To the Editor

Keywords: Toxicity; Silver nanparticles; Enivornmental and health hazards; Antibacterial. Silver nanoparticles (AgNP) have been extensively used for packaging and storage of food products to enhance their shelf life [1]. Likewise, AgNP are increasingly used in various fields of pharmaceutical and biomedical sciences [2]. In addition, AgNP are good antibacterial and antiviral agents [3], and also used in the treatment of infection in burns, open wounds, chronic ulcer [4], trophic sores, eczema, and acne [5]. The use of silver based resin composites have been reported for the filling and coating of dental and medical devices. Similarly, the use of AgNP as an antimicrobial agent in toothpastes, shampoos, air sanitizer sprays, detergents and soaps has been reported previously [6]. AgNP are also investigated for its unique properties in catalysis, chemical sensing [7], biosensing, photonics and electronics [8], biomedical imaging, clinical diagnostics and therapeutics [9]. Pugazhendhi et al. (2016) reported that Dioscoreaalata mediated AgNP possess excellent antimicrobial activity by using agar well diffusion assay method [10]. Recently, Borrego et al. (2016) have been tested the potential antiviral activity of AgNP against Rift Valley fever virus (RVFV) by using both in vitro and in vivo (mice) studies. They claimed that AgNP has the ability to control the infectivity of RVFV [11]. Number of research papers have been published in 2016 reveal the in vivo evaluation of AgNP against Rhizoctoniasolani [12], Pseudomonas aeruginosa [13], lungs cancer cells [14], Bacillus subtilis [15], Endodontic Treatments [15] etc.

However, the toxicity of AgNP are reported by many researchers. The investigations of Mahmoudi and Serpooshan (2012) stated that the AgNP are highly toxic to healthy/normal cells [16]. Similarly, Bharadwaj Punita (2012) has been reported that AgNP are highly toxic to mammalian cells, brain cells, liver cells and stem cells. Furthermore, they also described that the nano-antimicrobial agentsare a big threaten to the whole biodiversity [17]. The previous studies also revealed that thezero-valent AgNP can generate highly reactive oxygen species (ROS) such as super oxide and hydroxyl radical, which can lead to oxidative stress [18,19]. Whereas, the ROS can cause the oxidative damage of biomolecules and DNA [20].

Due to bactericidal activities, AgNP have been extensively used in personal care products, home appliances, laundry additives, paints, food storage containers and food supplements. The unique properties of nanoparticles such as relatively high surface area, greater mobility and high chemical reactivity can result in unpresented environmental and public health hazards [21].

The aforementioned results clearly illustrated that before the use of AgNP against cancer cells and/or microbes, their cytotoxicity (against healthy cells) should be evaluated. As such, further studies are needed to fully evaluate its potential environmental and health hazards.

References

1. Pulizzi F. Nanotechnology in food: Silver-lined packaging. Nature Nanotechnology. 2016; doi: 10.1038/nnano.2016.11   
2. Sambale F, Wagner S, Stahl F, et al. Investigations of the toxic effect of silver nanoparticles on mammalian cell lines. Journal of Nanomaterials. 2015; doi: 10.1155/2015/136765   
3. Rajathi K, Sridhar S. Green synthesized silver nanoparticles from the medicinal plant Wrightia tinctoria and its antimicrobial potential. Intl. J. Chem. Tech. Res. 2013; 5(4): 1707-1713.   
4. Krithiga N, Rajalakshmi A, Jayachitra A. Green synthesis of silver nanoparticles using leaf extracts of Clitoria ternatea and Solanum nigrum and study of its antibacterial effect against common nosocomial pathogens. Journal of Nanoscience. 2015; doi: 10.1155/2015/928204   
5. Rakhmetova A, Bogoslovskaya O, Olkhovskaya I, et al. Concomitant action of organic and inorganic nanoparticles in wound healing and antibacterial resistance: Chitosan and copper nanoparticles in an ointment as an example. Nanotechnologies in Russia. 2015; 10(1-2): 149-157. doi: 10.1134/S1995078015010164   
6. Prabhu S, Poulose EK. Silver nanoparticles: mechanism of antimicrobial action, synthesis, medical applications, and toxicity effects. International Nano Letters. 2012; 2(1): 1-10. doi: 10.1186/2228-5326-2-32   
7. Prema P, Lakshmi Priya S, Rameshkumar G. Bio-based and chemical mediated fabrication of silver nanoparticles and evaluation of their potential antimicrobial activity-a comparative view. International Journal of Nanoparticles. 2012; 5(4): 338-357. doi: 10.1504/IJNP.2012.049910   
8. Sarkar R, Kumbhakar P, Mitra A. Green synthesis of silver nanoparticles and its optical properties. Digest Journal of Nanomaterials and Biostructures. 2010; 5(2): 491-496.   
9. Jiang W, Kim BY, Rutka JT, et al. Nanoparticle-mediated cellular response is size-dependent. Nature nanotechnology. 2008; 3(3): 145-150. doi: 10.1038/nnano.2008.30   
10. Pugazhendhi S, Sathya P, Palanisamy P, et al. Synthesis of silver nanoparticles through green approach using Dioscorea alata and their characterization on antibacterial activities and optical limiting behavior. Journal of Photochemistry and Photobiology B: Biology. 2016; 159: 155-160. doi: 10.1016/j.jphotobiol.2016.03.043   
11. Borrego B, Lorenzo G, Mota-Morales DJ, et al. Potential application of silver nanoparticles to control the infectivity of Rift Valley fever virus in vitro and in vivo. Nanomedicine: Nanotechnology, Biology and Medicine. 2016; 12(5): 1185-1192. doi: 10.1016/j.nano.2016.01.021   
12. Nejad MS, Bonjar GHS, Khatami M, et al. In vitro and in vivo antifungal properties of silver nanoparticles against Rhizoctonia solani, a common agent of rice sheath blight disease. IET Nanobiotechnology. 2016; doi: 10.1049/iet-nbt.2015.0121   
13. Nour EDS, Tayeb TAE, Abou-Aisha K, et al. In vitro and in vivo antimicrobial activity of combined therapy of silver nanoparticles and visible blue light against Pseudomonas aeruginosa. International journal of nanomedicine. 2016; 11(1): 1749. doi: https://dx.doi.org/10.2147/IJN.S102398   
14. He Y, Du Z, Ma S, et al. Effects of green-synthesized silver nanoparticles on lung cancer cells in vitro and grown as xenograft tumors in vivo. International journal of nanomedicine. 2016; 11(1): 1879-1882. doi: 10.2147/IJN.S103695   
15. Takamiya AS, Monteiro D, Bernabé D, et al. In Vitro and In Vivo Toxicity Evaluation of Colloidal Silver Nanoparticles Used in Endodontic Treatments. Journal of endodontics. 2016; 42(6): 953-960. doi: 10.1016/j.joen.2016.03.014   
16. Mahmoudi M, Serpooshan V. Silver-coated engineered magnetic nanoparticles are promising for the success in the fight against antibacterial resistance threat. ACS nano. 2012; 6(3): 2656-2664. doi: 10.1021/nn300042m   
17. Bharadwaj PS. Silver or silver nanoparticle a safety or a risk. Journal of Environmental Research And Development. 2012; 7(1A): 452-456.   
18. Puzyn T, Rasulev B, Gajewicz A, et al. Using nano-QSAR to predict the cytotoxicity of metal oxide nanoparticles. Nature nanotechnology. 2011; 6(3): 175-178. doi: 10.1038/nnano.2011.10   
19. Pal S, Tak YK, Song JM. Does the antibacterial activity of silver nanoparticles depend on the shape of the nanoparticle? A study of the gram-negative bacterium Escherichia coli. Applied and environmental microbiology. 2007; 73(6): 1712-1720. doi: 10.1128/AEM.02218-06   
20. Rahim M, Ullaha I, Khan A, et al. Health Risk from Heavy Metals via Consumption of Food Crops in the Vicinity of District Shangla. Journal of the Chemical Society of Pakistan. 2016; 38(1): 177-185.   
21. Navarro E, Piccapietra F, Wagner B, et al. Toxicity of silver nanoparticles to Chlamydomonas reinhardtii. Environmental science & technology. 2008; 42(23): 8959-8964.