Lignin-Grafted-Poly(lactic- co -glycolic) Acid Nanoparticles as a Delivery System for CuS-C18 Nanoparticles Translocation inSoybean ( Glycine max ) and Lettuce ( Lactuca sativa )

Abstract Translocation of lignin-grafted poly(lactic-co-glycolic) acid (PLGA) nanoparticles (LNPs) and CuS-C18-loaded LNPs was investigated in hydroponically grown soybean (Glycine max) and lettuce (Lactuca sativa). Fluorescent polymer characterization using NMR and FTIR spectroscopy confirmed successful conjugation, and Rhodamine 640-labeled nanoparticles (F-LNPs) were synthesized and characterized for size, surface charge, and morphology. TEM imaging revealed that both F-LNPs and CuS-C18 F-LNPs exhibited spherical morphology. Particle tracking analysis indicated similar sizes for LNPs and F-LNPs, while CuS loading increased particle diameter from 96.5 to 110.6 nm. Rho640 release from LNPs in simulated apoplastic fluid (pH 5.5) was gradual, reaching ∼72% after 72 h. For translocation studies, soybean and lettuce plants were hydroponically exposed for 3 days to F-LNPs, with or without CuS-C18. Control groups included untreated plants, free Rho640, and empty LNPs. Fluorescence intensity and Cu/S content were quantified in plant tissues (soybean: roots, stems, and leaves; lettuce: roots and leaves) to evaluate nanoparticle uptake and transport. Fluorescence intensity was significantly higher in treated plants, particularly in roots, and confocal imaging further confirmed enhanced uptake and systemic distribution. Plants treated with CuS-C18-loaded F-LNPs showed greater Cu accumulation than those treated with unloaded F-LNPs, with concentrations decreasing from roots to leaves, consistent with root exposure pathways. These findings demonstrate that lignin-grafted PLGA nanoparticles can effectively deliver and transport CuS-C18 in multiple crop species. This delivery platform enables controlled release, reduces the need for high doses of free metal nanoparticles, and may lower environmental persistence and off-target risks, improving the sustainability of nano-enabled agricultural applications.