November 2, 2016
A team of Japanese researchers has pioneered a new method for improving the biocompatibility of implant surfaces based on the chemical properties of mussels. The study contributes to a field of research that is exploring the use of proteins to ‘immobilise’, or fix, organic cells to metal surfaces.
The authors, based at the RIKEN research institute, Saitama, Japan, identified the natural adhesive properties of mussels as a potential method for improving attachment to metal surfaces. These molluscs use protein secretions to tightly bond their cells with surfaces, including metallic or ceramic ones, and can retain this grip even when submerged under water. The team identified that advances in controlling gene expression may enable them to activate the binding property of specific proteins, which could then be applied to implant surfaces.
The key chemical in the reaction is dopamine (3,4-dihydroxyphenethylamine) which had not previously been integrated into protein-based growth factors for use on implant surfaces. However, the scientists were concerned that the direct incorporation of such a chemical may compromise the protein’s underlying structure, negating the effect.
An innovative two-stage engineering method was devised by the team to express dopamine in a growth factor. The non-intrusive chemical tyrosine was incorporated into the protein, which was subsequently mixed with the enzyme tyrosinase. Tyrosinase has been used in other research to convert tyrosine into dopamine. In this case, the reaction took place without unsettling the tertiary structure of the protein, and dopamine was safely generated within it – closely matching that of the underwater adhesive secreted by mussels.
The authors tested the chemical by applying it to titanium-coated discs. Titanium is commonly used for many medical devices including dental implants. After applying the modified growth factor, significantly enhanced cell growth was observed on the surface of the discs as well as improved cell binding properties.
This outcome could have an impact on implant procedures, as cells may bond with implant surfaces more easily if they are coated with the treated growth factor. As well as having applications in implant dentistry, the new method for expressing dopamine in growth-factor proteins could be harnessed in regenerative medicine and cell culture systems. The study was published in Angewandte Chemie.