Nanostructured lipid carriers of essential oils as potential tools for the sustainable control of insect pests

Plant essential oils (EOs) represent a promising alternative and sustainable tool to reduce the negative environmental impact of conventional management systems, e.g., synthetic insecticides. Their practical implementation is hindered by various drawbacks, such as phytotoxicity, stability and degradation patterns.
Innovative and advanced nanotechnologies, such as Nanostructured Lipid Carriers (NLCs), could help overcoming such problems. NLCs, composed by 10% w/v of lipid and 10% w/v of oil (Lavender, Rosemary,Peppermint) were prepared through PIT method. The obtained formulations showed the presence of small (200nm) and homogeneous particles (Polydispersity Index (PDI) < 0.3). All NLCs were purified obtaining a 20% w/v EO concentration using ultracentrifugation, without any significant variation of mean size and homogeneity. The efficacy of these formulations was tested for three key insect pests with different feeding strategies: a sap-sucking (Aphis gossypii), a chewer (Spodoptera littoralis) and a leafminer (Tuta absoluta). NLCs loaded with EOs were diluted with distilled water at 30:70 v/v and were tested by ingestion and topical contact exposure routes. Longterm stability results obtained by Turbiscan® technology showed the occurrence of not significant (ΔBS < 20%) sedimentation phenomenon after 30 days of storage at 25 C. Among the three EO-NLCs, Rosemary demonstrated to be the most long-term stable, as confirmed by the destabilization kinetic. The results of the bioassays showed that all the tested EO-NLCs, as well as the nanocarrier alone, caused high mortality on A. gossypii and significantly reduced its progeny by topical contact exposure. NLCs of Lavender and Rosemary EOs decreased the feeding activity but not the survival of S. littoralis. Conversely, the three EO-NLCs did not decrease the survival and the feeding activity of T. absoluta. Our findings suggest that NLCs can successfully deliver EOs by keeping unaltered their properties, therefore this nanotechnology could contribute to the sustainable control of arthropod pests.

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