Single-holed cobalt - nitrogen - carbon hollow structure with oxidase-mimicking activity for the chemiluminescence determination of ß - galactosidase activity.

A single-holed cobalt - nitrogen - carbon (Co - N - C) hollow structure nanozyme has been fabricated by in situ growth of zeolitic imidazolate framework (ZIF - 67) on the polystyrene (PS) sphere and following treatment by high-temperature carbonization. The Co - N - C nanostructure mimics the activity of oxidase and can activate O2 into reactive oxygen species (ROS), giving a remarkable enhancement on the chemiluminescence (CL) signal of luminol - O2 reaction. The Co - N - C oxidase mimic has further been exploited in the biosensing field by the determination of the activity of ß - galactosidase (ß - gal). The CL method for ß - gal activity has a linear range of 0.5 mU·L-1 to 5.0 U·L-1, a detection limit of 0.167 mU·L-1, and the precision of 3.1% (5.0 U·L-1, n = 11). This method has been employed to assess inhibitor screening of ß - gal and determine activity of ß - gal in spiked human serum samples.

An Aggregation-Induced Emission Nanosensor for Real-Time Chemiluminescent Sensing of Light-Independent Intracellular Singlet Oxygen.

Characterizing the transient ultratrace light-independent intracellular singlet oxygen (1O2), which plays a vital role in multiple biological processes in living organisms, brings about tremendous help for understanding the nature of 1O2-mediated or related bioevents. Nevertheless, an approach to detect the light-independent intracellular 1O2 is hard to find. Herein, we developed a chemiluminescent nanosensor by compacting a great number of TPE-N(Ph)-DBT-PH molecules in one nanostructure via autoaggregation. Taking advantage of the aggregation-induced emission property, this TPE-N(Ph)-DBT-PH nanosensor is highly fluorescent and promises a bright red-light CL and the convenience of mapping in vivo sensor distribution. Experiments demonstrate the nanosensor's unprecedented selectivity toward 1O2 against other reactive oxygen species. The 3.7 nmol L-1 limit of detection renders this nanosensor with the best-known sensitivity of 1O2 chemical sensors. Meanwhile, fluorescence confocal microscope imaging results suggest that our nanosensor simultaneously targets mitochondria and lysosomes in RAW 264.7 cells via the energy-dependent endocytosis pathway, thereby implying an attractive potential for the detection of intracellular 1O2. Such a potential is demonstrated by detecting 1O2 in RAW 264.7 cells during a lipopolysaccharide and phorbol myristate acetate stimulated respiration burst. This study represents the first approach to detect light-independent intracellular 1O2 during cell bioregulation. Thus, our nanosensor provides an effective tool for investigating the 1O2-related bioprocesses and pathological processes.

Real-Time Mapping of Ultratrace Singlet Oxygen in Rat during Acute and Chronic Inflammations via a Chemiluminescent Nanosensor.

Sensing nonradiation-induced singlet oxygen (1 O2 ) in whole-animal is deemed as one of the most challenging tasks in noninvasive techniques due to the µs level lifetime of 1 O2 and quenching by numerous reductants in tissues. Here a distinct chemiluminescent (CL) nanosensor (NTPE-PH) that boasts ultrahigh concentrated CL units in one nanoparticle is reported. Taking advantage of the intramolecular energy transfer mechanism that promises high energy transfer efficiency and the aggregation-induced emission behavior that guarantees high CL amplification, the NTPE-PH sensor is sensitive to a nm level 1 O2 . Experiments demonstrate that the NTPE-PH yields a highly selective CL response toward 1 O2 among common reactive oxygen species. With proved low cytotoxicity and good animal compatibility, real-time mapping of ultratrace 1 O2 in whole-animal during acute and chronic inflammations is first achieved. It is anticipated that the NTPE-PH sensor can be a useful tool for monitoring 1 O2 variation during immune response and pathological processes corresponding to different stimuli, even with drug treatment included.

A novel thermometer-type hydrogel senor for glutathione detection.

A thermometer-type visual sensor for glutathione (GSH) sensing was developed with stimulus-responsive fluorescent hydrogel which was obtained by using 5, 6-bicarboxylic fluorescein crossli`nked partly ammoniated polyacrylamide. Various experimental parameters such as the particle size of hydrogel, buffer solution and swelling time were optimized. It is accessible to measure the volume change of hydrogel with the sensor by reading the graduation on a pipette like thermometer with naked eye. The concentration of the GSH depended on the volume in a certain range as the signal. Satisfactory agreements between the sensor and HPLC results for atuomolan tablet assays indicated the capability of the thermometer-type sensors for the analysis of real samples. These findings proved the utility of stimulus-responsive, intelligent hydrogel and the suitability of thermometer-style visual sensor design for quantitative assays.

Self-Catalyzing Chemiluminescence of Luminol-Diazonium Ion and Its Application for Catalyst-Free Hydrogen Peroxide Detection and Rat Arthritis Imaging.

We report the unique self-catalyzing chemiluminescence (CL) of luminol-diazonium ion (N2+-luminol) and its analytical potential. Visual CL emission was initially observed when N2+-luminol was subjected to alkaline aqueous H2O2 without the aid of any catalysts. Further experimental investigations found peroxidase-like activity of N2+-luminol on the cleavage of H2O2 into OH• radical. Together with other experimental evidence, the CL mechanism is suggested as the activation of N2+-luminol and its dediazotization product 3-hydroxyl luminol by OH• radical into corresponding intermediate radicals, and then further oxidation to excited-state 3-N2+-phthalic acid and 3-hydroxyphthalic acid, which finally produce 415 nm CL. The self-catalyzing CL of N2+-luminol provides us an opportunity to achieve the attractive catalyst-free CL detection of H2O2. Experiments demonstrated the 10-8 M level detection sensitivity to H2O2 as well as to glucose or uric acid if presubjected to glucose oxidase or uricase. With the exampled determination of serum glucose and uric acid, N2+-luminol shows its analytical potential for other analytes linking the production or consumption of H2O2. Under physiological condition, N2+-luminol exhibits highly selective and sensitive CL toward 1O2 among the common reactive oxygen species. This capacity supports the significant application of N2+-luminol for detecting 1O2 in live animals. By imaging the arthritis in LEW rats, N2+-luminol CL is demonstrated as a potential tool for mapping the inflammation-relevant biological events in a live body.

A visual volumetric hydrogel sensor enables quantitative and sensitive detection of copper ions.

We propose a visual volumetric sensor with 5,6-dicarboxylic fluorescein cross-linked amine-functionalized polyacrylamide hydrogel. The sensor undergoes volume response to Cu(2+) ions at the µM level, which enables naked-eye quantitative detection by reading the graduation on a pipette.

A siphonage flow and thread-based low-cost platform enables quantitative and sensitive assays.

For pump-free, material abundant, portable, and easy-to-operate low-cost microfluidics, a siphonage flow microfluidic thread-based analytical device (S-µTAD) platform enabling quantitative and sensitive assays was designed. Renewable and continuous siphonage flow allowed replicate sampling and detection on one channel/device, obviating some possible inconsistencies among channels or devices. Y-shaped channels were fabricated with polyester cotton blend thread, due to its greater chemiluminescent sensitivity in comparison with that of cotton and polyester threads. S-µTAD sensors for glucose and uric acid were fabricated by using oxidase-immobilized cotton thread as the sample arm of the channels. The acceptable reproducibility and high sensitivity, demonstrated by the relative standard deviations of less than 5% in all cases and the detection limits of 4 × 10(-8) mol L(-1) for hydrogen peroxide, 1 × 10(-7) mol L(-1) for glucose, and 3 × 10(-6) mol L(-1) for uric acid, demonstrated the feasibility of the S-µTAD for quantitative assays. Good agreements between S-µTAD/sensor results and hospital results for blood glucose and uric acid assays indicated the capability of S-µTAD/sensors for the analysis of real samples. These findings proved the utility of siphonage for low-cost microfluidics and the suitability of our S-µTAD design for quantitative assays.

A high-performance liquid chromatography:chemiluminescence method for potential determination of vardenafil in dietary supplement.

A flow method of high-performance liquid chromatography (HPLC) seperation and chemiluminescence (CL) detection for sensitive vardenafil analysis in dietary supplements was developed. The vardenafil separation was achieved on a C18 column at 30°C using ethanol-H(3)PO(4) and ethylenediaminetetraacetic acid disodium salt (Na(2)EDTA) aqueous solution (25 : 75, v/v%) as mobile phase. The followed continuous CL detection was conducted based on the strong CL enhancement by the presence of vardenafil to luminol-K(3)Fe(CN)(6) reaction in alkaline medium. At the flow rate of 0.8 mL/min, the vardenafil retention time (t(R)) was 6.4 min. Factors that affected the HPLC resolution and CL detection were studied and optimized. The calibration curve obtained for vardenafil standard was linear in concentration range of 8.0 × 10(-7) ~ 1.0 × 10(-4) mol/L. The relative standard deviations (RSD) of intraday and interday precision were less than 3.5%. The proposed method was applied to the vardenafil determination in oral liquid, wine, and capsule samples.

Three-dimensional positron emission tomography/computed tomography analysis of 13NO3- uptake and 13N distribution in growing kohlrabi.

We report the application of three-dimensional positron emission tomography/computed tomography (PET/CT) for the analysis of (13)NO(3)(-) uptake and (13)N distribution in growing kohlrabi. The analytical procedures, equipment parameters, and image reconstruction mode for plant imaging were tested and selected. (13)N in growing kohlrabi plants was imaged versus time using both PET movies and PET/CT tomograms. The (13)NO(3)(-) transport velocity in kohlrabi from root to petiole was estimated to be 1.0 cm/min. The appearance of shell-shaped (13)NO(3)(-) transport pathways, corresponding to the kohlrabi corm, suggests the existence of special routes with higher efficiency for (13)NO(3)(-) transport, which tends to have the shortest distances to the leaves or buds. Standardized uptake values (SUVs), used as the representative figures for describing (13)N distribution, were quantified versus time at some putative sites of interest. For multiple analysis of the same-plant, (13)N distribution in kohlrabi under normal conditions, methionine sulfoximine (MSX) stress, and recovery from MSX stress was examined. The (13)N distribution variation studies were also done under the above three growth conditions. Our results suggest a significant downregulation of nitrate uptake in kohlrabi in the presence of MSX.

Utilizing multibubble sonophotoluminscence for calcium quantitative analysis in pharmaceuticals.

Sonoluminescence can photoexcite fluorescent solutes yielding sonophotoluminescence (SPL). The possibility of applying multibubble sonophotoluminescence (MBSPL) for chemical quantitative analysis is examined in this work. Special devices for MBSPL quantitative detection are designed and fabricated. Calcium contents in pharmaceutical samples are selected to verify the proposed MBSPL analysis. Coupled with flow fluid manifold, high detection frequency, good reproducibility and automatic operation are obtained. Further applications of presented method to detecting a variety of chemical or biochemical molecules in low quantities are expected.

Determination of phenol at ng l-1 level by flow-injection chemiluminescence combined with on-line solid-phase extraction.

In this paper, a simple flow-injection chemiluminescence (CL) system combined with on-line solid-phase extraction is presented to determine phenol. This method is based on the enhancement effect of phenol on the luminol-K3Fe(CN)6 CL system. The solid-phase extraction promised the high sensitivity and improved selectivity of CL detection. With the calibration range from 4.7 ng l-1 to 470 ng l-1 phenol concentration, the proposed method was applied to analyzing phenol in water samples and the obtained results were validated by the standard method. The detection limit was determined as 0.66 ng l-1. The relative standard deviation was 1.5% for determining 4.7 ng l-1 phenol standard (n=7).

Flow injection chemiluminescence detection and solvent extraction for human skin ointment dexamethasone acetate absorption analysis and the reaction mechanism study.

A flow-injection chemiluminescence (CL) method coupled with solvent extraction for the determination of dexamethasone acetate (DA) in ointment was presented in this paper. It was based on the enhancing effect of the studied drug on CL emission of luminol-K(3)Fe(CN)(6) system. This method has the advantages of simple sample treatment, cheap instrumentation and rapid detection. Under the optimum conditions, relative CL intensities were proportional to DA concentrations in the 0.044-4.4 microg ml(-1) range. The limit of detection was 0.01 microg ml(-1) (3sigma) for DA. The method was applied to DA quantification in commercial DA ointment pharmaceutical and to human skin DA absorption analysis. Experiments were performed to evaluate the nature of DA enhanced luminol-K(3)Fe(CN)(6) CL reaction. Based on the experimental results, it was suggested that in this CL system, DA was oxidized by K(3)Fe(CN)(6) to form a medium product (DAox), DAox oxidized luminol with a faster kinetic step comparing with K(3)Fe(CN)(6) oxidized luminol to an active form. As a result, DA speed the luminol CL reaction, and finally intensified the CL signal.

Chemometrics-assisted simultaneous determination of cobalt(II) and chromium(III) with flow-injection chemiluminescence method.

In this paper, a flow-injection chemiluminescence (CL) system is proposed for simultaneous determination of Co(II) and Cr(III) with partial least squares calibration. This method is based on the fact that both Co(II) and Cr(III) catalyze the luminol-H(2)O(2) CL reaction, and that their catalytic activities are significantly different on the same reaction condition. The CL intensity of Co(II) and Cr(III) was measured and recorded at different pH of reaction medium, and the obtained data were processed by the chemometric approach of partial least squares. The experimental calibration set was composed with nine sample solutions using orthogonal calibration design for two component mixtures. The calibration curve was linear over the concentration range of 2 x 10(-7) to 8 x 10(-10) and 2 x 10(-6) to 4 x 10(-9) g/ml for Co(II) and Cr(III), respectively. The proposed method offers the potential advantages of high sensitivity, simplicity and rapidity for Co(II) and Cr(III) determination, and was successfully applied to the simultaneous determination of both analytes in real water sample.

Flow-injection chemiluminescence simultaneous determination of cobalt(II) and copper(II) using partial least squares calibration.

A flow-injection chemiluminescence (CL) system is proposed for simultaneous determination of Co(2+) and Cu(2+) using partial least squares (PLS) calibration. This method is based on the fact that both Co(2+) and Cu(2+) catalyse the CL reaction of luminol-H(2)O(2), and that their kinetic characteristics of Co(2+) and Cu(2+) are significantly different in the luminol-H(2)O(2) system. The CL intensity was measured and recorder at different reaction times of luminol-H(2)O(2)Co(2+)Cu(2+), and the obtained data were processed by the chemometric approach of partial least squares. The experimental calibration set was composed of 16 sample solutions using an orthogonal calibration design for two component mixtures. The proposed method offers the potential advantages of high sensitivity, simplicity and rapidity for Co(2+) and Cu(2+) determination, and was successfully applied to the simultaneous determination of both analytes in real water sample. The present paper demonstrated that the simultaneous determination of two metal ions without any prior separation has been possible using flow-injection CL system.

Simultaneous determination of rifampicin and isoniazid by continuous-flow chemiluminescence with artificial neural network calibration.

In this paper a continuous-flow chemiluminescence (CL) system with artificial neural network calibration is proposed for simultaneous determination of rifampicin and isoniazid. This method is based on the different kinetic spectra of the analytes in their CL reaction with alkaline N-bromosuccinimide as oxidant. The CL intensity was measured and recorded every second from 1 to 300 s. The data obtained were processed chemometrically by use of an artificial neural network. The experimental calibration set was 20 sample solutions. The relative standard errors of prediction for both analytes were approximately 5%. The proposed method was successfully applied to the simultaneous determination of rifampicin and isoniazid in a combined pharmaceutical formulation.

A micro-chemiluminescence determination of cyanide in whole blood.

A reactant volume self-controlled micro-device was presented and applied to the flow injection chemiluminescence (CL) for determination of cyanide in whole blood. A mini distiller was fabricated for cyanide extraction from the blood samples with the extraction efficiencies of cyanide > or = 98%. A fluidic control platform with air driving was fabricated. The described system showed the features of easy fabrication, undiluted sample injection, safe analysis operation, and suitability for automatic cyanide analysis. The calibration curve showed linearity in the cyanide concentration range of 5.0 x 10(-7) to 5.0 x 10(-5) mol l(-1) with the detection limits (3sigma) of 2.3 x 10(-7) mol l(-1). CL peak-height precision was 1.9% R.S.D. (n = 11) at the 1.0 x 10(-6) mol l(-1) cyanide level. The new devices were applied to the analysis of cyanide in rabbit whole blood samples and the results agreed well with those obtained from official method.

An on-line galvanic cell-generated electrochemiluminescence and flow injection determination of calcium in milk and vegetables.

An on-line Ag/Al galvanic cell was studied and employed to generate electrochemiluminescence (ECL) of calcein blue. The potential of the galvanic cell could be adjusted by varying the components of flow reagent or by using different metals to substitute for Ag or Al. The reported cell exhibited perfect capability of supplying a stable potential for ECL generation. Because the weak ECL of calcein blue could be greatly sensitized in the presence of calcium in alkaline solution, calcium contents in milk and vegetable samples were assayed; the results were validated with ICP-AES method. The method gave linear results in 1.0 x 10(-4) mol L(-1) to 8.0 x 10(-6) mol L(-1) calcium concentration range and the 3(sigma)limit of detection was to be 2.0 x 10(-6) mol L(-1). Experiment results imply that this model of ECL detection could be applied for instrument miniaturization with easy fabrication.