Eco-friendly control of malaria and arbovirus vectors using the mosquitofish Gambusia affinis and ultra-low dosages of Mimusops elengi-synthesized silver nanoparticles: towards an integrative approach?

Tiny Green Army: Fighting Malaria with Plants and Nanotechnology

Malaria poses a global threat to human health, with millions of cases and thousands of deaths each year, mainly affecting developing countries in tropical and subtropical regions. Malaria's causative agent is Plasmodium species, generally transmitted in the hematophagous act of female Anopheles sp. mosquitoes. The main approaches to fighting malaria are eliminating the parasite through drug treatments and preventing transmission with vector control. However, vector and parasite resistance to current strategies set a challenge. In response to the loss of drug efficacy and the environmental impact of pesticides, the focus shifted to the search for biocompatible products that could be antimalarial. Plant derivatives have a millennial application in traditional medicine, including the treatment of malaria, and show toxic effects towards the parasite and the mosquito, aside from being accessible and affordable. Its disadvantage lies in the type of administration because green chemical compounds rapidly degrade. The nanoformulation of these compounds can improve bioavailability, solubility, and efficacy. Thus, the nanotechnology-based development of plant products represents a relevant tool in the fight against malaria. We aim to review the effects of nanoparticles synthesized with plant extracts on Anopheles and Plasmodium while outlining the nanotechnology green synthesis and current malaria prevention strategies.

Plant-mediated synthesis of silver nanoparticles: unlocking their pharmacological potential-a comprehensive review

In recent times, nanoparticles have experienced a significant upsurge in popularity, primarily owing to their minute size and their remarkable ability to modify physical, chemical, and biological properties. This burgeoning interest can be attributed to the expanding array of biomedical applications where nanoparticles find utility. These nanoparticles, typically ranging in size from 10 to 100 nm, exhibit diverse shapes, such as spherical, discoidal, and cylindrical configurations. These variations are not solely influenced by the manufacturing processes but are also intricately linked to interactions with surrounding stabilizing agents and initiators. Nanoparticles can be synthesized through physical or chemical methods, yet the biological approach emerges as the most sustainable and eco-friendly alternative among the three. Among the various nanoparticle types, silver nanoparticles have emerged as the most encountered and widely utilized due to their exceptional properties. What makes the synthesis of silver nanoparticles even more appealing is the application of plant-derived sources as reducing agents. This approach not only proves to be cost-effective but also significantly reduces the synthesis time. Notably, silver nanoparticles produced through plant-mediated processes have garnered considerable attention in recent years due to their notable medicinal capabilities. This comprehensive review primarily delves into the diverse medicinal attributes of silver nanoparticles synthesized using plant-mediated techniques. Encompassing antimicrobial properties, cytotoxicity, wound healing, larvicidal effects, anti-angiogenesis activity, antioxidant potential, and antiplasmodial activity, the paper extensively covers these multifaceted roles. Additionally, an endeavor is made to provide an elucidated summary of the operational mechanisms underlying the pharmacological actions of silver nanoparticles.

Comparative efficacy of natural aquatic predators for biological control of mosquito larvae: A neglected tool for vector control

Mosquitoes are a dominant fraction of dipteran fauna, occupying a variety of niches. The most common method deployed for their control is the use of insecticides. Throughout their life cycle they are exposed to a wide range of predators in different habitats, thus biological control of mosquitoes by using aquatic predators has been suggested. Therefore, the present study was carried out to explore the type of natural predators coexisting with the mosquito larvae in still water bodies and to determine their efficacy as predators for mosquito larvae. A coexistence of different predators with mosquito larvae was observed in 27 standing water bodies of Chandigarh, India. The predation efficiency of tadpoles of frog was comparable to Gambusia fish, as 97% of the mosquito larvae of all instars of the medically important mosquito genera Anopheles, Aedes, Culex and Armigeres were preyed. The toad tadpoles were found to be least effective and their predation rate was found to be negligible. Further studies on larval source management by frog tadpoles in combination with insecticides or stand-alone would be worthwhile.

Larvicidal activity of green synthesized iron oxide nanoparticles using Grevillea robusta Cunn. leaf extract against vector mosquitoes and their characterization

Extensive fumigation of synthetic pesticides to control the mosquito vector during each post-monsoon season in Pakistan significantly enhanced the environmental contamination and extinction of beneficial insects from the urban ecosystems. In this context, the present study examined the larvicidal efficacy of green synthesized iron nanoparticles (IONPs), using an aqueous leaf extract of Grevillea robusta against the early 2nd and 4th instar larvae of Aedes aegypti and Anopheles stephensi in Pakistan. The prepared IONPs were characterized by UV-Vis spectrum, FTIR, X-ray diffraction, scanning electron microscopy, and energy-dispersive diffraction. Larvicidal bioassay was conducted at various concentrations (80, 160, 240, 320, and 400 ppm) of IONPs prepared from leaf extract of G. robusta, and readings were taken-every 12 h for two consecutive days. In vitro, larvicidal assay, G. robusta leaf extract IONPs exhibited high mortalities of 64-96% (LC50 = 259.07 ppm; LC90 = 443.92 ppm) for the second instar and 65-98% (LC50 = 238.05 ppm; LC90 = 433.93 ppm) for the fourth instar of Ae. aegypti, while in the case of An. stephensi 56-84% (LC50 = 297.96 ppm; LC90 = 528.69 ppm) for the second and 56-88% (LC50 = 292.72 ppm; LC90 = 514.00 ppm) mortality for fourth larvae at 12-48 h post-exposure times were observed respectively. Significant (p < 0.05) dose-dependent and exposure time-dependent trends were observed among the 2nd and 4th larvalinstar of An. stephensi and Ae. aegypti. However, both species showed similar response and observed no significant (p > 0.05) difference in percentage mortality between the vector mosquitoes An. stephensi and Ae. aegypti. Overall, this study demonstrates that the larvicidal efficacy of green synthesized IONPs at low concentrations can be an ideal eco-friendly and cost-effective biocontrol of vector mosquitoes' larvae of An. stephensi and Ae. aegypti.

Synergistic antibacterial and mosquitocidal effect of Passiflora foetida synthesized silver nanoparticles

Silver nanoparticles are opted to have various applications in different fields ranging from traditional medicines to culinary items. It is toxic and most effective against bacteria, fungi viruses, parasites, parasite carrying vectors such as mosquitoes and their larvae and other eukaryotic microorganisms at low concentration without any side effects and toxicity to humans. In view of these data, the present research has been investigated by synthesizing silver nanoparticles using 1mM silver nitrate and aqueous extract of Passiflora foetida. The variation of nanoparticles in size and shape concerning the concentration of extract prepared were analysed. The formation of silver nanoparticles was confirmed by colour changing from yellowish green to reddish-brown implicating the surface plasmon resonance. Further, it was concluded by obtaining an absorbance peak at 420 nm using UV-Visible spectrophotometer analysis. FTIR analysis was used to identify the capping ligands, which included alkanes, aromatic groups and nitro compounds. The average grain size of ~12 nm to 14 nm with crystalline phase was revealed by X-ray Diffraction studies. The SEM images depicted the surface morphology with agglomeration; TEM studies showed the shape of nanoparticles as spherical and hexagonal with sizes ranging from 40 nm to 100 nm and EDAX analysis confirmed the presence of elemental silver as the principal constituent. The characterized silver nanoparticles were then tested for synergistic antibacterial effects with tetracycline, and the results show that they are more active against E. coli and S. aureus, but moderately effective against B. cereus and K. pneumoniae . It also had a strong larval and pupal toxic effects on the dengue vector, Aedes aegypti with the highest mortality. As a result, silver nanoparticles could be a viable alternative for a variety of applications.

Perspectives of vector management in the control and elimination of vector-borne zoonoses

The complex transmission profiles of vector-borne zoonoses (VZB) and vector-borne infections with animal reservoirs (VBIAR) complicate efforts to break the transmission circuit of these infections. To control and eliminate VZB and VBIAR, insecticide application may not be conducted easily in all circumstances, particularly for infections with sylvatic transmission cycle. As a result, alternative approaches have been considered in the vector management against these infections. In this review, we highlighted differences among the environmental, chemical, and biological control approaches in vector management, from the perspectives of VZB and VBIAR. Concerns and knowledge gaps pertaining to the available control approaches were discussed to better understand the prospects of integrating these vector control approaches to synergistically break the transmission of VZB and VBIAR in humans, in line with the integrated vector management (IVM) developed by the World Health Organization (WHO) since 2004.

Phytoconstituents Assisted Biofabrication of Copper Oxide Nanoparticles and Their Antiplasmodial, and Antilarval Efficacy: A Novel Approach for the Control of Parasites

The present work aimed to biofabricate copper oxide nanoparticles (CuO NPs) using Tinospora cordifolia leaf extract. The biofabricated CuO NPs were treated against the malarial parasite of chloroquine-resistant Plasmodium falciparum (INDO) and the antilarval efficacy was evaluated against the malaria vector Anopheles stephensi and dengue vector Aedes aegypti. The prominence at 285 nm in the UV-visible spectrum helped to identify the produced CuO NPs. Based on the XRD patterns, the concentric rings correspond to reflections at 38.26° (111), 44.11° (200), 64.58° (220), and 77.34° (311). These separations are indicative of CuO's face-centered cubic (fcc) structure. The synthesized CuO NPs have FTIR spectra with band intensities of 3427, 2925, 1629, 1387, 1096, and 600 cm^-1. The absorbance band at 3427 cm^-1 is known to be associated with the stretching O-H due to the alcoholic group. FTIR proved that the presence of the -OH group is responsible for reducing and capping agents in the synthesis of nanoparticles (NPs). The synthesized CuO NPs were found to be polymorphic (oval, elongated, and roughly spherical) in form with a size range of 11-47 nm and an average size of 16 nm when the morphology was examined using FESEM and HRTEM. The highest antiplasmodial efficacy against the chloroquine-resistant strain of P. falciparum (INDO) was found in the synthesized CuO NPs, with LC₅₀ values of 19.82 µg/mL, whilst HEK293 cells are the least toxic, with a CC₅₀ value of 265.85 µg/mL, leading to a selectivity index of 13.41. However, the antiplasmodial activity of T. cordifolia leaf extract (TCLE) and copper sulfate (CS) solution showed moderate activity, with LC₅₀ values of 52.24 and 63.88 µg/mL, respectively. The green synthesized NPs demonstrated extremely high antilarval efficacy against the larvae of An. stephensi and Ae. aegypti, with LC₅₀ values of 4.06 and 3.69 mg/L, respectively.

Transgenic cytoplasmic incompatibility persists across age and temperature variation in Drosophila melanogaster

Environmental stressors can impact the basic biology and applications of host-microbe symbioses. For example, Wolbachia symbiont densities and cytoplasmic incompatibility (CI) levels can decline in response to extreme temperatures and host aging. To investigate whether transgenic expression of CI-causing cif genes overcomes the environmental sensitivity of CI, we exposed transgenic male flies to low and high temperatures as well as aging treatments. Our results indicate that transgenic cif expression induces nearly complete CI regardless of temperature and aging, despite severe weakening of Wolbachia-based wild-type CI. Strong CI levels correlate with higher levels of cif transgene expression in young males. Altogether, our results highlight that transgenic CI persists against common environmental pressures and may be relevant for future control applications involving the cifA and cifB transgenes.

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Symbiont adaptations are often weakened by life history and environmental parameters

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Cytoplasmic incompatibility (CI) declines with host age and temperature

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Transgenic CI is robust to age and temperature variation in Drosophila melanogaster

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Transgenic CI circumvents pressures that diminish wildtype CI

Efficacy of metal nanoparticles as a control tool against adult mosquito vectors: A review

Presently, there is a need to develop effective and novel modes of control for mosquitoes, which remain a key driver of infectious disease transmission throughout the world. Control methods for these vectors have historically relied on a limited number of active ingredients (AIs) that have not experienced significant change in usage since the mid-20th century. The resulting development of widespread insecticide resistance has consequently increased the risk for future vector-borne disease outbreaks. Recently, metal nanoparticles have been explored for potential use in mosquito control due to their demonstrated toxicity against mosquitoes at all life stages. However, the majority of studies to date have focused on the larvicidal efficacy of metal nanoparticles with few studies examining their adulticidal potential. In this review, we analyze the current literature on green synthesized metal nanoparticles and their effect on adult mosquitoes.

Green Nano-Biotechnology: A New Sustainable Paradigm to Control Dengue Infection

Dengue is a growing mosquito-borne viral disease prevalent in 128 countries, while 3.9 billion people are at high risk of acquiring the infection. With no specific treatment available, the only way to mitigate the risk of dengue infection is through controlling of vector, i.e., Aedes aegypti. Nanotechnology-based prevention strategies like biopesticides with nanoformulation are now getting popular for preventing dengue fever. Metal nanoparticles (NPs) synthesized by an eco-friendly process, through extracts of medicinal plants have indicated potential anti-dengue applications. Green synthesis of metal NPs is simple, cost-effective, and devoid of hazardous wastes. The recent progress in the phyto-synthesized multifunctional metal NPs for anti-dengue applications has encouraged us to review the available literature and mechanistic aspects of the dengue control using green-synthesized NPs. Furthermore, the molecular bases of the viral inhibition through NPs and the nontarget impacts or hazards with reference to the environmental integrity are discussed in depth. Till date, major focus has been on green synthesis of silver and gold NPs, which need further extension to other innovative composite nanomaterials. Further detailed mechanistic studies are required to critically evaluate the mechanistic insights during the synthesis of the biogenic NPs. Likewise, detailed analysis of the toxicological aspects of NPs and their long-term impact in the environment should be critically assessed.

A comprehensive phytochemical and pharmacological review on sesquiterpenes from the genus Ambrosia

Sesquiterpenes are bitter secondary metabolites characteristic to the genus Ambrosia (Asteraceae) and constitute one of the most diverse classes of terpenoids. These compounds exhibit broad-spectrum bioactivities, such as antiproliferative, cytotoxic, antimicrobial, anti-inflammatory, molluscicidal, schistomicidal, larvicidal, and antiprotozoal activities. This review compiles and discusses the chemistry and pharmacology of sesquiterpenes of the Ambrosia species covering the period between 1950 and 2021. The review identified 158 sesquiterpenes previously isolated from 23 different Ambrosia species collected from across the American, African, and Asian continents. These compounds have guaiane, pseudoguaiane, seco-pseudoguaiane, daucane, germacrane, eudesmane, oplopane, clavane, and aromadendrane carbon skeletons. Most sesquiterpene compounds predominantly harbor the pseudoguaiane skeleton, whereas the eudesmanes have the most varied substituents. Antiproliferative and antiprotozoal activities are the most promising bioactivities of sesquiterpenes in Ambrosia and could lead to new pathways toward drug discovery.

ٍSome biologically active microorganisms have the potential to suppress mosquito larvae (Culex pipiens, Diptera: Culicidae)

Malaria is a disease caused by protozoan species of the genus Plasmodium. It is widespread and becoming a challenge in several African countries in the tropical and subtropical regions. In 2010, a report was published showing that over 1.2 million death cases were occurred globally due to malaria in just one year. The transmission of the disease from one person to another occurs via the bite of the Anopheles female. It is known that Plasmodium ovale, P. vivax, P. malariae, P. falciparum, and P. knowlesi are the highly infective malaria species. The problem of this disease is the absence of any effective medical treatment or vaccine, making the mosquito control is the only feasible way for disease prevention. Pesticides are currently the most widely used method for mosquito control, despite its well-known negative effects, including health hazards on human, the increasing insecticidal resistance, and the negative impact on the environment and beneficial organisms. Biological control (also called: biocontrol) of insects has been a promising method to overcome the negative effects of using chemical insecticides, as it depends on just using the natural enemies of pests to either minimize their populations or eradicate them. This article provides an overview of the recent and effective biological means to control malaria, such as bacteria, fungi, viruses, larvivorous fish, toxorhynchites larva and nematodes. In addition, the importance, advantages, and disadvantages of the biocontrol methods will be discussed in comparison with the traditionally used chemical methods of malaria control with special reference to nanotechnology as a novel method for insects’ control.

Efficacy and side effects of bio-fabricated sardine fish scale silver nanoparticles against malarial vector Anopheles stephensi

Mosquitoes are a great menace for humankind since they transmit pathogenic organisms causing Malaria, Dengue, Chikungunya, Elephantiasis and Japanese encephalitis. There is an urgent need to discover new and novel biological tools to mitigate mosquito-borne diseases. To develop bioinsecticides through newly developed nanotechnology is another option in the present research scenario. In this study we synthesize and characterize sardine fish scales with silver nitrate by adopting various instrumental techniques such as UV- and FTIR-spectroscopy, energy-dispersive X-ray (EDAX), X-ray diffraction analyses (XRD) and scanning electron microscopy (SEM). Toxicity bioassays were conducted with young developmental stages of mosquito vectors. Significant mortality appeared after different life stages of mosquito vectors (young larval and pupal instars were exposed to the nanomaterials). LC50 values were 13.261 ppm for young first instar larvae and 32.182 ppm for pupae. Feeding and predatory potential of G. affinis, before and after exposure to nanoparticles against mosquito larval (I & II) instars of the mosquitoes showed promising results in laboratory experiments. Feeding potential of mosquito fish without nanoparticle treatment was 79.7% and 70.55% for the first and second instar larval populations respectively. At the nanoparticle-exposed situation the predatory efficiency of mosquitofish was 94.15% and 84.3%, respectively. Antioxidant enzymes like (SOD), (CAT), and (LPO) were estimated in the gill region of sardine fish in control and experimental waters. A significant reduction of egg hatchability was evident after nanoparticle application. It became evident from this study that the nano-fabricated materials provide suitable tools to control the malaria vector Anopheles stephensi in the aquatic phase of its life cycle. This finding suggests an effective novel approach to mosquito control.

Adult damselflies as possible regulators of mosquito populations in urban areas

BACKGROUND

Dragonfly and damselfly larvae have been considered as possible biocontrol agents against young instars of mosquito vectors in urban environments. Yet our knowledge about adult odonate predation against mosquito adults is scarce. We quantified daily and annual predation rates, consumption rates and prey preferences of adult Hetaerina vulnerata male damselflies in an urban park. A focus on predation of mosquito species was provided, quantified their arbovirus (dengue, chikungunya and Zika) infection rates and biting activity.

RESULTS

Foraging times of H. vulnerata overlapped with those of the maximum activity of hematophagous mosquitoes. The most consumed preys were Diptera and Hymenoptera and, in lower quantities, Hemiptera, Coleoptera, Trichoptera, Psocoptera and Neuroptera. Of note, 7% of the diet was represented by hematophagous dipterans, with 2.4% being Aedes aegypti and Aedes albopictus. Prey abundance in the diet coincided with that of the same species in the environment. The arboviral infection rate (dengue, chikungunya and Zika) was 1.6% for A. aegypti and A. albopictus. The total biting rate of these mosquito vectors was 16 bites per person per day, while the annual rate of infectious bites was 93.4.

CONCLUSION

Although 2.4% for both Aedes species seems a low consumption, considering the presence of 12 odonate species at the park, it can be argued that adult odonates may play a relevant role as mosquito vector regulators, therefore impacting the spread of mosquito-borne diseases. Our study outlines the need for further research on the topic of the possible role of adult odonates for mosquito biocontrol. © 2021 Society of Chemical Industry.

Zinc oxide nanoparticles using plant Lawsonia inermis and their mosquitocidal, antimicrobial, anticancer applications showing moderate side effects

Microbes or parasites spread vector-borne diseases by mosquitoes without being affected themselves. Insecticides used in vector control produce a substantial problem for human health. This study synthesized zinc oxide nanoparticles (ZnO NPs) using Lawsonia inermis L. and were characterized by UV-vis, FT-IR, SEM with EDX, and XRD analysis. Green synthesized ZnO NPs were highly toxic against Anopheles stephensi, whose lethal concentrations values ranged from 5.494 ppm (I instar), 6.801 ppm (II instar), 9.336 ppm (III instar), 10.736 ppm (IV instar), and 12.710 ppm (pupae) in contrast to L. inermis treatment. The predation efficiency of the teleost fish Gambusia affinis and the copepod Mesocyclops aspericornis against A. stephensi was not affected by exposure at sublethal doses of ZnO NPs. The predatory potency for G. affinis was 45 (I) and 25.83% (IV), copepod M. aspericornis was 40.66 (I) and 10.8% (IV) while in an ZnO NPs contaminated environment, the predation by the fish G. affinis was boosted to 71.33 and 34.25%, and predation of the copepod M. aspericornis was 60.35 and 16.75%, respectively. ZnO NPs inhibited the growth of several microbial pathogens including the bacteria (Escherichia coli and Bacillus subtilis) and the fungi (Alternaria alternate and Aspergillus flavus), respectively. ZnO NPs decreased the cell viability of Hep-G2 with IC50 value of 21.63 µg/mL (R2 = 0.942; P < 0.001) while the concentration increased from 1.88 to 30 µg/mL. These outcomes support the use of L. inermis mediated ZnO NPs for mosquito control and drug development.

Green-synthesized metal nanoparticles for mosquito control: A systematic review about their toxicity on non-target organisms

Studies capturing the high efficiency of green-synthesized metal nanoparticles (NPs) in targeting mosquito vectors of the world's main infectious diseases suggest the NPs' possible utilization as bio-insecticides. However, it is necessary to confirm that these potential bio-insecticides are not harmful to non-target organisms that are often sympatric and natural enemies of the vectors of these diseases. In this systematic review, we comprehensively analyse the content of 56 publications focused on the potentially deleterious effects of NPs on these non-target organisms. Current research on biosynthesised NPs, characterization, and impact on mosquito vectors and non-target larvivorous organisms is reviewed and critically discussed. Finally, we pinpoint some major challenges that merit future investigation. Plants (87.5%) were mainly used for synthesizing NPs in the studies. NPs were found to be spherical or mainly spherical in shape with a large distribution size. In most of the included studies, NPs showed interesting mosquitocidal activity (LC₅₀ < 50 ppm). Some plant families (e.g., Meliaceae, Poaceae, Lamiaceae) have produced NPs with a particularly high larvicidal and pupicidal activity (LC₅₀ < 10 ppm). Regarding non-target organisms, most of the studies concluded that NPs were safe to them, with boosted predatory activity in NP-treated milieu. In contrast, some studies reported NP-elicited adverse effects (i.e., genotoxic, nuclear, and enzymatic effects) on these non-target organisms. This review outlines the promising mosquitocidal effects of biosynthesized NPs, recognizing that NPs' potential usage is currently limited by the harm NPs are thought pose to non-target organism. It is of utmost importance to investigate green NPs to determine whether laboratory findings have applications in the real world.

Evaluation of Larvicidal Efficacy of Ricinus communis (Castor) Plant Extract and Synthesized Green Silver Nanoparticles against Aedes albopictus

Background

Aedes mosquitoes are the most important group of vectors having ability of transmitting pathogens including arboviruses that can cause serious diseases like Chikungunya fever, Dengue fever and Zika virus in human. Biosynthesis and the use of green silver nanoparticles (AgNPs) is an important step in the search of reliable and ecofriendly control of these vectors.

Methods

In this study an aqueous leaves extract of Ricinus communis (castor) and silver nanoparticles (AgNPs) synthesized from this extract were evaluated as larvicidal agent for 2^nd and 3^rd instar larvae of the Aedes albopictus. Different concentrations (50, 100, 150, 200 and 250ppm) of plant extract and synthesized nanoparticles were prepared and applied on second and third instar larvae. The percent mortality was noted after 6, 12, 18, 24, 30, 36, 42 and 48H of exposure and subjected to probit analysis to calculate LC₅₀ and LC₉₀.

Results

Synthesized Ag⁺ nanoparticles were characterized by UV-Vis spectroscopy, Fourier transform infrared spectroscopy (FT-IR), and energy-dispersive X-ray spectroscopy (XRD). The nanoparticles were more toxic against larvae of Ae. albopictus with LC₅₀ value (49.43ppm) and LC₉₀ value (93.65ppm) for 2^nd instar larvae and LC₅₀ (84.98ppm) and LC₉₀ (163.89ppm) for 3^rd instar larvae as compared to the plant extract (149.58ppm, 268.93ppm) and (155.58ppm, 279.93ppm) for 2^nd and 3^rd instar larvae of Ae. albopictus respectively after 48H.

Conclusion

Our results suggest the extract of R. communis and synthesized nanoparticles as excellent replacement of chemical pesticides to control the vector mosquitoes.

Silver Nanoparticles: Mechanism of Action and Probable Bio-Application

This review is devoted to the medical application of silver nanoparticles produced as a result of "green" synthesis using various living organisms (bacteria, fungi, plants). The proposed mechanisms of AgNPs synthesis and the action mechanisms on target cells are highlighted.

Dye degradation, antimicrobial and larvicidal activity of silver nanoparticles biosynthesized from Cleistanthus collinus

The present study aimed in green synthesis and characterization of silver nanoparticles (AgNPs) using the leaves of Cleistanthus collinus. The NPs showed various absorption peaks between 3402 cm-1 and 1063 cm-1. FTIR spectrum revealed the presence of OH group, alkene, aromatic hydrocarbon, aliphatic fluro compound and aliphatic chloro compounds. Scanning electron microscopic analysis revealed the particle size ranged from 30 to 50 nm. The biosynthesized NPs have potent activity against Shigella dysentriae, Staphylococcus aureus and Bacillus subtilis and the zone of inhibition was 21 ± 1, 20 ± 2, 16 ± 2 mm, respectively. Toxicity of the synthesized NPs was tested on green gram (Vigna radiata) seed at various concentrations (20-100%) and germination was induced by NPs treated seeds. Shoot length and root length was higher in NPs treated plant than control plant (p < 0.01). Elevated level of catalase (CAT) and superoxide dismutase (SOD) and about 13% CAT and 7% SOD activity registered than control. Superoxide dismutase activity of root and shoot varied based on the dosage of AgNPs (p < 0.01). Also, the NPs (1%) showed significant larvicidal activity on Aedes aegypti and 100% mortality was achieved after 24 h treatment. The green synthesized NPs reduced methylene blue and 4-nitrophenol significantly (p < 0.01). The colouration of methylene blue and 4-nitrophenol were considerably reduced after 60 min showed the potential of dye degrading ability.

Comparative study on larvicidal activity of green synthesized silver nanoparticles and Annona glabra (Annonaceae) aqueous extract to control Aedes aegypti and Aedes albopictus (Diptera: Culicidae)

The present study reports mosquito larvicidal potential of green synthesized silver nanoparticles by using Annona glabra leaves (An-AgNPs). Synthesized An-AgNPs were characterized by Ultraviolet-Visible spectroscopy (UV-VIS), Scanning Electron Microscopy (SEM), Dynamic Light Scattering (DLS) technique and Fourier transform infrared spectroscopy (FTIR). Colur change from pale yellow to brick red of the plant extract and AgNO3 solution indicated the formation of An-AgNPs initially. Surface Plasmon Resonance (SPR) band at 435 nm in the UV-Vis confirmed the formation of An-AgNPs. SEM images showed that An-AgNPs were spherical in shape. FTIR proved that An-AgNPs were functionalized with biomolecules in A. glabra leaves. Based on DLS analysis the average size range of synthesized An-AgNPs was determine to be 10-100 nm and 100-1000 nm. Third instar larvae of dengue vector mosquitoes, Aedes aegypti and Aedes albopictus were subjected to larvicidal bioassays in a range of concentrations of An-AgNPs and A. glabra crude aqueous leaf extract (2-10 mg/L). An-AgNPs exhibited very high larvicidal activity against dengue vector mosquito larvae; LC50 value for Ae. aegypti at 24 h exposure to An-AgNPs (Plant extract: AgNO3 1 : 10) 5.29 mg/L; An-AgNPs (Plant extract: AgNO3 2 : 10) 2.43 mg/L while LC50 value for Ae. albopictus at 24 h exposure to An-AgNPs (Plant extract: AgNO31:10) 3.02 mg/L; An-AgNPs (Plant extract: AgNO3 2:10) 2.51 mg/L. LC50 values obtained for A. glabra leaf extract tested against Ae. aegypti and Ae. albopictus are 5.94 mg/L and 5.00 mg/L respectively at 24-hour exposure. This study further revealed that Ae. albopictus is more susceptible than to Ae. aegypti to a given concentration of An-AgNPs and to crude aqueous leaf extract of A. glabra. Larvicidal effect of An-AgNPs is superior to the crude aqueous leaf extract of A. glabra. An-AgNPs is a potent larvicide for dengue vector control.

Phytochemical analysis of Rhazya stricta extract and its use in fabrication of silver nanoparticles effective against mosquito vectors and microbial pathogens

Worldwide, billions of people are at risk from viruses, parasites and bacteria transmitted by mosquitoes, ticks, fleas and other vectors. Over exploitation of chemical pesticides to overcome the mosquito borne diseases led to detrimental effects on environment and human health. The present research aims to explore bio-fabrication of metal silver nanomaterials using Rhazya stricta extract against deadly mosquito vectors and microbial pathogens. The phytochemical profile of the R. stricta extracts was studied by HPLC-MS and ¹H NMR. Further, confirmation of the bio-fabricated silver nanoparticles (AgNPs) was carried out by UV-vis spectroscopy and characterization through FTIR, TEM, EDX, and XRD analyses. The R. stricta-fabricated AgNPs showed acute toxicity on key mosquito vectors from two different country (India and Kingdom of Saudi Arabia, KSA) strains, notably, with LC₅₀ values of 10.57, 11.89 and 12.78 μg/ml on malarial, dengue and filarial key Indian strains of mosquito vectors, respectively, and 30.66 and 38.39 μg/ml on KSA strains of Aedes aegypti and Culex pipiens, respectively. In mosquito adulticidal activity, R. stricta extract alone exhibited LC₅₀ values ranging from 304.34 to 382.45 μg/ml against Indian strains and from 738.733 to 886.886 against Saudi Arabian strains, while AgNPs LC₅₀ boosted from 9.52 to 12.16 μg/ml and from 30.66 to 38.39 μg/ml, respectively. Moreover, it was noticed that at low concentration the tested AgNPs showed high growth retardation of important pathogenic bacteria such as Bacillus subtilis, Klebsiella pneumoniae and Salmonella typhi with inhibition zone diameters from 11.86 to 22.92 mm. In conclusion, the present study highlighted that R. stricta-fabricated AgNPs could be a lead material for the management of mosquito vector and microbial pathogens control.

Green synthesis of silver nanoparticles using Solanum mammosum L. (Solanaceae) fruit extract and their larvicidal activity against Aedes aegypti L. (Diptera: Culicidae)

The family of mosquitoes (Diptera: Culicidae) contains several species of major public health relevance due to their role as vectors of human disease. One of these species, Aedes aegypti, is responsible for the transmission of some of the most important vector-borne viruses affecting humankind, including dengue fever, chikungunya and Zika. Traditionally, control of Ae. aegypti and other arthropod species has relied on the use of a relatively small diversity of chemical insecticides. However, widespread and intensive use of these substances has caused significant adverse environmental effects and has contributed to the appearance of pesticide-resistant populations in an increasing number of locations around the world, thereby dramatically reducing their efficiency. Therefore, it becomes urgent to develop novel alternative tools for vector control. In that context, our study aimed at evaluating the insecticidal activity against Ae. aegypti of aqueous extracts obtained from the fruits of Solanum mammosum L., as well as silver nanoparticles synthesized using aqueous extracts from this plant species (SmAgNPs). To perform the test, third instar Ae. aegypti larvae were exposed to increasing concentrations of plant extract and SmAgNPs for 24 h. Our results suggest that both the aqueous extract and SmAgNPs were toxic to the larvae, with SmAgNPs displaying a much higher level of toxicity than the extract alone, as reflected in their LC₅₀ values (0.06 ppm vs 1631.27 ppm, respectively). These results suggest that both S. mammosum extracts and SmAgNPs exhibit noteworthy larvicidal activity, and should be further explored as potential source of alternative tools in the fight against insect vectors of human disease.

Plant extracts for developing mosquito larvicides: From laboratory to the field, with insights on the modes of action

In the last decades, major research efforts have been done to investigate the insecticidal activity of plant-based products against mosquitoes. This is a modern and timely challenge in parasitology, aimed to reduce the frequent overuse of synthetic pesticides boosting resistance development in mosquitoes and causing serious threats to human health and environment. This review covers the huge amount of literature available on plant extracts tested as mosquito larvicides, particularly aqueous and alcoholic ones, due to their easy formulation in water without using surfactants. We analysed results obtained on more than 400 plant species, outlining that 29 of them have outstanding larvicidal activity (i.e., LC₅₀ values below 10 ppm) against major vectors belonging to the genera Anopheles, Aedes and Culex, among others. Furthermore, synergistic and antagonistic effects between plant extracts and conventional pesticides, as well as among selected plant extracts are discussed. The efficacy of pure compounds isolated from the most effective plant extracts and - when available - their mechanism of action, as well as the impact on non-target species, is also covered. These belong to the following class of secondary metabolites: alkaloids, alkamides, sesquiterpenes, triterpenes, sterols, flavonoids, coumarins, anthraquinones, xanthones, acetogenonins and aliphatics. Their mode of action on mosquito larvae ranges from neurotoxic effects to inhibition of detoxificant enzymes and larval development and/or midugut damages. In the final section, current drawbacks as well as key challenges for future research, including technologies to synergize efficacy and improve stability - thus field performances - of the selected plant extracts, are outlined. Unfortunately, despite the huge amount of laboratory evidences about their efficacy, only a limited number of studies was aimed to validate their efficacy in the field, nor the epidemiological impact potentially arising from these vector control operations has been assessed. This strongly limits the development of commercial mosquito larvicides of botanical origin, at variance with plant-borne products developed in the latest decades to kill or repel other key arthropod species of medical and veterinary importance (e.g., ticks and lice), as well as mosquito adults. Further research on these issues is urgently needed.

Evaluation of Pistia stratiotes fractions as effective larvicide against Anopheles mosquitoes

Mosquito are well-known vectors that cause diseases particularly malaria and filariasis which are detrimental to human health. These vectors occur mainly in tropical countries where more than 2 billion people live in endemic regions with about one million deaths been claimed yearly from malaria and filariasis. The study is aimed at evaluating the larvicidal activity of Pistia stratiotes fractions on Anopheles mosquitoes (Diptera: Culicidae). The ethyl acetate extract of P. stratiotes was obtained through percolation process and was chromatographed to yield nine fractions. The larvicidal activity of each of the nine fractions was tested in triplicates by exposing the larvae to 500, 250, 125, 62.5 and 31.3 µg/ml, respectively. Phytochemical screening of the nine fractions revealed the presence of alkaloids, flavonoids, glycosides and phlobatannins in varying quantities. The result obtained shows that fraction E has the highest lethal effect on the Anopheles larvae at LC₅₀ =14.81 µg/ml and was weakly effective at 602.03 µg/ml on brine shrimp larvae. The gas chromatography mass spectrometry analysis of fraction E revealed the presence of 35 pre-cursor compounds. Hence, ethyl acetate fractions of P. stratiotes could be an effective larvicide against Anopheles mosquito larvae as it has been found to be harmless to other aquatic organisms. Further work should be done on other aquatic weeds that have larvicidal potential to isolate the bioactive compounds.

First detection of Erysipelothrix sp. infection in western mosquitofish Gambusia affinis inhabiting catfish aquaculture ponds in Mississippi, USA

Native and introduced fish can serve as reservoirs for pathogens of cultured fish species. In the current study, 351 archived western mosquitofish Gambusia affinis collected from experimental catfish production ponds in Mississippi, USA, were surveyed histologically to evaluate their potential as vectors for fish pathogens. In addition to epitheliocystis and multiple metazoan parasites, 8 fish had widespread basophilic colonies of small Gram-positive rods associated primarily with stroma supporting the skeletal muscle and bone, as well as connective tissue components of other tissues and organ systems, such as perivascular adventitia and basement membranes. These findings were consistent with spaC-type Erysipelothrix sp. infections in ornamental fish cultured in the USA. The 16S rRNA, gyrase B (gyrB), and surface protective antigen (spa) genes were amplified and sequenced from bacterial colonies excised from paraffin-embedded tissue sections using laser capture microdissection. Molecular data confirmed the identity of a spaC-type Erysipelothrix sp., which grouped phylogenetically with spaC-type Erysipelothrix sp. from diseased ornamental fish. Given the significance of commercial catfish aquaculture in the southeastern USA and the widespread distribution of mosquitofish in catfish ponds throughout the region, infectivity trials with channel catfish Ictalurus punctatus were conducted. Catfish fingerlings were exposed to a spaC-type Erysipelothrix sp. isolate by intracoelomic injection and gavage. No mortality was observed in catfish exposed by either route, and surviving fish demonstrated no significant histopathologic lesions, suggesting channel catfish have low susceptibility to the bacteria. Further research is warranted to investigate the susceptibility of other cultured fish species to this emergent fish pathogen.

Biological nanopesticides: a greener approach towards the mosquito vector control

Mosquitoes, being a vector for some potentially dreadful diseases, pose a considerable threat to people all around the world. The control over the growth and propagation of mosquitoes comprises conventional pesticides, insect growth regulators and other microbial control agents. However, the usage of these common chemicals and conventional pesticides eventually has a negative impact on human health as well as the environment, which therefore becomes a major concern. The lacuna allows nanotechnology to come into action and exploit nanopesticides. Nanopesticides are majorly divided into two categories-synthetic and biological. Several nanoformulations serve as a promising nanopesticide viz. nanoparticles, e.g. biologically synthesised nanoparticles through plant extracts, nanoemulsions prepared using the essential oils like neem oil and citronella oil and nanoemulsion of conventional pesticides like pyrethroids. These green approaches of synthesising nanopesticides make use of non-toxic and biologically derived compounds and hence are eco-friendly with a better target specificity. Even though there are numerous evidences to show the effectiveness of these nanopesticides, very few efforts have been made to study the possible non-target effects on other organisms prevalent in the aquatic ecosystem. This study focuses on the role of these nanopesticides towards the vector control and its eco-safe property against the other non-target species.

High toxicity of camphene and γ-elemene from Wedelia prostrata essential oil against larvae of Spodoptera litura (Lepidoptera: Noctuidae)

The development of eco-friendly biopesticides in the fight against agricultural pests is an important challenge nowadays. The essential oil of Wedelia prostrata Hemsl. is known for its multipurpose biological activities in Chinese folk medicine. However, limited efforts attempted to understand the potential insecticidal activity of its main individual constituents and related mechanism of action. In this research, we investigated the insecticidal activity of W. prostrata against the crop pest Spodoptera litura (Fabricius) (Lepidoptera: Noctuidae). Toxicity on 4th instar larvae was assessed after 24 h of exposure. The LC₅₀ and LC₉₀ of the W. prostrata essential oil were 167.46 and 322.12 μg/ml, respectively. GC-MS analyses were carried out to shed light on the oil chemical composition. Main constituents were the monoterpene camphene (9.6%) and the sesquiterpenes γ-elemene (7.6%), α-humulene (6.9%), and (E,E)-α-farnesene (7.3%). The pure constituents were evaluated for their insecticidal activity on S. litura 4th instar larvae. The most toxic molecule was camphene (LC₅₀ = 6.28 μg/ml), followed by γ-elemene, (LC₅₀ = 10.64 μg/ml), α-humulene (LC₅₀ = 12.89 μg/ml), and (E,E)-α-farnesene (LC₅₀ = 16.77 μg/ml). Overall, our experiments highlighted the promising potential of camphene and γ-elemene from W. prostrata essential oil against larvae of S. litura, allowing us to propose these two compounds for the development of newer pesticides in the fight against crop pests. Further studies aimed at evaluating the potential synergy between these two molecules, as well as their stability in field conditions are ongoing.

Mosquito control with green nanopesticides: towards the One Health approach? A review of non-target effects

The rapid spread of highly aggressive arboviruses, parasites, and bacteria along with the development of resistance in the pathogens and parasites, as well as in their arthropod vectors, represents a huge challenge in modern parasitology and tropical medicine. Eco-friendly vector control programs are crucial to fight, besides malaria, the spread of dengue, West Nile, chikungunya, and Zika virus, as well as other arboviruses such as St. Louis encephalitis and Japanese encephalitis. However, research efforts on the control of mosquito vectors are experiencing a serious lack of eco-friendly and highly effective pesticides, as well as the limited success of most biocontrol tools currently applied. Most importantly, a cooperative interface between the two disciplines is still lacking. To face this challenge, we have reviewed a wide number of promising results in the field of green-fabricated pesticides tested against mosquito vectors, outlining several examples of synergy with classic biological control tools. The non-target effects of green-fabricated nanopesticides, including acute toxicity, genotoxicity, and impact on behavioral traits of mosquito predators, have been critically discussed. In the final section, we have identified several key challenges at the interface between "green" nanotechnology and classic biological control, which deserve further research attention.

Biosurfactants produced by Bacillus subtilis A1 and Pseudomonas stutzeri NA3 reduce longevity and fecundity of Anopheles stephensi and show high toxicity against young instars

Anopheles stephensi acts as vector of Plasmodium parasites, which are responsible for malaria in tropical and subtropical areas worldwide. Currently, malaria management is a big challenge due to the presence of insecticide-resistant strains as well as to the development of Plasmodium species highly resistant to major antimalarial drugs. Therefore, the present study focused on biosurfactant produced by two bacteria Bacillus subtilis A1 and Pseudomonas stutzeri NA3, evaluating them for insecticidal applications against malaria mosquitoes. The produced biosurfactants were characterized using FT-IR spectroscopy and gas chromatography-mass spectrometry (GC-MS), which confirmed that biosurfactants had a lipopeptidic nature. Both biosurfactants were tested against larvae and pupae of A. stephensi. LC₅₀ values were 3.58 (larva I), 4.92 (II), 5.73 (III), 7.10 (IV), and 7.99 (pupae) and 2.61 (I), 3.68 (II), 4.48 (III), 5.55 (IV), and 6.99 (pupa) for biosurfactants produced by B. subtilis A1 and P. stutzeri NA3, respectively. Treatments with bacterial surfactants led to various physiological changes including longer pupal duration, shorter adult oviposition period, and reduced longevity and fecundity. To the best of our knowledge, there are really limited reports on the mosquitocidal and physiological effects due to biosurfactant produced by bacterial strains. Overall, the toxic activity of these biosurfactant on all young instars of A. stephensi, as well as their major impact on adult longevity and fecundity, allows their further consideration for the development of insecticides in the fight against malaria mosquitoes.

Managing wastes as green resources: cigarette butt-synthesized pesticides are highly toxic to malaria vectors with little impact on predatory copepods

The development of novel mosquito control tools is a key prerequisite to build effective and reliable Integrated Vector Management strategies. Here, we proposed a novel method using cigarette butts for the synthesis of Ag nanostructures toxic to young instars of the malaria vector Anopheles stephensi, chloroquine (CQ)-resistant malaria parasites Plasmodium falciparum and microbial pathogens. The non-target impact of these nanomaterials in the aquatic environment was evaluated testing them at sub-lethal doses on the predatory copepod Mesocyclops aspericornis. Cigarette butt-synthesized Ag nanostructures were characterized by UV-vis and FTIR spectroscopy, as well as by EDX, SEM and XRD analyses. Low doses of cigarette butt extracts (with and without tobacco) showed larvicidal and pupicidal toxicity on An. stephensi. The LC₅₀ of cigarette butt-synthesized Ag nanostructures ranged from 4.505 ppm (I instar larvae) to 8.070 ppm (pupae) using smoked cigarette butts with tobacco, and from 3.571 (I instar larvae) to 6.143 ppm (pupae) using unsmoked cigarette butts without tobacco. Smoke toxicity experiments conducted against adults showed that unsmoked cigarette butts-based coils led to mortality comparable to permethrin-based positive control (84.2 and 91.2%, respectively). A single treatment with cigarette butts extracts and Ag nanostructures significantly reduced egg hatchability of An. stephensi. Furthermore, the antiplasmodial activity of cigarette butt extracts (with and without tobacco) and synthesized Ag nanostructures was evaluated against CQ-resistant (CQ-r) and CQ-sensitive (CQ-s) strains of P. falciparum. The lowest IC₅₀ values were achieved by cigarette butt extracts without tobacco, they were 54.63 μg/ml (CQ-s) and 63.26 μg/ml (CQ-r); while Ag nanostructure IC₅₀ values were 72.13 μg/ml (CQ-s) and 77.33 μg/ml (CQ-r). In MIC assays, low doses of the Ag nanostructures inhibited the growth of Bacillus subtilis, Klebsiella pneumoniae and Salmonella typhi. Finally, the predation efficiency of copepod M. aspericornis towards larvae of An. stephensi did not decrease in a nanoparticle-contaminated environment, if compared to control predation assays. Overall, the present research would suggest that an abundant hazardous waste, such as cigarette butts, can be turned to an important resource for nanosynthesis of highly effective antiplasmodials and insecticides.

Biophysical characterization of Acacia caesia-fabricated silver nanoparticles: effectiveness on mosquito vectors of public health relevance and impact on non-target aquatic biocontrol agents

Mosquito-borne diseases lead to serious public health concerns in tropical and sub-tropical countries worldwide, due to development of mosquito resistance to synthetic pesticides, non-target effects of pesticides, and socioeconomic reasons. Currently, green nanotechnology is a promising research field, showing a wide range of potential applications in vector control programs. The employ of natural products as reducing agents to fabricate insecticidal nanocomposites is gaining research attention worldwide, due to low costs and high effectiveness. Interestingly, biophysical features of green-synthesized nanoparticles strongly differ when different botanicals are employed for nanosynthesis. In this study, a cheap Acacia caesia leaf extract was employed to fabricate silver nanoparticles (Ag NPs) with ovicidal, larvicidal, and adulticidal toxicity against three mosquito vectors, Anopheles subpictus, Aedes albopictus, and Culex tritaeniorhynchus. Ag NPs were analyzed by various biophysical methods, including spectroscopy (UV-visible spectrophotometry, XRD, FTIR, EDX) and microscopy (SEM, TEM, AFM) techniques. High acute larvicidal potential was observed against larvae of An. subpictus (LC₅₀ = 10.33 μg/ml), Ae. albopictus (LC₅₀ = 11.32 μg/ml), and Cx. tritaeniorhynchus (LC₅₀ = 12.35 μg/ml). Ag NPs completely inhibited egg hatchability on three vectors at 60, 75, and 90 μg/ml, respectively. In adulticidal assays, LD₅₀ values were 18.66, 20.94, and 22.63 μg/ml. If compared to mosquito larvae, Ag NPs were safer to three non-target aquatic biocontrol agents, with LC₅₀ ranging from 684 to 2245 μg/ml. Overall, our study highlights the potential of A. caesia as an abundant and cheap bioresource to fabricate biogenic Ag NPs effective against mosquito young instars and adults, with moderate impact on non-target aquatic biocontrol agents.

Fabrication of highly effective mosquito nanolarvicides using an Asian plant of ethno-pharmacological interest, Priyangu (Aglaia elaeagnoidea): toxicity on non-target mosquito natural enemies

Mosquitoes threaten the lives of humans, livestock, pets and wildlife around the globe, due to their ability to vector devastating diseases. Aglaia elaeagnoidea, commonly known as Priyangu, is widely employed in Asian traditional medicine and pest control. Medicinal activities include anti-inflammatory, analgesic, anticancer, and anesthetic actions. Flavaglines, six cyclopenta[b]benzofurans, a cyclopenta[bc]benzopyran, a benzo[b]oxepine, and an aromatic butyrolactone showed antifungal properties, and aglaroxin A and rocaglamide were effective to control moth pests. Here, we determined the larvicidal action of A. elaeagnoidea leaf aqueous extract. Furthermore, we focused on Priyangu-mediated synthesis of Ag nanoparticles toxic to Culex quinquefasciatus, Aedes aegypti and Anopheles stephensi. The plant extract and the nanolarvicide were tested on three mosquito vectors, following the WHO protocol, as well as on three non-target mosquito predators. Priyangu-synthesized Ag nanoparticles were characterized by spectroscopic (UV, FTIR, XRD, and EDX) and microscopic (AFM, SEM, and TEM) analyses. Priyangu extract toxicity was moderate on Cx. quinquefasciatus (LC₅₀ 246.43; LC₉₀ 462.09 μg/mL), Ae. aegypti (LC₅₀ 229.79; LC₉₀ 442.71 μg/mL), and An. stephensi (LC₅₀ 207.06; LC₉₀ 408.46 μg/mL), respectively, while Priyangu-synthesized Ag nanoparticles were highly toxic to Cx. quinquefasciatus (LC₅₀ 24.91; LC₉₀ 45.96 μg/mL), Ae. aegypti (LC₅₀ 22.80; LC₉₀ 43.23 μg/mL), and An. stephensi (LC₅₀ 20.66; LC₉₀ 39.94 μg/mL), respectively. Priyangu extract and Ag nanoparticles were found safer to non-target larvivorous fishes, backswimmers, and waterbugs, with LC₅₀ ranging from 1247 to 37,254.45 μg/mL, if compared to target pests. Overall, the current research represents a modern approach integrating traditional botanical pesticides and nanotechnology to the control of larval populations of mosquito vectors, with negligible toxicity against non-target including larvivorous fishes, backswimmers, and waterbugs.

The desert wormwood (Artemisia herba-alba) - From Arabian folk medicine to a source of green and effective nanoinsecticides against mosquito vectors

The development of eco-friendly and effective insecticides is crucial for public health worldwide. Herein, we focused on the desert wormwood (Artemisia herba-alba), a plant widely used in Arabian traditional medicine, as a source of green nanoinsecticides against mosquito vectors, as well as growth inhibitors to be employed against microbial pathogens. Ag nanoparticles (AgNPs) fabricated with the A. herba-alba extract were tested on Indian and Saudi Arabian strains of Anopheles, Aedes and Culex mosquitoes. The chemical profile of the A. herba-alba extract was determined by LC-DAD-MS and ¹H NMR studies. Then, AgNPs were studied using UV-vis spectroscopy, XRD, FTIR spectroscopy, TEM, and EDX analyses. Artemisia herba-alba-synthesized AgNPs showed high larvicidal toxicity against mosquitoes from both Indian and Saudi Arabian strains. LC₅₀ of AgNPs against Indian strains was 9.76 μg/ml for An. stephensi, 10.70 μg/ml for Ae. aegypti and 11.43 μg/ml for Cx. quinquefasciatus, whereas against Saudi Arabian strains it was 33.58 μg/ml for Ae. aegypti and 38.06 μg/ml for Cx. pipiens. In adulticidal experiments, A. herba-alba extract showed LC₅₀ ranging from 293.02 to 450 μg/ml, while AgNP LC₅₀ ranged from 8.22 to 27.39 μg/ml. Further, low doses of the AgNPs inhibited the growth of selected microbial pathogens. Overall, A. herba-alba can be further considered as a source of phytochemicals, with special reference to saponins, for effective and prompt fabrication of AgNPs with relevant insecticidal and bactericidal activity against species of high public health importance.

Larvicidal Activity of Silver Nanoparticles Synthesized Using Extracts ofAmbrosia arborescens(Asteraceae) to ControlAedes aegyptiL. (Diptera: Culicidae)

The mosquito speciesAedes aegyptiis the primary vector of dengue, chikungunya, and Zika infections worldwide. Since effective vaccines or drugs are not available for the prevention and/or treatment of these pathologies, vector control has been adopted as the main approach to reduce their transmission. To controlAedespopulations, the most commonly used tool is the application of chemical insecticides and, despite their effectiveness, indiscriminate use of these chemicals has led to high operational costs, appearance of resistant populations, and adverse nontarget effects. Plant-derived insecticides may be an eco-friendly, cost-effective, and safe biocontrol alternative. The present study was carried out to evaluate the larvicidal activity of leaf extracts ofAmbrosia arborescensand green-synthesized silver nanoparticles (AgNPs) using aqueous extracts obtained from this plant against third instar larvae ofAe. aegypti. To test this, larvae were exposed for 24 h to the aqueous plant extract at 1500, 3000, 4500, and 6000 ppm and the plant-synthesized AgNPs at 0.2, 0.3, 0.4, and 0.5 ppm. In laboratory assays, AgNPs were more toxic (LC50 = 0.28 ppm; LC90 = 0.43 ppm) than the plant extract (LC50 = 1844.61 ppm; LC90 = 6043.95 ppm). These results suggest thatA. arborescensaqueous extract and green-synthesized silver nanoparticles produced from those extracts have the potential to be developed into suitable alternative tools useful for the control ofAe. aegyptipopulations.

Recent advances in use of silver nanoparticles as antimalarial agents

Malaria is one of the most common infectious diseases, which has become a great public health problem all over the world. Ineffectiveness of available antimalarial treatment is the main reason behind its menace. The failure of current treatment strategies is due to emergence of drug resistance in Plasmodium falciparum and drug toxicity in human beings. Therefore, the development of novel and effective antimalarial drugs is the need of the hour. Considering the huge biomedical applications of nanotechnology, it can be potentially used for the malarial treatment. Silver nanoparticles (AgNPs) have demonstrated significant activity against malarial parasite (P. falciparum) and vector (female Anopheles mosquito). It is believed that AgNPs will be a solution for the control of malaria. This review emphasizes the pros- and cons of existing antimalarial treatments and in depth discussion on application of AgNPs for treatment of malaria. The role of nanoparticles for site specific drug delivery and toxicological issues have also been discussed.

Ipomoea batatas (Convolvulaceae)-mediated synthesis of silver nanoparticles for controlling mosquito vectors of Aedes albopictus, Anopheles stephensi, and Culex quinquefasciatus (Diptera:Culicidae)

We proposed an effective and eco-friendly control of dengue, malaria, and filariasis-causing vectors. We tested Ipomoea batatas leaves-mediated silver nanoparticles (AgNPs) against first to fourth instar larvae and adults of Aedes albopictus, Anopheles stephensi, and Culex quinquefasciatus at different concentrations. The synthesized AgNPs showed broad spectrum of larvicidal and adulticidal effects after 48 h of exposure. The characterization of synthesized AgNPs was done using various spectral and microscopy analyses. The maximum efficacy was observed in synthesized AgNPs against the adult of Ae. albopictus with the LC₅₀ and LC₉₀ values were 10.069 and 15.657 μg/mL, respectively, followed by others.

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.

Acute toxicity and repellent activity of the Origanum scabrum Boiss. & Heldr. (Lamiaceae) essential oil against four mosquito vectors of public health importance and its biosafety on non-target aquatic organisms

The recent outbreaks of dengue, chikungunya, and Zika virus highlighted the pivotal importance of mosquito vector control in tropical and subtropical areas worldwide. However, mosquito control is facing hot challenges, mainly due to the rapid development of pesticide resistance in Culicidae and the limited success of biocontrol programs on Aedes mosquitoes. In this framework, screening botanicals for their mosquitocidal potential may offer effective and eco-friendly tools in the fight against mosquitoes. In the present study, the essential oil (EO) obtained from the medicinal plant Origanum scabrum was analyzed by GC-MS and evaluated for its mosquitocidal and repellent activities towards Anopheles stephensi, Aedes aegypti, Culex quinquefasciatus, and Culex tritaeniorhynchus. GC-MS analysis showed a total of 28 compounds, representing 97.1 % of the EO. The major constituents were carvacrol (48.2 %) and thymol (16.6 %). The EO was toxic effect to the A. stephensi, A. aegypti, C. quinquefasciatus, and C. tritaeniorhynchus larvae, with LC₅₀ of 61.65, 67.13, 72.45, and 78.87 μg/ml, respectively. Complete ovicidal activity was observed at 160, 200, 240, and 280 μg/ml, respectively. Against adult mosquitoes, LD₅₀ were 122.38, 134.39, 144.53, and 158.87 μg/ml, respectively. In repellency assays, the EOs tested at 1.0, 2.5, and 5.0 mg/cm² concentration of O. scabrum gave 100 % protection from mosquito bites up to 210, 180, 150, and 120 min, respectively. From an eco-toxicological point of view, the EO was tested on three non-target mosquito predators, Gambusia affinis, Diplonychus indicus, and Anisops bouvieri, with LC₅₀ ranging from 4162 to 12,425 μg/ml. Overall, the EO from O. scabrum may be considered as a low-cost and eco-friendly source of phytochemicals to develop novel repellents against Culicidae.