Solid-state NMR study of discrete environments of bone mineral nanoparticles using phosphorus-31 relaxation

Bone mineral nanoparticles, residing between collagenous fibres, contain a crystalline apatite core (CAC) covered by an amorphous hydrated surface layer (AHSL). The main objectives of this work were to characterize the nanoparticles of human bone mineral and their discrete CAC and AHSL regions and relate this information to bone diseases. This pilot study involved 18 postmenopausal women suffering from osteoarthritis together with osteoporosis or osteopenia. Trabecular tissue specimens were acquired from the femoral intertrochanteric region during total hip arthroplasty. The specimens of whole bone were examined by P-31 solid-state NMR (ssNMR) to measure the concentration ratio of phosphorus in the AHSL and CAC locations, together with their P-31 linewidths and spin-lattice relaxation times. It was found that the AHSL region of the studied specimens contained 13-24% apatite phosphorus. The magnitude, hydration and structural order of AHSL and CAC were dependent on the progress of the pertinent diseases. Thus, the P-31 ssNMR spectroscopy can be used ex vivo to selectively analyse the discrete nanoapatite environments in whole bone specimens and possibly assist in postoperative medical diagnostics. (C) 2016 Faculty of Health and Social Sciences, University of South Bohemia in Ceske Budejovice. Published by Elsevier Sp. z o. o. All rights reserved.