Toxicity on Dengue Mosquito Vectors Through Myristica fragrans-Synthesized Zinc Oxide Nanorods, and Their Cytotoxic Effects on Liver Cancer Cells (HepG2)

Optically active organic and inorganic nanomaterials for biological imaging applications: A review

Recent advancements in the field of nanotechnology have enabled targeted delivery of drug agents in vivo with minimal side effects. The use of nanoparticles for bio-imaging has revolutionized the field of nanomedicine by enabling non-invasive targeting and selective delivery of active drug moieties in vivo. Various inorganic nanomaterials like mesoporous silica nanoparticles, gold nanoparticles, magnetite nanoparticles graphene-based nanomaterials etc., have been created for multimodal therapies with varied multi-imaging modalities. These nanomaterials enable us to overcome the disadvantages of conventional imaging contrast agents (organic dyes) such as lack of stability in vitro and in vivo, high reactivity, low-quantum yield and poor photo stability. Inorganic nanomaterials can be easily fabricated, functionalised and modified as per requirements. Recently, advancements in synthesis techniques, such as the ability to generate molecules and construct supramolecular structures for specific functionalities, have boosted the usage of engineered nanomaterials. Their intrinsic physicochemical properties are unique and they possess excellent biocompatibility. Inorganic nanomaterial research has developed as the most actively booming research fields in biotechnology and biomedicine. Inorganic nanomaterials like gold nanoparticles, magnetic nanoparticles, mesoporous silica nanoparticles, graphene-based nanomaterials and quantum dots have shown excellent use in bioimaging, targeted drug delivery and cancer therapies. Biocompatibility of nanomaterials is an important aspect for the evolution of nanomaterials in the bench to bedside transition. The conduction of thorough and meticulous study for safety and efficacy in well-designed clinical trials is absolutely necessary to determine the functional and structural relationship between the engineered nanomaterial and its toxicity. In this article an attempt is made to throw some light on the current scenario and developments made in the field of nanomaterials in bioimaging.

Larvicidal and pupicidal activity of phyto-synthesized zinc oxide nanoparticles against dengue vector aedes aegypti

This study aimed to assess the phyto-synthesizing potential of Tarenna asiatica methanol leaf extract as well as its larvicidal and pupicidal potential against Aedes aegypti larvae. According to the findings of this study, the methanol leaf extract of T. asiatica has the potential to synthesize zinc oxide nanoparticles from zinc acetate dehydrate. Standard analytical techniques such as UV-visible spectrophotometer, Fourier-transform infrared spectroscopy, X-ray Diffraction analysis, Scanning Electron Microscope, and Energy Dispersive X-Ray were used to characterize the phyto-synthesized nanoparticles. The zinc oxide nanoparticles synthesized ranged in size from 22.35 to 31.27 nm and was spherical in shape. These nanoparticles demonstrated excellent larvicidal activity against Aedes aegypti larvae in the second, third, and fourth in stars, as well as significant pupicidal activity. These findings suggest that the methanol leaf extract of T. asiatica synthesized zinc oxide nanoparticles, which could be used to develop mosquito repellents.

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.

Swift synthesis of zinc oxide nanoparticles using unripe fruit extract of Pergularia daemia: An enhanced and eco-friendly control agent against Zika virus vector Aedes aegypti

In this study Pergularia daemia unripe fruits were used to synthesize zinc oxide nanoparticles (Pd-ZnONPs). UV-vis Spectroscopy detected the production of ZnONPs. XRD, FTIR, SEM, and TEM studies were used to characterize the synthesized Pd-ZnONPs. Aedes aegypti (Ae. aegypti) third instar larvae were analyzed to diverse concentrations of Pd-unripe fruit extract and Pd-ZnONPs for 24 hours to assess the larvicidal effect. Mortality was also detected in Ae. aegypti larvae under laboratory conditions, with corresponding LC₅₀ and LC₉₀ values of 11.11 and 21.20 µg/ml respectively. As a result of this study, the levels of total proteins, esterases, acetylcholine esterase, and phosphatase enzymes in the third instar larvae of Ae. aegypti were significantly lower than the control. These findings suggest that Pd-ZnONPs could be used to suppress mosquito larval populations.

Plant Extract-Based Synthesis of Metallic Nanomaterials, Their Applications, and Safety Concerns

Nanotechnology has attracted the attention of researchers from different scientific fields because of the escalated properties of nanomaterials compared with the properties of macromolecules. Nanomaterials can be prepared through different approaches involving physical and chemical methods. The development of nanomaterials through plant-based green chemistry approaches is more advantageous than other methods from the perspectives of environmental safety, animal, and human health. The biomolecules and metabolites of plants act as reducing and capping agents for the synthesis of metallic green nanomaterials. Plant-based synthesis is a preferred approach as it is not only cost-effective, easy, safe, clean, and eco-friendly but also provides pure nanomaterials in high yield. Since nanomaterials have antimicrobial and antioxidant potential, green nanomaterials synthesized from plants can be used for a variety of biomedical and environmental remediation applications. Past studies have focused mainly on the overall biogenic synthesis of individual or combinations of metallic nanomaterials and their oxides from different biological sources, including microorganisms and biomolecules. Moreover, from the viewpoint of biomedical applications, the literature is mainly focusing on synthetic nanomaterials. Herein, we discuss the extraction of green molecules and recent developments in the synthesis of different plant-based metallic nanomaterials, including silver, gold, platinum, palladium, copper, zinc, iron, and carbon. Apart from the biomedical applications of metallic nanomaterials, including antimicrobial, anticancer, diagnostic, drug delivery, tissue engineering, and regenerative medicine applications, their environmental remediation potential is also discussed. Furthermore, safety concerns and safety regulations pertaining to green nanomaterials are also discussed. This article is protected by copyright. All rights reserved.

Effect of green synthesized ZnO nanoparticles using Paspalum scrobiculatum grains extract in biological applications

In this report, ZnO nanoparticles were biosynthesized using Paspalum scrobiculatum grains extract for the first time. GC-MS analysis explicated that diethyl phthalate was the major phytocompound with 94.09% in aqueous extract. ZnO nanoparticles formation was confirmed by various physicochemical analyses. HR-TEM images showed the hexagonal, rectangular shaped nanoparticles in 15-30 nm size. The antioxidant, anti-inflammatory, and anti-diabetic analyses showed the effective bioactivity of ZnO nanoparticles in 80 μg/ml concentration with 95.36%, 94.08%, and 91.96%, respectively. The morphological and tissue changes witnessed in larvicidal and insecticidal activities against Culex tritaeniorhynchus and Tribolium castaneum revealed the efficient nature of ZnO nanoparticles in 100 ppm at 48 h and 100 μg/kg at 72 h, respectively. The morphological changes in antibacterial activity demonstrated the bactericidal nature of ZnO nanoparticles against Salmonella typhi and Staphylococcus aureus in 150 μg/ml concentration. The morphological observations in anticancer activity against HepG2 liver cancer cells showed the potent drug features of ZnO nanoparticles in 100 μg/ml concentration with 97.18% of cytotoxicity. The ZnO nanoparticles showed no toxicity against HDF normal cells in lower concentrations and it explicated the biocompatible features of nanoparticles. The Vigna radiata plant growth was efficiently promoted by low (60 ppm) concentration of nanoparticles. The ZnO nanoparticles divulged effective degradation of IPA, EDTA, BQ, and DPBF in 75%, 45%, 55%, and 80% through ROS formation, respectively. Thus, the synthesized ZnO nanoparticles are biocompatible and inexpensive material compared to the traditional one and can be utilized as an efficient material in biological fields.

Excito-repellency of Myristica fragrans Houtt. and Curcuma longa L. extracts from Southern Thailand against Aedes aegypti (L.)

The development of local plant extracts as a mosquito repellent is environmentally safe, inexpensive, and easily accessible for residents. In this study, three extracts from two local plants, Myristica fragrans Houtt. (flesh and mace) and Curcuma longa L. (rhizome) from southern Thailand, were investigated for their inherent repellent activity using the excito-repellency (ER) assay system against insectary-colonized Aedes aegypti (L.) (Diptera: Culicidae). The escape responses of mosquitoes exposed to concentrations of 0.5% to 5.0% (w/v) were measured to determine the contact irritant and non-contact repellent properties of each extract. Both the flesh and mace extracts of M. fragrans had relatively limited contact irritants (28.1% and 34.6% escape) and non-contact repellent (16.7% and 18.3% escape) activities against Ae. aegypti, respectively. The C. longa rhizome extract produced higher escape responses in the non-contact (42.6% escape) and contact (41.4% escape) trials at concentrations of 5.0% and 1.0%, respectively. GC-MS analysis found diethyl malate (56.5%) and elemicin (11.7%) to be the main components of the flesh and mace extracts, respectively, while ar-turmerone (24.6%), β-turmerone (15.2%), α-turmerone (10.5%) were the primary constituents of the rhizome extract. Overall, our results indicate that both M. fragrans extracts primarily caused Ae. aegypti escape through contact irritation. For C. longa, lower concentrations (0.5% and 1.0%) exhibited contact irritancy, but higher concentrations (2.5% and 5.0%) exhibited non-contact repellency against Ae. aegypti. Although they had limited efficacy, further experiments (e.g., mixing with other plant-based compounds) could enhance the ER of both local plant extracts. Additional evaluation of these extracts against other mosquito species and the ER of their chemical components, either alone or in combination, would also be beneficial for the development of green repellents. Our findings emphasize the possibility of utilizing plant-based mosquito repellent as an alternative personal protection method for future mosquito control programs.

Exploring the Journey of Zinc Oxide Nanoparticles (ZnO-NPs) toward Biomedical Applications

The field of nanotechnology is concerned with the creation and application of materials having a nanoscale spatial dimensioning. Having a considerable surface area to volume ratio, nanoparticles have particularly unique properties. Several chemical and physical strategies have been used to prepare zinc oxide nanoparticles (ZnO-NPs). Still, biological methods using green or natural routes in various underlying substances (e.g., plant extracts, enzymes, and microorganisms) can be more environmentally friendly and cost-effective than chemical and/or physical methods in the long run. ZnO-NPs are now being studied as antibacterial agents in nanoscale and microscale formulations. The purpose of this study is to analyze the prevalent traditional method of generating ZnO-NPs, as well as its harmful side effects, and how it might be addressed utilizing an eco-friendly green approach. The study's primary focus is on the potential biomedical applications of green synthesized ZnO-NPs. Biocompatibility and biomedical qualities have been improved in green-synthesized ZnO-NPs over their traditionally produced counterparts, making them excellent antibacterial and cancer-fighting drugs. Additionally, these ZnO-NPs are beneficial when combined with the healing processes of wounds and biosensing components to trace small portions of biomarkers linked with various disorders. It has also been discovered that ZnO-NPs can distribute and sense drugs. Green-synthesized ZnO-NPs are compared to traditionally synthesized ones in this review, which shows that they have outstanding potential as a potent biological agent, as well as related hazardous properties.

Effect of morphology on larvicidal activity of chemically synthesized zinc oxide nanoparticles against mosquito vectors

We report the larvicidal effects of four different morphologies of zinc oxide nanoparticles (ZnO NPs) [star-shaped (S), needle-like (N), plate-like (P) and cubical (C)] on larvae of Aedes albopictus and Anopheles vagus; the mosquitoes causing dengue fever and malaria, respectively. The nanoparticles were characterized by several analytical techniques, and their sizes and shapes were determined. Second instar larvae of the two types of mosquitoes were exposed to several concentrations of nanoparticles (25 mg L-1, 50 mg L-1, 75 mg L-1, 100 mg L-1) at 25 ± 2 °C and 84 ± 5% R.H, separately, for each morphology. Larval mortality was reported at 24 h intervals up to 21 days. The resulting LC50 for Aedes albopictus were, respectively, 38.90 mg L-1, 47.53 mg L-1, 68.38 mg L-1, 50.24 mg L-1 for S-, N-, P- and C-shaped nanoparticles. The LC50 of Anopheles vagus is lower (LC50 4.78 mg L-1, 6.51 mg L-1, 13.64 mg L-1, 10.47 mg L -1 ), respectively, for S-, N-, P- and C-shaped nanoparticles indicating that the nanoparticles are more toxic to Anopheles vagus larvae. The highest larvicidal effect was obtained from star-shaped nanoparticles [Aedes albopictus (38.90 mg L-1) on Anopheles vagus (4.78 mg L-1)], and the lowest was shown by the plate-like nanoparticles [Aedes albopictus (68.38 mg L-1), Anopheles vagus (13.64 mg L-1)]. The rate of development of surviving mosquito larvae was retarded when exposed to ZnO nanoparticles suggesting the possibility for these nanoparticles to kill and delay the growth of Aedes albopictus and Anopheles vagus larvae.

Zinc oxide nanoparticles: A comprehensive review on its synthesis, anticancer and drug delivery applications as well as health risks

In recent years, zinc oxide nanoparticles (ZnONPs) emerged as an excellent candidate in the field of optical, electrical, food packaging and particularly in biomedical research. ZnONPs show cancer cell specific toxicity via the pH-dependent (low pH) dissolution into Zn²⁺ ions, which generate reactive oxygen species and induce cytotoxicity in cancer cells. Further, ZnONPs have also been used as an effective carrier for the targeted delivery of several anticancer drugs into tumor cells. The increasing focus on ZnONPs resulted in the development of various synthesis approaches including chemical, pHysical, and green or biological for the manufacturing of ZnONPs. In this article, at first we have discussed the various synthesis methods of ZnONPs and secondly its biomedical applications. We have extensively reviewed the anticancer mechanism of ZnONPs on different types of cancers considering its size, shape and surface charge dependent cytotoxicity. Photoirradiation with UV light or NIR laser further increase its anticancer activity via synergistic chemo-photodynamic effect. The drug delivery applications of ZnONPs with special emphasis on drug loading mechanism, stimuli-responsive controlled release and therapeutic effects have also been discussed in this review. Finally, its side effects to vital body organs with mechanism via different exposure routes, the future direction of the ZnONPs research and application are also discussed.

Botanical insecticide-based nanosystems for the control of Aedes (Stegomyia) aegypti larvae

Aedes (Stegomyia) aegypti is a cosmopolitan species that transmits arbovirus of medical importance as dengue, Zika, and chikungunya. The main strategy employed for the control of this mosquito is the use of larvicidal agents. However, the overuse of synthetic chemical larvicides has led to an increase in resistant insects, making management difficult. Therefore, the use of botanical insecticide-based nanosystems as an alternative to the use of synthetic agents for the control of Ae. aegypti has gained more considerable attention in the last years, mainly due to the advantages of nanostructured delivery systems, such as (a) controlled release; (b) greater surface area; (c) improvement of biological activity; (d) protection of natural bioactive agents from the environment and thus achieving stability; and (e) lipophilic drugs are easier dispersed even in aqueous vehicles. This review summarizes the current knowledge about botanical insecticide-based nanosystems as larvicidal against Ae. aegypti larvae. The majority of papers used metallic nanoparticles (NPs) as larvicidal agents, mainly silver nanoparticles (AgNPs), showing potential for their use as an alternative, followed by nanoemulsions containing vegetable oils, most essential oils, nanosystems that allow the dispersion of this high hydrophobic product in water, the environment of larval development. The final section describes scientific findings about the mode of action of these NPs, showing the gap about this subject in literature.

Plant Natural Products for the Control of Aedes aegypti: The Main Vector of Important Arboviruses

The mosquito species Aedes aegypti is one of the main vectors of arboviruses, including dengue, Zika and chikungunya. Considering the deficiency or absence of vaccines to prevent these diseases, vector control remains an important strategy. The use of plant natural product-based insecticides constitutes an alternative to chemical insecticides as they are degraded more easily and are less harmful to the environment, not to mention their lower toxicity to non-target insects. This review details plant species and their secondary metabolites that have demonstrated insecticidal properties (ovicidal, larvicidal, pupicidal, adulticidal, repellent and ovipositional effects) against the mosquito, together with their mechanisms of action. In particular, essential oils and some of their chemical constituents such as terpenoids and phenylpropanoids offer distinct advantages. Thiophenes, amides and alkaloids also possess high larvicidal and adulticidal activities, adding to the wealth of plant natural products with potential in vector control applications.

Myristica fragrans bio-active ester functionalized ZnO nanoparticles exhibit antibacterial and antibiofilm activities in clinical isolates

We provide a novel one-step/one-pot bio-inspired method of synthesis for Myristica fragrans leaf ester (MFLE) capped‑zinc oxide nanoparticles (MFLE-ZnONPs). Antibacterial and antbiofilm efficacies of MFLE-ZnONPs were tested against the multi-drug resistant (MDR) Escherichia coli (E. coli-336), methicillin-resistant Staphylococcus aureus (MRSA-1) and methicillin-sensitive (MSSA-2) clinical isolates. Antibacterial screening using well diffusion assay revealed the cytotoxicity of MFLE-ZnONPs in the range of 500-2000 μg/ml. MFLE-ZnONPs significantly increased the zone of growth inhibition of E. coli-336 (17.0 ± 0.5 to 19.25 ± 1.0 mm), MSSA-2 (16.75 ± 0.8 to 19.0 ± 0.7 mm) and MRSA-1 (16.25 ± 1.0 to 18.25 ± 0.5 mm), respectively. The minimum inhibitory concentration (MIC) and minimum bactericidal concentrations (MBC) against E. coli-336, MRSA-1 and MSSA-2 were found to be 1500, 1000 and 500 μg/ml, and 2500, 2000 and 1500 μg/ml, respectively. A time and dose dependent reduction in the cell proliferation were also found at the respective MICs of tested strains. Scanning electron microscopy (SEM) of MFLE-ZnONPs-treated strains exhibited cellular damage via loss of native rod and coccoid shapes because of the formation of pits and cavities. E. coli-336 and MRSA-1 strains at their MICs (1500 and 1000 μg/ml) sharply reduced the biofilm production to 51% and 24%. The physico-chemical characterization via x-ray diffraction (XRD) ascertained the crystallinity and an average size of MFLE-ZnONPs as 48.32 ± 2.5 nm. Gas chromatography-mass spectroscopy (GC-MS) analysis of MFLE-ZnONPs unravelled the involvement of two bio-active esters (1) butyl 3-oxobut-2-yl ester and (2) α-monoolein) as surface capping/stabilizing agents. Fourier transform infrared (FTIR) analysis of MFLE and MFLE-ZnONPs showed the association of amines, alkanes, aldehydes, amides, carbonyl and amines functional groups in the corona formation. Overall, our data provide novel insights on the rapid development of eco-friendly, cost-effective bio-synthesis of MFLE-ZnONPs, showing their putative application as nano-antibiotics against MDR clinical isolates.

Phytosynthesized metal oxide nanoparticles for pharmaceutical applications

Developments in nanotechnology field, specifically, metal oxide nanoparticles have attracted the attention of researchers due to their unique sensing, electronic, drug delivery, catalysis, optoelectronics, cosmetics, and space applications. Physicochemical methods are used to fabricate nanosized metal oxides; however, drawbacks such as high cost and toxic chemical involvement prevail. Recent researches focus on synthesizing metal oxide nanoparticles through green chemistry which helps in avoiding the involvement of toxic chemicals in the synthesis process. Bacteria, fungi, and plants are the biological sources that are utilized for the green nanoparticle synthesis. Due to drawbacks such as tedious maintenance and the time needed for the nanoparticle formation, plant extracts are widely used in nanoparticle production. In addition, plants are available all over the world and phytosynthesized nanoparticles show comparatively less toxicity towards mammalian cells. Secondary metabolites including flavonoids, terpenoids, and saponins are present in plant extracts, and these are highly responsible for nanoparticle formation and reduction of toxicity. Hence, this article gives an overview of recent developments in the phytosynthesis of metal oxide nanoparticles and their toxic analysis in various cells and animal models. Also, their possible mechanism in normal and cancer cells, pharmaceutical applications, and their efficiency in disease treatment are also discussed.

Lagenaria siceraria - synthesised ZnO NPs - a valuable green route to control the malaria vector Anopheles stephensi

Malaria is a dangerous disease affecting humans and animals in tropical and subtropical areas worldwide. According to recent estimates, 3.2 billion people are at risk of malaria. Many drugs are in practices to control this disease and their vectors. Eco-friendly control tools are needed to fight vectors of this important disease. Nanotechnology is playing a key role in the fight against many public health emergencies. In the present study, Lagenaria siceraria aqueous peel extract was used to prepare zinc oxide nanoparticles (ZnO NPs), then tested on Anopheles stephensi eggs, larvae and pupae. The L. siceraria-synthesised ZnO NPs were characterized additionally by FTIR, AFM, XRD, UV-Vis spectroscopy, EDX, and SEM spectroscopy The ovicidal, larvicidal, pupicidal and repellent activities of L. siceraria and green-synthesised ZnO NPs were analysed on A. stephensi. The potential mechanism of action of ZnO NPs was studied investigating the changes in various enzyme activities in A. stephensi IV instar larvae. Furthermore, the smoke toxicity of L. siceraria-based cones against A. stephensi evoked higher mortality if compared with the control. Overall, the present study concluded that L. siceraria peel extract and its mediated green synthesised ZnO NPs represent a valuable green option to manage against malaria vectors.

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.

Greener synthesis of ZnO and Ag-ZnO nanoparticles using Silybum marianum for diverse biomedical applications

AIM

To investigate the physical and biological properties of Silybum marianum inspired ZnO nanoparticles (NPs), Ag-ZnO heterostructures. Experiment: Nanoparticles were characterized using ultraviolet-visible and infrared spectroscopy, x-ray diffraction, high resolution electron microscopy, ζ potential and thermo-gravimetric analysis etc. Results: Ag-ZnO-NPs indicated slightly higher antimicrobial potential then ZnO-NPs. Good antileishmanial (IC50 = 246 μg/ml for Ag-ZnO; 341 μg/ml for ZnO) and antioxidant potential while moderate enzyme inhibition is reported. 2, 2-Diphenyl 1-picrylhydrazyl radical scavenging of Ag-ZnO was higher relative to ZnO-NPs. Nanocosmaceutical formulation of nanoparticles indicated stable antimicrobial performance.

CONCLUSION

Biosynthesized nanoparticles indicated interesting biological properties and should be subjected to further research to establish their pharmacological relevance.

Evaluation of larvicidal, adulticidal, and anticholinesterase activities of essential oils of Illicium verum Hook. f., Pimenta dioica (L.) Merr., and Myristica fragrans Houtt. against Zika virus vectors

Aedes aegypti is the vector responsible for transmitting pathogens that cause various infectious diseases, such as dengue, Zika, yellow fever, and chikungunya, worrying health authorities in the tropics. Due to resistance of mosquitoes to synthetic insecticides, the search for more effective insecticidal agents becomes crucial. The aim of this study was to verify the larvicidal, adulticidal, and anticholinesterase activities of the essential oils of the Illicium verum (EOIV), Pimenta dioica (EOPD), and Myristica fragrans (EOMF) against Ae. aegypti. The essential oils (EOs) were obtained by hydrodistillation and analyzed by gas chromatography-mass spectrometry (GC-MS). The larvicidal and adulticidal activities of EOs were evaluated against third instar larvae and Ae. aegypti adult females, respectively, using the procedures of the World Health Organization (WHO) and the anticholinesterase activity of the EOs by the modified Ellman method. The following major components were identified: (E)-anethole (90.1%) for EOIV, methyl eugenol (55.0%) for EOPD, and sabinene (52.1%) for EOMF. All EOs exhibited larvicidal and adulticidal activity against Ae. aegypti. The highest larval mortality was observed in EOMF with LC₅₀ = 28.2 μg mL^-1. Adult mortality was observed after 1 (knockdown) and 24 h exposure, with the highest potential established by the EOIV, KC₅₀ = 7.3 μg mg female^-1 and LC₅₀ = 10.3 μg mg female^-1. EOIV (IC₅₀ = 4800 μg mL^-1), EOMF (IC₅₀ = 4510 μg mL^-1), and EOPD (IC₅₀ = 1320 μg mL^-1) inhibited AChE. EOMF (4130 μg mL^-1) and EOPD (IC₅₀ = 3340 μg mL^-1) inhibited BChE whereas EOIV showed no inhibition. The EOs were toxic to larvae and adults of Ae. aegypti, as well as being less toxic to humans than the currently used insecticides, opening the possibility of elaboration of a natural, safe, and ecological bioinsecticide for vector control.

Environmentally-Friendly Green Approach for the Production of Zinc Oxide Nanoparticles and Their Anti-Fungal, Ovicidal, and Larvicidal Properties

Green synthesis of nanoparticles can be an important alternative compared to conventional physio-chemical synthesis. We utilized Scadoxus multiflorus leaf powder aqueous extract as a capping and stabilizing agent for the synthesis of pure zinc oxide nanoparticles (ZnO NPs). Further, the synthesized ZnO NPs were subjected to various characterization techniques. Transmission electron microscope (TEM) analysis showed an irregular spherical shape, with an average particle size of 31 ± 2 nm. Furthermore, the synthesized ZnO NPs were tested against Aedes aegypti larvae and eggs, giving significant LC₅₀ value of 34.04 ppm. Ovicidal activity resulted in a higher percentage mortality rate of 96.4 ± 0.24 at 120 ppm with LC₅₀ value of 32.73 ppm. Anti-fungal studies were also conducted for ZnO NPs against Aspergillus niger and Aspergillus flavus, which demonstrated a higher inhibition rate for Aspergillus flavus compared to Aspergillus niger.

Mode of action of nanoparticles against insects

The employment of nanoparticles obtained through various synthesis routes as novel pesticides recently attracted high research attention. An impressive number of studies have been conducted to test their toxic potential against a wide number of arthropod pests and vectors, with major emphasis on mosquitoes and ticks. However, precise information on the mechanisms of action of nanoparticles against insects and mites are limited, with the noteworthy exception of silica, alumina, silver, and graphene oxide nanoparticles on insects, while no information is available for mites. Here, I summarize current knowledge about the mechanisms of action of nanoparticles against insects. Both silver and graphene oxide nanoparticles have a significant impact on insect antioxidant and detoxifying enzymes, leading to oxidative stress and cell death. Ag nanoparticles also reduced acetylcholinesterase activity, while polystyrene nanoparticles inhibited CYP450 isoenzymes. Au nanoparticles can act as trypsin inhibitors and disrupt development and reproduction. Metal nanoparticles can bind to S and P in proteins and nucleic acids, respectively, leading to a decrease in membrane permeability, therefore to organelle and enzyme denaturation, followed by cell death. Besides, Ag nanoparticles up- and downregulate key insect genes, reducing protein synthesis and gonadotrophin release, leading to developmental damages and reproductive failure. The toxicity of SiO₂ and Al₂O₃ nanoparticles is due to their binding to the insect cuticle, followed by physico-sorption of waxes and lipids, leading to insect dehydration. In the final section, insect nanotoxicology research trends are critically discussed, outlining major challenges to predict the ecotoxicological consequences arising from the real-world use of nanoparticles as pesticides.

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.

Iron and iron oxide nanoparticles are highly toxic to Culex quinquefasciatus with little non-target effects on larvivorous fishes

The control of filariasis vectors has been enhanced in several areas, but there are main challenges, including increasing resistance to insecticides and lack of cheap and eco-friendly products. The toxicity of iron (Fe⁰) and iron oxide (Fe₂O₃) nanoparticles has been scarcely investigated yet. We studied the larvicidal and pupicidal activity of Fe⁰ and Fe₂O₃ nanoparticles against Culex quinquefasciatus. Fe⁰ and Fe₂O₃ nanoparticles produced by green (using a Ficus natalensis aqueous extract) and chemical nanosynthesis, respectively, were analyzed by UV-Vis spectrophotometry, FT-IR spectroscopy, XRD analysis, SEM, and EDX assays. In larvicidal and pupicidal experiments on Cx. quinquefasciatus, LC₅₀ of Fe⁰ nanoparticles ranged from 20.9 (I instar larvae) to 43.7 ppm (pupae) and from 4.5 (I) to 22.1 ppm (pupae) for Fe₂O₃ nanoparticles synthesized chemically. Furthermore, the predation efficiency of the guppy fish, Poecilia reticulata, after a single treatment with sub-lethal doses of Fe⁰ and Fe₂O₃ nanoparticles was magnified. Overall, this work provides new insights about the toxicity of Fe⁰ and Fe₂O₃ nanoparticles against mosquito vectors; we suggested that green and chemical fabricated nano-iron may be considered to develop novel and effective pesticides.

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.