A hi-tech tattoo to detect melanomas

A temporary tattoo made up of nanoparticles and microneedles could make it possible to detect melanoma when it is still invisible to the naked eye, opening up new perspectives for the early diagnosis of the most aggressive of skin tumors. This is what emerges from a study published in the journal Nature Sensors and coordinated by Jinyang Liang of the Institut national de la recherche scientifique (INRS) of Quebec, carried out in collaboration with researchers from the University of Montreal.

The goal of the research is to address one of the main challenges of dermatology: recognizing melanomas in the early stages, when the lesions are still too small to be identified through traditional clinical examination. Currently, diagnosis is based primarily on visual observation of suspicious lesions followed by biopsies, invasive procedures that often prove unnecessary. According to the authors, the new technology could offer a rapid, direct and non-invasive method to evaluate suspicious skin changes, reducing the number of unnecessary biopsies and improving diagnostic accuracy.

“Our goal is to provide a minimally invasive tool to detect very small but already aggressive melanomas,” explains Jinyang Liang, senior author of the study. “Due to their small size, these lesions are often missed by visual clinical inspection and may therefore go unnoticed.”

How microneedles and microscopic thermometers work

At the heart of the technology is a patch made up of painless microneedles that deposit specialized nanoparticles under the skin, forming a sort of smart temporary tattoo. These nanoparticles behave like microscopic thermometers. When illuminated with near-infrared light they emit visible light and the duration of the light emission varies depending on the local temperature.

Because cancer cells consume more oxygen and nutrients than healthy tissue, they also produce more heat. The system is therefore able to transform minimal thermal differences into a highly sensitive optical signal. Using an ultra-fast imaging platform, called SMEAR-ULM, researchers obtain a detailed thermal map of the skin with sub-millimeter resolution and sub-degree centigrade sensitivity.

“We acquire all the information necessary to build an instant temperature map in a single image,” explains Yingming Lai, first author of the study. “This makes the method rapid and robust in monitoring abnormal thermal responses associated with small melanomas even under complex biological conditions.”

The results of the study and future prospects

In the experimental models used in the study, the system identified micro-melanomas just four days after their appearance, a stage in which they are generally too small to be detected by conventional techniques. The researchers point out that traditional infrared-based thermographic methods can normally only identify tumors larger than five millimeters in diameter, dimensions that can already be seen with the naked eye.

According to Sylvain Meloche, professor of medicine at the University of Montreal and co-lead author of the research, the experimental model used reproduces the genetic alterations observed in human melanomas and could therefore have important future clinical implications.

In addition to early diagnosis of melanoma, the authors believe that the platform can be adapted to monitor other biological parameters, such as pH or ionic concentrations, opening up new applications in the field of biomedical imaging and precision diagnostics. The technology thus transforms skin temperature from a simple secondary indicator to a potential diagnostic biomarker for the early identification of skin cancers.