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Preparation of carbon nanotube bioconjugates for biomedical applications


Biomedical applications of carbon nanotubes have attracted much attention in recent years. Here, we summarize our previously developed protocols for functionalization and bioconjugation of single-walled carbon nanotubes (SWNTs) for various biomedical applications including biological imaging; using nanotubes as Raman, photoluminescence and photoacoustic labels; sensing using nanotubes as Raman tags and drug delivery. Sonication of SWNTs in solutions of phospholipid-polyethylene glycol (PL-PEG) is our most commonly used protocol of SWNT functionalization. Compared with other frequently used covalent strategies, our non-covalent functionalization protocol largely retains the intrinsic optical properties of SWNTs, which are useful in various biological imaging and sensing applications. Functionalized SWNTs are conjugated with targeting ligands, including peptides and antibodies for specific cell labeling in vitro or tumor targeting in vivo. Radio labels are introduced for tracking and imaging of SWNTs in real time in vivo. Moreover, SWNTs can be conjugated with small interfering RNA (siRNA) or loaded with chemotherapy drugs for drug delivery. These procedures take various times ranging from 1 to 5 d.

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Figure 1: Overview of the protocol.
Figure 2: A scheme showing conjugation of targeting ligands to SWNTs.
Figure 3: A scheme showing radiolabeling of targeting SWNT bioconjugates.
Figure 4: A scheme showing siRNA conjugation to SWNTs through a disulfide bond.
Figure 5: Functionalization of SWNTs by PL-PEG.
Figure 6: Targeting SWNT bioconjugates for cell labeling and Raman imaging.
Figure 7: Radiolabeled SWNTs for in vivo PET imaging and tumor targeting radiolabeled nanotubes.
Figure 8: CXCR4 expression levels on CEM.NKR cells after various treatments.
Figure 9: Doxorubicin (DOX) on functionalized SWNTs for drug delivery.


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The multiple projects involved here were supported by a Stanford Graduate Fellowship, a Stanford Bio-X grant, CCNE-TR at Stanford University, NIH-NCI R01 CA135109-02 and Ensysce Biosciences Inc. Drs Nadine Wong Shi Kam, Sarunya Bangsaruntip, Xiaowu Tang, Xiaoming Sun, Xiaoyuan Chen, Weibo Cai and Ms Nozomi Nakayama have also contributed in the development of this protocol.

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Z.L. and H.D. designed and wrote this paper. S.M.T. and Z.C. revised the paper.

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Correspondence to Zhuo Chen or Hongjie Dai.

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Liu, Z., Tabakman, S., Chen, Z. et al. Preparation of carbon nanotube bioconjugates for biomedical applications. Nat Protoc 4, 1372–1381 (2009).

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