Effects of magnesium doping on the properties of hydroxyapatite/sodium alginate biocomposite

ABSTRACT

A novel hydroxyapatite/sodium alginate biocomposite doped with magnesium was developed to enhance the physical, mechanical and bioactivity properties in bone implant applications. Specifically, magnesium was doped in hydroxyapatite (HA) (Ca₁₀(PO₄)₆(OH)₂/sodium alginate (SA) (NaC₆H₇O) by using precipitation method. This research also explored the effects of magnesium doping on HA/SA samples. The prepared powder was uniaxially pressed and sintered at 1300°C. The characterisation of Mg-doped HA/SA at various concentration ranging from 0.5?wt-% to 1.5?wt-% were performed through Field Emission Scanning Electron Microscopy (FESEM) analysis. The maximum relative density and hardness of Mg-doped HA/SA were fixed at 92% and 4.11?GPa respectively and at 1.0?wt-% for samples of magnesium doping. Based on the microstructure analysis by FESEM it is evident that the elements were distributed evenly in Mg-doped hydroxyapatite/sodium alginate (HA/SA). These results proved that the Mg doping increased the physical, mechanical and bioactivity properties of HA/SA biocomposite.     

In vitro evaluation and mechanical studies of MgO added borophosphate glasses for biomedical applications

The objective of current research is to evaluate the bioactive and tribological properties of the MgO doped borophosphate glass system. The glass system constituted of 40% B₂O₃ - (20-x) % CaO – 25% Li₂O – 15% P₂O₅ – x % MgO (mol%), x = 0, 0.5, 01, 02, 03 and synthesized using the melt quench technique. In-vitro bioactivity was determined using simulated body fluid (SBF) at 37 °C with time intervals of 7, 14 and 21 days. Hydroxyapatite (HA) layer formation was assessed using characterization techniques like XRD, FTIR and FESEM-EDS for structural, functional and morphological analysis respectively. The effect of MgO content on microhardness and tribological properties was studied by making cylindrical shaped glass samples. MTT assay was performed for various doses (62.5–1000 μg/ml) of glass dilutions using MG-63 cell line. In-vitro bioactivity showed higher Ca/P ratio with increase in MgO content after 21 days of immersion. MgO content seemed to promote degradation of glass due to formation of open structure in glass network. Borophosphate glass having 3% MgO exhibited the highest hardness value of 5.79(±0.08) GPa with minimum specific wear rate of 1.86 × 10^?11 and 1.38 × 10^?11 m³/Nm at a load of 15 N and 20 N respectively. MTT assay demonstrated the non-toxic behaviour of glass samples even at a higher dose level of 1000 μg/ml which confirmed its biocompatible behaviour. The study suggests that produced MgO doped borophosphate glass exhibits essential characteristics of bioactive materials and hence could be effective in bone filling and wound healing applications.     

Bioactivity and Antibacterial Behaviors of Nanostructured Lithium-Doped Hydroxyapatite for Bone Scaffold Application

The material for bone scaffold replacement should be biocompatible and antibacterial to prevent scaffold-associated infection. We biofunctionalized the hydroxyapatite (HA) properties by doping it with lithium (Li). The HA and 4 Li-doped HA (0.5, 1.0, 2.0, 4.0 wt.%) samples were investigated to find the most suitable Li content for both aspects. The synthesized nanoparticles, by the mechanical alloying method, were cold-pressed uniaxially and then sintered for 2 h at 1250 °C. Characterization using field-emission scanning electron microscopy (FE-SEM) revealed particle sizes in the range of 60 to 120 nm. The XRD analysis proved the formation of HA and Li-doped HA nanoparticles with crystal sizes ranging from 59 to 89 nm. The bioactivity of samples was investigated in simulated body fluid (SBF), and the growth of apatite formed on surfaces was evaluated using SEM and EDS. Cellular behavior was estimated by MG63 osteoblast-like cells. The results of apatite growth and cell analysis showed that 1.0 wt.% Li doping was optimal to maximize the bioactivity of HA. Antibacterial characteristics against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) were performed by colony-forming unit (CFU) tests. The results showed that Li in the structure of HA increases its antibacterial properties. HA biofunctionalized by Li doping can be considered a suitable option for the fabrication of bone scaffolds due to its antibacterial and unique bioactivity properties.     

In vitro cytotoxicity and ion release of multi-ion doped hydroxyapatite

Multi-ion doped hydroxyapatite (HA) is gaining more attention due to its potential in enhancing multifunctional biological, structural, and mechanical properties for orthopedic and dental applications. In this study, HA doped with multiple cations (Sr⁺², Zn⁺², Ag⁺) and anion (F⁻) was prepared by high-energy ball milling. Sintered HA samples were evaluated for their in vitro cytocompatibility, ion release, and bioactivity. The composition of multi-ion doped HA was optimized using Design of experiments (DOE). Our analysis showed that the contribution of each dopant on cell proliferation changes with culture duration. During first 3 days, F⁻ exhibited strongest influence and during 7-day proliferation Sr⁺² and Ag⁺ had maximum influence. Binary ion doping found to have strong interaction on cell proliferation, while the ternary and quaternary ion doping did not show any interactions. In general, up to twofold increase in the cell viability was achieved with ternary and quaternary ion doping consisting of Sr⁺², Zn⁺², Ag⁺ and F⁻. Although large number of compositions has been identified to exhibit better in vitro cell viability than pure HA, for enhanced long-term cytocompatibility the compositions of multi-ion doped HA would be 2.5Sr-2.5Zn-2.5Ag, 2.5Sr-5Zn-2.5Ag, and 5Sr-2.5Zn-2.5Ag with up to 5 wt% F.     

Mechanical properties,microstructure, and bioactivity of β-Si3N4/HA composite ceramics for bone reconstruction

Pure hydroxyapatite (HA) as bone graft substitute has excellent osteogenic activity, but it has lower fracture toughness and its biological activity is harmed by the addition of toughening phases, which limits its clinical application. To alleviate the contradiction, columnar β-Si₃N₄ as the toughening phase and La³⁺/Y³⁺ sintering aid as active ions are used in this study to prepare β-Si₃N₄/HA composite biomaterials. According to the results, hardness and toughness of 10 wt% β-Si₃N₄/HA composite prepared by cold press sintering at 1300 °C were 6.44 GPa and 1.69 MPa m^1/2, respectively, being 110% and 140% higher than those of pure HA. Moreover, 10 wt% β-Si₃N₄/HA composite exhibited better protein adsorption capacity and obviously stimulated adhesion, proliferation, and osteogenic differentiation of osteoblast. In addition, it was found that sintering aid not only facilitated the improvement of mechanical properties, but also promoted the formation of 100–200 nm nanostripe structure, which was beneficial to cell adhesion. Determination of La³⁺concentration combined with biological experiments also proved that its concentration range from 4×10⁻⁸ M to 6 × 10⁻⁸M was beneficial to cell proliferation and osteogenic differentiation. In summary, β-Si₃N₄ and sintering aids were shown to improve mechanical properties of HA at maintaining the biological activity of the latter.     

Optical,mechanical and fractographic response of transparent alumina ceramics on erbium doping

Alumina ceramics found their utilisation in many applications which can be further extend by attaining functional properties; in our case the transparency obtained through precise processing and photoluminescence due to erbium (Er) doping. In order to examine the optical, mechanical and fractographic response of transparent alumina on Er doping, slip casted samples containing 0–0.15 at.% of erbium nano-oxide were pre-sintered by two-step sintering regime and then hot isostatically pressed. Prepared samples exhibited fully dense submicron microstructure and corresponding high transparency (RIT up to 60%). Positive influence of doping on the Vickers hardness resulted in values up to 27 GPa (at 10 N load). Moreover, the comparison of the Vickers hardness determined at different loadings with literature data showed that the Er doped alumina is one of the hardest material in this category. The samples were characterised also in terms of fracture toughness and fractographic behaviour.     

Inorganic-salt coprecipitation synthesis,fluoride-doping,bioactivity and physiological pH buffering evaluations of bredigite

Bredigite (Ca₇MgSi₄O₁₆), with suitable bioactivity, biodegradation, biocompatibility and mechanical properties, is a promising candidate for the repair and regeneration of damaged bone tissues. In this research, for the first time, bredigite was synthesized by a facile and inexpensive coprecipitation method using inorganic salt precursors, followed by calcination at 1200 °C. Additionally, 0.5 mol% fluoride was successfully doped into the structure without the formation of any second phases. X-ray diffraction and Fourier-transform infrared spectroscopy confirmed the formation of single-phase orthorhombic bredigite in the samples and the incorporation of fluoride in the doped sample, respectively. Both the undoped and doped samples exhibited apatite-formation ability in terms of the precipitation of hydroxycarbonate apatite when exposed to a simulated physiochemical medium, with an increase in this characteristic as a result of fluoride doping. The addition of fluoride also lowered and buffered the pH value of the medium, where the enhancement of this parameter is due to the fast bioresorption of bredigite affecting disadvantageously biocompatibility.     

Mechanically strong and bioactive carbon fiber-SiC nanowire-hydroxyapatite-pyrolytic carbon composites for bone implant application

Carbon fiber-SiC nanowire-hydroxyapatite-pyrolytic carbon composites (CHS) composed of carbon fiber, hydroxyapatite (HA), SiC nanowires (SiCnws) and pyrolytic carbon (PyC) were prepared by sol-gel, heat treating, electrochemical deposition (ECD) and isothermal chemical vapor infiltration (ICVI) for bone implant application. The morphology, microstructure and the composition of CHS were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS) and transmission electron microscopy (TEM). The mechanical properties of CHS were tested and compared with the traditional bone implant materials. The in-vitro bioactivity was evaluated by testing the cell morphology, cell proliferation and cell differentiation. The results show that SiCnws and HA are distributed uniformly inside the CHS. SiCnws are attached on the carbon fibers. The diameter of the SiCnws is around 250 nm and the length is more than 100 μm. HA could grow on the surface of both SiCnws and carbon fibers, forming a brush shape. The flexural strength, shear strength, out-of-plane and in-of-plane compressive strength of CHS are 127 MPa, 90 MPa, 169 MPa and 213 MPa, respectively. The elastic modulus of CHS is 7.2 GPa. The mechanical properties of CHS are similar to those of cortical bone. In-vitro cell test shows that CHS has excellent cell proliferation and cell differentiation. CHS possessing good mechanical and biological performances may have potential to be applied for bone implant materials.     

Effect of A‐ or B‐site doping of perovskite calcium manganite on structure,resistivity, and thermoelectric properties

Bismuth‐, lanthanum‐, and molybdenum‐doped calcium manganite (CaMnO₃, abbreviated Mn113) are synthesized by solid‐state synthesis route from their respective oxide precursors at a same doping level (x=0.05). Depending on the ionic sizes, trivalent dopants (Bi³⁺ and La³⁺) replace Ca²⁺(A site), while penta/hexavalent dopant Mo⁵⁺/Mo⁶⁺ replaces Mn⁴⁺ (B site) in the Mn113 structure. XRD of all three doped samples confirm formation of single phase. In all three samples, doping causes unit cell volume to expand, while volume expansion is maximum for the Mo‐Mn113. The transport behavior of the doped samples follows small polaron hopping mechanism. Resistivity of the doped samples depends not only on the carrier concentration but also on the effective bandwidth determined by the structural distortion introduced by the dopant ions. Bi‐Mn113 has highest resistivity at the both temperature end, while La‐Mn113 has the lowest. Thermopower is determined by the carrier concentration only and does not depend on dopant type, having value ~260 μV/K at 1000 K. At high (>800 K), S reaches a saturation value and becomes independent of T. La‐Mn113 is having highest figure of merit (zT) 0.19 at 1000 K.     

Fabrication of fibrous poly (ɛ-caprolactone) nano-fibers containing cerium doped-bioglasses nanoparticles encapsulated collagen

Novel nanosized designed ceramic powders, cerium (Ce) doped bioglass (BG) with various doped Ce content, were synthesized by sol–gel method in order to be employed in the development of PCL fibrous scaffold for bone tissue engineering applications. Characterization techniques such as X-ray diffraction analysis, transmission electron microscopy, Fourier transform infrared spectroscopy, and energy-dispersive X-ray spectroscopy were employed to evaluate the developed Ce doped BG powders. The results confirmed successful doping of Ce inside BG structure. 0, 1, 3, and 10 wt% Ce doped 58S BG were successfully encapsulated in the collagen microspheres by water-in-oil emulsion method and the average particle size and hydrodynamic diameter of microspheres were determined using scanning electron microscopy and dynamic light scattering analysis, respectively. Next, 0, 1, 3, and 10 wt% Ce doped 58S BG encapsulated collagen microspheres were loaded inside the Poly(ɛ-caprolactone) fibrous scaffold and their in vitro bioactivity and biocompatibility properties were evaluated. The results of soaking samples in the simulated body fluid showed that all Ce doped 58S BG encapsulated collagen microspheres loaded PCL fibrous scaffold have acceptable bioactivity and apatite formation ability over time. The biocompatibility evaluation of developed scaffolds showed high viability and proliferation of MG63 cells cultured on the surface of 3% Ce doped 58S BG encapsulated collagen microsphere loaded in the PCL fibrous scaffold and its high potential ability for bone tissue engineering applications. These results potentially open new aspects for scaffolds aimed at the regeneration of bone defects.     

Adjusting physicochemical and cytological properties of biphasic calcium phosphate by magnesium substitution: An in vitro study

Biphasic calcium phosphate (BCP) is a highly study bone defect repair material with adjustable degradation, perfect osteoconduction and good osteoinduction. As one of the essential trace elements, magnesium (Mg) possesses the abilities of pro-osteogenesis and pro-angiogenesis. Therefore, Mg doping may further expand the application of BCP in bone defect repair, but few studies focus on promoting the osteogenesis and angiogenesis of BCP simultaneously by Mg doping, and the optimal doping amount of Mg remains to be explored. In this study, the physicochemical and biological properties of BCP scaffold affected by Mg doping were systematically study. Results showed that Mg doping enhanced the sintering of BCP scaffold, resulting in the decrease of degradation rate at the initial soaking period. However, the introduction of Mg damaged the lattice stability of BCP, leading to the increase of BCP degradation rate at the later soaking period. BCP scaffolds with Mg doping content ≥3 mol.% could achieve a long-term sustained release of Mg. The ion microenvironment created by Mg-doped scaffolds was simultaneously conducive to the osteogenic differentiation of stem cells and the enhanced angiogenic activity of endothelial cells. The scaffold doped with 5 mol.% of Mg (Mg5–S) showed the highest efficiency in promoting osteogenic differentiation. Mg-doped BCP scaffolds with a doping content ≥3 mol.%, especially Mg5–S, significantly improved the proliferation and angiogenic differentiation of endothelial cells. Based on these, we believe that the optimal doping content of Mg in BCP is 5 mol.%, and Mg5–S has great application potential in bone defect repair.     

Bioactivity enhancement by a ball milling treatment in novel bioactive glass-hydroxyapatite composites produced by spark plasma sintering

Hydroxyapatite (HA) and a lab-made bioactive glass (BGMS10) are combined (50/50 wt%) in this work, where the effect produced by a ball milling (BM) treatment (0–120 min) prior SPS consolidation on the characteristics of the resulting products is investigated. An extraordinary improvement of the apatite-forming ability during in-vitro test on SPS samples (800 °C/70 MPa/2 min) is obtained using the 30 min BMed mixture. Superior Young’s Modulus (122 GPa) and Vickers Hardness (675) were also found compared to unmilled samples (95 GPa and 510, respectively). Microstructural changes induced by BM, with 90 nm HA crystallites size in the bulk composite, and the intimate HA/BGMS10 interfaces established, are the factors mainly responsible for such result. When milling was prolonged to 120 min, samples with relatively lower density, mechanical properties, and in-vitro bioactivity, were produced under the same SPS conditions. The formation of crystalline SiO₂ during SPS might be responsible for such behaviour.     

Mechanical properties of warm sprayed HATi bio-ceramic composite coatings

To explore a new approach for fabricating the load bearing implants with the combination of bioactivity, biocompatibility, and mechanical properties, mechanically mixed hydroxyapatite (HA) and titanium (Ti) powders containing 30, 50, and 70 wt% Ti were sprayed onto a 316L stainless steel substrate using a warm spray (WS) process. The microstructures, phase compositions, chemical structures, and mechanical properties of WS HATi composite coatings were comprehensively investigated and compared to those of WS HA coating. Experimental results indicate that the cross-sectional microstructures of WS HATi composite coatings present typical lamellar structures composed of curved stripes formed by well-deformed and oxidized Ti splats and limited deformed HA splats, and are significantly influenced by the Ti content in the original powders. Phase constitutions of the composite coatings mainly consist of HA, Ti, TiO_2, and TiO. Chemical structures of HA in the composite coatings deposited using powders with Ti content less than 30% are similar to the structures in the original powder. The microhardness, elastic modulus, and bond strength of the coatings increased from 0.32 ± 0.15 GPa to 1.41 ± 0.31 GPa, from 1.37 ± 0.28 GPa to 23.28 ± 3.45 GPa, and from 17.3 ± 2.2 MPa to 34.8 ± 3.2 MPa, respectively. The abrasive wear weight loss of the coatings on Al₂O₃ abrasive paper decreased from 2.9 mg to 1 mg, as the addition of Ti particles in original powders increased from 0 to 70%.     

Biomimetic Mg- and Mg,CO3-substituted hydroxyapatites: synthesis characterization and in vitro behaviour

The doping of the apatite with carbonate or/and Mg ions in biologically-like amounts (6 and 1 wt.%, respectively) was performed. Chemico-physical characterizations and cell culture tests were carried out onto the synthetic Mg- and Mg,CO₃-substituted (∼30–40 nm particle size) powders in comparison with stoichiometric HA (∼160 nm particle size) to determine as mesenchymal stem cells (MSCs) can directly use the mineral microenvironment to stimulate their own proliferation and differentiation activities. At the same time the growth of human osteoblast like cells (MG-63) was evaluated to determine the compatibility of the synthetic doped apatites for bone substitution. Cell morphology analysis by SEM as well as MTT and ALP tests were performed.The peculiar chemico-physical properties of the doped (Mg- and Mg,CO₃-substituted) materials improved the behaviours of MSC and MG-63 cells in term of adhesion, proliferation and metabolic activation compared to stoichiometric HA.     

Structural,optical, morphological properties of silver doped cobalt oxide nanoparticles by microwave irradiation method

The synthesis of silver doped cobalt oxide nanoparticles by microwave-assisted method and their structural, optical, antibacterial activities are presented in this study. The doping concentrations were chosen as 5, 10, 15, and 20 wt percentages. The sample was undergone powder X-ray diffraction studies and the result shows the good crystalline nature of the sample. Also, the average crystallite size increases from 13.95 nm, 21.26 nm, 26.13 nm, and 28.35 nm with different doping concentrations. The transmission electron microscopy image shows cubic and spherical morphology. The optical properties were tested by UV–vis–NIR absorption spectrum. It indicates the decrease of band gap value. From the antibacterial activity studies, the 20 wt % Ag doped nanoparticles exhibit better activity.     

Synthesis,characterization, and visible-light photocatalytic activity of transition metals doped ZTO nanoparticles

Transition metals doping has been proved to be a feasible way for tuning the physical properties on the surface and bulk of nanomaterials and also for the good performance in decontamination of emerging pollutants. In this context, doped samples of zinc tin oxide or zinc stannate nanoparticles (ZTO NPs) by several transition metals were synthesized in order to enhance the optical absorbance with the aims of reducing the band gap and therefore ameliorated their photocatalytic activity. They were characterized by the X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), diffuse reflectance spectroscopy, Raman spectroscopy and photoluminescence. The XRD patterns and the microscopic observations showed the formation of spherical nanoparticles with an average size of about 30 nm and highly pure ZTO phase with an inverse spinel structure. The Raman spectra were dominated by bands relatives to the F2g (2) and A1g symmetries modes of inverse spinel structure. The band gap Eg is estimated to be 3.75 eV for the undoped sample, and 3.67, 3.64, 3.78 and 3.21 eV, for 2% Fe, 2% Mg, 2% Gd, and 2% Mn doped ZTO samples, respectively.Furthermore, the undoped ZTO NPs have the intrinsic problem of recombination of photogenerated charge carriers. We have shown that the reduction of the band gap and oxygen vacancies resulting from the doping effect could be a useful tool for trapping and avoid the recombination of electrons coming from photosensitized rhodamine B (RhB) under visible light irradiation. Owing to the structural advantages and low band gap, 2% Mn doped ZTO NPs, with the kinetic rate constants k of 0.024 min⁻¹, show enhanced performance for the elimination of RhB in aqueous solution compared to undoped and other doped ZTO NPs.     

The Effect of Grain Size on the Mechanical and Optical Properties of Spark Plasma Sintering‐Processed Magnesium Aluminate Spinel MgAl2O4

The study deals with the effect of the SPS parameters and LiF doping on the mechanical and optical properties polycrystalline magnesium aluminate spinel (PMAS) with emphasis on the grain size of the final product. Sintering at 1300°C of undoped powder yielded fully dense submicrometer (0.4–0.6 μm) samples with elevated mechanical properties (1600HV and 300MPa bending strength). Doped samples had a larger, 40 μm grain size, lower, 1450HV, hardness and 150MPa bending strength. The transmittance of the doped samples (80% at 500 nm wavelength) was higher than that of the undoped ones. Thus, the required functionality of the ceramic dictates the choice of parameters for the fabrication of dense transparent PMAS.     

Influence of low concentration Sm doping on optical and catalytic performance of titania

The work focuses on exploring the effect of the concentration of Sm dopant (0.2–0.6 at.%) on structural, optical and photocatalytic properties of the spin coated titania based thin films annealed at different temperatures. The optical interpretation involves the influence of Sm doping on optical constants and luminescence behaviour of the samples. The comprehensive work on optical bandgap, Urbach energy and electron-phonon interaction strength was conducted for Sm doped samples. The optical band gap was found to increase with the increasing concentration of Sm, but decreased with high temperature annealing. Using ellipsometry measurement, refractive index of the samples was obtained. The orbital level information was gathered using X-Ray Photoelectron Spectroscopy (XPS) study with a special emphasis on the evolution of physico-chemical properties as function of Sm doping. The XPS study confirms the presence of Sm in the titania host material and it helped in estimating defects induced by Sm doping. The photocatalytic study of Sm doped titania thin films was carried out by using methylene blue (MB) and Rhodamine B (RhB) dye and we have found an enhanced photocatalytic activity for the 0.4 at.% Sm doped samples.     

Morphological,mechanical, and biological evolution of pure hydroxyapatite and its composites with titanium carbide for biomedical applications

Pure hydroxyapatite (HAp) was synthesized successfully via a wet chemical precipitation method. To study the influence of TiC (weight % of 5, 10, 15) substitution on the mechanical behavior of pure HAp, its composites with TiC were synthesized using a solid-state reaction method. Herein, detailed investigations of pure HAp and its composites using X-ray powder diffraction (XRD), FTIR spectroscopy, Raman spectroscopy, UV-VIS spectroscopy, SEM followed by EDAX and particle size analysis were carried out. XRD study reveals the phase stability of the prepared HAp and composite samples. However, FTIR and Raman spectroscopic studies revealed the bond formation among the various constituents. Mechanical behavior of HAp, and its composites with TiC were studied using numerous parameters like density, Young's modulus, fracture toughness, and load absorption capability. Based on these studies, it was revealed that the addition of 5 wt % substitution of TiC sintered at 1200 °C significantly enhanced the mechanical properties of pure HAp. Hence, 5 wt % of TiC composite 95HAp-5TiC showed the best mechanical characteristics such as density (2.3060 g/cm³), Young's modulus (14.53 MPa), fracture toughness (19.82 MPa m^1/2), maximum compressive strength (186 MPa) respectively. Cytotoxicity and osteogenic activities of the synthesized pure HAp and its composite, 95HAp-5TiC were performed using osteoblast cells (mouse calvarial) at different concentrations of the samples (0.01 μg, - 100 μg). From the above studies, the cell viability and ALP activities of the composite, 95HAp-5TiC found to be excellent than that of pure HAp. Hence, this composite sample may be utilized for bone implant applications.     

Antibacterial and magnetic response of site-specific cobalt incorporated hydroxyapatite

Hydroxyapatite [HA, Ca₁₀(PO₄)₆(OH)₂] based ceramics are a potential candidate for orthopedic implants, bone cements, and bioactive coating over metallic implants due to their compositional similarities [Ca/P = 1.67] with human bone. Cobalt doping in HA can greatly enhance angiogenesis and vascularization along with incorporating antimicrobial properties to HA. For the first time, this work reports the importance of Co doping sites on biological and magnetic properties of HA. In the current work, Co doing in HA has been carried out according to the chemical formula Ca₁₀(PO₄)₆Co_x(OH)_2-α and Ca_10-x Co_x(PO₄)₆(OH)₂, (x = 0, 0.2 and 0.3) to assess the correlation of individual Co incorporation sites on crystal chemistry, cytotoxicity, magnetic properties, ion leaching and antibacterial efficacy. Dependence of antibacterial efficacy on different doping sites revealed that cytocompatible Co doped HA is antibacterial against E. coli, and S. aureus mainly after substitution of Co in Ca site. Additionally, a minor antibacterial effect has been noticed after Co doping in OH channels. Interestingly, the Ca substituted Co doped HA shows Co leaching up to ∼758 ppb (obtained from inductively coupled plasma-mass spectrometry), which comes to only ∼27 ppb after incorporating Co in OH channel. This higher Co leaching (when doped at Ca site in comparison to that at OH channels) is the major cause of better antibacterial efficacy. Vibrating sample magnetometer measurements showed that the order of m_r and m_s values significantly changes after altering the doping sites, due to change in local Co environment. Thus, this work proves that different doping sites of Co doped HA can greatly enhance its antibacterial properties with significant changes in crystallographic and magnetic properties, which make Co doped HA an ideal choice as a bone replacement material or drug delivery agent with tailored properties depending on the doping sites.