Silver nanoparticle induced chemiluminescence of the hexacyanoferrate-fluorescein system, and its application to the determination of catechol

Synergistic enhancement of fluorescein-K3[Fe(CN)6] CL by MoO3-x NPs for sensitive and noninvasive detection of uric acid in saliva

MoO3-x NPs was rapidly synthesized at room temperature by an easy stirring method. It was interesting to find that MoO3-x NPs induce OH- to generate active free radicals (ROS), which is a highly promising property in chemiluminescence (CL). Benefiting from the abundant oxygen vacancy, MoO3-x NPs adsorbs H2O2 and turn it into ·OH. The oxidase activity of fluorescein under visible light had already been reported, which catalyzes dissolved oxygen to become O2-· and continue to convert to H2O2. By creating the synergy effect with fluorescein, MoO3-x NPs strengthen the CL intensity of K3[Fe(CN)6]-fluorescein system significantly. Utilizing the quench effect of uric acid for the CL intensity, we developed a rapid, simple, and highly sensitive CL platform for uric acid detection. The linear range was 5-80 µM and the detection limit (LOD) for uric acid was 3.11 µM (S/N = 3). This work expanded the application of MoO3-x NPs in the CL field and developed a simple and highly sensitive CL sensing system to detect UA in human saliva.

Direct synthesis of highly porous interconnected carbon nanosheets from sodium d-isoascorbic acid for the simultaneous determination of catechol and hydroquinone

Interconnected porous carbon was prepared by pyrolyzing sodium d-isoascorbic acid. An electrochemical sensor for simultaneous detection of hydroquinone and catechol was fabricated by modification with porous carbon on the glassy carbon electrode surface.

Directed aryl sulfotransferase evolution toward improved sulfation stoichiometry on the example of catechols

Sulfation is an important way for detoxifying xenobiotics and endobiotics including catechols. Enzymatic sulfation occurs usually with high chemo- and/or regioselectivity under mild reaction conditions. In this study, a two-step p-NPS-4-AAP screening system for laboratory evolution of aryl sulfotransferase B (ASTB) was developed in 96-well microtiter plates to improve the sulfate transfer efficiency toward catechols. Increased transfer efficiency and improved sulfation stoichiometry are achieved through the two-step screening procedure in a one-pot reaction. In the first step, the p-NPS assay is used (detection of the colorimetric by-product, p-nitrophenol) to determine the apparent ASTB activity. The sulfated product, 3-chlorocatechol-1-monosulfate, is quantified by the 4-aminoantipyrine (4-AAP) assay in the second step. Comparison of product formation to p-NPS consumption ensures successful directed evolution campaigns of ASTB. Optimization yielded a coefficient of variation below 15% for the two-step screening system (p-NPS-4-AAP). In total, 1760 clones from an ASTB-SeSaM library were screened toward the improved sulfation activity of 3-chlorocatechol. The turnover number (k_cat = 41 ± 2 s^-1) and catalytic efficiency (k_cat/K_M = 0.41 μM^-1 s^-1) of the final variant ASTB-M5 were improved 2.4- and 2.3-fold compared with ASTB-WT. HPLC analysis confirmed the improved sulfate stoichiometry of ASTB-M5 with a conversion of 58% (ASTB-WT 29%; two-fold improvement). Mass spectrometry (MS) and nuclear magnetic resonance spectroscopy (NMR) confirmed the chemo- and regioselectivity, which yielded exclusively 3-chlorocatechol-1-monosulfate. For all five additionally investigated catechols, the variant ASTB-M5 achieved an improved k_cat value of up to 4.5-fold and sulfate transfer efficiency was also increased (up to 2.3-fold).

Fluorometric determination of hydroquinone by using blue emitting N/S/P-codoped carbon dots

N/S/P-codoped carbon dots (CDs) are shown to be a viable fluorescent probe in a turn-off-on fluorometric assay for hydroquinone (HQ). The preparation of CDs was carried out using a one-step hydrothermal reaction starting with glyoxal and isocarbophos. The method is based on the formation of ground state complexes between CD and Fe(III) which leads to quenching of blue fluorescence (with excitation/emission peaks at 363/448 nm). On addition of HQ, it will be oxidized by Fe(III) upon which fluorescence recovers. This turn-off-on system can be utilized to quantify HQ. A linear relationship exists between fluorescence recovery and HQ concentration in range between 0.56 and 375 μM. The limit of detection is 0.16 μM. The assay was successfully applied to the determination of HQ in spiked water samples and developer samples. Graphical abstract Fluorometric determination of hydroquinone (with good selectivity over catechol and resorcinol) by using blue-emitting N/S/P-codoped carbon dots and the quenching effect of Fe(III).

Highly sensitive determination of diclofenac based on resin beads and a novel polyclonal antibody by using flow injection chemiluminescence competitive immunoassay

A novel flow injection chemiluminescence immunoassay for simple, sensitive and low-cost detection of diclofenac was established based on specific binding of antigen and antibody. Carboxylic resin beads used as solid phase carrier materials provided good biocompatibility and large surface-to-volume ratio for modifying more coating antigen. There was a competitive process between the diclofenac in solution and the immobilized coating antigen to react with the limited binding sites of the polyclonal antibody to form the immunocomplex. The second antibody labelled with horseradish peroxidase was introduced into the immunosensor and trapped by captured polyclonal antibody against diclofenac, which could effectively amplify chemiluminescence signals of luminol-PIP-H₂O₂. Under optimal conditions, the diclofenac could be detected quantitatively. The chemiluminescence intensity decreased linearly with the logarithm of the diclofenac concentration in the range of 0.1-100ngmL^-1 with a detection limit of 0.05ngmL^-1 at a signal-to-noise ratio of 3. The immunosensor exhibited high sensitivity, specificity and acceptable stability. This easy-operated and cost-effective analytical method could be valuable for the diclofenac determination in real water samples.

Flow analysis with chemiluminescence detection: Recent advances and applications

This article highlights the most important developments in flow analysis with chemiluminescence (CL) detection, describing different flow systems that are compatible with CL detection, detector designs, commonly applied CL reactions and approaches to sample treatment. Recent applications of flow analysis with CL detection (focusing on outputs published since 2010) are also presented. Applications are classified by sample matrix, covering foods and beverages, environmental matrices, pharmaceuticals and biological fluids. Comprehensive tables are provided for each area, listing the specific sample matrix, CL reaction used, linear range, limit of detection and sample treatment for each analyte. Finally, recent and emerging trends in the field are also discussed.