Targeted Delivery of Sucrose‐Coated Nanocarriers with Chemical Cargoes to the Plant Vasculature Enhances Long‐Distance Translocation

Abstract

Current practices for delivering agrochemicals are inefficient, with only a fraction reaching the intended targets in plants. The surfaces of nanocarriers are functionalized with sucrose, enabling rapid and efficient foliar delivery into the plant phloem, a vascular tissue that transports sugars, signaling molecules, and agrochemicals through the whole plant. The chemical affinity of sucrose molecules to sugar membrane transporters on the phloem cells enhances the uptake of sucrose‐coated quantum dots (sucQD) and biocompatible carbon dots with β‐cyclodextrin molecular baskets (suc‐β‐CD) that can carry a wide range of agrochemicals. The QD and CD fluorescence emission properties allowed detection and monitoring of rapid translocation (<40 min) in the vasculature of wheat leaves by confocal and epifluorescence microscopy. The suc‐β‐CDs more than doubled the delivery of chemical cargoes into the leaf vascular tissue. Inductively coupled plasma mass spectrometry (ICP‐MS) analysis showed that the fraction of sucQDs loaded into the phloem and transported to roots is over 6.8 times higher than unmodified QDs. The sucrose coating of nanoparticles approach enables unprecedented targeted delivery to roots with ≈70% of phloem‐loaded nanoparticles delivered to roots. The use of plant biorecognition molecules mediated delivery provides an efficient approach for guiding nanocarriers containing agrochemicals to the plant vasculature and whole plants.

Critical Review: Uptake and Translocation of Organic Nanodelivery Vehicles in Plants

“…64 Surface chemistry was also shown to be an important factor in the uptake and subsequent translocation of sugar-coated inorganic quantum dots (QDs). 116 One day after foliar exposure to wheat plants, 9.5% of sucrose-coated QDs (∼18 nm, −45 mV) reached the roots, compared to 1.4% of unfunctionalized QD (∼15 nm, −55 mV), suggesting enhanced phloem loading and transport, possibly due to the high affinity of sugars to sucrose transporter membrane proteins (SUT) in the phloem. 116 To date, no organic NDVs with sugar coating or functionalization have been studied.…”

“…116 One day after foliar exposure to wheat plants, 9.5% of sucrose-coated QDs (∼18 nm, −45 mV) reached the roots, compared to 1.4% of unfunctionalized QD (∼15 nm, −55 mV), suggesting enhanced phloem loading and transport, possibly due to the high affinity of sugars to sucrose transporter membrane proteins (SUT) in the phloem. 116 To date, no organic NDVs with sugar coating or functionalization have been studied. Given the active nature of sugar transport in plants, investigating the uptake and subsequent translocation of foliarly delivered sugar-coated organic NDVs could generate promising results.…”

“…120 Using X-ray fluorescence (XRF), Gd-loaded, sucrosecoated carbon dots (20 nm, − 30 mV) were found colocalized with potassium ions, a major cation present in phloem sap, suggesting phloem loading and transport of these inorganic NDVs in wheat. 116 Inorganic NDVs ranging in size from 8 to 150 nm have been visualized within cells, 132−138 having crossed the cell wall, which reportedly has pores ranging from 2 to 5 nm. 132,139 The ability of NDVs larger than cell wall pores to move through the apoplast is likely a consequence of chemical modifications on the cell wall induced by the NDVs.…”

“…A systematic study evaluating the effect of several different organic NDV surface properties on their translocation in tomato plants following foliar application provided additional evidence for this claim, with slightly anionic (−10 mV) HPMCAS-coated NDVs exhibiting much higher translocation efficiency (∼32%) than either a cationic (+38 mV) PDMAEMA-coated NDV (∼10%) or a more anionic (−40 mV) PAA-coated NDV (∼12%) . Surface chemistry was also shown to be an important factor in the uptake and subsequent translocation of sugar-coated inorganic quantum dots (QDs) . One day after foliar exposure to wheat plants, 9.5% of sucrose-coated QDs (∼18 nm, −45 mV) reached the roots, compared to 1.4% of unfunctionalized QD (∼15 nm, −55 mV), suggesting enhanced phloem loading and transport, possibly due to the high affinity of sugars to sucrose transporter membrane proteins (SUT) in the phloem .…”

“…Gold nanoparticles (AuNPs) measuring 15–50 nm were shown to accumulate on plasmodesmata of sieve tube elements and companion cells of poplar roots, suggesting symplastic movement via the endoplasmic reticulum continuum between cells . Using X-ray fluorescence (XRF), Gd-loaded, sucrose-coated carbon dots (20 nm, – 30 mV) were found colocalized with potassium ions, a major cation present in phloem sap, suggesting phloem loading and transport of these inorganic NDVs in wheat …”