Laboratory Scale Microbial Food Chain To Study Bioaccumulation, Biomagnification, and Ecotoxicity of Cadmium Telluride Quantum Dots Govind S. Gupta, †,‡ Ashutosh Kumar, † Violet A. Senapati, † Alok K. Pandey, ‡ Rishi Shanker,* ,† and Alok Dhawan* ,‡ † Division of Biological & Life Sciences, School of Arts & Sciences (Formerly, Institute of Life Sciences), Ahmedabad University, University Road, Navrangpura, Ahmedabad 380009, Gujarat, India ‡ Nanotherapeutics & Nanomaterial Toxicology Group, CSIR-Indian Institute of Toxicology Research (CSIR-IITR), Vishvigyan Bhawan, 31 Mahatma Gandhi Marg, P. O. Box 80, Lucknow 226001, Uttar Pradesh, India * S Supporting Information ABSTRACT: The increasing applications of engineered nano- materials (ENMs) in consumer products warrant a careful evaluation of their trophic transfer and consequent ecological impact. In the present study, a laboratory scale aquatic microbial food chain was established using bacteria (Escherichia coli (E. coli)) as a prey and ciliated protozoan (Paramecium caudatum) as a predator organism to determine the impact of cadmium telluride quantum dots (CdTe QDs). We observed that 29% of bacterivory potential of paramecium was lost, including an ∼12 h delay in doubling time on exposure to 25 mg/L CdTe QD (∼4 nm) as compared to control. The fluorescence based stoichiometric analysis revealed that 65% of the QDs bioaccumulated when paramecia were exposed to 25 mg/L QDs at 24 h. There was a significant (p < 0.05) increase in cellular cadmium (Cd) concentration at 24 h (306 ± 192 mg/L) as compared to 1 h (152 ± 50 mg/L). Moreover, the accumulation of Cd in E. coli (147 ± 25 mg/L) at 1 h of exposure to 25 mg/L QDs transferred 1.4 times higher Cd (207 ± 24 mg/L; biomagnification factor = 1.4) to its predator, paramecium. ■ INTRODUCTION The global production of engineered nanomaterials (ENMs) is increasing rapidly due to use of nanotechnology in public and industrial sectors. Various nanobased products such as personal care, health and fitness, electronics, textiles, sports, ceramics, energy, automotive, medicine, agriculture, and environmental remediation are already in the market. 1-4 It is predicted that by 2020 nanotechnology will have a market share of $3 trillion. 2 Keller and Lazareva 5 have estimated that the annual production of the most-used ENMs has reached around 320,000 t. Further, the release of these ENMs in environment is predicted to be 21% in aquatic systems, 17% in soil, and 2.5% in the air. 5,6 The entry of ENMs into aquatic environments can be during its production (0.1-2%), as well as through transport, consumers’ use, disposal, and recycling. 5,7-11 Despite these, ENMs find applications in sunscreens, cosmetics, and wastewater treatment and thus directly find their way into the aquatic environment. As large amounts of ENMs enter the aquatic environment, it is prudent to understand the threats posed by them to the environment and human health. There are more than 40 different types of nanomaterials being used in various products; these include ENMs of metals, metal oxides, carbonaceous materials, and composites. 12 Quantum dots (QDs) are one of the emerging ENMs that have gained wide importance due to their unique physical, chemical, and optical properties, which includes very small size as well as intense and long lasting fluorescence due to their broad excitation and narrow emission property. 13-15 The fluorescence of QDs can be tuned into different wavelengths of emission by manipulating their size. 14 Currently, the most projected applications of QDs are in the displays of light- emitting diodes, lighting, 16 biomedical imaging, 17 security inks, 18 quantum computing applications, 19 photovoltaics, 20 and photodynamic cancer therapies 21,22 Therefore, QDs may be released into the environment and cause adverse effects to humans and the environment. Recently, a pilot study by Pillai et al. 23 showed the release of QDs from free-standing polymer to the external environment. Derfus et al. 24 showed that toxicity of cadmium metal based QDs is often because of release of Cd 2+ ions in oxidative conditions. In contrast, Chen et al. 25 reported that the release of Cd 2+ ions cannot be the only reason for their potential toxicity in aqueous suspension. The data demonstrated that the Received: August 5, 2016 Revised: November 22, 2016 Accepted: January 9, 2017 Published: January 9, 2017 Article pubs.acs.org/est © XXXX American Chemical Society A DOI: 10.1021/acs.est.6b03950 Environ. Sci. Technol. XXXX, XXX, XXX-XXX