High-Resolution and High-Contrast Fluorescence Imaging with Carbon Nanomaterials for Preclinical and Clinical Applications
John Czerski
Single Molecule Biophysics Laboratory, Department of Physics, Colorado School of Mines, Golden, USA
Search for more papers by this authorSusanta K. Sarkar
Single Molecule Biophysics Laboratory, Department of Physics, Colorado School of Mines, Golden, USA
Search for more papers by this authorJohn Czerski
Single Molecule Biophysics Laboratory, Department of Physics, Colorado School of Mines, Golden, USA
Search for more papers by this authorSusanta K. Sarkar
Single Molecule Biophysics Laboratory, Department of Physics, Colorado School of Mines, Golden, USA
Search for more papers by this authorYuen Yung Hui
Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei, Republic of China
Search for more papers by this authorHuan-Cheng Chang
Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei, Republic of China
Search for more papers by this authorHaifeng Dong
University of Science and Technology Beijing, P.R. China
Search for more papers by this authorXueji Zhang
University of Science and Technology Beijing, P.R. China
Search for more papers by this authorSummary
This chapter reviews some of the most promising carbon nanomaterials (CNMs) for fluorescent imaging and their advantages, specific properties, and potential applications. It discusses fluorescent nanodiamonds (FNDs) for visible wavelengths and carbon nanotubes for near-infrared (NIR) wavelengths in the context of biomedical imaging. The properties of FNDs and carbon nanotubes provide multiple pathways toward high-contrast fluorescent imaging, contrast for other imaging modalities, and functional imaging. Carbon nanodots can be separated into two main groups based on their composition, crystalline carbon quantum dots (CQDs) and amorphous varieties. FNDs have indefinite photostability, broad excitation, and emission spectra in the visible and NIR range, and magnetic field-dependent fluorescence emission. While there are a variety of fluorescent CNMs, the most promising for biomedical imaging are FNDs and single-walled carbon nanotubes (SWCNTs). Carbon dots and FNDs are most used CNMs for imaging in the short-wavelength window.
References
- Hong, G., Diao, S., Antaris, A. et al. (2015). Carbon nanomaterials for biological imaging and nanomedicinal therapy. Chemical Reviews 115 (19): 10816–10906.
- Park, S.-m., Aalipour, A., Vermesh, O. et al. (2017). Towards clinically translatable in vivo nanodiagnostics. Nature Reviews Materials 2: 17014.
- Scheinberg, D.A., Grimm, J., Heller, D.A. et al. (2017). Advances in the clinical translation of nanotechnology. Current Opinion in Biotechnology 46: 66–73.
-
Merchant, K. and Sarkar, S.K. (2016). Fluorescent Nanodiamonds for molecular and cellular bioimaging. IEEE Journal of Selected Topics in Quantum Electronics
22 (3): 235–245.
10.1109/JSTQE.2015.2512981 Google Scholar
- Hsiao, W.W.-W., Hui, Y.Y., Tsai, P.-C. et al. (2016). Fluorescent nanodiamond: a versatile tool for long-term cell tracking, super-resolution imaging, and nanoscale temperature sensing. Accounts of Chemical Research 49 (3): 400–407.
- Bumb, A., Sarkar, S.K., Billington, N. et al. (2013). Silica encapsulation of fluorescent nanodiamonds for colloidal stability and facile surface functionalization. Journal of the American Chemical Society 135 (21): 7815–7818.
- de Lange, G., Ristè, D., Dobrovitski, V.V. et al. (2011). Single-spin Magnetometry with multipulse sensing sequences. Physical Review Letters 106 (8): 080802.
- Doherty, M.W., Acosta, V.M., Jarmola, A. et al. (2014). Temperature shifts of the resonances of theNV−center in diamond. Physical Review B 90 (4).
- Maze, J.R., Stanwix, P.L., Hodges, J.S. et al. (2008). Nanoscale magnetic sensing with an individual electronic spin in diamond. Nature 455 (7213): 644–647.
-
Plakhotnik, T., Doherty, M.W., Cole, J.H.
et al. (2014). All-optical thermometry and thermal properties of the optically detected spin resonances of the NV (−) center in nanodiamond. Nano Letters
14 (9): 4989–4996.
10.1021/nl501841d Google Scholar
- Wrachtrup, J., von Borczyskowski, C., Bernard, J. et al. (1993). Optical detection of magnetic resonance in a single molecule. Nature 363 (6426): 244–245.
- Hui, Y.Y., Su, L.J., Chen, O.Y. et al. (2014). Wide-field imaging and flow cytometric analysis of cancer cells in blood by fluorescent nanodiamond labeling and time gating. Scientific Reports 4: 5574.
-
Sarkar, S.K., Bumb, A., Wu, X.
et al. (2014). Wide-field in vivo background free imaging by selective magnetic modulation of nanodiamond fluorescence. Biomedical Optics Express
5 (4): 1190–1202.
10.1364/BOE.5.001190 Google Scholar
- Colomb, W., Czerski, J., Sau, J. et al. (2017). Estimation of microscope drift using fluorescent nanodiamonds as fiducial markers. Journal of Microscopy 266 (3): 298–306.
- Hemelaar, S., de Boer, P., Chipaux, M. et al. (2017). Nanodiamonds as multi-purpose labels for microscopy. Scientific Reports 7.
- Hui, Y.Y., Cheng, C.-L., and Chang, H.-C. (2010). Nanodiamonds for optical bioimaging. Journal of Physics D: Applied Physics 43 (37): 374021.
- McGuinness, L., Yan, Y., Stacey, A. et al. (2011). Quantum measurement and orientation tracking of fluorescent nanodiamonds inside living cells. Nature Nanotechnology 6 (6): 358–363.
- Iakoubovskii, K., Minami, N., Kim, Y. et al. (2006). Midgap luminescence centers in single-wall carbon nanotubes created by ultraviolet illumination. Applied Physics Letters 89 (17): 173108.
- Miyauchi, Y., Oba, M., and Maruyama, S. (2006). Cross-polarized optical absorption of single-walled nanotubes by polarized photoluminescence excitation spectroscopy. Physical Review B 74 (20).
- Weisman, R.B., Bachilo, S.M., Strano, M.S. et al. (2003). (n,m)-assigned absorption and emission spectra of single-walled carbon nanotubes. AIP Conference Proceedings 685: 241–245.
- Carlson, L.J., Maccagnano, S.E., Zheng, M. et al. (2007). Fluorescence efficiency of individual carbon nanotubes. Nano Letters 7 (12): 3698–3703.
- de la Zerda, A., Liu, Z., Bodapati, S. et al. (2010). Ultrahigh sensitivity carbon nanotube agents for photoacoustic molecular imaging in living mice. Nano Letters 10 (6): 2168–2172.
- Serpell, C.J., Rutte, R.N., Geraki, K. et al. (2016). Carbon nanotubes allow capture of krypton, barium and lead for multichannel biological X-ray fluorescence imaging. Nature Communications 7: 13118.
- Wang, S., Lin, Q., Chen, J. et al. (2017). Biocompatible polydopamine-encapsulated gadolinium-loaded carbon nanotubes for MRI and color mapping guided photothermal dissection of tumor metastasis. Carbon 112: 53–62.
- Li, D. and Kaner, R.B. (2008). Graphene-based materials. Science 320 (5880): 1170–1171.
- Shen, H., Zhang, L., Liu, M. et al. (2012). Biomedical applications of Graphene. Theranostics 2 (3): 283–294.
- Cushing, S.K., Li, M., Huang, F. et al. (2014). Origin of strong excitation wavelength dependent fluorescence of Graphene oxide. ACS Nano 8 (1): 1002–1013.
- Pei, S. and Cheng, H.-M. (2012). The reduction of graphene oxide. Carbon 50 (9): 3210–3228.
- Saxena, M. and Sarkar, S. (2013). Fluorescence imaging of human erythrocytes by carbon nanoparticles isolated from food stuff and their fluorescence enhancement by blood plasma. Materials Express 3 (3): 201–209.
- Zhu, S., Song, Y., Zhao, X. et al. (2015). The photoluminescence mechanism in carbon dots (graphene quantum dots, carbon nanodots, and polymer dots): current state and future perspective. Nano Research 8 (2): 355–381.
- Li, L., Wu, G., Yang, G. et al. (2013). Focusing on luminescent graphene quantum dots: current status and future perspectives. Nanoscale 5 (10): 4015–4039.
- Bhunia, S.K., Saha, A., Maity, A.R. et al. (2013). Carbon nanoparticle-based fluorescent bioimaging probes. Scientific Reports 3: 1473.
- Fan, R.-J., Sun, Q., Zhang, L. et al. (2014). Photoluminescent carbon dots directly derived from polyethylene glycol and their application for cellular imaging. Carbon 71: 87–93.
- Jiang, K., Sun, S., Zhang, L. et al. (2015). Bright-yellow-emissive N-doped carbon dots: preparation, cellular imaging, and Bifunctional sensing. ACS Appl Mater Interfaces 7 (41): 23231–23238.
-
Liu, Y., Liu, C.Y., and Zhang, Z.Y. (2011). Synthesis and surface photochemistry of graphitized carbon quantum dots. Journal of Colloid and Interface Science
356 (2): 416–421.
10.1016/j.jcis.2011.01.065 Google Scholar
- Yang, Z., Xu, M., Liu, Y. et al. (2014). Nitrogen-doped, carbon-rich, highly photoluminescent carbon dots from ammonium citrate. Nanoscale 6 (3): 1890–1895.
- Du, F., Zhang, L., Zhang, L. et al. (2017). Engineered gadolinium-doped carbon dots for magnetic resonance imaging-guided radiotherapy of tumors. Biomaterials 121: 109–120.
- Lee, C. et al. (2016). Biodegradable nitrogen-doped carbon Nanodots for non-invasive Photoacoustic imaging and Photothermal therapy. Theranostics 6 (12): 2196–2208.
- Yu, S.-J., Kang, M.-W., Chang, H.-C. et al. (2005). Bright fluorescent nanodiamonds: no photobleaching and low cytotoxicity. Journal of the American Chemical Society 127 (50): 17604–17605.
- Fu, C.-C., Lee, H.-Y., Chen, K. et al. (2007). Characterization and application of single fluorescent nanodiamonds as cellular biomarkers. Proceedings of the National Academy of Sciences 104 (3): 727–732.
- Pham, L.M., Le Sage, D., Stanwix, P.L. et al. (2011). Magnetic field imaging with nitrogen-vacancy ensembles. New Journal of Physics 13 (4): 045021.
- Jarmola, A., Acosta, V., Jensen, K. et al. (2012). Temperature-and magnetic-field-dependent longitudinal spin relaxation in nitrogen-vacancy ensembles in diamond. Physical Review Letters 108 (19): 197601.
- Jelezko, F. and Wrachtrup, J. (2006). Single defect centres in diamond: a review. Physica Status Solidi (A) 203 (13): 3207–3225.
- Doherty, M.W., Manson, N.B., Delaney, P. et al. (2013). The nitrogen-vacancy colour Centre in diamond. Physics Reports 528 (1): 1–45.
- Maze, J., Gali, A., Togan, E. et al. (2011). Properties of nitrogen-vacancy centers in diamond: the group theoretic approach. New Journal of Physics 13 (2): 025025.
- Smith, B.R., Inglis, D.W., Sandnes, B. et al. (2009). Five-nanometer diamond with luminescent nitrogen-vacancy defect centers. Small 5 (14): 1649–1653.
- Mohtashami, A., Frimmer, M., and Koenderink, A.F. (2013). Quantum efficiency of single NV centers in nanodiamonds. In 2013 Conference on Lasers & Electro-Optics Europe & International Quantum Electronics Conference CLEO EUROPE/IQEC.
- Davies, G. (1979). Dynamic Jahn-teller distortions at trigonal optical centres in diamond. Journal of Physics C: Solid State Physics 12 (13): 2551.
- Davies, G. and Hamer, M.F. (1976). Optical studies of the 1.945 eV Vibronic band in diamond. Proceedings of the Royal Society of London. A. Mathematical and Physical Sciences 348 (1653): 285–298.
- Dolde, F., Doherty, M.W., Michl, J. et al. (2014). Nanoscale detection of a single fundamental charge in ambient conditions using the NV- center in diamond. Physical Review Letter 112 (9): 097603.
- Dolde, F., Fedder, H., Doherty, M.W. et al. (2011). Electric-field sensing using single diamond spins. Nature Physics 7 (6): 459–463.
- Maclaurin, D., Hall, L.T., Martin, A.M. et al. (2013). Nanoscale magnetometry through quantum control of nitrogen–vacancy centres in rotationally diffusing nanodiamonds. New Journal of Physics 15 (1): 013041.
- Toyli, D.M., de las Casas, C.F., Christle, D.J. et al. (2013). Fluorescence thermometry enhanced by the quantum coherence of single spins in diamond. Proceedings of the National Academy of Sciences of the United States of America 110 (21): 8417–8421.
- Zhu, M., Toda, M., and Ono, T. (2016). Scanning probe with nitrogen vacancy centers in diamond particle for magnetic resonance imaging . In 2016 IEEE 16th International Conference on Nanotechnology (IEEE-NANO).
- Singh, R. and Torti, S.V. (2013). Carbon nanotubes in hyperthermia therapy. Advanced Drug Delivery Reviews 65 (15): 2045–2060.
- Barone, P.W., Baik, S., Heller, D.A. et al. (2005). Near-infrared optical sensors based on single-walled carbon nanotubes. Nature Materials 4 (1): 86–92.
- Welsher, K., Sherlock, S.P., and Dai, H. (2011). Deep-tissue anatomical imaging of mice using carbon nanotube fluorophores in the second near-infrared window. Proceedings of the National Academy of Sciences of the United States of America 108 (22): 8943–8948.
- Welsher, K., Liu, Z., Sherlock, S.P. et al. (2009). A route to brightly fluorescent carbon nanotubes for near-infrared imaging in mice. Nature Nanotechnology 4 (11): 773–780.
- Welsher, K., Liu, Z., Daranciang, D. et al. (2008). Selective probing and imaging of cells with single walled carbon nanotubes as near-infrared fluorescent molecules. Nano Letters 8 (2): 586–590.
- Cherukuri, P., Bachilo, S.M., Litovsky, S.H. et al. (2004). Near-infrared fluorescence microscopy of single-walled carbon nanotubes in phagocytic cells. Journal of the American Chemical Society 126 (48): 15638–15639.
- O'Connell, M.J., Bachilo, S.M., Huffman, C.B. et al. (2002). Band gap fluorescence from individual single-walled carbon nanotubes. Science 297 (5581): 593–596.
- Roxbury, D., Jena, P.V., Williams, R.M. et al. (2015). Hyperspectral microscopy of near-infrared fluorescence enables 17-chirality carbon nanotube imaging. Scientific Reports 5: 14167.
- Shiraki, T., Shiraishi, T., Juhász, G. et al. (2016). Emergence of new red-shifted carbon nanotube photoluminescence based on proximal doped-site design. Scientific Reports 6: 28393.
- Murakami, Y., Chiashi, S., Miyauchi, Y. et al. (2004). Growth of vertically aligned single-walled carbon nanotube films on quartz substrates and their optical anisotropy. Chemical Physics Letters 385 (3–4): 298–303.
- Xie, L., Wang, G., Zhou, H. et al. (2016). Functional long circulating single walled carbon nanotubes for fluorescent/photoacoustic imaging-guided enhanced phototherapy. Biomaterials 103: 219–228.
- Heller, D.A., Baik, S., Eurell, T.E. et al. (2005). Single-walled carbon nanotube spectroscopy in live cells: towards long-term labels and optical sensors. Advanced Materials 17 (23): 2793–2799.
- Wang, L.V. and Yao, J. (2016). A practical guide to photoacoustic tomography in the life sciences. Nature Methods 13 (8): 627–638.
- Song, K.H. and Wang, L.V. (2007). Deep reflection-mode photoacoustic imaging of biological tissue. Journal of Biomedical Optics 12 (6): 060503. 1–3.
- De La Zerda, A., Zavaleta, C., Keren, S. et al. (2008). Carbon nanotubes as photoacoustic molecular imaging agents in living mice. Nature Nanotechnology 3 (9): 557–562.
- Pramanik, M., Song, K.H., Swierczewska, M. et al. (2009). In vivo carbon nanotube-enhanced non-invasive photoacoustic mapping of the sentinel lymph node. Physics in Medicine and Biology 54 (11): 3291.
- Lalwani, G., Cai, X., Nie, L. et al. (2013). Graphene-based contrast agents for photoacoustic and thermoacoustic tomography. Photoacoustics 1 (3–4): 62–67.
- Nie, L. and Chen, X. (2014). Structural and functional photoacoustic molecular tomography aided by emerging contrast agents. Chemical Society Reviews 43 (20): 7132–7170.
- Zhang, T., Cui, H., Fang, C.-Y. et al. (2013). Photoacoustic contrast imaging of biological tissues with nanodiamonds fabricated for high near-infrared absorbance. Journal of Biomedical Optics 18 (2): 026018–026018.
- Wharton, T. and Wilson, L.J. (2002). Highly-iodinated fullerene as a contrast agent for X-ray imaging. Bioorganic & Medicinal Chemistry 10 (11): 3545–3554.
- Waddington, D.E., Sarracanie, M., Zhang, H. et al. (2017). Nanodiamond-enhanced MRI via in situ hyperpolarization. Nature Communications 8.
- Manus, L.M., Mastarone, D.J., Waters, E.A. et al. (2009). Gd (III)-nanodiamond conjugates for MRI contrast enhancement. Nano letters 10 (2): 484–489.
- Hill, D.L., Batchelor, P.G., Holden, M. et al. (2001). Medical image registration. Physics in Medicine and Biology 46 (3): R1.
- Zurbuchen, M.A., Lake, M.P., Kohan, S.A. et al. (2013). Nanodiamond landmarks for subcellular multimodal optical and electron imaging. Scientific Reports 3.
-
Sochacki, K.A., Shtengel, G., Van Engelenburg, S.B.
et al. (2014). Correlative super-resolution fluorescence and metal-replica transmission electron microscopy. Nature Methods
11 (3): 305–308.
10.1038/nmeth.2816 Google Scholar
- De Boer, P., Hoogenboom, J.P., and Giepmans, B.N. (2015). Correlated light and electron microscopy: ultrastructure lights up! Nature Methods 12 (6): 503–513.
-
Yi, J., Manna, A., Barr, V.A.
et al. (2016). madSTORM: a superresolution technique for large-scale multiplexing at single-molecule accuracy. Molecular Biology of the Cell
27 (22): 3591–3600.
10.1091/mbc.E16-05-0330 Google Scholar
- Yang, S.-T., Cao, L., Luo, P.G. et al. (2009). Carbon dots for optical imaging in vivo. Journal of the American Chemical Society 131 (32): 11308–11309.
- Vaijayanthimala, V., Cheng, P.-Y., Yeh, S.-H. et al. (2012). The long-term stability and biocompatibility of fluorescent nanodiamond as an in vivo contrast agent. Biomaterials 33 (31): 7794–7802.
- Su, L.-J., Wu, M.-S., Hui, Y.Y. et al. (2017). Fluorescent nanodiamonds enable quantitative tracking of human mesenchymal stem cells in miniature pigs. Scientific Reports 7.
- Chow, E.K., Zhang, X.-Q., Chen, M. et al. (2011). Nanodiamond therapeutic delivery agents mediate enhanced chemoresistant tumor treatment. Science Translational Medicine 3 (73): 73ra21.
- Steinert, S., Ziem, F., Hall, L. et al. (2013). Magnetic spin imaging under ambient conditions with sub-cellular resolution. Nature Communications 4: 1607.
- Huang, B., Babcock, H., and Zhuang, X. (2010). Breaking the diffraction barrier: super-resolution imaging of cells. Cell 143 (7): 1047–1058.
- Diaspro, A. and van Zandvoort, M.A. (2016). Super-Resolution Imaging in Biomedicine . CRC Press.
- Betzig, E., Patterson, G.H., Sougrat, R. et al. (2006). Imaging intracellular fluorescent proteins at nanometer resolution. Science 313 (5793): 1642–1645.
- Hess, S.T., Girirajan, T.P., and Mason, M.D. (2006). Ultra-high resolution imaging by fluorescence photoactivation localization microscopy. Biophysical Journal 91 (11): 4258–4272.
- Rust, M.J., Bates, M., and Zhuang, X. (2006). Sub-diffraction-limit imaging by stochastic optical reconstruction microscopy (STORM). Nature Methods 3 (10): 793–796.
- Westphal, V. and Hell, S.W. (2005). Nanoscale resolution in the focal plane of an optical microscope. Physical Review Letters 94 (14): 143903.
- Gustafsson, M.G.L. (2005). Nonlinear structured-illumination microscopy: wide-field fluorescence imaging with theoretically unlimited resolution. Proceedings of the National Academy of Sciences of the United States of America 102 (37): 13081–13086.
- Gustafsson, M.G.L. (2000). Surpassing the lateral resolution limit by a factor of two using structured illumination microscopy. Journal of Microscopy 198 (2): 82–87.
- Li, D., Shao, L., Chen, B.-C. et al. (2015). Extended-resolution structured illumination imaging of endocytic and cytoskeletal dynamics. Science 349 (6251): aab3500.
-
Yang, X., Tzeng, Y.-K., Zhu, Z.
et al. (2014). Sub-diffraction imaging of nitrogen-vacancy centers in diamond by stimulated emission depletion and structured illumination. RSC Advances
4 (22): 11305–11310.
10.1039/c3ra47240j Google Scholar
-
Cuche, A., Sonnefraud, Y., Faklaris, O.
et al. (2009). Diamond nanoparticles as photoluminescent nanoprobes for biology and near-field optics. Journal of Luminescence
129 (12): 1475–1477.
10.1016/j.jlumin.2009.04.089 Google Scholar
- Hell, S.W. and Wichmann, J. (1994). Breaking the diffraction resolution limit by stimulated emission: stimulated-emission-depletion fluorescence microscopy. Optics Letters 19 (11): 780–782.
- Rittweger, E., Han, K.Y., Irvine, S.E. et al. (2009). STED microscopy reveals crystal colour centres with nanometric resolution. Nature Photonics 3: 144.
- Sun, M.G., Kopek B.G., Paez-Segala, M.G. et al. (2016). Diverse Protocols for Correlative Super-Resolution Fluorescence Imaging and Electron Microscopy of Cells and Tissue. USAMRIID Frederick United States.
-
Igarashi, R., Yoshinari, Y., Yokota, H.
et al. (2012). Real-time background-free selective imaging of fluorescent nanodiamonds in vivo. Nano Letters
12 (11): 5726–5732.
10.1021/nl302979d Google Scholar
- Tisler, J., Balasubramanian, G., Naydenov, B. et al. (2009). Fluorescence and spin properties of defects in single digit nanodiamonds. ACS Nano 3 (7): 1959–1965.
- Forster, L.S. (1976). Fluorescence lifetimes of biomolecules. Photochemistry and Photobiology 23 (6): 445–448.
-
Wu, T.-J., Tzeng, Y.-K., Chang, W.-W.
et al. (2013). Tracking the engraftment and regenerative capabilities of transplanted lung stem cells using fluorescent nanodiamonds. Nature Nanotechnology
8 (9): 682–689.
10.1038/nnano.2013.147 Google Scholar
- Zipfel, W.R., Williams, R.M., Christie, R. et al. (2003). Live tissue intrinsic emission microscopy using multiphoton-excited native fluorescence and second harmonic generation. Proceedings of the National Academy of Sciences 100 (12): 7075–7080.
-
Smith, K.C. (1991). The photobiological basis of low level laser radiation therapy. Laser Therapy
3 (1): 19–24.
10.5978/islsm.91-OR-03 Google Scholar
- Hong, G., Lee, J.C., Robinson, J.T. et al. (2012). Multifunctional in vivo vascular imaging using near-infrared II fluorescence. Nature Medicine 18 (12): 1841–1846.
- Hong, G., Diao, S., Chang, J. et al. (2014). Through-skull fluorescence imaging of the brain in a new near-infrared window. Nature Photonics 8 (9): 723–730.
- Bruns, O.T., Bischof, T.S., Harris, D.K. et al. (2017). Next-generation in vivo optical imaging with short-wave infrared quantum dots. Nature Biomedical Engineering 1: 0056.
- Kairdolf, B.A., Smith, A.M., Stokes, T.H. et al. (2013). Semiconductor quantum dots for bioimaging and biodiagnostic applications. Annual Review of Analytical Chemistry 6: 143–162.
- Lam, C.-W., James, J.T., McCluskey, R. et al. (2004). Pulmonary toxicity of single-wall carbon nanotubes in mice 7 and 90 days after intratracheal instillation. Toxicological Sciences 77 (1): 126–134.
- Pulskamp, K., Diabaté, S., and Krug, H.F. (2007). Carbon nanotubes show no sign of acute toxicity but induce intracellular reactive oxygen species in dependence on contaminants. Toxicology Letters 168 (1): 58–74.
- Liu, Q., Guo, B., Rao, Z. et al. (2013). Strong two-photon-induced fluorescence from photostable, biocompatible nitrogen-doped graphene quantum dots for cellular and deep-tissue imaging. Nano Letters 13 (6): 2436–2441.
- Kong, B., Zhu, A., Ding, C. et al. (2012). Carbon dot-based inorganic–organic nanosystem for two-photon imaging and biosensing of pH variation in living cells and tissues. Advanced Materials 24 (43): 5844–5848.
- Denk, W., Strickler, J.H., and Webb, W.W. (1990). Two-photon laser scanning fluorescence microscopy. Science 248 (4951): 73–76.
- Zavaleta, C., De La Zerda, A., Liu, Z. et al. (2008). Noninvasive Raman spectroscopy in living mice for evaluation of tumor targeting with carbon nanotubes. Nano Letters 8 (9): 2800–2805.
- Keren, S., Zavaleta, C., Cheng, Z. et al. (2008). Noninvasive molecular imaging of small living subjects using Raman spectroscopy. Proceedings of the National Academy of Sciences 105 (15): 5844–5849.
- Liu, Z., Tabakman, S., Sherlock, S. et al. (2010). Multiplexed five-color molecular imaging of cancer cells and tumor tissues with carbon nanotube Raman tags in the near-infrared. Nano Research 3 (3): 222–233.
- Jorio, A., Saito, R., Dresselhaus, G. et al. (2004). Determination of nanotubes properties by Raman spectroscopy. Philosophical Transactions of the Royal Society of London A: Mathematical, Physical and Engineering Sciences 362 (1824): 2311–2336.
- Jung, Y., Slipchenko, M.N., Liu, C.H. et al. (2010). Fast detection of the metallic state of individual single-walled carbon nanotubes using a transient-absorption optical microscope. Physical Review Letters 105 (21): 217401.
- Tong, L., Liu, Y., Dolash, B.D. et al. (2012). Label-free imaging of semiconducting and metallic carbon nanotubes in cells and mice using transient absorption microscopy. Nature Nanotechnology 7 (1): 56–61.
- Krawczynski, K., Beach, M.J., Bradley, D.W. et al. (1992). Hepatitis C virus antigen in hepatocytes: immunomorphologic detection and identification. Gastroenterology 103 (2): 622–629.