The prognosis for a cancer patient who undergoes surgery is better if the surgeon removes all of the tumour, but it can be hard to tell where a tumour ends and healthy tissue begins.

Now, scientists report in ACS Sensors that they have developed a fluorescent spray that specifically lights up cancerous tissue so it can be identified readily and removed during surgery.

Surgeons often use sight and touch to identify cancerous tissue, but this approach can miss small tumours, as well as diseased cells at the margins between a tumour and healthy tissue.

Fluorescence-guided surgery is an emerging technology that could enhance this difference.

The method relies on fluorescent probes that target cancerous tissue and heighten its visibility.

But some of these compounds must be administered many hours or days before surgery —sometimes necessitating a long hospital stay — and they might not reveal tiny tumours.

In addition, these compounds can require a large dose if they’re injected, or a washing step to get rid of excess dye if they’re applied to the tumour site.

So Ching-Hsuan Tung and colleagues set out to develop a fluorescent probe to rapidly visualise diseased tissue, even on a small scale, when sprayed on a surgical site or injected.

The researchers started with a compound they had previously designed that remains nearly invisible at the neutral pH of healthy tissue, but fluoresces brightly in the near-infrared range in the acidic environment of tumours.

That initial compound linked a pH-sensitive amino group with a cyanine fluorophore.

It worked when injected, but didn’t produce a signal when applied as a spray, so the team replaced some of its methyl groups with isopropyl groups.

That made the new compound more responsive to the acidic tumour environment.

When sprayed, it delineated tumour edges in mice within minutes, without the need for washing.

And when injected in the abdomen of mice, it illuminated ovarian tumours as small as 1 mm in diameter in an hour.

The researchers say the compound could enhance a surgeon’s ability to visualise and remove cancerous tissue.

Source: American Chemical Society