One-Pot Fabrication of Silver Nanocrystals Using Nicandra Physalodes:A Novel Route for Mosquito Vector Control with Moderate Toxicity on Non-Target Water Bugs
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Research in Veterinary Science 107 (2016) 95–101 Contents lists available at ScienceDirect Research in Veterinary Science journal homepage: www.elsevier.com/locate/rvsc One-pot fabrication of silver nanocrystals using Nicandra physalodes:A novel route for mosquito vector control with moderate toxicity on non-target water bugs Marimuthu Govindarajan a,⁎, Hanem F. Khater b,ChellasamyPanneerselvamc,GiovanniBenellid,⁎ a Unit of Vector Control, Phytochemistry and Nanotechnology, Department of Zoology, Annamalai University, Annamalainagar, 608 002, Tamil Nadu, India b Department of Parasitology, Faculty of Veterinary Medicine, Benha University, Moshtohor, Toukh, 13736, Egypt c Department of Biology, Faculty of Science, University of Tabuk, Tabuk 71491, Saudi Arabia d Insect Behaviour Group, Department of Agriculture, Food and Environment, University of Pisa, via del Borghetto 80, 56124 Pisa, Italy article info abstract Article history: Mosquitoes (Diptera: Culicidae) as vectors for important diseases and parasites causing millions of deaths every Received 12 December 2015 year. The use of synthetic pesticides against Culicidae leads to resistance and environmental concerns. Therefore, Received in revised form 12 May 2016 eco-friendly control tools are a priority. In this research, Nicandra physalodes-mediated synthesis of silver nano- Accepted 30 May 2016 particles (Ag NPs) was conducted, in order to control larval populations of three important mosquito vectors, Anopheles stephensi, Aedes aegypti and Culex quinquefasciatus. Biofabricated Ag NPs were characterized using Keywords: UV–vis spectrophotometry, XRD, FTIR spectroscopy, SEM, and TEM analyses. Ag NPs were highly toxic against Biosafety fi μ Dengue the three mosquito vectors. Maximum ef cacy was detected against A. stephensi (LC50 = 12.39 g/mL), followed μ μ Filariasis by Ae. aegypti (LC50 = 13.61 g/mL) and Cx. quinquefasciatus (LC50 = 14.79 g/mL). Interestingly, Ag NPs were Malaria safer for the non-target aquatic organism Diplonychus indicus sharing the same aquatic habitats of mosquito lar- Green-synthesis vae. LC50 and LC90 values were 1032.81 and 19,076.59 μg/mL, respectively. Overall, our results highlight that N. Zika virus physalodes-fabricated Ag NPs are a promising for development of eco-friendly larvicides against mosquito vec- tors, with negligible toxicity against non-target aquatic water bugs. © 2016 Elsevier Ltd. All rights reserved. 1. Introduction al., 2016c). In particular, silver nanoparticles can be used for purification of drinking water, degradation of pesticides, to kill human pathogenic Mosquitoes (Diptera: Culicidae) are responsible for transmission of bacteria, as well as novel mosquitocides and antiplasmodial drugs some serious and dreadful pathogens and parasites in tropical and sub- (Kathiresan et al., 2009; Benelli and Mehlhorn, 2016). tropical countries worldwide, including malaria, avian malaria, yellow Recently, a growing number of plants have been successfully used fever, Rift valley fever, dengue, West Nile virus, Zika virus, Japanese en- for efficient and rapid extracellular synthesis of silver, copper and gold cephalitis, Western equine encephalomyelitis, bancroftian and brugian nanoparticles (Govindarajan, 2016). Good examples include cheap ex- filariae, canine heartworm disease (Dirofilaria immitis) and setariosis tracts of neem, Azadirachta indica (Shankar et al., 2004; Murugan et (Setaria spp.) (Benelli and Mehlhorn, 2016; Benelli et al., 2016; al., 2016), Chomelia asiatica (Muthukumaran et al., 2015a), Sida acuta Govindarajan and Benelli, 2016a; Govindarajan et al., 2016a). The use (Veerekumar et al., 2013), Gmelina asiatica (Muthukumaran et al., of synthetic insecticides to control mosquito vectors lead to resistance, 2015b), Barleria cristata (Govindarajan and Benelli, 2016b), Bauhinia adverse environmental effects and high operational costs. Therefore, variegata (Govindarajan et al., 2016d)andClerodendrum chinense eco-friendly control tools are urgently needed (Benelli, 2015a, 2015b; (Govindarajan et al., 2016e). Nanoparticles possess peculiar toxicity Govindarajan et al., 2016b). In recent years, the green processes for mechanisms due to surface modification (Oberdorster et al., 2005), the synthesis of silver nanoparticles evolved into an important branch and this may actively contribute to their excellent mosquitocidal poten- of nanotechnology, due to low cost, simple procedures and absence of tial against Culicidae larvae (Saxena et al., 2010; Benelli, 2016; toxic chemicals or high energy inputs (Benelli, 2016; Govindarajan et Govindarajan et al., 2016f ). However, despite the increasing number of evidences of plant-synthesized mosquitocidal nanoparticles, only moderate efforts have been carried out to shed light on the nanoparticle biotoxicity on non-target organisms sharing the same ecological niche ⁎ Corresponding authors. E-mail addresses: [email protected] (M. Govindarajan), [email protected], of mosquito young instars (see Benelli, 2016; Veerakumar and [email protected] (G. Benelli). Govindarajan, 2014). http://dx.doi.org/10.1016/j.rvsc.2016.05.017 0034-5288/© 2016 Elsevier Ltd. All rights reserved. 96 M. Govindarajan et al. / Research in Veterinary Science 107 (2016) 95–101 Fig. 1. (a) Nicandra physalodes (L.) Gaertn. (Solanaceae). (b) Color intensity of Nicandra physalodes aqueous extract before and after the reduction of silver nitrate (1 mM). The color change indicates Ag+ reduction to elemental nanosilver. (c) UV-visible spectrum of silver nanoparticles after 120 min from the reaction. Nicandra physalodes (L.) Gaertn. (Solanaceae) is commonly known 2.2. Preparation of plant leaf extract as “shooflyplant”, while the tamil name is “sudakku thakkali”. N. physalodes is an erect herb, with light blue or light purple flowers (Fig. The leaves of N. physalodes were dried in the shade and ground to 1a). In Tibetan medicine, this plant is used for the treatment of diuresis, fine powder in an electric grinder. Aqueous extract was prepared by mydriasis, analgesia, antibacterial and inflammation (Chopra et al., mixing 50 g of dried leaf powder with 500 mL of water (boiled and 1986). Several compounds (i.e. nicaphysalins) have been isolated from cooled distilled water) with constant stirring on a magnetic stirrer. the plant (Kirson et al., 1972), and it has also been confirmed that this The suspension of dried leaf powder in water was left for 3 h and filtered species has insecticidal properties (Olga et al., 1964). However, its through Whatman n. 1 filter paper and the filtrate was stored in an mosquitocidal potential is currently unknown. amber-colored airtight bottle at 10 °C temperature until testing In this research, we reported a method to fabricate silver nanoparti- (Govindarajan et al., 2016b). cles (Ag NPs) using the aqueous leaf extract of the N. physalodes, a cheap and eco-friendly material acting as reducing and stabilizing agent. Ag NPs were characterized by UV–vis spectrophotometry, X-ray diffraction 2.3. Synthesis of silver nanoparticles (XRD), Fourier transform infrared spectroscopy (FTIR), scanning elec- tron microscopy (SEM) and transmission electron microscopy (TEM). The aqueous extract of fresh leaves was prepared by taking 10 g of The aqueous extract of N. physalodes and the green-synthesized Ag thoroughly washed and finely cut leaves in a 300-mL Erlenmeyer flask NPs were tested for their larvicidal potential against the malaria vector along with 100 mL of sterilized double-distilled water and then boiling Anopheles stephensi, the dengue vector Aedes aegypti and the filariasis the mixture for 5 min before finally decanting it. The extract was filtered vector Culex quinquefasciatus. Furthermore, we evaluated the biotoxicity with Whatman filter paper n. 1, stored at −15 °C and tested within a of N. physalodes aqueous extract and green-synthesized Ag NPs on the week. The filtrate was treated with aqueous 1 mM AgNO3 (21.2 mg of non-target aquatic water bug Diplonychus indicus, which shares the AgNO3 in 125 mL of Milli-Q water) solution in an Erlenmeyer flask same ecological niche of Anopheles, Aedes and Culex mosquito in South and incubated at room temperature. Eighty-eight milliliters of an aque- India. ous solution of 1 mM silver nitrate was reduced using 12 mL of leaf ex- tract at room temperature for 10 min, resulting in a brown–yellow solution indicating the formation of Ag NPs (Govindarajan et al., 2016c). 2. Materials and methods 2.1. Materials 2.4. Characterization of silver nanoparticles Silver nitrate was purchased from Merck, India. The glassware was The bioreduction of Ag+ ions was monitored using UV–vis spectro- acid-washed thoroughly and then rinsed with Millipore Milli-Q water. photometry (UV-160v, Shimadzu, Japan). Analysis of size, morphology Healthy and fresh leaves of N. physalodes (Fig. 1) were collected from and composition of Ag NPs were performed by scanning electron mi- Nilgiris, Western Ghats (11° 10′ Nto11°45′ N latitude and 76° 14’Eto croscopy (Hitachi S3000 H SEM), and transmission electron microscopy 77° 2′ E longitude), Tamil Nadu State, India. The identity was confirmed (TEM Technite 10 Philips). The purified Ag NPs were examined for the at the Department of Botany, Annamalai University, Annamalai Nagar, presence of biomolecules using FTIR spectrum (Thermo ScientificNico- Tamil Nadu. Voucher specimens were numbered and kept in our labora- let 380 FT-IR Spectrometer) KBr pellets and crystalline Ag NPs were de- tory and are available upon request (ID: AUDZ-400). termined by XRD analysis