Biomedical subjects

D Compagnone

Publications and source records attributed to D Compagnone.

At least 19 recordsLinked to original sources

PubMed2007

NADH screen-printed electrodes modified with zirconium phosphate, Meldola blue, and Reinecke salt. Application to the detection of glycerol by FIA.

Bulk screen-printed electrodes (bSPEs) modified with zirconium phosphate (ZrP) and Meldola blue (MB) and by electrochemical deposition of a Reineckate film (bMBZrPRs-SPEs) have been constructed and used as NADH sensors. Cyclic voltammetric investigation of these bulk electrochemically modified screen-printed electrodes revealed stable catalytic activity in oxidation of the reduced form of the coenzyme nicotinamide adenine dinucleotide (NADH). Flow-injection analysis (FIA) coupled with amperometric detection confirmed the improved stability of the bMBZrPRs-SPEs (10(-4) mol L(-1) NADH, %RSD = 4.2, n = 90, pH 7.0). Other conditions, for example applied working potential (+50 mV relative to Ag|AgCl), flow rate (0.30 mL min(-1)) and pH-dependence (range 4.0-10.0) were evaluated and optimized. A glycerol biosensor, prepared by immobilizing glycerol dehydrogenase (GDH) on the working electrode area of a bMBZrPRs-SPE, was also assembled. The biosensor was most stable at pH 8.5 (%RSD = 5.6, n = 70, 0.25 mmol L(-1) glycerol). The detection and quantification limits were 2.8 x 10(-6) and 9.4 x 10(-6) mol L(-1), respectively, and the linear working range was between 1.0 x 10(-5) and 1.0 x 10(-4) mol L(-1). To assess the effect of interferences, and recovery by the probe we analyzed samples taken during fermentation of chemically defined grape juice medium and compared the results with those obtained by HPLC.

Beverages↗

PubMed2006

An electrochemical bioassay for dichlorvos analysis in durum wheat samples.

The use of an acetylcholinesterase inhibition assay for the detection of dichlorvos in durum wheat samples by a simplified extraction procedure is reported. After an incubation step, the residual activity was determined with an amperometric biosensor using a portable potentiostat. The use of electric eel and recombinant acetylcholinesterase was compared. The effect of the matrix extract was evaluated by using various sample:solvent ratios, 1:2.5, 1:5, 1:10, and 1:20. The optimal extraction ratio, considering the electrochemical interferences and the effect on enzyme activity and bioavailability of the pesticide, was 1:10. Calibrations were performed in buffer and durum wheat extract. The calculated detection limits in buffer solution were 10 ng/ ml and 0.045 ng/ml for electric eel and recombinant acetylcholinesterase, respectively, whereas operating in the matrix extract they increased up to 45 ng/ml and 0.07 ng/ml, corresponding to 0.45 mg/kg (extraction ratio 1:10) and 0.07 mg/kg in samples. These characteristics allowed the detection of contaminated samples at the maximum residue limit, which is 2 mg/kg and well below. Fortified samples of durum wheat were obtained with both dichlorvos and the commercial product Didivane, which contains dichlorvos as an active molecule. At all the tested levels, the occurrence of contaminant was detected with an average recovery of 75%. The total assay time, including the extraction step, was 30 min. Because several extractions as well as most of the assay steps can be run simultaneously, the throughput for one operator is 12 determinations per hour.

Acetylcholinesterase↗

PubMed2005

Evaluation of the antioxidant capacity of individual phenolic compounds in virgin olive oil.

Virgin olive oil has a high resistance to oxidative deterioration due to its tryacylglycerol composition low in polyunsaturated fatty acids and due to the presence of a group of phenolic antioxidants composed mainly of polyphenols and tocopherols. We isolated several phenolic compounds of extra virgin olive oil (phenyl-ethyl alcohols, lignans, and secoiridoids) by semipreparative high-performance liquid chromatography (HPLC) and identified them using ultraviolet, atmospheric pressure chemical ionization, and electrospray ionization MS detection. The purity of these extracts was confirmed by analytical HPLC using two different gradients. Finally, the antioxidant capacity of the isolated compounds was evaluated by measuring the radical scavenging effect on 1,1-diphenyl-2-picrylhydrazyl radical, by accelerated oxidation in a lipid model system (OSI, oxidative stability instrument), and by an electrochemical method.

Antioxidants↗

PubMed2004

Piezoelectric sensors for dioxins: a biomimetic approach.

The aim of this work was to design a fast, cheap and easy to use analytical system for dioxins. Piezoelectric sensors coupled with the pentapeptides as biomimetic traps (the receptors), selective for the dioxins, were used for the realisation of this analytical system. A methodology to select specific receptors among all possible pentapeptides randomly generated was represented by the use of molecular modelling software. Three peptides called later on A, B and C (A:[N]Asn-Phe-Gln-Gly-Ile[C]; B:[N]Asn-Phe-Gln-Gly-Gln[C]; C:[N]Asn-Phe-Gln-Gly-Phe[C]), were selected and evaluated for their potential usage as artificial receptors in solid-gas analysis by using a quartz crystal microbalance (QCM) sensors array. The peptide sequences were functionalised by two terminal cysteine residues in order to achieve a covalent interaction with the QCM gold surface. A manganese-porphyrin complex and two other pentapeptides, a pentaglutamine (pentapeptide D) and a pentalysine (pentapeptide E), were used as negative control sensors. The QCM sensors (A, B and C) gave a good linearity against different sample concentrations of the 2,3,7,8-tetrachlorinated dibenzo-p-dioxin (TCDD) and a mixture of dioxins. In particular, the selectivity against 2,3,7,8-TCDD was nicely correlated to the estimated binding energy of the receptors calculated by computational modelling. The cross-reactivity of the system was quantified using commercial polychlorinated biphenyls (PCBs) mixtures (dioxin-like compounds).

Biomimetics↗

PubMed2004

Contribution of the phenolic fraction to the antioxidant activity and oxidative stability of olive oil.

Antioxidant activity of the phenolic fraction of extra virgin olive oil (EVOO) was measured by means of a chemical and an electrochemical method. Both methods were tested in predicting the oxidative spoilage and stability to oxidation of 22 EVOO samples and resulted correlated with peroxide values and oxidative stability measured by Rancimat. The main phenolic compounds of EVOOs were detected by HRGC. To study the contribution of single polyphenols (PPs) to antioxidant activity of phenolic fraction and oxidative stability of EVOOs, multivariate statistical analyses were applied on HRGC data. An isomer of oleuropein aglycon was shown to affect significantly antioxidant activity of phenolic fraction but not oil stability to oxidation. No individual compounds was identified as the main cause of the overall antioxidant activity, and the total polyphenol determination by the Folin reagent was better correlated to antioxidant activity and oxidative stability than each tested PP or PPs groups such as o-diphenols.

Antioxidants↗

PubMed2002

An electrochemical ELISA procedure for the screening of 17beta-estradiol in urban waste waters.

A sensitive electrochemical enzyme-linked immunosorbent assay (ELISA) has been used for the detection of 17beta-estradiol in waste waters. The activity of the label enzyme (horseradish peroxidase) was measured electrochemically using 3,3',5,5'-tetramethylbenzidine as electrochemical substrate. The detection limit was estimated to be 5 pg mL(-1), interday and intraday precision (RSD), ranged from 1 to 3% and from 3 to 6%, respectively. Analysis of waste waters from three different treatment plants demonstrated no matrix effect both for samples diluted 1:1 in buffer and diethyl ether extracted. Data on 36 samples analysed by an LC-ESI-MS-MS procedure and by the electrochemical ELISA assay were compared. Results correlated well. The electrochemical enzyme immunoassay appears suitable as a screening tool for analysis of estradiol in waste waters.

Electrochemistry↗

PubMed2001

Construction and analytical characterization of Prussian-Blue-based carbon paste electrodes and their assembly as oxidase enzyme sensors.

This paper reports on the development and characterization of Prussian Blue-modified carbon paste electrodes. New methods of matrix modification with Prussian Blue are reported. Two different carbon pastes have been prepared, using mineral oil or solid paraffin, thus obtaining different types of sensors whose behavior toward the electrochemical reduction of hydrogen peroxide has been fully characterized. Results obtained with Prussian Blue-modified electrodes showed a long operational lifetime, an excellent stability in a wide range of pH (3-9), a high sensitivity, and a fast response time. In addition, the coupling of solid carbon paste modified with Prussian Blue and the enzymes glucose oxidase and choline oxidase led to the assembling of biosensors that showed an optimum working range at alkaline pH.

Journal Article↗

PubMed2001

Immunodetection of lactosylated proteins as a useful tool to determine heat treatment in milk samples.

This paper reports the optimisation of a competitive immunoassay (ELISA) to detect lactosylated proteins in milk samples. The assay employs monoclonal antibodies for lactosylated proteins produced in our laboratory and requires no pre-treatment of the samples other than a dilution step. Monoclonal antibodies were fully characterised in terms of selectivity and cross-reactivity with structurally related molecules and used in a competitive assay format with lactosylated standard proteins (lactosylated ovalbumin). The detection limit for lactosylated ovalbumin was 0.015 microgram ml-1 and the working range was from 0.010 to 40 micrograms ml-1. The data obtained indicate that the ELISA developed is applicable to diluted milk samples and is able to distinguish between milk samples that have undergone different heat treatments (UHT and pasteurised milk).

Animals↗

PubMed2000

Rapid assay of choline in foods using microwave hydrolysis and a choline biosensor.

A fast procedure for the determination of choline in food was developed by coupling a microwave hydrolysis procedure with an O(2)/choline oxidase-based electrochemical biosensor. Time and temperature were varied to select the best conditions for the microwave hydrolysis. Results have been compared with those found by the traditional method, constituted by hydrolysis at 70 degrees C followed by enzymatic-colorimetric assay. Data obtained by the biosensor method correlated well with the enzymatic-colorimetric assay (R(2) = 0.998). Microwave versus traditional hydrolysis gave a good correlation both with the colorimetric and with biosensor procedures with a relative error below 6%. The method is sensitive and selective enough to be used for a wide variety of food items reducing remarkably the analysis time.

Biosensing Techniques↗

PubMed2000

Evaluation of the effects of fixed combinations of sustained-release verapamil/trandolapril versus captopril/hydrochlorothiazide on metabolic and electrolyte parameters in patients with essential hypertension.

The objective of this randomised open, active controlled, cross-over study was to evaluate the effect of a fixed combination of verapamil SR/trandolapril compared to captopril/hydrochlorothiazide on serum lipids, lipoproteins, and other metabolic and electrolyte parameters in patients with essential hypertension. Another objective was to assess the efficacy and safety of both combinations. One hundred hypertensives with systolic blood pressure 140-209 mm Hg and diastolic blood pressure 90-119 mm Hg were evaluated after 16 weeks receiving a fixed combination of verapamil SR 180 mg/ trandolapril 2 mg (VT) or captopril 50 mg/hydro- chlorothiazide 25 mg (CH) both given once daily. Lipids and lipoproteins were assessed in duplicate on 2 consecutive days. The study was completed by 80 patients. There was no statistically significant difference between the two combined regimens with respect to low-density lipoprotein (LDL)-cholesterol for the 'intention-to-treat' population measured at the end of each treatment period (3.44 +/- 0.87 mmol/L with VT, and 3.46 +/- 0.86 mmol/L with CH). No differences were found for other lipid parameters like total cholesterol, triglycerides, apolipoproteins A1 and B, Lp(a). High-density lipoprotein (HDL)-cholesterol was significantly higher with VT (1.39 +/- 0.01 vs 1.35 +/- 0.01, P < 0. 03). Serum potassium declined while uric acid and glucose increased on CH. In conclusion, no significant differences were found in LDL-cholesterol and in other lipid parameters with the exception of HDL-cholesterol which was significantly higher on VT. Serum potassium declined while uric acid and glucose increased on CH (all significantly). Both fixed combinations were well tolerated. The incidence of adverse events was higher on CH. Both fixed combinations significantly lowered BP. Journal of Human Hypertension (2000) 14, 347-354

Adolescent↗

PubMed2000

Development of an electrochemical ELISA for the screening of 17 beta-estradiol and application to bovine serum.

A sensitive electrochemical enzyme-linked immunosorbent assay (ELISA) for the detection of 17 beta-estradiol (17 beta-E2) was developed. Optimisation of two ELISA competition assays, using monoclonal or polyclonal antibodies anti-17 beta-estradiol, coupled with the electrochemical detection was firstly performed. The activity of the label enzyme (horseradish peroxidase) was measured electrochemically using 3,3',5,5'-tetramethylbenzidine as substrate. The use of the polyclonal antibody resulted in a more sensitive assay and the detection limit of the assay was estimated to be 20 pg ml-1. The analytical performances of the method were compared to those obtained using a dissociation enhanced lanthanide fluorescence immunoassay (DELFIA). Although sample extraction is not usually required by DELFIA, both extracted and non extracted samples were assayed. The comparison between the two screening techniques revealed similar results for the extracted samples and showed a comparable precision (RSD%), ranging from 6.2 to 13.4 and from 6.7 to 14.3 for DELFIA and ELISA, respectively. The results obtained by these screening assays were confirmed by liquid chromatography atmospheric pressure chemical ionisation tandem mass spectrometry which is currently used to confirm illegal hormone administration for regulatory purposes. The electrochemical enzyme immunoassay appears suitable as a screening tool for routine analysis of bovine serum estradiol and can be extended to other anabolic hormones using appropriate antibodies.

Animals↗

PubMed1999

Flow injection analysis of mercury(II) in pharmaceuticals based on enzyme inhibition and biosensor detection.

An enzymatic amperometric procedure for measurement of mercury(II) in pharmaceuticals, based on the inhibition of invertase and on a glucose electrode was studied. Analytical parameters for measurements in batch and flow injection analysis (FIA) have been optimised. Mercury(II) was detected in the 10-60 ppb range with RSD < or =2%. A sample throughput of 6 h(-1) for batch and 15 h(-1) for FIA was obtained. The total mercury(II) from thimerosal (thiomersal, sodium ethylmercurithiosalicylate) in eye-drop samples was measured with the amperometric procedure after oxidative cleavage treatment. Results for both batch and FIA procedures correlated well with atomic absorbtion spectroscopy (AAS) data.

Biosensing Techniques↗

PubMed1999

Verapamil SR/trandolapril combination therapy for the elderly hypertensive patient. German VeraTran Hypertension Study Group.

A total of 254 elderly hypertensive patients (71 men and 183 women aged between 63 and 92 years, diastolic blood pressure (DBP) 95-115 mm Hg inclusive) were treated with the fixed combination of verapamil SR/trandolapril following a 4-week single-blind placebo run-in period. Treatment was started with a response dependent 3-step dose titration period. All patients were initiated at dose step 1 (verapamil SR/trandolapril 120/0.5 mg o.d.) and if not normalised (DBP <90 mm Hg) titrated at 4-weekly intervals over dose step 2 (verapamil SR/trandolapril 180/1 mg o.d.) to dose step 3 (verapamil SR/trandolapril 180/2 mg o.d.) during the first 12 weeks. After 3 months of treatment all patients not normalised were excluded from further participation in the study. The total duration of the treatment period was 6 months. Routine safety investigations were performed prior, during and on completion of the treatment period. Verapamil SR/trandolapril was highly effective in reducing blood pressure. At individual last visit during active treatment (also taking the non-responders into account), the mean reduction in SBP/DBP was 21.9/17.1 mm Hg (95% CI 19.8-24.1/16.1-18.1 mm Hg), with most of this reduction occurring during the first 3 months of treatment. After 6 months, 81.9% of the patients enrolled showed normalisation of DBP (<90 mm Hg) and 85% were responders (normalisation and/or reduction in DBP by at least 10 mm Hg). Normalisation and responder rates appeared to be comparable when stratified by age subgroups (63-69, 70-79 and > or =80 years) and were all greater than 80%. Verapamil SR/trandolapril was very well tolerated and there was no evidence of any clinically relevant changes in routine laboratory safety variables or resting ECG. In conclusion, the fixed dose combination of verapamil SR/trandolapril is an effective and safe alternative treatment for the elderly hypertensive patient.

Aged↗

PubMed1998

Development of a biosensor for monitoring of glycerol during alcoholic fermentation.

A biosensor for the measurement of glycerol in FIA was constructed using covalently immobilized glycerokinase and glycerol-3-phosphate oxidase in conjunction with a Pt based hydrogen peroxide probe. Different immobilization strategies have been studied including random and asymmetric immobilization onto a polymeric support and immobilization onto two different membranes. The latter resulted in the best configuration for batch measurement. The most effective configuration for measurement in FIA was the immobilization of glycerokinase in a glass beads reactor coupled with glycerol-3-phosphate oxidase on a preactivated Immobilon AV membrane kept at the electrode surface. Using a 250-microliter injection loop, 3 mmol ATP(Mg+2) in 0.1 M borate buffer pH 8.5 and a flow rate of 0.5 ml/min, a linear response in the 2 x 10(-6)/10(-3) mol/l range and a detection limit of 5 x 10(-7) mol/l were obtained for glycerol. Lifetime of the glycerol-3-phosphate membrane was extended up to 1 month by storage in the working buffer containing 1% DEAE-dextran and 5% lactitol. More than 350 samples can be assayed with this system. The biosensor was used to monitor off-line glycerol production during alcoholic fermentations carried out at different pHs and temperatures.

Biosensing Techniques↗

PubMed1998

Amperometric immunosensor for lactate dehydrogenase LD-1.

An amperometric immunosensor for the detection of the lactate dehydrogenase isoenzyme LD-1 has been developed. Polyclonal antibodies for LD-1 have been covalently immobilised onto a preactivated Immunodyne ABC membrane, reacted with standard LD-1 solutions and placed onto a platinum working electrode polarised at +600 mV vs. Ag/AgCl. Lactate dehydrogenase activity has been measured by detection of the oxidation of NADH at the electrode surface. A calibration curve for LDH in the 0.005-0.12 U range has been obtained with a repeatability of 3% and a reproducibility of 10%. The probe exhibited good selectivity (response of LD-2 was 18% of LD-1) which was further improved using thermal treatment of the membranes. Measurement of LD-1 content in human control serum with the developed procedure gave a LD-1 concentration in the reported assigned range.

Animals↗

PubMed1998

Verapamil SR and trandolapril combination therapy in hypertension--a clinical trial of factorial design. German Hypertension Study Group.

AIMS: To investigate the dose-response relationship and contribution of verapamil SR and trandolapril given in combination once a day for the treatment of essential hypertension. METHODS: A randomized, double-blind, placebo controlled, factorial, 12 arm parallel group comparison with placebo, verapamil SR (120, 180 mg), trandolapril (0.5, 1.0, 2.0 mg) covering all combinations of both drugs. A 4 week placebo run-in period followed by 6 weeks of treatment. Four hundred and fifty-six patients from office practice (22 centres) with mild to moderate hypertension enrolled and 426 with diastolic pressure > or = 100 mm Hg at the end of run-in period were randomized. Main outcome measures were reduction in sitting systolic (SBP) and sitting diastolic (DBP) blood pressure. RESULTS: The combination of verapamil SR and trandolapril, particularly verapamil SR 180 mg and trandolapril 0.5 or 1.0 mg was significantly superior to both monocomponents at the same dose (P<0.05). For these combinations, the adjusted mean reductions in DBP from baseline to last visit were 14.1 and 16.0 mm Hg, respectively. Response surface analysis provided further evidence that these combinations were optimal for antihypertensive efficacy. All treatments were well tolerated. The incidence of adverse events did not differ significantly between treatment groups; the profile of adverse events on combination therapy was mild and consistent with that of each monocomponent. CONCLUSIONS: All dosage combinations of verapamil SR and trandolapril produced significantly greater reduction of blood pressure than the monotherapy at the same dosage. However, verapamil SR 180 mg in combination with trandolapril 1.0 mg was the dosage with the greatest blood pressure reduction and had the greatest effects compared with the monocomponents.

Antihypertensive Agents↗

PubMed1997

Amperometric bienzymic sensor for aspartame.

An amperometric enzyme electrode for the determination of aspartame was developed by covalent immobilization of alcohol oxidase and alpha-chymotrypsin. A platinum based hydrogen peroxide electrode was used as the detector. Excellent sensitivity was obtained using batch, flow-through and flow injection methods with detection limits of 2 x 10(-7), 4 x 10(-7) and 10(-6) mol l-1, respectively. Different strategies for eliminating interfering compounds, including the introduction of an additional alcohol oxidase-catalase membrane and signal subtraction using an alcohol electrode, were employed. A recovery study on seven food samples was carried out and the results were satisfactory.

Aspartame↗

PubMed1996

Amperometric ammonium ion and urea determination with enzyme-based probes.

Amperometric enzyme probes for ammonium and urea have been assembled and evaluated using immobilized glutamate dehydrogenase and urease enzymes coupled with platinum electrodes. Analytical parameters such as pH, buffer, temperature, probe life-time, enzyme immobilization, cofactor concentration and response time have been optimized. Ammonium was detected in the range 10(-5)-3 x 10(-4) mol l-1. Better reproducibility and stability were achieved using the enzyme GLDH type III and NADH at a concentration of 10(-3) mol l-1. Urea has been determined in the range 10(-5)-3 x 10(-4) mol l(-1) using the enzyme urease first in solution and then immobilized on nylon net. The analysis was based on an amperometric measurement which gives a linear relationship between current and analyte concentration. This considerably improved the sensitivity of the analysis when compared with the potentiometric-based procedures. Moreover, this method does not suffer from the potassium ion interference which affects the potentiometric nonactin-based NH+4 electrodes. Analysis of ammonium and urea were carried out in standard solutions and in saliva samples. Results compared with a spectrophotometric reference procedure correlated well.

Biosensing Techniques↗