Selective repellent coating

‘Smart’ nanosurfaces designed to only accept beneficial substances

Image credit: Kevin Patrick Robbins, McMaster University

Researchers based at McMaster University, Ontario, Canada, have developed a surface capable of repelling essentially everything, except for specified substances which boost effectiveness and safety.

Completely repellent surfaces have existed since 2011 and have proved useful in keeping the insides of mobile devices free from water and dirt, keeping windscreens clear and repelling bacteria from areas which need to be sterile, such as kitchen surfaces.

However, these coatings have not proved to be a Holy Grail in medical applications, in which it is often necessary to repel virtually all substances, including bacteria and viruses, while accepting specific beneficial objects.

“It was a huge achievement to have completely repellent surfaces, but to maximise the benefits of such surfaces, we needed to create a selective door that would allow beneficial elements to bond with those surfaces,” said Professor Tohid Dldar, senior author of the ACS Nano paper describing the project.

For instance, a synthetic heart valve made with a repellent coating could prevent blood cells from sticking and forming clots – rendering it far safer by some measures – but would also prevent the body from naturally accepting and integrating the valve into its own heart tissue. A heart valve covered with a coating which accepts only certain substances could lower the risk of clotting while simultaneously lowering the risk of rejection.

“A coating that repels blood cells could potentially eliminate the need for medicines such as warfarin that are used after implants to cut the risk of clots,” commented Sara Imani, a PhD student in biomedical engineering who worked on the project.

“If you want a device to perform better and not be rejected by the body, this is what you need to do,” added Maryam Badv, another PhD student in biomedical engineering at McMaster University.

Dldar and his colleagues used nanoengineering techniques to develop a repellent coating which could accept only specified beneficial substances. In addition to improving the safety and effectiveness of other medical implants – such as vascular grafts and artificial joints – this type of coating could be used to develop more accurate diagnostic tests which eliminate interference from non-target elements which allowing targets to stick to the biosensor.

The researchers are in the process of transferring their smart surface into clinical use.

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