IP: 46.161.62.159 On: Mon, 08 Jul 2019 07:52:28 Copyright: American Scientific Publishers Delivered by Ingenta Copyright © 2019 American Scientific Publishers All rights reserved Printed in the United States of America Article Journal of Nanoscience and Nanotechnology Vol. 19, 7112–7122, 2019 www.aspbs.com/jnn Nanoparticle Size-Dependent Antibacterial Activities in Natural Minerals Souravi Bardhan 1 , Kunal Pal 2 , Shubham Roy 1 , Solanky Das 3 , Abhijit Chakraborty 4 , Parimal Karmakar 2 , Ruma Basu 5 , and Sukhen Das 1 ∗ 1 Department of Physics, Jadavpur University, Kolkata 700032, India 2 Department of Life Science and Biotechnology, Jadavpur University, Kolkata 700032, India 3 Department of Geology, Jadavpur University, Kolkata 700032, India 4 Department of Geology, Jogamaya Devi College, Kolkata 700026, India 5 Department of Physics, Jogamaya Devi College, Kolkata 700026, India The size-dependent antibacterial activities of three minerals namely; alkali feldspar, calcite and stibnite are reported as examined individually against Escherichia coli andStaphylococcus aureus by evaluating minimum inhibitory concentration (MIC) with colony counting method, along with cell survivability assay (MTT). Each of these minerals were grinded into fine-size fractions—S1 (bulk), S2 (ball milled) and S3 (nanosized) and spectroscopically characterized using X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM) and ultraviolet-visible (UV-Vis) spec- troscopy. Antibacterial activity was found to be highest in the nanosized (S3) minerals. Interaction between bacteria and nanosized mineral samples produce intracellular reactive oxygen species (ROS), which might cause higher bacterial mortality. The penetration due to nano-dimension is another significant observation as evidenced by bacterial FESEM micrographs. The current findings thus provide a pathway for future research on antibacterial products retrievable from widely avail- able geological materials. The size dependant antibacterial activity of naturally formed minerals is a new insight to reduce bacterial contamination in living systems. Keywords: Nanoparticles, Bacteria-Mineral Interaction, MIC, ROS, FESEM. 1. INTRODUCTION Minerals are essential natural resources that have huge impact on human health and have been used for medi- cal and other purposes for thousands of year. 1 By linking the naturally available materials with biomedical aspects, the researchers and geoscientists are attempting to dis- cover ways of mitigating environmental health problems. 2 The recognition of an intimate relationship between the environment, particularly geological materials and human health has led to the emergence of a new field of sci- ence called medical geology, 3 which deals with the rela- tionship between geological materials such as rocks and minerals, with the health problems in humans, animals and plants. 3 4 New products are now developed from minerals due to their bacteriological properties, such as in minerals like Talc, Halloysite, Sericite 5 6 which are used in different medical and dermatological products. Antibacterial tiles ∗ Author to whom correspondence should be addressed. and ceramics, antibacterial architectural coatings, etc. can also be made from commonly occurring minerals. 7 8 This is leading to the emergence of geomicrobiology which is an emerging frontier of interdisciplinary science. The science of geomicrobiology focuses mainly on the studies of mineral-microbe interactions and their applications 9 since minerals and rocks are the most fundamental earth materials with which microbes inter- act at all scales, from macroscopic to microscopic. 10–12 Many rocks and minerals contain the essential nutrients and energy required for microbial growth, and microbes actively extract nutrients from solid materials to sus- tain their metabolism and growth. 13 The modern era is giving emphasis on researches on novel, active and eco friendly antibacterial reagents, 14 as microbes are developing increasing resistance to multiple antibiotics. Thus demand of low cost, non-toxic natural antibacterial products have increased 15 16 beside various well known metal and metal oxide nanoparticles, such as CuO, ZnO, Ag + , etc. 17–22 7112 J. Nanosci. Nanotechnol. 2019, Vol. 19, No. 11 1533-4880/2019/19/7112/011 doi:10.1166/jnn.2019.16658