PA imaging avoids radiation by using near-infrared light to excite contrast molecules, which emit sound waves. These waves are detected and processed to create detailed images of tumours in the body
Published Jun 15, 2025 | 7:00 AM ⚊ Updated Jun 15, 2025 | 9:35 AM
From left to right: Pooja Patkulkar, Sanhita Sinharay, and Arjun SV. Credit: Ankita Mandal
Synopsis: Scientists at IISc have developed GPc, a new biocompatible imaging molecule for Photoacoustic Tomography, offering a safer, radiation-free alternative to PET scans. The technique uses light and sound to produce high-contrast 3D tumour images, particularly near the body’s surface. Published in JACS Au, the study highlights the method’s affordability and potential to transform cancer diagnosis in low-resource settings.
Scientists at IISc have developed a new imaging molecule that can help detect tumours more safely and cheaply — without using radiation. The researchers claim that this new method could one day replace expensive PET scans and make cancer diagnosis more accessible, especially in low-resource settings.
The new study, published in JACS Au, introduces GPc, a biocompatible molecule tailored for Photoacoustic (PA) Tomography – a promising imaging technique that uses light and sound to create high-contrast 3D images of tumours, especially those near the body’s surface.
“You are able to use a more cost-effective technique, cheaper than both PET and MRI, and get the same information,” said Sanhita Sinharay, Assistant Professor at the Department of Bioengineering (BE), IISc, and corresponding author of the study in a statement from IISc to the media.
Today, Positron Emission Tomography (PET) is the gold standard in detecting tumours, which consume more glucose than healthy cells.
PET scans involve injecting radioactive glucose tracers like 18F-FDG, which accumulate at tumour sites and light them up during imaging. But PET is expensive, and more importantly, poses radiation risks, especially in patients requiring repeated scans for cancer monitoring.
PA imaging, the technique used in the new study, avoids radiation altogether. It uses near-infrared (NIR) light to excite contrast molecules in the body. These molecules then emit sound waves, which are detected and used to construct tumour images.
Until now, PA imaging in a clinical setting has been limited to natural chromophores already present in the body, like haemoglobin. The IISc team’s breakthrough was designing an external molecule – GPc – to dramatically enhance sensitivity and contrast, making tumour detection easier.
In the new study, the IISc team designed an external molecule–not typically found in human cells–to provide better sensitivity and contrast, which makes it easier to differentiate the target region from normal tissues. “The molecule, referred to as GPc, consists of four glucose units conjugated to a scaffold made of zinc-phthlocyanine,”
“The strength of our work was proving to some extent the behaviour of the probe inside cells and validating its entry into the tumour core” said which exhibits a low gradient of molecular oxygen supply,” said Sinharay.
Once it enters the tumour, we wanted to check “how is it functioning? How close is the behaviour to F-FDG? Even though the structure and molecular weight are different, their functionality is very close. That was really surprising,” Sinharay added.
GPc is a compound made from zinc-phthalocyanine, a chemical well-suited for NIR-based imaging, and four glucose units attached to it. The glucose tags enhance both water solubility and cellular uptake, helping the molecule reach tumour sites more effectively.
The team ensured GPc wouldn’t interfere with the body’s natural glucose pathways. “We wanted to see whether the molecule we made was being taken up by the glucose transporters, and what its fate was after uptake,” explained Pooja Patkulkar, a PhD student at IISc and first author of the study. Using a “seahorse assay” and other biochemical tests, they confirmed that GPc is not metabolised and doesn’t compete with glucose, making it an ideal diagnostic tool.
The implications for cancer patients – especially in low-resource settings – are profound:
No radiation exposure, unlike PET scans
Lower costs, making tumour imaging more accessible
Potential for repeat scans without health risks
Better imaging of superficial tumours, such as those in the breast, skin, or lymph nodes
According to the IISc statement, “The use of such molecules can greatly help visualise ntumour sites with high metabolic activity non-invasively… providing similar functionality at a lower cost.”
While early lab studies show promise, further research and clinical trials are needed to establish the molecule’s behaviour in human patients across tumour types. If validated, GPc could be a game-changer in non-invasive cancer diagnostics, especially for countries like India where PET access is limited.
(Edited by Ananya Rao)
