Non-phytotoxic Zinc Based Nanoparticle Adjuvant for Improving Rainfastness and Sustained Release of Streptomycin

Abstract Antibiotic streptomycin has been extensively used for the treatment of bacterial infections in humans. Streptomycin is also used in agriculture to protect pome fruits from fire blight, a destructive bacterial disease. Recently, streptomycin sulfate (65.8 % A.I.) has been labeled for suppression of Huanglongbing in Florida, USA. The A.I. is water soluble and therefore suffers from poor rainfastness after foliar application. Due to high polarity, uptake and mobility of streptomycin sulfate through phloem vascular system is limited. Furthermore, streptomycin is prone to UV degradation when exposed to direct sunlight. Therefore, an efficient adjuvant is desired to improve rainfastness, UV-stability and vascular mobility. In this study, a novel non-phytotoxic zinc sulfide (ZnS) nanoparticle based adjuvant has been introduced that demonstrates improved rainfastness and sustained release of streptomycin. Antibacterial efficacy of streptomycin and the ZnS-streptomycin conjugate was found comparable when tested against model plant pathogenic bacteria (E. coli, X. alfalfae, and P. syringae).