- Implants typically require interaction between biological molecules and the metal or plastic surfaces.
- Sometimes the body reacts badly to the implant material.
- Research shows coating the implant with free radicals can make the devices appear less foreign to the body.
The front and side view of a total knee replacement. Research shows coating such implants with free radicals may help the body accept the device. Click to enlarge this image.
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Coating artificial knees with free radicals could make the devices appear less foreign to the body and reduce the chance of implant rejection.
The research by applied physicist Professor Marcela Bilek of the University of Sydney and colleagues, is reported today in the Proceedings of the National Academy of Sciences.
"It puts a cloak around the nasty surface of the implant," said Bilek, about the new coating.
Knee implants, stents and other biomedical implants typically require the interaction between biological molecules and metal or plastic surfaces.
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But when proteins in the body interact with the artificial surface of the implant they lose the folded shape they need for their proper function.
The body tries to break these "denatured" proteins down, but when this doesn't work it tries to isolate the implants with a huge wall of scar tissue.
To reduce the risk of implants leading to inflammation, rejection and development of scar tissue, Bilek and colleagues have developed a new way of coating bio-implants so they present a more friendly face to folded proteins and avoid a bad reaction from the body.
The coating is developed by inserting the surface to be treated into a vessel of plasma. Electrostatic forces cause energetic ions in the plasma to hit and penetrate the surface leading to the production of free radicals, which have unpaired electrons, in the material.
Once taken out of the plasma, the free radicals migrate to the top of the surface where they react with oxygen in the air.
This makes the surface hydrophilic so that it is attractive to folded proteins, which are normally folded in a way that makes their exterior surface compatible with a watery environment. Over time, more free radicals move to the top of the surface, where they can lock proteins in place with covalent bonds.
As part of the special coating, these free radicals would stay bound to the proteins and be blocked from causing havoc in the body, said Bilek.
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As well as making implant surfaces appear less foreign to the body, the researchers are also involved in developing designer proteins that can be used in the coating to encourage tissue to integrate with the artificial surface in a controlled way.
Bilek said the new coating could also be used in biosensors that detect the presence of pathogens and other molecules. In this application the free radicals would keep the biological molecules that are the "sensing" part of the device in the right shape for detection.
The coating could also be used in microarrays that facilitate early treatment of disease by detecting an 'unhealthy' pattern of proteins produced by the body, said Bilek. And the coating could be used to speed up processing of food, and the textiles and creation of biofuels.
Bilek and colleagues are working with Cochlear (manufacturer of cochlear ear implants), as well as with companies involved in producing diagnostic arrays and replacement spinal discs. Bilek predicts the coating could be used in biosensors and diagnostic arrays within two years but that its use in bio-implants would take much longer.
Tags: Biofuels, Biomedical, Bionics, Devices, Plastic
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