Shape-shifting stickers offer early detection of surgical complications

imeng.vip:03月-10日 Three variations of the ultrasound sticker displayed on a fingertip for scale.

Researchers have created a unique sticker allowing medical professionals to use a basic ultrasound machine to check patients’ deep tissues and organs.

A collaborative effort between Northwestern University and Washington University School of Medicine in St. Louis has led to the development of a flexible adhesive sticker. When applied to an organ, this sticker responds to the body’s varying pH levels by undergoing morphological changes.

Scientists claim this phenomenon can be a precursor to surgical issues, including anastomotic leaks. Using ultrasonic imaging, clinicians may then see these form changes in real-time.

The details of the team’s research were published in the journal Science.

Assessing gastrointestinal leaks

Postoperative gastrointestinal leaks are common 3–7 days following surgery and can be dangerous if detected too late. Although early diagnosis of this problem remains challenging, it requires continual monitoring.

According to the team, the main issue is that it is impossible to foresee who would experience these kinds of issues. Furthermore, the patient is already very sick when they start exhibiting symptoms.

Rather than creating brand-new imaging technologies, researchers focussed on improving existing techniques, allowing them to “see” elements that would not normally be apparent. Ultrasound technology offers manyefits, including low cost, wide availability, lack of complicated equipment requirements, and no risk of radiation exposure for patients.

According to the team, the organs’ position, form, and structure can be ascertained using sound waves. However, ultrasound technology cannot accurately distinguish between different body fluids. For example, the appearance of stomach fluid and blood is the same.

Ultimately, researchers found a way to get around this restriction by employing tiny sensor devices made to be readable by ultrasonic imaging. In particular, they used a flexible and chemically responsive soft hydrogel to make a tiny sticker that adheres to tissue.

Subsequently, the minuscule, paper-thin metal disks were inserted into the thin hydrogel layers. The sticker swells in the presence of acidic substances, such as stomach acid. The sticker shrinks when it comes into contact with caustic substances like pancreatic secretions.

Novel pH-responsive ultrasound stickers

In reaction to pH changes, the hydrogel expands or contracts, causing the metal disks to shift inward or outward accordingly. Then, these minute positioning changes are seen on the ultrasound.

In ultrasound imaging, the metal disks contrast sharply because their acoustic properties differ significantly from the surrounding tissue’s. “In this way, we can essentially ‘tag’ an organ for monitoring,” said John A Rogers, the Louis Simpson and Kimberly Querrey Professor of Materials Science and Engineering, Biomedical Engineering and Neurological Surgery at Northwestern University, in a statement.

The team used bioresorbable polymers to create these stickers because monitoring is only necessary during the healing period following surgery. When no longer required, they harmlessly and naturally vanish within the body.

The group also made stickers in different sizes. The largest has a diameter of 12 millimeters, and the smallest is only 4 millimeters. Researchers highlight that radiologists might find it challenging to manually evaluate the images given that the metal disks are all 1 millimeter or smaller. They also developed software that can automatically analyze the photos and identify any relative movement of the disks with high precision to get around this problem.

Researchers tested the novel sticker on small and large animal models to determine its effectiveness. Even when the shape-shifting sticker was ten centimeters deep into the tissues, ultrasonography imaging in the trials reliably identified changes in the sticker. The sticker changed shape quickly in the presence of unusually high or low-pH liquids.

According to the team, the device might be inserted following surgery. Clinicians can also utilize the compact and flexible device to fold it up and fit it inside a syringe to inject the tag into the patient’s body.

The team plans to investigate the potential of comparable tags that might identify temperature variations or internal bleeding. “Detecting changes in pH is a good starting point. But this platform can extend to other types of applications by use of hydrogels that respond to other changes in local chemistry, or to temperature or other properties of clinical relevance,” said Rogers.

Abstract

Monitoring homeostasis is an essential aspect of obtaining pathophysiological insights for treating patients. Accurate, timely assessments of homeostatic dysregulation in deep tissues typically require expensive imaging techniques or invasive biopsies. We introduce a bioresorbable shape-adaptive materials structure that enables real-time monitoring of deep-tissue homeostasis using conventional ultrasound instruments. Collections of small bioresorbable metal disks distributed within thin, pH-responsive hydrogels, deployed by surgical implantation or syringe injection, allow ultrasound-based measurements of spatiotemporal changes in pH for early assessments of anastomotic leaks after gastrointestinal surgeries and their bioresorption after recovery period eliminates the need for surgical extraction. Demonstrations in small and large animal models illustrate capabilities in monitoring leakage from the small intestine, the stomach, and the pancreas.