Crystalline Hydroxyapatite Research Articles

Comparison of the expansion behavior of atoms and droplets ablated from a β-tricalcium phosphate target under low-pressure ambient H2O gas for hydroxyapatite coating

Visualizing the expansion of particles of different size in a laser-ablated plume is useful for understanding the mechanism of the pulsed-laser deposition process. In our previous work that the crystalline hydroxyapatite content in a coating layer decreased with increasing H2O gas pressure. We concluded that ablated atoms and ions, which were immediately changed into crystalline hydroxyapatite, were stopped before reaching the substrate in the H2O pressure range. In the present study, the expansion behavior of ablated droplets and atoms in H2O gas was measured independently. Droplets were also measured via Mie scattering images using a second probe laser beam and were found to not be affected by the ambient gas pressure. However, the excited Ca atoms and ions in this H2O pressure range were effectively prevented from reaching the substrate. These confirm that the decrease in the crystalline hydroxyapatite content was caused by the increase in the ambient gas pressure.

Natural Adsorbent Made from Eggshells for Removal of Chromium (VI) in Water

Substantial utilization of heavy metals in various industrial processes nowadays had cause heavy metal pollutions in the water. Hexavalent chromium, Cr (VI), is one of the heavy metals which has been extensively used in alloy pigment production and surface treatment. The present work reports natural adsorbent synthesis made from eggshell to reduce Cr (VI) in water. The eggshell adsorbents were prepared by several steps that include boiling, drying, calcination at 900 °C, grinding, pH adjustment, precipitation, and filtration. XRD results displayed a highly crystalline hydroxyapatite (HAp) peak that was successfully synthesized. FESEM analysis showed the morphology of the powder that was agglomerate with irregular cloud-like shapes, while EDS results presented the elements in the eggshell powders that include calcium (Ca), phosphorus (P), and oxygen (O). FTIR analysis revealed the presence of hydroxyl group (OH-) that contribute to the adsorption process. The adsorption experiment demonstrates the highest Cr (VI) removal and adsorption capacity of 70% and 285.71 mg/g, respectively, was attained by 6 g adsorbent dosage within 1 hour. Kinetic studies of the adsorption process were best described by the pseudo-second-order model and Langmuir isotherm model with a high correlation coefficient of 0.98. This work's findings suggested that eggshells are potential natural adsorbent to reduce heavy metal pollutions, specifically Cr(VI) in water.

Direct growth of structurally controllable hydroxyapatite coating on Ti-6Al-4V through a rapid hydrothermal synthesis

Titanium alloys have been used as an implant material for many years due to their high ductility, high strength, excellent corrosion resistance and better biocompatibility. However, this biomaterial as an implant still requires the functionally bioactive surface coating to improve the osseointegration between the implant and bone tissue. Herein, we develop a facile hydrothermal synthesis of using the mixture of calcium hydroxide and sodium tripolyphosphate to directly form a structurally tunable hydroxyapatite coating on the Ti-6Al-4V surface. The result shows that the structure of hydroxyapatite can be readily controlled by modifying the Ti-6Al-4V surface with TiO2 via a short heat treatment. The treated Ti-6Al-4V can provide the rapid growth of hydroxyapatite fibers to form a porous structure interwoven with wire-like shapes in comparison with untreated Ti-6Al-4V presenting needle-like shapes. This structural difference results from the formation of TiO2 assisting in initial nucleation of hydrothermal hydroxyapatite growth. The bioactivity result reveals a better proliferation rate on the wire-like sample is enabled to correlate with the porous structure, crystallinity, and wettability of hydroxyapatite. Our results here not only indicate the feasibility of a structurally controllable hydroxyapatite through a rapid hydrothermal synthesis but also provide insights into optimizing preferred structures on implant surfaces.

Optimization of permanently polarized hydroxyapatite catalyst. Implications for the electrophotosynthesis of amino acids by nitrogen and carbon fixation

The enhanced catalytic activity of permanently polarized hydroxyapatite, which is achieved using a thermally stimulated polarization process, largely depends on both the experimental conditions used to prepare crystalline hydroxyapatite from its calcium and phosphate precursors and the polarization process parameters. A mineral similar to brushite, which is an apatitic phase that can evolve to hydroxyapatite, is found at the surface of highly crystalline hydroxyapatite. It appears after chemical precipitation and hydrothermal treatment performed at 150 °C for 24 h followed by a sinterization at 1000 °C and a polarization treatment by applying a voltage of 500 V at high temperature. Both the high crystallinity and the presence of brushite-like phase on the electrophotocatalyst affect the nitrogen and carbon fixation under mild reaction conditions (95 °C and 6 bar) and the synthesis of glycine and alanine from a simple gas mixture containing N2, CO2, CH4 and H2O. Thus, the Gly/Ala ratio can be customized by controlling the presence of brushite on the surface of the catalyst, enabling to develop new strategies to regulate the production of amino acids by nitrogen and carbon fixation.

Comparative investigation of hydroxyapatite coatings formed on titanium via phosphate chemical conversion

Phosphate chemical conversion coatings have attracted much attention on surface modification of metallic implant, due to their in-situ growth pattern and good mechanical performances. Nevertheless, it is difficult to use this method for preparing a pure hydroxyapatite (HA) coating. In this study, a pure HA coating was prepared on titanium (Ti) in an acidic phosphate aqueous via a simple single-step chemical conversion without alkali post-treatment. The microstructure, chemical composition, electrochemical and mechanical performances of the HA coating were characterized in comparison with those of a precursor dicalcium phosphate (CaP) coating which was alkali post-treated (CaP-OH). Results revealed that the one-step chemically converted HA coating was homogeneously nano-structured with higher phase purity and crystallinity. Moreover, the HA coating was thicker (~6.5 μm) than the CaP-OH one (~40 μm) but with better mechanical properties and corrosion resistance. The results encouraged the direct preparation of crystalline HA coating with superior properties on surface of Ti via a single-step phosphate chemical conversion.

Effect of chitosan reinforcement on properties of hydroxyapatite/silk fibroin composite for biomedical application

In this study we reported the synthesis of biocompatible Hydroxyapatite (HAP)/Silk Fibroin (SF)/Chitosan (CT) composite by using In-situ co-precipitation method. Trace of carbonated hydroxyapatite with low crystallinity serves as a promising platform for the growth of bone tissue and were confirmed using Fourier Transfer Infrared (FTIR) spectroscopy, which is in accordance with X-Ray Diffraction (XRD) results. In-vitro bioactivity of the composite was analysed by treating it with Simulated Body Fluid (SBF) solution for two consecutive weeks. A maximum degradation rate of 30.28 ± 0.57% was observed for the first week and 23.89 ± 0.58% for the latter week, which confirms the increase in mineralization of the composite. The cytotoxicity of the composite was assessed using MTT-assay countered to MG-63 osteoblast like cell line, which reveals that all the composites are less toxic. Dependence of the antibacterial effect of composite on the type of bacteria were examined which reflects the better antibacterial activity of the composite to Gram-negative than Gram-positive. The potential of the 40% HAP- 30% SF- 30% CT composite (HSC-3) as a promising candidate for bone tissue engineering could be further confirmed from the future in-vivo studies for which the findings in the present study remains supportive. • A cross-linked HAP/SF/Chitosan composite was fabricated by in-situ co-precipitation route. • Polymer matrix could control the crystallinity of HAP. • Chitosan content could accelerate the bioactivity of the composite. • The prepared biomimetic composite can be used as a potential bone graft material.

Preparation and Characterization of Crystalline Hydroxyapatite Induced by Self‐Assembled Peptide and the Potential Application in Remineralizing Dentin

The generation of mineral crystals on the implant surface under physiological conditions is an efficient way to repair defects in hard tissues. However, there is still a challenge to mimic the complicated structure of hard tissue with well bonding stability. Herein, a peptide sequence: Leu–Asp–Asp–Try–Glu–Glu–Ser–Cys is designed. The peptide forms a self‐assembled peptide (SAP) coating at the solid/water interface via a facile and rapid process. The abundant functional groups on the SAP coating can be utilized to bind with calcium ions trough chelation, which may facilitate the formation of c‐axis hydroxyapatite crystals. Owing to the amyloid adhesion properties, a c‐axis hydroxyapatite layer with low wear extent and well bonding robustness can be integrated with virtually arbitrary material irrespective of their size and morphology, even hard tissues such as dentin. This suggests that the facile process may hold a great potential application in repairing hard tissue and designing complex materials.

Biogenic hydroxyapatite powders: Effects of source and processing methodologies on physicochemical properties and bioactive response

This study compares and analyzes the biogenic hydroxyapatite (BHAp) powders obtained from bovine and porcine bones using two methodologies to determine the influence of the obtention process on BHAp properties. Despite the differences between the processing methods, the results obtained suggest that the thermal-treatment has a meaningful influence on physicochemical properties. Since the thermal-treatments performed (1100 °C for 2 h and 800 °C for 24 h for A- and B-methods, respectively) resulted in a hydroxyapatite crystalline phase formation as the main phase with the presence of magnesium oxide (MgO) as a secondary phase in both methods and calcium oxide (CaO) in samples obtained by A-method. The B-method samples also present higher carbonate group content (CO32−) and A- and B-type substitutions compared to the A-method. We found that the carbonate groups' changes can be mainly attributed to the thermal-treatment temperature. Subsequently, the BHAp samples were immersed in Hank Solution for 3, 7, 14, 21, and 28 days to study the bioactive response. We found a bone-like apatite layer formation on the surface as a function of the soaking time in all sets of samples, as was expected. However, we also found a calcite layer grown on the surface of the samples prepared by the B-method, which is associated with the carbonate ions release from these samples to the solution. Finally, a formation mechanism of calcite in samples obtained through the B-method during the exposure to Hank's solution is also proposed.”

Bioactivity of microporous borate glass-ceramics prepared from solution and derived glasses

Microporous borate compositions based on the formula xB2O3•(100–x)(0.5CaO•0.45Na2O•0.05P2O5) (x = 56.1 and 51.1 mol%) have been prepared from solution. The dried products were subjected to heat-treatment at 600 and 700 °C for 3 h to obtain borate glass-ceramics with scaffold-like structure. Bioactivity and degradation were tested in simulated body fluid (SBF) at 37 °C for different time intervals. Scanning (SEM) and transmission (TEM) electron microscopy, infrared spectroscopy (FTIR) and X-ray diffraction (XRD) were used to examine the correlation between bioactivity and microstructure. Results indicated that the type and concentration of crystalline CaNaB5O9 and CaNa3B5O10 phases, in addition to concentration of bridging and non-bridging oxygen atoms, are the factors affecting the apatite forming ability and composition degradation. XRD and SEM results showed that the as-prepared compositions and those heat-treated at 600 and 700 °C are crystalline matrices, while TEM-EDP of selected region exhibited halo diffuse intensity with clear bright spots. These features indicate that the crystalline phases are dispersed in amorphous phase. After immersion in SBF, TEM-EDP proved that the crystalline hydroxyapatite (HA) phase was formed on amorphous phase. The type of product after reaction in SBF is influenced by the nature of borate network. For melt-derived borate glasses, hydrous species of B(OH)3 and amorphous calcium phosphate are formed. Microporous borate glass-ceramics exhibited a good in vitro bioactive response through the formation of hydroxyapatite, except when the matrix is rich in CaNa3B5O10 phase. The results of this study suggest that the solution-method can be used to prepare microporous bioactive borate glass-ceramics, such as three-dimensional porous scaffolds, which are of particular interest for the clinical application in bone regeneration.

Characterization and In Vitro Evaluations of Injectable Calcium Phosphate Cement Doped with Magnesium and Strontium.

Injectable calcium phosphate cement is a promising biomaterial for hard tissue repair due to its osteoinductivity, biocompatibility properties, and its use to correct defect areas involving narrow cavities with limited accessibility by the minimally invasive technique. Microwave-synthesized hydroxyapatite (HA) was used for the preparation of cement. In recent years, both magnesium and strontium calcium phosphate cements have exhibited rapid setting, improved mechanical strength, and a good resorption rate. A big step still remains to develop injectable magnesium and strontium phosphate cements with ideal self-setting properties, adequate mechanical strength, and good biocompatibility for clinical applications. In this study, both magnesium and strontium were doped with synthesized semiamorphous and crystalline hydroxyapatite (HA). The powder mixture was mixed with Na2HPO4, NaH2PO4, and a carboxymethyl cellulose (CMC) solution to develop the novel magnesium and strontium calcium phosphate cement. The setting time, physiochemical properties of hardened cement, microstructure, mechanical strength, and injectability of the prepared cement were studied. The toxicity evaluation and cell adhesion, which are necessary to identify the suitability of the material for different applications, were quantified and investigated using fibroblast cells. The setting time of cement was reduced substantially for magnesium- or strontium-doped cement by 2 min. The phase composition of the hardened cement expresses the semiamorphous or crystalline phase of HA with additives. Smooth and complete injection of cement paste was observed in semiamorphous HA-based cement. The intercellular reactive oxygen stress (ROS) of the Sr2+-doped cement sample showed varied degrees of toxicity to cells in terms of different concentrations. The Mg2+-doped cement showed significant attachment of cells after treatment at varying incubation times.

Isolation and characterization of hydroxyapatite powder from the scale of freshwater fish Labeo rohita using green technology

The objective of the present work was to isolate and characterize hydroxyapatite (HAP) from Labeo rohita scale using green technology. The method used only 0.6% KOH solution for isolation, which did not generate any spent liquid for disposal to the environment. Investigation through thermogravimetric analysis, X-ray diffraction study, scanning electron microscopy, energy-dispersive X-ray spectroscopy, and particle size distribution measurement was carried out for characterization of HAP. The powder after isolation from scale contained < 7% organic matter and could be converted to thermally stable perfectly crystalline pure HAP without any organic impurity by exposition to 1000 °C for only 1 h. The heated HAP powder had a Ca:P ratio of 1.52 and indicated the grains to be in submicron size but remaining in soft agglomerated condition with 50% of the mass passing through ≈ 167 µm.

Synthesis and characterization of non-stoichiometric hydroxyapatite nanoparticles using unmodified and modified starches

Non-stoichiometric hydroxyapatite (HAp) presents an additional phase in its structure due to calcium or phosphorus excess, which can influence the material’s mechanical properties, as well as its bioactivity and biodegradability. While stoichiometric HAp, with calcium to phosphorus ratio (Ca/P) of 1.67, has been widely investigated, only a few studies have reported the synthesis of HAp with higher Ca/P ratio. In this work, non-stoichiometric HAp nanoparticles were synthesized using chemical precipitation method followed by a calcination protocol. In order to achieve better process control with chemical precipitation, starch, a natural additive, was applied. Three types of starch were selected for comparison: nonionic starch (NS), soluble starch (SS), and cationic starch (CS). Infrared spectroscopy and chemical analysis results confirmed the non-stoichiometric profile of the synthesized HAp, with a 1.98 Ca/P ratio. X-ray diffraction (XRD) results showed that HAp and calcium oxide (CaO) crystalline phases were obtained and no residual starch was detected. Rietveld refinements confirmed that, for all three types of starch, the content of crystalline HAp was greater than 96.5% and the unit cell volume was not affected. Scanning electron microscopy (SEM) showed agglomeration of particles. Nanoparticle tracking analysis (NTA) results demonstrated that the use of SS produced the smallest particles (approximately 60nm).

Synthesis and characterization of plasma sprayed functional gradient bioceramic coating for medical implant applications

The dissolution of plasma-sprayed hydroxyapatite (HA) coating in physiological media is complex and involves numerous factors. It is generally believed that the highly crystalline HA coatings are beneficial for long-term stability, whereas amorphous layers dissolve more quickly and promote early biointegration. In the present study, the functionally gradient coating (FGC) was formulated in three successive layers over Ti6Al4V alloy using an atmospheric plasma spray (APS) process. At the inner layer, the titania (TiO2) bond coat is applied to enhance adhesion strength. In the middle layer, crystalline hydroxyapatite (HA) coating was deposited to provide long-term stability. In contrast, the outer amorphous layer of as-sprayed HA coating was assumed to promote the early implant bonding with host bone. The crystallinity level of the middle HA layer was increased by post coating heat treatment at 700̊ C for 1 h. There is an improvement in microhardness value after heat treatment from 276.6 ± 91.2 HV to 316.3 ± 41.4 HV. The corresponding porosity and surface roughness values decreased from 15 to 11% and 5.81 ± 1.00 to 5.22 ± 0.84 μm, respectively. In addition, the post coating heat treatment of the middle layer minimized the plasma spray process defects, such as micro-cracks and voids. Furthermore, a corrosion study in the ringer solution shows that heat treatment effectively enhanced the corrosion resistance of the middle crystalline HA layer. Nevertheless, the TiO2 bond coat enhanced the adhesion strength of functional gradient coating from 21.70 MPa to 30.50 MPa. The findings of this study indicate that surface modification with functional gradient coating is a promising approach to improve the performance of the Ti6Al4V alloy for biomedical applications.

Diagenetic processes in Quaternary fossil bones from tropical limestone caves

Quaternary fossils from limestone caves bear various diagenetic features due to the complex nature of sedimentary processes. However, few studies have addressed the problem of diagenetic changes in fossils from tropical-wet environments. We study Quaternary fossil bones from different sites of a tropical limestone cave in northeastern Brazil. These fossils show diverse diagenetic features. The approach encompassed the use of scanning electron microscopy, Raman spectroscopy, and X-ray diffraction to understand the modification of the fossil bone structure, chemical composition, and mineral assemblage during the diagenesis processes. We describe a model for fossil diagenesis in tropical limestone caves that involves early and advanced diagenetic stages, which produce two routes with different endmembers. The diagenesis in the cave alters the crystallinity and ordering of hydroxyapatite. The recrystallization of hydroxyapatite appears to be strongly influenced by dripping water that is rich in calcium carbonate, which leads to crystal formation with higher crystallinity. In the absence of calcium carbonate, hydroxyapatite diagenesis involves crystal growth but not necessarily dissolution of the original material, which enables remarkable preservation of the biological structure.

Enhanced osteogenesis properties of titanium implant materials by highly uniform mesoporous thin films of hydroxyapatite and titania intermediate layer.

Titanium (Ti) has been widely used for medical and dental applications; however, bare Ti cannot be properly connected to a living bone, and hence some modifications are needed for this purpose. The present study describes the synthesis of mesoporous hydroxyapatite thin films (MHF) on titanium implant materials for speeding up and shortening the processes of osteointegration. The uniform MHF was coated on a Ti substrate following the insertion of intermediate titania (TiO2) film via the sol-gel dip-coating method. The intermediate titania layer improved the bonding strength between the MHF and Ti substrate. MHFs were synthesized using a precursor solution containing phosphoric acid, calcium nitrate tetrahydrate, and a nonionic surfactant (C12E10) as the phosphate source, calcium source, and structure-directing agent, respectively. The effect of calcination temperature on phase composition, morphology, microstructure, roughness, and wettability of the MHFs was investigated using XRD, FE-SEM, COM, AFM, and contact angle measurement. The XRD results revealed the crystalline hydroxyapatite phase, which was improved with an increase in the calcination temperature. Moreover, the FE-SEM images showed the crack-free MHFs, uniform thickness of the layer, and mesoporous surface morphology. In addition, it was found that the roughness and wettability of the samples change upon the alteration of calcination temperature. The biological studies demonstrated that MHFs support the adhesion and proliferation of the mesenchymal stem cells (MSCs) and guid them toward osteogenic differentiation. Therefore, the MHFs prepared in this study may be useful in a wide range of applications, particularly in bone regeneration medicine.

Thermal conversion of fish bones into fertilizers and biostimulants for plant growth – A low tech valorization process for the development of circular economy in least developed countries

Local food production systems of least developed countries (LDCs) are more vulnerable to environmental factors, such as climate change, with respect to those of developed ones. Hence, the development of low-tech processes to empower LDCs adaptive capacity through a circular economy approach is very promising. Here, we report on a straightforward process for potential application in LDCs contexts based on the thermal conversion of fishery by-products (fish bone) into calcium phosphate-based materials with application as fertilizers and biostimulants. Sardinella aurita bones collected from artisanal ports in Senegal were calcined in air at 300 °C, 600 °C and 900 °C. The sample obtained at 300 °C was a composite material made of an organic part, deriving from the uncomplete combustion of fish bone collagen and fatty acid, and an inorganic part made of very poorly crystalline hydroxyapatite. The other two samples obtained at 600 °C and 900 °C had a negligible content of organic matter, and consisted of hydroxyapatite and β-TCP. Materials phytotoxicity was tested against Lepidium sativum seed, and their bio-stimulation activity was assayed on Zea mais seedlings and coleoptiles. All the materials showed promising results in terms of seed germination, plant fertilization and corn coleoptile biostimulation. Finally, we briefly analyzed the environmental impacts and economic cost of the proposed low-tech thermal process to confirm its large-scale applicability in LDCs for the conversion of fish bones into valuable products.

Controlled Rate Thermal Analysis (CRTA) as a Fast and Effective Method for the Development of Ceramic Powders of Synthetic Hydroxyapatite at Low Temperatures

One of the main limitations for applying synthetic hydroxyapatite as a filler in cement and other formulations in orthopedic surgery is its morphology. The present work shows the obtaining of synthetic hydroxyapatite powders at low temperatures such as 300 and 850ºC using the Controlled Rate Thermal Analysis (CRTA) technique. The powders obtained were characterized by IR spectroscopy and X-ray diffraction, showing that the phase formed corresponds to crystalline hydroxyapatite. The specific surface area values determined are between 17 and 66 m2/g with a pore size between 50-300 Å. The transformation of phases in the synthetic hydroxyapatite is studied by Dynamic Thermogravimetric Analysis and CRTA techniques, allowing the kinetic calculations of the transformation using two methods of data processing, determining the activation energy (Ea), pre-exponential factor (A), and model kinetic most likely in each stage. The results show the effectiveness and usefulness of the CRTA technique for preparing synthetic hydroxyapatite powders with different specific surface areas, which makes this technique attractive for medical purposes.

Isotope Microscopic Observation of Osteogenesis Process Forming Robust Bonding of Double Network Hydrogel to Bone.

Tough double network (DN) hydrogels are promising substitutes of soft supporting tissues such as cartilage and ligaments. For such applications, it is indispensable to robustly fix the hydrogels to bones with medically feasible methods. Recently, robustly bonding the DN hydrogels to defected bones of rabbits in vivo has been proved successful. The low crystalline hydroxyapatite (HAp) of calcium-phosphate-hydroxide salt coated on the surface layer of the DN hydrogels induced spontaneous osteogenesis penetrating into the semi-permeable hydrogels to form a gel/bone composite layer. In this work, the 44 Ca isotope-doped HAp/DN hydrogel is implanted in a defect of rabbit femoral bone and the dynamic osteogenesis process at the gel/bone interface is analyzed by tracing the calcium isotope ratio using isotope microscopy. The synthetic HAp hybridized on the surface layer of DN gel dissolves rapidly in the first two weeks by inflammation, and then the immature bone with a gradient structure starts to form in the gel region, reutilizing the dissolved Ca ions. These results reveal, for the first time, that synthetic HAp is reutilized for osteogenesis. These facts help to understand the lifetime of bone absorbable materials and to elucidate the mechanism of spontaneous, non-toxic, but strong fixation of hydrogels to bones.

Enhanced corrosion protection of NiTi orthopedic implants by highly crystalline hydroxyapatite deposited by spin coating: The importance of pre-treatment

NiTi shape memory alloy has found broad applications in orthopedics and dentistry due to its superelasticity, shape memory effect, high corrosion performance, and biocompatibility. New horizons for biomedical applications of NiTi can be opened by improving its corrosion resistance and surface characteristics. The corrosion resistance and biological characteristics of NiTi can be improved by appropriate pre-treatments, such as mechanical polishing, acid chemical etching followed by immersion in an alkali solution and heat treatment, followed by the deposition of a nano-HAp layer by sol-gel spin coating. To deposit a highly crystalline nano-HAp coating, the synthesized HAp coatings were calcined in the temperature range 400–600 °C and the further investigations were carried out on an optimum coating of HAp calcined at 600 °C. Results indicated that the type of pre-treatment influenced the final properties of coated NiTi. While heat-treated NiTi resulted in superior corrosion behavior and in-vitro bioactivity, NiTi treated by acid etching followed by immersion in an alkali solution provided the highest hydrophilicity. The contact angle of water on the HAp-coated, heat treated NiTi was 21% lower than that on mechanically polished NiTi. The HAp coating enhanced the final characteristics of pre-treated NiTi irrespective of the type of pre-treatment. A decrease of 75% in Ni2+ ion release and a 212% increase in polarization resistance for HAp-coated, heat treated NiTi showed its superior corrosion resistance in Ringer's solution at 37 °C under static conditions, compared to mechanically polished NiTi.

TOFSIMS and XPS characterisation of strontium in amorphous calcium phosphate sputter deposited coatings

Strontium (Sr) substituted calcium phosphate (CaP) coatings have stimulated a lot of interest as Sr is known to provide osteoconductive properties. Most of the work to date with respect to Sr substituted coatings has focused on the creation of crystalline Sr-substituted hydroxyapatite (HA), as opposed to amorphous coatings. The work reported here utilises radio frequency magnetron sputtering to deposit both amorphous CaP and Sr-containing CaP coatings and their characterisation using X-Ray Photoelectron Spectroscopy (XPS) and Time-of-Flight Secondary Ion Mass Spectrometry (ToF-SIMS). The CaP coating had a high Ca/P atomic ratio at 1.81 ± 0.02. The amorphous Sr containing CaP coating was shown to contain Sr with a Ca/P and (Ca + Sr)/P atomic ratios of 1.18 ± 0.05 and 1.49 ± 0.05, respectively. Peak-fitting of the overlapping Sr3d and P2p region also showed the presence of previously unreported doublets for each element. The ToF-SIMS results also highlighted that Sr was homogeneously distributed across the surface of the Sr containing coating via detailed chemical mapping experiments. This study has shown that sputtering can be used to deposit Sr-containing CaP coatings and that the use of surface analytical techniqes is important for understanding their uppermost surface properties.