Use of 2D and co-culture cell models to assess the toxicity of zein nanoparticles loading insect repellents icaridin and geraniol

After the latest dengue and Zika outbreaks, the fight against mosquito vectors has become an emerging area of research. One tool for this combat is repellents; however, these products are composed of different toxic agents. Botanical compounds with repellent potential are an alternative; however these compounds are highly volatile. Thus, the present study aimed to synthesize zein-based polymeric nanoparticles as an efficient carrier system for the sustained release of the repellents icaridin and geraniol and evaluate the toxicity of these nanorepellents comparing two different cell models. In vitro tests were carried out due to current Brazilian legislation prohibiting animal testing for cosmetics (current classification of repellents). The cytotoxicity and genotoxicity of the nanoparticles were evaluated in 2D and co-culture cell models (A549/lung epithelium, HaCaT/keratinocytes, HT-29/intestinal epithelium, and THP-1/peripheral blood monocytes). Cell viability by mitochondrial activity, cell membrane integrity, damage to genetic material, and expression of genes involved in the allergic/inflammatory system were evaluated. The results of cytotoxicity evaluation showed cell viability above 70% in both cell models. No differences were observed in genotoxicity assessment between cells exposed to nanorepellents and controls. In contrast, gene expression analysis showed increased cytokine expression for the emulsion compounds in 2D cell cultures compared to co-cultures. These findings open perspectives that zein-based nanorepellents have potential applications due to the reduced toxicity observed when the compounds are encapsulated and emerge as an alternative for arbovirus control. In addition, the study demonstrated that depending on the analysis, different results might be observed when comparing 2D and co-culture cell models to evaluate the toxicity of new nanosystems.