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Probing Albumin Adsorption onto Calcium Phosphates by XPS and ToF-SIMS
J E Baio1, T Weidner, G Interlandi
1National ESCA and Surface Analysis Center for Biomedical Problems, Department of Chemical, University of Washington, Seattle, WA 98195.
Journal of Vacuum Science and Technology. B, Nanotechnology & Microelectronics : Materials, Processing, Measurement, & Phenomena : JVST B
|January 24, 2012
Summary
Bovine serum albumin (BSA) forms a monolayer on calcium phosphate surfaces. Surface binding alters BSA structure, with hydroxyapatite showing a slight but significant difference compared to dibasic calcium phosphate dihydrate.
Area of Science:
- Materials Science
- Surface Chemistry
- Biochemistry
Background:
- Calcium phosphates (CaP) are crucial biomaterials in bone regeneration.
- Understanding protein adsorption on CaP surfaces is vital for biomaterial design.
- Bovine serum albumin (BSA) is a model protein for studying protein-surface interactions.
Purpose of the Study:
- To investigate the adsorption and structural changes of bovine serum albumin (BSA) on three distinct calcium phosphate (CaP) phases.
- To quantify BSA adsorption and analyze structural alterations upon binding to hydroxyapatite, dibasic calcium phosphate dihydrate, and β-tricalcium phosphate.
Main Methods:
- X-ray photoelectron spectroscopy (XPS) for adsorption isotherms and quantification.
- Time-of-flight secondary ion mass spectrometry (ToF-SIMS) for structural analysis of adsorbed BSA.
- Development of a hydrophobic/hydrophilic residue intensity ratio for quantitative structural comparison.
Main Results:
- BSA formed a monolayer on all three CaP surfaces.
- ToF-SIMS revealed intensity differences in hydrophobic and hydrophilic amino acid-derived ions.
- A statistically significant 7% increase in the hydrophobic/hydrophilic ratio was observed for BSA on hydroxyapatite versus dibasic calcium phosphate dihydrate.
Conclusions:
- Surface binding induces structural changes in BSA.
- Differences in BSA structure correlate with the specific CaP phase.
- The developed ratio offers a quantitative approach to assess protein structural modifications on biomaterial surfaces.
