M. Tomassetti

Biosensors for determination of total and natural antioxidant capacity of red and white wines: comparison with other spectrophotometric and fluorimetric methods

Research was carried out to experimentally evaluate the antioxidant capacity of several red and white wines using a superoxide dismutase (SOD) biosensor recently developed by the present authors. Measurements were performed by comparing the biosensor response to increasing concentration of the superoxide radical produced in solution by the xanthine/xanthine oxidase system, both in the presence and absence of the test sample.The results were compared with those of two traditional spectrophotometric methods and of a spectrofluorimetric method described in literature.Lastly, also the polyphenol, sulfite and ascorbic acid contents of the different wine samples examined were measured using a tyrosinase biosensor, a sulfite oxidase biosensor and an ascorbate oxidase biosensor, respectively.

Hydrogen peroxide determination in pharmaceutical formulations and cosmetics using a new catalase biosensor.

The possibility of evaluating the content of hydrogen peroxide in several authentic matrices, such as cosmetic and pharmaceutical formulations, was studied. A new catalase biosensor fabricated using an amperometric gas-diffusion oxygen sensor as electrochemical transducer and the catalase enzyme immobilized in kappa-carrageenan gel and capable of operating in both aqueous and non aqueous solvents was developed and tested for this purpose. Creams, emulsions and disinfectant solutions were analysed. To this end, a preliminary check was needed to establish the best conditions to analyse these matrices; the choice of solvent was one of the most important points studied. The solvents considered included dioxane, water-dioxane mixtures, water saturated chloroform and aqueous solutions. The different solubility properties of the matrices analysed were taken into account.

New biosensor for superoxide radical used to evidence molecules of biomedical and pharmaceutical interest having radical scavenging properties

A superoxide dismutase biosensor was used to determine the antioxidant properties of scavenger molecules and the antiradical activity of healthy and diseased human kidney tissues; this biosensor is based on the use of the enzyme superoxide dismutase (SOD), which is physically entrapped in a kappa-carrageenan gel membrane, and of a transducer consisting of an amperometric hydrogen peroxide electrode. Several compounds with scavenging properties were tested, including some commercial drugs.

The effect of organic solvent properties on the response of a tyrosinase enzyme sensor

The use of an enzyme tyrosinase sensor capable of being employed in non aqueous media represents a good opportunity to investigate the effects of the organic solvent on enzyme activity. Six different solvents are considered (n-heptane, n-hexane, n-pentane, toluene, chloroform, acetonitrile) and two properties of these solvents are studied in particular, i.e. hydrophobicity (as log P) and dielectric constant, taking into account their influence on sensor response. Results are generally in agreement with those found by other authors, who determined the behaviour of the enzyme activity as a function of organic solvents using different methods.

Butyrylcholine enzyme sensor for determining organophosphorus inhibitors

Abstract Esterase enzymes play an important role in biology because they are responsible for the hydrolysis of acetylcholine and because, in their absence, (or if their activity is inhibited), the original state of the postsynaptic membranes cannot be re-established. It is therefore of interest to study the inhibiting action exerted by some compounds on this class of enzymes. Among them, pesticides are important because of the potential danger as a result of their large-scale use in agriculture. The behavior of the esterase/pesticide systems, and the analytical possibilities arising from the inhibiting action exerted by pesticides on esterases were examined. Along these guide lines, a biosensor for the determination of pesticides did finally result. This biosensor consists of a Clark oxygen electrode, modified with a dialysis membrane placed over it containing two immobilized biological mediators: butyryl- or acetyl-cholinesterase and choline oxidase. Its application to the analysis of ecologically important matrices is described. A comparison with the results obtained by a similar, previously published procedure, characterized by butyryl- (or acetyl-)cholinesterase free in solution, is also reported.

Determination of phenol in wastes and water using an enzyme sensor

Biosensors for the determination of phenol in real matrices such as oil press and industrial wastes and sea-, lake and river waters are proposed. Optimization of the experimental parameters, especially regarding enzyme immobilization, was performed. The biosensors are based on a Clark oxygen electrode coupled with tyrosinase immobilized by three different methods. Biosensors were also tested in order to verify whether their direct use with environmental samples and in in situ analysis is possible.

New amperometric and potentiometric immunosensors for anti-human immunoglobulin G determinations

Two new electrochemical immunosensors for the determination of antibodies such as anti-human immunoglobulin G (anti-HIgG) were fabricated and characterized. The two immunosensors investigated made use of two different types of electrochemical transducer: an amperometric electrode for H2O2 determination and a gaseous diffusion potentiometric electrode for NH3 determination. The development of these immunosensors involved the immobilization of human immunoglobulin G (HIgG) on a polymeric membrane located on the electrode head. Furthermore, two different enzymes were used as markers, thus allowing two different anti-HIgG conjugates with urease and glucose oxidase, respectively, to be obtained. Two different polymeric membranes on which the HIgG were immobilized, namely ‘Pall-Biodyne’ and ‘Immobilon’, were also employed. A method for re-utilizing the membrane of the immunosensor in which the conjugate was immobilized was also optimized.

Biosensor for direct determination of glucose and lactate in undiluted biological fluids.

This paper describes the implementation of a bienzyme sensor for the direct determination of glucose and lactate in undiluted biological samples. The biosensor exploits the competitive action versus the substrate itself by two different enzymes immobilized into a sandwich of two different membranes. In this way the quantity of substrate reaching the indicating electrode is reduced and this determines an extension of the linearity range.

Determination of choline-containing phospholipids in human bile and serum by a new enzyme sensor

A simple method for direct determination both of choline and lecithin (phosphatidylcholine) in human bile and blood sera was developed. An enzyme electrode, based on immobilized choline oxidase on nylon net and an oxygen Clark electrode was assembled. Phosphatidylcholine can be determined by use of phospholipase D as hydrolyzing agent. Reliable results were obtained in the case of determination of lecithin and choline in bile samples.

Tyrosinase biosensor response as a function of physical properties of organic solvents.

The main aim was to investigate the possibility of developing a fast, easily produced biosensor capable of being used in non-aqueous solvents such as n-hexane, chloroform, mixtures thereof and water-saturated chloroform. The research also provided an experimental confirmation of several concepts, described in the literature, concerning enzymatic activity in different types of non-aqueous solvents. The results are decidedly encouraging as regards future possible uses of this sensor to determine soluble substances in non-aqueous solvents.