Phytosynthesized Gold Nanoparticles-Bacillus thuringiensis (Bt–GNP) Formulation: A Novel Photo Stable Preparation Against Mosquito Larvae

It is well-known that the sunlight irradiation damages the spores and toxin produced by Bacillus thuringiensis (Bt), which leads to loss of their insecticidal activity. This photodegradation problem is addressed in the present investigation by use of green phytosynthesized gold nanoparticles (GNP) as a photoprotectant. The efficiency of Bt with GNP before and after exposing to sunlight was evaluated against the larvae of Aedes aegypti and Anopheles subpictus. The bioassay results focused that after sunlight irradiation the Bt significantly lose their activity for Ae. aegypti (23.13%) and An. subpictus (27.08%). Although the individual GNP showed very less activity against tested larvae, it was observed that in combination with Bt it significantly enhances activity and consequently reduced the LC₅₀ of Bt–GNP. Similarly, even after irradiation of Bt–GNP formulation, the enhanced activity was found against Ae. aegypti (23.10%) and An. subpictus (27.24%). Henceforth in the case of Bt–GNP formulation, the GNP it was not only protecting the Bt from sunlight but enhances its larvicidal potential. The interactions between the GNP and Bt toxin which might be the main reason to protect the Bt from sunlight and can help to locate the Bt toxin at the target site.