Magnetic nanoparticles are highly toxic to chloroquine-resistant Plasmodium falciparum, dengue virus (DEN-2), and their mosquito vectors.

A main challenge in parasitology is the development of reliable tools to prevent or treat mosquito-borne diseases. We investigated the toxicity of magnetic nanoparticles (MNP) produced by Magnetospirillum gryphiswaldense (strain MSR-1) on chloroquine-resistant (CQ-r) and sensitive (CQ-s) Plasmodium falciparum, dengue virus (DEN-2), and two of their main vectors, Anopheles stephensi and Aedes aegypti, respectively. MNP were studied by Fourier-transform infrared spectroscopy and transmission electron microscopy. They were toxic to larvae and pupae of An. stephensi, LC50 ranged from 2.563 ppm (1st instar larva) to 6.430 ppm (pupa), and Ae. aegypti, LC50 ranged from 3.231 ppm (1st instar larva) to 7.545 ppm (pupa). MNP IC50 on P. falciparum were 83.32 µg ml-1 (CQ-s) and 87.47 µg ml-1 (CQ-r). However, the in vivo efficacy of MNP on Plasmodium berghei was low if compared to CQ-based treatments. Moderate cytotoxicity was detected on Vero cells post-treatment with MNP doses lower than 4 µg ml-1. MNP evaluated at 2-8 µg ml-1 inhibited DEN-2 replication inhibiting the expression of the envelope (E) protein. In conclusion, our findings represent the first report about the use of MNP in medical and veterinary entomology, proposing them as suitable materials to develop reliable tools to combat mosquito-borne diseases.

Hydrothermal synthesis of titanium dioxide nanoparticles: mosquitocidal potential and anticancer activity on human breast cancer cells (MCF-7).

Mosquito vectors (Diptera: Culicidae) are responsible for transmission of serious diseases worldwide. Mosquito control is being enhanced in many areas, but there are significant challenges, including increasing resistance to insecticides and lack of alternative, cost-effective, and eco-friendly products. To deal with these crucial issues, recent emphasis has been placed on plant materials with mosquitocidal properties. Furthermore, cancers figure among the leading causes of morbidity and mortality worldwide, with approximately 14 million new cases and 8.2 million cancer-related deaths in 2012. It is expected that annual cancer cases will rise from 14 million in 2012 to 22 million within the next two decades. Nanotechnology is a promising field of research and is expected to give major innovation impulses in a variety of industrial sectors. In this study, we synthesized titanium dioxide (TiO2) nanoparticles using the hydrothermal method. Nanoparticles were subjected to different analysis including UV-Vis spectrophotometry, Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), zeta potential, and energy-dispersive spectrometric (EDX). The synthesized TiO2 nanoparticles exhibited dose-dependent cytotoxicity against human breast cancer cells (MCF-7) and normal breast epithelial cells (HBL-100). After 24-h incubation, the inhibitory concentrations (IC50) were found to be 60 and 80 µg/mL on MCF-7 and normal HBL-100 cells, respectively. Induction of apoptosis was evidenced by Acridine Orange (AO)/ethidium bromide (EtBr) and 4',6-diamidino-2-phenylindole dihydrochloride (DAPI) staining. In larvicidal and pupicidal experiments conducted against the primary dengue mosquito Aedes aegypti, LC50 values of nanoparticles were 4.02 ppm (larva I), 4.962 ppm (larva II), 5.671 ppm (larva III), 6.485 ppm (larva IV), and 7.527 ppm (pupa). Overall, our results suggested that TiO2 nanoparticles may be considered as a safe tool to build newer and safer mosquitocides and chemotherapeutic agents with little systemic toxicity.

Biosynthesis, characterization, and acute toxicity of Berberis tinctoria-fabricated silver nanoparticles against the Asian tiger mosquito, Aedes albopictus, and the mosquito predators Toxorhynchites splendens and Mesocyclops thermocyclopoides.

Aedes albopictus is an important arbovirus vector, including dengue. Currently, there is no specific treatment for dengue. Its prevention solely depends on effective vector control measures. In this study, silver nanoparticles (AgNPs) were biosynthesized using a cheap leaf extract of Berberis tinctoria as reducing and stabilizing agent and tested against Ae. albopictus and two mosquito natural enemies. AgNPs were characterized by using UV­vis spectrophotometry, X-ray diffraction, and scanning electron microscopy. In laboratory conditions, the toxicity of AgNPs was evaluated on larvae and pupae of Ae. albopictus. Suitability Index/Predator Safety Factor was assessed on Toxorhynchites splendens and Mesocyclops thermocyclopoides. The leaf extract of B. tinctoria was toxic against larval instars (I­IV) and pupae of Ae. albopictus; LC50 was 182.72 ppm (I instar), 230.99 ppm (II), 269.65 ppm (III), 321.75 ppm (IV), and 359.71 ppm (pupa). B. tinctoria-synthesized AgNPs were highly effective, with LC50 of 4.97 ppm (I instar), 5.97 ppm (II), 7.60 ppm (III), 9.65 ppm (IV), and 14.87 ppm (pupa). Both the leaf extract and AgNPs showed reduced toxicity against the mosquito natural enemies M. thermocyclopoides and T. splendens. Overall, this study firstly shed light on effectiveness of B. tinctoria-synthesized AgNPs as an eco-friendly nanopesticide, highlighting the concrete possibility to employ this newer and safer tool in arbovirus vector control programs.

Fern-synthesized nanoparticles in the fight against malaria: LC/MS analysis of Pteridium aquilinum leaf extract and biosynthesis of silver nanoparticles with high mosquitocidal and antiplasmodial activity.

Malaria remains a major public health problem due to the emergence and spread of Plasmodium falciparum strains resistant to chloroquine. There is an urgent need to investigate new and effective sources of antimalarial drugs. This research proposed a novel method of fern-mediated synthesis of silver nanoparticles (AgNP) using a cheap plant extract of Pteridium aquilinum, acting as a reducing and capping agent. AgNP were characterized by UV-vis spectrophotometry, Fourier transform infrared (FTIR) spectroscopy, energy-dispersive X-ray spectroscopy (EDX), and X-ray diffraction (XRD). Phytochemical analysis of P. aquilinum leaf extract revealed the presence of phenols, alkaloids, tannins, flavonoids, proteins, carbohydrates, saponins, glycosides, steroids, and triterpenoids. LC/MS analysis identified at least 19 compounds, namely pterosin, hydroquinone, hydroxy-acetophenone, hydroxy-cinnamic acid, 5, 7-dihydroxy-4-methyl coumarin, trans-cinnamic acid, apiole, quercetin 3-glucoside, hydroxy-L-proline, hypaphorine, khellol glucoside, umbelliferose, violaxanthin, ergotamine tartrate, palmatine chloride, deacylgymnemic acid, methyl laurate, and palmitoyl acetate. In DPPH scavenging assays, the IC50 value of the P. aquilinum leaf extract was 10.04 µg/ml, while IC50 of BHT and rutin were 7.93 and 6.35 µg/ml. In mosquitocidal assays, LC50 of P. aquilinum leaf extract against Anopheles stephensi larvae and pupae were 220.44 ppm (larva I), 254.12 ppm (II), 302.32 ppm (III), 395.12 ppm (IV), and 502.20 ppm (pupa). LC50 of P. aquilinum-synthesized AgNP were 7.48 ppm (I), 10.68 ppm (II), 13.77 ppm (III), 18.45 ppm (IV), and 31.51 ppm (pupa). In the field, the application of P. aquilinum extract and AgNP (10 × LC50) led to 100 % larval reduction after 72 h. Both the P. aquilinum extract and AgNP reduced longevity and fecundity of An. stephensi adults. Smoke toxicity experiments conducted against An. stephensi adults showed that P. aquilinum leaf-, stem-, and root-based coils evoked mortality rates comparable to the permethrin-based positive control (57, 50, 41, and 49 %, respectively). Furthermore, the antiplasmodial activity of P. aquilinum leaf extract and green-synthesized AgNP was evaluated against CQ-resistant (CQ-r) and CQ-sensitive (CQ-s) strains of P. falciparum. IC50 of P. aquilinum were 62.04 µg/ml (CQ-s) and 71.16 µg/ml (CQ-r); P. aquilinum-synthesized AgNP achieved IC50 of 78.12 µg/ml (CQ-s) and 88.34 µg/ml (CQ-r). Overall, our results highlighted that fern-synthesized AgNP could be candidated as a new tool against chloroquine-resistant P. falciparum and different developmental instars of its primary vector An. stephensi. Further research on nanosynthesis routed by the LC/MS-identified constituents is ongoing.

Characterization and mosquitocidal potential of neem cake-synthesized silver nanoparticles: genotoxicity and impact on predation efficiency of mosquito natural enemies.

Mosquitoes (Diptera: Culicidae) serve as important vectors for a wide number of parasites and pathogens of huge medical and veterinary importance. Aedes aegypti is a primary dengue vector in tropical and subtropical urban areas. There is an urgent need to develop eco-friendly mosquitocides. In this study, silver nanoparticles (AgNP) were biosynthesized using neem cake, a by-product of the neem oil extraction from the seed kernels of Azadirachta indica. AgNP were characterized using a variety of biophysical methods, including UV-vis spectrophotometry, FTIR, SEM, EDX, and XRD analyses. Furthermore, the neem cake extract and the biosynthesized AgNP were tested for acute toxicity against larvae and pupae of the dengue vector Ae. aegypti. LC50 values achieved by the neem cake extract ranged from 106.53 (larva I) to 235.36 ppm (pupa), while AgNP LC50 ranged from 3.969 (larva I) to 8.308 ppm (pupa). In standard laboratory conditions, the predation efficiency of a Carassius auratus per day was 7.9 (larva II) and 5.5 individuals (larva III). Post-treatment with sub-lethal doses of AgNP, the predation efficiency was boosted to 9.2 (larva II) and 8.1 individuals (larva III). The genotoxic effect of AgNP was studied on C. auratus using the comet assay and micronucleus frequency test. DNA damage was evaluated on peripheral erythrocytes sampled at different time intervals from the treatment; experiments showed no significant damages at doses below 12 ppm. Overall, this research pointed out that neem cake-fabricated AgNP are easy to produce, stable over time, and can be employed at low dosages to reduce populations of dengue vectors, with moderate detrimental effects on non-target mosquito natural enemies.

Genetic deviation in geographically close populations of the dengue vector Aedes aegypti (Diptera: Culicidae): influence of environmental barriers in South India.

Mosquitoes are vectors of devastating pathogens and parasites, causing millions of deaths every year. Dengue is a mosquito-borne viral infection found in tropical and subtropical regions around the world. Recently, dengue transmission has strongly increased in urban and semiurban areas, becoming a major international public health concern. Aedes aegypti (Diptera: Culicidae) is a primary vector of dengue. Shedding light on genetic deviation in A. aegypti populations is of crucial importance to fully understand their molecular ecology and evolution. In this research, haplotype and genetic analyses were conducted using individuals of A. aegypti from 31 localities in the north, southeast, northeast and central regions of Tamil Nadu (South India). The mitochondrial DNA region of cytochrome c oxidase 1 (CO1) gene was used as marker for the analyses. Thirty-one haplotypes sequences were submitted to GenBank and authenticated. The complete haplotype set included 64 haplotypes from various geographical regions clustered into three groups (lineages) separated by three fixed mutational steps, suggesting that the South Indian Ae. aegypti populations were pooled and are linked with West Africa, Columbian and Southeast Asian lineages. The genetic and haplotype diversity was low, indicating reduced gene flow among close populations of the vector, due to geographical barriers such as water bodies. Lastly, the negative values for neutrality tests indicated a bottle-neck effect and supported for low frequency of polymorphism among the haplotypes. Overall, our results add basic knowledge to molecular ecology of the dengue vector A. aegypti, providing the first evidence for multiple introductions of Ae. aegypti populations from Columbia and West Africa in South India.

Carbon and silver nanoparticles in the fight against the filariasis vector Culex quinquefasciatus: genotoxicity and impact on behavioral traits of non-target aquatic organisms.

Mosquito-borne diseases represent a deadly threat for millions of people worldwide. The Culex genus, with special reference to Culex quinquefasciatus, comprises the most common vectors of filariasis across urban and semi-urban areas of Asia. In recent years, important efforts have been conducted to propose green-synthesized nanoparticles as a valuable alternative to synthetic insecticides. However, the mosquitocidal potential of carbon nanoparticles has been scarcely investigated. In this study, the larvicidal and pupicidal activity of carbon nanoparticle (CNP) and silver nanoparticle (AgNP) was tested against Cx. quinquefasciatus. UV-Vis spectrophotometry, Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD) analysis, scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy-dispersive X-ray (EDX) spectroscopy, and Raman analysis confirmed the rapid and cheap synthesis of carbon and silver nanoparticles. In laboratory assays, LC50 (lethal concentration that kills 50 % of the exposed organisms) values ranged from 8.752 ppm (first-instar larvae) to 18.676 ppm (pupae) for silver nanoparticles and from 6.373 ppm (first-instar larvae) to 14.849 ppm (pupae) for carbon nanoparticles. The predation efficiency of the water bug Lethocerus indicus after a single treatment with low doses of silver and carbon nanoparticles was not reduced. Moderate evidence of genotoxic effects induced by exposure to carbon nanoparticles was found on non-target goldfish, Carassius auratus. Lastly, the plant extract used for silver nanosynthesis was tested for 2,2-diphenyl-1-picrylhydrazyl (DPPH) and 2,2'-azino-bis-3-ethylbenzothiazoline-6-sulfonic acid (ABTS) radical scavenging activity. Overall, our results pointed out that AgNP and CNP can be a candidate for effective tools to reduce larval and pupal populations of filariasis vectors, with reduced genotoxicity and impact on behavioral traits of other aquatic organisms sharing the same ecological niche of Cx. quinquefasciatus.

Fabrication of nano-mosquitocides using chitosan from crab shells: Impact on non-target organisms in the aquatic environment.

Mosquitoes are arthropods of huge medical and veterinary relevance, since they vector pathogens and parasites of public health importance, including malaria, dengue and Zika virus. Currently, nanotechnology is considered a potential eco-friendly approach in mosquito control research. We proposed a novel method of biofabrication of silver nanoparticles (AgNP) using chitosan (Ch) from crab shells. Ch-AgNP nanocomposite was characterized by UV-vis spectroscopy, FTIR, SEM, EDX and XRD. Ch-AgNP were tested against larvae and pupae of the malaria vector Anopheles stephensi obtaining LC50 ranging from 3.18 ppm (I) to 6.54 ppm (pupae). The antibacterial properties of Ch-AgNP were proved against Bacillus subtilis, Klebsiella pneumoniae and Salmonella typhi, while no growth inhibition was reported in assays conducted on Proteus vulgaris. Concerning non-target effects, in standard laboratory considtions the predation efficiency of Danio rerio zebrafishes was 68.8% and 61.6% against I and II instar larvae of A. stephensi, respectively. In a Ch-AgNP-contaminated environment, fish predation was boosted to 89.5% and 77.3%, respectively. Quantitative analysis of antioxidant enzymes SOD, CAT and LPO from hepatopancreas of fresh water crabs Paratelphusa hydrodromous exposed for 16 days to a Ch-AgNP-contaminated aquatic environment were conducted. Notably, deleterious effects of Ch-AgNP contaminating aquatic enviroment on the non-target crab P. hydrodromous were observed, particularly when doses higher than 8-10ppm are tested. Overall, this research highlights the potential of Ch-AGNP for the development of newer control tools against young instar populations of malaria mosquitoes, also highlighting some risks concerned the employ of nanoparticles in aquatic environments.

Cymbopogon citratus-synthesized gold nanoparticles boost the predation efficiency of copepod Mesocyclops aspericornis against malaria and dengue mosquitoes.

Plant-borne compounds can be employed to synthesize mosquitocidal nanoparticles that are effective at low doses. However, how they affect the activity of mosquito predators in the aquatic environment is unknown. In this study, we synthesized gold nanoparticles (AuN) using the leaf extract of Cymbopogon citratus, which acted as a reducing and capping agent. AuN were characterized by a variety of biophysical methods and sorted for size in order to confirm structural integrity. C. citratus extract and biosynthesized AuN were tested against larvae and pupae of the malaria vector Anopheles stephensi and the dengue vector Aedes aegypti. LC50 of C. citratus extract ranged from 219.32 ppm to 471.36 ppm. LC50 of AuN ranged from 18.80 ppm to 41.52 ppm. In laboratory, the predatory efficiency of the cyclopoid crustacean Mesocyclops aspericornis against A. stephensi larvae was 26.8% (larva I) and 17% (larva II), while against A. aegypti was 56% (I) and 35.1% (II). Predation against late-instar larvae was minimal. In AuN-contaminated environment,predation efficiency against A. stephensi was 45.6% (I) and 26.7% (II), while against A. aegypti was 77.3% (I) and 51.6% (II). Overall, low doses of AuN may help to boost the control of Anopheles and Aedes larval populations in copepod-based control programs.

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

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.

Tackling the growing threat of dengue: Phyllanthus niruri-mediated synthesis of silver nanoparticles and their mosquitocidal properties against the dengue vector Aedes aegypti (Diptera: Culicidae).

Mosquitoes are vectors of devastating pathogens and parasites, causing millions of deaths every year. Dengue is a mosquito-borne viral infection found in tropical and subtropical regions around the world. Recently, transmission has strongly increased in urban and semiurban areas, becoming a major international public health concern. Aedes aegypti (Diptera: Culicidae) is the primary vector of dengue. The use of synthetic insecticides to control Aedes mosquitoes lead to high operational costs and adverse nontarget effects. In this scenario, eco-friendly control tools are a priority. We proposed a novel method to synthesize silver nanoparticles using the aqueous leaf extract of Phyllanthus niruri, a cheap and nontoxic material. The UV-vis spectrum of the aqueous medium containing silver nanostructures showed a peak at 420 nm corresponding to the surface plasmon resonance band of nanoparticles. SEM analyses of the synthesized nanoparticles showed a mean size of 30-60 nm. EDX spectrum showed the chemical composition of the synthesized nanoparticles. XRD highlighted that the nanoparticles are crystalline in nature with face-centered cubic geometry. Fourier transform infrared spectroscopy (FTIR) of nanoparticles exhibited prominent peaks 3,327.63, 2,125.87, 1,637.89, 644.35, 597.41, and 554.63 cm(-1). In laboratory assays, the aqueous extract of P. niruri was toxic against larval instars (I-IV) and pupae of A. aegypti. LC50 was 158.24 ppm (I), 183.20 ppm (II), 210.53 ppm (III), 210.53 ppm (IV), and 358.08 ppm (pupae). P. niruri-synthesized nanoparticles were highly effective against A. aegypti, with LC50 of 3.90 ppm (I), 5.01 ppm (II), 6.2 ppm (III), 8.9 ppm (IV), and 13.04 ppm (pupae). In the field, the application of silver nanoparticles (10 × LC50) lead to A. aegypti larval reduction of 47.6%, 76.7% and 100%, after 24, 48, and 72 h, while the P. niruri extract lead to 39.9%, 69.2 % and 100 % of reduction, respectively. In adulticidal experiments, P. niruri extract and nanoparticles showed LC50 and LC90 of 174.14 and 6.68 ppm and 422.29 and 23.58 ppm, respectively. Overall, this study highlights that the possibility to employ P. niruri leaf extract and green-synthesized silver nanoparticles in mosquito control programs is concrete, since both are effective at lower doses if compared to synthetic products currently marketed, thus they could be an advantageous alternative to build newer and safer tools against dengue vectors.

Toxicity of seaweed-synthesized silver nanoparticles against the filariasis vector Culex quinquefasciatus and its impact on predation efficiency of the cyclopoid crustacean Mesocyclops longisetus.

Nearly 1.4 billion people in 73 countries worldwide are threatened by lymphatic filariasis, a parasitic infection that leads to a disease commonly known as elephantiasis. Filariasis is vectored by mosquitoes, with special reference to the genus Culex. The main control tool against mosquito larvae is represented by treatments with organophosphates and insect growth regulators, with negative effects on human health and the environment. Recently, green-synthesized nanoparticles have been proposed as highly effective larvicidals against mosquito vectors. In this research, we attempted a reply to the following question: do green-synthesized nanoparticles affect predation rates of copepods against mosquito larvae? We proposed a novel method of seaweed-mediated synthesis of silver nanoparticles using the frond extract of Caulerpa scalpelliformis. The toxicity of the seaweed extract and silver nanoparticles was assessed against the filarial vector Culex quinquefasciatus. Then, we evaluated the predatory efficiency of the cyclopoid crustacean Mesocyclops longisetus against larval instars of C. quinquefasciatus in a nanoparticle-contaminated water environment. Green-synthesized silver nanoparticles were characterized by UV-vis spectrum, Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and X-ray diffraction (XRD). In mosquitocidal assays, the LC50 values of the C. scalpelliformis extract against C. quinquefasciatus were 31.38 ppm (I), 46.49 ppm (II), 75.79 ppm (III), 102.26 ppm (IV), and 138.89 ppm (pupa), while LC50 of silver nanoparticles were 3.08 ppm, (I), 3.49 ppm (II), 4.64 ppm (III), 5.86 ppm (IV), and 7.33 ppm (pupa). The predatory efficiency of the copepod M. longisetus in the control treatment was 78 and 59% against I and II instar larvae of C. quinquefasciatus. In a nanoparticle-contaminated environment, predation efficiency was 84 and 63%, respectively. Predation was higher against first instar larvae over other instars. Overall, our study showed that seaweed-synthesized silver nanoparticles can be proposed in synergy with biological control agents against Culex larvae, since their use leads to little detrimental effects against aquatic predators, such as copepods.

Datura metel-synthesized silver nanoparticles magnify predation of dragonfly nymphs against the malaria vector Anopheles stephensi.

Malaria is a life-threatening disease caused by parasites transmitted to people and animals through the bites of infected mosquitoes. The employ of synthetic insecticides to control Anopheles populations leads to high operational costs, non-target effects, and induced resistance. Recently, plant-borne compounds have been proposed for efficient and rapid extracellular synthesis of mosquitocidal nanoparticles. However, their impact against predators of mosquito larvae has been poorly studied. In this study, we synthesized silver nanoparticles (AgNPs) using the Datura metel leaf extract as reducing and stabilizing agent. The biosynthesis of AgNPs was confirmed analyzing the excitation of surface plasmon resonance using ultraviolet-visible (UV-vis) spectroscopy. Scanning electron microscopy (SEM) showed the clustered and irregular shapes of AgNPs, with a mean size of 40-60 nm. The presence of silver was determined by energy-dispersive X-ray (EDX) spectroscopy. Fourier transform infrared (FTIR) spectroscopy analysis investigated the identity of secondary metabolites, which may be acting as AgNP capping agents. In laboratory, LC50 of D. metel extract against Anopheles stephensi ranged from 34.693 ppm (I instar larvae) to 81.500 ppm (pupae). LC50 of AgNP ranged from 2.969 ppm (I instar larvae) to 6.755 ppm (pupae). Under standard laboratory conditions, the predation efficiency of Anax immaculifrons nymphs after 24 h was 75.5 % (II instar larvae) and 53.5 % (III instar larvae). In AgNP-contaminated environment, predation rates were boosted to 95.5 and 78 %, respectively. Our results documented that D. metel-synthesized AgNP might be employed at rather low doses to reduce larval populations of malaria vectors, without detrimental effects on behavioral traits of young instars of the dragonfly Anax immaculifrons.

S argassum muticum-synthesized silver nanoparticles: an effective control tool against mosquito vectors and bacterial pathogens.

Mosquito-borne diseases represent a deadly threat for millions of people worldwide. Furthermore, pathogens and parasites polluting water also constitute a severe plague for populations of developing countries. In this research, silver nanoparticles (AgNP) were synthesized using the aqueous extract of the seaweed Sargassum muticum. The production of AgNP was confirmed by surface plasmon resonance band illustrated in UV-vis spectrophotometry. AgNP were characterized by FTIR, SEM, EDX, and XRD analyses. AgNP were mostly spherical in shape, crystalline in nature, with face-centered cubic geometry, and mean size was 43-79 nm. Toxicity of AgNP was assessed against Aedes aegypti, Anopheles stephensi, and Culex quinquefasciatus. In laboratory, AgNP were highly toxic against larvae and pupae of the three mosquito species. Maximum efficacy was observed against A. stephensi larvae, with LC50 ranging from 16.156 ppm (larva I) to 28.881 ppm (pupa). In the field, a single treatment with AgNP (10 × LC50) in water storage reservoirs was effective against the three mosquito vectors, allowing complete elimination of larval populations after 72 h. In ovicidal experiments, egg hatchability was reduced by 100% after treatment with 30 ppm of AgNP. Ovideterrence assays highlighted that 10 ppm of AgNP reduced oviposition rates of more than 70% in A. aegypti, A. stephensi, and C. quinquefasciatus (OAI = -0.61, -0.63, and -0.58, respectively). Antibacterial properties of AgNP were evaluated against Bacillus subtilis, Klebsiella pneumoniae, and Salmonella typhi using the agar disk diffusion and minimum inhibitory concentration protocol. AgNP tested at 50 ppm evoked growth inhibition zones larger than 5 mm in all tested bacteria. Overall, the chance to use S. muticum-synthesized AgNP for control of mosquito vectors seems promising since they are effective at low doses and may constitute an advantageous alternative to build newer and safer mosquito control tools. This is the first report about ovicidal activity of metal nanoparticles against mosquito vectors.

Mosquitocidal and antiplasmodial activity of Senna occidentalis (Cassiae) and Ocimum basilicum (Lamiaceae) from Maruthamalai hills against Anopheles stephensi and Plasmodium falciparum.

Each year, mosquito-borne diseases infect nearly 700 million people, resulting to more than 1 million deaths. In this study, we evaluated the larvicidal, pupicidal, and smoke toxicity of Senna occidentalis and Ocimum basilicum leaf extracts against the malaria vector Anopheles stephensi. Furthermore, the antiplasmodial activity of plant extracts was evaluated against chloroquine (CQ)-resistant (CQ-r) and CQ-sensitive (CQ-s) strains of Plasmodium falciparum. In larvicidal and pupicidal experiments, S. occidentalis LC50 ranged from 31.05 (I instar larvae) to 75.15 ppm (pupae), and O. basilicum LC50 ranged from 29.69 (I instar larvae) to 69 ppm (pupae). Smoke toxicity experiments conducted against adults showed that S. occidentalis and O. basilicum coils evoked mortality rates comparable to the pyrethrin-based positive control (38, 52, and 42%, respectively). In antiplasmodial assays, Senna occidentalis 50% inhibitory concentration (IC50) were 48.80 µg/ml (CQ-s) and 54.28 µg/ml (CQ-r), while O. basilicum IC50 were 68.14 µg/ml (CQ-s) and 67.27 µg/ml (CQ-r). Overall, these botanicals could be considered as potential sources of metabolites to build newer and safer malaria control tools.

Nanoparticles in the fight against mosquito-borne diseases: bioactivity of Bruguiera cylindrica-synthesized nanoparticles against dengue virus DEN-2 (in vitro) and its mosquito vector Aedes aegypti (Diptera: Culicidae).

Mosquitoes are blood-feeding insects serving as the most important vectors for spreading human pathogens and parasites. Dengue is a viral disease mainly vectored through the bite of Aedes mosquitoes. Its transmission has recently increased in urban and semi-urban areas of tropical and subtropical regions worldwide, becoming a major international public health concern. There is no specific treatment for dengue. Its prevention and control solely depend on effective vector control measures. Mangrove plants have been used in Indian traditional medicine for a wide array of purposes. In this research, we proposed a method for biosynthesis of antiviral and mosquitocidal silver nanoparticles (AgNP) using the aqueous extract of Bruguiera cylindrica leaves. AgNP were characterized using a variety of biophysical analyses, including UV-visible spectrophotometry, Fourier-transform infrared spectroscopy, scanning electron microscopy, and energy-dispersive X-ray spectroscopy. Bruguiera cilyndrica aqueous extract and green-synthesized AgNP were tested against the primary dengue vector Aedes aegypti. AgNP were the most effective. LC50 values ranged from 8.93 ppm (larva I) to 30.69 ppm (pupa). In vitro experiments showed that 30 µg/ml of AgNP significantly inhibited the production of dengue viral envelope (E) protein in vero cells and downregulated the expression of dengue viral E gene. Concerning nontarget effects, we observed that the predation efficiency of Carassius auratus against A. aegypti was not affected by exposure at sublethal doses of AgNP. Predation in the control was 71.81 % (larva II) and 50.43 % (larva III), while in an AgNP-treated environment, predation was boosted to 90.25 and 76.81 %, respectively. Overall, this study highlights the concrete potential of green-synthesized AgNP in the fight against dengue virus. Furthermore, B. cylindrica-synthesized AgNP can be employed at low doses to reduce larval and pupal population of A. aegypti, without detrimental effects of predation rates of mosquito predators, such as C. auratus.

Seaweed-synthesized silver nanoparticles: an eco-friendly tool in the fight against Plasmodium falciparum and its vector Anopheles stephensi?

Malaria, the most widespread mosquito-borne disease, affects 350-500 million people each year. Eco-friendly control tools against malaria vectors are urgently needed. This research proposed a novel method of plant-mediated synthesis of silver nanoparticles (AgNP) using a cheap seaweed extract of Ulva lactuca, acting as a reducing and capping agent. AgNP were characterized by UV-vis spectrophotometry, Fourier transform infrared (FTIR) spectroscopy, energy-dispersive X-ray spectroscopy (EDX), scanning electron microscopy (SEM), and X-ray diffraction (XRD). The U. lactuca extract and the green-synthesized AgNP were tested against larvae and pupae of the malaria vector Anopheles stephensi. In mosquitocidal assays, LC50 values of U. lactuca extract against A. stephensi larvae and pupae were 18.365 ppm (I instar), 23.948 ppm (II), 29.701 ppm (III), 37.517 ppm (IV), and 43.012 ppm (pupae). LC50 values of AgNP against A. stephensi were 2.111 ppm (I), 3.090 ppm (II), 4.629 ppm (III), 5.261 ppm (IV), and 6.860 ppm (pupae). Smoke toxicity experiments conducted against mosquito adults showed that U. lactuca coils evoked mortality rates comparable to the permethrin-based positive control (66, 51, and 41%, respectively). Furthermore, the antiplasmodial activity of U. lactuca extract and U. lactuca-synthesized AgNP was evaluated against CQ-resistant (CQ-r) and CQ-sensitive (CQ-s) strains of Plasmodium falciparum. Fifty percent inhibitory concentration (IC50) values of U. lactuca were 57.26 µg/ml (CQ-s) and 66.36 µg/ml (CQ-r); U. lactuca-synthesized AgNP IC50 values were 76.33 µg/ml (CQ-s) and 79.13 µg/ml (CQ-r). Overall, our results highlighted out that U. lactuca-synthesized AgNP may be employed to develop newer and safer agents for malaria control.

Green-synthesized silver nanoparticles as a novel control tool against dengue virus (DEN-2) and its primary vector Aedes aegypti.

Dengue is an arthropod-borne viral infection mainly vectored through the bite of Aedes mosquitoes. Recently, its transmission has strongly increased in urban and semi-urban areas of tropical and sub-tropical regions worldwide, becoming a major international public health concern. There is no specific treatment for dengue. Its prevention and control solely depends on effective vector control measures. In this study, we proposed the green-synthesis of silver nanoparticles (AgNP) as a novel and effective tool against the dengue serotype DEN-2 and its major vector Aedes aegypti. AgNP were synthesized using the Moringa oleifera seed extract as reducing and stabilizing agent. AgNP were characterized using a variety of biophysical methods including UV-vis spectroscopy, Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), and sorted for size categories. AgNP showed in vitro antiviral activity against DEN-2 infecting vero cells. Viral titer was 7 log10 TCID50/ml in control (AgNP-free), while it dropped to 3.2 log10 TCID50/ml after a single treatment with 20 µl/ml of AgNP. After 6 h, DEN-2 yield was 5.8 log10 PFU/ml in the control, while it was 1.4 log10 PFU/ml post-treatment with AgNP (20 µl/ml). AgNP were highly effective against the dengue vector A. aegypti, with LC50 values ranging from 10.24 ppm (I instar larvae) to 21.17 ppm (pupae). Overall, this research highlighted the concrete potential of green-synthesized AgNP in the fight against dengue and its primary vector A. aegypti. Further research on structure-activity relationships of AgNP against other dengue serotypes is urgently required.

Predation by Asian bullfrog tadpoles, Hoplobatrachus tigerinus, against the dengue vector, Aedes aegypti, in an aquatic environment treated with mosquitocidal nanoparticles.

Aedes aegypti is a primary vector of dengue and chikungunya. The use of synthetic insecticides to control Aedes populations often leads to high operational costs and adverse non-target effects. Botanical extracts have been proposed for rapid extracellular synthesis of mosquitocidal nanoparticles, but their impact against predators of mosquito larvae has not been well studied. We propose a single-step method for the biosynthesis of silver nanoparticles (AgNP) using the extract of Artemisia vulgaris leaves as a reducing and stabilizing agent. AgNP were characterized by UV-vis spectroscopy, Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), and X-ray diffraction (XRD). SEM and XRD showed that AgNP were polydispersed, crystalline, irregularly shaped, with a mean size of 30-70 nm. EDX confirmed the presence of elemental silver. FTIR highlighted that the functional groups from plant metabolites capped AgNP, stabilizing them over time. We investigated the mosquitocidal properties of A. vulgaris leaf extract and green-synthesized AgNP against larvae and pupae of Ae. aegypti. We also evaluated the predatory efficiency of Asian bullfrog tadpoles, Hoplobatrachus tigerinus, against larvae of Ae. aegypti, under laboratory conditions and in an aquatic environment treated with ultra-low doses of AgNP. AgNP were highly toxic to Ae. aegypti larval instars (I-IV) and pupae, with LC50 ranging from 4.4 (I) to 13.1 ppm (pupae). In the lab, the mean number of prey consumed per tadpole per day was 29.0 (I), 26.0 (II), 21.4 (III), and 16.7 (IV). After treatment with AgNP, the mean number of mosquito prey per tadpole per day increased to 34.2 (I), 32.4 (II), 27.4 (III), and 22.6 (IV). Overall, this study highlights the importance of a synergistic approach based on biocontrol agents and botanical nano-insecticides for mosquito control.

Characterization and biotoxicity of Hypnea musciformis-synthesized silver nanoparticles as potential eco-friendly control tool against Aedes aegypti and Plutella xylostella.

Two of the most important challenges facing humanity in the 21st century comprise food production and disease control. Eco-friendly control tools against mosquito vectors and agricultural pests are urgently needed. Insecticidal products of marine origin have a huge potential to control these pests. In this research, we reported a single-step method to synthesize silver nanoparticles (AgNP) using the aqueous leaf extract of the seaweed Hypnea musciformis, a cheap, nontoxic and eco-friendly material, that worked as reducing and stabilizing agent during the biosynthesis. The formation of AgNP was confirmed by surface plasmon resonance band illustrated in UV-vis spectrophotometer. AgNP were characterized by FTIR, SEM, EDX and XRD analyses. AgNP were mostly spherical in shape, crystalline in nature, with face-centered cubic geometry, and their mean size was 40-65nm. Low doses of H. musciformis aqueous extract and seaweed-synthesized AgNP showed larvicidal and pupicidal toxicity against the dengue vector Aedes aegypti and the cabbage pest Plutella xylostella. The LC50 value of AgNP ranged from 18.14 to 38.23ppm for 1st instar larvae (L1) and pupae of A. aegypti, and from 24.5 to 38.23ppm for L1 and pupae of P. xylostella. Both H. musciformis extract and AgNP strongly reduced longevity and fecundity of A. aegypti and P. xylostella adults. This study adds knowledge on the toxicity of seaweed borne insecticides and green-synthesized AgNP against arthropods of medical and agricultural importance, allowing us to propose the tested products as effective candidates to develop newer and cheap pest control tools.