Surgery Patch Seals Wounds After Abdominal Surgery

ETH Zurich and Empa researchers have created a patch with a sensing function. It can be used to close wounds in the abdomen following surgery. The polymer patch warns of harmful leakage on sutures in the gastrointestinal tract before they occur.

After surgery on the stomach or intestines, they are a dreaded complication: leaks at the sutures where the contents of the digestive tract can slip into the abdomen. “Even today, such leaks are a life-threatening complication,” explains Inge Herrmann, Professor of Nanoparticular Systems at ETH Zurich and a researcher at Empa in St. Gallen.

The concept of using a plaster to encapsulate sutured tissue in the abdominal cavity has already made its way into operating rooms. However, the patches employed, which are constructed of protein-containing material, dissolve too quickly when exposed to digestive juices. Herrmann’s group has so collaborated with Andrea Schlegel, a surgeon at the University Hospital Zurich, to seek innovative solutions.

Scientists have developed a plaster consisting of polymers that form a hydrogel, which can absorb moisture, over the last few years. The polymers form a bond with the intestinal tissue, sealing the lesion. As a result, the patch prevents acidic digestive juices and germ-laden food residues from escaping and causing peritonitis or even life-threatening blood poisoning.

Sensor Reaction to Acid and Enzymes

Now the researchers have gone one step further: “Surgeons have told us that they keep a close eye on the surgical field during even the most complicated procedures—but as soon as the abdominal cavity is closed, they are ‘blind’ and may not notice leaks until it is too late,” says Alexandre Anthis, postdoc in Herrmann’s group and co-developer of the patch.

As a result, the researchers outfitted their patch with non-electronic sensors that alert them before digestive juices escape into the abdominal cavity. The sensors are protein structures or salts embedded in the patch that react to variations in pH produced by escaping stomach acid or to specific enzymes found in the gut. When the sensor elements come into contact with digestive juices, their structure changes, which doctors may detect using biomedical imaging from outside the body.

Shape that draws attention
The researchers have succeeded in equipping the sensor parts in such a way that their reaction may also be detected by computer tomography (CT), as they describe in the newest issue of the journal Advanced Science. This was accomplished because the scientists were able to form the sensor elements in a way that is visible in computed CT using a combination of reactive salts and insoluble tantalum oxide. “On contact with digestive fluid, for example, the sensor changes its shape from a filled round area to a ring,” says Benjamin Suter, doctoral student in Herrmann’s group and first author of the latest study.

The sensor parts were first constructed by the researchers in a report released last year, but they lacked a shape-changing capability at the time. Furthermore, at the time, only ultrasonic imaging was capable of detecting the structural change in the plaster following a sensor reaction. The difference may now be noticed using both imaging techniques.

“In future, a sensor whose shape clearly stands out from anatomical structures in CT and ultrasound images, could reduce ambiguity of impending leak diagnostics,” explains Herrmann. The intestinal patch could thus not only reduce the risk of complications after abdominal surgery, but also shorten hospital stays and save health care costs. “The intestinal patch project is already attracting a great deal of interest from the medical profession,” says the ETH professor. Now it is important to advance the application of the clinically relevant innovation in practice.

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