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Biomedical subjects

M Minunni

Publications and source records attributed to M Minunni.

13 recordsLinked to original sources
PubMed2005

Aptamer-based biosensors for the detection of HIV-1 Tat protein.

Two biosensors have been constructed using an RNA aptamer as biorecognition element. The aptamer, specific for HIV-1 Tat protein, has been immobilised on the gold surface of piezoelectric quartz crystals or surface plasmon resonance (SPR) chips to develop a quartz crystal microbalance (QCM)-based and an SPR-based biosensor, respectively. Both the biosensors were modified with the same immobilisation chemistry based on the binding of a biotinylated aptamer on a layer of streptavidin. The binding between the immobilised aptamer and its specific protein has been evaluated with the two biosensors in terms of sensitivity, reproducibility and selectivity. A protein very similar to Tat, Rev protein, has been used as negative control. The two biosensors both were very reproducible in the immobilisation and the binding steps. The selectivity was high in both cases.

Biosensing Techniques↗
PubMed2004

Analytical applications of aptamers.

So far, several bio-analytical methods have used nucleic acid probes to detect specific sequences in RNA or DNA targets through hybridisation. More recently, specific nucleic acids, aptamers, selected from random sequence pools, have been shown to bind non-nucleic acid targets, such as small molecules or proteins. The development of in vitro selection and amplification techniques has allowed the identification of specific aptamers, which bind to the target molecules with high affinity. Many small organic molecules with molecular weights from 100 to 10,000 Da have been shown to be good targets for selection. Moreover, aptamers can be selected against difficult target haptens, such as toxins or prions. The selected aptamers can bind to their targets with high affinity and even discriminate between closely related targets. Aptamers can thus be considered as a valid alternative to antibodies or other bio-mimetic receptors, for the development of biosensors and other analytical methods. The production of aptamers is commonly performed by the SELEX (systematic evolution of ligands by exponential enrichment) process, which, starting from large libraries of oligonucleotides, allows the isolation of large amounts of functional nucleic acids by an iterative process of in vitro selection and subsequent amplification through polymerase chain reaction. Aptamers are suitable for applications based on molecular recognition as analytical, diagnostic and therapeutic tools. In this review, the main analytical methods, which have been developed using aptamers, will be discussed together with an overview on the aptamer selection process.

Acoustics↗
PubMed2004

Development of biosensors with aptamers as bio-recognition element: the case of HIV-1 Tat protein.

The in vitro selection of combinatorial libraries of RNA/DNA, has allowed the identification of specific nucleic acids (aptamers) which bind to a wide range of target molecules with high affinity and specificity. In this work, an RNA aptamer, specific for the protein trans-activator of transcription (Tat) of HIV-1, has been used as bio-recognition element to develop a biosensor (aptasensor). The biosensor was optimised using piezoelectric quartz-crystals as transducers and the aptamer was immobilised on the gold electrode of the crystal. The immobilisation procedure was based on the interaction between the biotinylated aptamer and streptavidin previously deposited on the electrode. The main analytical characteristics of the biosensor, such as sensitivity, selectivity and reproducibility, have been studied in details. An optimised regeneration procedure allowed the multiple use of the aptamer-coated crystal. The aptasensor has been compared with the corresponding immunosensor, based on the specific monoclonal anti-Tat antibody. The antibody was immobilised on a layer of carboxylated dextran previously deposited on the gold electrode. The results demonstrated that the use of a biosensor with a specific aptamer as bio-recognition element could be an interesting approach in the detection of proteins, which has been here examined considering a model system.

Biosensing Techniques↗
PubMed2003

Disposable electrochemical sensor for rapid determination of heavy metals in herbal drugs.

Analysis of herbal drugs and extracts need rapid and affordable methods to assure the quality of products. The application of the electrochemical sensors in the field of quality control of herbal drugs, herbal drug preparations and herbal medicinal products appears very promising, advantageous and alternative to conventional methods due to their inherent specificity, simplicity and for the fast response obtained. This paper presents a proposal about the application of disposable electrochemical sensors associated with electroanalytical instrumentation for the detection of heavy metal analysis in herbal drugs. In particular samples of St. John's wort were analysed applying anodic stripping voltammetry. The content of Cd and Pb were evaluated. The ICP spectroscopy was used as reference method.

Electrochemistry↗
PubMed2001

Biosensors as new analytical tool for detection of Genetically Modified Organisms (GMOs).

Three different biosensors for detection of Genetically Modified Organisms (GMOs) are presented. The sensing principle is based on the affinity interaction between nucleic acids: the probe is immobilised on the sensor surface and the target analyte is free in solution. The immobilised probes are specific for most inserted sequences in GMOs: the promoter P35S and the terminator TNOS. Electrochemical methods with screen-printed electrodes, piezoelectric and optical (SPR) transduction principles were applied.

Biosensing Techniques↗
PubMed2000

Comparison among differential pulse voltammetry, amperometric biosensor, and HPLC/DAD analysis for polyphenol determination.

Polyphenols are widespread in vegetables and fruits. They can play an important role in human diet and health, and they influence the sensorial properties of many foods, and act as natural antioxidants. This study was conducted using HPLC/DAD, tyrosinase biosensor, and differential pulse voltammetry (DPV) analyses to detect polyphenolic compounds in natural complex matrices. The analyses were applied to a series of both standards and natural extracts derived from grape, olives, and green tea. The pure compounds include phenolic acids, flavones, flavonols, catechins, tannins, and oleuropein. HPLC/DAD, DPV, and the biosensor approach were used as independent analytical techniques. Bare graphite screen-printed electrodes were employed in DPV and in the biosensor analysis. The most accurate data were obtained by HPLC/DAD analysis, while the DPV approach using screen-printed electrodes could represent a quick screening method for the determination of polyphenols in natural extracts. Use of the biosensor for the analysis of complex matrices needs further study in order to improve its performance.

Biosensing Techniques↗
PubMed1998

Surface modifications for the development of piezoimmunosensors.

Four different techniques for the immobilisation of proteins onto the gold electrode of a piezoelectric quartz crystal were investigated. The examined techniques were adsorption, avidin-biotin binding and two different types of covalent binding on self-assembled monolayers (SAM), dithiobis(succinimidylpropionate) (DSP) and a dextran modified thiol monolayer. The reaction of the immobilised proteins (bovine serum albumin (BSA) and anti-human IgG) with their specific antibodies, anti-BSA and hIgG (50 and 200 micrograms/ml) were studied using a quartz crystal microbalance and then compared. Many cycles of measurements were performed on the same crystal regenerating the gold surface with a solution of glycine.HCl, 100 mM, pH 2.1. The interactions of the immobilised reagents with non-specific antibodies were also studied. The adsorption protocol was the quickest, but did not allow regeneration with glycine.HCl. Thiol-dextran coated surfaces did not show any detectable response to non-specific reagents, but needed a very long and complicated protocol. DSP and avidin-biotin coating procedures were easy and not too long. They seemed to have the best characteristics of reproducibility among different crystals and possibility of regeneration of the coated surface, but the percentage of non-specific binding was high.

Adsorption↗
PubMed1996

In vivo cytogenetic effects of natural humic acid.

As humic compounds are naturally widespread in the environment and present in surface water, studies on their genotoxicity are justified. Humic acid (HA) has not been demonstrated to be genotoxic either in vitro or in vivo. In the present paper we investigated its activity both in intestinal and bone marrow cells following a single dose (100 mg/kg b.w. corresponding to 0.5 ml per animal of an aqueous solution of 4 g/l) of HA administered to mice by gastric intubation, to mimic the most likely route of human exposure. HA induced structural and, in particular, numerical chromosome abnormalities in intestinal cells. A marginal, non-significant induction of aneuploidy was also found in bone marrow cells.

Aneuploidy↗
PubMed1994

Characterization of monoclonal antibodies to 2,4-dichlorophenoxyacetic acid using a piezoelectric quartz crystal microbalance in solution.

Piezoelectric quartz crystals (resonance frequency 10 MHz) were used for an investigation of the immunochemical reaction between 2,4-dichlorophenoxyacetic acid (2,4-D) herbicide and several monoclonal antibodies prepared against 2,4-D. The herbicide was immobilized on the gold electrodes of the crystals silanized with 3-aminopropyltriethoxysilane. The activated carboxylic group of 2,4-D was linked either directly to the silanized surface or through hexamethylenediamine or albumin as a macromolecule. The interaction of the immobilized antigen with monoclonal antibody in solution was followed as a change in the resonant frequency of the crystals. The best results were achieved using 2,4-D attached to albumin. The affinity binding of five monoclonal antibodies was characterized by association (ka) and dissociation (kd) kinetic rate constants and by equilibrium association constants (KA) which were obtained from the experimental frequency vs. time curves.

2,4-Dichlorophenoxyacetic Acid↗
PubMed1993

Cytogenetic effects of benzimidazoles in mouse bone marrow.

The cytogenetic effects of three benzimidazoles, i.e., benomyl, methyl thiophanate and methyl 2-benzimidazolecarbamate (MBC), were studied in mouse bone marrow cells by analyzing three genetic endpoints: micronuclei, structural chromosome aberrations plus or minus gaps, and aneugenic effects (hyperdiploidy or polyploidy). In general, the effects were small, but it was observed that benomyl and MBC significantly induced micronuclei as well as aneugenic effects, hyperdiploidy (no metaphases with more than one or two extra chromosomes, 2n + 1 or 2n + 2, were observed) and polyploidy (4n). The induction of chromosome gaps and breaks was less evident. Methyl thiophanate significantly induced micronuclei, but it was less effective than benomyl and MBC. Our results showed that micronuclei are a good indicator of aneugenic effects in mouse bone marrow cells. A curvilinear trend test has been devised to fit the curves originating from the time-dependent responses.

Analysis of Variance↗
PubMed1990

Genotoxicity of methylglyoxal: cytogenetic damage in human lymphocytes in vitro and in intestinal cells of mice.

The mutagenic activity of methylglyoxal (MG) was assayed in vitro in human lymphocytes [induction of chromosomal aberrations (CAs), sister chromatid exchanges (SCEs) and micronuclei] both in the presence and in the absence of metabolic activation (S9 mix). The Ames/microsome test was performed with the Salmonella typhimurium strains considered more responsive (TA102 and TA104). Positive results were obtained for all the genetic endpoints analysed. In human lymphocytes the activity of MG is decreased by the presence of S9 mix. In the in vivo studies, the metaphase analysis in the ileum and duodenum cells of mice treated per os with MG (400 and 600 mg/kg body wt) gave negative results for CA induction, while only a weak increase of SCE in duodenum cells at the higher dose was obtained. Dimethylhydrazine (25 mg/kg body wt), as positive control, was clearly active in inducing both CAs and SCEs in the same intestinal tissues.

Aldehydes↗