3rd International Symposium on Nanotechnology, Occupational and Environmental Health Aug. 29 to Sep. 1, 2007, Taipei, Taiwan
IN-VIVO EXPOSURE CHARACTERIZATION AND VISUALIZATION OF SWNH AGGREGATES R. M. Lynch, B. H. Voy, D. F. Glass, S. M. Mahurin, B. Zhao, L. Tetard, Ali Passian, K. T. Venmar, T. Thundat, and M.-D. Cheng* Oak Ridge National Laboratory, Oak Ridge, TN 37831-6038, USA Tel: 865-241-5918; Fax: 865-576-8646; E-mail:
[email protected] Keywords: SWNH; Visualization; Clustering; Inflammatory As the manufacturing and use of nanomaterials and nanoparticle clusters/aggregates become prevalent in the future, it will be necessary to understand the biological interactions with this new class of materials introduced through various routes, intentionally or unintentionally. However, there currently exist a host of technical/methodological issues related to nanotoxicological study1. For example, the ability to generate reproducible precision nanomaterial and nanoparticles is critically needed for both toxicological evaluation and pharmaceutical applications. Technology for tracing and visualization of nanomaterials in biological systems are also lacking. Single-walled carbon nanohorn (SWNH) is a unique carbon nanostructure belonging to the same family as the famous carbon nanotubes. SWNH aggregates can be produced through laser vaporization of carbon at room temperature2; the aggregates are of particular interest to energy application such as hydrogen storage3 and new-generation of fuel cells3. Unlike carbon nanotubes that are made using metal catalysts, SWNHs can be made without the use of a metal catalyst providing an opportunity for nanotoxicological study of purest carbon nanoparticles with no complication of trace metal toxicity that the nanotubes might have. We summarize results from our ongoing biological research on SWNHs. Our results were from in vivo animal aspiration experiments, in contrast to the results of a recent publication4 that were based on phenotypic observation of cell-line exposure experiments. The characterization results2 of ORNL-produced SWNHs are presented in Figure 1, which include low- (Figure 1a) and high-resolution (Figure 1b) structural images of SWNHs, the thermal gravimetric analysis (Figure 1c) and characteristic Raman (Figure 1d) results. We coated the SWNH powder with Pluronic F-127, which is a biocompatible polymer, to facilitate the dispersion of SWNHs in suspension during pressuredriven nebulization in mice aspiration and nose-only inhalation experiments. The phenotypic and genomic expression results are reported by5. Twenty-two inflammatory measures from bronchoalveolar lavage were assayed. Only five showed significant changes from the control (e.g., G-CSF, GM-CSF, IP-10, and IL-5) in 24 hours after exposure indicating acute inflammatory responses; however, the responses subsided in 7 days and no significant difference could be found between the control and exposed groups. Whole lung microarray analysis also found few differences between SWNH-exposed and controls of several genes in 24 hours. The SWNH aggregates did penetrate cell membranes; the stained optical microscopy5 images show the presence of SWNH aggregates in mice red blood cell. The images results are consistent with visualization by using the Scanning Near Field Ultrasound Holography9 (SNFUH) available at the Oak Ridge National Laboratory. The SNFUH also provided transport information regarding the transport dynamics of the SWNH aggregates into the cells. The visualization showing consistent results with those obtained from the stained optical microscopy.
3rd International Symposium on Nanotechnology, Occupational and Environmental Health Aug. 29 to Sep. 1, 2007, Taipei, Taiwan
Fig. 1. A low-magnification SEM image (Figure 1a) shows that SWNH aggregates have an irregular spherical morphology in a variety of diameters (in this distribution, ranging from 40 nm to 120 nm). A high resolution TEM image (Figure 1b) shows an individual SWNH aggregate, which is composed of radially oriented SWNHs with conical tips. TGA data (Figure 1c) of SWNHs were recorded by a TA Q-500 TGA instrument with a heating rate of 5K/min in air. The derivative peak appearing at 893 K corresponds to the contribution from SWNHs6. The Raman spectrum of SWNHs (Figure 1d) measured by a Renishaw Raman spectroscopy instrument (λexc = 633 nm) shows two broad peaks centered at 1317 cm-1 and 1588 cm-1, which can be assigned to the D-band attributed to disordered sp2 carbon in defect sites of nanohorns, and the G-band associated with the tangential C-C bond stretching vibration in graphitic carbon, respectively7-8.
Acknowledgements The research was supported by the Oak Ridge National Laboratory/Laboratory Directed Research and Development program office. The authors thank technical support in material synthesis and characterization provided by the functional nanomaterial group at the Center for Nanophase Materials Sciences operated by Oak Ridge National Laboratory for the Department of Energy/Office of Science. The functional nanomaterial group is headed by Dr. David B. Geohegan. Oak Ridge National Laboratory is managed by UT-Battelle, LLC, for the U.S. Dept. of Energy under contract DE-AC05-00OR22725. Disclaimer The submitted manuscript has been authored by a contractor of the U.S. Government under contract DEAC05-00OR22725. Accordingly, the U.S. Government retains a nonexclusive, royalty-free license to publish or reproduce the published form of this contribution, or allow others to do so, for U.S. Government purposes. References [1] Maynard, A. “Safe handling of nanotechnology,” Nature, 444 (7117) pp. 243-400 (Nov. 16, 2006) [2] Cheng, M.-D. et al. “Formation Studies and Controlled Production of Carbon Nanohorns Using Continuous In-Situ Characterization Techniques”, Nanotechnology, 18 (2007) 185604. [3] http://www.hydrogen.energy.gov/pdfs/review06/stp_12_geohegan-brown.pdf [4] Isobe, H. et al. “Preparation, purification, characterization, and cytoxocitity assessment of water-soluble, transition-metal-free carbon nanotube aggregates”, Angew. Chem. Int. Ed., 45: 667-680 (2006) [5] Lynch, R. et al. “Assessing the pulmonary toxicity of single-walled carbon nanohorns”, in review, Nanotoxicology, 2007. [6] Zhang, M. et al. “Isolating Single-Wall Carbon Nanohorns as Small Aggregates through a Dispersion Method”, J. Phys. Chem. B, 109, 22201, 2005 [7] Bekyarova, E. et al. “Single-Wall Nanostructured Carbon for Methane Storage”, Phys. Chem. B, 107, 4681, 2003 [8] Yang, C. et al. “Highly Ultramicroporous Single-Walled Carbon Nanohorn Assemblies”, Advanced Materials, 17, 866, 2005 [9] Tetard, L. “Direct subsurface visualization of nanoparticles in the lung cells of exposed mice: a potential nanotoxicological procedure”, in review, Nature/Biotechnology, 2007.
