Cell-Based Odorant Sensor Array for Odor Discrimination Based on Insect Odorant Receptors

Abstract

The olfactory system of living organisms can accurately discriminate numerous odors by recognizing the pattern of activation of several odorant receptors (ORs). Thus, development of an odorant sensor array based on multiple ORs presents the possibility of mimicking biological odor discrimination mechanisms. Recently, we developed novel odorant sensor elements with high sensitivity and selectivity based on insect OR-expressing Sf21 cells that respond to target odorants by displaying increased fluorescence intensity. Here we introduce the development of an odorant sensor array composed of several Sf21 cell lines expressing different ORs. In this study, an array pattern of four cell lines expressing Or13a, Or56a, BmOR1, and BmOR3 was successfully created using a patterned polydimethylsiloxane film template and cell-immobilizing reagents, termed biocompatible anchor for membrane (BAM). We demonstrated that BAM could create a clear pattern of Sf21 sensor cells without impacting their odorant-sensing performance. Our sensor array showed odorant-specific response patterns toward both odorant mixtures and single odorant stimuli, allowing us to visualize the presence of 1-octen-3-ol, geosmin, bombykol, and bombykal as an increased fluorescence intensity in the region of Or13a, Or56a, BmOR1, and BmOR3 cell lines, respectively. Therefore, we successfully developed a new methodology for creating a cell-based odorant sensor array that enables us to discriminate multiple target odorants. Our method might be expanded into the development of an odorant sensor capable of detecting a large range of environmental odorants that might become a promising tool used in various applications including the study of insect semiochemicals and food contamination.

Increasing cell–device adherence using cultured insect cells for receptor-based biosensors

“…We used Sf21 cells and Sf21 cells expressing insect ORs with OR co-receptors and fluorescent calcium indicator proteins (GCaMP6s) [ 6 ]. A bright-field microscopy image of Sf21 cells on a plastic cell-culture dish is shown in figure 1 c .…”

“…We proposed a new bio-hybrid electronic odorant sensor, termed the odour-sensitive field-effect transistor (OSFET) [ 3 ], based on extended-gate FETs with thin Al 2 O 3 layers and Sf21 insect cells derived from pupal ovarian tissues of Spodoptera frugiperda [ 4 ] expressing insect ORs. Sf21 cells with insect ORs act as odorant sensor elements [ 5 , 6 ]; simply attaching them to extended-gate electrodes allowed the sensors to discriminate between two structurally similar odorants by electrical signals.…”

The Emergence of Insect Odorant Receptor-Based Biosensors

“…In order to overcome the cumbersome setup of cell-based sensors, portable fluidic devices have been developed [31] and the cell transducer interface has been studied resulting in increased adherence [32]. Recently, a cell-based odorant sensor array has demonstrated prolonged lifespan by using a specific biocompatible membrane anchoring reagent patterned on Polydimethylsiloxane (PDMS) [33]. The feasibility of the detection of multiple odorants was demonstrated by patterning different sf21 cell lines expressing various insect ORs spatially separated and fluorescently tagged (with a fluorescent calcium indicator).…”

Membrane protein-based biosensors

“…The long lifespan of this cellular system demonstrates a breakthrough for cell-based odorant sensing technology. Using the same Sf21 cells mentioned above, this research group also produced other olfactory receptors (Or13a and Or56a derived from Drosophila melanogaster) and demonstrated the detection of four kinds of chemicals (bombykol, bombykal, octenol and geosmin) [98]. They regionally immobilized each Sf21 cell group expressing each receptor to four regions on a modified glass substrate and measured the cell responses by fluorescent observation of GCaMP6s in a single visual field ( figure 8).…”