Cellular uptake Uptake, Translocation, and Transmission of Carbon Nanomaterials in Rice Plants** Sijie Lin, Jason Reppert, Qian Hu, JoAn S. Hudson, Michelle L. Reid, Tatsiana A. Ratnikova, Apparao M. Rao, Hong Luo, * and Pu Chun Ke* Recent development of nanotechnology has reshaped the landscape of modern science and technology, while in the meantime raised concerns about the adverse effects of nanomaterials on biological systems and the environment. [1,2] Owing to their mutual interaction, carbon-based nanomater- ials readily aggregate and are not considered potential contaminants in the liquid phase. [3] However, when discharged into the environment, the hydrophobicity of nanomaterials can be averted through their interaction with natural organic matter (NOM), [4] a heterogeneous mixture of decomposed animals and plants and a major pollutant carrier [5] in nature. Consequently, mobile NOM-modified nanomaterials may pose a threat to ecological terrestrial species through further physical, chemical, and biological processes. The impact of nanomaterials on high plants has scantly been examined in the current literature. Among the studies available, [6–12] none have used major food crops or carbon nanoparticles (a major class of nanomaterials) for their evaluations. Although both enhanced and inhibited growth have been reported for vegetations exposed to nanomaterials at various developmental stages, [6–12] including seed germina- tion, root growth, and photosynthesis, fundamental questions remain regarding the uptake, accumulation, translocation, and transmission of nanomaterials in plant cells and tissues, and the impact of these processes on plant reproduction. [13] Here, we provide the first evidence on the uptake, accumulation, and generational transmission of NOM-suspended carbon nano- particles in rice plants, the staple food crops of over half the world’s population. The data presented in this Communication suggest the potential impact of nanomaterial exposure on plant development and the food chain, and prompt further investigation into the genetic consequences through plant– nanomaterial interactions. NOM in freshwater ecosystems ususally has a concentra- tion between 1–100 mg L 1 . [14] To mimic the natural ecosystems we formed a NOM solution of 100 mg L 1 in Milli-Q water and suspended fullerene C 70 and multiwalled carbon nanotubes (MWNTs) in the NOM. Using a Zetasizer (S90, Malvern Instruments) we identified three hydrodynamic diameters of 1.19 (major), 17.99, and 722.10 nm for C 70 –NOM and one major hydrodynamic diameter of 239.70 nm for MWNT–NOM (see Supporting Information, Sections 1C and 1D). The nonspecific assembly of NOM with C 70 or MWNTs is believed to be a dynamic equilibrium process [4] with the hydrophobic moieties of the NOM interacting and p-stacking with the hydrophobic carbon nanoparticle surfaces. Newly harvested rice seeds were incubated in Petri dishes that contained 15 mL of different concentrations of C 70 –NOM and MWNT–NOM in rice germination buffer. After germina- tion at 25  1 8C for 2 weeks the seedlings were transplanted to soil in big pots and grown in a green house to maturity without addition of nanoparticles. For each sample concentration, 5 pots of plants were maintained for analysis. These plants are referred to as the first generation. The plants grown in the germination buffer are known as the control. Identical amounts of NOM were used for C 70 –NOM and MWNT– NOM for each concentration. For example, the NOM concentration in ‘‘NOM400’’ was identical to that in C 70 –NOM or MWNT–NOM of 400 mg L 1 . To investigate generational transmission of nanomaterials, mature seeds from the control plants and C 70 -treated plants were harvested 6 months after germination, and 60 seeds of similar size for each plant were chosen and sterilized using the same method as described above. Ten seeds were planted in each Petri dish filled with rice germination buffer and kept at 25  1 8C for 2 weeks. These germinated plants without the addition of nanomaterials are known as the second generation. communications [  ] Prof. H. Luo, Q. Hu Department of Genetics and Biochemistry Clemson University Clemson, SC 29634 (USA) E-mail: hluo@clemson.edu Prof. P. C. Ke, S. Lin, J. Reppert, M. L. Reid, T. A. Ratnikova, Prof. A. M. Rao Department of Physics and Astronomy Center for Optical Materials Science and Engineering Technologies Clemson University Clemson, SC 29634 (USA) E-mail: pcke11@clemson.edu Dr. J. S. Hudson Electron Microscopy Facility Clemson University Clemson, SC 29634 (USA) [  ] Ke acknowledges an NSF Career award #CBET-0744040 and NSF grant #CBET-0736037. Luo acknowledges USDA grants BRAG 2007-33522-18489 and CSREES SC-1700315. The authors thank Xiaoqian Sun, Bevan Elliott, and Malcolm Skove for discussions and Godfrey Kimball for critical reading of our manuscript. This is Technical Contribution No. 5515 of the Clemson University Exper- iment Station. : Supporting Information is available on the WWW under http:// www.small-journal.com or from the author. DOI: 10.1002/smll.200801556 1128 ß 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim small 2009, 5, No. 10, 1128–1132