Characterization of Sr-substituted hydroxyapatite thin film by sputtering technique from mixture targets of hydroxyapatite and strontium apatite

Abstract

Sr-substituted hydroxyapatite thin films were prepared by sputtering technique from mixture targets of hydroxyapatite (HA) and strontium apatite (SrAp). The HA and SrAp powders were mixed at 0-100% Sr/(Sr + Ca) target ratios. The coated films were recrystallized by a hydrothermal treatment to reduce film dissolution. The films were then characterized by X-ray diffractometry (XRD), scanning electron microscopy (SEM) and inductively coupled plasma atomic emission spectrometry (ICP). The osteocompatiblity of the films was also evaluated by the size of the bone formation area in osteoblast cells.In the XRD patterns, peaks shifted to lower 2θ values with increasing Sr/(Sr + Ca) target ratios, which indicated Sr incorporation into the HA lattice. In the SEM observation of the hydrothermally treated films, the surface was covered with globular particles, and the size of the globular particles increased from Sr0 to Sr40, and then the size decreased from Sr60 to Sr100. The ICP analysis showed that the Sr/(Sr + Ca) film ratios were almost the same as the target ratios. In the cell culture, the bone formation area on the Sr-substituted HA films increased with increasing Sr concentration, and saturated at Sr60.

Chitosan/hydroxyapatite composite bone tissue engineering scaffolds with dual and decoupled therapeutic ion delivery: copper and strontium

“…50 In particular, Sr-HA samples were characterized by general peak broadening and shifts in low 2y angle peaks, which are typical evidences of ion substitution. 49 The analysis by FTIR further confirmed the findings of the XRD analyses: typical peaks and bands of phosphate and hydroxyl vibrations were detected both in HA and Sr-HA. In addition, a minor signal that can be ascribed to carbonate impurities was also identified.…”

“…As Sr 2+ ions (ionic radius 1.18 Å) are substituted at Ca 2+ (0.99 Å) sites in the HA lattice structure, expansion in the unit cell occurs, which consequently results in peak broadening as well as slight shifting in peak position. 49 Lattice parameters obtained using Bruker's TOPAS software confirmed this observation. The software showed that the a-axis and c-axis parameters of Sr-HA were increased after the substitution of Sr 2+ , as presented in Table 3.…”

“…50 In addition, a slight shift in diffraction peaks towards lower angles (2y), as compared to reference HA peaks, was observed, which can be ascribed to the substitution of calcium ions by strontium ions. 49 3.2.2 Functional group analysis by FTIR. The FTIR spectra of HA and Sr-HA are presented in Fig.…”

A Review on Ionic Substitutions in Hydroxyapatite Thin Films: Towards Complete Biomimetism

“…Sr-HA has been deposited both by Sr-HA targets with variable Sr/(Sr + Ca) ratio and by co-deposition from different targets. Deposition on titanium alloys and silicon has been reported [1,24,38,43]. Interestingly, the content of Sr was found to influence sputtering rate.…”

“…From a biological point of view, Sr increases the mechanical strength of bone [21] and has an anti-osteoporotic effect [19][20][21]. In fact, strontium ranelate, a strontium-based drug used against osteoporosis, can boost osteoblast activity while inhibiting osteoclasts [20,21,24,37,38,42,43]. Sr capability to improve bone regeneration has also been demonstrated by tests in vivo [17,20,37,38,42].…”