Researchers at Université de Montréal and the Institut national de la recherche scientifique (INRS) have developed SMEAR-ULM, a painless patch of microneedles that deposits specialized nanoparticles just beneath the skin—creating what they call an "intelligent tattoo" capable of detecting melanoma before it becomes visible to the human eye.
The breakthrough addresses a critical gap in dermatology. Melanoma incidence continues to rise in Canada, and early diagnosis is essential for survival. Current diagnostic approaches rely on visual examination followed by biopsies—invasive procedures that are often unnecessary. By enabling rapid, direct, and noninvasive assessment of suspicious skin lesions, this technology could reduce unnecessary biopsies and improve early diagnostic accuracy, potentially transforming clinical decision-making.
The system works by turning the subtle heat signature of cancer cells into a measurable signal. The temporary "tattoo" functions as an array of microscopic thermometers. When illuminated with near-infrared light, the nanoparticles emit visible light whose duration depends directly on local temperature. Because cancer cells consume more oxygen and nutrients than healthy cells, they produce additional heat—a signal that SMEAR-ULM can detect with remarkable precision. An ultrafast imaging system captures all this information in a single high-speed snapshot, generating a detailed thermal map with submillimeter spatial resolution and sub-degree temperature sensitivity.
"Our goal is to provide a minimally invasive tool to detect very small, but still aggressive melanomas," said Jinyang Liang, senior author and INRS professor specializing in ultrafast imaging and biophotonics. "Because of their small size, they are usually excluded from clinical visual inspection, which leaves the threat unwatched. We want to detect them, so that intervention can be made as soon as possible."
The research, published in Nature Sensors and led by Liang in close collaboration with INRS professor Fiorenzo Vetrone and UdeM professors David Brambilla and Sylvain Meloche, represents a fundamental shift in how temperature is used for cancer detection. While tumors have long been known to generate more heat due to their higher metabolic activity, this signal has traditionally been too imprecise to serve as a reliable diagnostic marker. SMEAR-ULM changes that equation entirely.
The results are striking. In testing, researchers successfully detected micro-melanomas as early as four days old—a stage at which they are typically far too small to be identified by conventional imaging techniques. This early detection window could mean the difference between intervention and progression, between survival and severity.
The study was conducted in mice, but Meloche, a researcher at UdeM's Institute for Research in Immunology and Cancer and co-principal author, emphasizes the clinical relevance: "Even though this study was conducted in mice, this animal model replicates the genetic changes observed in human melanomas and could therefore potentially benefit patients."
Conventional thermal imaging methods rely on infrared technologies that suffer from limited spatial resolution and high noise levels—significant barriers to early detection. SMEAR-ULM overcomes these limitations by capturing all necessary information for an instantaneous temperature map in a single shot, making the method fast and robust enough to continuously monitor abnormal thermal responses in small melanomas, even within complex in vivo conditions. As melanoma incidence continues to rise, this "intelligent tattoo" offers a path toward catching cancer before it becomes visible—and before it becomes deadly.