Dartmouth Engineering Researchers Develop Implant for Comprehensive Organ Health Monitoring After Surgery

The flexible microneedle array with backward-facing barbs that conform to uneven tissue. (Photo by Wei Ouyang and Xiangling Li)

"Many people will need surgery at some point of their lives, to repair an injury, remove a tumor, or receive a transplant," said Wei Ouyang, assistant professor of engineering at Dartmouth and the study's corresponding author. "When complications arise, they often go undetected until significant or even irreversible damage has occurred. Surprisingly, there's currently no good method for early detection." 

Published today in Nature Biomedical Engineering, the study demonstrates effective monitoring of organ health through both physical and chemical means. Using a 3D-printing-based fabrication process, the system features a flexible set of microneedles with backward-facing barbs that conform to uneven tissue and remain stable.

"Conventional implants typically only monitor physical parameters such as temperature and internal pressure. This is one of the first demonstrations of an implant that is capable of monitoring biochemical markers inside organs," Ouyang said. 

"Chemical markers are more powerful because they provide information about the molecular basis of complications, which is typically more specific than physical markers," he said.

Such comprehensive and continuous assessment of organ metabolism, oxygenation, and electrochemistry can enable more timely interventions for complications such as low blood flow and transplant rejection. 

With this problem in mind, the Dartmouth Engineering team—which includes first author Xiangling Li, a research associate in Ouyang's lab, along with co-authors PhD student Shibo Liu, researchers Gen Li, Mingwei Zhou, and Jaehyeon Ryu, engineering major Matthew Morales '27, and Professor Hui Fang—developed the device to be placed directly on organs during surgery rather than relying on blood tests that often fail to detect problems quickly enough. 

The system features "an electrically-programmable self-destruction mechanism," eliminating the need for device retrieval surgery. "I think the most beautiful thing is the device is bioresorbable," said Ouyang. "That's a big deal because a second surgery can increase hospital visits and healthcare costs and introduce further complications that delay patient recovery."

The device is made of a synthetic, biodegradable, and biocompatible material called poly-lactic-co-glycolic acid (PLGA) which is FDA-approved and widely-used in biomedical implants. PLGA breaks down into lactic acid and glycolic acid, which are naturally metabolized by the body into carbon dioxide and water.

"The first one- or two-week post-operative window is the most critical," said Ouyang. In the future, however, the team wants to develop materials that can dissolve more slowly and biosensors that can monitor for months or even years. Future applications include the potential to detect cytokines associated with inflammation or infection.