Biosynthesis of Moringa oleifera Silver Nanoparticles and Bio-efficacy against Anopheles gambiae

• C. M. D Ohia

• R. E. E. Ana Godson

• I. A. Oladosu

• A. O. Odeseye

• K. O Popoola

Mosquito control is pivotal in managing malaria and other mosquito-borne diseases worldwide. However, reliance on synthetic larvicides is increasingly constrained by environmental toxicity and insecticide resistance, necessitating the exploration of eco-friendly alternatives. This study investigates the biosynthesis of Moringa oleifera-synthesised silver nanoparticles (MOS-AgNPs) using aqueous extracts of Moringa oleifera seeds (AEMOS), characterizes their physicochemical properties, and evaluates their bio-efficacy against immature stages of Anopheles gambiae.  MOS-AgNPs were synthesized by reacting freshly prepared AEMOS with 1mM silver nitrate (AgNO₃) solution. The formation of MOS-AgNPs was initially confirmed through a color change from light golden yellow to colloidal yellowish-brown. Characterization techniques, including ultraviolet-visible (UV-Vis) spectroscopy, Fourier transform infrared (FTIR) spectroscopy, and transmission electron microscopy (TEM) were used to establish physicochemical properties of the nanoparticles formed. For the bioassays, the larvicidal activity of MOS-AgNPs and AEMOS was assessed against immature A. gambiae at various concentrations of solutions of AEMOS (50, 100, 150, 200, 250ppm) and MOS-AgNPs (5, 10, 15, 20, 25ppm) in five replicates with distilled water as a control. The setup was observed for moribund and dead larvae and pupae until 96 hours post-exposure. Data were subjected to descriptive and inferential analyses. Data from the characterization of the nanoproduct revealed that the nanoparticles exhibited a surface plasmon resonance (SPR) band at 384.30 nm, spherical morphology, and an average size of 25 ± 2 nm. FTIR analysis confirmed functionalization with biomolecules from M. oleifera seeds. Dose-dependent toxic effects were observed from the bioassays, achieving ≥60% mortality within 24 hours of exposure. MOS-AgNPs exhibited superior efficacy, with LC₅₀ values ranging from 9.27 ppm in larval stage 1 (L1) to 12.42 ppm in the pupal stages as compared to AEMOS, which ranged from 203.99 ppm (L1) to 106.43 ppm (pupae).  Overall, the stages of development of the mosquitoes had significant correlation (p˂0.05) with the % mortality recorded within the exposure time across treatment concentrations used. The findings demonstrate that M. oleifera -synthesised silver nanoparticles are highly effective larvicidal agents against A. gambiae, underscoring their potential for integration into green mosquito vector control strategies. This study highlights the promise of plant-based nanotechnology as a sustainable and potent alternative to conventional larvicides in combating mosquito-borne diseases

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