Larvicidal and pupicidal evaluation of silver nanoparticles synthesized using Aquilaria sinensis and Pogostemon cablin essential oils against dengue and zika viruses vector Aedes albopictus mosquito and its histopathological analysis

Advances in stabilization of metallic nanoparticle with biosurfactants- a review on current trends

Recently, research based on new biomaterials for stabilizing metallic nanoparticles has increased due to their greater environmental friendliness and lower health risk. Their stability is often a critical factor influencing their performance and shelf life. Nowadays, the use of biosurfactants is gaining interest due to their sustainable advantages. Biosurfactants are used for various commercial and industrial applications such as food processing, therapeutic applications, agriculture, etc. Biosurfactants create stable coatings surrounding nanoparticles to stop agglomeration and provide long-term stability. The present review study describes a collection of important scientific works on stabilization and capping of metallic nanoparticles as biosurfactants. This review also provides a comprehensive overview of the intrinsic properties and environmental aspects of metal nanoparticles coated with biosurfactants. In addition, future methods and potential solutions for biosurfactant-mediated stabilization in nanoparticle synthesis are also highlighted. The objective of this study is to ensure that the stabilized nanoparticles exhibit biocompatible properties, making them suitable for applications in medicine and biotechnology.

Applications of Green Synthesized Metal Nanoparticles - a Review

Green nanotechnology is an emerging field of science that focuses on the production of nanoparticles by living cells through biological pathways. This topic plays an extremely imperative responsibility in various fields, including pharmaceuticals, nuclear energy, fuel and energy, electronics, and bioengineering. Biological processes by green synthesis tools are more suitable to develop nanoparticles ranging from 1 to 100 nm compared to other related methods, owing to their safety, eco-friendliness, non-toxicity, and cost-effectiveness. In particular, the metal nanoparticles are synthesized by top-down and bottom-up approaches through various techniques like physical, chemical, and biological methods. Their characterization is very vital and the confirmation of nanoparticle traits is done by various instrumentation analyses such as UV-Vis spectrophotometry (UV-Vis), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscope (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), atomic force microscopy (AFM), annular dark-field imaging (HAADF), and intracranial pressure (ICP). In this review, we provide especially information on green synthesized metal nanoparticles, which are helpful to improve biomedical and environmental applications. In particular, the methods and conditions of plant-based synthesis, characterization techniques, and applications of green silver, gold, iron, selenium, and copper nanoparticles are overviewed.

Biosynthesized silver nanoparticles (Ag NPs) from isolated actinomycetes strains and their impact on the black cutworm, Agrotis ipsilon

Nanomaterials have been produced with the use of bio-nanotechnology, which is a low-cost approach. Currently, research is being conducted to determine whether actinomycetes isolated from Egyptian soil can biosynthesize Ag nanoparticles (Ag NPs) and characterized by using the following techniques: Transmission electron microscopy (TEM), Dynamic light scattering (DLS), Fourier transforms infrared (FT-IR), Energy-dispersive X-ray spectroscopy (EDX), UV-Vis spectroscopy and X-ray diffraction (XRD). The most promising actinomycetes isolate were identified, morphologically, biochemically, and molecularly. Streptomyces avermitilis Azhar A.4 was found to be able to reduce silver metal nanoparticles from silver nitrate in nine isolates collected from Egyptian soil. Toxicity of biosynthesized against 2nd and 4th larval instar of Agrotis ipsilon (Hufn.) (Lepidoptera: Noctuidae) was estimated. In addition, activity of certain vital antioxidant and detoxifying enzymes as well as midgut histology of treated larvae were also investigated. The results showed appositive correlations between larval mortality percentage (y) and bio-AgNPs concentrations (x) with excellent (R2). The 4th larval instar was more susceptible than 2nd larval instar with LC50 (with 95% confirmed limits) =8.61 (2.76-13.89) and 26.44(13.25-35.58) ppml-1, respectively of 5 days from treatment. The initial stages of biosynthesized AgNps exposure showed significant increases in carboxylesterase (CarE) and peroxidases (PODs) activity followed by significant suppression after 5 days pos-exposure. While protease activity was significantly decreased by increasing time post-exposure. Midgut histology showed abnormality and progressive damage by increasing time post exposure leading to complete destruction of midgut cells after 5 days from exposure. These results make biosynthesized AgNPs an appropriate alternative to chemical insecticide in A. ipsilon management.

Mosquito-Borne Diseases and Their Control Strategies: An Overview Focused on Green Synthesized Plant-Based Metallic Nanoparticles

Mosquitoes act as vectors of pathogens that cause most life-threatening diseases, such as malaria, Dengue, Chikungunya, Yellow fever, Zika, West Nile, Lymphatic filariasis, etc. To reduce the transmission of these mosquito-borne diseases in humans, several chemical, biological, mechanical, and pharmaceutical methods of control are used. However, these different strategies are facing important and timely challenges that include the rapid spread of highly invasive mosquitoes worldwide, the development of resistance in several mosquito species, and the recent outbreaks of novel arthropod-borne viruses (e.g., Dengue, Rift Valley fever, tick-borne encephalitis, West Nile, yellow fever, etc.). Therefore, the development of novel and effective methods of control is urgently needed to manage mosquito vectors. Adapting the principles of nanobiotechnology to mosquito vector control is one of the current approaches. As a single-step, eco-friendly, and biodegradable method that does not require the use of toxic chemicals, the green synthesis of nanoparticles using active toxic agents from plant extracts available since ancient times exhibits antagonistic responses and broad-spectrum target-specific activities against different species of vector mosquitoes. In this article, the current state of knowledge on the different mosquito control strategies in general, and on repellent and mosquitocidal plant-mediated synthesis of nanoparticles in particular, has been reviewed. By doing so, this review may open new doors for research on mosquito-borne diseases.

Biogenic Synthesis of Silver Nanoparticles Using Pantoea stewartii and Priestia aryabhattai and Their Antimicrobial, Larvicidal, Histopathological, and Biotoxicity Potential

In recent years, green nanotechnology has gained considerable importance for the synthesis of nanoparticles due to its economic viability and biosafety. In the current study, silver nanoparticles were synthesized using two bacterial isolates, H2 and H3, which were isolated from soil samples collected from the Western Ghats, Tamil Nadu, and identified at the species level as Pantoeastewartii (H2) and Priestiaaryabhattai (H3) by sequencing their 16s rRNA genes. Intracellularly synthesized silver nanoparticles were characterized by UV-visible spectroscopy, Fourier transform infrared spectroscopy, atomic force microscopy, and particle size analysis. AFM studies show that both of the bacterial synthesized Ag NPs were circular-shaped and disaggregated, with an average size distribution of 4 nm for Pantoeastewartii and 3.6 nm for Priestiaaryabhattai. Furthermore, their larvicidal activity, antimicrobial, histopathological, and biotoxicity effects were determined. The synthesized Ag NPs exhibited potent larvicidal activity against fourth instars of Ae.aegypti, An.stephensi, and Cx.quinquefasciatus exposed to a 50 µg/mL concentration for 24 h based on their LC₅₀ and LC₉₀ values. Histopathological studies of the affected mosquito larvae clearly show damage to the epithelial cells, food bolus, basement membrane, muscles, and midgut parts. The maximum antimicrobial activity of Priestiaaryabhattai-synthesized Ag NPs was observed for Streptomyces varsoviensis MTCC-1537, and that of Pantoea stewartii-synthesized Ag NPs was against Escherichia coli MTCC-43. The toxicity test on non-target organisms such as Artemia nauplii and zebrafish embryos indicates no visible abnormalities or mortality after their exposure for 48h. It is concluded that silver nanoparticles can easily be synthesized using Pantoea stewartii (H2) and Priestia aryabhattai (H3) as capping and reducing agents. Silver nanoparticles showed potent larvicidal activities and could potentially be used in integrated vector control programs because they are safe for other inhabitants of the same aquatic environment as mosquito larvae.

Plant and Microbial Approaches as Green Methods for the Synthesis of Nanomaterials: Synthesis, Applications, and Future Perspectives

The unique biological and physicochemical characteristics of biogenic (green-synthesized) nanomaterials (NMs) have attracted significant interest in different fields, with applications in the agrochemical, food, medication delivery, cosmetics, cellular imaging, and biomedical industries. To synthesize biogenic nanomaterials, green synthesis techniques use microorganisms, plant extracts, or proteins as bio-capping and bio-reducing agents and their role as bio-nanofactories for material synthesis at the nanoscale size. Green chemistry is environmentally benign, biocompatible, nontoxic, and economically effective. By taking into account the findings from recent investigations, we shed light on the most recent developments in the green synthesis of nanomaterials using different types of microbes and plants. Additionally, we cover different applications of green-synthesized nanomaterials in the food and textile industries, water treatment, and biomedical applications. Furthermore, we discuss the future perspectives of the green synthesis of nanomaterials to advance their production and applications.

Self-Therapeutic Nanomaterials: Applications in Biology and Medicine

Over past decades, nanotechnology has contributed to the biomedical field in areas including detection, diagnosis, and drug delivery via opto-electronic properties or enhancement of biological effects. Though generally considered inert delivery vehicles, a plethora of past and present evidence demonstrates that nanomaterials also exude unique intrinsic biological activity based on composition, shape, and surface functionalization. These intrinsic biological activities, termed self-therapeutic properties, take several forms, including mediation of cell-cell interactions, modulation of interactions between biomolecules, catalytic amplification of biochemical reactions, and alteration of biological signal transduction events. Moreover, study of biomolecule-nanomaterial interactions offers a promising avenue for uncovering the molecular mechanisms of biology and the evolution of disease. In this review, we observe the historical development, synthesis, and characterization of self-therapeutic nanomaterials. Next, we discuss nanomaterial interactions with biological systems, starting with administration and concluding with elimination. Finally, we apply this materials perspective to advances in intrinsic nanotherapies across the biomedical field, from cancer therapy to treatment of microbial infections and tissue regeneration. We conclude with a description of self-therapeutic nanomaterials in clinical trials and share our perspective on the direction of the field in upcoming years.

Morphological and physiological changes induced by Achyranthes aspera-mediated silver nanocomposites in Aedes aegypti larvae

Aedes aegypti is responsible for the global spread of several ailments such as chikungunya, dengue, yellow fever, and Zika. The use of synthetic chemicals is the primary intervention in mosquito management. However, their excessive utilization resulting in the spread of toxic ingredients in the environment and posing threats to beneficial organisms has prompted the recommendation for the use of biologically synthesized nanocomposites as a promising approach for vector control. Silver nanocomposites were synthesized using leaf (AL-AgNCs) and stem (AS-AgNCs) extracts of Achyranthes aspera. The early fourth instars of A. aegypti were exposed to lethal doses of these nanocomposites to evaluate their effects on larval development, behavior, morphology, and mid-gut histoarchitecture. The cellular damage and deposition of nanocomposite residues in the mid-gut were studied using light and transmission electron microscopy. The A. aspera silver nanocomposite (AA-AgNC)-exposed larvae exhibited dose-dependent extended duration of development and diminished adult emergence, but did not exhibit modified behavior. Intense damage to the cuticle membrane and slight contraction in the internal membrane of anal papillae were noticed. Morphologically, the mid-gut appeared disorganized, darkly pigmented, and shrunk. Histological investigations of the mid-gut revealed significantly disordered internal architecture with lysed cells, damaged peritrophic membrane and microvilli, disintegrated epithelial layer, and a ruptured and displaced basement membrane. Visualization of the larval mid-gut through TEM showed severe cellular damage and aggregation of black spots, indicating the deposition of silver particles released by AA-AgNCs. The investigations revealed the bio-efficacy of A. aspera-mediated AgNCs against A. aegypti inducing stomach and contact toxicity in the larvae. The utilization of AA-AgNCs is recommended for A. aegypti management as a safe and effective intervention.

Enhanced Antimicrobial, Cytotoxicity, Larvicidal, and Repellence Activities of Brown Algae, Cystoseira crinita-Mediated Green Synthesis of Magnesium Oxide Nanoparticles

Herein, the metabolites secreted by brown algae, Cystoseira crinita, were used as biocatalyst for green synthesis of magnesium oxide nanoparticles (MgO-NPs). The fabricated MgO-NPs were characterized using UV-vis spectroscopy, Fourier transforms infrared spectroscopy (FT-IR), Transmission Electron Microscopy (TEM), Scanning Electron Microscopy linked with energy-dispersive X-ray (SEM-EDX), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). Data showed successful formation of crystallographic and spherical MgO-NPs with sizes of 3–18 nm at a maximum surface plasmon resonance of 320 nm. Moreover, EDX analysis confirms the presence of Mg and O in the sample with weight percentages of 54.1% and 20.6%, respectively. Phyco-fabricated MgO-NPs showed promising activities against Gram-positive bacteria, Gram-negative bacteria, and Candida albicans with MIC values ranging between 12.5 and 50 μg mL⁻¹. The IC₅₀ value of MgO-NPs against cancer cell lines (Caco-2) was 113.4 μg mL⁻¹, whereas it was 141.2 μg mL⁻¹ for normal cell lines (Vero cell). Interestingly, the green synthesized MgO-NPs exhibited significant larvicidal and pupicidal activity against Musca domestica. At 10 μg mL⁻¹ MgO-NPs, the highest mortality percentages were 99.0%, 95.0%, 92.2%, and 81.0% for I, II, III instars’ larvae, and pupa of M. domestica, respectively, with LC₅₀ values (3.08, 3.49, and 4.46 μg mL⁻¹), and LC₉₀ values (7.46, 8.89, and 10.43 μg mL⁻¹), respectively. Also, MgO-NPs showed repellence activity for adults of M. domestica at 10 μg mL⁻¹ with 63.0%, 77.9%, 84.9%, and 96.8% after 12, 24, 48, and 72 h, respectively.

Fabrication and characterization of noble crystalline silver nanoparticles from Pimenta dioica leave extract and analysis of chemical constituents for larvicidal applications

The current works report the bio-efficacy of Pimenta dioica leaf derived silver nanoparticles (Pd@AgNPs) and leaf extract obtained trough different solvents against the larvae of malaria, filarial and dengue vectors. Synthesis of silver nanoparticles (AgNPs) was done by adding 10 ml of P. dioica leaf extract into 90 ml of 1 mM silver nitrate solution, a slow colour change was observed depicting the formation of AgNPs. Further, Pd@AgNPs was confirmed through Ultraviolet–visible spectroscopy which exhibited characteristic absorption peak at 422 nm wavelength. X-ray diffraction and selected area electron diffraction analysis confirmed monodispersed and crystalline nature of Pd@AgNPs with 32 nm an average size. Scanning electron microscopy and transmission electron microscopy showed the most of Pd@AgNPs were spherical and triangular in shape and energy-dispersive X-ray spectroscopy revealed silver elemental nature of nanoparticles. Zeta potential of Pd@AgNPs is highly negative which confirmed its stable nature. Pd@AgNPs showed prominent absorption peaks at 1015, 1047, 1243, 1634, 2347, 2373, 2697 and 3840 cm⁻¹ which are corresponding to following compounds polysaccharides, carboxylic acids, water, alcohols, esters, ethers, amines, amides and phenol, respectively as reported by Fourier-transform infrared spectroscopy analysis. Gas chromatography–mass spectrometry and Liquid chromatography–mass spectrometry analysis revealed 39 and 70 compounds, respectively, which might be contributed for bio-reduction, capping, stabilization and larvicidal behavior of AgNPs. A comparable lethality (LC₅₀ and LC₉₀) was observed in case of Pd@AgNPs over leaf extract alone. The potential larvicidal activity of Pd@AgNPs was observed against the larvae of Aedes aegypti,(LC_50, 2.605; LC_90, 5.084 ppm) Anopheles stephensi (LC_50, 3.269; LC_90, 7.790 ppm) and Culex quinquefasciatus (LC_50, 5.373; LC_90, 14.738 ppm without affecting non-targeted organism, Mesocyclops thermocyclopoides after 72 hr of exposure. This study entails green chemistry behind synthesis of AgNPs which offers effective technique for mosquito control and other therapeutic applications.

B. Ovicidal, larvicidal and pupicidal efficacy of silver nanoparticles synthesized by Bacillus marisflavi against the chosen mosquito species

Microbial synthesis of silver nanoparticles is more advantageous and is eco-friendly to combat the various vectors that cause diseases in humans. Hence, in the present study a Bacillus strain is isolated from marine habitat and is evaluated for its ability to synthesize silver nanoparticles (AgNPs) and its efficacy evaluated against the immature stages of selected mosquito species. The effective candidate was confirmed to be Bacillus marisflavi after 16S rRNA sequencing. The synthesis of AgNPs was confirmed by UV-Vis spectrophotometer. Atomic Force Microscopic (AFM) analysis showed spherical nanoparticles. Size analysis using Scanning Electron Microscope (SEM) showed particles of nano size averaging 78.77 nm. The diameter of the particles analyzed by Dynamic Light Scattering (DLS) showed 101.6 nm with a poly-dispersive index of 0.3. Finally the elemental nature of the nanoparticles was identified by Fourier-transform infrared spectroscopy (FTIR). LC50 and LC90 values for the ovicidal, larvicidal and pupicidal efficacy of the AgNPs against the egg, larvae and pupae of Aedes aegypti, Culex quinquefasciatus and Anopheles stephensi respectively were evaluated. The present study revealed that the nanoparticles have an excellent toxic effect against the disease transmitting vector mosquitoes. Hence, the rapid synthesis of AgNPs would be an appropriate eco-friendly tool for biocontrol of vector mosquitoes.

Silver Nanoparticles as Potential Antiviral Agents

Since the early 1990s, nanotechnology has led to new horizons in nanomedicine, which encompasses all spheres of science including chemistry, material science, biology, and biotechnology. Emerging viral infections are creating severe hazards to public health worldwide, recently, COVID-19 has caused mass human casualties with significant economic impacts. Interestingly, silver nanoparticles (AgNPs) exhibited the potential to destroy viruses, bacteria, and fungi using various methods. However, developing safe and effective antiviral drugs is challenging, as viruses use host cells for replication. Designing drugs that do not harm host cells while targeting viruses is complicated. In recent years, the impact of AgNPs on viruses has been evaluated. Here, we discuss the potential role of silver nanoparticles as antiviral agents. In this review, we focus on the properties of AgNPs such as their characterization methods, antiviral activity, mechanisms, applications, and toxicity.

Nanotechnology Applications of Flavonoids for Viral Diseases

Recent years have witnessed the emergence of several viral diseases, including various zoonotic diseases such as the current pandemic caused by the Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2). Other viruses, which possess pandemic-causing potential include avian flu, Ebola, dengue, Zika, and Nipah virus, as well as the re-emergence of SARS (Severe Acute Respiratory Syndrome) and MERS (Middle East Respiratory Syndrome) coronaviruses. Notably, effective drugs or vaccines against these viruses are still to be discovered. All the newly approved vaccines against the SARS-CoV-2-induced disease COVID-19 possess real-time possibility of becoming obsolete because of the development of ‘variants of concern’. Flavonoids are being increasingly recognized as prophylactic and therapeutic agents against emerging and old viral diseases. Around 10,000 natural flavonoid compounds have been identified, being phytochemicals, all plant-based. Flavonoids have been reported to have lesser side effects than conventional anti-viral agents and are effective against more viral diseases than currently used anti-virals. Despite their abundance in plants, which are a part of human diet, flavonoids have the problem of low bioavailability. Various attempts are in progress to increase the bioavailability of flavonoids, one of the promising fields being nanotechnology. This review is a narrative of some anti-viral dietary flavonoids, their bioavailability, and various means with an emphasis on the nanotechnology system(s) being experimented with to deliver anti-viral flavonoids, whose systems show potential in the efficient delivery of flavonoids, resulting in increased bioavailability.

Green synthesized plant-based silver nanoparticles: therapeutic prospective for anticancer and antiviral activity

Nanotechnology holds an emerging domain of medical science as it can be utilized virtually in all areas. Phyto-constituents are valuable and encouraging candidates for synthesizing green silver nanoparticles (AgNPs) which possess great potentials toward chronic diseases. This review gives an overview of the Green approach of AgNPs synthesis and its characterization. The present review further explores the potentials of Phyto-based AgNPs toward anticancer and antiviral activity including its probable mechanism of action. Green synthesized AgNPs prepared by numerous medicinal plants extract are critically reviewed for cancer and viral infection. Thus, this article mainly highlights green synthesized Phyto-based AgNPs with their potential applications for cancer and viral infection including mechanism of action and therapeutic future prospective in a single window.

Toxicity of Essential Oils Nanoemulsion Against Aphis Craccivora and Their Inhibitory Activity on Insect Enzymes

Essential oils are widely used as botanical insecticides rather than chemically synthesized pesticides which led to catastrophic effects on humans, the environment, and eutrophication. Here, encapsulation of four essential oils Basilicum ocimum, Cuminum cyminum, Origanum marjorana, and Matricaria chamomilla were utilized in the presence of 3% v/v ethanol, as anti-insect against Aphis craccivora and compared to traditional insecticides dinotefuran and pymetrozine. Different tools were used to characterize the prepared nanoemulsion such as TEM, SEM, and Zeta potential analyzer. Besides, selected B. ocimum and C. cyminum were analyzed by gas chromatography-mass GC/mass spectrometry. The results reveal that nanoemulsion exhibited considerable toxic activities against laboratory and field strains of cowpea aphid. In the toxicity bioassay test of essential oils, moderate mortality was observed at 10,000 mg/L against aphid with lethal concentration that kills 50% of insects (LC50) values of basil 992 mg/L and marjoram 3162 mg/L. Else, nanoemulsion provided the highest mortality rate at 625 mg/L and the LC50 values of basil nanoemulsion (NE) 45 mg/L, and marjoram NE 188 mg/L in laboratory strains. The systemic effects of the tested substances acetylcholine esterase, alkaline phosphatase, β-esterases, glutathione S-transferase (GST), and mixed-function oxidase (MFO) enzymes on insects were found to be significantly decreased and increased when compared with control groups. Overall, these results highlight that the nanoemulsion is potential tools to control cowpea aphid and could be useful in developing integrated insect management in faba bean fields.

Insecticidal efficacy and mechanism of nanoparticles synthesized from chitosan and carboxymethyl chitosan against Solenopsis invicta (Hymenoptera: Formicidae)

The efficacy and mode of action of biodegradable chitosan (CS) and carboxymethyl chitosan (CMCS) organic polymer nanoparticles (NPs) on insects were studied. The prepared CS/CMCS-NPs were spherical with a particle size of 142.1 ± 2.0 nm. The swelling test showed that they were pH-sensitive, and the swelling rate was 554 % at pH 4.5. It was found that CS/CMCS-NPs had insecticidal efficacy against red fire ants (S. invicta). The mortality of red fire ants on the 6th day after treatment with 0.2 % and 0.06 % CS/CMCS-NPs suspensions was 98.33 ± 1.67 % and 48.33 ± 3.33 %, respectively. After CS/CMCS-NPs treatment, the food intake, growth, and development of red fire ants were inhibited; the midgut was significantly expanded; and the activity of digestive enzymes in the midgut was decreased. Our findings suggest that CS/CMCS-NPs mainly inhibited the digestion function of the midgut, leading to the death of red fire ants.

Metal oxide nanoparticle synthesis (ZnO-NPs) of Knoxia sumatrensis (Retz.) DC. Aqueous leaf extract and It's evaluation of their antioxidant, anti-proliferative and larvicidal activities

In around the world, mosquito control is considered a most important because of the incapable of synthetic insecticides and the ecological pollution about by them. In this manner, need the eco-friendly insecticides to efficient control the mosquito disease is the need of the hour. We synthesized the eco-friendly of zinc oxide nanoparticles (ZnO-NPs) using the Knoxia sumatrensis aqueous leaf extract (Ks-ALE) as a reducing and stabilizing agent. The synthesis of ZnO-NPs was confirmed by UV with an absorption peak at 354 nm. ZnO-NPs crystal structure was analyzed by X-ray diffraction (XRD). Fourier transform infrared spectroscopy (FT-IR) spectra revealed the chloride, cyclic alcohols, sulfonamies, carboxylic acids, oximes, phosphines, alkenes and alcohol & phenol. Field emission-scanning electron microscopy (FE-SEM) showed that the NP's are rod shaped with 50-80 nm size and also energy dispersive spectra (EDaX) spectra showed presence of zinc. Antioxidant assay showed superior activity and evidenced by DPPH, ABTS and H2O2 radical assays. Furthermore, the ZnO-NPs exhibited strong activity in MCF-7 cell line with IC50 value is 58.87 μg/mL. Mosquito larvicidal activity of ZnO-NPs produced significant activity and excellent larvicidal activity was noticed in Cx. quinquefasciatus with LC50 0.08, mg/mL and LC9019.46 mg/mL. This study suggests that synthesized ZnO-NPs using Knoxia sumatrensis leaf extract have good biological activities and it makes them an ideal candidate for pharmacological studies.

Biocontrol of mosquito vectors through herbal-derived silver nanoparticles: prospects and challenges

Mosquitoes spread several life-threatening diseases such as malaria, filaria, dengue, Japanese encephalitis, West Nile fever, chikungunya, and yellow fever and are associated with millions of deaths every year across the world. However, insecticides of synthetic origin are conventionally used for controlling various vector-borne diseases but they have various associated drawbacks like impact on non-targeted species, negative effects on the environment, and development of resistance in vector species by alteration of the target site. Plant extracts, phytochemicals, and their nanoformulations can serve as ovipositional attractants, insect growth regulators, larvicides, and repellents with least effects on the environment. Such plant-derived products exhibit broad-spectrum resistance against various mosquito species and are relatively cheaper, environmentally safer, biodegradable, easily accessible, and are non-toxic to non-targeted organisms. Therefore, in this review article, the current knowledge of phytochemical sources exhibiting larvicidal activity and their variations in response to solvents used for their extraction is underlined. Also, different methods such as physical, chemical, and biological for silver nanoparticle (AgNPs) synthesis, their mechanism of synthesis using plant extract, their potent larvicidal activity, and the possible mechanism by which these particles kill mosquito larvae are discussed. In addition, constraints related to commercialization of nanoherbal products at government and academic or research level and barriers from laboratory experiments to field trial have also been discussed. This comprehensive information can be gainfully employed for the development of herbal larvicidal formulations and nanopesticides against insecticide-resistant vector species in the near future. Graphical abstract.

Plant-based larvicidal agents: An overview from 2000 to 2018

Current review aims to systematically segregate, analyze and arrange the key findings of the scientific reports published on larvicidal plants including larvicidal formulations. The investigation was carried out by analyzing the published literature in various scientific databases, subsequently, the key findings of the selective scientific reports having larvicidal potency (LC₅₀) of extract or isolated oil<100 μg/mL were tabulated to provide the concise and crucial information. Special emphasis was given on reports in which LC₅₀ of extract or isolated oil was reported to be < 10 μg/mL, genus or species documented in multiple independent studies, advancement in larvicidal formulations and activity of isolated phytoconstituents. Extensive analysis of published literature revealed that the larvicidal potency of herbal resources varied from sub-microgram/ml to practically insignificant. Overall, this unprecedented summarized and arranged information can be utilized for design, development and optimization of herbal based formulation having potential larvicidal activity.

Larvicidal Activity of Synthesized Silver Nanoparticles from Curcuma zedoaria Essential Oil against Culex quinquefasciatus

Culex quinquefasciatus is the major vector of the bancroftian filarial parasite which causes human lymphatic filariasis and St. Louis encephalitis. The simple way to stop the transmission is to control the vector by using synthetic chemicals. However, herbal essential oils have biological properties, such as a larvicidal effect and are ecofriendly to use. In this study, we investigated the larvicidal activity of Curcuma zedoaria essential oil (ZEO) and biosynthesized silver nanoparticles using this essential oil (ZEO-AgNPs). The larvicidal activity against both insecticide-susceptible and -resistant strains of Cx. quinquefasciatus larvae of ZEO were investigated and compared with ZEO-AgNPs. The ZEO-AgNPs showed the utmost toxicity against both strains of Cx. quinquefasciatus. After 24 h of exposure, LC₅₀ and LC₉₉ of ZEO against susceptible strain were 36.32 and 85.11 ppm, respectively. While LC₅₀ and LC₉₉ of ZEO against the resistant strain were 37.29 and 76.79 ppm, respectively. Whereas ZEO-AgNPs offered complete larval mortality within 24 h of exposure, LC₅₀ and LC₉₉ of ZEO-AgNPs against the susceptible strain, were 0.57 and 8.54 ppm, respectively. For the resistant strain, LC₅₀ and LC₉₉ values were 0.64 and 8.88 ppm, respectively. The potency in killing Cx. quinquefasciatus and stability of ZEO-AgNPs have made this product a good candidate for the development of novel natural larvicides.