Functional Nanovesicle-Embedded Hydrogel Biosensors for the Real-Time Monitoring of Queen Mandibular Pheromone in Both Aqueous and Gaseous Environments.

Monitoring of the presence of a queen bee in hives is essential for the sustainability of healthy honey bee colonies. However, most beekeepers have relied on manual and visual inspections to assess the queen presence in a hive, which is not suitable for early diagnosis of queen loss. In this study, a functional nanovesicle-embedded hydrogel biosensor platform is developed for the real-time and direct monitoring of 9-oxo-2-decenoic acid (9-ODA), a main component of the queen mandibular pheromone, in both liquid- and gas-phase environments. Here, a black phosphorus-based field-effect transistor (BP-FET) was hybridized with nanovesicles containing Apis mellifera olfactory receptor 11 (AmOr11) recognizing 9-ODA to build a highly sensitive sensing platform. Then, a polyacrylamide hydrogel layer was coated on the channel region of the BP-FET, which could inhibit the nonspecific adsorption of macromolecules and provide excellent physiological environments to maintain the functional activities of receptors. Our nanovesicle-embedded hydrogel biosensor could be utilized for the real-time detection of 9-ODA down to 1 aM and 8.16 parts per trillion (ppt) in aqueous and gaseous environments, respectively. Moreover, our sensor could discriminate 9-ODA from other pheromone-related odorants in both liquid- and gas-phase environments with high selectivity. Furthermore, it could detect 9-ODA even in complicated environments, such as propolis and Apimil samples. Notably, our platform allowed us to sensitively monitor 9-ODA secreted by a live queen bee in real time. In this respect, our nanovesicle-embedded hydrogel biosensor could provide a promising platform for on-site assessment of queen presence and versatile practical applications in agricultural industries.