Star Polymer Size, Charge Content, and Hydrophobicity Affect their Leaf Uptake and Translocation in Plants

Abstract

Determination of how the properties of nanocarriers of agrochemicals affect their uptake and translocation in plants would enable more efficient agent delivery. Here, we synthesized star polymer nanocarriers poly­(acrylic acid)-block-poly­(2-(methylsulfinyl)­ethyl acrylate) (PAA-b-PMSEA) and poly­(acrylic acid)-block-poly­((2-(methylsulfinyl)­ethyl acrylate)-co-(2-(methylthio)­ethyl acrylate)) (PAA-b-P­(MSEA-co-MTEA)) with well-controlled sizes (from 6 to 35 nm), negative charge content (from 17% to 83% PAA), and hydrophobicity and quantified their leaf uptake, phloem loading, and distribution in tomato (Solanum lycopersicum) plants 3 days after foliar application of 20 μL of a 1g L–1 star polymer solution. In spite of their property differences, ∼30% of the applied star polymers translocated to other plant organs, higher than uptake of conventional foliar applied agrochemicals (<5%). The property differences affected their distribution in the plant. The ∼6 nm star polymers exhibited 3 times higher transport to younger leaves than larger ones, while the ∼35 nm star polymer had over 2 times higher transport to roots than smaller ones, suggesting small star polymers favor symplastic unloading in young leaves, while larger polymers favor apoplastic unloading in roots. For the same sized star polymer, a smaller negative charge content (yielding ζ ∼ −12 mV) enhanced translocation to young leaves and roots, whereas a larger negative charge (ζ < −26 mV) had lower mobility. Hydrophobicity only affected leaf uptake pathways, but not translocation. This study can help design agrochemical nanocarriers for efficient foliar uptake and targeting to desired plant organs, which may decrease agrochemical use and environmental impacts of agriculture.

A nanocarrier pesticide delivery system with promising benefits in the case of dinotefuran: strikingly enhanced bioactivity and reduced pesticide residue

“…[4][5][6][7][8] Recently, a series of nanomaterials have been developed as carriers of synthetic/botanical pesticides and fertilizers. [9][10][11][12] The active ingredients (AIs) of most traditional pesticides are hydrophobic and can be encapsulated in or attached to the peripheral groups of nanoparticles, increasing the dispersion and affinity of pesticides and expanding the contact area of targets. [13][14][15] Thus, nanocarriers can reduce pesticide application, which is beneficial for reducing environmental pollution and negative effects on human health.…”

Zein and lignin-based nanoparticles as soybean seed treatment: translocation and impact on seed and plant health

“…The plant's mechanism of nanoparticle adsorption and absorption to enhance the efficacy of the entrapped agrochemicals is a popular topic of interest (Avellan et al 2021;Grillo et al 2021a). Previous studies have shown that these mechanisms are influenced by the particle's size (Cui et al 2008), charge (Hu et al 2020), and hydrophobicity (Sharma et al 2020;Zhang et al 2021). Research focusing on the foliar applications of pesticide entrapped nanoparticles is often conducted as these plant tissues are frequently exposed to pests and environmental conditions.…”

Polymer nanoparticles pass the plant interface

“…13 Foliar loading of small, charged star polymer nanoparticles has been studied, although most treatments included a surfactant wetting agent to combat the hydrophobicity of the plant cuticle and this is likely to have affected uptake and penetration. 37 Once inside the tissues, both symplastic (smaller particles) and apoplastic (larger particles) transport was reported for negatively-charged polymers.…”

“…This early burst of accumulation of nanoparticles might indicate that the plants are responding to the influx and reacting to eject or block entry as with the immune response to restrict viral distribution in plants 36 and as seen in leaf loaded tomato plants, whereby negatively-charged nanoparticles travelling down the plant in the phloem. 37 A low level of accumulation of neutral nanoparticles does continue giving rise to the signal in the xylem after 24 hours (Figure 5). No damage to the plants was observed.…”