Martial Billon

Reversible oligonucleotide immobilisation based on biotinylated polypyrrole film

Abstract In this paper, we describe the design of a new versatile and reversible DNA sensor. The system is based on biotin grafting-units, covalently linked to a polypyrrole matrix, able to anchor large biomolecules, thanks to biotin/avidin affinity. These grafting-units can be regenerated after the “denaturation” of the biotin/avidin link allowing to reuse the matrix for the immobilisation of an other assembly and then the possibility to generate a new sensor.

Conducting polymers as a link between biomolecules and microelectronics

Abstract Biosensors based on electronic conducting polymers (ECPs) appear particularly well suited to the requirements of modern biological analysis: multiparametric assays, high information density and miniaturization. We describe a new methodology for the preparation of addressed DNA matrices. The process includes an electrochemically directed copolymerization of pyrrole and oligonucleotides bearing on their 5′ end a pyrrole moiety. The resulting polymer film deposited on the addressed electrode consists of pyrrole chains bearing covalently linked oligonucleotides. An oligonucleotide array was constructed on a silicon device bearing a matrix of 48 addressable 50 μm x 50 μm gold microelectrodes. This technology was successfully applied to the genotyping of Hepatitis C Virus in blood samples. Fluorescence detection results show good sensivity and a high degree of dimensional resolution. The need for versatile processes for the immobilization of biological species on surface led us to extend our methodology. A biotinylated surface was obtained by co-electropolymerization of pyrrole and biotin-pyrrole monomers. The efficiency for recognition (and consequently immobilization) of R-phycoerythrin-avidin was demonstrated by fluorescence detection. Copolymerization of decreasing ratios of pyrrole-biotin over pyrrole allowed us to obtain a decreasing scale of fluorescence.

Electropolymerization as a versatile route for immobilizing biological species onto surfaces

Biosensors based on electronic conducting polymers appear particularly well suited to the requirements of modern biological analysis—multiparametric assays, high information density, and miniaturization. We describe a new methodology for the preparation of addressed DNA matrices. The process includes an electrochemically directed copolymerization of pyrrole and oligonucleotides bearing on their 5′ end a pyrrole moiety. The resulting polymer film deposited on the addressed electrode consists of pyrrole chains bearing covalently linked oligonucleotides (ODN). An oligonucleotide array was constructed on a silicon device bearing a matrix of 48 addressable 50 × 50 µm gold microelectrodes. This technology was successfully applied to the genotyping of hepatitis C virus in blood samples. Fluorescence detection results show good sensitivity and a high degree of spatial resolution. In addition, gravimetric studies carried out by the quartz crystal microbalance technique provide quantitative data on the amount of surface-immobilized species. In the case of ODN, it allows discrimination between hybridization and nonspecific adsorption. The need for versatile processes for the immobilization of biological species on surfaces led us to extend our methodology. A biotinylated surface was obtained by coelectropolymerization of pyrrole and biotin-pyrrole monomers. The efficiency for recognition (and consequently immobilization) of R-phycoerythrin-avidin was demonstrated by fluorescence detection. Copolymerization of decreasing ratios of pyrrole-biotin over pyrrole allowed us to obtain a decreasing scale of fluorescence.

Conjugated alternating copolymer of dialkylquaterthiophene and fluorenone: synthesis, characterisation and photovoltaic properties

New π-conjugated alternating copolymers containing thienylene and fluorenone units, namely poly[(5,5‴-dioctyl-[2,2′;5′,2″;5″,2‴]quaterthiophene)-alt-(2,7-fluoren-9-one)] (PQTF8), as well as its analogue without fluorenone groups (PQT8), have been synthesized. Absorption studies carried out both in solution and in thin films indicate that the presence of fluorenone chromophores in PQTF8 leads to a significant extension of the absorption spectrum in the visible range as compared to PQT8. The redox properties of both polymers, in particular their LUMO and HOMO levels, have been characterized by cyclic voltammetry and have been found suitable for potential use of these systems in organic solar cells. Finally, these materials have been tested as donor components in bulk-heterojunction-type photovoltaic cells using PCBM as an electron acceptor. We demonstrate a strong effect of the polymers molecular weight on crucial cell parameters, such as the short-circuit current density Jsc, and therefore on the overall cell efficiency. This effect is particularly pronounced for PQTF8-based cells leading to power conversion efficiencies up to 1.5% for the highest molecular weights.

In situ study of polypyrrole morphology by STM: effect of the doping state

An electronic conducting polymer is submitted to strong structural variations during the doping (or dedoping) process due essentially to inclusion (or exclusion, respectively) of anions in its structure. The insertion (or exclusion) of ions induces a swelling (or deflation) phase and therefore modifications of the surface morphology. In this article we study these two correlated phenomena, surface morphological variations and swelling process, by scanning tunneling microscopy (STM) of a polypyrrole film as a function of its doping state. In order to account best for the modifications induced by the electrode potential, the STM images are obtained in situ. This allows us to follow the evolution of the swelling process and the surface morphological variations associated with the electrodoping mechanism.

Comparison by QCM and photometric enzymatic test of the biotin-avidin recognition on a biotinylated polypyrrole

By gravimetric measurements using a quartz cristal microbalance (QCM), we have studied the immobilization of biotinylated glucose oxidase enzymes (B-GOx) bound through on an intermediate avidin layer to a biotinylated polypyrrole film. The aim is to assess the amount of B-GOx specifically anchored on the biotinylated polypyrrole/avidin assembly thank to the biotin/avidin interaction between avidin and B-GOx. Indeed the estimated amount from the QCM measurement corresponds to the specific recognition of avidin/B-GOx added to a non-specific recognition (adsorption) of B-GOx. In order to discriminate these two phenomena, we have carried out a study by QCM of the anchoring of B-GOx on an avidin layer linked by adsorption to a polypyrrole free from biotin units. From QCM measurements we have deduced for the biotinylated polypyrrole/avidin assembly that the amount of B-GOx bound via the biotin/avidin interaction and those due to the avidin adsorption process correspond to 3.9 pmol cm(-2) (1.3 equivalent of B-Gox monolayer) and 1.4 pmol cm(-2) (0.46 equivalent of B-GOx monolayer) respectively. These values have been corroborated by measurements of the enzymatic activity of GOx.

Bistable molecules development and Si surface grafting: two chemical tools used for the fabrication of hybrid molecule/Si CMOS component

For the past ten years, there has been considerable interest dedicated to the miniaturisation of CMOS devices. The research axes followed to obtain scalable devices are numerous as the possibilities offered by both technological (top-down) and new (bottom-up) approaches are studied. Concerning the latter approach molecular electronics is a growing field of interest. Notably, the fabrication of hybrid molecule/Si structures paves the way for development of devices with electrical performances that can be tuned thanks to the molecular properties initially targeted. Here we present the recent results obtained in the two approaches we follow in order to develop new hybrid molecule/Si memory elements. The first axis focuses on the development of specific molecules that could allow a fine tuning of the memory retention characteristic. The second axis deals with the integration of redox molecules inside capacitive cells and the study of their electrical properties. The capacitance of such components clearly shows that an effect of charge transfer is observed only when redox active molecules (porphyrins) are grafted on Si.

Electrode-deposited films of polyrotaxanes: electrochemically induced gliding motion

Using the three-dimensional template effect of copper(I) or copper(II), a macrocycle incorporating two different chelating units was threaded by a coordinating molecular fragment whose two ends bear pyrrole nuclei; after electropolymerization, an electroactive film was obtained that clearly showed pirouetting of the ring induced by reducing the five-coordinate copper(II) complex to copper(I). The motion is driven by the difference in the stereoelectronic preferences of copper(I) and copper(II). The present system allows motions of the monovalent complex only.

Electroactive polymer films of silver complexes with intertwinedand interlocked ligands: the AgI–Ag0 redoxcouple as a topological probe

The electrochemical properties of bis(2,9-diaryl-1,10-phenanthroline)silver complexes are reported. The redox potentials of the coordinated metal centre are strongly dependent on the topology of the organic backbone surrounding the metal centre and its set of ligands. This particular property can be used for the evaluation of the topological characteristics of different polypyrrole matrices built around entwined 2,9-diaryl-1,10-phenanthroline moieties.

A Versatile Electronic Tongue Based on Surface Plasmon Resonance Imaging and Cross-Reactive Sensor Arrays—A Mini-Review

Nowadays, there is a strong demand for the development of new analytical devices with novel performances to improve the quality of our daily lives. In this context, multisensor systems such as electronic tongues (eTs) have emerged as promising alternatives. Recently, we have developed a new versatile eT system by coupling surface plasmon resonance imaging (SPRi) with cross-reactive sensor arrays. In order to largely simplify the preparation of sensing materials with a great diversity, an innovative combinatorial approach was proposed by combining and mixing a small number of easily accessible molecules displaying different physicochemical properties. The obtained eT was able to generate 2D continuous evolution profile (CEP) and 3D continuous evolution landscape (CEL), which is also called 3D image, with valuable kinetic information, for the discrimination and classification of samples. Here, diverse applications of such a versatile eT have been summarized. It is not only effective for pure protein analysis, capable of differentiating protein isoforms such as chemokines CXCL12α and CXCL12γ, but can also be generalized for the analysis of complex mixtures, such as milk samples, with promising potential for monitoring the deterioration of milk.