Quantification of calcium content in bone by using ToF-SIMS--a first approach

Area of Science:

• Biomaterials Science
• Analytical Chemistry
• Bone Biology

Background:

• Spatially resolved calcium distribution and concentration in bone are crucial for assessing bone quality.
• Accurate calcium mapping aids in diagnosing bone diseases, understanding bone remodeling, and evaluating bone-implant interfaces.

Purpose of the Study:

• To develop and validate a semi-quantitative method for mapping calcium distribution in bone cross-sections using time-of-flight secondary ion mass spectrometry (ToF-SIMS).
• To establish a calibration method for ToF-SIMS calcium quantification using synthesized standards.
• To demonstrate the enhanced lateral resolution of ToF-SIMS for bone calcium analysis.

Main Methods:

• Synthesized calcium hydroxyapatite collagen scaffolds with varying compositions as calibration standards.
• Characterized standards using loss on ignition, X-ray diffractometry (XRD), and X-ray photoelectron spectroscopy (XPS).
• Employed ToF-SIMS to map semi-quantitative calcium distribution in bone cross-sections with up to 1 μm lateral resolution.

Main Results:

• A linear dependence was observed between the secondary ion count rate for calcium and the calcium content in the synthesized standards.
• Established a calibration curve for quantifying calcium content in rat bone samples.
• Demonstrated superior lateral resolution of ToF-SIMS compared to XPS in calcium mass imaging.

Conclusions:

• ToF-SIMS provides a powerful tool for semi-quantitative, high-resolution mapping of calcium distribution in bone.
• The developed calibration method allows for accurate quantification of bone calcium content.
• This technique advances the locally resolved assessment of bone quality and disease progression, particularly in osteoporosis models.