Search Results (29)

This research investigated the feasibility of producing strontium-doped nanocrystalline hydroxyapatite (SrHAp) through an environmentally benign synthesis approach and evaluated the antimicrobial activity of the resulting material. The synthesized nanomaterial was subjected to comprehensive characterization. The antimicrobial efficacy of SrHAp was tested against Gram-positive and Gram-negative bacterial strains. X-ray diffraction (XRD) analysis in combination with Fourier-transform infrared (FT-IR) spectroscopy confirmed the successful formation of pure monocrystalline SrHAp. The scanning electron microscopy (SEM) examination revealed two predominant morphological structures: nanorods and prismatic configurations of the SrHAp. Transmission electron microscopy (TEM) demonstrated that the rod-like SrHAp nanocrystals aggregate into elongated grain structures with a size of about 25 nm × 10 nm. Inductively coupled plasma-optical emission spectroscopy (ICP-OES) analysis confirmed the presence and quantification of the concentrations of calcium, strontium, and phosphorus, while confirming the expected calcium–phosphorus ratio characteristic of hydroxyapatite. The study established that the positive surface charge of the material, with a point of zero charge near pH 10, is essential for its antimicrobial efficiency. These results suggest that SrHAp nanomaterials hold promise for biomedical applications, particularly as antimicrobial coatings for implants and scaffolds for bone tissue, where the prevention of infection is critical. Overall, despite its selective and material quantity-dependent antimicrobial efficacy, environmentally friendly synthesized SrHAp can be successfully applied as an effective controller of targeted microbial contamination, especially of Gram-positive bacterial species S. aureus, L. monocytogenes, S. Enteritidis, and A. baumanii. Full article

Background/Objectives: Recent advancements in biomaterials aimed at closely mimicking natural biological tissues hold great promise for hard tissue regeneration and controlled drug release due to their superior physical, chemical, and biological properties. This study aimed to develop multi-ion doped calcium hydroxyapatite (HAp) scaffolds with chitosan-based coatings for localized drug delivery, incorporating a novel hydrazone compound with potential anticancer activity. Methods: HAp powders doped with magnesium (Mg²⁺), strontium (Sr²⁺), and varying fluoride (F⁻) contents (0–2 mol.%) were synthesized via a hydrothermal method. Scaffolds were fabricated using the sponge replica technique and subsequently coated with chitosan or a chitosan–hydrazone blend. Dopant incorporation was confirmed by electron dispersive X-ray spectroscopy (EDS). Phase composition and morphology were analyzed via X-ray diffraction (XRD) and scanning electron microscopy (SEM). Mechanical properties, bioactivity, cytotoxicity, and hydrazone release profiles were systematically evaluated. Results: EDS confirmed successful incorporation of Mg²⁺ and Sr²⁺ in all powders, while F⁻ was detected only in powders with 1 and 2 mol.% fluoride. XRD and SEM revealed the phase composition and scaffold microstructure. Chitosan coatings significantly improved scaffold compressive strength and reduced degradation rate, indicating enhanced stability in biological environments. The coated scaffolds supported MRC-5 fibroblast viability. The hydrazone compound exhibited dose-dependent antitumor cytotoxicity comparable to cisplatin and showed sustained release from scaffolds for up to 15 days. Conclusions: The combination of multi-ion doped HAp scaffolds and chitosan–hydrazone coatings provides a promising platform for bone tissue engineering and localized cancer therapy, demonstrating both mechanical stability and controlled, sustained drug release. Full article

The ion doping of hydroxyapatite (HA) has gained appeal as a chemical method of improving and adding new characteristics to materials used in biomedical engineering. Dimension, morphology, porosity, surface charge, topology, composition, and other material characteristics make doped HA more suitable for specific biomedical applications. The main aim of this review study was to highlight the role of iHA (iHA) in developing drug delivery systems, tissue engineering, implant coating, wound healing, and multimodal imaging. To the best of our knowledge, depending on the dopant, iHA can have inherent distinct mechanical, physicochemical, and biological properties that make it eligible for biomedical application. More importantly, some ions make iHA a potent antibacterial agent and drug carrier for wound healing (e.g., silver, copper, zinc), have tissue engineering capabilities, improved proangiogenic and osteoconductive properties (e.g., strontium, cobalt, nickel), drug loading capacity (e.g., magnesium, ferric, strontium), metallic implant coating properties (e.g., manganese, silver, copper), and multimodal imaging potential (e.g., terbium, ytterbium, cerium). The concentration of ions and the number of dopants played a vital role in developing new approaches based on iHA. In conclusion, iHA, compared to HA, could show better improvements in biomedical applications. Full article

One of the main challenges in hydroxyapatite research is to develop cost-effective synthesis methods that consistently produce materials closely resembling natural bone, while maintaining high biocompatibility, phase purity, and mechanical stability for biomedical applications. Traditional synthetic techniques frequently fail to provide desirable mechanical characteristics and antibacterial activity, necessitating the development of novel strategies based on natural precursors and selective ion doping. The present study aims to explore the possibility of synthesizing hydroxyapatite through the co-precipitation method, followed by a microwave-assisted hydrothermal maturation process. The main CaO sources selected for this study are eggshells and mussel shells. Cu²⁺ and Sr²⁺ ions were added into the hydroxyapatite structure at concentrations of 1% and 5% to investigate their potential for biomedical applications. Furthermore, the morpho-structural and biological properties have been investigated. Results demonstrated the success of hydroxyapatite synthesis and ion incorporation into its chemical structure. Moreover, HAp samples exhibited significant antimicrobial properties, especially the samples doped with 5% Cu and Sr. Additionally, all samples presented good biological activity on MC3T3-E1 osteoblast cells, demonstrating good cellular viability of all samples. Therefore, by correlating the results, it could be concluded that the undoped and doped hydroxyapatite samples are suitable biomaterials to be further applied in orthopedic applications. Full article

To address the biological inertness of pure titanium implants, a composite coating with a strontium-doped hydroxyapatite (Sr-HA) phase and H₂Ti₅O₁₁·H₂O nanorods was engineered via ultrasonic-assisted micro-arc oxidation (UMAO) with hydrothermal treatment (HT). The ultrasonic field was applied to modulate the MAO discharge behavior, enhancing ion transport and coating formation. Structural characterization revealed that UMAO-HT coatings exhibited a lower anatase/rutile ratio and higher Sr-HA crystallinity, as compared to MAO-HT. In vitro simulated body immersion studies showed that UMAO-HT induced rapid apatite formation within 24 h, with a better apatite-inducing ability than the conventional MAO-HT. Density functional theory (DFT) simulations demonstrated that Sr substitution in HA lowered the (001) surface work function, enhancing Ca²⁺ adsorption energy and promoting apatite phase nucleation. This work reported the synergistic effects of ultrasonic-induced microstructure optimization and Sr-HA higher bioactivity, providing a mechanistic framework for designing next-generation bioactive coatings with enhanced osseointegration potential. Full article

Hydroxyapatite nanowires (HAW) can effectively improve the bone repair ability in bone engineered tissue. However, due to their single function, the application of HAWs in biological tissue engineering materials is limited. In this study, strontium-doped hydroxyapatite nanowires (SrHAW) were synthesized by a hydrothermal method and coated with polydopamine (PDA) to improve the function of HAWs. The material structure, biocompatibility evaluation, and differentiation capability testing of PDA-coated strontium-doped hydroxyapatite (SrHAW@PDA) nanowires were conducted. Then, the nanowires were co-cultured with rat bone marrow mesenchymal stem cells (BMSCs) and rat umbilical vein endothelial cells (UVECs) to prepare cell spheroids. Compared with the undoped and uncoated HAW, the SrHAW@PDA nanowires enhanced the cell activity and their angiogenesis and osteogenesis abilities. In addition, their performance in the three-dimensional spheroid also played a positive role in the cells in the spheroid. Due to the presence of PDA, the adhesion between the cells in the three-dimensional spheroid and the nanowires were enhanced. In summary, these results show that SrHAW@PDA has the potential to be used as an alternative material to regulate cell biological activity in three-dimensional cell spheroids. Full article

The present work investigates the rheological behavior of ceramic slurries made of hydroxyapatite powders doped with magnesium and strontium ions and selected as particularly relevant for biomedical applications. The incorporation of doping ions into the apatite crystal structure is a well-known way to enhance the bioactivity of hydroxyapatite through compositional and structural changes, however, this also affects the rheological properties relevant to the fabrication of ceramic devices by forming techniques based on the manipulation of aqueous slurries. We analyzed the effect of different apatitic chemical compositions, powder content, and dispersant amount on the shear behavior and flowability of slurries, thus finding that the structural changes in hydroxyapatite induced by ion doping significantly affected the colloidal stability of the apatite powders and the viscoelasticity of the slurries. This leads to improved rheological behavior in the hydroxyapatite suspensions, which is suitable for the future development of ceramic slurries, particularly for achieving novel ceramic devices by extrusion-based techniques. Full article

Autogenous grafts remain the “gold standard” in bone tissue grafting procedures; however, limitations such as donor site morbidity, invasiveness, and limited availability have spurred research into alternative materials. Hydroxyapatite (HA), a widely used bioceramic, is known for its bioactivity and biocompatibility. Nonetheless, its inherent brittleness and porosity necessitate modifications to enhance its mechanical and functional properties. Ionic doping has emerged as a transformative strategy to improve the properties of HA by integrating ions such as strontium (Sr²⁺), magnesium (Mg²⁺), and zinc (Zn²⁺). These dopants influence HA’s crystal structure, morphology, and solubility, resulting in enhanced bioactivity, accelerated bone mineralization, and improved mechanical properties, such as increased fracture resistance and wear durability. Additionally, antimicrobial properties can be achieved through the inclusion of silver ions (Ag⁺), reducing the risk of peri-implant infections. This review focuses on the effects of ionic doping on the structure and functionality of hydroxyapatite, emphasizing advancements in tailoring its properties to clinical needs. By consolidating two decades of research, this study highlights how ionic doping bridges the gap between synthetic biomaterials and native bone, unlocking new potential in regenerative medicine and orthopedic applications. Full article

This study aimed to compare the biological properties of newly synthesized cements based on calcium phosphate with a commercially used cement, mineral trioxide aggregate (MTA). Strontium (Sr)-, Copper (Cu)-, and Zinc (Zn)-doped hydroxyapatite (miHAp) powder was obtained through hydrothermal synthesis and characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), and energy dispersive X-ray spectrometry (EDX). Calcium phosphate cement (CPC) was produced by mixing miHAp powder with a 20 wt.% citric acid solution, followed by the assessment of its compressive strength, setting time, and in vitro bioactivity. Acetylsalicylic acid (ASA) was added to the CPC, resulting in CPCA. Biological tests were conducted on CPC, CPCA, and MTA. The biocompatibility of the cement extracts was evaluated in vitro using human dental pulp stem cells (hDPSCs) and in vivo using a zebrafish model. Antibiofilm and antimicrobial effect (quantified by CFUs/mL) were assessed against Streptococcus mutans and Lactobacillus rhamnosus. None of the tested materials showed toxicity, while CPCA even increased hDPSCs proliferation. CPCA showed a better safety profile than MTA and CPC, and no toxic or immunomodulatory effects on the zebrafish model. CPCA exhibited similar antibiofilm effects against S. mutans and L. rhamnosus to MTA. Full article

New gelatin methacryloyl (GelMA)—strontium-doped nanosize hydroxyapatite (SrHA) composite hydrogel scaffolds were developed using UV photo-crosslinking and 3D printing for bone tissue regeneration, with the controlled delivery capacity of strontium (Sr). While Sr is an effective anti-osteoporotic agent with both anti-resorptive and anabolic properties, it has several important side effects when systemic administration is applied. Multi-layer composite scaffolds for bone tissue regeneration were developed based on the digital light processing (DLP) 3D printing technique through the photopolymerization of GelMA. The chemical, morphological, and biocompatibility properties of these scaffolds were investigated. The composite gels were shown to be suitable for 3D printing. In vitro cell culture showed that osteoblasts can adhere and proliferate on the surface of the hydrogel, indicating that the GelMA-SrHA hydrogel has good cell viability and biocompatibility. The GelMA-SrHA composites are promising 3D-printed scaffolds for bone repair. Full article

In this work results are presented on the evaluation of HAp, HApSr, HAp_CS, and HApSr_CS layers deposited on Ti substrates regarding L929 cell viability and cytotoxicity as well as antimicrobial activity against Staphylococcus aureus, in connection with their physicochemical properties. The HAp and HApSr layers generated by radio-frequency magnetron sputtering technique were further covered with chitosan by a matrix-assisted pulsed laser evaporation technique. During the plasma depositions, the Ti substrates were heated externally by a home-made oven above 100 °C. The HApSr_CS layers generated on the unpolished Ti substrates at 100 °C and 400 °C showed the highest biocompatibility properties and antimicrobial activity against Staphylococcus aureus. The morphology of the layer surfaces, revealed by scanning electron microscopy, is dependent on substrate temperature and substrate surface roughness. The optically polished surfaces of Ti substrates revealed grain-like and microchannel structure morphologies of the layers deposited at 25 °C substrate temperature and 400 °C, respectively. Chitosan has no major influence on HAp and HApSr layer surface morphologies. X-ray photoelectron spectroscopy indicated the presence of Ca 2p_3/2 peak characteristic of the HAp structure even in the case of the HApSr_CS samples generated at a 400 °C substrate temperature. Fourier transform infrared spectroscopy investigations showed shifts in the wavenumber positions of the P-O absorption bands as a function of Sr or chitosan presence in the HAp layers generated at 25, 100, and 400 °C substrate temperatures. Full article

A challenge in tissue engineering and the pharmaceutical sector is the development of controlled local release of drugs that raise issues when systemic administration is applied. Strontium is an example of an effective anti-osteoporotic agent, used in treating osteoporosis due to both anti-resorptive and anabolic mechanisms of action. Designing bone scaffolds with a higher capability of promoting bone regeneration is a topical research subject. In this study, we developed composite multi-layer three-dimensional (3D) scaffolds for bone tissue engineering based on nano-hydroxyapatite (HA), Sr-containing nano-hydroxyapatite (SrHA), and poly-ε-caprolactone (PCL) through the material extrusion fabrication technique. Previously obtained HA and SrHA with various Sr content were used for the composite material. The chemical, morphological, and biocompatibility properties of the 3D-printed scaffolds obtained using HA/SrHA and PCL were investigated. The 3D composite scaffolds showed good cytocompatibility and osteogenic potential, which is specifically recommended in applications when faster mineralization is needed, such as osteoporosis treatment. Full article

Development of efficient controlled local release of drugs that prevent systemic side effects is a challenge for anti-osteoporotic treatments. Research for new bone-regeneration materials is of high importance. Strontium (Sr) is known as an anti-resorptive and anabolic agent useful in treating osteoporosis. In this study, we compared two different types of synthesis used for obtaining nano hydroxyapatite (HA) and Sr-containing nano hydroxyapatite (SrHA) for bone tissue engineering. Synthesis of HA and SrHA was performed using co-precipitation and hydrothermal methods. Regardless of the synthesis route for the SrHA, the intended content of Sr was 1, 5, 10, 20, and 30 molar %. The chemical, morphological, and biocompatibility properties of HA and SrHA were investigated. Based on our results, it was shown that HA and SrHA exhibited low cytotoxicity and demonstrated toxic behavior only at higher Sr concentrations. Full article

It is a great challenge to obtain an ideal guided bone regeneration (GBR) membrane. In this study, tragacanth gum (GT) was introduced into a chitosan/nano-hydroxyapatite (CS/n-HA) system. The effects of different component ratios and strontium-doped nano-hydroxyapatite (Sr-HA) on the physical-chemical properties and degradation behavior of the CS/Sr-n-HA/GT ternary composite membrane were investigated using Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), scanning electron microscopy (SEM), contact angle, electromechanical universal tester and in vitro soaking in simulated body fluid (SBF). The results showed that CS could be ionically crosslinked with GT through electrostatic interaction, and Sr-n-HA was loaded via hydrogen bond, which endowed the GT/CS/n-HA composite membrane with good tensile strength and hydrophilicity. In addition, the results of immersion in SBF in vitro showed that CS/n-HA/GT composite membranes had different degradation rates and good apatite deposition by investigating the changes in pH value, weight loss, water absorption ratio, SEM morphology observation and tensile strength reduction. All results revealed that the CS/Sr-n-HA/GT (6:2:2) ternary composite membrane possessed the strongest ionic crosslinking of GT and CS, which was expected to obtain more satisfactory GBR membranes, and this study will provide new applications of GT in the field of biomedical membranes. Full article

The reconstruction of bones following tumor excision and radiotherapy remains a challenge. Our previous study, performed using polysaccharide-based microbeads that contain hydroxyapatite, found that these have osteoconductivity and osteoinductive properties. New formulations of composite microbeads containing HA particles doped with strontium (Sr) at 8 or 50% were developed to improve their biological performance and were evaluated in ectopic sites. In the current research, we characterized the materials by phase-contrast microscopy, laser dynamic scattering particle size-measurements and phosphorus content, before their implantation into two different preclinical bone defect models in rats: the femoral condyle and the segmental bone. Eight weeks after the implantation in the femoral condyle, the histology and immunohistochemistry analyses showed that Sr-doped matrices at both 8% and 50% stimulate bone formation and vascularization. A more complex preclinical model of the irradiation procedure was then developed in rats within a critical-size bone segmental defect. In the non-irradiated sites, no significant differences between the non-doped and Sr-doped microbeads were observed in the bone regeneration. Interestingly, the Sr-doped microbeads at the 8% level of substitution outperformed the vascularization process by increasing new vessel formation in the irradiated sites. These results showed that the inclusion of strontium in the matrix-stimulated vascularization in a critical-size model of bone tissue regeneration after irradiation. Full article