Micro bubbles in cancer treatment

Treating cancer is still a medical mystery to doctors and scientists. But little by little, science combats the complex problems of treatment.

Dr. Mark Bordon, discussed the use of micro bubbles in detecting and evaluating tumors in cancer patients. In his talk, “Contrast Enhanced Ultrasound for Monitoring Tumor Response to Therapy,“ sponsored by Shell, Borden shows how this technology has recently become more advanced and easier to use in the human body.

Micro bubbles are so small that they can go through the blood stream without causing harm to even the smallest capillaries. Borden explained how they can be created artificially. “There’s a little transducer that’s hitting the surface… that produces capillary waves, those waves will then grow and become unstable and pinch off large bubbles into the aqueous medium.” The bubbles created are larger than can be safely used in the body but, Borden said, “Luckily, we also have capitation going on inside the fluid.” The capitation eventually breaks the larger bubbles into a size small enough for injection.

So how can bubbles help doctors fight cancer? Micro bubbles could provide an easy way to monitor the development of tumors. Borden said, “There’s a big push right now to find better ways to diagnose whether or not the therapy is working earlier on.”

For example, this is important when using anti-VGEF therapy. Anti-VGEF is a common treatment for certain types of cancer. In this method, a blockade cuts off blood flow to the tumor. This works for some tumors, but others can just take the blood they need from other sources. If the patient has the latter type of tumor, then, “If the tumor is co-opting blood vessels that are already there, you’re wasting a lot of time, money, and energy,” said Borden.

Micro bubbles allow tumors to show up in ultrasounds because the bubbles will bind to the tumor and resonate at a known frequency to produce the image. The problem is that the bubbles need to be broken in order to get them to bind with the tumor. Borden explained, “That can change the phenotype. Clearly, that might have a mechanical response in the cell… Therefore you might be changing the underlying physiology that you’re trying to detect. Molecular imaging should be purely detection; it should be a non-destructive testing.”
To make ultrasound imaging more effective, Borden’s team looked for “a way to engineer the surface of the bubble that will allow us to circumvent some of those problems.” They chose to approach the situation by burying the ligand of the bubble beneath its surface. This is the part that actually causes the interaction of the bubble and tumor. Although the ligand is essential to binding to the tumor for detection, “It is also a beacon telling your body that this is a foreign particle it has to remove.”

The hidden ligand allows the micro bubbles to serve their function better, but then how will the bubbles bind with the tumor? A specific frequency is used to resonate the bubbles. This causes the bubbles to expand and contract and on the expansion the boundary thins enough to expose the ligand to binding. Borden said, “You can get to the binding when you want to.” This technology gives doctors much more control over image.