Self-Cleaning Membrane for Implantable Glucose Sensors

An implantable sensor that allows diabetics to more effectively monitor their blood-sugar levels is a step closer to reality, thanks to Melissa Grunlan, associate professor in Texas A&M University's Department of Biomedical Engineering. Grunlan is developing a self-cleaning membrane that envelops an implanted glucose sensor, shielding it from the body's immune response that would otherwise render it nonfunctional. Made from a hydrogel (the same general type of material from which contact lenses are made), Grunlan's self-cleaning membrane is thermoresponsive, meaning it contracts and expands in response to changes in temperature.

Transcript

00:00:05 My name is Melissa Grunlan and I am an associate professor in the Department of Biomedical Engineering at Texas A&M University. My area of research focuses on developing new polymer biomaterials to improve how current medical devices function or to make new medical devices as well as polymers that can be used for regenerative therapies. One of the most interesting projects, I think, that we’re working on right now is the development of a self-cleaning membrane for a glucose biosensor. This would be a biosensor that could be placed inside the body of a diabetic patient so that they could monitor their glucose levels, their blood sugars, at all-time points during the day, during the night. Right now what diabetics have to do is they take finger prick test where they draw a blood sample and place it on a strip inside a glucose meter. This is encouraged to be done maybe four times a day or more.

00:01:06 Many patients don’t comply even with this because it’s uncomfortable, its inconvenient or they just might forget. So having an implanted glucose biosensor that could continuously monitor your glucose levels would really revolutionize how diabetics monitor their blood sugar levels. What we’re trying to do, specifically with the self-cleaning membrane, is to make the body accept and not reject a glucose sensor that’s implanted, let’s say, at the wrist just below the skin. So the body normally has this built in mechanism to say okay, there’s a foreign body, in this case a sensor that you’ve implanted in and the body says that shouldn’t be here so we’re going to seal it off; we’re going to send in cells and proteins, and eventually that sensor is sealed off from the environment, glucose is no longer getting to the sensor, and finally the sensor won’t work. So really the hurdle is a self-cleaning

00:02:14 membrane that we’re trying to develop, so this would enable the sensor to function over a long period of time. And so this self-cleaning membrane, it’s basically a hydrogel material, it’s like the material you see in your soft contact lens, it’s very soft, hydrated, squishy like material. But what we’ve done specifically is to use thermo responsive hydrogel, this is a hydrogel that when you heat it, it collapses and when you cool it back to body temperature it re-swells. So the big idea for this self-cleaning membrane is that you would wrap it around your glucose sensor, it would be implanted just below the skin, subcutaneously, and the person would wear a watch-like device over their implant. Well this watch-like device would be the meter that’s reading the glucose level signal that’s coming from the sensor, but it would also have a heating element that would be

00:03:18 attached to the watch. So periodically the heating element would heat the skin, through the skin, the membrane would collapse and that process kicks off cells and proteins, that’s the cleaning process that the membrane goes through. And so when it cools back down it re-swells and then that newly cleaned membrane allows the glucose to diffuse through it to the sensor, and that diabetic patient then can start to resume measuring their glucose levels.