Mosquitocidal and antibacterial activity of green-synthesized silver nanoparticles from Aloe vera extracts: towards an effective tool against the malaria vector Anopheles stephensi?

Abstract

Mosquitoes represent an important threat for lives of millions of people worldwide, acting as vectors for devastating pathogens, such as malaria, yellow fever, dengue, and West Nile. In addition, pathogens and parasites polluting water also constitute a severe plague for populations of developing countries. Here, we investigated the mosquitocidal and antibacterial properties of Aloe vera leaf extract and silver nanoparticles synthesized using A. vera extract. Mosquitocidal properties were assessed in laboratory against larvae (I-IV instar) and pupae of the malaria vector Anopheles stephensi. Green-synthesized silver nanoparticles were tested against An. stephensi also in field conditions. Antibacterial properties of nanoparticles were evaluated against Bacillus subtilis, Klebsiella pneumoniae, and Salmonella typhi using the agar disk diffusion and minimum inhibitory concentration protocol. The synthesized silver nanoparticles were characterized by UV-vis spectrum, Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and X-ray diffraction (XRD). In laboratory conditions, the A. vera extract was toxic against An. stephensi larvae and pupae, even at low dosages. LC50 were 48.79 ppm (I instar), 59.09 ppm (II instar), 70.88 ppm (III instar), 83.58 ppm (IV instar), and 152.55 ppm (pupae). Green-synthesized silver nanoparticles were highly toxic against An. stephensi. LC50 were 3.825 ppm (I instar), 4.119 ppm (II instar), 4.982 ppm (III instar), 5.711 ppm (IV instar), and 6.113 ppm (pupae). In field conditions, the application of A. vera-synthesized silver nanoparticles (10 × LC50) leads to An. stephensi larval reduction of 74.5, 86.6, and 97.7%, after 24, 48, and 72 h, respectively. Nanoparticles also showed antibacterial properties, and the maximum concentration tested (150 mg/L) evoked an inhibition zone wider than 80 mm in all tested bacterium species. This study adds knowledge about the use of green synthesis of nanoparticles in medical entomology and parasitology, allowing us to propose A. vera-synthesized silver nanoparticles as effective candidates to develop newer and safer mosquitocidal control tools.

Eco-friendly drugs from the marine environment: spongeweed-synthesized silver nanoparticles are highly effective on Plasmodium falciparum and its vector Anopheles stephensi, with little non-target effects on predatory copepods

“…The appearance of the yellowish-brown color was an indication of the synthesis of colloidal AgNP in the medium. The dark color may be due to the excitation of surface plasmon vibrations, typical of the AgNP (Ahmad et al 2003;Dinesh et al 2015). In agreement with our results, a peak with maximum absorption at 410 nm characterized the synthesis of Aloe vera-fabricated AgNP , while peaks with maximum absorption at 450 and 420 nm were observed for Moringa oleifera-fabricated AgNP (Sujitha et al 2015) and Phyllanthus niruri-synthesized AgNP , respectively.…”

“…Similarly, Devina Merin et al (2010) have reported the anti-bacterial activity of AgNP synthesized from marine microalgae. Dinesh et al (2015) focused on the antimicrobial activity of A. vera-synthesized AgNP tested at 300 ppm against three bacteria species. A. vera-fabricated AgNP led to zones of inhibition higher than 19 mm in all targeted bacteria.…”

Nanofabrication of Graphene Quantum Dots with High Toxicity Against Malaria Mosquitoes, Plasmodium falciparum and MCF-7 Cancer Cells: Impact on Predation of Non-target Tadpoles, Odonate Nymphs and Mosquito Fishes

“…For both species, eggs were transferred to laboratory conditions [27 ± 2°C, 75-85 % R.H., 14:10 (L:D) photoperiod] and placed in 18 9 13 9 4 cm plastic containers containing 500 mL of tap water, waiting for larval hatching [44,45]. Larvae were reared in the containers and fed daily with a mixture of crushed dog biscuits (Pedigree, USA) and hydrolyzed yeast (Sigma-Aldrich, Germany) at a 3:1 ratio (w:w).…”

“…Larval food (0.5 mg) was provided for each tested concentration [44]. Control mosquitoes were exposed for 24 h to the corresponding concentration of the solvent.…”

“…In latest years, a growing number of nanocomposites have been studied for their toxic activity against young instars of several mosquito vectors (e.g. [11,25,36,37,44,45,[77][78][79][80]). A good example is the larvicidal activity of Sargassum muticum-synthesized Ag nanoparticles against larval instars and pupae of A. aegypti, A. stephensi, and C. quinquefasciatus [81].…”