Bio-inspired hexagonal MoO nano-pencil rods for agrarian-pest control

Abstract

Background

The overuse and misuse of agrochemical pesticides to control pests and prevent crop losses pose serious environmental threats. To address this issue, and safeguard our environment for future generations, we aimed to develop eco-friendly and sustainable nano-biopesticides for controlling agricultural pests, such as the Bactrocera cucurbitae insect and certain microbes.

Method

Molybdenum salt, when subjected to ultra-sonification with aqueous floral extracts of Bauhinia monandra (BM) or Clitoria ternatea (CT) species, resulted in the formation of bio-inspired hexa-MoO nano-pencil-rods. The ‘h-MoO’ nano-formulation was tested for its toxicity against botanical-pest pathogens, zoological-pests, human cells, and the Wistar-rat model, using both in vitro and in vivo models.

Significant Findings

The bio-nano-template MoO_CT(33.91)/MoO_BM(44.48) nm was characterized spectroscopically using ultraviolet-visible spectroscopy (UV-Vis), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), and energy-dispersive X-ray spectroscopy (EDS). The ‘h-MoO’ formulation exhibited 100.00% efficacy against Bactrocera cucurbitae, with very low lethal concentrations, LC₅₀ and LC₉₀ values of 6.92 and 51.03 μg/mL, respectively, for 1st to 3rd instar larvae. FE-SEM images of the dead larvae revealed the presence of h-nanorods on the exterior and internal cell membrane damage. The antimicrobial capacity of ‘h-MoO’ was high, with a low EC₅₀ [1.92 to 20.21 (µg/mL)] and significant inhibition rates (14.28 to 99.28%) against agricultural pest pathogens. In vitro tests demonstrated notable oxidative stress and reactive oxygen species generation in the anti-microbials, as well as low toxicity to human cells (Hep G2, HeLa and HaCaT). In vivo trials on the Wistar-rat model showed low toxicity for the administered doses.