Microneedle Skin Patch Detects Melanoma Without Biopsy or Blood Draw

Melanoma, the most aggressive form of skin cancer, currently requires patients, especially those with fair skin and moles, to undergo regular doctor visits and biopsies every six months to determine if growths are malignant or benign. This process can be invasive, costly, and time-consuming. Traditional diagnostic methods often involve blood draws or surgical biopsies, making them inaccessible for routine, rapid screening. Detecting melanoma early is crucial to improving outcomes, but limitations in current testing options delay diagnosis and increase patient anxiety. Now, researchers have developed a skin patch and test strip that allow for non-invasive, rapid detection of melanoma without the need for a biopsy or blood sample.

ExoPatch, developed by researchers at the University of Michigan (Ann Arbor, MI, USA), is a silicone patch embedded with star-shaped microneedles that are just 0.6 mm long. These microneedles are coated with a gel containing Annexin V protein that attracts and captures exosomes, tiny vesicles released by cells from interstitial fluid in the epidermis. Once applied to the skin, the microneedles painlessly penetrate only the topmost layer without drawing blood. After 15 minutes, the patch is removed and placed in acid, dissolving the gel and releasing the exosomes into a solution. A test strip, similar to an at-home COVID-19 test, is then dipped into the solution: two lines indicate the presence of melanoma exosomes, while one line indicates a negative result.

The ExoPatch was first validated on pig skin samples due to their similarity to human skin, with microscopy confirming microneedle penetration of 350 to 600 nanometers well within the epidermis. The system was then tested on tissue samples from mice, half of which had been injected with human melanoma tumor fragments. The patch successfully adhered to exosomes in the 30 to 150 nanometer range and was able to distinguish between melanoma and healthy tissue with a 3.5-fold darker test line for melanoma samples. The findings, published in Biosensors and Bioelectronics, showed that the patch isolated 11.5 times more exosomal protein from melanoma tissues, indicating high specificity. Future plans include a pilot study in humans followed by clinical trials. The gel coating of the ExoPatch could also be modified to detect exosomes from other solid tumors such as lung, breast, colon, prostate, and brain cancers.

“This is the first patch designed to capture disease-specific exosomes from fluid under the skin. The potential applications are huge,” said Sunitha Nagrath, co-corresponding author of the study.

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