gms | German Medical Science

We have investigated rabbit bone samples by ³¹P and ¹³C solid state NMR spectroscopy in order to understand the molecular organization of the major organic and inorganic molecular components of bone, collagen type I and calcium-hydroxyapatite. High resolution of the solid-state NMR spectra is obtained by magic angle spinning. The ³¹P spectra of bone specimen show a single line characteristic for calcium-hydroxyapatite. ¹³C CPMAS NMR spectra show the characteristic signatures of collagen type I with good resolution for all major amino acids in collagen (alanine, glycine, proline, and hydroxyproline). Quantitative measurements of ¹³C-¹H dipolar couplings indicate that the collagen segments are very rigid with only small amplitude motions with correlation times in the nanosecond range. These quantitative investigations of natural bone may provide the basis for a quality control of all osteoinductive bone substitutes. If the artificial material is well adapted into the bone, collagen type I and calcium-hydroxyapatite should be detectable by the NMR technique. To test this idea, an animal study is currently carried out. From the ³¹P NMR spectra, ß-tricalcium phosphate and calcium-hydroxyapatite can be distinguished quantitatively. This should allow to record the formation of natural bone material. Further, ¹³C CPMAS spectra should allow to detect collagen type I that has been produced from the cells. Comparison with the spectroscopic date from natural bone should allow to assess the quality of the bone substitute material.