High-Capacity Conductive Nanocellulose Paper Sheets for Electrochemically Controlled Extraction of DNA Oligomers

Highly porous polypyrrole (PPy)-nanocellulose paper sheets have been evaluated as inexpensive and disposable electrochemically controlled three-dimensional solid phase extraction materials. The composites, which had a total anion exchange capacity of about 1.1 mol kg−1, were used for extraction and subsequent release of negatively charged fluorophore tagged DNA oligomers via galvanostatic oxidation and reduction of a 30–50 nm conformal PPy layer on the cellulose substrate. The ion exchange capacity, which was, at least, two orders of magnitude higher than those previously reached in electrochemically controlled extraction, originated from the high surface area (i.e. 80 m2 g−1) of the porous composites and the thin PPy layer which ensured excellent access to the ion exchange material. This enabled the extractions to be carried out faster and with better control of the PPy charge than with previously employed approaches. Experiments in equimolar mixtures of (dT)6, (dT)20, and (dT)40 DNA oligomers showed that all oligomers could be extracted, and that the smallest oligomer was preferentially released with an efficiency of up to 40% during the reduction of the PPy layer. These results indicate that the present material is very promising for the development of inexpensive and efficient electrochemically controlled ion-exchange membranes for batch-wise extraction of biomolecules

Electrogravimetric detection of DNA hybridization on polypyrrole copolymer

The immobilization of an oligonucleotide via a copolymerisation with a pyrrole monomer onto a Pt surface has been realized on a quartz crystal microbalance (QCM). The efficiency of this biosensor has been evaluated through the hybridization with different targets. Hybridization and adsorption responses were monitored in-situ by QCM frequency change

Approach to writing and simultaneous reading of micropatterns: Combining surface plasmon resonance imaging with scanning electrochemical microscopy (SECM)

International audienceThis work establishes the compatibility of surface plasmon resonance imaging (SPR-i) with the visualization of localized electropolymerization. The “writing” of polypyrrole and polypyrrole-oligonucleotide patterns onto thin gold films is demonstrated using scanning electrochemical microcopy (SECM), while an optical method, SPR-i, simultaneously detected the formed micropatterns. The combination of these two methods, SECM/SPR-i, has the advantage of not only controlling the patterning process but also providing unique information on the micropattern formation. The influence of the pulsing time and the monomer concentration on the spot size and its characteristics has been investigated in detail using SPR-i. Fluorescence microscopy and atomic force microscopy have also been used to support the data obtained by SPR-i

Point Mutation Detection by Surface Plasmon Resonance Imaging Coupled with a Temperature Scan Method in a Model System

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Contactless electrofunctionalization of a single pore

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Fast detection of both O157 and non-O157 shiga-toxin producing Escherichia coli by real-time optical immunoassay

International audienceAmong bacterial pathogens involved in food-illnesses, seven serogroups (O26, O45, O103, O111, O121, O145 and O157) of Shiga-toxin producing Escherichia coli (STEC), are frequently identified. During such outbreak, and due to the perishable property of most foodstuff, the time laps for the identification of contaminated products and pathogens is thus critical to better circumvent their spread. Traditional detection methods using PCR or culture plating are time consuming and may present some limitations. In this study, we present a multiplexed immunoassay for the optical detection of most commonly enterohemorrhagic E. coli serogroups: O26, O45, O103, O111, O121, O145 and O157:H7 in a single device. The use of Surface Plasmon Resonance imaging not only enabled the label-free analysis of the samples but gave results in a real-time manner. A dedicated protocol was set up for the detection of both low contaminating bacterial concentrations of food samples (5 CFU per 25 g) and postenrichment aliquots. By combining one single device for the detection of O157 and non-O157 STEC in a label-free manner, this rapid approach may have an important economic and societal impact