Miriam Gamero | Universidad Autónoma de Madrid (original) (raw)

Papers by Miriam Gamero

Analytica Chimica Acta, 2013

Abstract We report the electrocatalytic response of a lactate biosensor, based on a 3-dimensional... more Abstract We report the electrocatalytic response of a lactate biosensor, based on a 3-dimensional ordered macroporous (3DOM) gold electrode, as a function of the pore layer number. The biosensor was developed by covalent immobilization of lactate oxidase (LOx) to a self-assembled monolayer of dithiobis-N-succinimidyl propionate (DTSP). The binding of DTSP to the gold surface was studied by X-ray photoelectron spectroscopy (XPS), indicating the existence of S [BOND] Au bonds.

A study on optical and electrochemical properties resulting upon interaction of Schiff base ligan... more A study on optical and electrochemical properties resulting upon interaction of Schiff base ligands with gold nanoparticles is presented. The measurements of the optical absorption and fluorescence properties have provided important information about structure-properties dependence. We show that in function of the isomer structure and its attachment orientation with respect to the metal nanoparticle, their optical properties can be modulated.

Metal Powder Report, Jan 1, 2011

Previous studies have shown that pure Mg that is reinforced by powder metallurgy (Mg(PM)) is a pr... more Previous studies have shown that pure Mg that is reinforced by powder metallurgy (Mg(PM)) is a promising biodegradable material, because it circumvents the drawbacks of the toxic components of Mg alloy implants. However, its degradation rate is high, which can be reduced with fluoride coatings (Mg(PM)F). This protective effect is temporary, because chloride induces further biodegradation of Mg(PM) in biological media. The aim of this report was to examine the effects of phosphates on Mg(PM)F in chloride-containing medium. By surface analysis of Mg(PM)F, the aggressive activity of chlorides induced a rapid decrease in F content of the layer. However, by electrochemical impedance spectroscopy and EDX, the surface attack was hindered in the presence of phosphates that precipitated onto the regions where localized attack occurred and formed a more protective P-containing layer. Our results highlight the robust activity of phosphates, which act synergistically with fluorides, controlling the degradation of F-coating in biological media and prolonging the service period of temporary Mg(PM)F implants.► Phosphates hinder the corrosion of Mg by chlorides and reduce its degradation rate. ► The service period of F-treated Mg implants may be extended by phosphates. ► F- treated Mg reinforced by powder metallurgy is a promising biomaterial.

Materials Science and …, Jan 1, 2011

The development of a biodegradable metallic implant demands a precisely defined degradation profi... more The development of a biodegradable metallic implant demands a precisely defined degradation profile and adequate mechanical properties. Mg has been proposed for this purpose but it has an excessively high corrosion rate and insufficient yield strength. In the present work pure Mg mechanically reinforced by a powder metallurgy (Mg(PM)) route and treated with KF was used. The effect of chlorides, at the physiological level, on four fluoride conversion coatings (F-CC) formed on Mg(PM) was evaluated comparatively. The behavior of Mg(PM) during fluoride treatments (0.01 M-0.3 M fluoride-containing solutions) before and after the addition of chlorides (8 g L -1 NaCl) was investigated by conventional corrosion techniques and by scanning electrochemical microscopy (SECM) complemented with SEM observations and EDX analysis. Results showed that the composition and the microstructural characteristics of the F-CCs as well as their corrosion behavior change with KF concentration and immersion time. Treatments in the 0.01 M-0.1M KF range prove to be effective to protect Mg(PM) against corrosion in the absence of chlorides while higher KF solution concentration (0.3 M) adversely affects the corrosion resistance of this metal. In the presence of chloride ions the F-CCs progressively lose their fluoride content and their corrosion resistance at a rate that depends on the treatment conditions. Such temporary corrosion protection is appropriate for biodegradable implants.

Biosensors & Bioelectronics, Jan 1, 2010

The design and characterization of a lactate biosensor using a nanostructured rough gold surface ... more The design and characterization of a lactate biosensor using a nanostructured rough gold surface as a transducer is reported. The biosensor is developed by immobilization of lactate oxidase (LOx), on a rough gold electrode modified with a self-assembled monolayer of dithiobis-N-succinimidyl propionate (DTSP). This bifunctional reagent preserves the rough gold structure and allows further covalent immobilization of the enzyme through the terminal succinimidyl groups. The rough gold electrode is characterized using field emission scanning electron microscopy (FE-SEM) and atomic force microscopy (AFM). The preferential orientation and average crystallite size are obtained by X-ray diffraction (XRD). The resulting lactate oxidase monolayers are characterized by electrochemical impedance spectroscopy (EIS). This nanostructured transducer allows higher mediated electrocatalytic activity than polycrystalline ones. The biosensor response to increasing lactate concentrations, using hydroxymethylferrocene as a redox mediator in solution, is linear up to 1.2 mM with a sensitivity of 1.49 μA mM−1.

Journal of applied electrochemistry, Jan 1, 2010

A study has been performed to select optimum process conditions (temperature, pH, reagent concent... more A study has been performed to select optimum process conditions (temperature, pH, reagent concentration, reaction kinetics, deposition time, etc.) in gold deposition on Si(n) from sulphite/thiosulphate electrolytic baths. Gold deposits have been obtained by electrochemical techniques such as constant potential, constant current, cyclic voltammetry and pulsating overpotential, in diffusional regime or by charge transfer control, at two pH values (6 and 9) and two temperatures (30 and 50 °C). The surface morphology of the Au deposits was studied by scanning electron microscopy (SEM), the preferred orientation and average size of the Au electrodeposited particles on n-Si substrates were obtained by X-ray diffraction (XRD), and qualitative and semiquantitative analysis of the gold sample was performed by energy dispersive X-ray (EDX) and X-ray photoelectron spectroscopy (XPS). The surface sulphur content was much lower or almost zero for gold samples obtained at pH 9 compared to those obtained at pH 6. However, when the different methods were compared at pH 6, both cyclic voltammetry and pulsating overpotential deposition led to deposits with a low or zero sulphur content. The results also show that various morphologies with different grain sizes can be obtained without the addition of additives.

Analytica Chimica Acta, 2013

Abstract We report the electrocatalytic response of a lactate biosensor, based on a 3-dimensional... more Abstract We report the electrocatalytic response of a lactate biosensor, based on a 3-dimensional ordered macroporous (3DOM) gold electrode, as a function of the pore layer number. The biosensor was developed by covalent immobilization of lactate oxidase (LOx) to a self-assembled monolayer of dithiobis-N-succinimidyl propionate (DTSP). The binding of DTSP to the gold surface was studied by X-ray photoelectron spectroscopy (XPS), indicating the existence of S [BOND] Au bonds.

A study on optical and electrochemical properties resulting upon interaction of Schiff base ligan... more A study on optical and electrochemical properties resulting upon interaction of Schiff base ligands with gold nanoparticles is presented. The measurements of the optical absorption and fluorescence properties have provided important information about structure-properties dependence. We show that in function of the isomer structure and its attachment orientation with respect to the metal nanoparticle, their optical properties can be modulated.

Metal Powder Report, Jan 1, 2011

Previous studies have shown that pure Mg that is reinforced by powder metallurgy (Mg(PM)) is a pr... more Previous studies have shown that pure Mg that is reinforced by powder metallurgy (Mg(PM)) is a promising biodegradable material, because it circumvents the drawbacks of the toxic components of Mg alloy implants. However, its degradation rate is high, which can be reduced with fluoride coatings (Mg(PM)F). This protective effect is temporary, because chloride induces further biodegradation of Mg(PM) in biological media. The aim of this report was to examine the effects of phosphates on Mg(PM)F in chloride-containing medium. By surface analysis of Mg(PM)F, the aggressive activity of chlorides induced a rapid decrease in F content of the layer. However, by electrochemical impedance spectroscopy and EDX, the surface attack was hindered in the presence of phosphates that precipitated onto the regions where localized attack occurred and formed a more protective P-containing layer. Our results highlight the robust activity of phosphates, which act synergistically with fluorides, controlling the degradation of F-coating in biological media and prolonging the service period of temporary Mg(PM)F implants.► Phosphates hinder the corrosion of Mg by chlorides and reduce its degradation rate. ► The service period of F-treated Mg implants may be extended by phosphates. ► F- treated Mg reinforced by powder metallurgy is a promising biomaterial.

Materials Science and …, Jan 1, 2011

The development of a biodegradable metallic implant demands a precisely defined degradation profi... more The development of a biodegradable metallic implant demands a precisely defined degradation profile and adequate mechanical properties. Mg has been proposed for this purpose but it has an excessively high corrosion rate and insufficient yield strength. In the present work pure Mg mechanically reinforced by a powder metallurgy (Mg(PM)) route and treated with KF was used. The effect of chlorides, at the physiological level, on four fluoride conversion coatings (F-CC) formed on Mg(PM) was evaluated comparatively. The behavior of Mg(PM) during fluoride treatments (0.01 M-0.3 M fluoride-containing solutions) before and after the addition of chlorides (8 g L -1 NaCl) was investigated by conventional corrosion techniques and by scanning electrochemical microscopy (SECM) complemented with SEM observations and EDX analysis. Results showed that the composition and the microstructural characteristics of the F-CCs as well as their corrosion behavior change with KF concentration and immersion time. Treatments in the 0.01 M-0.1M KF range prove to be effective to protect Mg(PM) against corrosion in the absence of chlorides while higher KF solution concentration (0.3 M) adversely affects the corrosion resistance of this metal. In the presence of chloride ions the F-CCs progressively lose their fluoride content and their corrosion resistance at a rate that depends on the treatment conditions. Such temporary corrosion protection is appropriate for biodegradable implants.

Biosensors & Bioelectronics, Jan 1, 2010

The design and characterization of a lactate biosensor using a nanostructured rough gold surface ... more The design and characterization of a lactate biosensor using a nanostructured rough gold surface as a transducer is reported. The biosensor is developed by immobilization of lactate oxidase (LOx), on a rough gold electrode modified with a self-assembled monolayer of dithiobis-N-succinimidyl propionate (DTSP). This bifunctional reagent preserves the rough gold structure and allows further covalent immobilization of the enzyme through the terminal succinimidyl groups. The rough gold electrode is characterized using field emission scanning electron microscopy (FE-SEM) and atomic force microscopy (AFM). The preferential orientation and average crystallite size are obtained by X-ray diffraction (XRD). The resulting lactate oxidase monolayers are characterized by electrochemical impedance spectroscopy (EIS). This nanostructured transducer allows higher mediated electrocatalytic activity than polycrystalline ones. The biosensor response to increasing lactate concentrations, using hydroxymethylferrocene as a redox mediator in solution, is linear up to 1.2 mM with a sensitivity of 1.49 μA mM−1.

Journal of applied electrochemistry, Jan 1, 2010

A study has been performed to select optimum process conditions (temperature, pH, reagent concent... more A study has been performed to select optimum process conditions (temperature, pH, reagent concentration, reaction kinetics, deposition time, etc.) in gold deposition on Si(n) from sulphite/thiosulphate electrolytic baths. Gold deposits have been obtained by electrochemical techniques such as constant potential, constant current, cyclic voltammetry and pulsating overpotential, in diffusional regime or by charge transfer control, at two pH values (6 and 9) and two temperatures (30 and 50 °C). The surface morphology of the Au deposits was studied by scanning electron microscopy (SEM), the preferred orientation and average size of the Au electrodeposited particles on n-Si substrates were obtained by X-ray diffraction (XRD), and qualitative and semiquantitative analysis of the gold sample was performed by energy dispersive X-ray (EDX) and X-ray photoelectron spectroscopy (XPS). The surface sulphur content was much lower or almost zero for gold samples obtained at pH 9 compared to those obtained at pH 6. However, when the different methods were compared at pH 6, both cyclic voltammetry and pulsating overpotential deposition led to deposits with a low or zero sulphur content. The results also show that various morphologies with different grain sizes can be obtained without the addition of additives.