New Imaging Probe Lights Up Brain Tumors

Non-invasive Visualization of Tumor Cells

Despite being a small molecular probe, FA-ICG achieves big results. It combines a naturally occurring long-chain fatty acid (FA) with indocyanine green (ICG), a fluorescent dye with both excitation and emission spectra in the near-infrared (NIR) range.

ICG is already used in clinical medicine for retinal disease diagnostics, cardiac output measurement, liver function testing, and sentinel lymph node detection in oncologic surgery. Fatty acids serve as a key energy source for many proliferating tumor cells, and their metabolism plays an important role in glioblastoma progression.

Abnormal fatty acid uptake by tumor cells could thus be utilized for both diagnostics and therapy of malignancies. The ability to visualize elevated fatty acid uptake could enable real-time intraoperative visualization of tumor boundaries—especially crucial in glioblastoma surgery, where maximal tumor removal must be balanced with minimal damage to surrounding brain tissue.

The FA-ICG Probe

The FA-ICG probe uses palmitic acid. Its emission spectrum peaks at 820 nm, making it compatible with most surgical microscopes and intraoperative cameras.

Researchers first confirmed that FA-ICG uptake mirrors natural fatty acid uptake in fibroblasts, adipocytes, and various cancer cell lines. Glioblastoma cells were found to take up FA-ICG in especially high concentrations.

They validated these findings in orthotopic glioblastoma models, demonstrating increased FA-ICG uptake and retention over time, compared to ICG. The probe was also effective in patient-derived xenograft (PDX) glioblastoma models.

The results showed that FA-ICG combines the benefits of NIR imaging—high sensitivity, low autofluorescence, and deep tissue penetration—with specific targeting of tumor cells (based on their metabolism) and strong retention. FA-ICG is a promising candidate for metabolic intraoperative imaging in cancer surgery and could aid in the treatment of glioblastoma and other solid tumors.

Advantages for Intraoperative Imaging

Various navigational tools are used during brain tumor surgery, including microscopes, ultrasound, and fluorescent dyes.

Currently, the only approved fluorescent dye for glioblastoma surgery is 5-aminolevulinic acid (5-ALA), which fluoresces under blue light. However, 5-ALA has drawbacks: the operating room must be darkened, tissue penetration is shallow, and fluorescence signals can be weak and non-specific. Side effects are also possible.

By contrast, FA-ICG is brighter, works under standard surgical lighting, and allows real-time microscopic visualization—no need to turn off the lights mid-surgery. Its higher signal-to-background ratio improves the distinction between tumor and healthy tissue.

Prof. Michael Chicoine, a neurosurgeon at the University of Missouri, noted that FA-ICG could unify current approaches—used directly during surgery—while reserving costly, time-consuming MRI scans for postoperative checks. Post-radiation or chemotherapy, distinguishing scar tissue from active tumor can be difficult. FA-ICG may help clarify such decisions and guide further treatment.

Another promising application is photodynamic therapy during or after surgery. Since the dye has light-activated properties that can kill cancer cells, researchers are exploring its potential as a therapeutic tool as well.

How Well Is the Probe Tolerated?

The next step is to evaluate how patients tolerate FA-ICG—whether any side effects emerge at effective doses. Comparative studies with existing tools are also essential.

If results remain favorable, FA-ICG may one day be used to detect other tumors with high fatty acid metabolism, such as pancreatic cancer.

Editorial Team, Medscope.pro

Sources:

1. Ali M, Khodakivskyi P, Ntafoulis I, et al. Near-infrared fatty acid molecular probe for image-guided surgery of glioblastoma. Npj Imaging 2025 Jun 23; 3(1): 28, doi: 10.1038/s44303-025-00077-z.

2. Fountain DM, Bryant A, Barone DG, et al. Intraoperative imaging technology to maximise extent of resection for glioma: a network meta-analysis. Cochrane Database Syst Rev 2021 Jan 4; 1(1): CD013630, doi: 10.1002/14651858.CD013630.pub2.