Ann Arbor Times

Researchers at the University of Michigan have developed a new silicone patch with star-shaped microneedles, called the ExoPatch, which may enable at-home testing for melanoma. The technology aims to help patients detect this aggressive form of skin cancer early without needing a biopsy or blood draw.

The project received funding from the National Institutes of Health and was described in a study published in Biosensors and Bioelectronics. In animal tests, the ExoPatch was able to distinguish melanoma from healthy skin in mice.

“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,” said Sunitha Nagrath, Dwight F. Benton Professor of Chemical Engineering at U-M and co-corresponding author of the study.

The microneedles are 0.6 mm long and less than 100 nanometers wide at their tips. They are coated with a gel containing Annexin V protein, which attracts exosomes—small particles released by cells—from interstitial fluid in the epidermis. These exosomes contain DNA and RNA fragments used for cell communication; cancer cell exosomes can help tumors spread and detecting them may allow earlier diagnosis than previous methods.

After application to the skin, placing the patch in acid dissolves the gel coating and releases captured exosomes into a solution. A test strip dipped into this solution produces two lines if melanoma exosomes are present or one line if not, functioning similarly to at-home COVID-19 test strips.

“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.

In proof-of-concept studies using pig skin samples—which closely resemble human skin—the microneedles penetrated about 350 to 600 nanometers into tissue compared to approximately 18,300 nanometers thickness of human forearm epidermis. Mouse experiments showed that after 15 minutes on either healthy or melanoma-injected mouse skin samples, microscopy confirmed successful capture of exosomes within expected size ranges.

“When looking at microscopy images, I was happy to see how nicely the exosomes adhered to the microneedles and were within the 30 to 150 nanometer size range we expect,” said Scott Smith, U-M doctoral student of chemical engineering and co-lead author of the study.

Subsequent testing revealed that samples from melanoma tissue produced a line on test strips that was 3.5 times darker than those from healthy tissue. The ExoPatch also isolated more than eleven times as much exosomal protein from melanoma tissue as from healthy samples.

The next steps include pilot studies in humans followed by clinical trials before potential use in medical practice. Researchers note that modifying the gel coating could allow detection of other cancers with solid tumors such as lung, breast, colon, prostate, or brain cancer.

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

Funding for this research came from NIH grant number 1-R01-CA-208335-01-A1. The device was fabricated at U-M’s Lurie Nanofabrication Facility; additional testing took place in Biomedical Research Core Facilities and Rogel Cancer Center Immunology Core. Patent protection has been sought through U-M Innovation Partnerships.