Study of the interaction of Azur B with DNA and the determination of DNA based on resonance light scattering measurements

Based on the measurements of molecular absorption and resonance light scattering (RLS), the aggregation of Azur B (AB) was in a medium of pH ranging from 1.98 to 2.56 and ionic strength <0.12 M. The presence of double stranded DNA prompts the aggregation, resulting in enhanced RLS signals. Linear relationships were achieved between the enhanced RLS intensity at 359.7 nm and DNA concentration in the range of 0-4.5 μg ml⁻¹ for both calf thymus DNA (ctDNA) and fish sperm DNA (fsDNA) if 3.0×10⁻⁵ M AB was employed. The 3σ limits of detection were 9.3 and 8.9 ng ml⁻¹ for ctDNA and fsDNA, respectively. Five synthetic samples were analysed satisfactorily.     

Nucleic acids analysis with nano-Ag-Tb(III) by a resonance light scattering technique.

The nano-Ag-terbium(III)-mucleic acids system was observed by a resonance light scattering (RLS) technique for the first time, and the quantitative analysis of nucleic acids at nanogram levels was established. Studies showed that the RLS intensity of the nano-Ag-terbium(III) system can be obviously enhanced by nucleic acid, which was characterized by the RLS spectrum and the UV-Vis spectrum. In this system, the nanoparticles were only of a definite size and in a limited particle concentration region. Further research indicated that under the optimum conditions, the enhanced intensity of RLS is in proportion to the concentration of nucleic acids in the ranges of 7.0 x 10(-9) g ml(-1) to 8.0 x 10(-6) g ml(-1) for calf thymus DNA (ctDNA), 2.0 x 10(-8) g ml(-1) to 1.0 x 10(-6) g ml(-1) for fish sperm DNA (fsDNA) and 1.0 x 10(-9) g ml(-1) to 1.0 x 10(-7) g ml(-1) for yeast RNA (yRNA). The detection limits were 1.4 ng ml(-1) for ctDNA, 1.2 ng ml(-1) for fsDNA and 0.85 ng ml(-1) for yRNA, respectively. Synthetic and real samples were determined satisfactorily.     

Enoxacin-Tb complex as an environmentally friendly fluorescence probe for DNA and its application

The fluorescence intensity of the enoxacin (ENX)-Tb³⁺ complex enhanced by DNA was studied. On the basis of this study, an environmentally friendly fluorescence probe of enoxacin-Tb³⁺ for the determination of single-stranded and double-stranded DNA was developed. Under the optimal conditions, the enhanced fluorescence intensity was in proportion to the concentration of DNA in the range of 2.0 × 10⁻⁸ to 2.0 × 10⁻⁶ g mL⁻¹ for hsDNA, 1.0 × 10⁻⁸ to 1.0 × 10⁻⁶ g mL⁻¹ for ctDNA and 5.0 × 10⁻⁹ to 1.0 × 10⁻⁶ g mL⁻¹ for thermally denatured ctDNA. The detection limits (S/N = 3) were 5.0, 9.0 and 3.0 ng mL⁻¹, respectively. The interaction modes between ENX-Tb³⁺ and DNA and the mechanism of the fluorescence enhancement were also discussed in details. The experimental results from UV absorption spectra, fluorescence spectra and the competing combination tests between the ENX-Tb³⁺ complex and EB probe indicated that the possible interaction modes between enoxacin-Tb³⁺ complex and DNA had at least two different binding modes: the electrostatic binding and the intercalation binding. Additionally, this fluorescence probe was used to study the interaction between heavy metals and DNA.     

Study on the interaction between silver nanoparticles and nucleic acids in the presence of cetyltrimethylammonium bromide and its analytical application

A novel method is proposed in this paper, that is the silver nanoparticle (nanoAg)-cetyltrimethylammonium bromide (CTMAB) is used as the probe of resonance light scattering (RLS) for the determination of nucleic acids. Under optimum conditions, there are linear relationships between the quenching extent of RLS and the concentration of nucleic acids in the range of 4.0x10(-9)-2.0x10(-6)gmL(-1) for fish sperm DNA (fsDNA), 7.0x10(-9)-1.8x10(-6)gmL(-1) for calf thymus DNA (ctDNA) and 6.0x10(-9)-1.0x10(-6)gmL(-1) for yeast RNA (yRNA). The detection limits (S/N=3) of fsDNA, ctDNA and yRNA are 2.7x10(-10)gmL(-1), 4.8x10(-10)gmL(-1) and 7.2x10(-10)gmL(-1), respectively. The studies indicate that there are interactions among nanoAg, CTMAB and fsDNA through electrostatic and chemical affinity, and the nanoAg-CTMAB complex can induce the structural change of base stacking and helicity of fsDNA.     

Micro-determination of nucleic acids with a simple probe manganese chloride based on the fine enhanced resonance light scattering

Manganese chloride can form large particles with nucleic acids by electrostatic forces, which results in strong enhancement of resonance light scattering (RLS) signals. Based on this phenomenon, a novel and very simple assay of DNA was established. The work conditions have been investigated including the concentration of probe, the acidity of solution, the effect of ionic strength and the selectivity. In acidic solution, the enhanced RLS intensity at 389.5 nm was proportional to the concentration of nucleic acids in the range 0.05-10.0 microg ml(-1) for both ctDNA and fsDNA and 1.0-10.0 microg ml(-1) for yRNA. The limits of detection (LOD, 3sigma) were 0.17, 0.13 and 0.53 ng ml(-1) for ctDNA, fsDNA and yRNA, respectively. Synthetic samples were determined satisfactorily.     

The sensitive determination of nucleic acids using resonance light scattering quenching method

It is found that in hexamethylene tetramine (HMTA)-HCl buffer of pH 7.00, nucleic acids can quench the resonance light scattering (RLS) of europium (III) (Eu3+)-2-thenoyltrifluoroacetne (TTA)-1,10-phenanthroline (Phen) system. Based on this, a sensitive method for the determination of nucleic acids is proposed. The experiments indicate that under the optimum conditions, the quenched RLS intensity is in proportion to the concentration of nucleic acids in the range of 1.0x10(-10) to 2.0x10(-6) g ml-1 for fish sperm (fsDNA), 1.0x10(-11) to 1.0x10(-6) g ml-1 for yeast RNA (yRNA), 5.0x10(-11) to 5.0x10(-7) g ml-1 for calf thymus DNA (ctDNA). Their detection limits (S/N=3) are 0.03, 0.006 and 0.002 ng ml-1, respectively. Therefore, the proposed method is the most sensitive RLS method for the determination of nucleic acids so far. The interaction between nucleic acids and Eu3+-TTA-Phen is also discussed.     

Interactions of Night Blue with Nucleic Acids and Determination of Nucleic Acids Using Resonance Light Scattering Technique

The noncovalent interactions of night blue (NB) with several nucleic acids in buffer medium of Britton‐Robinson at pH 4.1 have been studied by spectroscopic methods. It is shown that the binding of NB with nucleic acids involves the J‐aggregation of NB molecules on the surface of nucleic acids. The aggregation was encouraged by polyanions nucleic acids, in which nucleic acids served for acting templates. In this connection, a new method of nucleic acids with sensitivity at nanogram level is proposed based on the measurement of enhanced resonance light scattering (RLS). The linear range of ctDNA, fsDNA and yRNA is 0.01—2.5, 0.03—2.5 and 0.04—1.0 μg/mL, respectively, and the corresponding detection limits (3s?) are 9.4, 7.3 and 5.7 ng/mL at 2.5 × 10–⁵mol/L of NB. Synthetic and real samples were analyzed with satisfactory results.     

Determination of indole-3-acetic acid and indole-3-butyric acid in mung bean sprouts using high performance liquid chromatography with immobilized Ru(bpy)3-KMnO4 chemiluminescence detection

A novel method for determination of indole-3-acetic acid (IAA) and indole-3-butyric acid (IBA) in an extract from mung bean sprouts using high performance liquid chromatography (HPLC) with chemiluminescence (CL) detection is described. The method is based on the CL reaction of auxin (indole-3-acetic acid and indole-3-butyric acid) with acidic potassium permanganate (KMnO₄) and tris(2,2′-bipyridyl)ruthenium(II), which was immobilized on the cationic ion-exchange resin. The chromatographic separation was performed on a Nucleosil RP-C18 column (i.d.: 250 mm × 4.6 mm, particle size: 5 μm, pore size: 100) with an isocratic mobile phase consisting of methanol-water-acetic acid (45:55:1, v/v/v). At a flow rate of 1.0 mL min⁻¹, the total run time was 20 min. Under the optimal conditions, the linear ranges were 5.0 × 10⁻⁸ to 5.0 × 10⁻⁶ g mL⁻¹ and 5.0 × 10⁻⁷ to 1.0 × 10⁻⁵ g mL⁻¹ for IAA and IBA, respectively. The detection limits were 2.0 × 10⁻⁸ g mL⁻¹ and 2.0 × 10⁻⁷ g mL⁻¹ for IAA and IBA, respectively. The relative standard deviation (RSD) of intra-day were 3.1% and 2.3% (n = 11) for 2 × 10⁻⁶ g mL⁻¹ IAA and 2 × 10⁻⁶ g mL⁻¹ IBA; The relative standard deviations of inter-day precision were 6.9% and 4.9% for 2 × 10⁻⁶ g mL⁻¹ IAA and 2 × 10⁻⁶ g mL⁻¹ IBA. The proposed method had been successfully applied to the determination of auxin in mung bean sprouts.     

Study on the interaction between oxolinic acid aggregates and protein and its analytical application

It was found that oxolinic acid (OA) at high concentration can self-assemble into nano- to micro- meter scale OA aggregates in Tris-HCl (pH 7.48) buffer solution. The nanoparticles of OA were adopted as fluorescence probes in the quantitative analysis of proteins. Under optimum conditions, the fluorescence quenching extent of nanometer scale OA aggregates was in proportion to the concentration of albumins in the range of 3.0 × 10⁻⁸ to 3.0 × 10⁻⁵ g mL⁻¹ for bovine serum albumin (BSA) and 8.0 × 10⁻⁸ to 8.0 × 10⁻⁶ g mL⁻¹ for human serum albumin (HSA). The detection limits (S/N = 3) were 3.4 × 10⁻⁹ g mL⁻¹ for BSA, and 2.6 × 10⁻⁸ g mL⁻¹ for HSA, respectively. Samples were satisfactorily determined. The interaction mechanism of the system was studied using fluorescence, UV-vis, resonance light scattering (RLS) and transmission electron microscope (TEM) technology, etc., indicating that the nonluminescent complex was formed between serum albumin molecular and OA, to disaggregate the self-association of OA, which resulted in the dominated static fluorescence quenching in the system.     

Fluorimetric determination of nucleic acids with terbium and lutetium

In this paper, fluorescence-enhancement of Tb-nucleic acids [fish sperm DNA (fsDNA) and yeast RNA (yRNA)] by Lu³⁺ is studied in detail and is applied to determine nucleic acids. The experiments indicated that under the optimum conditions, a linear relationship was obtained between the fluorescence intensity (I_f) and the concentration of nucleic acids. The linear range is 1.2×10⁻⁸-1.0×10⁻⁴ g/ml for DNA and 3.0×10⁻⁸-8.0×10⁻⁴ g/ml for RNA. The detection limits (signal/noise=3) for DNA and RNA were 4.8×10⁻⁹ and 7.0×10⁻⁹ g/ml, respectively. The mechanism of the co-luminescence effect is also discussed.     

An ultrasensitive post chemiluminescence reaction of ammonium in NBS-dichlorofluorescein system and its application

A strong post chemiluminescence (PCL) phenomenon was observed when ammonium was injected into the reaction mixture after the finish of CL reaction of N-bromosuccinimide (NBS) and dichlorofluorescein. Based on this, a sensitive flow injection PCL method was established for the determination of ammonium. The possible CL mechanism of the reaction was proposed based on a series of experiments. The PCL intensity responded linearly to the concentration of ammonium in the range 3.0 × 10⁻¹¹-1.0 × 10⁻⁷ g mL⁻¹ with a detection limit of 1 × 10⁻¹¹ g mL⁻¹. The relative standard deviation (R.S.D.) was 1.4% for 1.0 × 10⁻⁹ g mL⁻¹ ammonium (n = 11). This method had been applied to the determination of ammonium in samples of mineral water, tap water and river water.     

Backscattering light detection of nucleic acids with tetraphenylporphyrin-Al(III)-nucleic acids at liquid/liquid interface

A backscattering light (BSL) detection assembly is constructed and applied to the determination of nucleic acids with high sensitivity and selectivity based on the measurements of BSL signals at water/tetrachloromethane (H₂O/CCl₄) interface. In aqueous medium of pH 3, the binary complex of of Al(III)-DNAs could be formed by the interaction of Al(III) with the phosphate group of DNAs, which then could interact with tetraphenylporphyrin (TPP) in tetrachloromethane through liquid/liquid interaction, forming a ternary complex of TPP-Al(III)-DNAs at the interface. It was observed that greatly enhanced BSL signals occurred with maximum peak at 469 nm when the ternary complex of TPP-Al(III)-DNAs were absorbed to the liquid/liquid interface. The enhanced backscattering light intensity (I_BSL) is in proportion to the concentration of calf thymus DNA (ctDNA) and fish sperm DNA (fsDNA) in the range of 0.6-1200 ng ml⁻¹ and 1.1-1200 ng ml⁻¹, respectively. The limits of determination (3σ) are 60 pg ml⁻¹ and 110 pg ml⁻¹, correspondingly. Artificial samples with highly interference backgrounds were determined with the recovery ranging from 94.5 to 106.7%, and relative standard deviation (R.S.D.) less than 2.40%.     

Biomimetic enhanced chemiluminescence of luminol-H2O2 system by manganese (III) deuteroporphyrin and its application in flow injection determination of phenol at trace level

A novel, sensitive and high selective flow-injection chemiluminescence (FI-CL) method for the determination of phenol is reported, based upon its decreasing effect on the CL reaction of luminol with hydrogen peroxide catalyzed by manganese (III) deuteroporphyrin [MnDP, Scheme 1, 3] in alkaline solution. Under the selected optimized experimental conditions, the relative CL intensity was linear with phenol in the range of 4.0 × 10⁻⁹ to 4.0 × 10⁻⁷ g mL⁻¹. The detection limit (3σ) was 6.3 × 10⁻¹⁰ g mL⁻¹ and the relative standard deviation for 1.0 × 10⁻⁷ g mL⁻¹ phenol (n = 11) was 2.99%. The regression equation was I = 120.79 + 1.14 × 1010c (R = 0.9936). This method has been applied to the determination of phenol in water with satisfactory results.     

Determination of itopride hydrochloride by high-performance liquid chromatography with Ru(bpy)3 electrogenerated chemiluminescence detection

In this work, a stable electrogenerated chemiluminescence (ECL) detector was developed. The detector was prepared by packing cation-exchanged resin particles in a glass tube, followed by inserting Pt wires (working electrode) in this tube and sealing. The leakage of Ru(bpy)₃²⁺ can be compensated by adding a small amount of Ru(bpy)₃²⁺ into solution phase. Coupled with high-performance liquid chromatography separation, the detector has been used for determination of itopride hydrochloride in human serum. Under the optimal conditions, the ECL intensity has a linear relationship with the concentration of itopride hydrochloride in the range of 1.0 × 10⁻⁸ g mL⁻¹ to 1.0 × 10⁻⁶ g mL⁻¹ and the detection limit was 3 × 10⁻⁹ g mL⁻¹ (S/N = 3). The as-prepared ECL detector displayed good sensitivity and stability.     

Flow injection chemiluminescence determination of nitrofurazone in pharmaceutical preparations and biological fluids based on oxidation by singlet oxygen generated in N-bromosuccinimide-hydrogen peroxide reaction

A simple flow injection chemiluminescence (FI-CL) method was proposed for the determination of nitrofurazone. Strong CL signal was generated during the reaction of nitrofurazone with H₂O₂ and N-bromosuccinimide (NBS) in alkaline condition. The CL signal was proportional to the nitrofurazone concentration in the range 1.0 × 10⁻⁷ to 1.0 × 10⁻⁵ g mL⁻¹. The detection limit was 2 × 10⁻⁸ g mL⁻¹ nitrofurazone and the relative standard deviation was less than 4% (6.0 × 10⁻⁶ g mL⁻¹ nitrofurazone, n = 11). The proposed method was successfully applied to the determination of nitrofurazone in compound furacillin nasal drops, human plasma and urine samples. The CL reaction mechanism was also discussed briefly. Singlet oxygen generated in the reaction between H₂O₂ and NBS was suggested to be participated in the CL reaction.     

Flow injection chemiluminescence determination of naproxen based on KMnO4-Na2SO3 reaction in neutral aqueous medium

A simple, rapid and sensitive flow injection chemiluminescence (CL) method is described for the determination of naproxen. It was found that strong CL signal was generated when naproxen was mixed with KMnO₄ and Na₂SO₃ in neutral aqueous medium. Under the optimum experimental conditions, the CL intensity was linearly related to the concentration of naproxen from 4.0 × 10⁻⁹ to 1.0 × 10⁻⁶ g mL⁻¹ (r = 0.9993). The detection limit was 2 × 10⁻⁹ g mL⁻¹ naproxen, the relative standard deviation for 1.0 × 10⁻⁷ g mL⁻¹ naproxen solution was 1.5% (n = 11) and the sampling frequency was 120 h⁻¹. The method was applied to the determination of naproxen in pharmaceutical preparation with satisfactory results. The mechanism of CL reaction was discussed briefly.     

Silver nanoparticles fluorescence enhancement effect for determination of nucleic acids with kaempferol-Al(III)

Nucleic acids can greatly enhance fluorescence intensity of the kaempferol (Km)-Al(III) system in the presence of silver nanoparticles (AgNPs). Based on this, a novel method for the determination of nucleic acids is proposed. Under studied conditions, there are linear relationships between the extent of fluorescence enhancement and the concentration of nucleic acids in the range of 5.0 × 10⁻⁹ to 2.0 × 10⁻⁶ g mL⁻¹ for fish sperm DNA (fsDNA), 7.0 × 10⁻⁹ to 2.0 × 10⁻⁶ g mL⁻¹ for salmon sperm DNA (smDNA) and 2.0 × 10⁻⁸ to 3.0 × 10⁻⁶ g mL⁻¹ for yeast RNA (yRNA), and their detection limits are 2.5 × 10⁻⁹ g mL⁻¹, 3.2 × 10⁻⁹ g mL⁻¹ and 7.3 × 10⁻⁹ g mL⁻¹, respectively. Samples were satisfactorily determined. And the system of Km-Al(III)-AgNPs was used as a fluorescence staining reagent for sensitive DNA detection by DNA pattern of agarose gel electrophoresis analysis. The results indicate that the fluorescence enhancement should be attributed to the formation of Km-Al(III)-AgNPs-nucleic acids aggregations through electrostatic attraction and adsorption bridging action of Al(III) and the surface-enhanced fluorescence effect of AgNPs.     

Investigation on enhanced chemiluminescence reaction systems with bis(hydrogenperiodato) argentate(III) complex anion for fluoroquinolones synthetic antibiotics

A novel chemiluminescence (CL) reaction system with bis(hydrogenperiodato) argentate(III) complex anion (Ag(III) complex, [Ag(HIO₆)₂]⁵⁻), for the first time, is developed for the determination of lomefloxacin (LMFX), enrofloxacin (ENLX) and pefloxacin (PFLX). The possible CL emission mechanism was discussed by comparing the fluorescence emission with CL spectra. The CL conditions of [Ag(HIO₆)₂]⁵⁻-H₂SO₄-LMFX/ENLX/PFLX systems were investigated and optimized. Under the optimized experimental conditions, the CL intensity is proportional to the concentration of the drugs in the range 0.2994-36.80 × 10⁻⁷ g mL⁻¹ for LMFX, 4.00-30.0 × 10⁻⁷ g mL⁻¹ for ENLX and 1.54-27.64 × 10⁻⁷ g mL⁻¹ for PFLX. The limit of detection (s/n = 3) was 9.1 × 10⁻⁹ g mL⁻¹ for LMFX, 3.1 × 10⁻⁹ g mL⁻¹ for ENLX and 4.4 × 10⁻⁹ g mL⁻¹ for PFLX. The recovery of LMFX, ENLX and PELX from the spiked pharmaceutical preparations was in the range of 92.3-105% with the RSDs of 0.5-2.7%. For urine, serum and milk samples the recoveries of the three drugs were in the range of 85.1-107% for LMFX with the RSDs of 2.3-3.4%. 80.2-112% for ENLX with the RSDs of 1.4-2.8%, and 87.8-114% for PFLX with the RSDs of 1.6-2.7%. The proposed method was applied successfully to the determination of these compounds in real samples.     

A dual-wavelength resonance light scattering ratiometry of biopolymer by its electrostatic interaction with surfactant

A dual-wavelength resonance lighting scattering (DW-RLS) ratiometry is developed to detect anion biopolymer based on their bindings with cation surfactant. Using the interaction of Hyamine 1622 (HM) with fish sperm DNA (fsDNA) as an example, a dual-wavelength resonance light scattering (DW-RLS) ratiometric method of DNA was constructed. In Britton-Robinson buffer controlled medium, fish sperm DNA (fsDNA) could interact with Hyamine 1622 (HM), displaying significantly enhanced RLS signals. By measuring the RLS signals characterized at 300.0 nm (I_300.0) and the RLS intensity ratio (I_276.0/I_294.0), respectively, fsDNA over a wide dynamic range of content could be detected. Typically, when HM concentration is kept at 6.0 × 10⁻⁵ mol l⁻¹, using I_300.0 could detect fsDNA over the range of 50-2000 ng ml⁻¹ with the limit of 3.0 ng ml⁻¹, while using I_276.0/I_294.0 could detect fsDNA over the range of 0.5-2500 ng ml⁻¹ with the limit of 0.05 ng ml⁻¹. Thus the latter so-called DW-RLS ratiometry is obviously superior to the former one. Based on the measurements of I_300.0 and I_276.0/I_294.0 data, a Scatchard plot concerning the interaction between HM and fsDNA could be constructed and thus the binding number (n) and binding constant (K) could be available with the values of 13.5 and 1.35 × 10⁵ mol⁻¹ l, and 11.9 and 1.65 × 10⁵ mol⁻¹ l, respectively.     

Determination of ketotifen by using calcein as chemiluminescence reagent

Chemiluminescence (CL) was observed when potassium hexacyanoferrate(III) reacted with the mixture of calcein and ketotifen. Interestingly, the CL intensity would be enhanced by trace amounts of Mg²⁺ and the CL intensity was strongly dependent on ketotifen concentration. Based on this phenomenon, a flow injection CL method was established for the determination of ketotifen. The possible CL mechanism is proposed based on the kinetic characteristic of the CL reaction, CL spectrum, ultraviolet (UV) spectra and fluorescent spectra. The CL intensity was correlated linearly with concentration of ketotifen over the range of 6.0 × 10⁻⁹ to 2.0 × 10⁻⁷ g mL⁻¹ and the detection limit was 3 × 10⁻⁹ g mL⁻¹. The relative standard deviation was 1.8% for 2.0 × 10⁻⁸ g mL⁻¹ ketotifen (n = 11). This method was applied to the determination of ketotifen in the tablets successfully.