ABSTRACT
The seek of bioactive materials for promoting bone regeneration is a challenging and long-term task. Functionalization with inorganic metal ions or drug molecules is considered effective strategies to improve the bioactivity of various existing biomaterials. Herein, amorphous calcium magnesium phosphate (ACMP) nanoparticles and simvastatin (SIM)-loaded ACMP (ACMP/SIM) nanocomposites were developed via a simple co-precipitation strategy. The physiochemical property of ACMP/SIM was explored using transmission electron microscope (TEM), Fourier transform infrared spectroscopy (FTIR), powder X-ray diffraction (XRD) and high-performance liquid chromatograph (HPLC), and the role of Mg2+ in the formation of ACMP/SIM was revealed using X-ray absorption near-edge structure (XANES). After that, the transformation process of ACMP/SIM in simulated body fluid (SBF) was also tracked to simulate and explore the in vivo mineralization performance of materials. We find that ACMP/SIM releases ions of Ca2+, Mg2+ and PO 4 3 - , when it is immersed in SBF at 37°C, and a phase transformation occurred during which the initially amorphous ACMP turns into self-assembled hydroxyapatite (HAP). Furthermore, ACMP/SIM displays high cytocompatibility and promotes the proliferation and osteogenic differentiation of MC3T3-E1 cells. For the in vivo studies, lamellar ACMP/SIM/Collagen scaffolds with aligned pore structures were prepared and used to repair a rat defect model in calvaria. ACMP/SIM/Collagen scaffolds show a positive effect in promoting the regeneration of calvaria defect after 12 weeks. The bioactive ACMP/SIM nanocomposites are promising as bone repair materials. Considering the facile preparation process and superior in vitro/vivo bioactivity, the as-prepared ACMP/SIM would be a potential candidate for bone related biomedical applications.
ABSTRACT
Electronic structure and bioactivity of calcium phosphate (CaP) coatings on Ti-based anodic nanotubes are investigated. Nanotubes on pure Ti and Ti-6Al-4V alloy, respectively, are used as substrates for CaP deposition. The CaP coatings are formed by first growing a seeding CaP layer using alternative immersion (AIM) treatment followed by crystallization in Dulbecco's phosphate-buffered saline (DPBS). CaP coatings formed on both Ti and Ti-6Al-4V substrates are found containing a variety of bioactive CaP species, such as hydroxyapatite (HA), amorphous CaP (ACP), octacalcium phosphate (OCP), and dicalcium phosphate dihydrate (DCPD). The compositions of the coatings during the nucleation and crystallization processes are tracked and analyzed using X-ray absorption near-edge structure (XANES). The variation of CaP species in the resulted coatings are found strongly dependent on the choice of metal substrates, which leads to different bioactivities. By comparing the proliferation and differentiation of osteoblast cells (MC3T3-E1) on the CaP coatings, correlations between CaP species and their bioactivities are established.
Subject(s)
Calcium Phosphates/chemistry , Coated Materials, Biocompatible/chemistry , Nanotubes/chemistry , Oxides/chemistry , Titanium/chemistry , 3T3 Cells , Alloys , Animals , Calcium Phosphates/pharmacology , Cell Differentiation/drug effects , Cell Line , Cell Proliferation/drug effects , Crystallization/methods , Durapatite/chemistry , Materials Testing/methods , Mice , Osteoblasts/drug effects , Surface Properties/drug effects , Tensile Strength/drug effectsABSTRACT
Inorganic lead halide perovskite CsPbX3 (X = Cl, Br, or I) nanocrystals are promising candidate materials for light-emitting devices and optoelectronics. Mn-Doped CsPbX3 is of particular interest, as the Mn-doping introduces an additional emission band, making this material a promising white-light emitter. In this study, Mn-doped CsPb(Br/Cl)3 nanocrystals are prepared at room-temperature and ambient pressure. The chemical environment of Mn, and the luminescence of these nanocrystals are analyzed in detail using X-ray diffraction (XRD), extended X-ray absorption fine structure (EXAFS), X-ray absorption near-edge structure (XANES) and X-ray excited optical luminescence (XEOL). Although the introduction of Mn does not alter the long-range order of the CsPbX3 crystal, it leads to a local lattice contraction with the bond length of Mn-X much shorter than Pb-X. We also find excitation energy-dependence in both the intensity and wavelength of the perovskite excitonic emission band, while only in intensity of the Mn emission band. Detailed fitting of the XEOL reveals that the perovskite emission band is dual-channel, and it is the excitation energy-dependent intensity variation of these two channels that drives the observed red-shift of the combined emission band. Our findings also confirm that the Mn emission band is driven by exciton-Mn energy transfer and clarify the Mn chemical environment and the luminescence mechanism in Mn-doped CsPb(Br/Cl)3 nanocrystals.