Dental implants use titanium because it is strong and doesn’t harm tissues, though it does lack some of the beneficial properties of natural tissues such as bones and teeth. Inspired by the humble mussel, which can attach itself very tightly to metallic surfaces due to special proteins found in its byssal threads, scientists at RIKEN have successfully attached a biologically active molecule to a titanium surface.
This development could lead to implants that are more biologically beneficial, according to the researchers. Their work comes from earlier discoveries that the mussel’s L-DOPA protein binds very strongly to smooth surfaces such as rocks, ceramics, and metals. L-DOPA also functions as a precursor to dopamines in humans and is used as a treatment for Parkinson’s disease.
“We thought it would be interesting to try to use various techniques to attach a biologically active protein—in our case we chose insulin-like growth factor-1 (IGF-1), a promoter of cell proliferation—to a titanium surface like those used in implants,” said Chen Zhang of the RIKEN Nano Medical Engineering Laboratory and first author of the study.
Using a combination of recombinant DNA technology and treatment with tyrosinase, the researchers created a hybrid protein that contained active parts of both IGF-1 and L-DOPA. Tests showed the proteins were able to fold normally. Further experiments in cell cultures demonstrated that the IGF-1 still functioned normally.
By incorporating the L-DOPA, the researchers confirmed that the proteins bound strongly to the titanium surface and remained attached even when the metal was washed with phosphate-buffered saline, a water-based solution. This resembles the properties of the mussel adhesive, which can remain fixed to metallic materials underwater.
“We are very excited by this finding because the modification process is a universal one that could be used with other proteins. It could allow us to prepare new cell-growth enhancing materials with potential applications in cell culture systems and regenerative medicine,” said Yoshihiro Ito, leader of the Emergent Bioengineering Research Team of the RIKEN Center for Emergent Matter Science.
“And it is particularly interesting that this is an example of biomimetics, where nature can teach us new ways to do things,” Ito said. “The mussel has given us new insights that could be used to allow us to live healthier lives.”