Biocoating of Electropolished and Ultra‐Hydrophilic Titanium and Cobalt Chromium Molybdenum Alloy Surfaces with Proteins

Abstract

Bone morphogenetic proteins (BMPs) play a decisive role in bone development and osteogenesis. In the past they have been the subject of widespread research and clinical trials as stimulants of bone growth. Although recently recombinant human BMP-2 (rhBMP-2) has been chemically immobilized on implant surfaces leading to enhanced bone growth and accelerated integration in vivo, the non-covalent immobilization of proteins on metal surfaces is still poorly understood, since the oxide layers on metals like titanium, stainless steel or cobalt chromium alloys are poor adsorbents of proteins. Protein binding surfaces could either be generated by linking ionic groups (ion-exchange surface) or by coupling hydrophobic residues (hydrophobic interacting surface, HIS) to the surface. In this paper the preparation of protein adsorbing surfaces on titanium and cobalt chromium molybdenum alloy for the adsorption of rhBMP-2 and ubiquitin will be described. rhBMP-2 and ubiquitin are bound extremely tight to surfaces containing propyl or hexyl groups of a certain surface concentration and are slowly released over a range of at least 24–100 days making such surfaces applicable as long-term drug delivery devices for enhancing bone growth or implant integration.