Abstract
Delivering active ingredients with high antibacterial efficacy at infected sites in plants is essential to reach global goals for food security and sustainable agriculture productivity. Engineering nanomaterials is a suggested approach to attain systemic delivery of antibacterial active ingredients, thereby improving the treatment efficacy and minimizing harmful effects related to leaching in the environment. Herein, surface defect engineering of nanotherapeutics is used as a new form of active ingredient for systemic antimicrobial action in the phloem. The nanoparticle-based formulation, called Zinkicide®, features a spherical particle composed of a zinc oxide (ZnO) core and zinc peroxide (ZnO2) shell with a total diameter below 5 nm. This formulation exhibits significant efficacy to manage citrus huanglongbing (HLB) disease as seen by the decrease in severity of symptoms and the increase from ∼7% to 19% of medium and large fruits in HLB infected citrus groves, during field trials. Further analysis of the bacterial responses to Zinkicide® in situ indicates high potency at a concentration as low as 9-18 μg mL−1 and biofilm growth inhibition at a concentration of 50 μg mL−1. Nanoscale infrared spectroscopy reveals morphology and secondary structure changes of the bacterial membrane upon treatment. The origin of the changes is considered, based on the optical signatures of the nanoparticles, indicative of surface defects. These inform a theoretical description of the participation of a ZnO2/ZnO surface containing a pair of missing O atoms in the production of reactive oxygen species (ROS). The key participation of defects in the antibacterial action is confirmed experimentally by the slow decrease in antibacterial efficacy as nanoparticles age in media with passivation effects on the surface. This study reveals the importance of size of the nanoparticle and nature of surface defects in the design of nanotherapeutics for targeted delivery and antibacterial activity.
| Original language | English |
|---|---|
| Pages (from-to) | 2869-2886 |
| Number of pages | 18 |
| Journal | Environmental Science: Nano |
| Volume | 9 |
| Issue number | 8 |
| DOIs | |
| State | Published - Jul 7 2022 |
Funding
The authors acknowledge the support of the National Institute of Food and Agriculture, U.S. Department of Agriculture, under award number USDA Grant 2015-70016-23010 and the Citrus Research and Development Foundation (project # 907) for this study. This research used resources of CADES at the Oak Ridge National Laboratory, which is supported by the Office of Science of the U.S. Department of Energy under Contract No. DE-AC05-00OR22725, and at the High Flux Isotope, a DOE Office of Science User Facility operated by the Oak Ridge National Laboratory. M. Soliman and B. Lee contributed equally to this work. A. Ozcan and T. B. Rawal contributed equally to this work. A. Ozcan acknowledges current affiliation, Vocational School of Technical Sciences, Karamanoglu Mehmetbey University, Karaman, 70200, Turkey. T. B. Rawal acknowledges current affiliation, Department of Physics, University of Houston, Houston, TX, 77204.
