Synthesis and Optimisation of Psidium guajava Leaf-Based Titanium (IV) Oxide Nanoparticles and their Larvicidal effect against Anopheles gambiae s.l.

Abstract

Mosquitoes have been known to spread diseases of public health concerns to human of which malaria fever is the most prevalent globally. In order to develop environmentally friendly vector control method, plant-based nanoparticles have attracted considerable attention in recent times. Research has shown that environmental factors such as light duration during development interfere with insects’ development and responses. In this study, different light regimen was explored in testing the effect of different light regimen on larvicidal potential of synthesized silver nanoparticles (AgNPs) solution of Vitellaria paradoxa (Shea butter) leaf. This was tested against 3rd to 4th larval stages of Anopheles gambiae senso lato. Zeta potential shows the average size of synthesized silver nanoparticle to be 62.36 nm with 1mM of AgNO3 at 5 minutes. UV spectrometry shows its absorbance at the wavelength of 411.5 peaking at 1.702 absorbance. Thermo-gravimetric and Differential Thermal Analysis revealed an initial weight loss at 110oC and further degradation between 440oC and 700oC which shows its stability. Larvicidal bioassay showed that the mean mortality was not significant at p<0.05 for larvae reared under 6 hours and 18 hours of light. The mean mortality was significant for those reared under 12 hours of light with LC50 and LC90 of 24.99 and 49.88 mg/l respectively, R2 value being 0.99. Therefore, through this study, it could be deduced that light duration has a significant effect on the responses of Anopheles gambiae s. l. and there is the possibility of enhancing larvicidal efficacy of plant mediated silver nanoparticles by alteration of light duration on the developing larvae.