When Sustainable Nanochemistry Meets Agriculture: Lignin Nanocapsules for Bioactive Compound Delivery to Plantlets

First developed for biomedical and industrial applications, nanovectors have recently been extended to agriculture. Therefore, innovative plant-growing procedures making use of nanoparticles should be adapted to sustainable processes and materials. This work aims at proposing newly synthetized polymeric nanocapsules (NCs) to be used as biocompatible vectors for delivery of bioactive compounds to plants. Nanoparticles were fabricated from lignin, which is the main byproduct of wood processing and is currently a waste material. Lignin can thus find a virtuous fate and be reused in the context of circular economy. Specifically, we loaded lignin NCs with gibberellic acid (GA), assessing that stable and reproducible nanoparticles could be obtained in a range of the GA content that is relevant for delivery purposes, that is, 0.5-1.5 mg mL-1. Plain and GA-loaded NCs were characterized by dynamic light scattering and scanning electron microscopy. Assays of cytotoxicity and cargo release were carried out in two model plants, Eruca vesicaria and Solanum lycopersicum. These experiments, conducted both in vitro and in vivo, included the investigations of the percentage of germination, the stem, and primary root lengths, as well as the fresh and dry weight of treated plants versus nontreated ones. Furthermore, NCs were loaded with Fluorol Yellow 088 to track their entrance and accumulation in seeds and seedlings.