A pheromone receptor-based diamond biosensor for the detection of the invasive fall armyworm Spodoptera frugiperda

The fall armyworm, Spodoptera frugiperda, is a major lepidopteran crop pest belonging to the family Noctuidae. Native of America, it has spread extensively in recent years across Africa, Asia, Oceania, and more recently in Europe. In this context, we present a biosensing strategy for the in-field early detection of this highly invasive species. The approach lies in the development of a highly sensitive and selective biosensor targeting (Z)-9-tetradecenyl acetate (Z9-14:Ac), the major component of the sex pheromone of S. frugiperda. The biosensor combines a diamond membrane transducer, with S. frugiperda’s olfactory receptor SfruOR13 as sensitive biorecognition element. The transducer exploits both the outstanding mechanical properties of diamond, and the carbon-based nature of the membrane, enabling reliable surface immobilization of bioreceptors. Diamond membranes with 1000 µm diameters and ~ 3µm thickness were produced in the cleanroom on 4 inches silicon wafers. Their resonance frequencies were determined by calculation, simulation and experimentally both in air (~100 kHz) and phosphate buffer saline (PBS) solution (~50 kHz). SfruOR13 was expressed and stabilized in nanodiscs before being electrochemically grafted on the boron doped diamond surface of the membranes. The sensors showed linear response in PBS to Z9-14:Ac across a concentration range 0 – 1 pM with a typical sensitivity as high as 87 mHz.fM-1, and achieved a limit of detection of 8.4 fM. The response was highly selective, partially reversible, and fairly stable over 29 days. Ultimately, this biosensor could serve as an autonomous early pest detection tool, contributing to more sustainable and pesticide-free agriculture.