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Rapid at-home testing for skin cancer could now be possible, with researchers at the University of Michigan developing a silicone patch to do just that.
The ExoPatch, which contains star-shaped microneedles, successfully distinguished between melanoma and healthy skin in mouse skin tissue and pig skin samples, in a study funded by the National Institutes of Health. The research is published in Biosensors and Bioelectronics.
How the ExoPatch works
The ExoPatch features many microneedles, measuring just 0.6 mm long and at a width of less than 100 nanometers (0.0001 mm) at their tip.
“The star-shaped needles make puncture easier and less painful, but they are so small that they only go through the top-most layer of the skin, the epidermis, and do not draw blood,” explained Sunitha Nagrath, the Dwight F. Benton Professor of Chemical Engineering at U-M and the co-corresponding author of the study.
These microneedles are coated with a gel containing Annexin V, a protein that binds to exosomes from the interstitial fluid that fills the spaces between cells in the epidermis.
Exosomes
Exosomes are nanosized particles (30–150 nanometers) released by cells that transport proteins, RNA and other molecules. They play a role in cell communication and are increasingly studied as biomarkers for diseases, including cancer.
Once thought to be cellular “trash”, exosomes actually contain important DNA and RNA that play a role in cell-to-cell communication. Cancer cell exosomes can contribute to tumor spread, making their detection an early indicator of disease.
When applied to the skin for 15 minutes, the microneedles penetrate the epidermis without drawing blood. After removal, the patch is dissolved in an acidic solution to release the captured exosomes. A test strip dipped into this solution displays two lines if melanoma exosomes are present or one line if absent, functioning similarly to at-home COVID-19 tests.
Positive results in proof-of-concept tests
The ExoPatch was first tested on pig skin, chosen for its similarity to human skin. Imaging confirmed that the microneedles penetrated between 350 and 600 nanometers, within the epidermis but above the dermis. For scale, the human epidermis on the forearm is roughly 18,300 nanometers thick.
The device was then tested on mouse skin samples, half of which contained melanoma cells, in order to test whether the ExoPatch could capture melanoma exosomes from skin tissue.
After a 15-minute application window, the ExoPatch was removed and microscopy images were used to confirm that exosomes had been extracted using the microneedles. Following this, the ExoPatch was dissolved and processed as-intended with the test strips.
The ExoPatch was found to have collected 11.5 times more exosomal protein from melanoma samples than from healthy tissue, with the test strips producing a line 3.5 times darker for melanoma-positive samples.
Future work
According to the researchers, the next step to move this technology forward is conducting a pilot study in humans, followed by a series of clinical trials. If successful, the ExoPatch could be a rapid advancement for at-home melanoma testing – allowing individuals to detect the most aggressive form of skin cancer early, without a biopsy or blood draw.
“A fair-skinned person with moles must go to the doctor about every six months to send off a biopsy to see if they’re malignant or benign. With this test, they could instead test at home, get the results right away and follow up with a dermatologist for a positive result,” Nagrath said.
The researchers also suggest that modifying the gel coating could potentially allow for the detection of exosomes associated with other cancers, including lung, breast, colon, prostate and brain cancer.
“This is the first patch designed to capture disease-specific exosomes from fluid under the skin. The potential applications are huge,” said Nagrath.
Reference: Smith SM, Kumari A, Marvar JP, Onukwugha NE, Kang YT, Nagrath S. Stellate silicon microneedles for rapid point-of-care melanoma exosome isolation and detection via a lateral flow assay. Biosens Bioelectron. 2025;285:117560. doi: 10.1016/j.bios.2025.117560
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