Toxicity evaluation and biological activity of zein nanoparticles containing the biocide azadirachtin

Author(s)

Mônica Pascoli

• Document type: Doctoral Thesis
• Press: Sorocaba. 2019-09-17.
• Institution: Universidade Estadual Paulista (Unesp). Instituto de Ciência e Tecnologia. Sorocaba
• Defense date: 2019-09-02
• Advisor: Leonardo Fernandes Fraceto; Renata de Lima

Abstract

For pest control, large amounts of agrochemicals are continuously used which often have adverse effects on the environment and human health. This fact has motivated the search for less impacting alternatives. In this scenario, several mechanisms are being studied in order to minimize these damages, such as the development of carrier systems using biodegradable polymers and proteins. In addition, the use of botanical insecticides has also shown potential for pest control, due to the possible lower impacts caused by these products of natural origin. Therefore, the present work describes the preparation and characterization of a nanobiopesticide based on neem oil-loaded zein nanoparticles, together with evaluation of their toxicity towards nontarget organisms (using Allium cepa, soil nitrogen cycle microbiota, and Caenorhabditis elegans) and of their phytotoxicity (Phaseolus vulgaris). In addition the biological activity of this new system on agricultural pests (Acanthoscelides obtectus, Bemisia tabaci and Tetranychus urticae) were also carried out. The spherical nanoparticles showed an average diameter of 278 ± 61.5 nm, a high encapsulation efficiency (>80%) and a good stability during the experiments. In the toxicity assays with A. cepa, the neem oil-loaded zein nanoparticles mitigated the increase in the DNA relative damage index caused by the neem oil. Molecular genetic analysis of the soil nitrogen cycle microbiota revealed that neem oil-loaded zein nanoparticles did not change the number of genes which encode nitrogen-fixing enzymes and denitrifying enzymes. In C. elegans, the neem oil-loaded zein nanoparticles had no toxic effect, while neem oil interfered with pharyngeal pumping and GST-4 protein expression. Pre- and post-emergence treatments using this new system did not cause any phytotoxic effects towards P. vulgaris. The neem oil nanobiopesticide exhibited insecticidal effects on B. tabaci and T. urticae, while the effect against A. obtectus was significantly increased, compared to plain neem oil. Using labeled nanoformulations, it was possible to identify the exposure between nanobiopesticide and A. obtectus mainly by their ventral region with prominence to the legs and mouthparts. These neem oil-loaded zein nanoparticles showed promising results as a nanobiopesticide developed with the "safer by design" strategy which gives it great potential for use in pest control in sustainable agriculture, causing less impacts on the environment and human health. (AU)

• FAPESP's process: 15/17120-4 - Toxicity evaluation and biological activity of zein nanoparticles containing the biocide azadirachtin
• Grantee: Mônica Pascoli
• Support Opportunities: Scholarships in Brazil - Doctorate