Usually, doctors aim to improve the wellbeing of these patients by injecting their tumour with light-sensitive drugs, and then bathing the tumour with a beam of light. This is a non-invasive technique, known as photodynamic therapy, which works by activating the drugs with the secondary beam of light. However, as visible light cannot penetrate more than about 2cm into the tissue, tumours with much of their mass below the skin’s surface, like an iceberg, cannot be fully reached with this method.
Hence, Associate Professor Zhang Yong of the engineering school’s bioengineering department and his colleagues have developed nanoparticles that can capture a different kind of light and use it to activate drugs injected deeper down. Using near-infrared light, the bioengineers found that nanoparticles injected into the tumours of mice gave off a visible, fluorescent light, which activated the drugs around them. This is because infrared light has longer wavelengths and can penetrate deeper into body tissue than visible light. The researchers have proved that the method works in mice, inhibiting the growth of their tumours.
Professor Zhang, who first worked on such light-converting nanoparticles six years ago, commented that the technique is best suited to specific types of cancers, such as skin cancer and some oral and nose cancers. He said, ‘We are not saying it is a replacement for chemotherapy. It is an improvement on current photodynamic therapy.’ The professor, who was trained at Zhejiang University as a materials scientist, added that scientists elsewhere are studying the use of drug-infused nanoparticles to directly target tumours, but current drug-targeting is not yet as precise as a focused beam of light.
Working with the National Cancer Centre Singapore, the researchers are now looking to test the safety and level of toxicity in these nanoparticles, which will hopefully set the stage for pilot clinical trials on humans in the next two to three years. There could potentially be other applications for the nanoparticles, which includes anything from bioimaging to faster detection and diagnosis of infectious disease.