Efficiency of biodegradable and pH-responsive polysuccinimide nanoparticles (PSI-NPs) as smart nanodelivery systems in grapefruit: in vitro cellular investigation

Authors: XIN, XIAOPING - University Of Florida; HE, ZHENLI - University Of Florida; HILL, MEGAN - University Of Florida; Niedz, Randall; JIIANG, XIANJUN - Southwest University; SUMERLIN, BRENT - University Of Florida

Submitted to: In Vitro Cellular and Developmental Biology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/16/2018
Publication Date: 6/13/2018
Citation: Xin, X., He, Z., Hill, M.R., Niedz, R.P., Jiiang, X., Sumerlin, B.S. 2018. Efficiency of biodegradable and pH-responsive polysuccinimide nanoparticles (PSI-NPs) as smart nanodelivery systems in grapefruit: in vitro cellular investigation. In Vitro Cellular and Developmental Biology. 18(7):e1800159. https://doi.org/10.1002/mabi.201800159.
DOI: https://doi.org/10.1002/mabi.201800159

Interpretive Summary: Huanglongbing (HLB), also called citrus greening disease, is thought to be caused by a bacteria that lives in the tree. The bacteria is spread tree-to-tree by the psyllid, an insect that feeds on citrus. Pesticides are now used to kill the psyllid but are not sufficiently effective to control psyllid populations. Another approach to treat HLB-infected citrus trees is to deliver molecules directly into the tree, but this requires an effective delivery system through the wood. Nanoparticles may be able to penetrate the wood and deliver attached compounds directly into the tree. This is called a smart delivery system. This study reports the delivery of nanoparticles directly into plant cells and the release of a compound that emits light. Grapefruit cells were incubated with nanoparticles and light was emitted (fluorescence) from grapefruit cells. This experiment demonstrated that the nanoparticles had entered the cells through the cell wall (wood) and released their light-emitting cargo, a necessary prerequisite for their application on whole plants.

Technical Abstract: Biodegradable pH-responsive polysuccinimide nanoparticles (PSI-NPs) are synthesized for directly delivering agrochemicals to plant phloem to improve their efficacy. The PSI-NPs have an average size of 20.6 nm with negative charge on the surface. The desired responsiveness to changes in pH is demonstrated by release efficiency of the model molecule (Coumarin 6), which increases with increasing pH over 24 hours. The internalization of PSI-NPs into grapefruit cells occurs in 10 min, and into nucleus in 2 hours, with most of the PSI-NPs being distributed in cytoplasm and nucleus. The proportion of PSI- NPs in plant cells significantly increases with time, from 19.1% at 10 min to 55.5% at 2 hours of administering. The PSI-NPs do not show significant inhibitory effects on soil microbial growth and activity. These results indicate that this smart nanodelivery system has potential of application in agriculture for mitigating phloem-limited diseases, such as citrus huanglongbing.