Cellulose Nanocrystal-Based Emulsion of Thyme Essential Oil: Preparation and Characterisation as Sustainable Crop Protection Tool

Abstract

Essential oil-based pesticides, which contain antimicrobial and antioxidant molecules, have potential for use in sustainable agriculture. However, these compounds have limitations such as volatility, poor water solubility, and phytotoxicity. Nanoencapsulation, through processes like micro- and nanoemulsions, can enhance the stability and bioactivity of essential oils. In this study, thyme essential oil from supercritical carbon dioxide extraction was selected as a sustainable antimicrobial tool and nanoencapsulated in an oil-in-water emulsion system. The investigated protocol provided high-speed homogenisation in the presence of cellulose nanocrystals as stabilisers and calcium chloride as an ionic crosslinking agent. Thyme essential oil was characterised via GC-MS and UV-vis analysis, indicating rich content in phenols. The cellulose nanocrystal/essential oil ratio and calcium chloride concentration were varied to tune the nanoemulsions’ physical–chemical stability, which was investigated via UV-vis, direct observation, dynamic light scattering, and Turbiscan analysis. Transmission electron microscopy confirmed the nanosized droplet formation. The nanoemulsion resulting from the addition of crosslinked nanocrystals was very stable over time at room temperature. It was evaluated for the first time on Pseudomonas savastanoi pv. savastanoi, the causal agent of olive knot disease. In vitro tests showed a synergistic effect of the formulation components, and in vivo tests on olive seedlings demonstrated reduced bacterial colonies without any phytotoxic effect. These findings suggest that crosslinked cellulose nanocrystal emulsions can enhance the stability and bioactivity of thyme essential oil, providing a new tool for crop protection.

Natural Deep Eutectic Solvents as a Novel Bio-Based Matrix for Ready-to-Use Natural Antioxidants-Enriched Ingredients: Extraction and Formulation Optimization

“…Results are presented in Table 6 in terms of TSI and of estimated droplet size. The control cream, free of Calendula extract, exhibited a TSI value of 0.83 ± 0.21 at D1 and a droplet size of 9.3 ± 0.2 nm, indicating an initially stable formulation [53]. For the creams containing 1 and 10%wt BGCE, the TSI values observed at day one were also very close to 1 (1.23 ± 0.23 and 0.97 ± 0.35, respectively), and the droplet size was also inferior to 10 µm, showing a low susceptibility to creaming or oil release.…”

Advances in the Design of Functional Cellulose Based Nanopesticide Delivery Systems

“…Pickering emulsions have gained increasing attention, which are stabilized using eco-friendly solid particles instead of conventional organic surfactants . Nanocellulose is an ideal stabilizer for Pickering emulsions in the encapsulation of AIs, the resulting emulsions were stable over a long time at room temperature. , Yang et al designed a CNCs-stabled salts/water/vegetable oil emulsion, this oil-in-water (O/W) Pickering emulsion demonstrates high encapsulation efficiency (96.76%) as well as sustained release (82 h) of imidacloprid (Figure A). In another study, Shin et al utilized sulfated cellulose nanocrystal (S-CNC) to increase the surface tension of Phytochemicals, indicating high physical stability and potent larvicidal activity.…”