Effects of the physical state of nanocarriers on their penetration into the root and upward transportation to the stem of soybean plants using confocal laser scanning microscopy

• Three types of nanocarriers were prepared using a combined method of homogenization and sonication.
• Their characteristics were nearly similar, but the physical state of lipid matrix differed.
• Three types of nanocarriers could penetrate into root and transport upward from root to stem.
• Penetration and transportation of NE were faster than NLC and SLN because of its higher flexibility.
• This study supplies a basic background to generate a new generation of pesticide formulations.

We determined whether nanocarriers can penetrate into plant roots and be transported upward, from the root to stem, as well as studied the effect of the physical state of the lipid matrix of the nanocarriers on their penetration and transportation in plants. Firstly, solid lipid nanoparticles (SLN), nanostructured lipid carriers (NLC), and lipid-based nanoemulsions (NE) with similar characteristics (particle size, polydispersity index, and zeta potential) were successfully prepared by the combined method of hot homogenization and sonication, with beeswax as a solid lipid, corn oil as a liquid lipid, and Nile Red as a fluorescent active-ingredient. Penetration of nanocarriers into the roots and their transportation to the stem were visualized using confocal laser scanning microscopy. The images of vertical sections illustrated that NE penetrated into the root and was transported upward at a rate faster than did NLC and SLN, because of its relatively higher flexibility. While it took only 1 day for NE to penetrate into the center of the root and be transported upward to up to 4 cm of the stem, it took 3 and 6 days, respectively, for NLC and SLN to achieve the same. This study provides an important basic background required to generate a new generation of pesticide formulations, where pesticides will be encapsulated in nanocarriers, which in turn will be embedded into a patch that will be stuck on the root or stem. This would minimize pesticide loss, resulting in higher commercial profit and better environmental protection.