Hydrogel laminate may improve catheters and condoms

Materials World magazine
1 Sep 2017

An MIT-developed hydrogel laminate material can be embedded with drugs and coated onto elastomer products. Kathryn Allen reports.

By coating medical devices such as catheters and intravenous lines, as well as condoms, in a layer of hydrogel, engineers at MIT, USA, could improve comfort, reduce friction and increase product safety. 

MIT engineers have developed a method for bonding a hydrogel to elastomer materials, including latex, silicone and rubber. This method involves dip-coating the devices, which have been treated to ensure they will adhere to the hydrogel polymers, into a hydrogel precursor solution. They are then exposed to UV light. The thickness and composition of the hydrogel layers can be altered to change their rigidity while the elastomer layer prevents molecules passing through the material.

German Parada, chemical engineering graduate student at MIT and first author of the paper, told Materials World, ‘The hydrogel is a water-swollen double polymer network made out of a covalently cross-linked polymer (arylamide in this work) and an ionically-cross-linked biopolymer (alginate and chitosan in this work). One of the best features of the laminate and coatings work is that the composition of the hydrogel can be modified but the principle will remain the same.’ 

As well as being impermeable, the hydrogel laminates formed are slippery, stretchable and durable – the team found that they could tolerate being bent and twisted. Parada attributes this durability to ‘the hydrogel [being] firmly attached to the elastomer material (sheet, medical device, etc) by grafting of the hydrogel polymer chains during the curing process, so that the coating will not delaminate easily.’ The hydrogel used, developed at MIT in 2012 by team leader and Professor of Mechanical Engineering Xuanhe Zhao, is also very tough, according to Parada. 

In 2012, Zhao’s team bonded hydrogels to elastomers using benzophenone, to treat the elastomer surface, and UV light. To test the properties of the hydrogel laminates, Zhao’s team used a two-chamber tank. One side was filled with deionised water, while the other was filled with molecular dye. The hydrogel laminate prevented the dye from travelling to the other chamber. However, when the experiment was repeated with a layer of hydrogel alone, it did not stop the dye from spreading. 

The hydrogel laminates can have drugs integrated into them, which can be released to treat infection or, for example, a latex allergy. A thicker elastomer will increase the laminate’s rigidity, while a thicker coating of the hydrogel will allow more drugs to be incorporated. 

Parada said, ‘The current hydrogel material has better antifouling properties – which prevent the attachment and growth of bacteria – than elastomer materials, but we can easily adjust the hydrogel composition to further improve those properties and prevent any growth of biofilms. As for monitoring infection, it would be possible to incorporate sensing molecules that respond to infection markers, such as increased temperature, lower pH, presence of bacterial nucleic acids, proteins and signalling molecules.’ 

The team is working with clinicians and medical device professionals to develop the research. 

To read Impermeable Robust Hydrogels via Hybrid Lamination in full, visit bit.ly/2v3Knz