MMaterialsgateNEWS 2017/07/20

New gel coatings may lead to better catheters and condoms

Bonded layers of rubber and hydrogel yield tough, slippery, and impermeable coatings.

Catheters, intravenous lines, and other types of surgical tubing are a medical necessity for managing a wide range of diseases. But a patient’s experience with such devices is rarely a comfortable one.

Now MIT engineers have designed a gel-like material that can be coated onto standard plastic or rubber devices, providing a softer, more slippery exterior that can significantly ease a patient’s discomfort. The coating can even be tailored to monitor and treat signs of infection.

In a paper published today in the journal Advanced Healthcare Materials, the team describes their method for strongly bonding a layer of hydrogel — a squishy, slippery polymer material that consists mostly of water — to common elastomers such as latex, rubber, and silicone. The results are “hydrogel laminates” that are at once soft, stretchable, and slippery, and impermeable to viruses and other small molecules.

The hydrogel coating can be embedded with compounds to sense, for example, inflammatory molecules. Drugs can also be incorporated into and slowly released from the hydrogel coating, to treat inflammation in the body.

The team, led by Xuanhe Zhao, the Robert N. Noyce Career Development Associate Professor in the Department of Mechanical Engineering at MIT, bonded layers of hydrogel onto various elastomer-based medical devices, including catheters and intravenous tubing. They found that the coatings were extremely durable, withstanding bending and twisting, without cracking. The coatings were also extremely slippery, exhibiting much less friction than standard uncoated catheters — a quality that could reduce patients’ discomfort.

The group also coated hydrogel onto another widely used elastomer product: condoms. In addition to enhancing the comfort of existing latex condoms by reducing friction, a coating of hydrogel could help improve their safety, since the hydrogel could be embedded with drugs to counter a latex allergy, the researchers say.

“We’ve demonstrated hydrogel really has the potential to replace common elastomers,” Zhao says. “Now we have a method to integrate gels with other materials. We think this has the potential to be applied to a diverse range of medical devices interfacing with the body.”

Zhao’s co-authors are lead author and graduate student German Parada, graduate students Hyunwoo Yuk and Xinyue Liu, and visiting scientist Alex Hsieh.

A tailored gel

Zhao’s group previously developed recipes to make tough, stretchable hydrogels from mixtures composed mostly of water and a bit of polymer. They developed a technique to bond hydrogels to elastomers by first treating surfaces such as rubber and silicone with benzophenone, a molecular solution that, when exposed to ultraviolet light, creates strong chemical bonds between the elastomer and the hydrogel.

The researchers applied these techniques to fabricate a hydrogel laminate: a layer of elastomer sandwiched between two layers of hydrogel. They then put the laminate structure through a battery of mechanical tests and found the structure remained strongly bonded, without tearing or cracking, even when stretched to multiple times its original length.

The team also placed the laminate structure in a two-chamber tank, filled on one side with deionized water and the other with molecular dye. After several hours, the laminate prevented any dye from migrating from one side of the chamber to the other, whereas a layer of hydrogel alone let the dye through. The laminate’s elastomer layer, they concluded, made the structure as a whole strongly impermeable — a feature they reasoned could also prevent viruses and other small molecules from passing through.

In other tests, the team chemically mixed pH-sensing molecules into the layer of hydrogel lining one side of the elastomer layer, and green food dye into the opposite hydrogel layer. They once again placed the entire structure into the two-chamber tank and filled both sides with dioinized water.

As the researchers changed the acidity of the tank’s water, they observed that the parts of the hydrogel containing pH indicators lit up. Meanwhile, the green dye seeped slowly from the opposite hydrogel layer into the second tank, mimicking the action of drug molecules.

“We can put pH-sensing molecules in hydrogels, or drugs that are gradually released,” Parada says. “For different applications, we can modify the gel to accommodate that application.”

Tying knots

As a first foray into possible applications for hydrogel laminates, the researchers used their previously developed techniques to coat hydrogel onto various elastomer devices, including silicone tubing, a Foley catheter, and a condom.

“Our first major focus was catheters, because they are rigid and not very comfortable, and infection of catheters can cause around 50 percent of readmissions to hospitals,” Parada says. “We also thought we could apply this to condoms, because existing latex condoms cause lots of sensitivities and allergies, and if you can put drugs in the gel, you could have better protection.”

Even after sharply bending and folding the coated tubing into a knot, the researchers found the hydrogel coating remained strongly bonded to the tubing without causing any tears. The same was true when the researchers inflated both the coated catheter and the coated condom.

Parada says the dimensions of a hydrogel laminate may be tuned to accommodate different devices. For instance, scientists can choose a thicker elastomer to increase a laminate’s rigidity, or use a thicker coating of hydrogel to incorporate more drug molecules or sensors. Hydrogels can also be designed to be more or less slippery, depending on the amount of friction desired.

“We have the capability to fabricate large-scale hydrogel structures that can coat medical devices, and the hydrogel won’t agitate the body,” Zhao says. “This is a technological platform onto which you can imagine many applications.”

Source: Massachusetts Institute of Technology – 18.07.2017.

Investigated and edited by:

Dr.-Ing. Christoph Konetschny, Inhaber und Gründer von Materialsgate
Büro für Material- und Technologieberatung
The investigation and editing of this document was performed with best care and attention.
For the accuracy, validity, availability and applicability of the given information, we take no liability.
Please discuss the suitability concerning your specific application with the experts of the named company or organization.

You want additional material or technology investigations concerning this subject?

Materialsgate is leading in material consulting and material investigation.
Feel free to use our established consulting services

MMore on this topic

Rice chemists develop hydrogel strings using compound found in sea creatures

Rice University chemists can thank the mussel for putting the muscle into their new macroscale scaffold fibers. The Rice lab of chemist Jeffrey Hartgerink had already figured out how to make biocompatible nanofibers out of synthetic peptides. In new work, the lab is using an amino acid found in the sticky feet of mussels to make those fibers line up into strong hydrogel strings. Hartgerink and Rice graduate student I-Che Li introduced their room-temperature method this month in an open-access paper in the Journal of the American Chemical Society. The hydrogel strings can be picked up and moved with tweezers, and Li said he expects they will help labs gain better control over the growth... more read more

In research published in Nature Materials, a team led by scientists from the RIKEN Center for Emergent Matter Science in Japan has developed a new hydrogel that works like an artificial muscle--quickly stretching and contracting in response to changing temperature.

They have also managed to use the polymer to build an L-shaped object that slowly walks forward as the temperature is repeatedly raised and lowered. Hydrogels are polymers that can maintain large quantities of water within their networks. Because of this, they can swell and shrink in response to changes in the environment such as voltage, heat, and acidity. In this sense they are actually similar to the plant cells, which are able to change shape as the amount of water within them changes in response to environmental conditions. However, most hydrogels do this very slowly, and must absorb and excrete water to either expand or shrink in volume. The unique property of the hydrogel developed... more read more

Rice University bioengineers have created a hydrogel that instantly turns from liquid to semisolid at close to body temperature – and then degrades at precisely the right pace.

The gel shows potential as a bioscaffold to support the regrowth of bone and other three-dimensional tissues in a patient’s body using the patient’s own cells to seed the process. The hydrogel created in the lab of Rice bioengineer Antonios Mikos is a liquid at room temperature but, when injected into a patient, becomes a gel that would fill and stabilize a space while natural tissue grows to replace it. The new material detailed in the American Chemical Society journal Biomacromolecules takes the state of the art a few steps further, Rice scientists said. “This study describes the development of a novel thermogelling hydrogel for stem cell delivery that can be injected into skeletal... more read more


Partner of the Week

Search in MaterialsgateNEWS