Killing Cancer With Bubbles

Source: www.ox.ac.uk

By Naomi Canton

Bubbles are never far from hand — in the bath, at the bottom of your glass of champagne or, sadly, even in the washing up bowl. But while they might seem simple things, they’ve started to play a pivotal role in the treatment of cancer, thanks to pioneering work like that being carried out at Oxford.

Researchers at the Biomedical Ultrasonics, Biotherapy & Biopharmaceuticals Laboratory (BUBBL), based at the Institute of Biomedical Engineering in Headington, are busy studying bubbles to work out how they can take advantage of their physical properties and make a real medical impact. While it might sound fanciful, it’s already helping rid patients of cancer.

Currently, drugs used in chemotherapy treatments for cancer are simply injected into a patient’s bloodstream, meaning they can travel throughout the entire body, killing not just cancerous cells but healthy ones, too. That’s why patients undergoing the therapy suffer severe side effects, like nausea and hair loss. So the team at BUBBL are manufacturing microbubbles specifically designed to carry drugs within them, which burst once they reach their target — delivering the pharmaceuticals to a specific point in order to mitigate damage.

“Chemotherapy uses what amount to crude poisons to destroy cells,” explains Dr Eleanor Stride, University Lecturer at the Institute of Biomedical Engineering. “With bubbles you don’t release the poison until it reaches the target site, which reduces the harmful side effects.”

Putting bubbles into the body may strike you as strange; after all, air injected into the vein was a popular murder weapon in 1930s novels, and tiny bubbles in the blood are associated with decompression sickness in scuba divers. But the bubbles being engineered at BUBBL are much smaller — at less than ten micrometres in diameter, just a fraction of the width of a human hair — so they travel safely through human blood vessels. They’re even coated to prevent them sticking together and forming dangerous clumps.

Once the bubbles are injected, some find their way to the tumour that’s being treated. Then, a burst of high intensity ultrasound — sound with such a high frequency that humans can’t hear it — can be focussed, from outside the body, on the site. In turn, the pressure exerted by the sound encourages the bubbles to stick to the cancerous cells.

When enough of the drug-containing bubbles have reached the site of the tumour, the intensity of the ultrasound can be increased further, causing the bubbles to collapse in on themselves — in the process releasing the drugs to exactly where they’re required. Fortunately bubbles show up extremely well in ultrasound images, allowing the treatment to be carried out with amazing levels of precision.

Now, Stride’s team is perfecting the bubbles to make them as detectable as possible, and developing molecules to help bind them to cancer cells. As the team continues to improve the design, their effectiveness will increase — and the hope is that the bubbles could be licensed to a pharmaceutical company in five years’ time if current testing is successful.

But it’s not just injecting bubbles into the body that can help in the fight against cancer. Even aiming high-intensity focused ultrasound alone at a tumour can create bubbles in living tissue, which can then be used to destroy cancerous growths.

A transducer — the device which creates the sound beam — can send a high frequency sound wave into the body, creating pressures at the focus capable of causing spontaneous formation of bubbles. As the pressure is quickly varied, those bubbles expand and contract rapidly, and their motion creates such large increases in temperature that a section of cancerous tissue about the size of a grain of rice is effectively cooked and killed. By repeating that process it’s possible to destroy entire tumours — without ever cutting a patient open.

“It gives patients the option of having a tumour removed as a day patient without the need for surgery and scars,” explains Constantin-C. Coussios, Professor of Biomedical Engineering at the University Oxford. “Currently it is offered as a private option but we hope it becomes standard NHS treatment. The technology is still quite immature but could potentially help tens of thousands of patients.” His prediction seems likely: the technique’s already been used to treat thousands of cases of prostate cancer across the world, and is increasingly being used on other kinds of tumours, too.

It’s not difficult to see the appeal of the treatments being developed by the academics at BUBBL. Fighting cancer without the need for debilitating chemotherapy or invasive surgery is impossible to resist, and that’s exactly what their work is providing. Quite a feat for a humble bubble.