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Researchers at the University of Toronto have successfully converted microbubbles into nanoparticles that stay trapped in tumours to potentially deliver targeted, therapeutic payloads.

The discovery, published online March 30, 2015 in , details how Professor Gang Zheng and his research team created a new type of microbubble using a compound called porphyrin – a naturally occurring pigment in nature that harvests light.

In the lab in pre-clinical experiments, the team used low-frequency ultrasound to burst the porphyrin containing bubbles and observed that they fragmented into nanoparticles. Most importantly, the nanoparticles stayed within the tumour and could be tracked using imaging.

“Our work provides the first evidence that the microbubble reforms into nanoparticles after bursting and that it also retains its intrinsic imaging properties,” says Zheng, a professor of medical biophysics at �鶹��Ƶ. “We have identified a new mechanism for the delivery of nanoparticles to tumours, potentially overcoming one of the biggest translational challenges of cancer nanotechnology. In addition, we have demonstrated that imaging can be used to validate and track the delivery mechanism." 

Conventional microbubbles lose all intrinsic imaging and therapeutic properties once they burst, he says, in a blink-of-an-eye process that takes only a minute or so after bubbles are infused into the bloodstream.

“For clinicians, harnessing microbubble-to-nanoparticle conversion may be a powerful new tool that enhances drug delivery to tumours, prolongs tumour visualization and enables them to treat cancerous tumours with greater precision,” says Zheng, a senior scientist at the Princess Margaret Cancer Centre. 

For the past decade, Zheng’s research focus has been on finding novel ways to use heat, light and sound to advance multi-modality imaging and create unique, organic nanoparticle delivery platforms capable of transporting cancer therapeutics directly to tumours.

The research was funded by the Canadian Institutes of Health Research (CIHR) Frederick Banting and Charles Best Canada Graduate Scholarship, the Emerging Team Grant on Regenerative Medicine and Nanomedicine co-funded by the CIHR and the Canadian Space Agency, the Natural Sciences and Engineering Research Council of Canada, the Ontario Institute for Cancer Research, the International Collaborative R&D Project of the Ministry of Knowledge Economy, South Korea, the Joey and Toby Tanenbaum/Brazilian Ball Chair in Prostate Cancer Research, the Canada Foundation for Innovation and The Princess Margaret Cancer Foundation.