Further applications of a new biosensor method for dating cellulosic finds

Using a cellulosic material dating method recently proposed by three of the authors of the present article further applications to real samples are discussed. In the first instance, to wood samples, that is, to a type of sample for which the method was specifically developed but with the samples differing widely in age, and then to textile or paper samples. Of course in the latter two cases the results obtained are still quite preliminary, above all because of the difficulty of procuring certainly dated samples of this type.

Analysis of an anxiolytic technique applied in 1179 patients undergoing oral surgery

AIM

The aim of this study was to evaluate the effects of sedation with benzodiazepines in a large population of patients undergoing oral surgery and age-related implications.

METHODS

A group of 1 179 consecutive patients undergoing oral surgery in the Dental Clinic of the University of Padua between 2001 and 2003 was evaluated by analysing their anaesthesiological records. The patients were divided into 5 age groups. All were pre-sedated with chlordemethyldiazepam per os, while induction of maximum subjective tranquillity was obtained with fractionated doses of intravenous diazepam. Arterial pressure (AP), heart rate (HR), anxiety level, pathologies, drugs taken, types of intervention, techniques of loco-regional anaesthesia, immediately preoperative AP and HR and tranquillity, intraoperative AP and HR, data regarding postoperative psychomotor recovery, complications and drugs used for the treatment of perioperative pain, were evaluated in each group.

RESULTS

Most of the patients (679) were in the 45-64 year-old group. Cardiovascular, respiratory and digestive pathologies proved to be age-dependent. Control AP and HR respectively increased and decreased with age. The doses of chlordemethyldiazepam used induced age-dependent preoperative tranquillity levels. The doses of i.v. diazepam necessary to obtain maximal preoperative subjective tranquillity fell as a function of age. The AP and HR values respectively increased during intervention and decreased in the first hour of intervention. Normal psychomotor recovery was less evident in older patients. The most significant corrective intraoperative interventions consisted of the administration of sublingual hypotensive drugs and in the immediate treatment of some cases of orthostatic hypotension and vaso-vagal syncope.

CONCLUSIONS

The sedation technique and the antistress procedures employed proved safe and the intra- or postoperative complications almost non-existent. The variations observed in the parameters considered are compatible with the greater age of the treated subjects.

Comparison of fluorimetric, voltammetric and biosensor methods for the determination of total antioxidant capacity of drug products containing acetylsalicylic acid

Antioxidant capacity of several drug specialities containing as mean component acetylsalicylic acid were experimentally evaluated using an enzymatic electrode, recently developed by the present authors, based on superoxide dismutase (SOD) enzyme. The precision of this method of analysis was found to be good (for drug samples RSD < or = 5%). The results were also compared with those ones by a traditional spectrofluorimetric method and by two other methods, respectively, based on cyclic and pulsed voltammetry, recently trialled by the present authors.

Determination of hydrogen peroxide in disinfectant solutions using a biosensor with two antagonist enzymes

The development and characterisation of a new biosensor for hydroperoxides is described, which is obtained by combining an oxygen gas diffusion amperometric electrode and two immobilized enzymes (peroxidase and tyrosinase) working in parallel and competing for the same substrate (catechol). The response of the biosensor to several hydroperoxides was investigated (LOD=0.5.10(-4) M for hydrogen peroxide). It was experimentally found that the biosensor is able to respond also to aqueous solutions of ionic peroxides (LOD=0.2.10(-4) M for potassium peroxidisulphate). The biosensor was applied to the determination of the hydrogen peroxide content of pharmaceutical products, i.e. aqueous disinfectant solutions (RSD% < or =0.5; recoveries by standard addition method between 96.0 and 98.5%).

Determination of antioxidant properties of aromatic herbs, olives and fresh fruit using an enzymatic sensor

The aim was to experimentally evaluate the antioxidant capacity of different fresh aromatic herbs (field balm, marjoram, parsley, rosemary, sage, sweet basil), several varieties of olives from Central Italy ('Carboncello', 'Rosciolo', 'Olivastro', 'Coratello', 'Leccino', 'Frantoio') and several types of fresh fruit (apple, apricot, banana, cherry, fig, grape, medlar, melon, peach, pear, pineapple, plum, water melon, yellow plum) using a superoxide dismutase (SOD) biosensor developed by the present authors. Measurements were carried out by comparing the biosensor response to the concentration of superoxide radical produced in solution using a xanthine/xanthine oxidase system in the presence and absence of the antioxidant sample considered. Tests carried out on different samples of fruit and aromatic herbs showed that the homogenised samples had better antioxidant properties than the centrifuged ones (obtained by centrifuging the homogenate), which sometimes gave extremely low antioxidant capacity values. The reliability of the proposed method was checked by comparing the trend of some experimental results found using the SOD biosensor with those reported in the literature obtained using the classic (ORAC) method. The precision of this method of analysis was found to be good for samples of aromatic herbs (RSD% <or=8%), acceptable for homogenised fruit samples (RSD% <or=13%) and less good for homogenised and centrifuged samples (RSD% <or=20%).

Two OPEEs (organic phase enzyme electrodes) used to check the percentage water content in hydrophobic foods and drugs

The development and optimization of an analytical method using enzymatic biosensors able to operate in organic solvents [organic phase enzyme electrodes (OPEEs)] for the determination of the water content in food fats (butter, margarine) or pharmaceutical or cosmetic ointments is described. The method is based on the increase in enzymatic activity which is related to the increase in the percentage water content in the organic phase into which the biosensor is dipped. The enzymes used to assemble the biosensors were tyrosinase or catalase, the substrates were phenol or p-cresol and tert-butyl hydroperoxide, respectively, and the organic solvents were acetonitrile or dioxane. A gas diffusion amperometric electrode for oxygen measurement was used as electrochemical transducer. The results were compared with those obtained applying the Karl Fischer method to the same food or drug matrices. The correlations among the two methods proved satisfactory, as the difference in the computed values of water content was never higher than 7%. Also, the precision of measurements was acceptable (RSD < 6%) in all the analyses of real matrices.

Superoxide dismutase biosensors working in non-aqueous solvent

Enzymatic electrodes based on superoxide dismutase enzyme were developed. Using the superoxide dismutase enzyme sensor assembled according to the classical model, poor results were obtained. Results were improved by adopting a new way of assembling the biosensor using a cellulose triacetate layer in which the SOD enzyme is entrapped and sandwiched between two gas-permeable membranes, or using a kappa-carrageenan gel layer entrapping the enzyme, sandwiched between an external gas permeable membrane and an internal cellulose acetate membrane, coupled in each case to the oxygen amperometric transducer. Results obtained by applying the newly developed biosensor to assaying hydrophobic compounds showing radical scavenging properties, operating in dimethylsulfoxide, were also satisfactory.

Evaluation of radical scavenging properties of several plants, fresh or from a herbalist's, using a superoxide dismutase biosensor

The experimental evaluation of properties of defence against free radicals represents an extremely interesting heuristic and applicational objective. Research was carried out to experimentally evaluate the scavenging properties of several fruits and plants, fresh or from a herbalist's using an amperometric superoxide dismutase (SOD) biosensor recently developed by the present authors. The superoxide radical was produced in solution using the xanthine/xanthine oxidase system; measurements were carried out by comparing biosensor response to superoxide radical both in the presence and absence of the sample considered.

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.

Toxicity order of cholanic acids using an immobilised cell biosensor

There is considerable published evidence of the use of cells of various species to evaluate the toxicity of numerous compounds, many of pharmaceutical interest. The coupling of cell colonies with a suitable transduction device has led to the development in recent years of toxicity biosensors based on the alteration of a process or a cell metabolic function by the toxic substance under examination. A biosensor based on immobilised yeast cells (Saccharomyces cerevisiae) has been developed recently in this department for the purpose of performing a rapid toxicity test in aqueous environmental matrices. This biosensor has now been used in the toxicity screening of a number of sodium salts of conjugated and free cholanic acids. The "toxicity degree" scale, which was found by placing in decreasing order the values of the slopes of the straight lines obtained by quantifying changes in the behaviour of the respirometric curve, plotted before and after incubation, using known concentrations of cholanic acid sodium salts, was: deoxycholic acid > chenodeoxycholic acid > ursodeoxycholic acid > cholic acid, for free cholanic acids; and glycodeoxycholic acid > glycochenodeoxycholic acid > glycocholic acid, for glycocholanic acids. These values are in good agreement with published toxicity data obtained in vitro. This sensor can thus be considered to provide a valid instrument for the preliminary evaluation of the toxicity of organic compounds or drugs.

Immobilised yeast cells biosensor for total toxicity testing

An immobilised yeast cell biosensor has been developed for the total toxicity testing of a sample that may contain a number of different pollutant species; the biosensor uses an amperometric gas diffusion oxygen as indicator electrode. The method is based on the perturbation of the respiratory activity of a yeast, Saccharomyces cerevisiae, immobilised on an agar gel containing the culture medium (i.e., 'agarised medium'), by the toxic test substance. Glucose is used as substrate while the toxic substances tested consist of several metallic ions, phenol and cationic or anionic surfactants.