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Next-gen surface modification bolsters implantable medical devices

A discovery by University of Sydney researchers could result in synthetic peptides integrating seamlessly with host tissue.

This potential new class of implantable devices would aim to provide biological signals to achieve this improved integration which will hopefully, reduce the risk of infection and increase effectiveness.

The team says it has developed practical techniques to guide and attach peptides to surfaces; computer simulations and experiments demonstrated control of both peptide orientation and surface concentration, achieved through application of an electric field.

Professor Marcela Bilek explained that biomaterial coatings could mask the devices and mimic surrounding tissue.

“The holy grail is a surface that interacts seamlessly and naturally with host tissue through biomolecular signalling,” said Bilek. She has developed a surface modification process which allows the biological molecules to be attached to the bio-device surface and enable this procedure.

“Although proteins have successfully been used in a number of applications, they don’t always survive harsh sterilisation treatments – and introduce the risk of pathogen transfer due to their production in micro-organisms.”

Bilek, together with Dr Behnam Akhavan and lead author PhD candidate, Lewis Martin, are examining the use of peptides that, when strategically designed, can recapitulate the function of the protein.

According to Martin, the team has managed to tune the orientation of biomolecules, which are less than 10nm in size, on the surface. “We used specialised equipment to perform the experiments, but the electric fields could be applied by anyone using a home electronics kit,” he said.

Akhavan believes that with industry support and funding, improved implantable devices could be available within five years.

“The application of our approach ranges from bone-implants to cardiovascular stents and artificial blood vessels,” Akhavan said. “For the bone implantable devices, for example, such modern bio-compatible surfaces will directly benefit patients suffering from bone fracture, osteoporosis, and bone cancer."

The peptides can be produced synthetically and are said to be resilient during sterilisation due to their small size. The challenge is ensuring they are attached at appropriate densities and in orientations that effectively expose their active sites.

According to the team, they have discovered several new levers that control peptide attachment, using applied electric fields and buffer chemistry. Permanent dipole moments are created through the charge separation on peptides. This moments can be aligned with an electric field, offering what the team describes as ‘optimal’ orientation of the molecules. When the peptides have an overall charge, the amount of peptide immobilised can also be tuned by the electrostatic interactions.

The findings, published in Nature Communications, states: “Our findings shed light on mechanisms of biomolecule immobilisation that are extremely important for the design of synthetic peptides and biofunctionalisation of advanced implantable materials.”

Author
Bethan Grylls

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