Sensor Arrays Based on Phthalocyanines: New Developments on Nanostructured and Biomimetic Electrochemical Sensors

Phthalocyanines are among the most suitable materials for electrochemical sensors due to their versatility and to their unique electrochemical and electrocatalytic properties. Nanostructured films show enhanced surface-to-volume ratios that increase the sensitivity of the sensors. The layer-by-layer (LbL) or the Langmuir-Blodgett (LB) techniques are of special interest for enzyme immobilization because they allow the preparation of biomimetic systems, where enzymes are adsorbed in a lipidic layer. The sensitivity of biosensors can be enhanced by introducing in the sensing films phthalocyanines that facilitate the electron transfer between the enzyme and the electrode. Electrochemical multisensor systems based on phthalocyanines employ a variety of techniques, including potentiometry, amperom-etry, cyclic voltammetry and impedance measurements. With the use of chemometric techniques, it has been possible to discriminate and classify a variety of samples, such as wines, biogenic amines and oils. 4.1 IntroductionAn electronic tongue is a multisensor system formed by a number of non-selective sensors combined with multivariate chemometric tools [1-7]. Sensors play a decisive role in the performance of an electronic tongue. For this reason, many efforts have been dedicated to the development of new sensors with improved characteristics. Metallophthalocyanines (MPc) are among the most interesting materials in the fabrication of chemical sensors because their electrical, optical, mass or redox properties are modified when molecules are adsorbed in the sensing layers of the sensitive material giving rise to different classes of chemical sensors based on different working principles [8-13]. Phthalocyanines have obtained a particularly great success in the field of electrochemical multisensor systems. This is due to the varied electrochemical behavior and catalytic properties of these fully π-conjugated macrocyclic molecules that make them ideal as chemical modifiers in electrochemical sensors [12-18]. In addition, electrochemical sensors based on phthalocyanines can be prepared using a variety of techniques. In this aspect, nanotechnology has provided new tools to prepare sensors with improved sensitivity [13]. Electrochemical biosensors taking advantage of the specificity enzyme-substrate can be an alternative to conventional electrochemical sensors. Phthalocyanines have proven to be efficient electron mediators for electron transfer between the enzyme and the ele