Editors' ChoiceNanomedicine

Nanotubes Hunt Down Tumors, Spare Others

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Science Translational Medicine  23 Oct 2013:
Vol. 5, Issue 208, pp. 208ec174
DOI: 10.1126/scitranslmed.3007769

Maximum efficacy with precise targeting and no collateral damage to healthy cells is the Holy Grail of cancer therapy. To this end, Mulvey et al. used carbon nanotubes in a two-step method to deliver a dense therapeutic cargo to the tumor site. Their method encouraged rapid removal of unbound nanotubes from the body, which reduced potential side effects.

Rather than concocting a “one-stop shop,” the authors kept the tumor-targeting and therapeutic-delivery steps separate. In their scheme, an antibody modified with an oligonucleotide tag stuck to the tumor via a surface antigen. Then, a single-walled carbon nanotube (SWCNT) modified with the complementary oligonucleotide bound to the immobilized antibody-oligonucleotide complex. The functional SWCNT carried a drug and/or an imaging agent. The decoupling of targeting and delivery steps took advantage of the fact that despite the large size, SWCNTs are cleared rapidly via the kidneys. They could therefore carry large therapeutic loads, owing to their high surface area, but have minimal toxicity. In contrast, antibodies are typically cleared very slowly from the body, if at all. In a mouse model of human lymphoma, the two-step approach significantly reduced animal mortality when actinium radioisotope–conjugated SWNT was delivered as compared with free isotopes or pre-annealed antibody-SWNT complexes. The authors also evaluated the therapeutic potential of this method by implanting mice with Daudi lymphoma cells in the peritoneal cavity. Delivery of the radioisotope reduced tumor size in a dose-dependent manner, whereas single-step delivery or saline controls led to transient or no therapeutic response.

Overall, this approach—largely enabled by particular properties at nanoscale—is promising for human cancer treatment without the nasty side effects. However, before it is ready for clinical use, the cargo concentration, surface properties of SWCNTs, and delivery timing need careful optimization.

J. J. Mulvey et al., Self-assembly of carbon nanotubes and antibodies on tumours for targeted amplified delivery. Nat. Nanotechnol., published online 29 September 2013 (10.1038/nnano.2013.190). [PubMed]

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