Imaging tumours

A material developed at Virginia University has been shown to simplify the imaging of oxygen-deficient regions of tumours.

The material is based on polylactic acid, a biodegradable polymer that is safe for the body and the environment, which is easy and inexpensive to fabricate in many forms, including films, fibres and nanoparticles.

Chemists at Virginia University developed the material and consulted with cancer researchers at the Virginia University Cancer Center and the Duke University Medical Center to determine possible applications.

Guoqing Zhang, a Virginia University chemistry doctoral candidate, working with Cassandra Fraser, a Virginia University chemistry professor, synthesised the material by combining a corn-based biopolymer with a dye that is both fluorescent and phosphorescent.

The phosphorescence appears as a long-lived afterglow that is only evident under low-oxygen or oxygen-free conditions at room or body temperature, making it ideal for use in tissues.

Fraser said: 'We were amazed at how easy the material was to synthesise and fabricate as films and nanoparticles and how useful it is for measuring low oxygen concentrations.'

Cancer researchers at Duke University Medical Center quickly realised that the material could be particularly useful for the real-time and extended-time spatial mapping of oxygen levels in tumours.

Greg Palmer, assistant professor of radiation oncology at Duke University Medical Center, said: 'This technology will enable us to better characterise the influence of tumour hypoxia [a lack of sufficient oxygen in tumours] on tumour growth.'

Researchers and clinicians have long sought effective ways to locate and map low-oxygen areas in the body to better understand disease processes. Presently, there are no simple, easy or inexpensive methods for generating oxygen maps of tumours and surrounding tissues with good spatial and temporal resolution.

Michael Weber, director of Virginia University's Cancer Center, said: 'Tumours that have insufficient oxygen tend to be more likely to spread from the primary site to other parts of the body. Despite the overall importance of tumour hypoxia, it is very difficult to measure directly and most methods that are available are very expensive.'

The material is currently being used in pre-clinical studies to gain insight into cancer biology and treatment response, which could be useful for drug development and testing. Eventually, the material could be used as an injectable nanosensor, potentially providing continual data on oxygen levels, biological processes and therapy responsiveness.