Cytotoxicity and antibacterial activities of plant-mediated synthesized zinc oxide (ZnO) nanoparticles using Punica granatum (pomegranate) fruit peels extract Siti Nur Amalina Mohamad Sukri a , Kamyar Shameli a, * , Magdelyn Mei-Theng Wong b , Sin-Yeang Teow b , Jactty Chew c , Nur Afini Ismail a a Malaysia-Japan International Institute of Technology, Universiti Teknologi Malaysia, Jalan Sultan Yahya Petra, 54100, Kuala Lumpur, Malaysia b Department of Medical Sciences, School of Healthcare and Medical Sciences, Sunway University, Jalan Universiti, Bandar Sunway, 47500 Selangor Darul Ehsan, Malaysia c Department of Biological Sciences, School of Science and Technology, Sunway University, Jalan Bandar Sunway, 47500, Selangor Darul Ehsan, Malaysia article info Article history: Received 7 February 2019 Received in revised form 3 April 2019 Accepted 5 April 2019 Available online 6 April 2019 Keywords: Zinc oxide nanoparticles Punica granatum Antibacterial applications Cytotoxicity assay Transmission electron microscopy abstract The unique properties of zinc oxide nanoparticles (ZnO-NPs) produced using plant extract make them attractive for use in medical as well as industrial applications, and it is necessary to develop environ- mentally friendly methods for their synthesis. This can be accomplished by replacing the traditional chemical compounds for the reduction of the zinc ions to ZnO-NPs during synthesis with natural plant extracts. Here, the biosynthesis of ZnO-NPs using Punica granatum (P. granatum) fruit peels extract was investigated as the reducing and stabilizing agent. The P. granatum/ZnO-NPs with spherical and hexag- onal shapes were biosynthesized at different annealing temperatures. The X-ray diffraction analysis confirmed the synthesis of highly pure ZnO-NPs with increasing crystallinity in higher annealing tem- peratures. The ZnO-NPs displayed characteristic absorption peaks between 370 and 378 nm in the UV evis spectra. Transmission electron microscopy (TEM) imaging showed the formation of mostly spher- ical and hexagonal-shaped ZnO-NPs in the mean size of 32.98 nm and 81.84 nm at 600  C and 700  C respectively. According to FTIR spectrum, strong absorption bands in the range of 462e487 cm 1 cor- responding to ZneO bond stretching can be seen. Antibacterial activities of P. granatum/ZnO-NPs against Escherichia coli (E. coli) and Enterococcus faecalis (E. faecalis) were investigated and compared. Results obtained show that smaller-sized P. granatum/ZnO-NPs are more effective in inhibiting growth of both bacteria. In addition, cytotoxicity assays were performed for P. granatum/ZnO-NPs against human colon normal and cancerous cells. P. granatum/ZnO-NPs exhibited similar killing activities of both cell lines at the concentration of 31.25 mg/mL. The biosynthesized ZnO-NPs could offer potential applications in bio- medical field. © 2019 Published by Elsevier B.V. 1. Introduction The field of nanotechnology has been constantly growing as re- searchers explore more about novel materials in nanoscale level [1]. Nanotechnology provides the platform for construction of novel nanostructures, understanding their novel properties, and learning how to make use of them in different field of applications [2]. Nanoparticles are generally synthesized in the range of 1e 100 nm and can be produced from many metal compounds like silver, gold, zinc, copper, iron, titanium, etc., by various physical and chemical methods [3]. Even though synthesis of nanoparticles can be carried out by any method, green synthesis has gained prominence in recent years [4]. Compared to traditional chemical or physical methods, green synthesis method in synthesizing nanoparticles offers many advantages, such as requires mild reaction conditions, uses less toxic chemicals, is inexpensive and ecofriendly [5]. The green synthesis method utilizes a variety of biological agents, including plant ex- tracts, fruit extracts, microbes, and others [6]. Zinc oxide (ZnO) is a semiconductor with a large band gap of about 3.37 eV [7] and high exciton binding energy (60 meV) [8]. It is a multifunctional compound with unique optic, luminescent, * Corresponding author. E-mail address: kamyarshameli@gmail.com (K. Shameli). Contents lists available at ScienceDirect Journal of Molecular Structure journal homepage: http://www.elsevier.com/locate/molstruc https://doi.org/10.1016/j.molstruc.2019.04.026 0022-2860/© 2019 Published by Elsevier B.V. Journal of Molecular Structure 1189 (2019) 57e65