Pier Giorgio Zambonin

Molecularly Imprinted Electrosynthesized Polymers: New Materials for Biomimetic Sensors

The preparation and characterization of electrosynthesized poly(o-phenylenediamine) (PPD) imprinted by glucose (iPPD) is reported as the first case of an electrosynthesized polymer molecularly imprinted by a neutral template. The material is employed as the recognition element of a QCM biomimetic sensor for glucose. Scatchard analysis of the relevant calibration curve offers information on the equilibrium and binding sites involved in glucose detection. XPS comparison of PPD and iPPD supports the occurrence of a templating effect. On this basis, molecular imprinting electropolymerization is proposed as a possible strategy for the preparation of new materials with molecular recognition properties to be applied in biomimetic sensors.

Multi-parameter gas sensors based on organic thin-film-transistors

Abstract In this communication, evidence is provided that an organic thin-film-transistor (OTFT) can be used as a novel gas sensor. When exposed to chemical species at room temperature, four parameters can be measured: the bulk conductivity of the organic thin film, the field-induced conductivity, the transistor threshold voltage and the field effect mobility. Measurements of these parameters may allow for recognition of molecular species.

Simultaneous monitoring of glucose and lactate by an interference and cross-talk free dual electrode amperometric biosensor based on electropolymerized thin films

An interference and cross-talk free dual electrode amperometric biosensor integrated with a microdialysis sampling system is described, for simultaneous monitoring of glucose and lactate by flow injection analysis. The biosensor is based on a conventional thin layer flow-through cell equipped with a Pt dual electrode (parallel configuration). Each Pt disk was modified by a composite bilayer consisting of an electrosynthesised overoxidized polypyrrole (PPYox) anti-interference membrane covered by an enzyme entrapping gel, obtained by glutaraldehyde co-crosslinking of glucose oxidase or lactate oxidase with bovine serum albumin. The advantages of covalent immobilization techniques were coupled with the excellent interference-rejection capabilities of PPYox. Ascorbate, cysteine, urate and paracetamol produced lactate or glucose bias in the low micromolar range; their responses were, however, completely suppressed when the sample was injected through the microdialysis unit. Under these operational conditions the flow injection responses for glucose and lactate were linear up to 100 and 20 mM with typical sensitivities of 9.9 (+/- 0.1) and 7.2 (+/- 0.1) nA/mM. respectively. The shelf-lifetime of the biosensor was at least 2 months. The potential of the described biosensor was demonstrated by the simultaneous determination of lactate and glucose in untreated tomato juice samples; results were in good agreement with those of a reference method.

NEW FINDINGS ON POLYPYRROLE CHEMICAL STRUCTURE BY XPS COUPLED TO CHEMICAL DERIVATIZATION LABELLING

Abstract Polypyrrole electrosynthesised from aqueous solutions has been investigated by XPS, both in the conducting (PPY) and in the so-called overoxidised (PPYox) state. An accurate analysis of high resolution spectra, including cross-checking between the independent fittings of different though related signals (e.g. C1s and O1s), is presented, enlightening novel findings on polypyrrole structure. In particular, it suggested, for the first time, that overoxidation breaks polymer chains, producing new oxygen function on α-C (mainly CO). The application of a new chemical derivatization (CD) method to the labelling of this key functional group (CO) would confirm this feature.

Electrosynthesis and characterisation of nanostructured palladium–polypyrrole composites

Abstract Palladium–polypyrrole composite thin films have been synthesised using three different bottom-up procedures all comprising the electrochemical synthesis of palladium nanoparticles that are subsequently potentiostatically deposited or embedded into an electrochemically produced polypyrrole thin film. Transmission electron micrographs of the resulting composites show that the metallic inclusions have a mean diameter of about 5 nm with a homogeneous size distribution. Experimental evidence is also provided that both the nanoparticles and the composite thin films are electroactive. Preliminary results on the extendibility of this approach to the electrosynthesis of other metal–polypyrrole materials (namely Ag–PPy composites) are also presented.

Antifungal activity of polymer-based copper nanocomposite coatings

Eukaryotes, such as fungi, can be harmful pathogen agents, and the control of their bioactivity is critical as humans are eukaryote organisms, too. Here, copper∕polymer nanocomposites are proposed as antifungal spinnable coatings with controlled copper-releasing properties. The tests of the bioactivity show that fungal growth is inhibited on the nanocomposite-coated plates, and the antifungal activity can be modulated by controlling the Cu nanoparticle loading.

Electrosynthesized non-conducting polymers as permselective membranes in amperometric enzyme electrodes : a glucose biosensor based on a co-crosslinked glucose oxidase/overoxidized polypyrrole bilayer

A glucose amperometric biosensor based on glucose oxidase immobilized on an overoxidized polypyrrole (PPyox) platinum modified electrode, by glutaraldehyde co-crosslinking with bovine serum albumine, is described. The advantages of covalent immobilization techniques (e.g. high loading and long-term stability of the enzyme) are coupled with the excellent interferent rejection of electrosynthesized non-conducting polymers. The sensor showed an apparent Michaelis-Menten constant of 16 +/- 0.8 mM, a maximum current density of 490 microA/cm2 and a shelf lifetime of at least 3 months. Ascorbate, urate, cysteine and acetaminophen at their maximum physiological concentrations produced a glucose bias in the low micromolar range. Flow-injection response was linear up to 20 mM glucose with typical sensitivity of 84.0 +/- 1.5 nA/mM. The sensor was tested for glucose determination of untreated serum samples from both normal and diabetic subjects; results of amperometric assay compared well with those obtained by a standard enzymatic-colorimetric method.

Interference-free glucose sensor based on glucose-oxidase immobilized in an overoxidized non-conducting polypyrrole film

SummaryAn amperometric glucose sensor is described; it is based on glucose oxidase immobilized in an overoxidized non-conducting polypyrrole membrane. The overoxidation process of polypyrrole produces a permselective, antifouling membrane capable of rejecting ascorbate, urate, acetaminophen and cysteine, as well as proteins and other surface active components typically present in serum. The amperometric assay of glucose in serum correlates well with an established routine procedure based on an enzymatic-colorimetric method.

An interference-free biosensor based on glucose oxidase electrochemically immobilized in a non-conducting poly(pyrrole) film for continuous subcutaneous monitoring of glucose through microdialysis sampling

A glucose biosensor, based on glucose oxidase immobilized in a non-conducting (overoxidised) polypyrrole film, is described which proved practically immune from faradaic interference arising from endogeneous (ascorbate, urate, cysteine) and exogeneous (acetaminophen) electroactive interferents. The bias introduced in the measurement of 5 mM glucose by the given interferents at their maximum physiological levels never exceeded 2% which is, by far, the lowest value ever reported. The biosensor has been used for continuous subcutaneous monitoring of glucose in a rabbit implanted with a microdialysis probe. The potential and limits of this approach are discussed.

Nanostructured palladium–polypyrrole composites electrosynthesised from organic solvents

Abstract Palladium–polypyrrole nanostructured composite films can be easily synthesised using a two-step procedure comprising the electrochemical synthesis of palladium nanoparticles (Pd-NPs) that are subsequently potentiostatically deposited onto a polypyrrole thin film electrosynthesised from an acetonitrile solution. The composite thin films have good conductivity and their transmission electron micrographs show that the metallic inclusions have a mean diameter of about 5 nm with a homogeneous size distribution. X-ray photoelectron spectroscopy (XPS) analysis reveals the presence of two surface oxidation states for the as-synthesised Pd-NPs as well as for those deposited on the films. On the basis of experimental findings, a structural model for the Pd-NPs is proposed.