Sensitive chemiluminescence aptasensor based on exonuclease-assisted recycling amplification

We report herein an exonuclease-assisted aptamer-based target recycling amplification strategy for sensitive and selective chemiluminescence (CL) determination of adenosine. This aptasensor is based on target-induced release of aptamers from capture probes immobilized on the 96-well plate surface, and thus leading to a decreased hybridization with gold nanoparticle-functionalized reporter sequences followed by a CL signal. The introduction of exonuclease III catalyzes the stepwise removal of mononucleotides from 3′-hydroxyl termini of duplex DNAs of aptamers, liberating the adenosine. Therefore, a single copy of target adenosine can lead to the release and digestion of numerous aptamer strands from the 96-well plates and ultimately an enhanced sensitivity is achieved. Experimental results revealed that the exonuclease-assisted recycling strategy enabled the monitoring of adenosine with wide working ranges and low detection limits (LOD: 0.5 nM). This new CL strategy might create a novel technology for the detection of various targets and could find wide applications in the environmental and biomedical fields.     

Automated high performance liquid chromatography with on-line reduction of disulfides and chemiluminescence detection for determination of thiols and disulfides in biological fluids

In general, the reduction of disulfide bonds with tris(2-carboxyethyl)phosphine (TCEP) is performed using off-line operation, which is not only time-consuming but also vulnerable to the spontaneous re-oxidation of thiols during sample preparation and subsequent analysis procedures. To the best of our knowledge, there has been not any case on the on-line reduction for biological disulfides coupled with high performance liquid chromatography (HPLC). In this study, these obstacles are overcome by packing Zn(II)-TCEP complexes into a home-made column. The as-synthesized Zn(II)-TCEP complexes enable efficient reduction of disulfide bonds at pH 3.0. This acidic pH value was compatible with that of the mobile phase for HPLC separation of thiols and disulfides. Therefore, using fluorosurfactant-prepared triangular gold nanoparticles as HPLC postcolumn specific chemiluminescence (CL) reagents for thiols, the feasibility of the established on-line reduction column has been confirmed for the direct identification of both thiols and disulfides by incorporating this reduction column into a single chromatographic separation. Detection limits for these analytes range from 8.3 to 25.4 nM and the linear range in a log–log plot can comprise three orders of magnitude. Finally, the utility of this automated on-line reduction of disulfides-HPLC-CL system has been demonstrated for the reliable determination of thiols and disulfides in human urine and plasma samples.     

Determination of Total Chromium in Biological Samples by Automated Reagent Injection Chemiluminescence Analysis

A sensitive method for the determination of total chromium in real samples by flow injection–chemiluminescence (FI–CL) analysis was proposed. It was found that the CL intensity from luminol–lysozyme reaction could be markedly quenched, and the decrease of CL intensity was linear with the logarithm of Cr(III) concentrations over the range of 5.0 to 4000 pg mL^?1 with a detection limit of 2.0 pg mL^?1 (3σ) and relative standard deviations (RSDs) of 3.0, 2.6, and 2.0% for 10, 100, and 1000 pg mL^?1 Cr(III) (n = 7), respectively. At a flow rate of 2.0 mL min^?1, the whole process including sampling and washing could be accomplished within 36 s. The proposed CL method was successfully applied to the determination of total chromium in pharmaceutical capsules, a dietary supplement, and spiked human serum samples, with recoveries from 92.2 to 108.4% and RSDs of less than 4.0%. Using the homemade FI–CL model, the binding constant (K = 4.38 × 10⁶ L mol^?1) and the binding sites (n ≈ 1) of Cr(III) to lysozyme were given.     

Determined GA by FI‐CE in Luminol‐H2O2 System

It was found that the chemiluminescence arising from the reaction of luminol with H₂O₂ involving Co(II)‐catalyzed in alkaline solution could be strongly inhibited by gibberellic acid. Based on this observation, a new flow injection chemiluminescence method is proposed for the determination of gibberellic acid. The detection limits of the method are 0.09 ng mL^?1 gibberellic acid. The method was successfully applied to the determination of gibberellic acid in bacteria‐free culture liquid.     

Thermal oxidative degradation of additive-free polypropylene pellets investigated by multichannel Fourier-transform chemiluminescence spectroscopy

Thermal oxidative degradation of additive-free polypropylene pellets heated isothermally in dry air at 150 and 180 °C (below and above the melting point of 163 °C) was investigated by multichannel Fourier-transform chemiluminescence spectroscopy. The initial peak wavelength of chemiluminescence emission at 490 nm remained constant during the early stages of thermal degradation, but new emissions developed with time in the red spectral region over an extended oxidation period. The time-dependent luminescence spectra were deconvoluted into three emission bands by least-squares fitting using Gaussian curves. We concluded that at least three groups of luminescent species (luminophores), having different conjugation lengths, were generated by thermal oxidation over extended periods and show luminescence around 490, 660, and 740 nm.     

Determination of carbaryl by flow injection with luminol chemiluminescence inhibition detection

A flow-injection procedure is described for the determination of carbaryl based on its inhibition effect on luminol-cobalt(II) chemiluminescence reaction in alkaline medium in the presence of hydrogen peroxide. The calibration data over the range 5.0?×?10^?7 to 20?×?10^?6?M give a correlation coefficient (r ²) of 0.9972 with relative standard deviations (RSD; n?=?4) in the range of 1.0–2.1% with a limit of detection (3?×?blank noise) of 2.37?×?10^?7?M for carbaryl. The sample throughput was 120?h^?1. The effects of some carbamates, anions, and cations were studied on luminol CL system for carbaryl determination. The proposed method has been applied to determine carbaryl in natural waters.     

A stable chemiluminophore,adamantylideneadamantane 1,2-dioxetane: from fundamental properties to utilities in mechanochemistry and soft crystal science

Chemiluminescence (CL) is a luminescence phenomenon originated by a “chemical reaction.” CL provides a basis for real-time imaging technology in materials science. In fact, a CL reaction is easily triggered in general and makes it possible to track its progress in a target material by highly sensitive photon detection. Recently, real-time CL imagings became breakthrough techniques for analyzing the molecular mechanisms of failures of polymeric materials and of reactions and phase transitions in soft crystals. In the CL imaging techniques, adamantylideneadamantane 1,2-dioxetane (Adox) has been adopted as a stable core structure of chemiluminophores. That is, Adox is an essential seed compound to design a chemiluminophore with a desired molecular function. To support developments of real-time CL imaging techniques, we review the chemistry of Adox as a representative stable chemiluminophore including scientific history and utilities of Adox and its derivatives.     

Native vs photoinduced chemiluminescence in dimethoate determination

The determination of dimethoate using either its native chemiluminescent (CL) properties or its photoinduced chemiluminescence obtained by irradiation with a 15 W low-pressure mercury lamp was studied. Thereby, two flow injection systems (FIA) with and without irradiation were exhaustively optimized and their analytical characteristics studied. Better sensitivity and selectivity was found in absence of irradiation, due to the enhancing effect of hexadecylpyridinium chloride (HPC), which acted as a sensitizer. In the developed FIA-CL system, the alkaline hydrolysis of dimethoate with NaOH was performed on-line in presence of HPC. The oxidation of the product of hydrolysis with Ce(IV) in hydrochloric medium induced chemiluminescence. The method provided a limit of detection of only 0.05 ng mL⁻¹ without any pre-treatment. However, the combination with solid phase extraction allowed the removal of some potential interferents as well as the preconcentration of the pesticide. Finally, the developed method was successfully applied to natural waters with recoveries between 95 and 108%.     

Nylon and nylon blend nanotubes and nanorods

Nylon nanorods and nanotubes (200 nm diameter) were fabricated by the membrane wetting technique (solvent and melt wetting) from a range of nylons (6; 6,6; 6,9; 6,10; 6,12; 11; 12, 6(3)T) and nylon blended with different dyes (Nylon Cast Blue, Nylon 6/6 Black) or with molybdenum disulfide (Nylon cast MDS). The 65-μm long nylon nanotubes and nanorods were characterized by scanning electron microscopy. The nanoscale nylon 6,6 served as an effective high surface area alternative to a nylon membrane as a solid support in a chemiluminescent assay for nylon-bound biotinylated nucleic acids based on streptavidin- alkaline phosphatase and chemiluminescent detection of the bound alkaline phosphatase label with the dioxetane substrate, CDP-Star. Layer-by-layer deposition of the cationic polymer (Sapphire-II™; Tropix) onto the nylon 6,6 nanostructures prior to UV-cross-linking with biotinylated DNA resulted in further enhancement of binding and detection of biotinylated DNA.     

Chemiluminescence determination of antibacterial drug trimethoprim by automated sequential injection technique with permanganate and hexametaphosphate as reagents

Antibacterial drug trimethoprim [2,4-diamino-5-(3,4,5-trimethoxybenzyl)-pyrimidine] (I) was determined in pharmaceutical formulations by using a lab-made PC-controlled SIA analyser linked to conventional HPLC fluorimetric detector equipped with a chemiluminescence module. The chemical principle is the oxidation of I by KMnO(4) in acid medium; the reaction is accompanied by the emission of chemiluminescence, which is enhanced in the presence of hexametaphosphate (HMP). The optimum sequence and the flow parameters and concentrations and volumes of reagents aspirated optimised by a computer-aided simplex method were, 100 mul of 5 mM HMP, 40 mul of a test solution of I, 2 mul of 0.5 M H(2)SO(4) and 20 mul of 1 mM KMnO(4); the luminescing zone was pushed into the detector at a flow rate of 49 mul s(-1). The calibration graph relating the intensity of luminescence to concentration of I was parabolic (r=0.9994) in the range 0.5-100 mug ml(-1) of I with rectilinear part (r=0.9999) in the range 20-100 mug ml(-1) of I; the limit of detection was 0.1 mug ml(-1) of I. The method was used for the assay of Triprim(R) tablets (with nominal content 100 or 200 mg of I) for the active substance as well as for content uniformity tests; the R.S.D. values did not exceed 1% (n=5). The SIA results did not show statistical difference from those obtained by pharmacopoeial acidimetric titration in non-aqueous medium; the excipients such as microcrystalline cellulose, maze starch, povidone, talc, magnesium stearate and gelatin did not interfere.