Ultra-Hydrophilic Transition Metals as Histophilic Biomaterials

Abstract

Extremely hydrophilic surfaces have been prepared on titanium, stainless steel and cobalt chromium alloys after treatment by a chromosulfuric acid method at 200-240 °C. In spite of a ca. 300-500-fold higher surface roughness (Ra ∼ 880-1100 nm) in comparison to the quartz glass controls (Ra ∼ 2-3 nm), surfaces with contact angles close to 0° in the absence of contact angle hysteresis (ultra-hydrophilic surfaces) were obtained. We have called this phenomenon “Inverse Lotus Effect”. Metal surface layers exhibiting such properties form excellent priming coats with bioadhesive properties (histophilic surfaces) for the attachment of biocoats consisting of BMP-2 with bioactive properties in bone. Direct immobilization of BMP-2 on implant surfaces eliminates the need for a separate BMP-2 carrier or delivery system such as collagen, as is widely employed by others. A fundamental problem in such surfaces is that it is not at all certain that a protein immobilized in such a manner will retain its biological activity. In the case of BMP-2 it can be shown in vitro that the novel surfaces are biologically active. Similarly in vivo studies indicate an accelerated and improved osseointegration.