Yibing Zhao

Development of a novel rhodamine-type fluorescent probe to determine peroxynitrite

A novel method for the determination of peroxynitrite using rhodamine B hydrazide as a fluorogenic probe is described. The method is based on the oxidation of rhodamine B hydrazide, a colorless, non-fluorescent substance, by peroxynitrite to give rhodamine B-like fluorescence emission. The fluorescence increase is linearly related to the concentration of peroxynitrite in the range of 7.5x10(-8)-3.0x10(-6) mol l(-1) with a detection limit of 2.4x10(-8) mol l(-1) (3sigma). The optimal conditions for the detection of peroxynitrite were evaluated and the possible detection mechanism was also discussed in this paper.

Study on the interaction between rivanol and DNA and its application to DNA assay

Abstract Rivanol (RVN) binds to the double helical DNA with a high affinity, as deduced from the absorption and fluorescence spectral data. Extensive hypochromism and red shifts in the absorption spectra were observed when RVN binds to calf thymus DNA (CT DNA), which suggested the intercalation mechanism of RVN into DNA bases. Upon binding to DNA, the fluorescence from RVN was efficiently quenched by the DNA bases, with no shifts in the emission maximum. The large increases in the polarization upon binding to CT DNA supported the intercalation of RVN into the helix. Iodide quenching studies showed that the magnitude of Ksv of the free RVN was higher than that of the bound RVN. The results of competitive binding studies showed that RVN can be displaced by ethidium bromide. Thermal denaturation experiments exhibited that the quenching of the fluorescence from RVN by single strand (ssDNA) was smaller than that by double strand (dsDNA). The results of all above further studies also proved the intercalation of RVN into DNA base stack. Quenching of fluorescence from RVN by DNA can be employed for sensitive detection of DNA. The limit of detection for CT DNA was 16 ng ml−1.

Fluorescent core-shell silica nanoparticles as tunable precursors: towards encoding and multifunctional nano-probes

Core-shell silica nanoparticles comprised of a RuBpy doped silica core and a Pas-DTPA doped silica shell were synthesized and post-functionalized with an encoding fluorescence combination and multiplex imaging function.

Correlation between the Photoluminescence and Oriented Attachment Growth Mechanism of CdS Quantum Dots

Water-soluble mercaptoacetic acid-coated 3.1 nm CdS quantum dots (QDs) with two concentrations were selected for studying the correlation between the photoluminescence and the crystal growth mechanism. By achieving the classic Ostwald ripening mechanism and oriented attachment (OA) growth mechanism, we have shown that the evolution of the emission spectra were obviously different. The change in both the surface and internal defects during OA crystal growth were responsible for the specific variation of the photoluminescence of CdS QDs. Strategies for obtaining QDs with different luminescent properties are suggested.

LSPR Sensing of Molecular Biothiols Based on Noncoupled Gold Nanorods

Au NRs protected with mPEG-SH molecules (mPEG-Au NRs) were demonstrated to be a promising platform for LSPR-based sensing of molecular biothiols in aqueous solution. Surface mPEG-SH molecules endow Au NRs with great stability and biocompatibility and no nonspecific adsorption of biomacromolecules. The LSPR band of mPEG-Au NRs displays a stability and linear response in the spectral shift with respect to a change in their surrounding refractive index with a sensitivity of 252 nm/RIU. The loose structure of mPEG-SH around the Au NRs offers free sites, thereby allowing molecular biothiols to bind onto the surfaces of Au NRs. The LSPR response and the sensitivity of Au NRs to biothiols such as GSH, Cys, Hcy, TGA, GSSG, and BSA were then studied.

Application of vitamin K3 as a photochemical fluorescence probe in the determination of nucleic acids

ABSTRACT An in situ photochemical fluorescence probe method for the determination of nucleic acids with vitamin k3(VK3) as the photochemical fluorescence probe was developed for the first time. It was based on the conversion of VK3 into an intensively fluorescent product on irradiating with UV radiation. The photochemical reaction is decelerated by nucleic acids. The determination can be carried out by measuring the fluorescence intensity at a fixed time. The calibration graph was linear in the range of 0– 1.5 μg/ml for CT DNA and 0–2.0μg/ml for yeast RNA, the limit of detection was 10 ng/ml for CT DNA and 26 ng/ml for yeast RNA. The kinetic behaviour of the photochemical reaction and the effects of some experimental conditions were investigated and discussed in detail. CT DNA could be determined in the presence of 40%(w/w) yeast RNA and yeast RNA was determined when the content of CT DNA in synthetic samples was below 6%(w/w).

Determination of DNA and RNA by their quenching effect on the fluorescence of the Tb3+-Tiron complex

Abstract The fluorescence quenching of the Tb 3+ -Tiron complex by nucleic acids is reported. Studies involving calf thymus(CT) DNA, salmon(SM) DNA, herring sperm(HS) DNA and yeast RNA revealed that they compete with Tiron for the Tb 3+ ion, which resulted in the fluorescence quenching of the Tb 3+ -Tiron complex because the Tb 3+ -nucleic acid complex is non-fluorescent under the same conditions. The ratio of molar concentrations of Tb 3+ and Tiron appeared to be a key factor, a Tb 3+ : Tiron ratio of 3: 10 being the most suitable. The maximum fluorescence was produced at pH 6.9, with maximum excitation and emission wavelengths at 317 and 546 nm, respectively. Under optimal conditions, the differential value of fluorescence intensity in the absence and presence of nucleic acids was proportional to the concentration of nucleic acids over the range of 0.005–1.0 μg ml −1 for CT DNA, SM DNA, HS DNA, and 0.005–0.7 μg ml −1 yeast RNA. The detection limits were 1 ng ml −1 for CT DNA, 1 ng ml −1 for SM DNA, 0.9 ng ml −1 for HS DNA, and 0.6 ng ml −1 for yeast RNA, respectively. The relative standard deviations (6 replicates) were within 2.5% in the middle of the linear range. The mechanism for the fluorescence quenching was also studied.

Determination of DNA using sodium 9,10-anthraquinone-2-sulfonate as an in situ photochemical fluorescence probe

Abstract An in situ photochemical fluorescence probe method for the determination of DNA with sodium 9,10-anthraquinone-2-sulfonate (AQS) as a photochemical fluorescence probe was developed. It was based on the conversion of AQS into an intensively fluorescent product by irradiating with UV radiation. The photochemical reaction is retarded by DNA. The determination can be carried out by measuring the fluorescence intensity at a fixed time. The calibration graph was linear in the range 0–80 ng ml−1 calf thymus (CT) DNA (r = 0.9991), the limit of detection was 3.2 ng ml−1 CT DNA (n = 9). The kinetic behaviour of the photochemical reaction and the effects of experimental conditions were investigated and discussed in detail. The results of absorption spectra and competitive binding experiments suggested the interaction between AQS and DNA to be intercalative.

DNA-Dye Fluorescence Enhancement Based on Shifting the Dimer-Monomer Equilibrium of Fluorescent Dye

In this paper, the investigation of DNA–dye fluorescence enhancement based on shifting the dimer–monomer equilibrium of a fluorescent dye, acridine orange (AO), is reported. Formation of a virtually nonfluorescent dimeric dye, acridine orange homodimer (AOAO), induced by the pre-micellar aggregation of an anionic surfactant, sodium dodecyl sulfate (SDS), was observed. The possibility of using the in situ formed AOAO as a fluorescent probe for nucleic acids and polynucleotides was studied. The results showed that a nearly 1000-fold fluorescence enhancement was observed upon addition of calf thymus DNA (CT DNA). The fluorescence enhancement effect of DNA was thought to be based on the DNA modulated shift of the dimmer monomer equilibrium of AO in the anionic surfactant solution. Intercalation of the monomer in DNA caused the dissociation of AOAO and led to a very high fluorescence enhancement. It seemed that the dimeric dye molecules acted as a source of monomer molecules ready for interacting with nucleic acids and, at the same time, decreased the inherent fluorescence of monomer molecules, which proved to be unfavorable to the detection of fluorescence enhancement. A linear dependence of fluorescence intensity on CT DNA concentration over a range from 7.8 ng/mL to 10.0 g/mL, in the presence of AO at a concentration of 1.65 × 10−6mol/L and of SDS at a concentration of 8.0 × 10−4 mol/L, allowed sensitive quantitation of CT DNA in a conventional fluorometer. Calibration graphs for yeast RNA and polynucleotides, such as poly A, poly U, and poly I, were also obtained.

Determination of thiamine (vitamin B1) by in situ sensitized photochemical spectrofluorimetry

Abstract An in situ photochemical spectrofluorimetric flow-injection method for the determination of thiamine (vitamin B 1 ) is proposed. It is based on the conversion of thiamine in alkaline medium into an intensively fluorescent compound. The photochemical reaction is sensitized by acetone. The determination can be carried out by measuring the fluorescence intensity when the fluorescent signal reaches its maximum or at a fixed time. The calibration graph was linear up to 10.0 μg ml −1 thiamine ( r = 0.9996), the limit of detection was 0.46 ng ml −1 thiamine and the relative standard deviation was 1.5% for 50.0 ng ml −1 thiamine ( n = 6). The kinetic behaviour of the reaction and the effects of some experimental conditions were investigated and are discussed in detail. The mechanism of the sensitization of acetone was examined. Its application to vitamin B 1 tablets and injections was found to be satisfactory. By use of a selection valve and combination with a synchronous fluorescence technique, vitamin B 1 , B 2 and B 6 in pharmaceuticals were simultaneously determined.