Scientists at Nanyang Technological University (NTU Singapore) have invented a new way to direct cancer drugs deep into tumour cells.
The scientists create micro-sized gas bubbles coated with cancer drug particles and iron oxide nanoparticles, and then use magnets to direct them to gather around a specific tumour.
Ultrasound is then used to vibrate the microbubbles, providing the energy to direct the drug particles into a targeted area.
This innovative technique was developed by a multidisciplinary team of scientists, led by Assistant Professor Xu Chenjie from the School of Chemical and Biomedical Engineering and Associate Professor Claus-Dieter Ohl from the School of Physical and Mathematical Sciences.
NTU’s microbubbles were tested in mice and the study has been published in Asia Materials.
Xu, who is also a researcher at the NTU-Northwestern Institute for Nanomedicine, said the team's new method may solve some of the most pressing problems faced in chemotherapy used to treat cancer.
The first unique characteristic of our microbubbles is that they are magnetic
The main issue is that current chemotherapy drugs are largely non-targeted. The drug particles flow in the bloodstream, damaging both healthy and cancerous cells. Typically, these drugs are flushed away quickly in organs such as the lungs and liver, limiting their effectiveness.
The remaining drugs are also unable to penetrate deep into the core of the tumour, leaving some cancer cells alive, which could lead to a resurgence in tumour growth.
'The first unique characteristic of our microbubbles is that they are magnetic. After injecting them into the bloodstream, we are able to gather them around the tumour using magnets and ensure that they don’t kill the healthy cells,' said Xu, who has been working on cancer diagnosis and drug delivery systems since 2004.
'More important, our invention is the first of its kind that allows drug particles to be directed deep into a tumour in a few milliseconds. They can penetrate a depth of 50 cell layers or more – which is about 200 micrometres, twice the width of a human hair. This helps to ensure that the drugs can reach the cancer cells on the surface and also inside the core of the tumour.'
If NTU’s technology proves to be viable, clinicians might be able to localise and concentrate the anticancer drugs around a tumour, and introduce the drugs deep into tumour tissues in just a few seconds using a clinical ultrasound system.
The motivation for this research is to find alternative solutions for drug delivery systems that are non-invasive and safe.
Ultrasound uses soundwaves with frequencies higher than those heard by the human ear. It is commonly used for medical imaging to obtain diagnostic images.
Magnets, which can draw and attract the microbubbles, are already in use in diagnostic machines such the Magnetic Resonance Imaging (MRI).
'We are looking at developing novel drug carriers – essentially better ways of delivering drugs with minimum side effects,' explained Ohl, an expert in biophysics.
'Most prototype drug delivery systems on the market face three main challenges before they can be commercially successful: they have to be non-invasive, patient-friendly and yet cost-effective.
'Using the theory of microbubbles and how their surface vibrates under ultrasound, we were able to come up with our solution that addresses these three challenges.'
This study, which took two-and-a-half years, involved a 12-man international interdisciplinary team consisting of NTU scientists as well as researchers from City University of Hong Kong and Tel Aviv University in Israel.
Moving forward, the team will be adopting this new drug delivery system in studies on lung and liver cancer using animal models, and eventually clinical studies.
They estimate that it will take another eight to 10 years before it reaches human clinical trials.