Discrete and Continuous Odor Quantification in Gas-Phase Odor Biosensor

Abstract

Cells expressing heterologous olfactory receptors were commonly used as the sensing elements in odor biosensors owing to their high sensitivity and selectivity. However, The odor quantification performance of these biosensors especially in speed and accuracy aspects is not so favorable yet. To overcome this problem, we proposed discrete and continuous odor quantification. In this study, two olfactory receptors, Or13a and Or56a, and their agonists, 1-octen-3-ol and geosmin were used. The cell images were handled online to accelerate the processing speed. The odor intensity that we intended to quantify was the target odor, the odor intensity that we provided was the generated odor. The target and generated odors were repeatedly applied thus mitigating the sensor drift and aging influence. The target odor quantification outcome could be one of several discrete candidates (discrete quantification) or a continuous value computed based on the standard response curve (continuous quantification). We first obtained the typical results of the discrete and continuous quantification methods using single OR. After this, we executed the experiments in multiple target odor intensities and made a comparison between two methods. Discrete quantification was simpler while continuous quantification was faster and more accurate. In addition, both methods were tested under binary odor mixture conditions and their quantification results were satisfactory. The methods proposed here will benefit the on-site precise quantification of odor biosensors.