Regionalized quantitative LA-ICP-MS imaging of the biodegradation of magnesium alloys in bone tissue
Abstract
The spatially and timely resolved degradation of Mg alloys used as implants in bone material was monitored by LA-ICP-MS. Data evaluation and interpretation was accomplished by means of a geospatial information software (ArcGIS) tool to match spatially referenced LA-ICP-MS data to the microscopic images and to create regionalized images of quantitative data in order to describe the biodegradation process. Quantification was accomplished by matrix matched hydroxyapatite standards. Total combined uncertainty budgets were assessed for the entire quantification process. In the study, rat bones were extracted after 2 and 6 months implantation time and were analyzed for the lateral distribution of the alloying elements (Mg, Mn, Zn, Zr and Yb) in bone cross sections. The use of ArcGIS enabled the spatial referencing of data points and the identification of regions of interest by means of chemical and structural parameters. Moreover, ArcGIS allowed for the direct statistical analysis of defined areas (zones of interest) within these regions. Selected zones visualizing the Mg mass fractions at different distances from the pin after 2 and 6 months and within the blank sample were determined by chemometric means using cluster analysis and showed a clear decrease of the Mg content in the bone material surrounding the pin over time. Four meaningful different zones with significantly different Mg mass fractions in hydroxyapatite could be identified ranging from 8 μg g−1 in undisturbed cortical bone to 16 μg g−1 adjacent to the pin.
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