Andrea Valsesia

This paper describes a novel technique to produce polypyrrole-based nanoelectrodes for electrochemical detection purpose. The fabrication process relies on the creation of patterned nanotemplates i.e., nanometric gold spots surrounded by an electrically insulating material (SiOx). The authors carry out their research as members of the Nanob-Biotechnology project at JRC, Italy.

The NanoBiotechnology project carried out at JRC aims at building a technology platform based on long range experience in surface engineering and biophotonics that allows the development new bio-interfaces, biosensors and diagnostics systems with applications in the emerging Environment and Health priority.

Nano-Biotechnology for Health Applications - Biosensors

At the convergence of physics, chemistry and biology, Nanobiotechnology deals with the study, understanding and transformation of biosystems (living or non-living) to create and use functional structures and devices, which have novel properties and functions associated with their "nanoscopic" dimensions. In this context one group of researchers at the JRC focuses especially on biosensors. A biosensor is generally defined as a compact analytical device incorporating a biological sensing element intimately associated with a physicochemical transducer. It produces either discrete or continuous signals, which are proportional to the concentration of the target analyte. The interaction between the analyte and recognition biomolecules is an event on the molecular scale, which can be detected as a local change in mass, in optical or in electrical properties. Recognizing elements are generally biomolecules such as enzymes, antibodies or even cells with highly specific recognition abilities, usually immobilized on solid supports. The transducers can be devices such as piezoelectric materials, electrodes or wave-guides that are react to the analyte-biomolecule interaction and yield a measurable electric or optical signal of their corresponding response.

Summary - Fabrication of Polypyrrole-Based Nanoelectrode Arrays by Colloidal Lithography

The implementation of sensor platforms providing high sensitivity of detection is a crucial step for the design of the new analytical device generation for biosensor developments. Designing platform with active/non-actives region at nanoscale has shown already a drastic increase of sensitivity. Besides, the electrochemical sensitivity can be as well enhanced by using nano-electrode arrays that increase mass transport rate. Polypyrrole (PPy) is a good candidate to fulfil these requirements. Its preferential material for bio-analytical electrochemistry based sensor thanks to its good environmental stability, excellent biocompatibility and higher conductivity, together with the possibility of being functionalised with biological relevant functional groups. In this work surfaces with PPy nano pillars were fabricated by electrochemically growing PPy in a nano-template of gold nano-seeds in a silicon oxide (SiOx) matrix. Atomic force Microscopy and Scanning Kelvin Microscopy demonstrated that PPy grown only inside the conductive gold seeds, creating nano pillars of conductive material surrounded by an insulating material. The nano-structured surfaces were studied by Cyclic Voltammetry using hexacyanoferrate and the typical sigmoidal shape voltammogram of nanoelectrodes was obtained . Square Wave Voltammetry was tested in the surface and a well defined peak was obtained which indicates that the nanoarray is a promising surface for use in trace analytical analysis.

Andrea Valsesia, Patrícia Lisboa, Pascal Colpo, and François Rossi*, European Commission, Joint Research Center, Anal. Chem., 78 (21), 7588 -7591, 2006. 10.1021/ac0609172 S0003-2700(06)00917-6, Web Release Date: September 26, 2006, Copyright © 2006 American Chemical Society, Received for review May 18, 2006. Accepted August 10, 2006.