Al2O3@Ag composite structure achieved sensitive SERS detection of NaSCN. Combining the facile and low-cost methods, we believe that the SERS detection method developed in this work can be used as a potential candidate for biosensing applications in the future.

Effect of Zn2+ on emodin molecules studied by time-resolved fluorescence spectroscopy and quantum chemical calculations.

Emodin is a natural drug for treating neurodegenerative diseases and plays a vital role in the mitigation of nerve damage. Metal ions can modify the drug properties of emodin, where Zn2+ can synergize with the emodin molecule and enhance the drug effect of emodin. Besides, complex changes can be observed in the fluorescence intensity and fluorescence lifetime of the emodin molecule as the concentration of Zn2+ increases. Herein, the synergistic effects of ligand structural in Zn(II)-Emodin complexes and the electronic effects of metal elements on the antioxidant properties of the complexes are discussed in detail based on UV-vis absorption spectroscopy, fluorescence spectroscopy, time-correlated single photon counting (TCSPC) technique and quantum chemical calculations at the B3LYP/6-31G(d) level. The experimental results confirm that Zn2+ can coordinate with the hydroxyl groups on the emodin to make the molecule structure more rigid, thus inhibiting the non-radiative processes such as high-frequency vibrations of the emodin molecule in solution. The suppression of non-radiative processes leads to an increase in the average fluorescence lifetime of the emodin molecule, and finally results in the enhanced fluorescence intensity. The chemical softness of Zn(II)-Emodin is then confirmed to be higher than that of emodin by Gaussian calculations, indicating its higher chemical reactivity and lower stability. The stronger electron donating ability of Zn(II)-Emodin compared to emodin may explain the higher antioxidant activity of Zn(II)-Emodin, which gives it a stronger pharmacological activity. The results of this study show that emodin can well complex with Zn2+ to remove excess Zn2+ in human body and the resulting complex has better antioxidant properties, which helps to understand the role of Zn2+ in drug-metal coordination and provides guidance for the design of new drugs.

A fluorescent probe based on FRET effect between carbon nanodots and gold nanoparticles for sensitive detection of thiourea.

Illegal abuse results in the presence of thiourea (TU) in soil, wastewater, and even fruits, which is harmful for the environment and human health. It has urgent practical significance to design an efficient and reliable probe for TU detection. Herein, a sensitive fluorescent probe with off-on response for harmful TU was reported. The probe was designed with fluorescent carbon nanodots (CNDs) and gold nanoparticles (AuNPs) based on fluorescence resonance energy transfer (FRET) effect. Firstly, the CNDs were pre-combined with AuNPs and the fluorescence of CNDs was quenched due to the FRET effect. Upon addition of TU, the fluorescence of CNDs recovered due to the unbinding of CNDs and AuNPs, since the coordination interaction between TU and AuNPs is stronger than the electrostatic interaction among CNDs and AuNPs. Under the optimum parameters, a linear relationship was found between the relative fluorescence intensity of the probe and the concentration of TU in the range of 5.00 × 10-8-1.00 × 10-6 M (R2 = 0.9958), with the limit of detection (LOD) calculated to be 3.62 × 10-8 M. This proposed method is easy to operate and has excellent selectivity and sensitivity for TU, which can be effectively applied in environmental water and compound fruit-vegetable juice.

Sensitive determination of Norfloxacin in milk based on ß-cyclodextrin functionalized silver nanoparticles SERS substrate.

The norfloxacin (NFX) residue in milk will increase human resistance to drugs and pose a threat to public health. In this work, a highly sensitive method for detection of NFX was developed based on surface enhanced Raman spectroscopy (SERS) using ß-cyclodextrin functionalized silver nanoparticles (ß-CD-AgNPs) as substrate. The unique spatial size and hydrophilicity of ß-CD on the surface of AgNPs could selectively capture the target molecule (NFX) through some weak interactions, including hydrogen-bond interaction, electrostatic interaction, etc. The interactions were characterized by the UV-Vis absorption spectroscopy, fluorescence spectroscopy, Zeta potential and DLS. The Raman signal of NFX is largely enhanced when anchored by ß-CD on the surface of AgNPs due to SERS effect. Through a series of experiments and analysis, the limit of detection (LOD) in standard solution and spiked milk were calculated to be 3.214 pmol/L and 5.327 nmol/L. The correlation coefficients (R2) were 0.986 and 0.984, respectively. For milk sample determination of NFX, the recovery was 101.29% to 104.00% with the relative standard deviation (RSD) from 2.986% to 9.136%. To sum up, this developed SERS strategy is sensitive and specific to detect NFX in milk, it has practical application value and prospects.

Tonsillar CD4+CD25+ regulatory T cells from IgA nephropathy patients have decreased immunosuppressive activity in experimental IgA nephropathy rats.

BACKGROUND/AIM: CD4+CD25+ regulatory T (Treg) cells are of critical importance for maintenance of tolerance. We showed that the number of CD4+CD25+ Treg cells was significantly lower in tonsils of patients with IgA nephropathy (IgAN); however, the function of tonsillar CD4+CD25+ Treg cells in IgAN has not been reported. The aim of this study was to investigate the effect of tonsillar CD4+CD25+ Treg cells of IgAN patients on experimental IgAN in rats. METHODS: Tonsillar CD4+CD25+ Treg cells were isolated by magnetic beads. A total of 2 × 10(6) CD4+CD25+ Treg cells were transferred into rats that were previously orally immunized over a period of 14 weeks and subsequently received an injection of BSA into the tail vein on 3 consecutive days. Urine protein and erythrocytes were measured. Glomerular injury was assessed by histopathology. Plasminogen activator inhibitor type 1 (PAI-1), interleukin (IL)-6 and transforming growth factor (TGF)-ß1 in mesangial cells of rats were examined by reverse transcription PCR. Serum IgA and C3 and supernatants of IL-2, IL-4 and IL-6 in splenic cells were analysed by ELISA. Transferred tonsillar CD4+CD25+ Treg cells were tracked by reverse transcription PCR and flow cytometry. RESULTS: IgA deposition in the mesangial region and the glomerular planar area and the number of cells, levels of serum IgA and supernatant IL-2, IL-4 and IL-6 in splenic cells and PAI-1, IL-6 and TGF-ß1 expression in renal mesangial cells of rats that received CD4+CD25+ Treg cells from IgAN patients were significantly higher than in rats that received CD4+CD25+ Treg cells from the control group, although they were dramatically lower compared with rats treated without CD4+CD25+ Treg cells. Transferred tonsillar CD4+CD25+ Treg cells migrated predominantly to secondary lymphoid organs but not to the kidneys. CONCLUSION: Dysfunction of tonsillar CD4+CD25+ Treg cells may be an important cause of IgAN progression.

Renal function and serum albumin at the start of dialysis in 514 Chinese ESRD in-patients.

BACKGROUND: The dialysis population has grown rapidly in recent decades. Despite the high cost and poor outcomes of dialysis treatment for ESRD, there are scant data about the level of renal function and the relationship of renal function and serum albumin at the start of dialysis in Chinese ESRD patients. METHOD: We report the level of serum creatinine (Scr), glomerular filtration rate (GFR), and serum albumin (Salb) in 514 ESRD in-patients who began their dialysis treatment between January 2001 through December 2007 at two large dialysis centers in Changsha, Hunan, China. Data were obtained through reviewing the case records of all 514 patients. GFR was predicted by an equation developed from the Modification of Diet in Renal Disease Study. In addition, serum albumin was analyzed in relation to levels of predicted GFR. RESULTS: The mean (SD) and median predialysis serum creatinine was 1121.92 +/- 458.24 and 1032 micromol/L. The mean (SD) and median predicted GFR was 4.98 +/- 2.24 and 4.47mL/min/1.73m(2). The proportion of patients with predicted GFR of >10, 5 to 10, and <5 mL/min/1.73m(2) was 3.7, 36.2, and 60.1%, respectively. The mean predicted GFR was significantly lower among younger patients, uninsured patients, unemployed or farmer patients, patients who were employed, students, patients who selected hemodialysis, patients with ESRD caused by diseases other than diabetes, patients with BUN above the mean, and patients with hemoglobulin beneath the mean. Compared with patients who started with GFR >5mL/min, the patients who started with GFR

[Randomized controlled study of S (+) -ismer of ibuprofen supporsitory].

OBJECTIVE: To evaluate the efficacy and safety of S (+) - ismer of ibuprofen supporsitory. METHODS: One hundred and three cases of postopterative pain and 60 cases of fever, altogether 163 patients were randomly divided into 2 groups: S (+) -ismer of ibuprofen supporsitory treatment group (one supporsitory per day for 3 days) and ibuprofen supporsitory treatment group (one supporsitory per day for 3 days). The therapeutic effect was assessed and the side-effects were observed between the 2 groups. RESULTS: After being given medicine in the first 4 hours, pain intensity difference, pain remission degree and the dropped level of fever in S (+) -ismer of ibuprofen were all bigger than those of the ibuprofen supporsitory treatment group. There was no difference in side-effects between the 2 groups. CONCLUSION: Therapeutic effect of S (+) -ismer of ibuprofen supporsitory is definite, whose action appears more quickly and stronger and it has fewer side-effects than those of ibuprofen supporsitory.