RESUMEN

Small-molecule fluorescent probes having optimized optical properties, such as high photostability and brightness, local microenvironment sensitivity and specific subcellular localizations, are increasingly available. Although the basis for designing efficient fluorophores for bioimaging applications is well established, implementing an improvement in a given photophysical characteristic always tends to compromise another optical property. This problem has enormous consequences for in vivo imaging, where ensuring a specific localization and precise control of the probe response is challenging. Herein we discuss a fluorescent probe, CC334, as a case study of the chromenylium-cyanine family that commonly exhibits highly complex photophysical schemes and highly interfered bioanalytical responses. By an exhaustive and concise analysis of the CC334 optical responses including detailed spectroscopic calibrations, steady-state microenvironment effects, ultrafast photophysics analysis and computational studies, we elucidate a new strategy to apply the probe in the singlet oxygen reactive oxygen species (1O2-ROS) monitoring using in vitro and in vivo models. The probe provides a new avenue for designing fluorescent probes to understand the dynamic behavior of subcellular environments.

Asunto(s)

Benzopiranos/química , Colorantes Fluorescentes/química , Colorantes Fluorescentes/metabolismo , Cobalto/química , Ferrocianuros/química , Quinolinas/química , Especies Reactivas de Oxígeno/química , Análisis Espectral

RESUMEN

The use of ultraviolet light in photoreactors for wastewater treatment has become popular as an alternative of known chemical oxidative substances. UV LED light represents cheaper, robust, and versatile alternative to traditional UV lamps. In this study, it was designed and evaluated a photoreactor with an approach of chemical fluid dynamics (CFD) and experimental validation. The evaluation consisted of (1) CFD velocity profile analysis, (2) characterization of the average light distribution with potassium ferrioxalate actinometry, (3) degradation of a typical recalcitrant metallic cyanocomplex Fe(CN)63-, and (4) scavenger effect analysis in the photodegradation using potassium persulfate. Actinometrical essay concluded that the system was able to receive 1.93 µE/s. The reactor operated under turbulent regime and best result for Fe(CN)63- degradation was obtained at 4 h of operation, using 5-W UV-A LEDs, with pH ~ 7 and 10 mM de S2O82-. Baffled photoreactor demonstrated to be useful for this type of illumination and wastewater treatment.

Asunto(s)

Minería , Eliminación de Residuos Líquidos/instrumentación , Eliminación de Residuos Líquidos/métodos , Diseño de Equipo , Ferrocianuros/química , Hidrodinámica , Oxalatos/química , Oxidación-Reducción , Fotólisis , Compuestos de Potasio/química , Sulfatos/química , Rayos Ultravioleta , Aguas Residuales/química

RESUMEN

In this work nanostructured film composites of the monoamine oxidase B (MAO-B) enzyme, free or encapsulated in liposomes, were fabricated by the layer-by-layer (LbL) self-assembly technique, employing polyethylene imine (PEI) as polycation. Initially, the MAO-B enzyme was incorporated into liposomes in order to preserve its enzymatic structure ensuring their activity and catalytic stability. The LbL film growth was monitored by surface plasmon resonance (SPR) by gold resonance angle shift analysis after each bilayer deposition. Subsequently, the films were applied as amperometric biosensors for dopamine detection using Prussian Blue (PB) as the electron mediator. The biosensor fabricated by MAO-B incorporated into liposomes composed of DPPG:POPG in the ratio (1:4) (w/w) showed the best performance with a sensitivity of 0.86 (µA cm(-2))/(mmol L(-1)) and a detection limit of 0.33 mmol L(-1).

Asunto(s)

Técnicas Biosensibles , Dopamina/análisis , Monoaminooxidasa/metabolismo , Nanoestructuras/química , Dicroismo Circular , Técnicas Electroquímicas , Enzimas Inmovilizadas/química , Enzimas Inmovilizadas/metabolismo , Ferrocianuros/química , Humanos , Límite de Detección , Liposomas/química , Monoaminooxidasa/química , Polietileneimina/química , Resonancia por Plasmón de Superficie

RESUMEN

Supramolecular self-assembly has been demonstrated to be a useful approach to developing new functional nanomaterials. In this work, we used a cobalt Prussian blue analogue (PBA, Co3[Co(CN)6]2) compound and a ß-cyclodextrin (CD) macrocycle to develop a novel host-guest PBA-CD nanomaterial. The preparation of the functional magnetic material involved the self-assembly of CD molecules onto a PBA surface by a co-precipitation method. According to transmission electronic microscopy results, PBA-CD exhibited a polydisperse structure composed of 3D nanocubes with a mean edge length of 85 nm, which became shorter after CD incorporation. The supramolecular arrangement and structural, crystalline and thermal properties of the hybrid material were studied in detail by vibrational and electronic spectroscopies and X-ray diffraction. The cyclic voltammogram of the hybrid material in a 0.1 mol · L(-1) NaCl supporting electrolyte exhibited a quasi-reversible redox process, attributed to Co2+/Co3+ conversion, with an E1/2 value of 0.46 V (vs. SCE), with higher reversibility observed for the system in the presence of CD. The standard rate constants for PBA and PBA-CD were determined to be 0.07 and 0.13 s(-1), respectively, which suggests that the interaction between the nanocubes and CD at the supramolecular level improves electron transfer. We expect that the properties observed for the hybrid material make it a potential candidate for (bio)sensing designs with a desirable capability for drug delivery.

Asunto(s)

Cobalto/química , Ciclodextrinas/química , Ferrocianuros/química , Nanopartículas/química , Compuestos Organometálicos/síntesis química , Compuestos Organometálicos/química , Oxidación-Reducción , Polimerizacion

RESUMEN

A thiophene-modified screen printed electrode (SPE) for detection of the Dengue virus non-structural protein 1 (NS1), an important marker for acute phase diagnosis, is described. A sulfur-containing heterocyclic compound, the thiophene was incorporated to a carbon ink to prepare reproducible screen printed electrodes. After cured, the thiophene SPE was coated by gold nanoparticles conjugated to Protein A to form a nanostrutured surface. The Anti-NS1 antibodies immobilized via their Fc portions via Protein A, leaving their antigen specific sites free circumventing the problem of a random antibodies immobilization. Amperometric responses to the NS1 protein of dengue virus were obtained by cyclic voltammetries performed in presence of ferrocyanide/ferricyanide as redox probe. The calibration curve of immunosensor showed a linear response from 0.04 µg mL(-1) to 0.6 µg mL(-1) of NS1 with a good linear correlation (r=0.991, p<0.05). The detection limit (0.015 µg mL(-1) NS1) was lower than conventional analytical methods. In this work, thiophene monomers incorporated in the carbon ink enhanced the electroanalytical properties of the SPEs, increasing their reproducibility and sensitivity. This point-of-care testing represents a great potential for use in epidemic situations, facilitating the early diagnosis in acute phase of dengue virus.

Asunto(s)

Virus del Dengue/metabolismo , Técnicas Electroquímicas/métodos , Tiofenos/química , Proteínas no Estructurales Virales/análisis , Animales , Anticuerpos/química , Anticuerpos/inmunología , Anticuerpos Inmovilizados/química , Anticuerpos Inmovilizados/inmunología , Técnicas Biosensibles/instrumentación , Técnicas Biosensibles/métodos , Carbono/química , Línea Celular , Técnicas Electroquímicas/instrumentación , Electrodos , Ferricianuros/química , Ferrocianuros/química , Oro/química , Tinta , Nanopartículas del Metal/química , Reproducibilidad de los Resultados , Espectroscopía Infrarroja por Transformada de Fourier , Proteínas no Estructurales Virales/química , Proteínas no Estructurales Virales/inmunología

RESUMEN

This paper reports the magnetic control of nanoparticle collisions on gold ultramicroelectrode surface. Magnetite nanoparticles with diameters of 10 nm and modified with Prussian blue (Fe3O4-NPs-PB) were directed by gravitational force on the electrode surface, and spikes in current-time transients were observed. By modulating a magnetic field parallel to the electrode surface, the number of nanoparticle collisions and the nanoparticle positions could be controlled.

Asunto(s)

Ferrocianuros/química , Oro/química , Nanopartículas de Magnetita/química , Campos Magnéticos , Nanopartículas de Magnetita/ultraestructura , Microelectrodos , Propiedades de Superficie

RESUMEN

Label-free immunosensor based on amine-functionalized carbon nanotubes screen-printed electrode is described for detection of the cardiac troponin T, an important marker of acute myocardial infarction. The disposable sensor was fabricated by tightly squeezing an adhesive carbon ink containing carbon nanotubes onto a polyethylene terephthalate substrate forming a thin film. The use of carbon nanotubes increased the reproducibility and stability of the sensor, and the amine groups permitted nonrandom immobilization of antibodies against cardiac troponin T. Amperometric responses were obtained by differential pulse voltammetry in presence of a ferrocyanide/ferricyanide redox probe after troponin T incubation. The calibration curve indicated a linear response of troponin T between 0.0025 ng mL(-1) and 0.5 ng mL(-1), with a good correlation coefficient (r=0.995; p<0.0001, n=7). The limit of detection (0.0035 ng mL(-1) cardiac troponin T) was lower than any previously described by immunosensors and was comparable with conventional analytical methods. The high reproducibility and clinical range obtained using this immunosensor support its utility as a potential tool for point-of-care acute myocardial infarction diagnostic testing.

Asunto(s)

Técnicas Biosensibles , Infarto del Miocardio/sangre , Nanotubos de Carbono/química , Tereftalatos Polietilenos/química , Troponina T/sangre , Animales , Anticuerpos Inmovilizados/química , Anticuerpos Inmovilizados/aislamiento & purificación , Calibración , Técnicas Electroquímicas , Electrodos , Ferricianuros/química , Ferrocianuros/química , Humanos , Límite de Detección , Ratones , Infarto del Miocardio/diagnóstico , Infarto del Miocardio/patología , Miocardio/química , Miocardio/metabolismo , Miocardio/patología , Impresión , Reproducibilidad de los Resultados , Troponina T/aislamiento & purificación

RESUMEN

AIMS: The survival rate of freeze-dried cultures is not enough information for technological applications of micro-organisms. There could be serious metabolic/structural damage in the survivors, leading to a delay time that can jeopardize the design of a rapid biochemical oxygen demand (BOD) metabolic-based bioassay. Therefore, we will study the metabolic activity (as ferricyanide reduction activity) and the survival rate (as colony-forming units, CFU) of different Klebsiella pneumoniae freeze-dried cultures looking for stable metabolic conditions after 35days of storage. METHOD AND RESULTS: Here, we tried several simple freeze-drying processes of Kl. pneumoniae. Electrochemical measurements of ferrocyanide and survival rates obtained with the different freeze-dried cultures were used to choose the best freeze-drying process that leads to a rapid metabolic-based bioassay. CONCLUSIONS: The use of milk plus monosodium glutamate was the best choice to obtain a Kl. pneumoniae freeze-dried culture with metabolic stable conditions after storage at -20°C without the need of vacuum storage and ready to use after 20min of rehydration. We also demonstrate that the viability and the metabolic activity are not always directly correlated. SIGNIFICANCE AND IMPACT OF THE STUDY: This study shows that the use of this Kl. pneumoniae freeze-dried culture is appropriate for the design of a rapid BOD bioassay.

Asunto(s)

Análisis de la Demanda Biológica de Oxígeno/métodos , Liofilización/métodos , Klebsiella pneumoniae/metabolismo , Animales , Ferrocianuros/química , Klebsiella pneumoniae/crecimiento & desarrollo , Leche/metabolismo , Oxígeno/metabolismo , Glutamato de Sodio/química

RESUMEN

The aquapentacyanoferrate(II) ion, [Fe(II)(CN)(5)H(2)O](3-), catalyzes the disproportionation reaction of O-methylhydroxylamine, NH(2)OCH(3), with stoichiometry 3NH(2)OCH(3) → NH(3) + N(2) + 3CH(3)OH. Kinetic and spectroscopic evidence support an initial N coordination of NH(2)OCH(3) to [Fe(II)(CN)(5)H(2)O](3-) followed by a homolytic scission leading to radicals [Fe(II)(CN)(5)(•)NH(2)](3-) (a precursor of Fe(III) centers and bound NH(3)) and free methoxyl, CH(3)O(•), thus establishing a radical path leading to N-methoxyamino ((•)NHOCH(3)) and 1,2-dimethoxyhydrazine, (NHOCH(3))(2). The latter species is moderately stable and proposed to be the precursor of N(2) and most of the generated CH(3)OH. Intermediate [Fe(III)(CN)(5)L](2-) complexes (L = NH(3), H(2)O) form dinuclear cyano-bridged mixed-valent species, affording a catalytic substitution of the L ligands promoted by [Fe(II)(CN)(5)L](3-). Free or bound NH(2)OCH(3) may act as reductants of [Fe(III)(CN)(5)L](2-), thus regenerating active sites. At increasing concentrations of NH(2)OCH(3) a coordinated diazene species emerges, [Fe(II)(CN)(5)N(2)H(2)](3-), which is consumed by the oxidizing CH(3)O(•), giving N(2) and CH(3)OH. Another side reaction forms [Fe(II)(CN)(5)N(O)CH(3)](3-), an intermediate containing the nitrosomethane ligand, which is further oxidized to the nitroprusside ion, [Fe(II)(CN)(5)NO](2-). The latter is a final oxidation product with a significant conversion of the initial [Fe(II)(CN)(5)H(2)O](3-) complex. The side reaction partially blocks the Fe(II)-aqua active site, though complete inhibition is not achieved because the radical path evolves faster than the formation rates of the Fe(II)-NO(+) bonds.

Asunto(s)

Ferrocianuros/química , Hidroxilaminas/química , Catálisis , Radicales Libres/química , Cinética , Análisis Espectral

RESUMEN

Here we report the derivatization of mesoporous TiO2 thin films for the preparation of H2O2 amperometric sensors. The coordination of the bifunctional ligand 1,10 phenantroline, 5,6 dione on the surface Ti(IV) ions provides open coordination sites for Fe(II) cations which are the starting point for the growth of a layer of Prussian blue polymer. The porous structure of the mesoporous TiO2 allows the growth, ion by ion of the coordination polymer. Up to four layer of Prussian blue can be deposit without losing the porous structure of the film, which results in an enhanced response of these materials as H2O2 sensors. These porous confined PB modified electrodes are robust sensors that exhibit good reproducibility, environmental stability and high sensitivity towards H2O2 detection.

Asunto(s)

Técnicas Biosensibles/instrumentación , Conductometría/instrumentación , Electrodos , Ferrocianuros/química , Peróxido de Hidrógeno/análisis , Titanio/química , Catálisis , Diseño de Equipo , Análisis de Falla de Equipo , Peróxido de Hidrógeno/química , Porosidad

RESUMEN

Electroactive nanostructured membranes have been produced by the layer-by-layer (LbL) technique, and used to make electrochemical enzyme biosensors for glucose by modification with cobalt hexacyanoferrate redox mediator and immobilisation of glucose oxidase enzyme. Indium tin oxide (ITO) glass electrodes were modified with up to three bilayers of polyamidoamine (PAMAM) dendrimers containing gold nanoparticles and poly(vinylsulfonate) (PVS). The gold nanoparticles were covered with cobalt hexacyanoferrate that functioned as a redox mediator, allowing the modified electrode to be used to detect H(2)O(2), the product of the oxidase enzymatic reaction, at 0.0 V vs. SCE. Enzyme was then immobilised by cross-linking with glutaraldehyde. Several parameters for optimisation of the glucose biosensor were investigated, including the number of deposited bilayers, the enzyme immobilisation protocol and the concentrations of immobilised enzyme and of the protein that was crosslinked with PAMAM. The latter was used to provide glucose oxidase with a friendly environment, in order to preserve its bioactivity. The optimised biosensor, with three bilayers, has high sensitivity and operational stability, with a detection limit of 6.1 microM and an apparent Michaelis-Menten constant of 0.20mM. It showed good selectivity against interferents and is suitable for glucose measurements in natural samples.

Asunto(s)

Técnicas Biosensibles/métodos , Enzimas Inmovilizadas , Técnicas Biosensibles/instrumentación , Cobalto/química , Dendrímeros , Electroquímica/métodos , Electrodos , Ferrocianuros/química , Glucosa Oxidasa/química , Glucosa Oxidasa/metabolismo , Peróxido de Hidrógeno/análisis , Cinética , Nanopartículas del Metal/química , Microscopía de Fuerza Atómica , Oxidación-Reducción , Oxidorreductasas/metabolismo , Poliaminas/análisis , Compuestos de Estaño/química

RESUMEN

The anodic oxidation of ascorbic acid on a ruthenium oxide hexacyanoferrate modified electrode was characterized by cyclic voltammetry. On this modified surface, the electrocatalytic process allows the determination of ascorbic acid to be performed at 0.0 V and pH 6.9 with a limit of detection of 2.2 microM in a flow injection configuration. Under this experimental condition, no interference from glucose, nitrite and uric acid was noticed. Lower detection limit values were obtained by measuring flow injection analysis (FIA) responses at 0.4V (0.14 microM), but a concurrent loss of selectivity is expected at this more positive potential. Under optimal FIA operating conditions, the linear response of the method was extended up to 1 mM ascorbic acid. The repeatability of the method for injections of a 1.0 mM ascorbic acid solution was 2.0% (n=10). The usefulness of the method was demonstrated by an addition-recovery experiment with urine samples and the recovered values were in the 98-104% range.

Asunto(s)

Ácido Ascórbico/análisis , Electrodos , Análisis de Inyección de Flujo/métodos , Ácido Ascórbico/orina , Catálisis , Ferrocianuros/química , Compuestos de Rutenio/química

RESUMEN

A ruthenium oxide hexacyanoferrate (RuOHCF) modified electrode was developed. Hydrodynamic voltammetry was employed to demonstrate the remarkable electrocatalytic activity toward the oxidation of 2'-deoxyguanosine. The RuOHCF modified electrode was used as amperometric detector for 2'-deoxyguanosine determination in a FIA apparatus. The influence of various experimental conditions was explored for optimum analytical performance, and at these experimental conditions, the method exhibited a linear response range to 2'-deoxyguanosine extending from 3.8 to 252 micromol L(-1) with detection limit of 94 nmol L(-1). Applications in DNA samples were examined, and the results for determination of 2'-deoxyguanosine were in good agreement with those obtained by HPLC analysis. Studies on the kinetics of the in vitro consumption of 2'-deoxyguanosine by acetaldehyde were also performed.

Asunto(s)

Daño del ADN , ADN/química , Desoxiguanosina/análisis , Ferrocianuros/química , Análisis de Inyección de Flujo/métodos , Potenciometría/métodos , Compuestos de Rutenio/química , Catálisis , Electrodos , Análisis de Inyección de Flujo/instrumentación , Potenciometría/instrumentación

RESUMEN

The photo-induced charge transfer in four series of Prussian blue (PB) analogues was studied from photoacoustic spectra. In cobalticyanides the observed signals were assigned to a metal-to-ligand charge transfer, which appears as a shoulder below 450 nm, and to d-d transitions for Co(II), Ni(II) and Cu(II) complex salts. No evidence of metal-to-metal charge transfer was observed for this series, which is probably due to the high stability of low spin cobalt(III) in the hexacyanide complex. Photoacoustic spectra for ferricyanides are broad bands, which result particularly intense up to 750 nm. Such features were attributed to the overlapping of contributions from metal-to-ligand (<600 nm) and metal-to-metal charge transfer transitions, with probably also a minor contribution from d-d transitions in the outer metal. The spectra for the ferrocyanides series are dominated by the metal-to-ligand charge transfer band below 550 nm, approximately 100 nm above this transition in cobalticyanides. Within the studied solids, the most intense and broad metal-to-metal charge transfer bands were found for a series of low spin Co(III) high spin Co(II) hexacyanoferrates(II,III) and with similar features also for ferric ferrocyanide (Prussian blue), assigned to Fe(II)-->Co(III) and Fe(II)-->Fe(III) photo-induced transition, respectively. The first of these transitions requires of more energetic photons to be observed, its maximum falls at 580 nm while for Prussian blue it is found at 670 nm. Prussian blue analogues are usually obtained as nanometric size particles and many of them have a microporous structure. The role of surface atoms on the observed charge transfer bands in the studied series of compounds is also discussed.

Asunto(s)

Cobalto/química , Cobre/química , Ferrocianuros/química , Luz , Nitrógeno/química , Fotoquímica/métodos , Análisis Espectral/métodos , Acústica , Cianuros/química , Ferrocianuros/análisis , Ligandos , Metales/química , Modelos Químicos , Modelos Moleculares , Porosidad , Propiedades de Superficie

RESUMEN

Ions are known to concentrate in the salt-enriched phase of aqueous two-phase systems, with the only known exception being the pertechnetate anion, TcO(4)(-). We have discovered a second ion, nitroprusside anion (NP), which is markedly transferred from the salt phase to the polymer phase. The partitioning behavior of [Fe(CN)(5)NO](2-) anion was investigated in ATPS formed by poly(ethylene oxide) of molar mass 3350 and 35000 g mol(-1), and different sulfate salts (Na(2)SO(4), Li(2)SO(4), and MgSO(4)). On the basis of a model, the nitroprusside high affinity for the macromolecular phase was attributed to an enthalpic specific interaction between the anion and ethylene oxide unit. Partition coefficients increased exponentially with tie-line length increase, reaching values as high as 1000 and showing a relationship very dependent on the salt nature, but independent of the polymer molar mass.

Asunto(s)

Ferrocianuros/química , Nitroprusiato/química , Polietilenglicoles/química , Sulfatos/química , Agua/química , Aniones , Soluciones/química , Termodinámica

RESUMEN

Adsorptive interaction of p-aminophenol and p-nitrophenol in the concentration range 10(-4)-10(-5) M and at room temperature (30+/-1 degrees C) was studied with antimony, cadmium, and zirconium ferrocyanides. The interaction followed the Langmuir type of adsorption in general. The p-nitrophenol was found to have greater affinity for the antimony, cadmium, and zirconium ferrocyanides then the p-aminophenol.

Asunto(s)

Aminofenoles/química , Antimonio/química , Cadmio/química , Ferrocianuros/química , Nitrofenoles/química , Circonio/química , Adsorción , Soluciones/química , Propiedades de Superficie , Agua/química

RESUMEN

Prussian blue (PB) particles with the size of ca. 5 nm were synthesized and immobilized in a multilayer structure, as a strategy for the potential development of an amperometric transducer for oxidase-enzyme-based biosensors. Multilayer films composed of PB and poly(allylamine hydrochloride) (PAH) were prepared via layer-by-layer (LbL) sequential deposition. The process was carefully monitored by UV-vis spectroscopy and cyclic voltammetry. The increase of the redox current peaks during the layer-by-layer deposition demonstrated that charge propagation within the film occurs. Linear increase of UV-vis absorbance with the number of deposited bilayers indicates that well-organized systems have been elaborated. ITO electrodes coated with PB/PAH films were used successfully for detecting H2O2, sensitivity being dependent on the number of PB/PAH layers.

Asunto(s)

Técnicas Biosensibles , Ferrocianuros/síntesis química , Nanoestructuras/química , Adsorción , Técnicas Biosensibles/instrumentación , Electroquímica , Enzimas Inmovilizadas/química , Diseño de Equipo , Ferrocianuros/química , Oxidorreductasas/química