SINGLE-WALL CARBON NANOTUBES AS IN VITRO OXYGEN SENSORS

 

John M. Heddleston1, Jeremy N. Rich2, and Angela R. Hight-Walker1

1. Radiation and Biomolecular Physics Division, Gaithersburg, National Institute of Standards and Technology, Maryland

2. Department of Stem Cell Biology and Regenerative Medicine, Cleveland Clinic Foundation, Cleveland, Ohio

 

Solid tissue tumors are an internationally devastating health problem. Some malignancies, such as Glioblastoma Multiforme (WHO Grade IV brain tumor), demonstrate a universally negative prognosis with a median patient survival of 14 months after initial diagnosis (Stupp R, et al. Lancet Oncol. 2009). Current treatment modalities have done little to improve patient outcome despite the significant amount of research dollars and hours devoted to understanding tumors. Poor outcome is largely due to the heterogeneous nature of solid tumors and the presence of a tumorigenic subpopulation of cancer cells, termed cancer stem cells (CSCs; Singh SK, et al. Nature. 2004). Many labs have demonstrated the critical function of CSCs in propagating tumors as well as the ability of CSCs to evade typical treatment strategies (Bao S., et al. Nature. 2006). However the biological pathways that drive CSC tumorigenicity are not well understood. Several recent publications have revealed that oxygen concentration within the tumor can modulate cell phenotype and behavior. Specifically, the canonical molecular oxygen cell signaling pathway, regulated by the hypoxia inducible factors (HIFs), is not only required for CSC survival but can induce tumorigenicity in other cancer cell populations (Heddleston JM, et al. Cell Cycle. 2009).

Unfortunately, current methods of evaluating oxygen concentration and HIF function rely on immunodetection methods or viral integration of reporter constructs. These methods require extensive manipulation of the cellular material and can only measure oxygen concentration indirectly.  Furthermore, antibodies lack the fidelity to precisely measure in-cell fluctuation of oxygen. In order to address this deficiency, I propose to engineer single-wall carbon nanotubes (SWCNTs) bearing oxygen-labile surface modifications to precisely measure changes in oxygen tension in human cancer cells in vitro. SWCNTs are inherently stable structures that can be outfitted with a variety of modifications and bear a distinct Raman spectral signature. Previous publications have shown that it is possible to quantify changes in the Raman signature of SWCNTs when they are modified with labile molecules, such as single-stranded DNA (Heller DA, et al. Nature Nanotech. 2008). Therefore, modifying SWCNTs with oxygen-labile moieties and then introducing them into cancer cells will allow for precise measurement of cellular oxygen concentration via changes in the SWCNT Raman signature. This novel measurement method could be applicable to nanomedicine and environmental, health, and safety studies of nanomaterials.