Propelling Multi-Modal Therapeutics of PEEK Implants through the Power of NO evolving Covalent Organic Frameworks (COFs)

The design and fabrication of NO-evolving core-shell nanoparticles (denoted as NC@Fe), comprised of BNN6-laden COF@Fe3 O4 nanoparticles, are reported. This innovation extends to the modification of 3D printed polyetheretherketone scaffolds with NC@Fe, establishing a pioneering approach to multi-modal bone therapy tailored to address complications such as device-associated infections and osteomyelitis. This work stands out prominently from previous research, particularly those relying on the use of antibiotics, by introducing a bone implant capable of simultaneous NO gas therapy and photothermal therapy (PPT). Under NIR laser irradiation, the Fe3 O4 NP core (photothermal conversion agent) within NC@Fe absorbs photoenergy and initiates electron transfer to the loaded NO donor (BNN6), resulting in controlled NO release. The additional heat generated through photothermal conversion further propels the NC@Fe nanoparticles, amplifying the therapeutic reach. The combined effect of NO release and PPT enhances the efficacy in eradicating bacteria over a more extensive area around the implant, presenting a distinctive solution to conventional challenges. Thorough in vitro and in vivo investigations validate the robust potential of the scaffold in infection control, osteogenesis, and angiogenesis, emphasizing the timeliness of this unique solution in managing complicated bone related infectious diseases.

Porous Titanium Scaffolds with Mechanoelectrical Conversion and Photothermal Function: A Win-Win Strategy for Bone Reconstruction of Tumor-Resected Defects

Bone metastases severely threaten the lives of patients. Although surgical treatment combined with adjuvant chemotherapy significantly improves the survival rate of patients, tumor recurrence, or metastasis after surgical resection and bone defects caused by surgical treatment remain major challenges for clinicians. Given the abovementioned clinical requirements, barium titanate-containing iron-coated porous titanium alloy scaffolds have been proposed to promote bone defect repair and inhibit tumor recurrence. Fortunately, in vitro and in vivo experimental research confirms that barium titanate containing iron-coated porous titanium alloy scaffolds promote osteogenesis and bone reconstruction in defect repair via mechanoelectric conversion and inhibit tumor recurrence via photothermal effects. Furthermore, the underlying and intricate mechanisms of bone defect repair and tumor recurrence prevention of barium titanate-containing iron-coated porous titanium alloy scaffolds are explored. A win-win strategy for mechanoelectrical conversion and photothermal functionalization provides promising insights into bone reconstruction of tumor-resected defects.

Magnetic Hydroxyapatite Nanoparticles in Regenerative Medicine and Nanomedicine

This review focuses on the latest advancements in magnetic hydroxyapatite (mHA) nanoparticles and their potential applications in nanomedicine and regenerative medicine. mHA nanoparticles have gained significant interest over the last few years for their great potential, offering advanced multi-therapeutic strategies because of their biocompatibility, bioactivity, and unique physicochemical features, enabling on-demand activation and control. The most relevant synthetic methods to obtain magnetic apatite-based materials, either in the form of iron-doped HA nanoparticles showing intrinsic magnetic properties or composite/hybrid compounds between HA and superparamagnetic metal oxide nanoparticles, are described as highlighting structure-property correlations. Following this, this review discusses the application of various magnetic hydroxyapatite nanomaterials in bone regeneration and nanomedicine. Finally, novel perspectives are investigated with respect to the ability of mHA nanoparticles to improve nanocarriers with homogeneous structures to promote multifunctional biological applications, such as cell stimulation and instruction, antimicrobial activity, and drug release with on-demand triggering.

An injectable carboxymethyl chitosan hydrogel scaffold formed via coordination bond for antibacterial and osteogenesis in osteomyelitis

The intricate, hostile, and diverse nature of osteomyelitis (OM) poses a challenge for complete bacterial eradication and osteogenesis promotion via conventional treatment. Recently, functional hydrogels exhibiting antibacterial and osteogenic properties emerge as a promising avenue for OM wound healing in clinical practice. However, the preparation procedures and associated costs on cytokine and cell therapies for certain functional hydrogels can be complex and prohibitively expensive. In our research, a hybrid hydrogel dressing has been formulated utilizing carboxymethyl chitosan (CMCS) as the base material, and designed with inherent antibacterial, adhesion, proliferation, and differentiation characteristics, showing promise as a candidate for eradicating infection and promoting bone regeneration. The hybrid hydrogel is composed of interconnected networks of Fe3+-induced self-assembled CMCS and the antibacterial drug ciprofloxacin (CIP), resulting in excellent injectability and moldability. Notably, the CMCS/Fe3+/CIP hybrid hydrogel is capable of regulating antibacterial responses and stimulating osteogenesis in infected microenvironments without additional additives. This injectable antibacterial and osteogenic-promoting hydrogel establish a high-potential platform for low-cost, safe and effective treatment of OM by expediting the initial stages of infected bone wound repair.

Preparation of lithium-containing magnesium phosphate-based composite ceramics having high compressive strength, osteostimulation and proangiogenic effects

Fairly high concentrations of magnesium and lithium are conducive to improving the osteogenic and angiogenic capacities. In the current study, lithium-containing magnesium phosphate-based ceramics (AMP/LMPGs) were prepared from amorphous magnesium phosphate (AMP) at a low sintering temperature (650 °C), and the lithium/magnesium-containing phosphate glasses (LMPGs) were utilized as sintering additives. During the sintering procedure of AMP/LMPGs, the AMP reacted with LMPGs, producing new compounds. The AMP/LMPGs displayed nano-size grains and plentiful micropores. The addition of LMPGs noticeably increased the porosity as well as compressive strength of the AMP/LMPGs ceramics. The AMP/LMPGs sustainedly released Mg, P and Li ions, forming Mg-rich ionic microenvironment, which ameliorated cellular proliferation, osteogenic differentiation and proangiogenic capacities. The AMP/LMPGs ceramics with considerably high compressive strength, osteostimulation and proangiogenic effects were expected to efficiently regenerate the bone defects.

A Gelatin-Based Composite Hydrogel with a "One Stone, Two Birds" Strategy for Photothermal Antibacterial and Vascularization of Infected Wounds

Bacterial infection, prolonged inflammation, and insufficient angiogenesis are the main challenges for effective wound repair. In this work, we developed a stretchable, remodeling, self-healing, and antibacterial multifunctional composite hydrogel for infected wound healing. The hydrogel was prepared using tannic acid (TA) and phenylboronic acid-modified gelatin (Gel-BA) through hydrogen bonding and borate ester bonds and incorporated iron-containing bioactive glasses (Fe-BGs) with uniform spherical morphologies and amorphous structures to achieve GTB composite hydrogels. On one hand, the chelation of Fe³⁺ in Fe-BGs with TA endowed the hydrogel with good photothermal synergistic antibacterial ability; on the other hand, the bioactive Fe³⁺ and Si ions contained in Fe-BGs can recruit cells and synergistically promote blood vessel formation. In vivo animal experiments showed that the GTB hydrogels remarkably accelerated infected full-thickness skin wound healing by improving granulation tissue formation, collagen deposition, and the formation of nerves and blood vessels while decreasing inflammation. This hydrogel with a dual synergistic effect and ″one stone, two birds″ strategy holds immense potential for wound dressing applications.

Magnesium (Mg2 +), Strontium (Sr2 +), and Zinc (Zn2 +) Co-substituted Bone Cements Based on Nano-hydroxyapatite/Monetite for Bone Regeneration

New bone cement type that combines Sr2 + /Mg2 + or Sr2 + /Zn2 + co-substituted nano-hydroxyapatite (n-HAs) with calcium phosphate dibasic and chitosan/gelatin polymers was developed to increase adhesion and cellular response. The cements were physicochemically described and tested in vitro using cell cultures. All cements exhibited quite hydrophilic and had high washout resistance. Cement releases Ca2 + , Mg2 + , Sr2 + , and Zn2 + in concentrations that are suitable for osteoblast proliferation and development. All of the cements stimulated cell proliferation in fibroblasts, endothelial cells, and osteoblasts, were non-cytotoxic, and produced apatite. Cements containing co-substituted n-HAs had excellent cytocompatibility, which improved osteoblast adhesion and cell proliferation. These cements had osteoinductive potential, stimulating extracellular matrix (ECM) mineralization and differentiation of MC3T3-E1 cells by increasing ALP and NO production. The ions Ca2 + , Mg2 + , Zn2 + , and Sr2 + appear to cooperate in promoting osteoblast function. The C3 cement (HA-SrMg5%), which was made up of n-HA co-substituted with 5 mol% Sr and 5 mol% Mg, showed exceptional osteoinductive capacity in terms of bone regeneration, indicating that this new bone cement could be a promising material for bone replacement.

The Osteogenic Properties of Calcium Phosphate Cement Doped with Synthetic Materials: A Structured Narrative Review of Preclinical Evidence

Bone grafting is commonly used as a treatment to repair bone defects. However, its use is challenged by the presence of medical conditions that weaken the bone, like osteoporosis. Calcium phosphate cement (CPC) is used to restore bone defects, and it is commonly available as a bioabsorbable cement paste. However, its use in clinical settings is limited by inadequate mechanical strength, inferior anti-washout characteristics, and poor osteogenic activity. There have been attempts to overcome these shortcomings by adding various natural or synthetic materials as enhancers to CPC. This review summarises the current evidence on the physical, mechanical, and biological properties of CPC after doping with synthetic materials. The incorporation of CPC with polymers, biomimetic materials, chemical elements/compounds, and combination with two or more synthetic materials showed improvement in biocompatibility, bioactivity, anti-washout properties, and mechanical strength. However, the mechanical property of CPC doped with trimethyl chitosan or strontium was decreased. In conclusion, doping of synthetic materials enhances the osteogenic features of pure CPC. The positive findings from in vitro and in vivo studies await further validation on the efficacy of these reinforced CPC composites in clinical settings.

Calcium phosphate bone cements as local drug delivery systems for bone cancer treatment

Bone cancer is usually a metastatic disease, affecting people of all ages. Its effective therapy requires a targeted drug administration locally at the cancer site so that the surrounding healthy organs and tissues stay unharmed. Upon a thorough literature search, a tremendous number of published articles are reporting on development of calcium phosphate cements (CPCs) for the treatment of a variety of diseases, such as osteoporosis, osteoarthritis, osteomyelitis, and other musculoskeletal disorders. However, just a limited number of research employs CPCs specifically for bone cancer treatment. In this review article, we study the factors influencing the local drug release from CPCs and particularly focus on bone cancer therapy. Finally, we locate the deficiencies in the literature regarding this specific topic and propose which other perspectives should be considered and discussed in future articles.

Collaborative Design of MgO/FeOx Nanosheets on Titanium: Combining Therapy with Regeneration

The repair of bone defects caused by osteosarcoma resection remains a clinical challenge because of the tumor recurrence and bacterial infection. Combining tumor and bacterial therapy with bone regeneration properties in bone implants is a promising strategy for the treatment of osteosarcoma. Here, a layer of MgO/FeO_x nanosheet is constructed on the Ti implant to prevent tumor recurrence and bacterial infection, while simultaneously accelerating bone formation. This MgO/FeO_x double metal oxide demonstrates good peroxidase activity to catalyze H₂ O₂ , which is rich in tumor microenvironment, to form reactive oxygen species (ROS), and shows good photothermal conversion capacity to produce photothermal effect, thus synergistically killing tumor cells and eliminating tumor tissue. In addition, it generates a local alkaline surface microenvironment to inhibit the energy metabolism of bacteria to enhance the photothermal antibacterial effect. Furthermore, benefiting from the generation of a Mg ion-containing alkaline microenvironment, this MgO/FeO_x film can promote the osteogenic differentiation of osteoblast and angiogenesis of vascular endothelial cells in vitro as well as accelerated bone formation in vivo. This study proposes a multifunctional platform for integrating tumor and bacterial therapy and bone regeneration, which has good application prospects for the treatment of osteosarcoma.

Effects of Zinc, Magnesium, and Iron Ions on Bone Tissue Engineering

Large-sized bone defects are a great challenge in clinics and considerably impair the quality of patients' daily life. Tissue engineering strategies using cells, scaffolds, and bioactive molecules to regulate the microenvironment in bone regeneration is a promising approach. Zinc, magnesium, and iron ions are natural elements in bone tissue and participate in many physiological processes of bone metabolism and therefore have great potential for bone tissue engineering and regeneration. In this review, we performed a systematic analysis on the effects of zinc, magnesium, and iron ions in bone tissue engineering. We focus on the role of these ions in properties of scaffolds (mechanical strength, degradation, osteogenesis, antibacterial properties, etc.). We hope that our summary of the current research achievements and our notifications of potential strategies to improve the effects of zinc, magnesium, and iron ions in scaffolds for bone repair and regeneration will find new inspiration and breakthroughs to inspire future research.

Biomimetic porous scaffolds containing decellularized small intestinal submucosa and Sr2+/Fe3+co-doped hydroxyapatite accelerate angiogenesis/osteogenesis for bone regeneration

The design of bone scaffolds is predominately aimed to well reproduce the natural bony environment by imitating the architecture/composition of host bone. Such biomimetic biomaterials are gaining increasing attention and acknowledged quite promising for bone tissue engineering. Herein, novel biomimetic bone scaffolds containing decellularized small intestinal submucosa matrix (SIS-ECM) and Sr²⁺/Fe³⁺co-doped hydroxyapatite (SrFeHA) are fabricated for the first time by the sophisticated self-assembled mineralization procedure, followed by cross-linking and lyophilization post-treatments. The results indicate the constructed SIS/SrFeHA scaffolds are characterized by highly porous structures, rough microsurface and improved mechanical strength, as well as efficient releasing of bioactive Sr²⁺/Fe³⁺and ECM components. These favorable physico-chemical properties endow SIS/SrFeHA scaffolds with an architectural/componential biomimetic bony environment which appears to be highly beneficial for inducing angiogenesis/osteogenesis both in vitro and in vivo. In particular, the cellular functionality and bioactivity of endotheliocytes/osteoblasts are significantly enhanced by SIS/SrFeHA scaffolds, and the cranial defects model further verifies the potent ability of SIS/SrFeHA to accelerate in vivo vascularization and bone regeneration following implantation. In this view these results highlight the considerable angiogenesis/osteogenesis potential of biomimetic porous SIS/SrFeHA scaffolds for inducing bone regeneration and thus may afford a new promising alternative for bone tissue engineering.

Favorable osteogenic activity of iron doped in silicocarnotite bioceramic: In vitro and in vivo Studies

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The translational potential of this article

Accelerated biodegradation of iron-based implants via tantalum-implanted surface nanostructures

In recent years, pure iron (Fe) has attracted significant attention as a promising biodegradable orthopedic implant material due to its excellent mechanical and biological properties. However, in physiological conditions, Fe has an extremely slow degradation rate with localized and irregular degradation, which is problematic for practical applications. In this study, we developed a novel combination of a nanostructured surface topography and galvanic reaction to achieve uniform and accelerated degradation of an Fe implant. The target-ion induced plasma sputtering (TIPS) technique was applied on the Fe implant to introduce biologically compatible and electrochemically noble tantalum (Ta) onto its surface and develop surface nano-galvanic couples. Electrochemical tests revealed that the uniformly distributed nano-galvanic corrosion cells of the TIPS-treated sample (nano Ta–Fe) led to relatively uniform and accelerated surface degradation compared to that of bare Fe. Furthermore, the mechanical properties of nano Ta–Fe remained almost constant during a long-term in vitro immersion test (~40 weeks). Biocompatibility was also assessed on surfaces of bare Fe and nano Ta–Fe using in vitro osteoblast responses through direct and indirect contact assays and an in vivo rabbit femur medullary cavity implantation model. The results revealed that nano Ta–Fe not only enhanced cell adhesion and spreading on its surface, but also exhibited no signs of cellular or tissue toxicity. These results demonstrate the immense potential of Ta-implanted surface nanostructures as an effective solution for the practical application of Fe-based orthopedic implants, ensuring long-term biosafety and clinical efficacy.

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The degradation rate of nanostructured Fe implants was accelerated by TIPS technique.

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Ta ions were accelerated strongly toward the Fe surface by TIPS process.

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Nano Ta–Fe showed long-term mechanical stability and accelerated degradation rate.

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Nanostructured Ta–Fe surface showed enhanced in vitro and in vivo cellular responses.

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Ta-implanted Fe is a promising material for biodegradable orthopedic implants.

Sprayable β-FeSi2 composite hydrogel for portable skin tumor treatment and wound healing

The development of a rapid-forming in-situ sprayable hydrogel with the functions of tumor treatment and wound healing is essential for eliminating residual tumor tissue and promoting wound healing caused by surgical resection. On account of its semiconductor properties, β-FeSi₂ (FS) was widely explored as a thermoelectric material. In this work, FS was first applied as a bioactive material for the application of tissue engineering. Excitedly, we found that FS could be used as a novel antitumor agent. It exhibited excellent photothermal performance, and the released Fe ions could generate •OH under the acidic conditions and excessive H₂O₂ in the tumor microenvironment. Moreover, the sprayable β-FeSi₂-incorporated sodium alginate (FS/SA) hydrogel was prepared as an instant gelation after spraying in situ, contributing to timely tumor-induced skin wound healing and efficiently suppressing tumors through photothermal and chemodynamic therapy (PTT and CDT). Furthermore, the released bioactive Fe and Si ions could promote the migration and differentiation of endothelial cells and the pro-angiogenesis of skin wounds. Accordingly, such sprayable hydrogel played an effective role in emergency wound treatment with the advantage of convenience and portability. Overall, with incorporation of FS into the sprayable FS/SA hydrogel, the composite hydrogel possessed dual functions of tumor therapy and skin wound healing.

Scaffold 3D-Printed from Metallic Nanoparticles-Containing Ink Simultaneously Eradicates Tumor and Repairs Tumor-Associated Bone Defects

Bone metastasis occurs in about 70% of breast cancer patients. The surgical resection of metastatic tumors often leads to bone erosion and destruction, which greatly hinders the treatment and prognosis of breast cancer patients with bone metastasis. Herein, a bifunctional scaffold 3D-printed from nanoink is fabricated to simultaneously eliminate the tumor cells and repair the tumor-associated bone defects. The metallic polydopamine (PDA) nanoparticles (FeMg-NPs) may effectively load and sustainably release the metal ions Fe³⁺ and Mg²⁺ in situ. Fe³⁺ exerts a chemodynamic therapy to synergize with the photothermal therapy induced by PDA with effective photothermal conversion under NIR laser, which efficiently eliminates the bone-metastatic tumor. Meanwhile, the sustained release of osteoinductive Mg²⁺ from the bony porous 3D scaffold enhances the new bone formation in the bone defects. Taken together, the implantation of scaffold (FeMg-SC) 3D-printed from the FeMg-NPs-containing nanoink provides a novel strategy to simultaneously eradicate bone-metastatic tumor and repair the tumor-associated bone defects.

Integrated nanomaterials for non-invasive photothermal therapy of rheumatoid arthritis

Rheumatoid arthritis (RA) is a chronic systemic inflammatory autoimmune disease that causes swelling, redness, and arthralgia of multiple joints. Despite significant research and development on the treatment modalities for RA, there is still no established effective treatment option for eradicating joint damage and inflammation. In recent years, photothermal therapy (PTT) has emerged as a practical approach to treat RA. In this review, we outline various factors that affect the effective treatment of RA. Moreover, we discuss various PTT-based nanomaterials that can be used to treat RA.

Dual-Dynamic-Bond Cross-Linked Antibacterial Adhesive Hydrogel Sealants with On-Demand Removability for Post-Wound-Closure and Infected Wound Healing

The design and development of a smart bioadhesive hydrogel sealant with self-healing and excellent antibacterial activity to achieve high wound closure effectiveness and post-wound-closure care is highly desirable in clinical applications. In this work, a series of adhesive antioxidant antibacterial self-healing hydrogels with promising traits were designed through dual-dynamic-bond cross-linking among ferric iron (Fe), protocatechualdehyde (PA) containing catechol and aldehyde groups and quaternized chitosan (QCS) to enable the closure of skin incisions and promotion of methicillin-resistant Staphylococcus aureus (MRSA)-infected wound healing. The dual-dynamic-bond cross-linking of a pH-sensitive coordinate bond (catechol-Fe) and dynamic Schiff base bonds with reversible breakage and re-formation equips the hydrogel with excellent autonomous healing and on-demand dissolution or removal properties. Additionally, the hydrogel presents injectability, good biocompatibility and antibacterial activity, multifunctional adhesiveness, and hemostasis as well as NIR responsiveness. The in vivo evaluation in a rat skin incision model and infected full-thickness skin wound model revealed the high wound closure effectiveness and post-wound-closure care of the smart hydrogels, demonstrating its great potential in dealing with skin incisions and infected full-thickness skin wounds.

Bioactive Sr2+/Fe3+co-substituted hydroxyapatite in cryogenically 3D printed porous scaffolds for bone tissue engineering

Developing multi-doped bioceramics that possess biological multifunctionality is becoming increasingly attractive and promising for bone tissue engineering. In this view innovative Sr²⁺/Fe³⁺co-substituted nano-hydroxyapatite with gradient doping concentrations fixed at 10 mol% has been deliberately designed previously. Herein, to evaluate their therapeutic potentials for bone healing, novel gradient SrFeHA/PCL scaffolds are fabricated by extrusion cryogenic 3D printing technology with subsequent lyophilization. The obtained scaffolds exhibit desired 3D interconnected porous structure and rough microsurface, along with appreciable release of bioactive Sr²⁺/Fe³⁺from SrFeHA components. These favorable physicochemical properties render printed scaffolds realizing effective biological applications bothin vitroandin vivo, particularly the moderate co-substituted Sr7.5Fe2.5HA and Sr5Fe5HA groups exhibit remarkably enhanced bioactivity that not only promotes the functions of MC3T3 osteoblasts and HUVECs directly, but also energetically manipulates favorable macrophages activation to concurrently facilitate osteogenesis/angiogenesis. Moreover,in vivosubcutaneous implantation and cranial defects repair outcomes further confirm their superior capacity to dictate immune reaction, implants vascularization andin situbone regeneration, mainly dependent on the synergetic effects of released Sr²⁺/Fe³⁺. Accordingly, for the first time, present study highlights the great potential of Sr7.5Fe2.5HA and Sr5Fe5HA for ameliorating bone regeneration process by coupling of immunomodulation with enhanced angio- and osteogenesis and hence may provide a new promising alternative for future bone tissue engineering.

A thermostability perspective on enhancing physicochemical and cytological characteristics of octacalcium phosphate by doping iron and strontium

Investigation of thermostability will lead the groundbreaking of unraveling the mechanism of influence of ion-doping on the properties of calcium phosphates. In this work, octacalcium phosphate (OCP), a metastable precursor of biological apatite, was used as a stability model for doping ions (Fe³⁺ and Sr²⁺) with different ionic charges and radii. After treated under hot air at different temperatures (110–200 °C), the phase, morphology, structure, physicochemical properties, protein affinity, ions release, and cytological responses of the ion-doped OCPs were investigated comparatively. The results showed that the collapse of OCP crystals gradually occurred, accompanying with the dehydration of hydrated layers and the disintegration of plate-like crystals as the temperature increased. The collapsed crystals still retained the typical properties of OCP and the potential of conversion into hydroxyapatite. Compared to the undoped OCP, Fe-OCP, and Sr-OCP had lower and higher thermostability respectively, leading to different material surface properties and ions release. The adjusted thermostability of Fe-OCP and Sr-OCP significantly enhanced the adsorption of proteins (BSA and LSZ) and the cytological behavior (adhesion, spreading, proliferation, and osteogenic differentiation) of bone marrow mesenchymal stem cells to a varying extent under the synergistic effects of corresponding surface characteristics and early active ions release. This work paves the way for understanding the modification mechanism of calcium phosphates utilizing ion doping strategy and developing bioactive OCP-based materials for tissue repair.

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OCP was used as a stability model for doping ions with different charges and radii.

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Collapse of OCP crystals occurred with structural dehydration after heat treatment.

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Fe and Sr doping altered the thermostability of OCP crystals in an opposite way.

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The thermostable difference affected the surface properties and ion release of OCP.

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Active surface and ion release of OCP synergistically mediated its biocompatibility.

β-FeOOH/Fe-TiO2 heterojunctions on Ti for bacteria inactivation under light irradiation and biosealing

Intraosseous transcutaneous implants transferring mechanical stress directly from the skeleton to a prosthesis are an area of biological mechanics. However, bacterial invasion and weak biosealing with skin tissue usually induce implant failure. In this paper, composite coatings consisting of β-FeOOH as an outer layer and Fe-TiO₂ as an inner layer were prepared on Ti via micro-arc oxidation and hydrothermal treatment (HT). The surface microstructures and optical absorption properties of the coatings were observed, the production of reactive oxygen species (ROS) was measured, Staphylococcus aureus (S. aureus) and fibroblast behaviors were studied in vitro, and bacteria inactivation and skin tissue responses on different surfaces were evaluated in vivo. The results show that Fe³⁺ was doped into TiO₂ and β-FeOOH nanoparticles were gradually deposited on TiO₂ during HT treatment, forming β-FeOOH/Fe-TiO₂ heterojunctions. The light absorption of the composite coatings shifted to the longer wavelength region because of a narrowed TiO₂ bandgap and the formation of heterojunctions. Under light irradiation, photoinduced electrons and holes on the heterojunctions were separated efficiently. Via optimizing the amount of Fe³⁺ in TiO₂, ROS that formed at the heterojunctions after light irradiation for 10 min could kill 80% of S. aureus compared with pure Ti in vitro, but they did not affect fibroblast behavior, including proliferation and phenotyping. In vivo, the optimized β-FeOOH/Fe-TiO₂ heterojunctions, upon light irradiation, could inhibit bacterial infection, suppress an inflammatory response, and promote integration with skin tissue. Such results provide a new perspective suggesting the potential application of β-FeOOH/Fe-TiO₂ heterojunctions in percutaneous Ti implants, especially in infected cases.

Preparation and Characterization of Iron-Doped Tricalcium Silicate-Based Bone Cement as a Bone Repair Material

Iron is one of the trace elements required by human body, and its deficiency can lead to abnormal bone metabolism. In this study, the effect of iron ions on the properties of tricalcium silicate bone cement (Fe/C3Ss) was investigated. It effectively solved the problems of high pH value and low biological activity of calcium silicate bone cement. The mechanical properties, in vitro mineralization ability and biocompatibility of the materials were systematically characterized. The results indicate that tricalcium silicate bone cement containing 5 mol% iron displayed good self-setting ability, mechanical properties and biodegradation performance in vitro. Compared with pure calcium silicate bone cement (C3Ss), Fe/C3Ss showed lower pH value (8.80) and higher porosity (45%), which was suitable for subsequent cell growth. Immersion test in vitro also confirmed its good ability to induce hydroxyapatite formation. Furthermore, cell culture experiments performed with Fe/C3Ss ion extracts clearly stated that the material had excellent cell proliferation abilities compared to C3Ss and low toxicity. The findings reveal that iron-doped tricalcium silicate bone cement is a promising bioactive material in bone repair applications.

Magnetic Calcium Phosphate Cement for Hyperthermia Treatment of Bone Tumors

This article reports, for the first time, the 'proof-of-concept' results on magnetic monetite (CaHPO4)-based calcium phosphate cements (CPCs) compositions developed for the hyperthermia treatment of bone tumors. Hyperthermia involves the heating of a tumor within a temperature range of 40-45 °C, inducing apoptosis in the tumor cells. This process holds promising potential in the field of cancer treatment and has been proven to be more effective than conventional therapeutics. Hence, we aimed to develop cement compositions that are capable of the hyperthermia treatment of bone tumors. To achieve that central goal, we incorporated iron oxide (Fe3O4), a ferromagnetic material, into monetite and hypothesized that, upon the application of a magnetic field, magnetite will generate heat and ablate the tumor cells near the implantation site. The results confirmed that an optimized content of magnetite incorporation in monetite can generate heat in the range of 40-45 °C upon the application of a magnetic field. Furthermore, the compositions were bioactive and cytocompatible with an osteoblastic cell line.

Analysis of the osteogenic and mechanical characteristics of iron (Fe2+/Fe3+)-doped β‑calcium pyrophosphate

The calcium phosphate is the main mineral constituent of bone. Although there has been significant amount of research on finding ideal synthetic bone, no suitable scaffold material has yet been found. In this investigation, the iron doped brushite (CaHPO₄·2H₂O) has been investigated for osteogenic potential and mechanical properties. The synthesis of iron-oxide doping in the form of Fe^2+,3+-ions were carried out using the solution based method in which the ammonium hydrogen phosphate and calcium nitrate solutions were used in stoichiometric ratio for synthesizing CaHPO₄·2H₂O, with doping concentrations of Fe^2+,3+-ions between 5 mol% and 30 mol%. The synthesized powders were analysed using X-ray powder diffraction, FTIR, SEM and Raman spectroscopic techniques. The heat treatment of synthesized powder was carried out at 1000 °C in air for 5 h, and it was found that the dominant crystalline phase in samples with <20 mol% was β-CPP, which also formed an iron-rich solid solution phase. Increasing the concentrations of Fe^2+,3+-ions enhances the phase fraction of FePO₄ and amorphous phase. Amongst the Fe^2+,3+-doped β-CPP minerals, it was found that the 10 mol% Fe^2+,3+-doped β-CPP offers the best combination of bio-mechanical and osteogenic properties as a scaffold for bone tissue regenerative engineering.

Improved osteogenesis and angiogenesis of a novel copper ions doped calcium phosphate cement

Improving the angio1genesis potential of bone-repairing materials is vital for the repair of cancerous bone defects. It can further facilitate the delivery of active substances with osteogenesis and anti-tumor functions, ultimately promoting the formation of new bone tissues. Copper ions (Cu²⁺) have been proved to be beneficial to angiogenesis. This study developed a new type of Cu-containing calcium phosphate cement (Cu-CPC) by incorporating with copper phosphate (CuP) nanoparticles with a photothermal anti-tumor effect. The results revealed that the main phases of all hydrated CPCs were hydroxyapatite, unreacted tricalcium phosphate and calcium carbonate. But the hydration products of CPC became thinner after the incorporation of Cu²⁺. With the increase of CuP concentration, the setting time of CPC was prolonged while the injectability and the compressive strength were increased. The release concentration of Cu²⁺in vitro was among 0.01 to 0.74 mg/mL, which showed a positive relation with CuP content. Mouse bone marrow stromal cells (mBMSCs) displayed higher adhesion activity, proliferation performance and expression of osteogenic genes and proteins on CPC with 0.01 wt% CuP (0.01Cu-CPC) and 0.05 wt% CuP (0.05Cu-CPC). When human umbilical vein endothelial cells were co-cultured with 0.01Cu-CPC and 0.05Cu-CPC extracts, the proliferation and angiogenesis-related gene and protein expression were significantly increased, and the in vitro tube formation capacity was promoted. However, higher CuP content inhibited the proliferation of mBMSCs. In conclusion, CPC with 0.01 wt% and 0.05 wt% CuP nanoparticles has the potential to promote bone formation around cancerous bone defects, which would be promising for bone regeneration and treatment of bone tumors.

Ferric oxide: A favorable additive to balance mechanical strength and biological activity of silicocarnotite bioceramic

Ideal materials for bone regeneration should have not only a good bioactivity, but also a good mechanical strength to provide an initial support for new bone formation. How to get a balance between high mechanical property and good bioactivity is a challenging issue for bone regeneration materials. In the present work, a biocompatible additive Fe₂O₃ was selected to optimize the comprehensive properties of a novel calcium phosphate silicate (CPS) ceramic using a mechanical mixing method. The effects of Fe₂O₃ content on microstructure, bending strength, apatite formation ability and cytocompatibility of Fe-CPS bioceramics were investigated and the related mechanism was also discussed. The obtained Fe-CPS bioceramics showed enhanced mechanical and favorable bioactivity performances. Especially, the Fe-CPS bioceramic with 1.5 wt% Fe₂O₃ sintered at 1250 °C presented the highest bending strength of 91.9 MPa. While, Fe-CPS bioceramics still exhibited a good ability on apatite formation in simulated body fluid (SBF), and cytocompatibility test revealed that Fe-CPS bioceramics were favorable for cell adhesion and proliferation. All the results indicated that Fe-CPS bioceramics are promising candidate materials for bone regeneration at load bearing applications.

Integrating silicon/zinc dual elements with PLGA microspheres in calcium phosphate cement scaffolds synergistically enhances bone regeneration

Integrating multiple pro-osteogenic factors into bone graft substitutes is a practical and effective approach to improve bone repair efficacy. Here, Si-Zn dual elements and PLGA microspheres were incorporated into calcium phosphate cement (CPC) scaffolds (PLGA/CPC-Si/Zn) as a novel strategy to synergistically enhance bone regeneration. The incorporation of PLGA microspheres and Si/Zn dual elements within CPC scaffolds improved the setting time, injectability and compressive strength. The PLGA/CPC-Si/Zn scaffolds displayed controlled sequential release of Si and Zn ions. In vitro, RAW 264.7 cells displayed the M2 phenotype with a high level of anti-inflammatory cytokines in response to PLGA/CPC-Si/Zn. The conditioned medium of RAW 264.7 cells cultured on the PLGA/CPC-Si/Zn scaffolds significantly enhanced the osteogenic differentiation of rat BMSCs. In a rat femur defect model, the implanted PLGA/CPC-Si/Zn scaffolds led to obvious new bone formation after 4 weeks, apparent bone ingrowth into the PLGA microspheres after 12 weeks, and was almost completely filled with mature new bone upon degradation of the PLGA microspheres at 24 weeks. These findings demonstrate that the PLGA/CPC-Si/Zn scaffolds promote osteogenesis by synergistically improving the immune microenvironment and biodegradability. Hence, integrating multiple trace elements together with degradable components within bone graft biomaterials can be an effective strategy for promoting bone regeneration.

Three-Dimensional-Printed Bioceramic Scaffolds with Osteogenic Activity for Simultaneous Photo/Magnetothermal Therapy of Bone Tumors

For the postoperative treatment of bone cancer, biomaterials should possess an antitumor effect and simultaneous repair ability of bone defects. Compared with single photothermal treatment or magnetothermal treatment, photo/magnetothermal joint treatment represents a more high-efficient strategy to kill tumor cells. In this work, a 3D-printed bioceramic scaffold with a photo/magnetothermal effect was successfully designed and fabricated, which exhibited the function of killing tumor cells and excellent osteogenic bioactivity, via incorporating an Fe element into akermanite (AKT) bioceramics. After doping with ferric elements, the AKT scaffolds possessed significantly enhanced compressive strength and desirable ferromagnetic property. The ferric elements endowed the AKT scaffolds with excellent photo/magnetothermal effects, and hence the scaffolds could efficiently kill tumor cells in vitro under mild laser power density and magnetic field. In addition, the Fe-doped AKT bioceramic scaffolds significantly promoted cell proliferation and osteogenic differentiation of rabbit bone mesenchymal stem cells as compared with the original AKT scaffolds without Fe elements. The results suggest that Fe-doped bioceramic scaffolds with both photo/magnetothermal effect and in vitro osteogenic bioactivity could be a promising biomaterial for the synergistic therapy of bone cancers.

Concentration-dependent osteogenic and angiogenic biological performances of calcium phosphate cement modified with copper ions

Development of multifunctional bone grafting biomaterials with both osteogenesis and angiogenesis properties have earned increasing interest in the field of regenerative medicine. In the present investigation, copper-doped β-tricalcium phosphate (Cu-TCP) powders were successfully synthesized. And Cu-containing calcium phosphate cement (Cu-CPC) was acquired through uniformly mixing CPC and Cu-TCP powders, with Cu-TCP serving as the donor of Cu²⁺. Cu-CPC exhibited suitable setting time, and the incorporation of Cu-TCP aggregating into CPC exhibited positive effect on the compressive strength while Cu²⁺ was in lower concentration. Investigation results showed that Cu-CPC had relatively low releasing amount of Cu²⁺, which was attributed to the re-bonding of Cu²⁺ into the newly formed HA crystals on surface. In vitro osteogenesis and angiogenesis properties of Cu-CPC were systematically evaluated through co-culture with mouse bone marrow stromal cells (mBMSCs) and human umbilical vein endothelial cells (HUVECs) respectively. The results indicated dose-dependent biological functions of Cu²⁺ in Cu-CPCs. The mBMSCs and HUVECs showed well activity and attachment morphology on TCP/CPC, 0.05 Cu-TCP/CPC, 0.1 Cu-TCP/CPC. The upregulated osteogenic-related genes expression and angiogenic-related genes expression were detected with lower Cu²⁺ content. Taken together, Cu-containing CPC is of great potential for the regeneration of vascularized new bone.

Preparation and cytocompatibility of a novel bismuth aluminate/calcium phosphate cement with high radiopacity

In a minimally invasive surgery, using a bone cement being radiologically detectable is vital to the success of the procedure and avoiding cement leakage in the early stage. The radiopacity of calcium phosphate cement (CPC) is inadequate, thus limiting its clinic application in this area. In this work, bismuth aluminate (BiA) was employed as a radiopaque agent for CPC. The influences of BiA on physicochemical, radiopaque and in vitro biocompatible properties of CPC were investigated. With the increasing content of BiA, the setting time and the compressive strength of CPC were augmented, while the injectability of the cement pastes was reduced. The radiopacity of CPC was significantly improved by adding more than 6 wt.% BiA. CPC specimens with less than 12 wt.% BiA showed good cellular affinity. Moreover, the CPC containing 6 and 9 wt.% BiA promoted the cell growth and ALP activity of mouse bone marrow mesenchymal stem cells when compared with the control. On the basis of its improved radiopacity and cytocompatibility, the radiopaque CPC with 6 ~ 9 wt.% BiA is expected to be a potential substitute for bone defect restoration via minimally invasive surgery. CPC with bismuth aluminate reveals better radiopacity and cell affinity along with proper physicochemical properties.

Intrinsically ferromagnetic Fe-doped TiO2 coatings on titanium for accelerating osteoblast response in vitro

The microenvironment can regulate osteoblast behavior during integration of implants with host bones. An intrinsically magnetic field induced by an Fe³⁺ doped TiO₂ coating was applied herein to enhance the cytocompatibility of Ti. Porous TiO₂ incorporated with different amounts of Fe (2.27-11.07 wt%) was directly prepared on Ti by micro-arc oxidation. The microstructure, roughness, wettability, ion releasing and magnetic property of TiO₂ coatings were investigated. Cell behavior, including adhesion, proliferation, differentiation, collagen secretion and extracellular matrix mineralization on coating surfaces was evaluated. The results show that incorporation of Fe³⁺ did not significantly alter the phase component, topography, roughness and wettability of coatings, and with increased doses of Fe³⁺, trace amounts of Fe³⁺ were released into the media, whereas the Ca²⁺ accumulation concentration slightly decreased. Fe-Doped TiO₂ displayed a weak ferromagnetic property, and its saturation magnetization value increased initially and then decreased with the increased dose of Fe. Compared with the undoped, proliferation, expression of osteogenesis-related genes, collagen secretion and extracellular matrix mineralization of osteoblasts were enhanced with Fe doped ones, especially for those with 4.25 wt% Fe. By analyzing the structures and properties of different surfaces and their osteoblast responses, it is deduced that the ferromagnetism of Fe doped TiO₂ plays a key role in enhancing osteoblast behavior. Such a result provides a new perspective for the potential application of ferromagnetic coatings in bone repair.

Engineered Fe(OH)3 nanoparticle-coated and rhBMP-2-releasing PLGA microsphere scaffolds for promoting bone regeneration by facilitating cell homing and osteogenic differentiation

Iron facilitates cell homing and enhances the capacity of rhBMP-2.

In vitro model of potential metal cation exchanges in biological apatite

Biological apatite is ion-doped and provides an active pool for the exchange with foreign impurity ions. In this work, an in vitro model of hydrated metastable octacalcium phosphate (OCP) crystals was established to mimetically investigate the distinct exchange of trivalent and divalent cations (Fe³⁺ and Sr²⁺) with biological apatite. Fe³⁺ significantly promoted the collapses of OCP crystals and the formation of amorphous sol-like ferric phosphates, while Sr²⁺ facilitated the epitaxial growth and stability of OCP crystals. The involvement of Ca²⁺ maintained the crystalline integrity and inhibited the ion exchange within OCP crystals. This in vitro model would lay the foundation for the further investigation of the metabolism of biological apatite.

Competing Roles of Substrate Composition, Microstructure, and Sustained Strontium Release in Directing Osteogenic Differentiation of hMSCs

Strontium releasing bioactive ceramics constitute an important class of biomaterials for osteoporosis treatment. In the present study, we evaluated the synthesis, phase assemblage, and magnetic properties of strontium hexaferrite, SrFe₁₂O₁₉, (SrFe) nanoparticles. On the biocompatibility front, the size- and dose-dependent cytotoxicity of SrFe against human mesenchymal stem cells (hMSCs) were investigated. After establishing their non-toxic nature, we used the strontium hexaferrite nanoparticles (SrFeNPs) in varying amount (x = 0, 10, and 20 wt %) to consolidate bioactive composites with hydroxyapatite (HA) by multi-stage spark plasma sintering (SPS). Rietveld refinement of these spark plasma sintered composites revealed a near complete decomposition of SrFe₁₂O₁₉ to magnetite (Fe₃O₄) along with a marked increase in the unit cell volume of HA, commensurate with strontium-doped HA. The cytocompatibility of SrHA-Fe composites with hMSCs was assessed using qualitative and quantitative morphological analysis along with phenotypic and genotypic expression for stem cell differentiation. A marked decrease in the stemness of hMSCs, indicated by reduced vimentin expression and acquisition of osteogenic phenotype, evinced by alkaline phosphatase (ALP) and collagen deposition was recorded on SrHA-Fe composites in osteoinductive culture. A significant upregulation of osteogenic marker genes (Runx2, ALP and OPN) was detected in case of the SrHA-Fe composites, whereas OCN and Col IA expression were similarly high for baseline HA. However, matrix mineralization was elevated on SrHA-Fe composites in commensurate with the release of Sr²⁺ and Fe²⁺. Summarizing, the current work is the first report of strontium hexaferrite as a non-toxic nanobiomaterial. Also, SrHA-based iron oxide composites can potentially better facilitate bone formation, when compared to pristine HA.

Iron doped β-Tricalcium phosphate: Synthesis, characterization, hyperthermia effect, biocompatibility and mechanical evaluation

The ability of β-Tricalcium phosphate [β-TCP, β-Ca₃(PO₄)₂] to host iron at its structural lattice and its associated magnetic susceptibility, hyperthermia effect, biocompatibility and mechanical characteristics is investigated. The studies revealed the ability of β-Ca₃(PO₄)₂ to host 5.02mol% of Fe³⁺ at its Ca²⁺(5) site. Excess Fe³⁺ additions led to the formation of trigonal Ca₉Fe(PO₄)₇ and moreover a minor amount of CaFe₃(PO₄)₃O crystallization was also observed. A gradual increment in the iron content at β-Ca₃(PO₄)₂ results in the simultaneous effect of pronounced hyperthermia effect and mechanical stability. However, the presence of CaFe₃(PO₄)₃O contributes for the reduced hyperthermia effect and mechanical stability of iron substituted β-Ca₃(PO₄)₂. Haemolytic tests, cytotoxicity tests and ALP gene expression analysis confirmed the biocompatibility of the investigated systems.