Bisphosphonate incorporation in surgical implant coatings by fast loading and co-precipitation at low drug concentrations.

The objectives of the present work was to evaluate the possibility for fast loading by soaking of bisphosphonates (BPs) into hydroxylapatite (HA) implant coatings biomimetically grown on crystalline TiO(2) surfaces, and also investigate the influence of different BP loading concentrations in a buffer during co-precipitation of a calcium phosphate containing layer onto these surfaces. The co-precipitation method created coatings that contained BPs throughout most of the coating layer, but the presence of BPs in the buffer hindered the formation of a bulk HA-layer, thus resulting in very thin coatings most likely consisting of islands built up by a calcium phosphate containing BPs. The coatings biomimetically grown on TiO(2) surfaces, were shown to consist of crystalline HA. Soaking of these coatings during 15 min only in a low BPs concentration containing buffer yielded a concentration on the coating surface of the same order of magnitude as obtained with soaking during 60 min in significantly higher concentrated buffers. This could be of advantage during surgery since the operating surgeon could make a fast decision whether or not to include the drugs in the coating based on the need of the particular patient at hand. The BPs present on the surface of the fast-loaded HA coatings were found to be strongly bound, something which should be beneficial for in vivo use. Both the co-precipitation method and the fast loading by soaking method investigated here are promising techniques for loading of BPs onto surgical implants. The simplicity of both methods is an advantage since implants can have spatially complicated structures.