The Porcine Odorant-Binding Protein as a Probe for an Impedenziometric-Based Detection of Benzene in the Environment

Abstract

Odorant-binding proteins (OBPs) are a group of small and soluble proteins present in both vertebrates and insects. They have a high level of structural stability and bind to a large spectrum of odorant molecules. In the environmental field, benzene is the most dangerous compound among the class of pollutants named BTEX (benzene, toluene, ethylbenzene, and xylene). It has several effects on human health and, consequently, it appears to be important to monitor its presence in the environment. Commonly, its detection requires the use of very sophisticated and time-consuming analytical techniques (GC-MS, etc.) as well as the presence of specialized personnel. Here, we present the application of an odorant-binding protein (pOBP) isolated from pigs as a molecular recognition element (MRE) for a low-energy impedenziometric biosensor for outdoor and real-time benzene detection. The obtained results show that the biosensor can detect the presence of 64 pM (5 µg/m³) benzene, the limit value of exposure for human health set by the European Directive 2008/50/EC.

Keywords: VOCs; benzene; biosensors; odorant-binding protein (OBP).

Figure 1

Gas sensor. Photo (on top) and scheme of sensing area (on bottom) of the gas sensor prototypes with a gold-plated IDE at 200 µm (a) and 75 µm (b).

Figure 2

Schematic representation of surface derivatization and functionalization process. The gold surface derivatized with α-lipoic acid (a) was treated sequentially with a mixture of EDC/NHS (b), and then with a solution of pOBP (c) or GlnBP (d).

Figure 3

Sensor measurements in solution. Variation of the voltage in the absence (dry, water, and ethanol) and in the presence of different concentrations of benzene (64 pM and 1.2 µM) by using the 200 µm sensor chip.

Figure 4

Gas test chamber. Schematic representation of the test chamber (a); real picture of the realized and used test chamber (b).

Figure 5

Variation of the voltage value in the absence (nitrogen and ethanol) and in the presence of different concentrations of benzene (from 64 pM to 1.2 µM). The measurements were acquired in gas at room temperature by using the 200 µm sensor chip.

Figure 6

Variation of the voltage in the absence (nitrogen and ethanol) and in the presence of different concentrations of benzene (from 64 pM to 1.2 µM). The measurements were acquired in gas at room temperature by using the 75 µm sensor chip configuration.

Figure 7

Variation of the voltage, during the time (5 h) in the absence (nitrogen) and in the presence of gasoline and exhausted oil vapor. The measurements were acquired in gas, at room temperature by using the 75 µm sensor chip configuration.