M. Del Carlo

Gold nanoparticles-peptide based gas sensor arrays for the detection of food aromas.

A gas sensor array based on peptide modified gold nanoparticles deposited onto 20MHz quartz crystal microbalances has been realized. Glutathione and its constituting aminoacids and dipeptides have been used as ligands. A great increase in sensitivity (2 orders of magnitude) was achieved using gold nanoparticles versus monolayer modified QCMs. The sensors have been characterised in terms of sensitivity for hexane, water, trimethylammine and ethanol. Highest sensitivity was found for water. The ability to discriminate typical food aromas as cis-3-hexenol, isopentylacetate, ethylacetate, and terpinen-4-ol dissolved in different solvents was studied using a gas sensor array constituted by gold nanoparticles modified with the glutathione peptides, thioglycolic acid and an heptapeptide. The array was found able to discriminate the food aromas, the response being dependent on the polarity of the solvent used. Tests on real olive oil samples gave a satisfactory separation among samples having defects versus non defected samples demonstrating that this approach has high potential for the development of gas sensor arrays to be used in real samples.

Neutral loss and precursor ion scan tandem mass spectrometry for study of activated benzopyrene–DNA adducts

AbstractMethodology for detection of activated benzo[a]pyrene (B[a]P)–nucleoside adducts by liquid chromatography–tandem mass spectrometry is reported. Adducts of B[a]P-dihydrodiol epoxide (B[a]PDE) with guanosine and adenosine have been detected for the first time by use of precursor ion scan and neutral loss scan. B[a]P was then activated by use of UV irradiation and some of the products obtained have been identified by taking advantage of the information obtained for B[a]PDE. Photoactivation has also been carried out in the presence of hydrogen peroxide; this resulted in a higher yield of products with increased production of BaP diones. The reactivity of these compounds toward nucleosides has been tested. The proposed method was successfully used for detection of one stable guanosine–B[a]P dione adduct. FigureInteractions between activated B[a]P and DNA; MS/MS detection strategies

Oligopeptides as mimic of acetylcholinesterase: from the rational design to the application in solid-phase extraction for pesticides.

Three different peptides (His-Glu-Pro-Ser, His-Gly-Ser-Ala and Glu-Pro-Ser-Ala) were selected and tested to be used as affinity binding receptors for organophosphate and carbamate pesticides. The peptides were rationally designed by mimicking acetylcholinesterase active site. The simulated binding energy of the three tetrapeptides versus one model of organophosphate (paraoxon) and one of carbamate (carbaryl) pesticide was calculated; a good correlation between shape designed and binding score was obtained. The binding properties of the peptide-pesticide interaction were studied following the variation of UV-visible spectra in different solvents. The binding constants in water, which were nicely correlated with computational data, ranged from 506 (+/-115) to 36(+/-2) M(-1). All the peptides had a 5-fold decrease in binding by changing solvent, going from water to less polar ethanol. The binding affinity suggested the use of these ligands as a preanalytical tool in extraction cartridges. The tetrapeptides efficiency was tested linking the peptides to two different supports. The cartridges prepared using His-Glu-Pro-Ser sequence was, as predicted, able to bind paraoxon and carbaryl with recovery values in the 72-88% range at pH 4.5. Intercolumn, interday RSD was in the 4-7% range. The columns were used for 80 cycles before losing retention ability.

Piezoelectric Sensors Based on Biomimetic Peptides for the Detection of Heat Shock Proteins (HSPs) in Mussels

Abstract We describe a set of label‐free piezoelectric biosensors for fast, qualitative, and direct detection of HSP 70 in crude extract of the mussel mantle. A monoclonal anti‐HSP 70 antibody and three heptapeptides chosen using a computational/combinatorial approach were immobilized covalently to gold particles on quartz surfaces using a self‐assembled monolayer (SAM). A clear frequency shift in the presence of standard solutions of HSP 70 from bovine brain was obtained. The difference in signal intensity among the biomimetic sensors (the peptide sensors) was nicely correlated with the computationally predicted binding scores. Moreover, the peptides exhibited a signal comparable to the monoclonal antibody based immunosensor. Regeneration of the affinity sensors was also investigated obtaining a significant loss of signal only after 10 regeneration cycles with repeatability in the 20%–28% range and reproducibility in the 25%–35% range. Cross‐reactivity of the HSP sensors was tested using bovine serum albumin (BSA) and rabbit IgG. All the affinity sensors exhibited low nonspecific binding, compared with a blank sensor and a negative control sensor. The sensitivity pattern with the real sample (mussel mantle) reflected the one obtained from the standard solution of HSPs 70, demonstrating that all the sensors are able to detect the target analyte in a complex matrix as in a crude extract.

Detection of benzo(a)pyrene photodegradation products using DNA electrochemical sensors.

The reactivity of photodegradation products of benzo(a)pyrene vs. DNA has been assessed using both genomic and oligonucleotide based DNA electrochemical sensors. The kinetic of a photooxidation reaction of benzo(a)pyrene (BaP) carried out in controlled conditions using a 6 W UV lamp peaked at 365 nm has been studied using LC with fluorimetric detection. Degradation of benzo(a)pyrene by both UV and UV/H(2)O(2) exhibited pseudo-first-order reaction kinetics with half-lives ranging from 3.0 to 9.8h depending on the pH and on the amount of H(2)O(2). The oxidation products of benzo(a)pyrene obtained in different conditions were tested on genomic ssDNA electrochemical sensors obtained via immobilisation of salmon testis ss-DNA on graphite screen-printed electrodes. Guanines oxidation signals obtained using chronopotentiometry were used to detect the interaction of the products with DNA. The dose-response curve obtained with benzo(a)pyrene incubated 24 h at pH 4.7 was different from that of the parent compound indicating a different type of interaction with DNA. A DNA hybridisation sensor was also assembled using a thiolated/biotynilated 24-mer oligonucleotide immobilised on a gold screen-printed electrode and avidin-alkaline phosphatase conjugate. A voltammetric detection of naphtol was used to detect the hybridisation reaction. A net inhibition of the hybridisation reaction was observed after incubation with benzo(a)pyrene oxidation products that was attributed to the formation of stable adducts with the guanines of the biotinylated strand. LC-MS-MS studies of the oxidation products confirmed the presence of chemical species potentially forming adducts with DNA. The data reported demonstrate that DNA electrochemical sensors have the potential to be used to monitor remediation processes and to assess the potential toxicity vs. DNA of chemicals forming stable DNA adducts.

Novel oligopeptides based e-nose for food quality control: Application to extra-virgin olive samples

The potential of an electronic nose to discriminate olive oil samples based on their sensory profiles is proposed. The e-nose was constituted by an array of seven quartz crystal microbalance sensors modified with Gold Nanoparticles (GNPs) conjugated to short peptides. Forty olive oil samples headspaces were characterised by headspace solid-phase microextraction gas chromatography-mass spectrometry analysis to evaluate chemical composition; in parallel, they were chemically and sensory evaluated according to European Regulation EEC 2568/91 and amendments and EU Regulation 640/2008. The steady state sensor responses obtained with the e-nose setup were used to evaluate the discrimination properties of the system by principal component analysis and partial least square method. The results of this study provided a promising perspectives for the use of the electronic nose as a low-cost, easy to use and rapid system for the quality control of extra virgin, virgin and lampante (non-edible) olive oil. This system ...

Multiple Minima Hypersurfaces Procedures for Biomimetic Ligands Screening

In this work the interaction of the pesticide carbaryl with two groups of biomimetic ligands, peptides and MIPs was screened by multiple minima hypersurfaces (MMH) procedures, through the AM1 semiempirical method. Data related to the properties of the molecular association of the complex biomimetic ligand-pesticide were obtained and compared with another molecular modeling algorithm named Leapfrog, as included in the Sybyl software package, and experimental results from the literature, remarking good correlation between them. All important MMH program parameters (cells number, box size, conformers) were studied and optimized with the aim of getting the minimum computation time without losing the correlation with experimental data. The data demonstrated that MMH approach can be used as a fast biomimetic ligand screening tool for MIPs. In the case of peptides the computation time was not comparable with the molecular dynamics methods conventionally used for this approach.

MIP-MEPS based sensing strategy for the selective assay of dimethoate. Application to wheat flour samples

The aim of this work was to demonstrate the potentialities of the use of a molecularly imprinted (MIP) sensor coupled to a microextraction by packed sorbent (MEPS) strategy for the selective and sensitive detection of dimethoate in real samples. A dimethoate-polypyrrole MIP film was realised by cyclic voltammetry (CV) on the surface of a glassy carbon electrode (GCE). Being dimethoate electro-inactive, K3[Fe(CN)6] was used as probe for the indirect quantification of the analyte via the decrease of redox peaks observed upon binding of the target analyte. Detection of dimethoate at low nanomolar range was achieved with linearity in the 0.1-1nM range. Relative standard deviation calculated for different electrodes at 0.5nM of dimethoate was < 3% and selectivity was very satisfactory being the response for omethoate only 23% of dimethoate. A MEPS strategy for the extraction of dimethoate from a challenging matrix as wheat flour was then used in conjunction with the MIP electrochemical sensor. The procedure applied to flour samples spiked with dimethoate at 0.5 MRL, MRL, and 1.5 MRL gave very favourable comparison with a validated UHPLC-MS/MS method with deviations in the -21% /+17% range, demonstrating the feasibility of the approach as screening assay. This work clearly shows that the sequential use of a microextraction based procedure and electrochemical sensing system is low cost, easy to realise and use and can open new perspectives for the development of selective sensing system to be used in field or decentralised lab testing for the selective screening of target analytes.

Carbon Black modified glassy carbon electrode for the detection of antioxidants compounds

In this paper we describe the use of Carbon Black (CB) as electrode modifier of the glassy carbon surface to achieve improved performance in terms of electrode stability, sensitivity and repeatability with respect to the naked glassy carbon electrode. The main advantage of the CB modified GC electrode with respect to other carbon electrode materials is the resistance to passivation which leads to the possibility of electrode reusing for tens of repeated measurements; thus avoiding electrode regeneration which represent the major limitation to “real world” application of such approach.

Oligopeptides-Based Gas Sensing for Food Quality Control

In this work a new kind of electronic nose, based on modified quartz crystal microbalance (QCM) array of gas sensors, is presented. The QCM surfaces have been covered with gold nanoparticles (GNPs) bearing short peptide moieties. The array was composed of eight modified QCM, one carrying only GNPs without the peptide moiety and seven modified with peptides. Three peptides were synthesized in order to test the response variability to different amino acid sequences of the same length. Electronic nose has been challenged with pure compounds and real food sample analysis demonstrating its ability to discriminate between different aroma patterns after simple statistical analysis such as PCA.