Abstract
Ionic substitutions within the hydroxyapatite lattice are a widely used approach to mimic the chemical composition of the bone mineral. In this work, Sr-substituted and Mg- and Sr-co-substituted calcium phosphate (CaP) scaffolds, with various levels of strontium and magnesium substitution, were prepared using the hydrothermal method at 200 °C. Calcium carbonate skeletons of cuttlefish bone, ammonium dihydrogenphosphate (NH4H2PO4), strontium nitrate (Sr(NO3)2), and magnesium perchlorate (Mg(ClO4)2) were used as reagents. Materials were characterized by means of X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). Whole powder pattern decomposition refinements of XRD data indicated that increased magnesium content in the Mg- and Sr-co-substituted scaffolds was related to an increased proportion of the whitlockite (WH) phase in the biphasic hydroxyapatite (HAp)/WH scaffolds. In addition, refinements indicate that Sr2+ ions have replaced Ca2+ sites in the WH phase. Furthermore, PCL-coated Mg-substituted and Sr- and Mg-co-substituted scaffolds, with the HAp:WH wt. ratio of 90:10 were prepared by vacuum impregnation. Results of compression tests showed a positive impact of the WH phase and PCL coating on the mechanical properties of scaffolds. Human mesenchymal stem cells (hMSCs) were cultured on composite scaffolds in an osteogenic medium for 21 days. Immunohistochemical staining showed that Mg-Sr-CaP/PCL scaffold exhibited higher expression of collagen type I than the Mg-CaP/PCL scaffold, indicating the positive effect of Sr2+ ions on the differentiation of hMSCs, in concordance with histology results. Reverse transcription-quantitative polymerase chain reaction (RT-qPCR) analysis confirmed an early stage of osteogenic differentiation.
Highlights
Synthetic calcium phosphates (CaPs), in particular hydroxyapatite (HAp, Ca10 (PO4 )6(OH)2, Ca/P = 1.667), are the most commonly used ceramics in dentistry, orthopedics and bone tissue engineering
After 21 days of osteogenic differentiation, the ion substituted composite scaffolds were removed from the culture medium and prepared sections were incubated with primary antibody and the signal was detected with EnVision Detection Systems Peroxidase/DAB, Rabbit/Mouse (Dako, Glostrup, Denmark), according to the manufacturer instructions
Rietveld of refinement analysis performed on X-ray diffraction (XRD) patterns of all in
Summary
Synthetic calcium phosphates (CaPs), in particular hydroxyapatite (HAp, Ca10 (PO4 ). Natural bone mineral differs from stoichiometric hydroxyapatite owing to the anionic and/or cationic substitutions within the apatite lattice For this reason, today, ionic substitutions within the apatite lattice are one of the most widely used approaches to mimic the chemical composition of the bone mineral and to improve the biological performance of calcium phosphate materials. Aina et al [20] synthesized magnesium- and strontium-co-substituted hydroxyapatite by an aqueous precipitation method They obtained biphasic calcium phosphates (BCPs) with variable HAp/β-tricalcium phosphate (β-Ca3 (PO4 ) , β-TCP) ratios. Considering the importance of Sr2+ and Mg2+ in the bone growth process, a further focus on the effect of Sr and Mg co-substitution on the structural, mechanical and biological properties of calcium phosphate ceramics are of great interest. The effect of ion substitution and the polymer coating on the mechanical and biological properties of the composite scaffolds has been investigated
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
