Flow-injection chemiluminescence study of Ce(IV)-Na2SO3-Tb(III)-fluoquinolone antibiotic system with DNA

Deep-sea in situ determination of sulfide using a sensitized chemiluminescent terbium complex

A new chemiluminescence (CL) method based on the chemiluminescent reaction between sulfide and an acidic permanganate solution was used to quantify sulfide in seawater. A terbium-pipemidic acid complex was used as CL enhancer. The method was used to determine sulfide in the concentration range of 1-30 μmol/L in artificial seawater samples. The limit of detection of the method was 21 nmol/L sulfide. The sensitivity of the CL method was eight times higher than that of the CL method reported previously. Br^- ions, which are conservative ions, interfered with sulfide. We investigated the effects of salinity, water temperature, and interfering chemicals,such asheavy-metal ions and organic matter, on the performance of the CL method. In addition, sulfite-spiked natural seawater samples were analyzed. The results demonstrate that the CL method can be used to develop a deep-sea sulfide analyzer.

Simple and sensitive detection of deoxyribonucleic acid using a RecA-GFP fusion protein-DNA filament as probe

A simple, rapid and highly sensitive method for detection of double-stranded DNA (dsDNA) was developed using a novel fluorescence probe composed of a RecA-GFP fusion protein that had specific recognition of ssDNA complexes (RecA-GFP-DNA filament). The RecA-GFP fusion protein not only had strong fluorescence, but could also occur by homologous recombination. In the presence of the target dsDNA, the complementary ssDNA of the RecA-GFP-DNA filaments invaded one end of the dsDNA chain. In addition, the other end of the ssDNA dissociated the RecA-GFP filaments. An assay of the probe showed a linear relationship with dsDNA concentration in the range 1-11 nM, with a correlation coefficient of 0.9923. The limit of detection for dsDNA was determined experimentally to be 0.3 nM (3δ). Compared with conventional methods, this method has the advantages of simple operation, high specificity, and high sensitivity.

Activatable QD-Based Near-Infrared Fluorescence Probe for Sensitive Detection and Imaging of DNA

Accurate detection of DNA is essential for the precise diagnosis of diseases. Here we report an activatable near-infrared (NIR) fluorescence nanoprobe (QD-Al-GFLX) composed of NIR quantum dots (QDs) and Al(III)-gatifloxacin (Al-GFLX) complexes for the sensitive detection of double-stranded DNA (dsDNA) both in aqueous solution and in living cells. We demonstrated that the initial strong NIR fluorescence of QDs in QD-Al-GFLX was quenched by the Al-GFLX complex via a photoinduced electron transfer (PET) mechanism. Upon interaction with dsDNA, the high binding affinity between dsDNA and Al-GFLX complex could trigger QD-Al-GFLX dissociation, which could eliminate the PET process, resulting in significant enhancement of NIR fluorescence. QD-Al-GFLX was sensitive and specific to detect dsDNA in aqueous solution, with a detection limit of 6.83 ng/mL. The subsequent fluorescence imaging revealed that QD-Al-GFLX holds a high ability to enter into live cells, generating strong NIR fluorescence capable of reporting on dsDNA levels. This study highlighted the potential of using QD-Al-GFLX nanoprobe for the real-time detection and imaging of dsDNA in living cells.

Energy transfer processes of chemiluminescence reaction systems with cerium(IV) ions and their analytical application: a review

This review is devoted to a thorough discussion of chemiluminescence of the systems containing Ce(IV) ions as oxidising agents, with particular emphasis on the energy transfer processes in such systems. The influence of sensitisers such as: rhodamines, quinine, lanthanide ions and their complexes and quantum-dots has been analysed and the practical use of reaction systems for development of new chemiluminescence methods for determination of therapeutic drugs and substances of biological importance in different matrices such as human urine or serum is indicated. The types of emitters and excited reaction products taking part in energy transfer to sensitisers and processes taking place in the chemiluminescence reaction systems containing Ce(IV) ions are presented on the basis of recent literature.

Hollow-fiber liquid-phase microextraction for the direct determination of flumequine in urban wastewaters by flow-injection analysis with terbium-sensitized chemiluminescence

A flow-injection analysis chemiluminescence method based on the enhancement effect of the flumequine-Tb(III) complex on the weak native emission of the Ce(IV)-Na2SO3 system has been developed for the determination of flumequine. The method includes a cleanup and preconcentration stage (750-fold) of the sample by hollow-fiber liquid-phase microextraction using an Accurel(®) Q 3/2 polypropylene hollow fiber impregnated with 1-octanol as the supported liquid membrane. The obtained 50 μL acceptor phase was injected in a 1 mM Tb(III) + 4 mM Ce(IV) in 5% v/v H2 SO4 stream and mixed with a 2 mM Na2 SO3 stream before its introduction into the flow cell. The chemiluminescence signal was linear in the 0.3-15 ng/mL range, with detection and quantitation limits of 0.1 and 0.3 ng/mL, respectively. The method allows the selective extraction and determination of flumequine in wastewater samples, using simpler and lower-cost instrumentation and with shorter extraction and analysis times than traditional high-performance liquid chromatography analysis.

Detection of DNA using an “off-on” switch of a regenerating biosensor based on an electron transfer mechanism from glutathione-capped CdTe quantum dots to nile blue

A new DNA detection method, which relies on the “off-on” switch of a regenerated fluorescence biosensor based on an electron transfer mechanism from glutathione (GSH)-capped CdTe quantum dots (QDs) to nile blue (NB), is proposed.

The second-order scattering study of the Tb(III)-RNA and determination of RNA

The second-order scattering technique (SOS), using a common spectrofluorometer, was first developed as a sensitive instrumental analysis method for determination of the ribonucleic acid (RNA). The results indicate that RNA had a weak SOS peak and the Tb(III) ion can greatly enhance the SOS intensity of RNA with the maximum peak located at 612.0 nm. Mechanism study shows that the peak results from the long-range assembly of Tb(III) ion on the molecular surface of RNA. At the pH 7.50 and with cetyltrimethylammonium bromide (CTMAB) (6.0 x 10(-5)M), the enhanced SOS intensity was in proportion to the concentration of RNA in the range of 2.0 x 10(-8) to 2.0 x 10(-5)g/ml. The detection limit was 1.96 ng/ml. The relative standard deviation (five replicates) was within +/-5% in the linear range. This method has been used satisfactorily for the determination of both synthetic and real samples. In comparison with most other methods for the determination of ribonucleic acids, this method is more sensitive.