The main challenges in drug delivery systems are to protect, transport and release biologically active compounds at the right time in a safe and reproducible manner, usually at a specific target site. In the past, drug nano-carriers have contributed to the development of precision medicine and to a lesser extent have focused on its inroads in agriculture. The concept of engineered nano-carriers may be a promising route to address confounding challenges in agriculture that could perhaps lead to an increase in crop production while reducing the environmental impact associated with crop protection and food production. The main objective of this review is to contrast the advantages and disadvantages of different types of nanoparticles and nano-carriers currently used in the biomedical field along with their fabrication methods to discuss the potential use of these technologies at a larger scale in agriculture. Here we explain what is the problem that nano-delivery systems intent to solve as a technological platform and describe the benefits this technology has brought to medicine. Also here we highlight the potential drawbacks that this technology may face during its translation to agricultural applications, based on the lessons learned so far from its use for biomedical purposes. We discuss not only the characteristics of an ideal nano-delivery system, but also the potential constraints regarding the fabrication including technical, environmental, and legal aspects. A key motivation is to evaluate the potential use of these systems in agriculture, especially in the area of plant breeding, growth promotion, disease control, and post-harvest quality control. Further, we highlight the importance of a rational design of nano-carriers and identify current research gaps to enable scale-up relevant to applications in the treatment of plant diseases, controlled release of fertilizers, and plant breeding.

Botrytis cinerea, a broad host-range necrotrophic (BHN) phytopathogen, establishes compatible interactions with hosts by deploying multigene infection strategies, rendering simply inherited resistance ineffective to fight off this pathogen. Since essential oils (EOs) serve as intermediators during phytobiome communication, we hypothesize that they have the potential to enhance the quantitative disease resistance against BHN by eliciting the adaptive stress response (hormesis) in plants. However, using EOs is challenging due to their poor solubility in water. Nanoemulsification of EOs enhances not only the solubility of EOs but also their potency and stability. Here, we demonstrate the potential use of essential oil nanoemulsions (EONEs) to control infections caused by BHN. Using basic engineering principles of nanocarrier design, we demonstrate the efficacy of a robust EONEs design for controlling B. cinerea infection in a model plant, Arabidopsis thaliana. Our nanoemulsion delivery system significantly enhanced the disease resistance of the host by reducing the necrotic area by up to 50% compared to untreated plants. RNA-seq analysis indicated that successful treatments upregulated autophagy, ROS scavenging, and activation of the jasmonic acid signaling pathway.

Chitosan and D-limonene are bioactive molecules derived from organic waste. We repurposed them in the form of a drug delivery system for agricultural applications in crop protection to combatBotrytis cinerea, a broad host-range necrotrophic (BHN) pathogen that causes economic losses worldwide. Synthetic fungicide application remains the most common method to control this pathogen, but this comes with a significant environmental cost. Drug delivery systems from naturally occurring biomaterials can offer efficient treatment options to combat this pathogen. We hypothesized that engineered chitosan nanoparticles (CSNPs) loaded with D-limonene can trigger an ondemand systemic defense response in plants that enhances its quantitative disease resistance against BHN. Chitosan nanocarriers encapsulated with D-limonene as cargo were fabricated through a rational formulation via ionic gelation and the spontaneous emulsification method, respectively, to produce chitosan D-limonene nanoparticles (CdlNPs). The therapeutic effect of the Dlimonene nanoemulsion, CSNPs, and CdlNPs on the plants' defense response against necrotrophic fungal pathogens was evaluated by monitoring the dynamic morpho-physiological changes via multispectral image-based phenotyping in an Arabidopsis thaliana (Col-0)−B. cinerea model system. Functional analysis of the differentially expressed genes revealed that at the concentration of significant disease resistance (0.5%), CSNPs downregulated the biological process involved in plant growth and development, but upregulated the main process controlling response to stress.