Role of polyethylene glycol integrity in specific receptor targeting of carbon nanotubes to cancer cells.

We demonstrate that dispersion of single walled carbon nanotubes (SWNTs) by ultrasonication with phospholipid-polyethylene glycol (PL-PEG) fragments it, thus interfering with its ability to block nonspecific uptake by cells. However, unfragmented PL-PEG promoted specific cellular uptake of targeted SWNTs to two distinct classes of receptors expressed by cancer cells. Since fragmentation is a likely consequence of ultrasonication, a technique commonly used to disperse SWNTs, this maybe a concern for certain applications such as drug delivery.