Protein- and Peptide-Based Biosensors in Artificial Olfaction

Abstract

Animals' olfactory systems rely on proteins, olfactory receptors (ORs) and odorant-binding proteins (OBPs), as their native sensing units to detect odours. Recent advances demonstrate that these proteins can also be employed as molecular recognition units in gas-phase biosensors. In addition, the interactions between odorant molecules and ORs or OBPs are a source of inspiration for designing peptides with tunable odorant selectivity. We review recent progress in gas biosensors employing biological units (ORs, OBPs, and peptides) in light of future developments in artificial olfaction, emphasizing examples where biological components have been employed to detect gas-phase analytes.

Keywords: Volatile organic compounds; artificial olfaction; biosensor; odorant-binding protein; olfactory receptor; peptide.

Figure I. Structural Features of Odor-Sensing Proteins and Peptides.

Figure 1. Scheme of Main Constituents of Protein and Peptide-Based Biosensors for Artificial Olfaction.

A bioreceptor known to bind to volatile organic compounds (VOCs) – olfactory receptors, odorant binding proteins or VOC affinity peptides – is selected for immobilization. Surface immobilization can be made through different methods including affinity, covalent spacers, and thiol-based chemistry. The biosensor is then applied in a signal transducing system which may be, for example, electrical, gravimetric, or optical. The collected data is finally processed to yield qualitative or quantitative information about target VOCs.

Figure 2

Key Figure Protein and Peptide Discovery and Engineering for Gas Sensing For a Figure360 author presentation of Figure 2, see the figure legend at https://doi.org/10.1016/j.tibtech.2018.07.004. For a Figure360 author presentation of Figure 2, see the figure legend at https://doi.org/10.1016/j.tibtech.2018.07.004. (A) Superimposition of the binding pockets of bovine and porcine odorant-binding proteins (OBPs) reveals how small differences in residue composition lead to different volatile organic compound (VOC) affinities [51]. (B) The extraction of volatile binding sequence from the fruit fly OBP LUSH, as a way to rationally develop peptides for VOC detection [62,63]. (C) Phage-display panning screens a multitude of peptide sequences against a graphitic surface mimicking benzene [68]. (D) Computational techniques predict the best peptide–VOC pairs to be experimentally tested [70].