STANFORD UNIVERSITY, CALIFORNIA, USA. Researchers have found a way to detect cancer without the high cost of MRI and CT scan by using a carbon nanotube contrast agent for photo-acoustic imaging.

Photo acoustic imaging is a medical imaging modality that is non-invasive, cheaper and safer than the conventional imaging modalities currently used to visualize tumors inside the body. Near Infrared light is first directed into the area of skin in order to heat up the underlying tissue and blood to produce expansion. When tissue expands, it produces ultrasonic waves which can be picked up by an ultrasound detector and generate a 2D or 3D image of the area of interest. Hemoglobin, which absorbs huge amounts of near-infrared light, makes blood produce stronger photoacoustic signals that any other tissue. This makes the modality very useful in the detection of bleeding and of cancer tumors.

What Sanjiv Gambhir and the research team created is a photoacoustic contrast agent that can bind into cancer tumor blood vessels. Using gold nanoparticles, dye that enhances light absorption was attached to the carbon nanotubes. Maleimide-containing linker molecules were used to tag the nanotubes with a peptide which can bind into a protein on tumor blood vessels to visualize them. This was then tested on mice with artificial brain tumors under the skin of their flanks. Usage of peptide-tagged contrast agents produced two to three times increased photo acoustic signals.

The research has the potential to increase the accuracy of diagnosis of physicians through modifying carbon nanotubes. Different molecules that attach to different cancer specific proteins can increase this. Another manipulation is to attach drugs into these nanotubes to create both a diagnostic and therapeutic imaging modality.