In vitro acaricidal activity of nano-SiO2 against Hyalomma spp. ticks and its toxicity

The Hyalomma species of ticks is hematophagous ectoparasites and responsible for transmission of protozoan, bacterial, rickettsial and viral infection in vertebrate animals and humans. Recently, nanobiotechnology is considered as a novel approach for the control of ticks. The aim of this study is to evaluate acaricidal activity of nanocristobalite (nano-SiO2) against the Hyalomma spp. in vitro and to determine its toxicity by MTT assay. The acaricidal activities of the SiO2-NPs were evaluated at concentrations of 50, 125 and 250 mg/ml and controls (distilled water and Cypermethrin) at exposure times of 10, 30 and 60 min, were performed each with two replications and two spraying and contact methods. Then the toxicity of each concentration was evaluated by MTT assay. Mortality percentages and LC50 values were calculated. Data were analysed by Graph Pad Prism 5 software. The results of this study revealed all concentrations of SiO2-NPs had acaricidal activity and concentration of 250 mg/ml of SiO2-NPs had the highest acaricidal effect (90%) at 60 min exposure time. The results showed that the spray method was more effective than the contact method and the results of MTT toxicity test showed that nano-SiO2 have very little toxicity in all concentrations. The median lethal concentration (LC50) values were obtained at 125 mg/ml in 60 min. The results indicated that SiO2-NPs contained potent acaricidal activity and might provide new acaricidal compounds for the effective control of Hyalomma spp. However, further investigations are needed to determine the efficacy of SiO2-NPs in vivo.