A new method for the direct tracking of in vivo lignin nanocapsules in Eragrostis tef (Poaceae) tissues

Abstract

Environmental concerns have driven scientists to research new eco-friendly approaches for the preparation of nanosystems. For this purpose, novel bio-polymers have been selected. Among these, one of the most promising is lignin, which is biodegradable and biocompatible. Additionally, lignin is one of the main by-products of the paper industry and can be re-used in nanosystems building. Lignin-based nanosystems could be used in agriculture, to improve the uptake of bioactive compounds, thus avoiding soil pollution. However, the mechanism of penetration in the plant and the route of transportation within the internal plant tissues are unknown and need to be clearly elucidated. Here we present a method of lignin nanocapsules staining and tracking by fluorochrome: Fluoral Yellow 088, which is a well-suited dye for the tracking of lipids and other oil phases. Two different applications were applied: in the first one fourteen-day plants were soaked with fluorescent nanocapsules (fNCs) pure solution and in the second one, Eragrostis tef plants were laid down on blotting paper and soaked with diluted fNCs solution. Wetting the roots of Teff plantlets with the pure fNCs solution resulted in the most efficient way of nanocapsule entrance. The dyeing of lignin nanocapsules allowed us to track them in Eragrostis tef plant tissues through microscopic observations. In particular, fNCs were proven to be able to permeate roots, reaching xylem vessels where, through water pressure, they reached the leaf.

Figure 1.

Scheme of fluorescent nanocapsule preparation.

Figure 2.

A) Eragrostis tef seedlings in germination dish. B) The two methods of fNC administration to Eragrostis tef seedlings.

Figure 3.

Fluorescence image of lignin nanocapsules loaded with FY088.

Figure 4.

A) Images of a longitudinal sections of Teff leaf. B) Longitudinal section of root. C) Teff leaf without treatment. D) Longitudinal sections of Teff root without treatment, only autofluorescence; E) Teff leaf after 24 h treatment in pure NCs (some indicated with arrows) loaded with FY088. F) Teff root after 24 h treatment in pure NCs loaded with FY088; many NCs are lining the xylem walls (arrows). G) Teff leaf after 24 h treatment on blotting paper soaked with NCs (some indicated with arrows) loaded with FY088. H) Teff root after 24 h treatment in blotting paper soaked with NCs (some indicated with arrows) loaded with FY088.