Fig. 1. Experimental setup for growth of calcium phosphate coatings on titanium foil. The underside of the foil sample is protected from precipitate settling out of solution.

Fig. 2. Time dependent pH variation of reaction solution during sample preseeding, during hybrid growth and during inorganic calcium phosphate coating growth.

Fig. 3. SEM micrographs comparing purely inorganic control (a) and hybrid (b) coatings on titanium foil. Inset of (b) is a high magnification image revealing nanoscale character of the hybrid coating.

Fig. 4. Powder XRD patterns for the inorganic control and the poly(l-lysine)-calcium phosphate hybrid. Major diffraction planes for OCP are labeled. (*) The peak at 28.8 degrees is a sum of the OCP reflection and the (2 1 0) reflection of calcium hydrogen phosphate hydroxide. (**) The peak at 22.9 degrees may be a strong OCP (2 0 1) or a new peak for the hybrid material.

Fig. 5. Reflective FTIR spectra for hybrid and inorganic control coatings on Ti. Inorganic coating patterns reveal characteristic bands for OCP, while the hybrid coating shows concomitant presence of poorly crystalline OCP and poly(l-lysine). High frequency peaks between 1350 and 2000 and above 3400 are believed to be due to ambient water from the reflective experimental setup.

Fig. 6. (a) A titanium surface, preseeded for 10 min with CaCl₂ and Na₂HPO₄. No calcium phosphate seeds are visible. (b) A titanium surface preseeded for 2 h with CaCl₂ and Na₂HPO₄. Seed crystals are visible on a Ti surface after 2 h of growth.

Fig. 7. SEM micrographs and corresponding EDS patterns showing different degradation behaviors of the hybrid coating (a–e) versus the inorganic coating (f–j). From left to right, samples shown as grown (a,f), treated in pH 7.4 buffer (b,g), treated in pH 7.4-buffered trypsin (c,h), treated in pH 7 buffer (d,i), and treated in pH 6 buffer (e,j). Scale bars are 1 μm. Black lines in EDS patterns represent measurement before degradation treatment while gray lines indicate patterns following treatment. The x-axis on the EDS plots represents energy (eV) and EDS patterns have been normalized by the background intensity between 3000 and 3500 eV.

Fig. 8. S:N ratios determined by XPS illustrating binding affinity of cysteine to hybrid and inorganic control coatings. Neither sulfur nor nitrogen was substantially detected on inorganic control samples. Error bars represent ±1 standard deviation from duplicate measurements.

XPS analysis of calcium phosphate pretreatments and coatings

Dependence of hybrid growth on Ti surface preseeding method

Coating stability under acidic and enzymatic degradation conditions