Graphene oxide loaded with copper oxide nanoparticles as an antibacterial agent against Pseudomonas syringae pv. tomato

Abstract

Bacterial speck caused by Pseudomonas syringae pv. tomato (Pst) is a major disease of tomatoes. Infection by Pst in the seedling stage could cause 75% of total yield loss and quality losses in tomatoes. Applying massive chemical bactericides to control this disease has caused undesirable pathogen resistance, environmental pollution, and threats to humans. Here, we developed a candidate antibacterial agent made from copper oxide nanoparticles loaded onto the surfaces of graphene oxide sheets (GO–Cu NPs). A series of characterization measurements showed that the nanocomposite had been successfully prepared. Antibacterial activity results indicated that GO–Cu NPs had a 16-times higher antibacterial activity than Kocide 3000. From further investigation, the GO–Cu NPs composite could lead to damaging the cell structure, increasing the level of reactive oxygen species, and decreasing the content of DNA in Pst cells. From an in vivo test, GO–Cu NPs at 4 and 8 μg mL⁻¹ significantly reduced the severity of bacterial speck below 25% and the tomatoes had no phytotoxicity. Comparatively, 125 and 250 μg mL⁻¹ were required for Kocide 3000 to achieve similar effects. Therefore, GO–Cu NPs composites as a high-efficiency biocide have great potential for managing crop diseases.