No abstract

The kinetics of development of ultra-hydrophilicity by concentrated chromosulfuric acid action at 240 C on titanium and medicinal 316L steel miniplates have been measured by a temperaturejump method. It is shown here that ultra-hydrophilicity (contact angle <10, absent contact angle hysteresis) is fully developed on electropolished titanium, anodically oxidized titanium, microstructured (sandblasted, acid etched) titanium and steel after 10 -20 min in chromosulfuric acid. The simultaneous determination of the microscopic roughness factor leads to the conclusion that ultra-hydrophilicity is not due to an increase in roughness factor, but is probably due to surface chemical changes. The very low contact angles therefore reflect high surface energies. In the case of the microstructured (sandblasted, acid etched) titanium surface the formation of a nanostructure (spheroids ca. 100 nm in diameter) especially in the valleys of the microstructure can be demonstrated. Ultra-hydrophilicity is lost in pure water but is conserved in liquids such as dry methanol or dry ethanol and also in the dry state through protection by a fine dissication layer. Thus the titanium surface enhanced by chromsulfuric acid action displays novel physicochemical and probably biological functions in the form of ultra-hydrophilicity and osteophilicity respectively.

Bacterial biofilms of Pseudomonas aeruginosa selectively labeled by introduction of 2-(13)C-glycerol was studied by solid-state and high-resolution nuclear magnetic resonance. The (13)C nuclei were mainly integrated into mannuronate and guluronate, the two monomer units forming the bacterial alginate. The signal for the C5 position of the mannuronate, which was easily identified and well separated from other peaks, was analyzed for molecular mobility. The result indicated a high degree of motional freedom within the molecular network of the alginate. Despite the fact that the alginate was part of a solid aqueous gel phase, the reorientation mechanism of the monomer units came close to isotropic tumbling. Solid-state spectra of biofilms labeled in the described manner may serve as a valuable tool for noninvasive analyses of molecular mobility of the alginate component under various influences, thereby revealing important structural information. In addition, the effect of a monovalent electrolyte (LiCl) on the molecular mobility of alginate fragments in an aqueous solution was studied by determining the spin-lattice relaxation times, line widths and line shapes under variations of the ion concentration. The presence of ions accelerated overall motions but left rapid local motions virtually unaffected.