Carbon Nano-tubes Targetting Tumor [Cancerous] Cells

Medical imaging represents one of the most used and useful procedures in the oncologist’s diagnostic toolkit, even though each of the most useful techniques—magnetic resonance imaging (MRI), computerized tomography x-ray imaging (CT), and positron emission tomography (PET) scanning—has its own set of limitations. The companies that make imaging instruments have responded by developing so-called dual-modality machines that can simultaneously perform two different types of scans. Now two reports in the scientific literature show how nanotechnology researchers have responded by creating dual-modality contrast agents for future use with these next-generation imaging devices.

Doctor’s first created a magnetic nano-particle from manganese and iron and coated it with albumin, the most common protein in blood; this nano-particle produces a very strong signal in an MRI (Magnetic resonance Imaging). Next, the researchers added PET functionality by chemically attaching radioactive iodine to the albumin coating. They then showed the value of combining MRI and PET contrast agents in the same nano-particle in a simple experiment that compared the spatial resolution—how small an object they could image accurately—and the sensitivity—how little they could see—of each modality when using the same dual-modality nano-particle. The spatial resolution in the MRI was far greater than that measured in the PET image, and PET imaging was able to detect far less material.

Platinum-based anticancer agents have a long history as proven therapeutic agents, but their toxicity and short lifetime in the body and the ability of tumors to develop resistance to these drugs limit the ultimate utility of these agents. In an attempt to overcome these limitations, a multi-institutional research team comprising some members targeted carbon nano-tubes as delivery agents for an inactive form of platinum that cancer cells themselves convert into a toxic anticancer agent.

When administered to tumor cells that over express a folic acid receptor, the modified nano-tubes rapidly enter the target cell. There, enzymes within the cell convert platinum-IV to a far more toxic form known as platinum-II. This chemical conversion has the effect of releasing platinum from the nano-tube and enabling it to travel to the cell nucleus, where it reacts with deoxyribonucleic acid (DNA) and eventually kills the cell. Tests with cancer cells growing in culture showed that this nano-tube formulation of platinum is more than 8 times more potent than the approved anticancer agent cisplatin.