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Global warming and sea level rise are serious threats to agriculture. The negative effects caused by severe salinity include discoloration and reduced surface of the leaves, as well as wilting due to an impaired uptake of water from the soil by roots. Nanotechnology is emerging as a valuable ally in agriculture: several studies have indeed already proven the role of silicon nanoparticles in ameliorating the conditions of plants subjected to (a) biotic stressors. Here, we introduce the concept of phyto-courier: hydrolyzable nanoparticles of porous silicon, stabilized with the nonreducing saccharide trehalose and containing different combinations of lipids and/or amino acids, were used as vehicle for the delivery of the bioactive compound quercetin to the leaves of salt-stressed hemp (Cannabis sativa L., Santhica 27). Hemp was used as a representative model of an economically important crop with multiple uses. Quercetin is an antioxidant known to scavenge reactive oxygen species in cells. Four different silicon-based formulations were administered via spraying in order to investigate their ability to improve the plant’s stress response, thereby acting as nano-biostimulants. We show that two formulations proved to be effective at decreasing stress symptoms by modulating the amount of soluble sugars and the expression of genes that are markers of stress-response in hemp. The study proves the suitability of the phyto-courier technology for agricultural applications aimed at crop protection.

Salinity is a form of abiotic stress that impacts growth and development in several economically relevant crops and is a top-ranking threat to agriculture, considering the average rise in the sea level caused by global warming. Tomato is moderately sensitive to salinity and shows adaptive mechanisms to this abiotic stressor. A case study on the dwarf tomato model Micro-Tom is here presented in which the response to salt stress (NaCl 200 mM) was investigated to shed light on the changes occurring at the expression level in genes involved in cell wall-related processes, phenylpropanoid pathway, stress response, volatiles’ emission and secondary metabolites’ production. In particular, the response was analyzed by sampling older/younger leaflets positioned at different stem heights (top and bottom of the stem) and locations along the rachis (terminal and lateral) with the goal of identifying the most responsive one(s). Tomato plants cv. Micro-Tom responded to increasing concentrations of NaCl (0-100-200-400 mM) by reducing the leaf biomass, stem diameter and height. Microscopy revealed stronger effects on leaves sampled at the bottom and the expression analysis identified clusters of genes expressed preferentially in older or younger leaflets. Stress-related genes displayed a stronger induction in lateral leaflets sampled at the bottom. In conclusion, in tomato cv. Micro-Tom subjected to salt stress, the bottom leaflets showed stronger stress signs and response, while top leaflets were less impacted by the abiotic stressor and had an increased expression of cell wall-related genes involved in expansion.

The search for more effective methods to alleviate the negative effects of exogenous stresses in plants has inspired nanotechnologies. It is in this context that the use of formulations containing nanoporous silicon-stabilized hybrid lipid nanoparticles acting as delivery systems of the flavonoid quercetin was investigated here. These formulations, referred to as phyto-couriers, proved their efficacy in protecting the important crop model Solanum lycopersicum "Micro-Tom" against salinity. Two phyto-courier formulations, GS1 and GS3, functionalized with 25 mg of quercetin and differing in the presence of trehalose were applied to salt-stressed tomato by foliar spraying. The shape and ordered structure of the palisade cells was completely compromised under salinity; however, the phyto-couriers preserved their elongated shape under abiotic stress. From a molecular point of view, some stress-responsive genes tended to decrease in expression in stressed leaves treated with the phytocouriers. Shotgun proteomics confirmed the nano-biostimulant nature of the formulations: several proteins involved in cytoprotection against oxidative stress were more abundant in control leaves treated with the phyto-couriers. Proteins involved in chromatin remodeling were also more abundant in control leaves treated with the trehalose-containing GS3 formulation, a finding indicating a priming effect. Overall, the formulations showed promising results to enhance abiotic stress tolerance in a crop model through the mitigation of stress symptoms. The results presented proof of the stress-relieving properties of the silicon-stabilized hybrid lipid nanoparticles and are a proof-of-concept for the use of the phyto-courier nanotechnology in horticultural applications.

Drug delivery to the eye remains a real challenge due to the presence of ocular anatomical barriers and physiological protective mechanisms. The lack of effective siRNA delivery mechanism has hampered the real potential of RNAi therapy, but recent literature suggests that nanocarrier systems show great promise in enhancing siRNA bioavailability and reducing the need for repeated intraocular injections. A diverse range of materials are under exploration worldwide, including natural and synthetic polymers, liposomes, peptides, and dendrimeric nanomaterials. This chapter describes a simple workflow for feasibility assessment of a proposed ocular surface siRNA delivery system. Gel retardation assay is used for investigation of optimal siRNA to carrier loading ratio. Fluorescent siRNA allows for initial in vitro testing of cellular uptake to corneal epithelial cells and investigation of in vivo siRNA delivery into mouse cornea by live animal imaging and fluorescence microscopy.