Colloids and Surfaces B: Biointerfaces 105 (2013) 37–42 Contents lists available at SciVerse ScienceDirect Colloids and Surfaces B: Biointerfaces jou rn al h om epage: www.elsevier.com/locate/colsurfb Non-hazardous anticancerous and antibacterial colloidal ‘green’ silver nanoparticles Shaswat Barua a , Rocktotpal Konwarh a , Satya Sundar Bhattacharya b , Pallabi Das b , K. Sanjana P. Devi c , Tapas K. Maiti c , Manabendra Mandal d , Niranjan Karak a,∗ a Advanced Polymer and Nanomaterial Laboratory, Department of Chemical Sciences, Tezpur University, Napaam 784 028, Assam, India b Department of Environmental Science, Tezpur University, Napaam 784 028, Assam, India c Department of Biotechnology, Indian Institute of Technology, Kharagpur, West Bengal, India d Department of Molecular Biology and Biotechnology, Tezpur University, Napaam 784 028, Assam, India a r t i c l e i n f o Article history: Received 25 September 2012 Accepted 16 December 2012 Available online xxx Keywords: Thuja occidentalis Silver nanoparticles Green nanotechnology Anti-cancerous Antibacterial Ecocompatibility a b s t r a c t Poly(ethylene glycol) stabilized colloidal silver nanoparticles were prepared using the reductive potency of the aqueous extract of Thuja occidentalis leaves under ambient conditions. The nanoparticles were well dispersed within a narrow size spectrum (7–14 nm) and displayed characteristic surface plasmon resonance peak at around 420 nm and Bragg’s reflection planes of fcc structure. MTT assay revealed the dose-dependent cytocompatibility and toxicity of the nanoparticles with the L929 normal cell line. On the other hand, the antiproliferative action of the nanoparticles was evaluated on HeLa cell (cancerous cells) line. Fluorescence and phase contrast microscopic imaging indicated the appearance of multinu- cleate stages with aggregation and nuclear membrane disruption of the HeLa cells post treatment with the nanoparticles. The interaction at the prokaryotic level was also assessed via differential antibacterial efficacy against Staphylococcus aureus (MTCC 3160) and Escherichia coli (MTCC 40). Under these perspec- tives, it is also necessary to observe the environmental impact of the prepared silver nanoparticles. Hence, the dose dependent toxicity of silver nanoparticles was evaluated upon the earthworm species Eisenia fetida. Neither the survival nor the reproduction was affected by the addition of silver nanoparticles up to 1000 ppm. Thus these ‘green’ silver nanoparticles have promising potential as future materials. © 2012 Elsevier B.V. All rights reserved. 1. Introduction A biogenic approach to prepare nanomaterials is a highly focused upon research area [1]. We have recently reported the utilization of various bio-resources for preparation of polymer- stabilized silver nanoparticles in accordance with the dictates of ‘green nanotechnology’ [2–4]. In this context, we have tried to explore yet another phyto-resource – Thuja occidentalis for the preparation of poly(ethylene glycol) assisted silver (PEG@Ag) nanoparticles. Thuja occidentalis is an evergreen coniferous tree, in the cypress family Cupressaceae with wide applications in homeopathy and evidence-based phytotherapy. It is pertinent to mention that a number of in vitro and in vivo studies bear testimony to Thuja’s immunopharmacological potential [5] and antiviral action. Herein, we report the utility of Thuja’s aqueous leaf extract to reduce silver salt under ambient conditions in a neutral medium (pH = 7). ∗ Corresponding author. Tel.: +91 3712 267009; fax: +91 3712267006. E-mail address: karakniranjan@yahoo.com (N. Karak). The reports on broad spectrum of antimicrobial activity [6] have attested tremendous popularity to silver nanoparticles in ther- apeutic applications. In this context, the antimicrobial action of the green silver nanoparticles against a panel of bacterial species (illustrating the response at the prokaryotic level) was evaluated. It is pertinent to mention that a search for the indexed phrase, ‘silver nanoparticles for biomedical applications’, in various lit- erature databases returns considerable number of hits [7,8]. In this regard, establishing the cytocompatibility and genocompati- bility of the silver nanoparticles [9] is pre-requisite. Even though a number of reports are available on bio-resource based prepa- ration of silver nanoparticles [6], not many have addressed their toxicity issues. Tunable antibacterial coatings with silver nanopar- ticles, generated through in situ route, which support mammalian cell growth, have been developed [10]. Such reports on utilities of silver nanoparticles call for assessment of their biocompatibil- ity. Deciphering molecular events that regulate bioaccumulation and toxicity of nanoparticles is quite perplexing. Here, we have tried to assess the differential effect (if any) of the prepared silver nanoparticles on the morphology and proliferation of L929 (a normal cell line) and HeLa cell line (a cancerous cell line). 0927-7765/$ – see front matter © 2012 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.colsurfb.2012.12.015