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.     

Determination of phenol by flow-injection with chemiluminescence detection based on the hemin-catalysed luminol-hydrogen peroxide reaction

This study established a novel flow injection (FI) methodology for the determination of phenol in aqueous samples based on luminol chemiluminescence (CL) detection. The method was based on the inhibition that phenol caused on the hemin-catalysed chemiluminescence reaction between luminol and hydrogen peroxide in alkaline solution. Optimum conditions and possible mechanisms have been investigated. The linear range was 2.0×10(-9) to 4.0×10(-7)gmL(-1) for phenol. The proposed method is sensitive with a detection limit of 4.0×10(-10)gmL(-1). The relative standard deviation for 11 measurements was 2.3% for 1.0×10(-7)gmL(-1) phenol. The method was applied for the determination of phenol in waste water samples. The results obtained compared well with those by an official method.     

能量转移荧光猝灭法测定加替沙星

在λ_(ex)/λ_(em)=470/566 nm、BR缓冲溶液(pH=5.72)、十二烷基苯磺酸钠介质中,吖啶橙(AO)与罗丹明6G(R6G)间能发生有效的能量转移,使R6G的荧光强度显著增强;加替沙星的加入,使R6G的荧光发生猝灭.应用AO-R6G能量转移荧光猝灭法测定加替沙星含量,提高了测定的灵敏度和选择性.加替沙星的浓度在0.6～9.0 μmol·L~(-1)范围内与R6G荧光猝灭程度呈线性关系;方法检出限为0.52 μmol·L~(-1);平行6次测定样品相对标准偏差为0.62%～0.84%;回收率为90.0%～105%.常见金属离子及药物敷料对测定无干扰,不经分离直接用于药物中加替沙星的测定.     

High selective determination iron(II) by its enhancement effect on the fluorescence of pyrene-tetramethylpiperidinyl (TEMPO) as a spin fluorescence probe

A novel fluorescence method determination for iron(II) with a high selectivity and sensitivity has been proposed, based on the enhancement of fluorescence signals resulting from specific redox reaction between synthesized spin fluorescence probe pyrene-tetramethylpiperidinyl (TEMPO) and iron(II). Under the experimental conditions, fluorescent probe displayed a rapid and linear response for iron(II) over the concentration range from 2.4 x 10(-7) to 3.6 x 10(-6) mol/L. The limit of detection was 4.0 x 10(-8) mol/L. The relative standard deviation of six replicate measurements was 1.90% for 3.0 x 10(-7) mol/L iron(II). Because of the specific redox reaction between developed spin fluorescence probe and iron(II), there are few interference by other ions, especially in the presence of relative high concentration iron(III). The method has been successfully applied for iron(II) determinations in two different kinds of real samples. Results determined by the proposed method agree favorably with those determined UV-vis spectrometry method with 1,10-phenanthroline.     

A fluorescent probe for zinc ions based on N-methyltetraphenylporphine with high selectivity

N-methyl-alpha,beta,gamma,delta-tetraphenylporphine (NMTPPH) has been used to detect trace amount of zinc ions in ethanol-water solution by fluorescence spectroscopy. The fluorescent probe undergoes a fluorescent emission intensity enhancement upon binding to zinc ions in EtOH/H(2)O (1:1, v/v) solution. The fluorescence enhancement of NMTPPH is attributed to the 1:1 complex formation between NMTPPH and Zn(II) which has been utilized as the basis for the selective detection of Zn(II). The linear response range covers a concentration range of Zn(II) from 5.0x10(-7) to 1.0x10(-5)mol/L and the detection limit is 1.5x10(-7)mol/L. The fluorescent probe exhibits high selectivity over other common metal ions except for Cu(II).     

FRET-based aptamer probe for rapid angiogenin detection

A sensitive method for rapid angiogenin (Ang) detection based on fluorescence resonance energy transfer (FRET) has been described. A dual-labeled probe based on high affinity aptamer for Ang was constructed. As donor and acceptor, 6-carboxyfluorescein (FAM) and 6-carboxy-tetramethylrhodamine (TMR) were labeled at 5'- and 3'-termini of the aptamer probe, respectively. The dual-labeled probe showed obvious fluorescence changes due to the specific binding between aptamer and Ang. By monitoring the fluorescence intensity of donor and acceptor, quantitative Ang detection could be achieved. This assay is highly specific and sensitive, with a detection limit of 2.0 x 10(-10) mol L(-1) and a linear range of 5.0 x 10(-10) to 4.0 x 10(-8) mol L(-1) Ang. Ang in serum samples of health and lung cancer were also detected.     

亲和毛细管电泳法测定牛血清白蛋白和加替沙星的结合常数

利用亲和毛细管电泳法对牛血清白蛋白(BSA)与加替沙星(GT)间的结合反应及其相互作用做了初步探索,并应用淌度比(M)作为指标测定了两者的结合常数。以20 mmol/L pH 7.4的磷酸盐缓冲液作为运行缓冲液,分别以GT和BSA作为添加剂,另一组分为进样样品,内标为二甲基甲酰胺,于214 nm波长下检测。两种测定条件下得到的结合常数分别为4.4×104 L/mol和4.2×104 L/mol,与传统的荧光淬灭法测得的结果基本一致。该方法具有简单、高效的优点。     

Highly sensitive spectrofluorimetric determination of trace amounts NADP using Europium ion-doxycycline complex probe

A new spectrofluorimetric method was developed for determination of trace amount of Coenzyme II (NADP). Using europium ion-doxycycline (DC) as a fluorescent probe, in the buffer solution of pH 8.44, NADP can remarkably enhance the fluorescence intensity of the Eu(3+)-DC complex at lambda=612 nm and the enhanced fluorescence intensity is in proportion to the concentration of NADP. Optimum conditions for the determination of NADP were also investigated. The dynamic range for the determination of NADP is 3.3 x 10(-7) to 6.1 x 10(-6) mol l(-1) with detection limit of 6.8 x 10(-8) mol l(-1). This method is simple, practical and relatively free interference from coexisting substances and can be successfully applied to determination of NADP in synthetic water samples and in serum samples. Moreover, the enhancement mechanisms of the fluorescence intensity in the Eu(3+)-DC system and the Eu(3+)-DC-NADP system have been also discussed.     

Fluorimetric study of the interaction between human serum albumin and quinolones-terbium complex and its application

A highly sensitive spectrofluorimetric method is proposed for determination of human serum albumin (HSA) and some quinolone drugs. Using quinolones-terbium (Tb3+) complex as a fluorescent probe, in the buffer solution of pH 7.8, HSA can remarkably enhance the fluorescence intensity of the quinolones-Tb3+ complex at 545 nm and the enhanced fluorescence intensity of Tb3+ ion is in proportion to the concentration of HSA and quinolone drugs. Optimum conditions for the determination of HSA were also investigated. The linear ranges and limits of detection are 8.0 x 10(-9) to 8.0 x 10(-8) mol L(-1), 4.20 x 10(-9) mol L(-1) (for HSA); 1.0 x 10(-6) to 4.0 x 10(-6) mol L(-1), 1.87 x 10(-8) mol L(-1) (for norfloxacin) and 1.0 x 10(-7) to 1.0 x 10(-6) mol L(-1), 4.82 x 10(-8) mol L(-1) (for enoxacine), respectively. This method is simple, practical and relatively free interference from coexisting substances, as well as much more sensitive than most of the existing assays.     

Functionalized CdS quantum dots-based luminescence probe for detection of heavy and transition metal ions in aqueous solution

Strong luminescence CdS quantum dots (QDs) have been prepared and modified with l-cysteine by a facile seeds-assistant technique in water. They are water-soluble and highly stable in aqueous solution. CdS QDs evaluated as a luminescence probe for heavy and transition metal (HTM) ions in aqueous solution was systematically studied. Five HTM ions such as silver(I) ion, copper(II) ion, mercury(II) ion, cobalt(II) ion, and nickel(II) ion significantly influence the photophysics of the emission from the functionalized CdS QDs. Experiment results showed that the fluorescence emission from CdS QDs was enhanced significantly by silver ion without any spectral shift, while several other bivalent HTM ions, such as Hg(2+), Cu(2+), Co(2+), and Ni(2+), exhibited effective optical quenching effect on QDs. Moreover, an obvious red-shift of emission band was observed in the quenching of CdS QDs for Hg(2+) and Cu(2+) ions. Under the optimal conditions, the response was linearly proportional to the concentration of Ag(+) ion ranging from 1.25 x 10(-7) to 5.0 x 10(-6)molL(-1) with a detection limit of 2.0 x 10(-8)molL(-1). The concentration dependence of the quenching effect on functionalized QDs for the other four HTM ions could be well described by typical Stern-Volmer equation, with the linear response of CdS QDs emission proportional to the concentration ranging from 1.50 x 10(-8) to 7.50 x 10(-7)molL(-1) for Hg(2+) ion, 3.0 x 10(-7) to 1.0 x 10(-5)molL(-1) for Ni(2+) ion, 4.59 x 10(-8) to 2.295 x 10(-6)molL(-1) for Cu(2+) ion, and 1.20 x 10(-7) to 6.0 x 10(-6)molL(-1) Co(2+) ion, respectively. Based on the distinct optical properties of CdS QDs system with the five HTM ions, and the relatively wide linear range and rapid response to HTM ions, CdS QDs can be developed as a potential identified luminescence probe for familiar HTM ions detection in aqueous solution.     

A new spectrofluorometric probe for the determination of trace amounts of CoA in injection, human serum and pig livers.

A new spectrofluorometric method has been developed for the determination of trace amounts of coenzyme A (CoA). Using europium (Eu3+)-tetracycline (TC) complex as a fluorescent probe in the buffer solution of pH 6.80, CoA could remarkably enhance the fluorescence intensity of the Eu3+-TC complex at lambda = 612 nm after adding H(5)IO(6) and the enhanced fluorescence intensity is in proportion to the concentration of CoA. Optimum conditions for the determination of CoA were also investigated. The dynamic range for the determination of CoA is 6.08 x 10(-8) - 1.84 x 10(-5) mol L(-1) with detection limit of 4.62 x 10(-8) mol L(-1). This method is simple, practical and relatively free of interference from coexisting substances and can be successfully applied to determination of CoA in injection, human serum and pig liver samples. Moreover, the enhancement mechanisms of the fluorescence intensity in the Eu3+-TC system and the CoA-Eu3+-TC system have been also discussed.     

New fluorimetric determination of hemoglobin used as a substitute of mimietic peroxidase

Hemoglobin (Hb) could be used as a substitute of peroxidase in the catalytic oxidation of tetra-substituted amino aluminum phthalocyanine (TAA1Pc) by H2O2. We found that the fluorescence of TAA1Pc (a red-region fluorescent dye with a maximum excitation wavelength at 606 nm and a maximum emission wavelength at 673 nm) could significantly be quenched by H2O2 in the presence of Hb. The value of F0/F (where the relative fluorescence intensity of blank solution and that of the sample solution containing Hb were given by F0 and F, respectively) is linearly related to the concentration of Hb. Based on this, a novel fluorimetric method was developed for the determination of Hb in aqueous solution. Under optimal conditions, Hb could be determined in the concentration range of 5 x 10(-11) - 12 x 10(-8) mol L(-1) with a detection limit of 1.5 x10(-11) mol L(-1). The relative standard deviation of ten replicate measurements was 1.95% for solution containing 1 x10(-9 ) mol L(-1) Hb. The proposed method has been applied to the analysis of Hb in human blood and the results were in good agreement with those reported by a hospital laboratory. So this is a new, high sensitive and precise fluorescence quenching method to determine Hb.     

Study on the fluorescence behavior of p-sulfonated calix[4,6]arene in cationic surfactant cetyltrimethylammonium bromide solution and its analytical application

The fluorescence properties of p-sulfonated calix[4,6]arene (SCnA, n=4, 6) in cationic surfactant cetyltrimethylammonium bromide (CTAB) solution were investigated. It was found that the fluorescence intensity of SCnA could be enhanced markedly by an appropriate amount of CTAB. The results indicate the formation of complex between CTAB and SCnA at a 1:1 complex stoichiometry and their association constants were calculated by applying a deduced equation. Based on the obtained results, a new fluorimetric method has been developed for rapid determination of SCnA with a good linearity in the concentration range of 2x10(-7) to 7x10(-6)mol L-1.     

Studies on interaction between gatifloxacin and human serum albumin as well as effect of copper(II) on the reaction

The binding characteristics of gatifloxacin (GTFX) and human serum albumin (HSA) have been studied by fluorescence spectroscopy in aqueous solution, and the interaction influenced by copper(II) was also explored in the paper. The results show that the two-reaction equilibrium constant and the number of binding sites were K = 1.16 x 10(5) l mol(-1), n = 1.27 for GTFX and K = 1.62 x 10(5) l mol(-1), n = 1.74 for GTFX-Cu2+, respectively. The quenching mechanism of fluorescence of HSA by GTFX is a static quenching procedure. The binding distance between GTFX and HSA and the energy transfer efficiency are obtained based on the theory of Fōrster spectroscopy energy transfer. The effect of GTFX on the conformation of HSA was also been analyzed by using synchronous fluorescence spectroscopy. The interaction of GTFX and HSA has been studied by flow-mixed microcalorimetry in the absence and presence of copper(II) and their thermodynamic parameters were obtained. The enthalpy changes and the entropy changes were calculated to be DeltaH approximately 0, DeltaS > 0 in the absence of copper(II),which indicated that static forces played major role in the interaction of GTFX and HSA, and to be DeltaH approximately 0, DeltaS > 0 in the presence of copper(II),which indicated that the static forces also played major role on the reaction. The molar free energy changes of the two reactions are identical with each other because the entropy-enthalpy compensation happened between the two reactions.     

Fluorescence properties of pyrylretinol

A fluorescent analog of retinol, 3,7-dimethyl-9-(1-pyryl)-2E,4E,6E,8E-nonatetr aene-1-ol (referred to as pyrylretinol, or 1) has been synthesized. The fluorescence properties (e.g. quantum yield, lifetime, steady-state anisotropy, and excitation/emission spectra) of this compound in various organic solvents and in dimyristoylphosphatidylcholine (DMPC) liposomes have been studied, and the results are compared with those obtained from 3-methyl-5-(1-pyryl)-2E,4E-pentadiene-1-ol (2), which has the same fused aromatic ring system but a much shorter acyclic chain. 1 and 2 form excimer in aqueous media and fluorescence anisotropies of both 1 and 2 in DMPC liposomes exhibit an abrupt decrease at approximately 21-23 degrees C, which coincides with the main phase transition temperature of DMPC liposomes, indicating that both compounds may be a useful membrane probe. In addition, the binding and quenching capability of pyrylretinol (1) to bovine serum albumin has been investigated. Pyrylretinol (1) binds with BSA with a binding constant of 3.6 x 10(4) M-1, although the value is somewhat lower than that obtained for retinol (3.06 x 10(5) M-1). Pyrylretinol (1) also quenches the BSA intrinsic fluorescence with the quenching rate constant of 1.67 x 10(13) M-1 s-1 and the value is lower than that obtained for retinol (4.06 x 10(13) M-1 s-1). The binding and quenching studies suggest that pyrylretinol (1) may serve as a useful fluorescence probe for structure/function studies of different retinoid binding proteins.     

Electrochemical detection of sequence-specific DNA using a DNA probe labeled with aminoferrocene and chitosan modified electrode immobilized with ssDNA

The electrochemical detection of sequence-specific DNA using a DNA probe labeled with aminoferrocene (AFC) is reported. Sample ssDNA was immobilized on a chitosan modified glassy carbon electrode. A sequence-known DNA with 256 bp [obtained by polymerase chain reaction (PCR)] was successfully labeled with the electro-active reagent AFC by 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide for the first time. This DNA probe labeled with AFC was applied to hybridize with a sequence-unknown DNA sample. Only the complementary sequence (cDNA) could form a double-stranded DNA (dsDNA) with the DNA probe labeled with AFC. The anodic peak currents (ipa) of the AFC bound to the dsDNA by differential pulse voltammetry were used for the determination of cDNA. The ipa of AFC was linearly related to the concentration of cDNA sequence between 1.0 x 10(-8) and 6.0 x 10(-6) mol L-1. The detection limit was 2.0 x 10(-9) mol L-1 using 3 sigma (where sigma is the standard deviation of blank solution, n = 11). The probe showed high sensitivity and selectivity.     

A novel route for immobilization of oligonucleotides onto modified silica nanoparticles

A novel approach for immobilization of probe oligonucleotides that uses zirconium phosphate modified silica nanoparticles is proposed. The surface modification of nanoparticles was carried out in two stages. Initially binding of Zr4+ to the surface of silica nanoparticles and later treated with phosphoric acid for terminal phosphate groups. Oligonucleotide probes modified with amine group at 5'-end were strongly binds to the phosphate terminated silica nanoparticles with imidazole in presence of 0.1 mol L(-1) EDC [N-ethyl-N'-(3-dimethylaminopropyl) carbodiimide], as phosphate groups are more reactive towards amine group. Various studies, i.e., synthesis of silica nanoparticles, their surface modification, probe immobilization, measurement of hybridization and effect of bovine serum albumin (BSA) were carried out during optimization of reaction conditions. The significant reduction in the background signal was observed by treating the probe modified silica nanoparticles with bovine serum albumin prior to hybridization. The probe modified silica nanoparticles were retained their properties and the hybridization was induced by exposure of single-stranded DNA (ssDNA) containing silica nanoparticles to the complementary DNA in solution. The decrease in the fluorescence signal for one mismatch and three mismatch was observed upon hybridization of probe with target DNAs, while there was no response for the random target ssDNA under the same experimental conditions. The intensity of fluorescence signal was linear to the concentration of target DNA ranging from 3.9 x 10(-9) to 3.0 x 10(-6)mol L(-1). A detection limit of 1.22 x 10(-9) mol L(-1) of oligonucleotides can be estimated. The proposed hybridization assay is simple and possesses good analytical characteristics and it can provide an effective and efficient route in the development of DNA biosensors and biochips.     

谷胱甘肽稳定的CdTe量子点荧光猝灭法测定痕量过氧化氢

以谷胱甘肽稳定的CdTe量子点作为荧光探针,基于荧光猝灭法对过氧化氢进行了定量检测,考察了缓冲溶液体系、量子点浓度、反应时间等多种因素的影响。实验结果表明,在pH=7.2的Na2HPO4-NaH2PO4缓冲液中,反应时间为15min,过氧化氢浓度为1.0×10-6～3.0×10-5 mol/L范围时,其线性回归方程为△F=9.78+7.56c(10-6 mol/L),线性相关系数和检测限分别为0.9992和1.27×10-8 mol/L。谷胱甘肽稳定的CdTe量子点荧光猝灭法已用于水样的测定,回收率在96%～103%之间,相对标准偏差RSD不大于3.3%,结果令人满意。     

Determination of ATP as a fluorescence probe with europium(III)-doxycycline.

A new spectrofluorimetric method has been developed for the determination of adenosine disodium triphosphate (ATP). We studied the interactions between the doxycycline (DC)-Eu3+ complex and adenosine disodium triphosphate (ATP) by using UV-visible absorption and fluorescence spectra. Using doxycycline (DC)-Eu3+ as a fluorescence probe, under the optimum conditions, ATP could remarkably enhance the fluorescence intensity of the DC-Eu3+ complex at lambda = 612 nm. The enhanced fluorescence intensity of the Eu3+ ion was in proportion to the concentration of ATP. The optimum conditions for the determination of ATP were also investigated. The linear ranges for ATP were 1.00 x 10(-7) - 2.00 x 10(-6) mol L(-1) with detection limits of 4.07 x 10(-8) mol L(-1). This method is simple, practical and relatively free of interference from coexisting substances, and can be successfully applied to the determination of ATP in samples. The mechanism of fluorescence enhancement between the doxycycline (DC)-Eu3+ complex and ATP was also studied.     

Chemiluminescence determination of ferulic acid by flow-injection analysis using cerium(IV) sensitized by rhodamine 6G

A simple, sensitive and rapid flow-injection chemiluminescence method has been developed for the determination of ferulic acid based on the chemiluminescence reaction of ferulic acid with rhodamine 6G and ceric sulfate in sulphuric acid medium. Strong chemiluminescence signal was observed when ferulic acid was injected into the acidic ceric sulfate solution in a flow-cell. The present method allowed the determination of ferulic acid in the concentration range of 8.0x10(-6) to 1.0x10(-4)moll(-1) and the detection limit for ferulic acid was 8.7x10(-9)moll(-1). The relative standard deviation was 2.4% for 10 replicate analyses of 1.0x10(-5)moll(-1) ferulic acid. The proposed method was applied to the determination of ferulic acid in Taita Beauty Essence samples with satisfactory results.