Targeted delivery of oxytetracycline to the epidermal cell junction and stomata for crop protection

Abstract

Scalable targeted delivery methods are urgently needed for crop protection in modern agriculture. Herein, we report on the use of a novel borate-zinc nanoformulation (Bz) for the targeted delivery of Oxytetracycline (OTC). Fluorescence spectroscopy demonstrated the formation of the OTC–Zn complex when Bz is tank-mixed with OTC. Scanning electron microscopy (SEM) studies confirm that OTC changes the morphology of Bz residue after desiccation. SEM study was conducted on peach saplings with three different antimicrobial treatments, Bz, OTC and Bz–OTC. Results revealed that Bz alone or in combination with OTC preferentially deposited in the junction between epidermal cells as well as around the stomata. Fluorescence microscopy also confirmed that OTC was preferentially deposited in the same areas. In contrast, the OTC treatment produced sessile drop patterns with no special affinity for any leaf structures. Antimicrobial studies were conducted on OTC-resistant and OTC-sensitive Xanthomonas arboricola pv. pruni strain (XAP) strains. Results demonstrated moderate synergistic antimicrobial activity of Bz–OTC against the OTC-sensitive XAP strain and no loss in activity against the OTC-resistant XAP strain. To the best of our knowledge, this is the first report of targeted delivery of OTC to the epidermal cell junction and stomata using a micronutrient-based nanosystem.