Electrosprayed Enzyme Coatings as Bioinspired Alternatives to Bioceramic Coatings for Orthopedic and Oral Implants

The biological performance of orthopedic and oral implants can be significantly improved by functionalizing the non-physiologic metallic implant surface through the application of biologically active coatings. In this paper, a cost-effective alternative to traditional biomedical coatings for bone substitution through exploitation of the specific advantages of the electrospray deposition technique for the immobilization of the enzyme alkaline phosphatase (ALP) onto the implant surface is presented. Since ALP increases the local inorganic phosphate concentration required for physiological mineralization of hard tissues, ALP coatings will enable enzyme-mediated mineralization onto titanium surfaces. To evaluate the bone-bioactive capacity of the ALP-coated titanium surface, soaking experiments are performed. Although the purely inorganic so-called simulated body fluid is the standard in vitro procedure for predictive studies on potential bone bonding in vivo, an alternative testing solution is proposed that also contains organic phosphates (cell culture medium supplemented with the organic beta-glycerophosphate (beta-GP) and serum proteins), thereby resembling the in vivo conditions more closely. Under these physiological conditions, the electrosprayed ALP coatings accelerated mineralization onto the titanium surface as compared to noncoated implant material by mean of enzymatic pathways. Therefore, this novel approach toward implant fixation holds significant promise.