RESUMO
Halloysite clay nanotubes were used as a support for the immobilization of the enzyme peroxidase from clover sprouts (Trifolium), and employed together with platinum nanoparticles in 1-butyl-3-methylimidazolium hexafluorophosphate ionic liquid (Pt-BMI·PF(6)) in the development of a new biosensor for the determination of catecholamines by square-wave voltammetry. Under optimized conditions, the analytical curves showed detection limits of 0.05, 0.06, 0.07, 0.12 µM for dopamine, isoproterenol, dobutamine and epinephrine, respectively. The biosensor demonstrated high sensitivity, good repeatability and reproducibility, and long-term stability (18% decrease in response over 150 days). A recovery study of dopamine in pharmaceutical samples gave values from 97.5 to 101.4%. The proposed biosensor was successfully applied to the determination of dopamine in pharmaceutical samples, with a maximum relative error of ±1.0% in relation to the standard (spectrophotometric) method. The good analytical performance of the proposed method can be attributed to the efficient immobilization of the peroxidase in the nanoclay, and the facilitation of electron transfer between the protein and the electrode surface due to the presence of the Pt nanoparticles and ionic liquid.
Assuntos
Silicatos de Alumínio/química , Técnicas Biossensoriais/métodos , Catecolaminas/análise , Líquidos Iônicos/química , Nanopartículas Metálicas/química , Nanotubos/química , Platina/química , Argila , Eletroquímica , Enzimas Imobilizadas/química , Enzimas Imobilizadas/metabolismo , Concentração de Íons de Hidrogênio , Imidazóis/química , Peroxidases/química , Peroxidases/metabolismo , Trifolium/enzimologiaRESUMO
Gold nanoparticles dispersed in 1-butyl-3-methylimidazolium hexafluorophosphate ionic liquid (Au-BMI·PF(6)) were supported in chitin (CTN) chemically crosslinked with glyoxal and epichlorohydrin to obtain a new supported ionic liquid phase (SILP) catalyst with high catalytic activity, and providing an excellent environment for enzyme immobilization. This modified biopolymer matrix (Au-BMI·PF(6)-CTN) was used as a support for the immobilization of the enzyme peroxidase (PER) from pea (Pisum sativum), and employed to develop a new biosensor for rosmarinic acid (RA) determination in pharmaceutical samples by square-wave voltammetry. In the presence of hydrogen peroxide, the PER catalyzes the oxidation of RA to the corresponding o-quinone, which is electrochemically reduced at a potential of +0.14 V vs. Ag/AgCl. Under optimized conditions, the resulting peak current increased linearly for the RA concentration range of 0.50 to 23.70 µM with a detection limit of 70.09 nM. The biosensor demonstrated high sensitivity, good repeatability and reproducibility, and long-term stability (15% decrease in response over 120 days). The method was successfully applied to the determination of RA content in pharmaceutical samples, with recovery values being in the range of 98.3 to 106.2%. The efficient analytical performance of the proposed biosensor can be attributed to the effective immobilization of the PER enzyme in the modified CTN matrix, the significant contribution of the high conductivity of the ionic liquid, the facilitation of electron transfer promoted by gold nanoparticles, and the inherent catalytic ability of these materials.
Assuntos
Biopolímeros/química , Técnicas Biossensoriais/métodos , Cinamatos/análise , Depsídeos/análise , Ouro/química , Líquidos Iônicos/química , Nanopartículas Metálicas/química , Biocatálise , Quitina/química , Enzimas Imobilizadas/química , Enzimas Imobilizadas/metabolismo , Peróxido de Hidrogênio/química , Oxirredução , Pisum sativum/enzimologia , Peroxidase/química , Peroxidase/metabolismo , Preparações Farmacêuticas/química , Ácido RosmarínicoRESUMO
Gold nanoparticles dispersed in an ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate (Au-BMI.PF(6)) and a binuclear nickel(II) complex ([Ni(2)(HBPPAMFF)mu-(OAc)(2)(H(2)O)]BPh(4)) immobilized on functionalized silica were successfully applied in the construction of a novel sensor for the determination of fisetin by square-wave voltammetry. Under optimized conditions, the analytical curve showed two linear ranges for fisetin concentrations from 0.28 to 1.39 microM and 2.77 to 19.50 microM with a detection limit of 0.05 microM. This sensor demonstrated suitable stability (ca. 150 days; at least 500 determinations) and good repeatability and reproducibility, with relative standard deviations of 2.91 and 5.11%, respectively. The recovery study of fisetin in apple juice samples gave values from 96.4 to 106.4%. The efficient analytical performance of the proposed sensor can be attributed to the effective immobilization of the Ni(ii)Ni(ii) complex on silica and the Au-BMI.PF(6) contribution to the electrode response.
Assuntos
Técnicas Eletroquímicas/métodos , Flavonoides/análise , Ouro/química , Líquidos Iônicos/química , Nanopartículas Metálicas/química , Níquel/química , Dióxido de Silício/química , Catálise , Eletrodos , Flavonóis , Imidazóis/químicaRESUMO
Novel and effective biosensors based on Ag or Au nanoparticles dispersed in ionic liquid (IL) 1-butyl-3-methylimidazolium hexafluorophosphate (BMI.PF(6)) and laccase (Lac) from Aspergillus oryzae immobilized in chitosan (Chi) chemically cross-linked with cyanuric chloride (CC) were constructed. This enzyme catalyzes the oxidation of luteolin to the corresponding o-quinone, which is electrochemically reduced back to luteolin at 0.35 V vs. Ag/AgCl. Square-wave voltammetry was used for the electrochemical determination of luteolin at the Lac-nanoparticles-BMI.PF(6) biosensors. The best performance was obtained with 50:20:15:15% (w/w/w/w) as the graphite powder:Chi-CC:Nujol:Ag-BMI.PF(6) or Au-BMI.PF(6) composition (Lac 0.29 units mL(-1)) in 0.1 M acetate buffer solution (pH 4.0) with frequency, pulse amplitude and scan increment at 50 Hz, 100 mV, and 5.0 mV, respectively. Under optimized conditions, the cathodic currents increased linearly for the luteolin concentration range of 0.099-5.825 microM with detection limits of 0.054 +/- 0.004 microM (Ag-BMI.PF(6)) and 0.028 +/- 0.002 microM (Au-BMI.PF(6)). These biosensors demonstrated high sensitivity, good repeatability and reproducibility, and long-term stability (13% decrease in response over 70 days). The recovery study for luteolin in chamomile tea samples gave values of 91.8-104.8%. The influence of Lac immobilized in Chi-CC and nanoparticles-BMI.PF(6) contributes to the excellent performance of the biosensors.