Bioelectronic tongues

© 2013 by Taylor & Francis Group, LLC. There is unpaired activity in the design of new sensors and biosensors, normally directed to the implementation of new concepts, designs, or configurations, in all cases heading to improved biodevices showing perfect selectivity. Opposite to the search of biosensors with better specificity, there is a different approach that appeared in the late 1990s that proposes the use of arrays of sensors in order to obtain some added value in the generation of analytical information. Some variants of this approach are the use of extra sensors for the detection of malfunctioning episodes, the design of parallel multidetermination schemes to accelerate sample throughput, or the assembly of sensor arrays with cross-sensitivity features, which has led to what is referred to as electronic noses and tongues. According to the agreed International Union of Pure and Applied Chemistry (IUPAC) definition [1], an electronic tongue (ET) is “a multisensor system, consisting of a number of low-selective sensors using advanced mathematical procedures for signal processing based on pattern recognition and/or multivariate data analysis-artificial neural networks (ANNs), principal component analysis (PCA), etc.” The underlying motivation of ETs is different from the general trend, that is, to use low-selectivity sensors or with cross-response features, a prerequisite for the development of these biomimetic systems, outlined in Figure 13.1. In these ET systems, each sensor uses certain recognition element to differentiate the response. This can be different ionophores responsible for the potentiometric response, different metal electrodes responsible for different redox behavior, or different catalysts responsible for different voltammetric response. Many research papers are found along the ca. one-decade history of ETs that use sensors of different types, but a new class is emerging lately, which has received the name bioelectronic tongue (BioET); this specific type is characterized by including one or several biosensors into the sensor array. To be considered a biosensor, the sensor’s recognition element must be of biological origin, namely, enzymes, antigens, antibodies, nucleic acids, receptor proteins, cells, or even tissues. Our research group was pioneer in this variant, developing a BioET with voltammetric biosensors for glucose [2], another BioET with voltammetric biosensors for phenolic compounds [3], or also, a BioET employing potentiometric biosensors for the determination of urea [4].