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Biomedical subjects

E López-Cabarcos

Publications and source records attributed to E López-Cabarcos.

10 recordsLinked to original sources
PubMed2006

The application of methacrylate-based polymers to enzyme biosensors.

Enzyme electrodes based on methacrylates have received significant attention in the development of biosensors. This article reviews the use and application of methacrylate and its derivatives as an immobilization system for the preparation of enzyme electrodes. Resent examples, extracted from the literature, illustrate the superior performance of such materials in the fabrication of biosensors and bioreactors.

Biocompatible Materials↗
PubMed2006

Amperometric tyrosinase biosensor based on polyacrylamide microgels.

An amperometric enzyme sensor using tyrosinase (PPO) entrapped in polyacrylamide microgels has been developed for determination of phenolic compounds. Polyacrylamide microgels were obtained by the concentrated emulsion polymerization method. The crosslinking of the polymer matrix optimum to retain the enzyme and to allow the diffusion of the compounds involved in the enzyme reaction has been studied (4.0%) as well as the influence on the response of analytical parameters such as pH, temperature, enzyme load and working potential. The useful lifetime of the biosensor was 27 days and it was useful to determine monophenolics compounds (e.g. cresol, chlorophenol) and diphenolics compounds (e.g. catechol and dopamine) by amperometric measurements at -100mV (versus SCE) in a batch system. The results showed that the substrate structures have a great influence on the sensor response.

Acrylic Resins↗
PubMed2006

Organic phase enzyme electrodes.

In the development of biosensors, organic phase enzyme electrodes (OPEEs) have received considerable attention for the detection of substrates in organic media. This article reviews different enzymes, transductors and immobilization methods used for the preparation of OPEEs in the last decade.

Biosensing Techniques↗
PubMed2006

Amperometric glucose biosensor based on polymerized ionic liquid microparticles.

A glucose amperometric biosensor based on the immobilization of glucose oxidase (GOx) in microparticles prepared by polymerization of the ionic liquid 1-vinyl-3-ethyl-imidazolium bromide (ViEtIm+ Br-) using the concentrated emulsion polymerization method has been developed. The polymerization of the emulsion dispersed phase, in which the enzyme was dissolved together with the ionic liquid monomer, provides poly(ViEtIm+ Br-) microparticles with entrapped GOx. An anion-exchange reaction was carried out for synthesizing new microparticles of poly(ViEtIm+ (CF3SO2)2N-) and poly(ViEtIm+ BF4-). The enzyme immobilization method was optimized for biosensor applications and the following optimal values were determined: pH 4.0 for the synthesis medium, 1.23 M monomer concentration and 3.2% (w/w) cross-linking content. The performance of the biosensor as a function of some analytical parameters such as pH and temperature of the measuring medium, and enzymatic load of the microparticles was also investigated. The effect of the substances which are present in serum samples such as uric and ascorbic acid was eliminated by using a thin Nafion layer covering the electrode surface. The biosensor thus prepared can be employed in aqueous and in non-aqueous media with satisfactory results for glucose determination in human serum samples. The useful lifetime of this biosensor was 150 days.

Biosensing Techniques↗
PubMed2005

Biosensors based on acrylic microgels: a comparative study of immobilized glucose oxidase and tyrosinase.

Acrylic microgels are proposed as enzyme immobilizing support in amperometric biosensors. Two enzymes, glucose oxidase and tyrosinase, were entrapped in this matrix and their behaviour is compared. The optimum cross-linking of the polymeric matrix required to retain the enzyme, and to allow the diffusion of the substrate is different for each enzyme, 3.2% for glucose oxidase and 4.5% for tyrosinase. The effect of pH and temperature on the biosensor responses has been studied by experimental design methodology and predictions have been compared with independently performed experimental measurements. A quadratic effect of the variables studied (pH and T) on the biosensor response and the small or null interaction between them was confirmed. The pH results obtained with both methods are coincident revealing an reversible effect on the enzyme. However, the temperature optimum value obtained by experimental design was 10 degrees C lower as a result of an activity decay due to irreversible thermal denaturation of both enzymes.

Acrylic Resins↗
PubMed2002

Structural modifications in the swelling of inhomogeneous microgels by light and neutron scattering.

Small-angle neutron scattering and dynamic light scattering have been used to study the thermodynamics of swelling and the associated structure modifications of highly cross-linked temperature-sensitive poly (N-isopropylacrylamide) [poly(NIPAM)] microgels in D2O. A particle core-shell model is proposed, with the core containing most of the cross-linker molecules. The Flory-Rehner theory, with the inclusion of a concentration dependent Flory solvency parameter, successfully describes the experimental swelling, despite the inhomogeneous character of the particles. Interestingly, the shell evolution with temperature controls the whole particle swelling, exerting an external pressure over the core, which in turn influences its size during the swelling process. Scaling laws for the correlation lengths were found with respect to temperature and polymer concentration. Finally, it has been encountered that for the collapsed microgel states, the particle surface seems to have a fractal character.

Journal Article↗
PubMedDate not supplied

Changes in the flow properties of phospholipid dispersions induced by procaine hydrochloride. Effect of pH and temperature.

Since local anaesthetics are known to interact with membrane lipids, we have examined the changes taken place by procaine hydrochloride in lipid matrices as a function of pH. Rheological methods might give useful information on the association of this anaesthetic with soybean lecithin. The procaine interacted with negatively charged phospholipid polar head groups at pH 4. This system exhibits a loosening in the tight arrangement of phospholipid molecules caused by the addition of procaine as a function of this anaesthetic's concentration. The flow enthalpy values as a function of procaine-lipid ratio shows biphasic behaviour and suggests a phase transition when the anaesthetic concentration goes from 10 to 14 mM and temperatures dip below 10 degrees C.

Chemical Phenomena↗
PubMedDate not supplied

Mucopolysaccharides in aqueous solutions: effect of ionic strength on titration curves.

We study the changes taking place in hyaluronic acid, chondroitin 4-sulfate (C4-S) and condroitin 6-sulfate (C6-S), at ionic strengths of 0.10, 0.15, and 0.20 in NaCl, in a neutralization process in aqueous solution. We apply the equation of Henderson Hasselbalch modified for polyelectrolytes and evaluate the changes in the electrostatic free energy starting from the pK curves as a function of the dissociation degree. For a dissociation degree next to 0.4 corresponding to the -COOH group of the hyaluronic acid, we observed a change in the conformation of the three glycosaminoglycans studied. This conformational change takes place as a consequence of the break of intramolecular links and the beginning of the ionization process. The macromolecules in solution show a structure of random coil sufficiently expanded so that the interaction among the close ionizable groups is negligible.

Algorithms↗