Design and test of a biosensor-based multisensorial system: a proof of concept study

Abstract

Sensors are often organized in multidimensional systems or networks for particular applications. This is facilitated by the large improvements in the miniaturization process, power consumption reduction and data analysis techniques nowadays possible. Such sensors are frequently organized in multidimensional arrays oriented to the realization of artificial sensorial systems mimicking the mechanisms of human senses. Instruments that make use of these sensors are frequently employed in the fields of medicine and food science. Among them, the so-called electronic nose and tongue are becoming more and more popular. In this paper an innovative multisensorial system based on sensing materials of biological origin is illustrated. Anthocyanins are exploited here as chemical interactive materials for both quartz microbalance (QMB) transducers used as gas sensors and for electrodes used as liquid electrochemical sensors. The optical properties of anthocyanins are well established and widely used, but they have never been exploited as sensing materials for both gas and liquid sensors in non-optical applications. By using the same set of selected anthocyanins an integrated system has been realized, which includes a gas sensor array based on QMB and a sensor array for liquids made up of suitable Ion Sensitive Electrodes (ISEs). The arrays are also monitored from an optical point of view. This embedded system, is intended to mimic the working principles of the nose, tongue and eyes. We call this setup BIONOTE (for BIOsensor-based multisensorial system for mimicking NOse, Tongue and Eyes). The complete design, fabrication and calibration processes of the BIONOTE system are described herein, and a number of preliminary results are discussed. These results are relative to: (a) the characterization of the optical properties of the tested materials; (b) the performance of the whole system as gas sensor array with respect to ethanol, hexane and isopropyl alcohol detection (concentration range 0.1-7 ppm) and as a liquid sensor array (concentration range 73-98 μM).

Figure 1.

Electronic interface for liquid sensor system. The input signal is a triangular function. The output signal is measured by the working electrode and transduced in an output current by an opportune converter.

Figure 2.

Calibration curves of S1 and S2 (QMB sensors) for three compounds: ethanol, hexane and isopropanol.

Figure 3.

The voltage modulation applied to the liquid sensor provides in each time a value of current. The peaks of current are referred to different redox processes. All the current responses represent an electrochemical pattern of the sample (each marker corresponds to a different specimen). The scores plot obtained from a PCA model built on the collected data shows different clusters for different compounds.

Figure 4.

Optical spectra of different sensing materials in different conditions. The wavelength at which the anthocyanin chromophore shows the maximum absorbance in the pH 1.0 solution is 520 nm. The optical stability of sensing material (hortensia panel (A), rose panel (B), cabbage panel (C)) has been monitored for a period of 14 days at different temperatures (room temperature (RT), 4 °C and 40 °C).

Figure 5.

HPLC-UV/Vis chromatograms acquired at 520 nm of (A) blue hortensia, (B) red rose and (C) red cabbage anthocyanins extracts.

Figure 6.

Concept design of a system composed of three parts: optical transduction, liquid sensors and gas sensors array. The sample under test could be contemporaneously analyzed by the three techniques.

Figure 7.

The liquid sensors have been calibrated to different solutions of water with addition of hexane, ethanol, isopropanol (Left). The score plot obtained by the principal component analysis model shows a discrimination of the mixtures (Right).