Human Saliva-Based Quantitative Monitoring of Clarithromycin by Flow Injection Chemiluminescence Analysis: A Pharmacokinetic Study

Human saliva quantitative monitoring of clarithromycin (CLA) by chemiluminescence (CL) with flow injection analysis was proposed for the first time, which was based on the quenching effect of CLA on luminol–bovine serum albumin (BSA) CL system with a linear range from 7.5?×?10^?4 to 2.0 ng/ml. This proposed approach, offering a maximum sample throughput of 100 h^?1, was successfully applied to the quantitative monitoring of CLA levels in human saliva during 24 h after a single oral dose of 250 mg intake, with recoveries of 95.2～109.0 % and relative standard deviations lower than 6.5 % (N?=?7). Results showed that CLA reached maximum concentration of 2.28?±?0.02 μg/ml at approximately 3 h, and the total elimination ratio was 99.6 % in 24 h. The pharmacokinetic parameters including absorption rate constant (0.058?±?0.006 h^?1), elimination rate constant (0.149?±?0.009 h^?1) and elimination half-life time (4.66?±?0.08 h) were obtained. A comparison of human saliva and urine monitoring was also given. The mechanism study of BSA–CLA interaction revealed the binding of CLA to BSA is an entropy driven and spontaneous process through hydrophobic interaction, with binding constant K _BSA–CLA of 4.78?×?10⁶ l/mol and the number of binding sites n of 0.82 by flow injection–chemiluminescence model. Molecular docking analysis further showed CLA might be in subdomain IIA of BSA, with K _BSA–CLA of 6.82?×?10⁵ l/mol and ΔG of ?33.28 kJ/mol.     

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.     

Study on Interactions of Phenolic Acid-Like Drug Candidates with Bovine Serum Albumin by Capillary Electrophoresis and Fluorescence Spectroscopy

The interactions of the phenolic acids cinnamic acid (CNA), ferulic acid (FA), caffeic acid (CA) and chlorogenic acid (CLA) with bovine serum albumin (BSA) were investigated and compared using affinity capillary electrophoresis (ACE) and the fluorescence quenching methods. ACE gives binding constants (K _b) and thermodynamic parameters. The thermodynamic parameters show that each of four phenolic acids bind to BSA mainly by hydrogen bonds, electrostatic and hydrophobic interactions. The fluorescence quenching method provided quenching constant K _sv, binding site number n and K _b. The fluorescence results indicate that BSA fluorescence quenching is mainly a static quenching process. The binding constants (K _b) of CNA, FA, CA and CLA were from 2.52×10⁴ to 7.90×10⁴ L⋅mol⁻¹ from ACE experiments and 1.19×10⁴ to 5.21×10⁴ L⋅mol⁻¹ from fluorescence, their increase corresponded to the increase in the number of hydroxyl groups. These results imply that molecular structure and the number of hydroxyl groups of phenolic acids play act key roles in the affinity of natural phenolic acids towards BSA.     

Study on the Interaction of Raloxifene and Bovine Serum Albumin by the Tachiya Model

The interaction of bovine serum albumin (BSA) with raloxifene was assessed via fluorescence spectroscopy. The number of binding sites and the apparent binding constants between raloxifene and BSA were analyzed using the Tachiya model and Stern-Volmer equation, respectively. The apparent binding constant and the number of binding sites at 298 K were 2.33×10⁵ L?mol^?1 and 1.0688 as obtained from the Stern-Volmer equation and 2.00×10⁵ L?mol^?1 and 2.6667 from the Tachiya model. The thermodynamic parameters ΔH and ΔS were calculated to be 69.46 kJ?mol^?1 and 121.12 J?K^?1?mol^?1, respectively, suggesting that the force acting between raloxifene and BSA was mainly a hydrophobic interaction. The binding distance between the donor (BSA) and acceptor (raloxifene) was 4.77 nm according to Förster’s nonradiational energy transfer theory. It was also found that common metal ions such as K⁺, Cu²⁺, Zn²⁺, Mg²⁺ and Ca²⁺ decreased the apparent association constant and the number of binding sites between raloxifene and BSA.     

IONIC STRENGTH EFFECTS ON THE GROUND STATE COMPLEXATION and TRIPLET STATE ELECTRON TRANSFER REACTION BETWEEN ROSE BENGAL and METHYL VIOLOGEN

Abstract— The equilibrium constants, K_c, for complexation between methyl viologen dication (MV²+) and Rose Bengal, or Eosin Y, decrease with increasing ionic strength. At zero ionic strength K_c is 6500 (± 500) mol^?1 dm³ for Rose Bengal and 3200 (± 200) mol^?1 dm³ for Eosin Y, and these values decrease to 1500 (± 100) and 680 (± 40) mol^?1 dm³, respectively, at an ionic strength of 0.1 mol dm^?3. K_c is independent of pH between 4.5 and 10. ΔH is -25 (± 1) kJ mol^?1 for complexation with either dye, whereas ΔS is -15 (± 3) J K^?1 mol^?1 for Rose Bengal, and - 23 (± 3) J K^?1 mol^?1 for Eosin Y. The complexation constant for Rose Bengal and the neutral viologen, 4,4'-bipyridinium-N, N'-di(propylsulphonate), (4,4'-BPS), is 420 (± 35) mol^?1 dm³, and independent of ionic strength. No complexation could be observed for either Rose Bengal or Eosin with another neutral viologen, 2,2'-bipyridinium-N,N'-di(propylsulphonate), (2,2'-BPS). MV²+ quenches the triplet state of Rose Bengal with a rate constant of 7 × 10⁹ mol^?1 dm³ s^?1, and this rate constant decreases slightly as ionic strength increases. The cage escape yield following quenching, Φ_cc is very low (Φ_cc= 0.02 (± 0.005), and independent of ionic strength. 4,4'-BPS quenches the triplet state of Rose Bengal with a rate constant of 2.2 (± 0.1) × 10⁹ mol^?1 dm³ s^?1, and gives a cage escape yield of 0.033 (± 0.006). 2,2'-BPS quenches the Rose Bengal triplet with a rate constant of 6 (± 1) × 10⁸ mol^?1 dm³ s^?1 and gives a cage escape yield of 0.07 (± 0.01). Conductivity measurements indicate that MV²+(Cl^?)₂ is completely dissociated at concentrations below 2 × 10^?2 mol dm^?3.     

Enantioselective recognition of penicillamine enantiomers on bovine serum albumin-modified glassy carbon electrode

As a natural chiral selector, bovine serum albumin (BSA) has been used to recognize penicillamine (Pen) enantiomers through electrochemical methods. The recognition and assay rely on the stereoselectivity of BSA embedded in ultrathin Al₂O₃ sol–gel film coated on the surface of glassy carbon electrode (BSA/GCE). The enantioselective interaction between Pen enantiomers and BSA was monitored by cyclic voltammetry and electrochemical impedance spectroscopy measurements, from which larger response signals were obtained from d-Pen. The factors influencing the performance of the modified biosensor were also investigated. The association constant (K) was calculated to be 1.93?×?10⁴?L?mol^?1 for d-Pen and 1.20?×?10³?L?mol^?1 for l-Pen. A good linear response was exhibited with the concentration of Pen enantiomers by BSA/GCE over the range of 1?×?10^?8–1?×?10^?1?mol?L^?1 with a detection limit of 3.31?×?10^?9?mol?L^?1.     

Multi-spectroscopic Study on the Interaction between CdTe Quantum Dots and Bovine Serum Albumin

The interaction between CdTe quantum dots (QDs) and bovine serum albumin (BSA) was systematically investigated by fluorescence, UV‐vis absorption and circular dichroism (CD) spectroscopy under physiological conditions. The experimental results showed that the fluorescence of BSA could be quenched by CdTe QDs with a static quenching mechanism, indicating that CdTe QDs could react with BSA. The quenching constants according to the modified Stern‐Volmer equation were obtained as 1.710×10⁶, 1.291×10⁶ and 1.010×10⁶ L·mol^?1 at 298, 304, and 310 K, respectively. ΔH, ΔS and ΔG for CdTe QDs‐BSA system were calculated to be ?33.68 kJ·mol^?1, 6.254 J·mol^?1·K^?1 and ?35.54 kJ·mol^?1 (298 K), respectively, showing that electrostatic interaction in the system played a major role. According to F?rster theory, the distance between Trp‐214 in BSA and CdTe QDs was given as 2.18 nm. The UV‐vis, synchronous fluorescence and CD spectra confirmed further that the conformations of BSA after addition of CdTe QDs have been changed.     

Determination of Dopamine Using 2-(4-Boronophenyl)quinoline-4-carboxylic Acids as Fluorescent Probes

The selective identification of dopamine is a significant issue because this compound is an important neurotransmitter closely related to Parkinson’s disease and other mental disorders. 2-(4-Boronophenyl)quinoline-4-carboxylic acid (PBAQA) has been previously reported as a water-soluble fluorescent probe for catechol. However, there are no significant differences in the binding constants between catechol and catecholamines, such as dopamine or levodopa. Here a series of bis-boronic acid compounds based on PBAQA were synthesized and the binding activities were characterized. As a representative compound, the binding constant of 4-(4-((3-(3-borono-4-chlorobenzamido)propyl)carbamoyl)quinolin-2-yl)boronic acid to dopamine is up to 10⁴?L?mol^?1 and much higher than previously reported boronic acid probes. Dopamine selectivity may be achieved by the variation of the substituents in the probe molecules. 4-(4-((3-(3-Borono-4-methoxybenzamido)propyl)carbamoyl)quinolin-2-yl)boronic acid has a stronger binding affinity to dopamine (K_a=5204?±?106?L?mol^?1) than catechol (K_a=2588?±?273?L?mol^?1) or levodopa (K_a=2383?±?273?L?mol^?1). This fluorescence response was used for determining dopamine in a range from 5?×?10^?5?mol?L^?1 to 5?×?10^?4?mol?L^?1 with a detection limit of 7.7?×?10^?6?mol?L^?1. This compound has been successfully used for the assay of dopamine in rabbit plasma, exhibiting excellent specificity. It is believed that synthesized compounds hold great promise as practical platforms to monitor dopamine levels.     

Synthesis,structure and spectroscopic studies on DNA binding,BSA interaction of a nickel(II) complex containing l–methionine Schiff base and 1,10-phenanthroline

A new nickel(II) complex, [Ni(o-van-L-met)(phen)(CH₃OH)] (o-van-L-met = Schiff base derived from o-vanillin and l-methionine, phen = 1,10–phenanthroline), has been synthesized and characterized by elemental analyses, IR spectra, and single-crystal X-ray diffraction. The crystal structure shows nickel is six-coordinate in a distorted octahedral geometry. In this crystal, molecules form a 2-D plane structure via hydrogen bonds and π–π interactions. The interaction of the complex with calf thymus DNA (CT-DNA) was investigated by absorption, fluorescence, circular dichroism (CD), spectroscopies, and viscosity measurement. The complex binds to CT-DNA in an intercalative mode with a binding constant of (4.7 ± 0.5) × 10⁴ M^?1. The interaction of the complex with bovine serum albumin (BSA) was also studied by the multispectroscopic methods. Results illustrated that the nickel(II) complex can effectively quench the intrinsic fluorescence of BSA via a static quenching mechanism and cause conformational changes. The binding constant K_b was (6.3 ± 1.6) × 10⁴ M^?1 and the binding site number n was 0.96 ± 0.04; its bind site was located within subunit IIA of BSA.     

Spectrofluorimetric determination of niobium with morin enhanced by cetyltrimethylammonium bromide micelles

The effect of surfactants on the fluorescence of the niobium—morin system is described. Cationic surfactants strongly enhanced the intensity (e.g., cetyltrimethylammonium bromide (CTAB) gives an 80-fold increase), while anionic and non-ionic surfactants are without effect. The formation of 1:1 and 1:3 (Nb:morin) complexes is demonstrated spectrophotometrically. The conditional stability constants for these complexes in CTAB micelles are β₁ = (1.14 ± 0.01) × 10⁴ l mol^?1 amd β₃ = (5.66 ± 0.02 × 10¹⁰ l³ mol^?3. The micellar-enhanced fluorimetric method has a 1 μg l^?1 detection limit, and is highly selective. The r.s.d. for the determination of 50 μg l^?1 Nb is 3.5%.     

百草枯与牛血清白蛋白结合作用的荧光光谱

在模拟动物体生理条件下, 用荧光光谱和紫外-可见吸收光谱法研究了在不同温度下, 百草枯(PQ)与牛血清白蛋白(BSA)结合反应的光谱行为. 试验发现, PQ对BSA有较强的荧光猝灭作用. 用Stern-Volmer和Lineweaver-Burk方程分别处理试验数据, 发现BSA与PQ发生反应生成了新的复合物, 属于静态荧光猝灭, 发生分子内的非辐射能量转移. 根据F?rster的偶极-偶极非辐射能量转移理论计算出结合位置距离212位色氨酸残基2.07 nm. 由Lineweaver-Burk方程求出了不同温度下反应时复合物的形成常数K_LB (297 K: 2.035×10⁴ L•mol^－1; 304 K: 3.256×10⁴ L•mo^－1; 311 K: 2.889×10⁴ L•mol^－1)及对应温度下结合反应的热力学参数(⊿H^Ø＝18.50 kJ•mol^－1;⊿S^Ø＝144.7 J•K^－1/145.2 J•K^－1/141.0 J•K^－1; ⊿G^Ø＝－24.50 kJ•mol^－1/－25.66 kJ•mol^－1/－25.36 kJ•mol^－1), 证明二者主要靠疏水作用力结合. 同时用三维荧光光谱及同步荧光光谱法探讨了PQ对BSA构象的影响, 为预防和医治PQ中毒提供了重要依据.     

Spectroscopic Studies on the Binding of Kaempferol‐3,7‐α‐L‐rhamnopyranoside to Bovine Serum Albumin

The binding of kaempferol‐3,7‐α‐L‐rhamnopyranoside (KRR) with bovine serum albumin (BSA) was investigated by different spectroscopic methods under simulative physiological conditions. Analysis of ?uorescence quenching data of BSA by KRR at different temperatures using Stern‐Volmer methods revealed the formation of a ground state KRR‐BSA complex with moderate binding constant of the order 10⁴ L·mol^?1. The existence of some metal ions could weaken the binding of KRR on BSA. The changes in the van't Hoff enthalpy (ΔH⁰) and entropy (ΔS⁰) of the interaction were estimated to be ?26.53 kJ·mol^?1 and 3.33 J·mol^?1·K^?1 and both hydrophobic and electrostatic forces contributed to stabilizing the BSA‐KRR complex. According to the F?ster theory of non‐radiation energy transfer, the distance r between the donor (BSA) and the acceptor (KRR) was obtained (r=2.83 nm). Site marker competitive experiments showed that KRR could bind to Site I of BSA. In addition, synchronous fluorescence, UV‐Vis absorption and circular dichroism (CD) results indicated that the KRR binding could cause conformational changes of BSA.     

Studies on Thermodynamics Features of the Interaction between Imidacloprid and Bovine Serum Albumin

At different temperatures, the interactions between imidacloprid （IMI） and bovine serum albumin （BSA） were investigated with a fluorescence quenching spectrum, a synchronous fluorescence spectrum, a three-dimensional fluorescence spectrum and an ultraviolet-visible spectrum. The average values of bonding constants （KLB： 3.424 × 10^4 L,mol^-1）, thermodynamic parameters （△H： 5.188 kJ,mol^-1, △G^（○—）：-26.36 kJ,mol^-1, △S： 103.9 J,K^-1,mol^-1） and the numbers of bonding sites （n： 1.156） could be obtained through Stern-Volmer, Lineweaver-Burk and ther- modynamic equations. It was shown that the fluorescence of BSA could be quenched for its reactions with IMI to form a certain kind of new compound. The quenching belonged to a static fluorescence quenching, with a non-radiation energy transfer happening within a single molecule. The thermodynamic parameters agree with △H〉 0, △S〉0 and△G^（○-）〈0, suggesting that the binding power between IMI and BSA should be mainly a hydrophobic interaction.     

Mechanistic Aspects of Ligand Substitution on the Hydroxopentaaquarhodium(III) Ion in Aqueous Solution by Sulfur‐Containing Bioactive Ligands

The kinetics of the interactions between three sulfur‐containing ligands, thioglycolic acid, 2‐thiouracil, glutathione, and the title complex, have been studied spectrophotometrically in aqueous medium as a function of the concentrations of the ligands, temperature, and pH at constant ionic strength. The reactions follow a two‐step process in which the first step is ligand‐dependent and the second step is ligand‐independent chelation. Rate constants (k₁ ～10^?3 s^?1 and k₂ ～10^?5 s^?1) and activation parameters (for thioglycolic acid: ΔH₁^≠ = 22.4 ± 3.0 kJ mol^?1, ΔS₁^≠ = ?220 ± 11 J K^?1 mol^?1, ΔH₂^≠ = 38.5 ± 1.3 kJ mol^?1, ΔS₂^≠ = ?204 ± 4 J K^?1 mol^?1; for 2‐thiouracil: ΔH₁^≠ = 42.2 ± 2.0 kJ mol^?1, ΔS₁^≠ = ?169 ± 6 J K^?1 mol^?1, ΔH₂^≠ = 66.1 ± 0.5 kJ mol^?1, ΔS₂^≠ = ?124 ± 2 J K^?1 mol^?1; for glutathione: ΔH₁^≠ = 47.2 ± 1.7 kJ mol^?1, ΔS₁^≠ = ?155 ± 5 J K^?1mol^?1, ΔH₂^≠ = 73.5 ± 1.1 kJ mol^?1, ΔS₂^≠ = ?105 ± 3 J K^?1 mol^?1) were calculated. Based on the kinetic and activation parameters, an associative interchange mechanism is proposed for the interaction processes. The products of the reactions have been characterized from IR and ESI mass spectroscopic analysis. A rate law involving the outer sphere association complex formation has been established as      

Dynamic proton magnetic resonance studies on complex spin systems. Non-mutual three-spin exchange in N-(trideuteriomethyl)-2-cyanoaziridine

At room temperature and below, the proton NMR spectrum of N-(trideuteriomethyl)-2-cyanoaziridine consists of two superimposed ABC patterns assignable to two N-invertomers; a single time-averaged ABC pattern is observed at 158.9°C. The static parameters extracted from the spectra in the temperature range from –40.3 to 23.2°C and from the high-temperature spectrum permit the calculation of the thermodynamic quantities ΔH⁰ = ?475±20 cal mol^?1 (?1.987 ± 0.084 kJ mol^?1) and ΔS⁰ = 0.43±0.08 cal mol^?1 K^?1 (1.80±0.33 J mol^?1 K^?1) for the cis ? trans equilibrium. Bandshape analysis of the spectra broadened by non-mutual three-spin exchange in the temperature range from 39.4–137.8°C yields the activation parameters ΔH_tc^≠ = 17.52±0.18 kcal mol^?1 (73.30±0.75 kJ mol^?1), ΔS_tc^≠ = ?2.08±0.50 cal mol^?1 K^?1 (?8.70±2.09 J mol^?1 K^?1) and ΔG_tc^≠ (300 K) = 18.14±0.03 kcal mol^?1 (75.90±0.13 kJ mol^?1) for the trans → cis isomerization. An attempt is made to rationalize the observed entropy data in terms of the principles of statistical thermodynamics.     

抗肿瘤药物5-氟尿嘧啶与人血清白蛋白相互作用的热力学研究

在298.15 K下,根据本结合过程的假设和Langmuir结合理论, 用等温滴定微量热和圆二色谱分析法研究了抗肿瘤药物5-氟尿嘧啶(5-FU)与人血清白蛋白(HSA)的相互作用. 研究结果表明, 蛋白质(HSA)与药物配体5-氟尿嘧啶的相互作用存在两类结合位点. 第一类结合, 结合位点数N＝71±0.1, 结合常数 K＝(1.46±0.016)×10⁵ L•mol^－1, 结合焓ΔH＝(39.61±0.220) kJ•mol^－1, 结合熵ΔS＝(231.68±0.025) J•mol^－1•K^－1, 结合自由能ΔG＝(－29.48±0.030) kJ•mol^－1. 结合过程为熵驱动过程, 疏水相互作用是过程的主要推动力;第二类结合, 结合位点数N＝140±0.2, 结合常数 K＝(1.49±0.032)×10⁵ L•mol^－1, 结合焓ΔH＝(－19.31±0.103) kJ•mol^－1, 结合熵ΔS＝(34.30±0.055) J•mol^－1•K^－1, 结合自由能ΔG＝(－29.53±0.041) kJ•mol^－1, 结合过程为焓-熵协同驱动过程, 氢键和静电相互作用是过程的主要推动力. 圆二色谱分析结果表明, 在两类结合过程中, 药物5-氟尿嘧啶(5-FU)的作用致使蛋白质(HSA)二级结构单元的相对含量发生了变化.     

Effect of Hydrogenation on Ring C of Flavonols on Their Affinity for Bovine Serum Albumin

In this paper, the effect of hydrogenation on ring C of flavonols on the affinity for bovine serum albumin was investigated. Two differently substituted B-ring hydroxylation flavonols (myricetin and quercetin) and their dihydrides (dihydromyricetin and dihydroquercetin) were used to study their affinities for BSA by quenching the intrinsic BSA fluorescence in solution. From the spectra, the bimolecular quenching constants, the binding constants, the number of binding sites and the binding distances were calculated. The hydroxylation on ring B and hydrogenation on ring C of flavonols significantly affected the binding/quenching process; in general, the hydroxylation increased the affinity and the hydrogenation decreased the affinity. For myricetin and quercetin, the binding constants (K _a) for BSA were 1.84×10⁸ L⋅mol⁻¹ and 3.83×10⁷ L⋅mol⁻¹. For dihydromyricetin, the binding constant was 1.36×10⁴ L⋅mol⁻¹, while dihydroquercetin hardly quenched the BSA intrinsic fluorescence. These results showed that hydrogen bonding and conjugative effects may play an important role in binding of flavonols to BSA. These results also showed that the properties of flavonols are related to their chemical structure.     

Effects of Temperature and Common Ions on Binding of Puerarin to BSA

The effects of temperature and common ions on binding of puerarin to bovine serum albumin (BSA) are investigated. The binding constants (K _a) between puerarin and BSA are 1.13×10⁴ L⋅mol⁻¹ (20 °C) and 1.54×10⁴ L⋅mol⁻¹ (30 °C), and the number of binding sites (n) is (0.95±0.02). However, at a higher temperature (40 °C) the stability of the puerarin–BSA system decreases, which results in a lower binding constant (1.58×10³ L⋅mol⁻¹) and number of binding sites (n=0.73) of the puerarin–BSA system. However, the presence of Cu²⁺ and Fe³⁺ ions increases the binding constants and the number of binding sites in the puerarin–BSA complex.     

Spectroscopic investigations of hematoxylin–Eu(III) complex interacting with Herring-sperm DNA

The interaction of HE–Eu(III) complex (HE?=?hematoxylin) with Herring-sperm DNA (hsDNA) has been studied by absorption spectra, fluorescence, and viscosity measurements in physiological buffer (pH?=?7.40). The binding constant of HE–Eu(III) complex to hsDNA was obtained by double reciprocal method at 298 and 310?K and the corresponding thermodynamic parameters (Δ_r Hm??=?8.55?×?10⁴?J?mol^?1, Δ_r Gm??=??3.01?×?10⁴?J?mol^?1, Δ_r Sm??=?387.95?J?mol^?1?K^?1) were calculated, showing that the interaction between HE–Eu(III) complex and hsDNA was driven mainly by entropy. The value of K indicated that the binding mode of HE–Eu(III) complex with DNA was not classical intercalation. These results were further supported by viscosity method and competitive binding experiment. Scatchard analysis suggests that the interaction mode was a mixed binding, which contains partial intercalation and groove binding.     

Electrocatalysis of Horseradish Peroxidase Immobilized on Cobalt Nanoparticles Modified ITO Electrode

Abstract

It is the first time that Horseradish peroxidase (HRP) was successively immobilized on the magnetic cobalt nanoparticles modified ITO (indium tin oxide) electrode. Morphologies of electrode surface were featured by the field emission‐scanning electron microscope (FSEM). Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) were used to characterize the modified process of electrode. Direct electrochemistry and electrocatalysis of HRP immobilized on nano‐Co/ITO were investigated. The biosensor exhibited high sensitivity, good stability, and excellent electrocatalytic activity to the reduction of H₂O₂. Under the optimized experimental conditions, a calibration curve over 2.0×10^?9～2.0×10^?8 mol l^?1 and 2.0×10^?7～2.0×10^?6 mol l^?1, with a limit of detection of 1.9×10^?9 mol l^?1 was obtained. The apparent Michaelis‐Menten constant (K _M ^app ) for HRP/nano‐Co/ITO electrode was calculated to be 0.79 mmol l^?1, indicating a higher affinity of HRP attached on the modified electrode.