Correlative Spectromicroscopy and Tomography
were performed using the ambient STXM on beam line 10ID1 at the Canadian Light Source at the University of Saskatche- wan in Saskatoon.
Results Biomaterials Interfaces. We have used chemically sen-
sitive correlative imaging by X-ray tomography (CT), TEM, STEM, ET, APT, and STXM to investigate the 4D (3D plus composition) structure of the interface between human bone and a Ti dental implant, which had been in place for 47 months [3]. Figure 2 presents results from ET, EELS tomography, and APT of a FIB-machined needle-shaped sample that is about 80 nm in diameter. Te Z-contrast from on-axis HAADF- STEM ET (Figure 2a) differentiates the phases in order of decreasing density: Ti implant (brightest), hydroxyapatite, and collagen/organic matter (darkest). Tere is evidence of continuous bone growth and integration with the surface of the laser-modified, commercially pure, titanium dental implant. Tis interfacial implant was shown to be rich in Ti oxide by EELS tomography, as shown in detail in reference [3]. Figure 2b shows the tomographic reconstruction of the series of EELS element maps on the same 80 nm needle. Te reconstruction provides higher resolution elemental map- ping of the interface than single raw maps from the tilt-series. Specifically, the reconstruction shows the Ca of the bone apa- tite (green) and the organic collagen (red). Te needle was then FIB sharpened to about 40 nm diameter and analyzed by APT. Te atom probe tomograph of Figure 2c shows that both Ca and C are in contact with an outer Ti oxide layer of the implant just outside a layer of TiN at the implant surface
(O and N APT maps not shown). Confirmation of these phase designations was accomplished by analysis of the EELS and STXM data, as discussed below. Correlative microscopy of a dental implant-bone inter-
face. Detailed chemical speciation was provided by 2D TEM- EELS at the Ca L2,3 Ca L2,3
, Ti L2,3 -OD396 eV
edge, as well as STXM studies at the C K, , O K, and N K edges. Figure 3a shows a HAADF-
STEM image of a bone-implant interface, and Figure 3b shows a STXM optical density difference map (OD400 eV
)
where the N-rich region is bright and other regions show a near-background intensity. While the bone and Ti implant regions were identified from Figure 3a, the STXM OD differ- ence image in Figure 3b clearly shows the TiN band inside the Ti implant. Te color composite (Figure 3d) combines com- ponent maps generated by fitting a N 1s image sequence (50 images at photon energies between 395–420 eV) to the N 1s spectra of protein in bone (green), the Ti implant (red) and the TiN coating (blue) (Figure 3c). It is clear that the N signal in the APT data (Figure 2c) is spatially correlated with the TiN band measured by STXM. Tis band was probably generated from a laser hardening surface treatment of the machined implant in air [20]. Figure 4 shows results from Ca L2,3 studies of the interface. Te Ca L2,3
and Ti L2,3 STXM spectra measured by both EELS and STXM indicate the presence of multiple
Figure 3: (a) STEM image of a FIB-milled thin section of bone-dental implant interface. (b) STXM optical density difference map (OD400
–OD396
Figure 2: (a) On-axis ET, (b) electron energy loss tomography (EELS ET), (c) APT of the interface of human bone and a Ti dental implant. The TiO and TiN designations are related to detailed analysis of the O and N species from APT spectra [3]. (Adapted from [3]).
14
. (c) N K-edge XANES spectra from regions indicated in (b). (d) STXM color-coded composite
of the chemical component maps of the implant (red), bone (green), and TiNx layer (blue) derived by fitting a full N 1s stack (50 images from 395–420 eV) to the spectra in (c) (reprinted from [3] with permission from John Wiley & Sons). All data from STXM except (a) TEM.
www.microscopy-today.com • 2019 March
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