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One way to effectively address endophyte infection and loosening is the creation of multifunctional coatings that combine anti-inflammatory, antibacterial, and vascularized osteogenesis. This study started with the preparation of strontium-doped titanium dioxide nanotubes (STN) on the titanium surface. Next, tannic acid (TA), gentamicin sulfate (GS), and pluronic F127 (PF127) were successfully loaded into the STN via layer-by-layer self-assembly, resulting in the STN@TA-GS/PF composite coatings. The findings demonstrated the excellent hydrophilicity and bioactivity of the STN@TA-GS/PF coating. STN@TA-GS/PF inhibited E. coli and S. aureus in vitro to a degree of roughly 80.95 % and 92.45 %, respectively. Cellular investigations revealed that on the STN@TA-GS/PF surface, the immune-system-related RAW264.7, the vasculogenic HUVEC, and the osteogenic MC3T3-E1 showed good adhesion and proliferation activities. STN@TA-GS/PF may influence RAW264.7 polarization toward the M2-type and encourage MC3T3-E1 differentiation toward osteogenesis at the molecular level. Meanwhile, the STN@TA-GS/PF coating achieved effective removal of ROS within HUVEC and significantly promoted angiogenesis. In both infected and non-infected bone defect models, the STN@TA-GS/PF material demonstrated strong anti-inflammatory, antibacterial, and vascularization-promoting osteogenesis properties. In addition, STN@TA-GS/PF had good hemocompatibility and biosafety. The three-step process used in this study to modify the titanium surface for several purposes gave rise to a novel concept for the clinical design of antimicrobial coatings with immunomodulatory properties., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

The application of titanium (Ti) implants for patients with diabetes mellitus (DM) is still facing a significant challenge due to obstacles such as hyperglycemia, reactive oxygen species (ROS), and chronic inflammation, which hinders osseointegration. To address this issue, a Ti implant with dual functions of regulating polarization of macrophages and facilitating osseointergration is developed via hydrothermal reaction and hydrogel coating. The reactive oxygen species (ROS) and glucose (Glu) responsive hydrogel coating can locally deliver adenosine (ADO) in the early stage of implantation. The controlled release of ADO regulated the phenotype of macrophages, restored oxidative balance, and enhanced mitochondrial function during the early stages of implantation. Subsequently, strontium (Sr) ions will be released to promote osteogenic differentiation and proliferation of mesenchymal stem cells (MSCs), as the hydrogel coating degraded. It eventually leads to bone reconstruction during the late stages, aligning with the biological cascade of bone healing. The modified Ti implants showed effective osteogenesis for bone defects in DM patients, shedding light on the design and biological mechanisms of surface modification. This research offers promising potential for improving the treatment of bone-related complications in diabetic patients., (© 2024 Wiley‐VCH GmbH.)

Osteoporotic fractures and arthritis represent a major socioeconomic health burden. Fragility fracture fixation and joint replacement are often undertaken using titanium (Ti) or Ti alloy implants. Ideally these should induce bone formation and reduce osteoclast formation. Nanoscale topographies are potent inducers of osteogenesis, and strontium (Sr) has both osteogenic and antiosteoclastic effects. We incorporated strontium into a titanium surface with an osteogenic disordered nanoscale topography. The surface comprises 120 nm diameter, 100 nm deep pits in a near-square order with deliberate offset from the center pit position up to ±50 nm, providing a pattern with an average center-center pit spacing of 300 nm (called near-square 50, NSQ50). Several surfaces were assessed, including NSQ50 alone, strontium incorporated alone, and combined, compared with control surfaces. We assessed the surfaces using a human bone marrow stromal cell (BMSC)/ bone marrow hematopoietic cell (BHSC) coculture capable of osteogenesis and osteoclastogenesis. The samples eluted Sr over long-term culture, and uptake of Sr was better with eluted Sr than with Sr added to the culture media. The NSQ50 pattern in Ti was osteogenic, and addition of Sr elution increased osteogenesis further for both flat and NSQ50 samples. Interestingly, BMSCs on all Ti samples did not secrete the receptor activator of nuclear factor kappa-Β ligand (RANKL) or macrophage colony-stimulating factor (M-CSF) while secreting osteoprotegrin (OPG) at high levels. This meant that no osteoclast formation was observed on any Ti surface. Therefore, using Sr-incorporated nanotopographical imprinting, we generated highly osteogenic Ti surfaces that inhibited osteoclast formation.

Endowing titanium surfaces with multifunctional properties can reduce implant-related infections and enhance osseointegration. In this study, titanium dioxide nanotubes with strontium doping (STN) were first created on the titanium surface using anodic oxidation and hydrothermal synthesis techniques. Next, casein phosphopeptide (CCP) and an antimicrobial peptide (HHC36) were loaded into the STN with the aid of vacuum physical adsorption (STN-CP-H), giving the titanium surface a dual function of "antimicrobial-osteogenic". The surface of STN-CP-H has a suitable roughness and good hydrophilicity, which is conducive to osteoblasts. STN-CP-H had a 99 % antibacterial rate against S. aureus and E. coli and effectively prevented the growth of bacterial biofilm. Meanwhile, the antibacterial mechanism of STN-CP-H was initially explored with the help of transcriptome sequencing technology. STN-CP-H could greatly increase osteoblast adhesion, proliferation, and expression of osteogenic markers (alkaline phosphatase, runt-related transcription) when CCP and Sr worked together synergistically. In vivo, the STN-CP-H coating could effectively promote new osteogenesis around titanium implant bone and had no toxic effects on heart, liver, spleen, lung and kidney tissues. A potential anti-infection bone healing material, STN-CP-H bifunctional coating developed in this work efficiently inhibited bacterial infection of titanium implants and encouraged early osseointegration., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Inc. All rights reserved.)

Bone defects, resulting from trauma, inflammation, tumors, and various other factors, affect both health and quality of life. Although autologous bone transplantation is the gold-standard treatment for bone defects, it has disadvantages such as donor site limitations, prolonged surgical durations, and potential complications, necessitating the development of alternative bone tissue engineering materials. In this study, we used 3D printing technology to fabricate porous titanium implants characterized by superior biocompatibility and mechanical properties. Sodium alginate (SA) and strontium ions (Sr 2+ ) were integrated into mineralized collagen matrices (MCs) to develop strontium-functionalized alginate-mineralized collagen hydrogels (SAMs) with high mechanical strength and sustained metal ion release ability. SAMs were seamlessly incorporated into the porous structures of 3D-printed titanium scaffolds, establishing a novel organic-inorganic bioactive interface. This composite system exhibited high biocompatibility in vitro and increased the expression of genes important for osteogenic differentiation and angiogenesis. In a rabbit model of femoral defect, the titanium implants effectively promoted bone and vascular regeneration on their surface, highlighting their potential in facilitating bone-implant integration., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

Titanium and its alloys are widely used as orthopedic implants owing to their good mechanical properties and excellent corrosion resistance. However, the insufficient osteogenic activity and antibacterial properties hinder their clinical applications. To address these issues, TiO 2 nanotube arrays (TNT) were first fabricated on the TA2 alloy surface via an anodizing technique, and strontium ions (Sr 2+ ) were then loaded by hydrothermal reaction (TNT + Sr) and annealing treatment (TNT + A). Subsequently, the polydopamine layer (TNT + PDA) was constructed to immobilize the carboxymethyl chitosan and alendronate sodium (TNT + CA) mixture. The prepared coatings were thoroughly characterized by scanning electron microscopy (SEM), energy dispersive spectrometer (EDS), X-ray photoelectron spectrometer (XPS), attenuated total reflection-Fourier transform infrared spectroscopy (ATR-FTIR), X-ray diffractometer (XRD), and water contact angle measurement. The results confirmed that Sr 2+ ions, polydopamine, and carboxymethyl chitosan/alendronate sodium were successfully immobilized on the nanotubes. The coating of TNT + CA significantly enhanced the hydrophilicity, and effectively delayed the release of Sr 2+ and alendronate. The TNT + CA coating significantly promoted osteoblast adhesion and proliferation, and up-regulated the expressions of alkaline phosphatase (ALP), osteocalcin (OCN), and osteoblast-specific transcription factor (RUNX2). TNT + CA was able to rapidly induce in situ hydroxyapatite deposition from the simulated body fluid (SBF). Moreover, TNT + CA coating showed inhibition against Escherichia coli and Staphylococcus aureus (especially against Escherichia coli). The prepared TNT + CA coating provides a novel strategy for enhancing bone affinity, improving osteoblast behaviors, and antibacterial properties of titanium-based biomaterials., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

Objectives: This study aimed to investigate the osseointegration of titanium (Ti) implants with micro-nano textured surfaces functionalized with strontium additions (Sr) in a pre-clinical rat tibia model., Methodology: Ti commercially pure (cp-Ti) implants were installed bilaterally in the tibia of 64 Holtzman rats, divided into four experimental groups (n=16/group): (1) Machined surface - control (C); (2) Micro-nano textured surface treatment (MN); (3) Micro-nano textured surface with Sr2+ addition (MNSr); and (4) Micro-nano textured surface with a higher complementary addition of Sr2+ (MNSr+). In total, two experimental euthanasia periods were assessed at 15 and 45 days (n=8/period). The tibia was subjected to micro-computed tomography (μ-CT), histomorphometry with the EXAKT system, removal torque (TR) testing, and gene expression analysis by PCR-Array of 84 osteogenic markers. Gene expression and protein production of bone markers were performed in an in vitro model with MC3T3-E1 cells. The surface characteristics of the implants were evaluated by scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), and laser scanning confocal microscopy., Results: SEM, confocal, and EDS analyses demonstrated the formation of uniform micro-nano textured surfaces in the MN group and Sr addition in the MNSr and MNSr+ groups. TR test indicated greater osseointegration in the 45-day period for treated surfaces. Histological analysis highlighted the benefits of the treatments, especially in cortical bone, in which an increase in bone-implant contact was found in groups MN (15 days) and MNSr (45 days) compared to the control group. Gene expression analysis of osteogenic activity markers showed modulation of various osteogenesis-related genes. According to the in vitro model, RT-qPCR and ELISA demonstrated that the treatments favored gene expression and production of osteoblastic differentiation markers., Conclusions: Micro-nano textured surface and Sr addition can effectively improve and accelerate implant osseointegration and is, therefore, an attractive approach to modifying titanium implant surfaces with significant potential in clinical practice.

The primary emphasis of this study was on the innovative and scientifically valuable hydrothermal synthesis of MIL-101(Co) as a metal-organic framework (MOF) material. Subsequently, the CuFe 2 O 4 was incorporated into the MOF by a reduction-precipitation technique. The SrTiO 3 /CuFe 2 O 4 /MIL-101(Co) composite was synthesized by using hydrothermal in situ growth process. The XRD and FESEM investigations of the SrTiO 3 /CuFe 2 O 4 /MIL-101(Co) composite definitively verified its crystalline structure and proved its production with exact shape and dimensions. The data indicated that Candida albicans displayed the greatest vulnerability to all three produced materials, with reported Minimum Inhibitory Concentration (MIC) values of 500 µg mL -1 for MIL-101(Co). The CuFe 2 O 4 /MIL-101(Co) compound, when produced, exhibits MIC values of 200 µg mL -1 . Additionally, the combination of CuFe 2 O 4 /MIL-101(Co) with SrTiO 3 , shows MIC values of 50 µg mL -1 . The results also indicated that the MIC values for MIL-101(Co), and CuFe 2 O 4 /MIL-101(Co) against S. aureus were 100 µg mL -1 . Ultimately, SrTiO 3 /CuFe 2 O 4 /MIL-101(Co) exhibited identical MIC values of 50 µg mL -1 against S. aureus. The concentration of the bacterial protein was increased by adding MIL-101(Co), CuFe 2 O 4 /MIL-101(Co), and SrTiO 3 /CuFe 2 O 4 /MIL-101(Co). The antibacterial capabilities of the SrTiO 3 /CuFe 2 O 4 /MIL-101(Co) were increased after being subjected to gamma doses of 100.0 kGy. This process paves a ways for manufacturing innovation in near future., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

Bone tissue engineering offers a promising alternative to stimulate the regeneration of damaged tissue, overcoming the limitations of conventional autografts and allografts. Recently, titanium alloy (Ti) implants have garnered significant attention for treating critical-sized bone defects, especially with the advancement of 3D printing technology. Although Ti alloys have impressive versatility, their lack of cellular adhesion, osteogenic and antibacterial properties are significant factors that contribute to their failure. Hence, to overcome these obstacles, this study aimed to incorporate osteoinductive and antibacterial cue-loaded hydrogels into 3D-printed Ti (3D-Ti) scaffolds. 3D-Ti scaffolds were synthesized using the direct metal laser sintering method and loaded with a gelatin (Gel) hydrogel containing strontium-doped silver nanoparticles (Sr-Ag NPs). Compared with Ag NPs, Sr-doped Ag NPs increased the expression of Runx2 mRNA, which is a key bone transcription factor. We subjected the bioactive 3D-hybrid scaffolds (3D-Ti/Gel/Sr-Ag NPs) to physicochemical and material characterization, followed by cytocompatibility and osteogenic evaluation. The microporous and macroporous topographies of the scaffolds with Sr-Ag NPs showed increased Runx2 expression and matrix mineralization, with potent antibacterial properties. Therefore, the 3D-Ti scaffolds incorporated with Sr-Ag NP-loaded Gel hydrogels favored osteoblast differentiation and antibacterial activity, indicating their potential for orthopedic applications., (© 2024 Wiley‐VCH GmbH.)

Objectives: To explore the antimicrobial potential of strontium (Sr)-functionalized wafers against multiple bacteria associated with per-implant infections, in both mono- and multispecies biofilms., Materials and Methods: The bactericidal and bacteriostatic effect of silicon wafers functionalized with a strontium titanium oxygen coating (Sr-Ti-O) or covered only with Ti (controls) against several bacteria, either grown as a mono-species or multispecies biofilms, was assessed using a bacterial viability assay and a plate counting method. Mono-species biofilms were assessed after 2 and 24 h, while the antimicrobial effect on multispecies biofilms was assessed at Days 1, 3, and 6. The impact of Sr functionalization on the total percentage of Porphyromonas gingivalis in the multispecies biofilm, using qPCR, and gingipain activity was also assessed., Results: Sr-functionalized wafers, compared to controls, were associated with statistically significant less viable cells in both mono- and multispecies tests. The number of colony forming units (CFUs) within the biofilm was significantly less in Sr-functionalized wafers, compared to control wafers, for Staphylococcus aureus at all time points of evaluation and for Escherichia coli at Day 1. Gingipain activity was less in Sr-functionalized wafers, compared to control wafers, and the qPCR showed that P. gingivalis remained below detection levels at Sr-functionalized wafers, while it consisted of 15% of the total biofilm on control wafers at Day 6., Conclusion: Sr functionalization displayed promising antimicrobial potential, possessing bactericidal and bacteriostatic ability against bacteria associated with peri-implantitis grown either as mono-species or mixed in a multispecies consortium with several common oral microorganisms., (© 2024 The Author(s). Clinical and Experimental Dental Research published by John Wiley & Sons Ltd.)

Titanium-based orthopedic implants are gaining popularity in recent years due to their excellent biocompatibility, superior corrosion resistance and lightweight properties. However, these implants often fail to perform effectively due to poor osseointegration. Nanosurface modification approaches may help to resolve this problem. In this work, TiO 2 nanotube (NT) arrays were fabricated on commercially available pure titanium (Ti) surfaces by anodization and annealing. Then, zinc (Zn) and strontium (Sr), important for cell signaling, were doped on the NT surface by hydrothermal treatment. This very simple method of Zn and Sr doping takes less time and energy compared to other complicated techniques. Different surface characterization tools such as scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), energy-dispersive X-ray spectroscopy (EDS), static water contact angle, X-ray diffraction (XRD) and nanoindentation techniques were used to evaluate the modified surfaces. Then, adipose derived stem cells (ADSCs) were cultured with the surfaces to evaluate cell adhesion, proliferation, and growth on the surfaces. After that, the cells were differentiated towards osteogenic lineage to evaluate alkaline phosphatase (ALP) activity, osteocalcin expression, and calcium phosphate mineralization. Results indicate that NT surfaces doped with Zn and Sr had significantly enhanced ADSC adhesion, proliferation, growth, and osteogenic differentiation compared to an unmodified surface, thus confirming the enhanced performance of these surfaces.

Porous titanium exhibits low elastic modulus and porous structure is thought to be a promising implant in bone defect repair. However, the bioinert and low mechanical strength of porous titanium have limited its clinical application, especially in load-bearing bone defect repair. Our previous study has reported an infiltration casting and acid corrosion (IC-AC) method to fabricate a novel porous titanium (pTi) with 40% porosity and 0.4 mm pore diameter, which exerts mechanical property matching with cortical bone and interconnected channels. In this study, we introduced a nanoporous coating and incorporated an osteogenic element strontium (Sr) on the surface of porous titanium (named as Sr-micro arch oxidation [MAO]) to improve the osteogenic ability of the pTi by MAO. Better biocompatibility of Sr-MAO was verified by cell adhesion experiment and cell counting kit-8 (CCK-8) test. The in vitro osteogenic-related tests such as immunofluorescence staining, alkaline phosphatase staining and real-time polymerase chain reaction (RT-PCR) demonstrated better osteogenic ability of Sr-MAO. Femoral bone defect repair model was employed to evaluate the osseointegration of samples in vivo. Results of micro-CT scanning, sequential fluorochrome labeling and Van Gieson staining suggested that Sr-MAO showed better in vivo osteogenic ability than other groups. Taking results of both in vitro and in vivo experiment together, this study indicated the Sr-MAO porous titanium could be a promising implant load-bearing bone defect., (© 2024 Wiley Periodicals LLC.)

Phosphate bioactive glass has been studied for its advanced biodegradability and active ion release capability. Our previous research found that phosphate glass containing (P 2 O 5 )-(Na 2 O)-(TiO 2 )-(CaO)-(SrO) or (ZnO) showed good biocompatibility with MG63 and hMSCs. This study further investigated the application of 5 mol% zinc oxide or 17.5 mol% strontium oxide in titanium-doped phosphate glass for bone tissue engineering. Ti-Ca-Na-Phosphate glasses, incorporating 5% zinc oxide or 17.5% strontium oxide, were made with melting quenching technology. The pre-osteoblast cell line MC3T3-E1 was cultured for indirect contact tests with graded diluted phosphate glass extractions and for direct contact tests by seeding cells on glass disks. The cell viability and cytotoxicity were analysed in vitro over 7 days. In vivo studies utilized the tibial defect model with or without glass implants. The micro-CT analysis was performed after surgery and then at 2, 6, and 12 weeks. Extractions from both zinc and strontium phosphate glasses showed no negative impact on MC3T3-E1 cell viability. Notably, non-diluted Zn-Ti-Ca-Na-phosphate glass extracts significantly increased cell viability by 116.8% (P < 0.01). Furthermore, MC3T3-E1 cells cultured with phosphate glass disks exhibited no increase in LDH release compared with the control group. Micro-CT images revealed that, over 12 weeks, both zinc-doped and strontium-doped phosphate glasses demonstrated good bone incorporation and longevity compared to the no-implant control. Titanium-doped phosphate glasses containing 5 mol% zinc oxide, or 17.5 mol% strontium oxide have promising application potential for bone regeneration research., (© 2024. The Author(s).)

Infection and aseptic loosening caused by bacteria and poor osseointegration remain serious challenges for orthopedic implants. The advanced surface modification of implants is an effective strategy for addressing these challenges. This study presents a "pneumatic nanocannon" coating for titanium orthopedic implants to achieve on-demand release of antibacterial and sustained release of osteogenic agents. SrTiO 3 nanotubes (SrNT) were constructed on the surface of Ti implants as "cannon barrel," the "cannonball" (antibiotic) and "propellant" (NH 4 HCO 3 ) were codeposited into SrNT with assistance of mussel-inspired copolymerization of dopamine and subsequently sealed by a layer of polydopamine. The encapsulated NH 4 HCO 3 within the nanotubes could be thermally decomposed into gases under near-infrared irradiation, propelling the on-demand delivery of antibiotics. This coating demonstrated significant efficacy in eliminating typical pathogenic bacteria both in planktonic and biofilm forms. Additionally, this coating exhibited a continuous release of strontium ions, which significantly enhanced the osteogenic differentiation of preosteoblasts. In an implant-associated infection rat model, this coating demonstrated substantial antibacterial efficiency (>99%) and significant promotion of osseointegration, along with alleviated postoperative inflammation. This pneumatic nanocannon coating presents a promising approach to achieving on-demand infection inhibition and sustained osseointegration enhancement for titanium orthopedic implants.

Introduction: There is an ongoing need for improved healing response and expedited osseointegration on the Ti implants in acetabular fracture sites. To achieve adequate bonding and mechanical stability between the implant surface and the acetabular fracture, a new coating technology must be developed to promote bone integration and prevent bacterial growth., Methods: A cylindrical Ti substrate mounted on a rotating specimen holder was used to implant Ca 2+ , P 2+ , and Sr 2+ ions at energies of 100 KeV, 75 KeV and 180 KeV, respectively, using a low-energy accelerator to synthesize strontium-substituted hydroxyapatite at varying conditions. Ag 2+ ions of energy 100 KeV were subsequently implanted on the as-formed surface at the near-surface region to provide anti-bacterial properties to the as-formed specimen., Results: The properties of the as-formed ion-implanted specimen were compared with the SrHA-Ag synthesized specimens by cathodic deposition and low-temperature high-speed collision technique. The adhesion strength of the ion-implanted specimen was 43 ± 2.3 MPa, which is well above the ASTM standard for Ca-P coating on Ti. Live/dead cell analysis showed higher osteoblast activity on the ion-implanted specimen than the other two. Ag in the SrHA implanted Ti by ion implantation process showed superior antibacterial activity., Discussion: In the ion implantation technique, nano-topography patterned surfaces are not concealed after implantation, and their efficacy in interacting with the osteoblasts is retained. Although all three studies examined the antibacterial effects of Ag 2+ ions and the ability to promote bone tissue formation by MC3T3-E1 cells on SrHA-Ag/Ti surfaces, ion implantation techniques demonstrated superior ability. The synthesized specimen can be used as an effective implant in acetabular fracture sites based on their mechanical and biological properties., Competing Interests: The authors declare no conflicts of interest in this work., (© 2024 Swain et al.)

Surface modification is an important approach to improve osseointegration of the endosseous implants, however it is still desirable to develop a facile yet efficient coating strategy. Herein, a metal-phenolic network (MPN) is proposed as a multifunctional nanocoating on titanium (Ti) implants for enhanced osseointegration through early immunomodulation. With tannic acid (TA) and Sr 2+ self-assembled on Ti substrates, the MPN coatings provided a bioactive interface, which can facilitate the initial adhesion and recruitment of bone marrow mesenchymal stem cells (BMSCs) and polarize macrophage toward M2 phenotype. Furthermore, the TA-Sr coatings accelerated the osteogenic differentiation of BMSCs. In vivo evaluations further confirmed the enhanced osseointegration of TA-Sr modified implants via generating a favorable osteoimmune microenvironment. In general, these results suggest that TA-Sr MPN nanocoating is a promising strategy for achieving better and faster osseointegration of bone implants, which can be easily utilized in future clinical applications., (© 2024 The Authors. Advanced Science published by Wiley‐VCH GmbH.)

Antibacterial properties and osteogenic activity are considered as two crucial factors for the initial healing and long-term survivability of orthopedic implants. For decades, various drug-loaded implants to enhance biological activities have been investigated extensively. More importantly, to control the drug release timing is equally significant due to the sequential biological processes after implantation. Hence, developing a staged regulation system on the titanium surface is practically significant. Here, we prepared TiO 2 nanotubes (TiO 2 NTs) on the titanium surface by anodization, followed by the incorporation of zinc (Zn) and strontium (Sr) sequentially through a hydrothermal process. Surface characterization confirmed the successful fabrication of Zn and Sr-incorporated TiO 2 NTs (Zn-Sr/TiO 2 ) on the titanium surface. The ion release results exhibited the differential release characteristic of Zn and Sr, which meant the early-stage release of Zn and the long-term release of Sr. It was exactly in accord with  the biological process after implantation, laying the basis of staged regulation after implantation. Zn-Sr/TiO 2 showed favorable anti-early infection properties both in vitro and in vivo . Its inhibition effect on bacterial biofilm formation was attributed to the resistance against bacteria's initial adhesion and the killing effect on planktonic bacteria. Additionally, the release of Sr could alleviate infection-induced damage via immunoregulation. The biocompatibility and osteogenic activity mediated by M2 macrophage activation were confirmed with in vitro and in vivo studies. Therefore, it exhibited great potential in staged regulation for antibacterial activity in the early stage and the M2 activation-mediated osteogenic activity in the late stage. The staged regulation process was based on the differential release of Zn and Sr to achieve the early antibacterial effect and the long-term immune-induced osteogenic activity, to prevent implant-related infection and achieve better osseointegration. These two kinds of ions played their roles synergistically and complement mutually. This work is expected to provide an innovative idea for realizing sequential regulation after implantation.

The promotion of early osseointegration is crucial for the success of biomedical titanium implants. Physical and chemical modifications to the material surface can significantly compensate for the lack of biocompatibility and early osseointegration of the implant. In this study, we implanted strontium onto titanium plates and analyzed the effect of strontium-doped materials on angiogenesis and biocompatibility in the human bone structure. Our findings demonstrated that strontium-loaded titanium sheet materials effectively promote human umbilical vein endothelial cell (HUVEC) biocompatibility and vascular differentiation ability, as evidenced by proliferation-apoptosis assays, RT-qPCR for vascular neogenesis markers, ELISA for vascular endothelial growth factor (VEGF) levels, and nitric oxide (NO) analysis. Mechanism studies based on RNAseq and Western blotting analysis revealed that strontium can promote titanium material biocompatibility with HUVEC cells and vascular neovascularization ability by activating the extracellular signal-regulated kinase 1/2 (ERK1/2) signaling pathway. Meanwhile, blocking the ERK1/2 signaling pathway could reverse the promotional effect of vascular formation. Overall, we have successfully fabricated a multifunctional biocompatible bone implant with better histocompatibility and angiogenesis compared to uncoated implants., (© 2023. The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.)

Bone implantation inevitably causes damage to surrounding vasculature, resulting in a hypoxic microenvironment that hinders bone regeneration. Although titanium (Ti)-based devices are widely used as bone implants, their inherent bioinert surface leads to poor osteointegration. Herein, a strontium peroxide (SrO 2 )-decorated Ti implant, Ti&#95;P@SrO 2 , was constructed through coating with poly-L-lactic acid (PLLA) to alleviate the hypoxic microenvironment and transform the bioinert surface of the implant into a bioactive surface. PLLA degradation resulted in an acidic microenvironment and the release of SrO 2 nanoparticles. The acidic microenvironment then accelerated the decomposition of SrO 2 , resulting in the release of O 2 and Sr ions. O 2 released from Ti&#95;P@SrO 2 can alleviate the hypoxic microenvironment, thus enhancing cell proliferation in an O 2 -insufficient microenvironment. Furthermore, under hypoxic and normal microenvironments, Ti&#95;P@SrO 2 enhanced alkaline phosphatase activity and bone-related gene expression in C3H10T1/2 cells with the continuous release of Sr ions. Meanwhile, Ti&#95;P@SrO 2 suppressed M1 polarization and promoted M2 polarization of bone marrow-derived monocytes under hypoxic and normal conditions. Furthermore, in a rat implantation model, the implant enhanced new bone formation and improved osteointegration after modification with SrO 2 . In summary, the newly designed O 2 - and Sr ion-releasing Ti implants are promising for applications in bone defects., Competing Interests: Declaration of Competing Interest The authors declare no conflict of interest., (Copyright © 2024 Elsevier B.V. All rights reserved.)

The treatment of critical-sized bone defects has long been a major problem for surgeons. In this study, an intramedullary nail shaped three-dimensional (3D)-printed porous titanium implant that is capable of releasing strontium ions was developed through a simple and cost-effective surface modification technique. The feasibility of this implant as a stand-alone solution was evaluated using a rabbit's segmental diaphyseal as a defect model. The strontium-loaded implant exhibited a favorable environment for cell adhesion, and mechanical properties that were commensurate with those of a rabbit's cortical bone. Radiographic, biomechanical, and histological analyses revealed a significantly higher amount of bone ingrowth and superior bone-bonding strength in the strontium-loaded implant when compared to an untreated porous titanium implant. Furthermore, one-year histological observations revealed that the strontium-loaded implant preserved the native-like diaphyseal bone structure without failure. These findings suggest that strontium-releasing 3D-printed titanium implants have the clinical potential to induce the early and efficient repair of critical-sized, load-bearing bone defects., (© 2024 Wiley Periodicals LLC.)

The titanium alloy composition and microdesign affect the dynamic interplay between the bone cells and titanium surface in the osseointegration process. The current study aimed to evaluate the surface physicochemical properties, electrochemical stability, and the metabolic response of the MC3T3-E1 cells (pre-osteoblast cell line) cultured onto titanium-15molybdenum (Ti-15Mo) discs treated with phosphoric acid (H 3 PO 4 ) and sodium hydroxide (NaOH) and/or strontium-loading by the hydrothermal method. The x-ray dispersive energy spectroscopy (EDS) and x-ray diffraction (XRD) analysis showed no trace of impurities and the possible formation of hydrated strontium oxide (H 2 O 2 Sr), respectively. The confocal laser microscopy (CLSM) analysis indicated that titanium samples treated with strontium (Sr) showed greater surface roughness. The acid/alkali treatment prior to the hydrothermal Sr deposition improved the surface free energy and resistance to corrosion of the Ti-15Mo alloy. The acid/alkali treatment also provided greater retention of the Sr particles on the Ti-15Mo surfaces accordingly with inductively coupled plasma optical emission spectrometry (ICP-OES) analysis. The AlamarBlue and fluorescence analysis indicated noncytotoxic effects against the MC3T3-E1 cells, which allowed cells' adhesion and proliferation, with greater cells' spreading in the Sr-loaded Ti-15Mo samples. These findings suggest that Sr deposition by the hydrothermal method has the potential to enhance the physicochemical properties of the Ti-15Mo previously etched with H 3 PO 4 and NaOH, and also improve the initial events related to cell-mediated bone deposition., (© 2022 IOP Publishing Ltd.)

The present study aims to reveal the osteogenic roles played by DNA damage response biomarkers through implementing isobaric tags for relative and absolute quantitation (iTRAQ) technique. First, sandblasted large-grit double acid-etched (SLA) titanium implant and strontium-incorporated (SLA-Sr) titanium implant were used for inserting in the tibiae of rats. iTRAQ technique was used to detect protein expression changes and identify differentially expressed proteins (DEPs). In total, 19,343 peptides and 4280 proteins were screened out. Among them, 91 and 138 DEPs were identified in the SLA-Sr group after implantation for 3 and 7 days, respectively. Ataxia-telangiectasia mutated (ATM) protein up-regulated on the 3rd day showed a trend of further up-regulation on the 7th day. Moreover, functional enrichment analyses were also conducted to explore the biological function of DEPs during the initial stage of osseointegration in vivo, which revealed that the biological functions of the DEPs on the 7th day were mainly related to "mismatch repair" and "mitotic G1 DNA damage checkpoint." Analysis of the Reactome signaling pathway showed that ATM was associated with TP53's regulation and activation. Finally, DNA damage repair related genes were selected for validation at mRNA and protein expression levels. Real-time reverse transcription-polymerase chain reaction and immunohistochemistry validation results demonstrated that mRNA expression level of ATM was higher in SLA-Sr group. In conclusion, SLA-Sr titanium implant could initiate DNA damage repair by activating expression levels of ATM. This study was striving to reveal new faces of better osseointegration and shedding light on the biological function and underlying mechanisms of this important procedure., (© 2021 Wiley Periodicals LLC.)

One of the major challenges for Ti-based implants is insufficient osteointegration, which might result in the loosening of the implant. In this study, we fabricated strontium (Sr)-containing barium titanate (BST) on the surface of Ti to improve the bioactivity for osteointegration enhancement. The introduction of Sr significantly reduced the crystallization time and improved crystallinity, which was proved by X-ray diffraction, X-ray photoelectron spectroscopy, and transmission electron microscopy. Compared with Ti, the BST film showed greater wettability surface and lower elastic modulus and hardness. Furthermore, in synergy with the release of Sr ions, the BST film improved early adhesion and followed osteogenic differentiation of rat bone mesenchymal stem cells. Furthermore, the bone implantation experiment suggested that the BST film could significantly improve the in vivo osteogenesis and osteointegration capabilities of Ti implants. In summary, this study revealed that BST-modified Ti has potential application in bone repair.

Implant-associated infections (IAI) remains a common and devastating complication in orthopedic surgery. To reduce the incidence of IAI, implants with intrinsic antibacterial activity have been proposed. The surface functionalization and structure optimization of metallic implants can be achieved by surface modification using the phosphate chemical conversion (PCC) technique. Zinc (Zn) has strong antibacterial behavior toward a broad-spectrum of bacteria. Herein, Zn was incorporated into strontium-calcium-phosphate (SrCaP) coatings on titanium (Ti) via PCC method, and the influence of its doping amount on the phase, microstructure, antibacterial activity, and biocompatibility of the composite coating was researched. The results indicated that traces of Zn doping produced grain refinement of SrCaP coating with no significant effect on its phase and surface properties, while a higher Zn content induced its phase and microstructure transformed into zinc-strontium-phosphate (SrZn 2 (PO 4 ) 2 ). SrCaP-Zn1 and SrCaP-Zn4 represented trace and high content Zn-doped coatings, respectively, which exhibited a similar bacterial attachment for a short time but showed inhibition of biofilm formation after continuous incubation up to 24 h. The killing rates of SrCaP-Zn1 coating for Staphylococcus aureus ( S. aureus ) and Escherichia coli ( E. coli ) reached 61.25% and 55.38%, respectively. While that data increased to 83.01% and 71.28% on SrCaP-Zn4 coating due to the more-releasing Zn 2+ . Furthermore, in vitro culture of MC3T3-E1 cells proved that the Zn-doped coatings also possessed excellent biocompatibility. This study provides a new perception for the phase and microstructural optimization of phosphate coatings on implant surfaces, as well as fabricating promising coatings with excellent biocompatibility and antimicrobial properties against IAI.

Bacterial infection and poor osteogenic capacity can result in the loosing or failure of titanium (Ti)-based implants in the clinic. Therefore, it is urgent to design an effective approach to enhance the osteogenic property and restrict bacterial activity. In this study, a layered double hydroxide (LDH) composed of Ga and Sr ions on Ti substrates by a hydrothermal method, then calcined in 250°C and denoted as LDH250. The scanning electron microscopy (SEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) were confirmed that the LDH films were successfully formed on the Ti substrates. Importantly, the obtained LDH films can induce an alkaline microenvironment around the Ti surface and regulate the behaviors of osteogenic cells and bacteria. In vitro cellular experiments, the LDH250 can enhance the differentiation of both MC3T3-E1 cells and osteoblasts, stimulate alkaline phosphatase activity (ALP), collagen secretion, and mineralization levels. Meanwhile, antimicrobial assay against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) demonstrated that the LDH250 samples had strong antibacterial abilities, which attributed to the release profile of Ga 3+ could act as a "Trojan horse" to destroy the bacterial iron metabolism, inducing of local alkaline environment, and producing reactive oxygen species. Hence, this study provides an effective method for reducing antibacterial infection and enhancing the bone integrative capacity of Ti-based implants for orthopedic applications., (© 2021 Wiley Periodicals LLC.)

Early osteointegration is essential for biomedical implants. Surface modifications can significantly compensate for an implant's lack of biocompatibility and osteo-differentiation. They can also be designed to promote angiogenesis in order to assist osteogenesis and ultimately facilitate bone regeneration. In this study, a polydopamine-assisted strontium-substituted apatite coating (Ti@PDA + SrHA) was fabricated on a multifunctional titanium implant to induce both angiogenic and osteogenic abilities for rapid osseointegration. Polydopamine and Sr-substituted hydroxyapatite were coated on the implant through biomineralization. The in vitro results showed that Ti@PDA + SrHA improved cell adhesion and increased the proliferation of rat bone marrow-derived mesenchymal stem cells (rBMSCs) and human umbilical vein endothelial cells (HUVECs). Ti@PDA + SrHA upregulated the expression of ALP activity and osteogenic genes in rBMSCs and elevated angiogenic genes in both rBMSCs and HUVECs. Mechanically, the FAK/MAPK signaling pathway was activated in rBMSCs, and the PI3K/AKT signaling pathway was activated in both rBMSCs and HUVECs. Consistent with these findings, Ti@PDA + SrHA accelerated new bone formation and rapid osseointegration in the femoral condyle implantation study with good stability. Overall, we fabricated a multifunctional biocompatible implant with better angiogenic and osteogenic performance compared to the non-coated implant., (Copyright © 2021. Published by Elsevier B.V.)

To mimic the electrical properties of natural bone, controlled strontium substitution of both hydroxyapatite and ferroelectric barium titanate were achieved by mixing in the ratio 30:70 by weight. The composites were characterized by X-ray diffraction, Fourier transform infrared spectroscopy and scanning electron microscopy to investigate the phase composition and microstructure of the composites. Unpolarized and polarized strontium hydroxyapatite (SrHA)-barium strontium titanate (BST) composites with controlled degree of Sr substitution were examined, including 5SrHA-5BST (5% Sr substitution in both components) and 10SrHA-10BST composites. The 10SrHA-10BST composite showed a higher osteoblast activity, as observed from the cell viability studies performed using CCK-8 assay. The polarized composites showed promise against Staphylococcus aureus bacteria by minimizing the adhesion and growth of bacteria, as compared with their unpolarized counterparts. The polarized 10SrHA-10BST was found to be superior than all other composites. As a result, the approach of polarization of SrHA-BST composites has been found to be an effective bone substitute material in controlled enhancement of osteoblast growth with simultaneous reduction of bacterial infection., (© 2021 Wiley Periodicals LLC.)

To improve in vivo osseointegration of pure titanium implant, Sr-Ga clavate double hydroxide (CDH) coating was grown in situ on a titanium (Ti) substrate with simple hydrothermal and calcination treatments at 500 °C. The obtained coating on the Ti substrate (Ti-CDH and Ti-CDH500) was researched by scanning electron microscopy (SEM), X-ray diffraction (XRD), and energy dispersive spectroscopy (EDS). Ti-CDH exhibited a sustained release profile of metal ions and maintained a slightly alkaline environment. The CDH coating was beneficial for osteogenic differentiation of mesenchymal stem cells (MSCs), which were reflected by the results of cellular assays, including alkaline phosphatase activity (ALP), cell mineralization capability (ARS), and osteogenesis-related gene expression. Besides, Ti-CDH could effectively improve the autophagic levels in MSCs, which further promoted osteogenic differentiation of MSCs. Hence, the Ti surface with Sr-Ga CDH modification supplied a simple and effective strategy to design biomaterials for bone generation.

Titanium (Ti) and Ti alloys are widely used biomaterials, but they lack osteogenic capability for rapid bone integration. To improve osseointegration of Ti implants, TiO 2 nanotubes were prepared using the anodizing oxidation technique, and strontium (Sr) combined with icariin (ICA) was loaded on TiO 2 nanotube coatings. Cell adhesion and proliferation of MC3T3-E1 cells, alkaline phosphatase (ALP) activity, mineralization of extracellular matrix, and bone formation around titanium implants in ovariectomized rats, were examined separately. The results showed that compared with pure Ti, TiO 2 and Sr-loaded TiO 2 coatings, the coatings loaded with both Sr and ICA showed better effect on cell adhesion and proliferation, higher ALP activity and more red-stained mineralized nodules. Furthermore, more bone was formed around implants loaded with both Sr and ICA in osteoporotic rats. Therefore, coating with Sr and ICA is valuable for clinical application to strengthen the osseointegration of titanium implants, especially in osteoporotic patients.

Ti and Ti alloys are bioinert materials and two frequent problems associated with them are bacterial infection and lack of osteogenic potential for rapid bone integration. To overcome the problems, the present study incorporated strontium (Sr) and silver (Ag) simultaneously into porous TiO 2 coatings through a single-step technique, micro-arc oxidation (MAO). Incorporation of Sr and Ag brought no significant changes to coating micromorphology and physicochemical properties, but endowed TiO 2 coatings with both strong antibacterial activity and osteogenic ability. Antibacterial activity increased with Ag contents in the coatings. When Ag content reached 0.58 wt%, the coating showed both excellent short-term (100.0%) and long-term (77.6%) antibacterial activities. Sr/Ag-containing coatings with 18.23 wt% Sr and 0.58 wt% Ag also presented good cytocompatibility for preosteoblast adhesion and proliferation, and promoted preosteoblast osteogenic differentiation both short-termly and long-termly. However, higher Ag content (1.29 wt%) showed toxic effects to preosteoblasts. In summary, MAO is a simple and effective way to incorporate Sr and Ag into porous TiO 2 coatings and Sr/Ag-containing TiO 2 coating with 18.5 wt% Sr and 0.58 wt% Ag has both good osteogenic activity and strong antibacterial capability short-termly and long-termly. Therefore, such coatings are valuable for clinical application to strengthen osseointegration and long-term high quality use of titanum implants., (© 2020 Wiley Periodicals LLC.)

To overcome problems associated with loosening of orthopedic implants and surgical site infections, we developed a novel, titanium (Ti)-based material that releases both strontium and silver ions (CaSrAg-Ti) based on alkali-and-heat treatment. The results of commercially pure Ti (cp-Ti), Ti that releases Sr ions only (CaSr-Ti), and the novel CaSrAg-Ti material were compared. Mechanical tests were performed to evaluate the in vivo bonding properties of CaSrAg-Ti and the bone-implant contact (BIC) ratio in histological specimens was determined at 4 and 8 weeks after implantation in a rat femur. Also, the in vitro antibacterial activities of this material against methicillin-susceptible Staphylococcus aureus (MSSA) were evaluated after a 24 h incubation period by assaying colony-forming units. In addition, antibacterial activities were evaluated in vivo at 7 days after implantation in a rat subcutaneous pocket model. There was direct contact between the bone and CaSrAg-Ti in histological specimens and no apparent signs of argyrosis in any rat. The bone-bonding strength and the BIC ratio were increased by 2.7- and 2.3-fold for CaSrAg-Ti vs. cp-Ti at 4 weeks and 2.2- and 2.0-fold at 8 weeks, respectively. As compared with cp-Ti, the number of viable MSSA remaining on CaSrAg-Ti was reduced by 100 ± 0% in vitro and 94.2 ± 6.9% in vivo. Ti that releases Sr and Ag ions is a promising material that exhibits both bone-bonding properties and anti-MSSA activities., (© 2020 Wiley Periodicals LLC.)

Peri-prosthetic infection and loosening of implants are major problems in orthopaedic and dental surgery. To address these issues, surface treatment methods for titanium implants have been improved by modifying the alkali and heat treatment. We have previously fabricated calcium-treated Ti metal that releases Sr ions (CaSr-Ti), which resulted in a higher in vitro osteogenic response and early in vivo bone bonding.Further, we developed a Ti metal that released both Sr and Ag ions (CaSrAg-Ti). In this study, we evaluated the antibacterial ability and osteogenic cellular response of CaSrAg-Ti and CaSr-Ti in vitro using rat bone marrow stromal cells (BMSCs) cultured on implant samples and extract mediums (EMs) made by immersing the implant samples in the medium. CaSrAg-Ti did not show cytotoxicity and was associated with a slightly higher osteogenic response when compared to CaSr-Ti, without inhibiting the effect of Sr. The osteogenic response was also observed in the cells cultured with the CaSrAg-Ti EM; however, the response was not as high as that of the cells on the CaSrAg-Ti implant sample. Significantly higher antibacterial activity was observed along with an antibacterial efficacy of more than 95% against methicillin-susceptible Staphylococcus aureus and Escherichia coli . The main advantages of our surface treatment are its simplicity and low cost. Therefore, our treatment is promising for clinical applications in orthopaedic or dental Ti-based implants with antibacterial and early bone-bonding abilities.

Titanium (Ti) and its alloys are believed to be promising scaffold materials for dental and orthopedic implantation due to their ideal mechanical properties and biocompatibility. However, the host immune response always causes implant failures in the clinic. Surface modification of the Ti scaffold is an important factor in this process and has been widely studied to regulate the host immune response and to further promote bone regeneration. In this study, a calcium-strontium-zinc-phosphate (CSZP) coating was fabricated on a Ti implant surface by phosphate chemical conversion (PCC) technique, which modified the surface topography and element constituents. Here, we envisioned an accurate immunomodulation strategy via delivery of interleukin (IL)-4 to promote CSZP-mediated bone regeneration. IL-4 (0 and 40 ng/mL) was used to regulate immune response of macrophages. The mechanical properties, biocompatibility, osteogenesis, and anti-inflammatory properties were evaluated. The results showed that the CSZP coating exhibited a significant enhancement in surface roughness and hydrophilicity, but no obvious changes in proliferation or apoptosis of bone marrow mesenchymal stem cells (BMMSCs) and macrophages. In vitro, the mRNA and protein expression of osteogenic related factors in BMMSCs cultured on a CSZP coating, such as ALP and OCN, were significantly higher than those on bare Ti. In vivo, there was no enhanced bone formation but increased macrophage type 1 (M1) polarization on the CSZP coating. IL-4 could induce M2 polarization and promote osteogenesis of BMMSCs on CSZP in vivo and in vitro. In conclusion, the CSZP coating is an effective scaffold for BMMSCs osteogenesis, and IL-4 presents the additional advantage of modulating the immune response for bone regeneration on the CSZP coating in vivo., (Copyright © 2020 Elsevier B.V. All rights reserved.)

To develop implants with improved bone ingrowth, titanium substrates were coated with homogeneous and dense struvite (MgNH4PO4·6H2O) layers by means of electrochemically assisted deposition. Strontium nitrate was added to the coating electrolyte in various concentrations, in order to fabricate Sr-doped struvite coatings with Sr loading ranging from 10.6 to 115 μg/cm2. It was expected and observed that osteoclast activity surrounding the implant was inhibited. The cytocompatibility of the coatings and the effect of Sr-ions in different concentrations on osteoclast formation were analyzed in vitro. Osteoclast differentiation was elucidated on morphological, biochemical as well as on gene expression level. It could be shown that moderate concentrations of Sr2+ had an inhibitory effect on osteoclast formation, while the growth of osteoblastic cells was not negatively influenced compared to pure struvite surfaces. In summary, the electrochemically deposited Sr-doped struvite coatings are a promising approach to improve bone implant ingrowth.

Early vascularization plays an important role in bone healing, especially in interfacial bone formation. Many modifications have been made to titanium surfaces to promote angiogenesis. In addition, cytokines secreted by osteoblasts have been reported to enhance early angiogenesis, however, the effect is limited because osteoblasts arise after inflammation subsides. We fabricated a newly sustained release system consisting of Sr ion-loaded sodium titanate nanorods (STSr) and studied its effect on angiogenesis by regulating macrophage subtypes. In an in vitro study, STSr significantly promoted the angiogenesis and formation of CD31 hi Emcn hi vessels by modulating the transformation of M1 macrophages toward M2 macrophages. After incubation on STSr surfaces, macrophages (RAW264.7) polarized toward M2 subtypes and expressed high levels of PDGF-BB. Furthermore, the conditioned medium from RAW264.7 cells enhanced the ability of tubule formation and migration of HUVECs and their differentiation into pro-osteogenesis vessels (CD31 hi Emcn hi vessels). In vivo studies showed high expression levels of CD31 hi Emcn hi surrounding implants. Accompanied with enhanced vascularization, improved bone formation and osseointegration were observed. Our study serves as a basis for the clinical application of novel functional topography surfaces fabricated on titanium, which can be applied in new orthopedic implants for the better prognosis of patients.

The inherent biological inertness of Ti substrates is a general challenge in orthopedic and dental clinical application. In this study, the strontium-containing phase change lysozyme coating was prepared on titanium via a supramolecular self-assembly method for accelerating osseointegration. Successful preparation of the Sr-incorporated lysozyme nanofilm onto the Ti substrate (Ti-Ly-Sr) was proved by tests of scanning electron microscopy (SEM), atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS) and Contact angle (CA). Furthermore, the results of cell morphology observation, cell viability assay, alkaline phosphatase staining and quantitative analysis showed that Ti-Ly-Sr substrate enhanced early adhesion, proliferation and osteogenic differentiation of bone marrow stromal cells (BMSCs). The quantitative real-time polymerase chain reaction (qRT-PCR) assays confirmed that Ti-Ly-Sr enhanced the expression of osteogenic related genes (BMP2, OPG, Runx2 and COL-1) of BMSCs at the molecular level. Moreover, Micro-CT and histological analysis proved that the strontium-incorporated lysozyme nanofilm modified Ti implants had significant capability of new bone formation in vivo after implantation for 4 weeks. We anticipate that the present system would provide a facile and effective means for surface modification of Ti-based implants. Relevant ideas and techniques in this study will contribute to the development of new implant devices., Competing Interests: Declaration of competing interest The authors declare that there is no conflict of interests regarding the publication of this paper., (Copyright © 2020 Elsevier B.V. All rights reserved.)

Selective laser melting (SLM) titanium alloys require surface modification to achieve early bone-bonding. This study investigated the effects of solution and heat treatment to induce the sustained release of strontium (Sr) ions from SLM Ti6Al4V implants (Sr-S64). The results were compared with a control group comprising an untreated surface [SLM pure titanium (STi) and SLM Ti6Al4V (S64)] and a treated surface to induce the release of calcium (Ca) ions from SLM Ti6Al4V (Ca-S64). The surface-treated materials showed homogenous nanoscale network formation on the original micro-topographical surface and formed bone-like apatite on the surface in a simulated body fluid within 3 days. In vitro evaluation using MC3T3-E1 cells showed that the cells were viable on Sr-S64 surface, and Sr-S64 enhanced cell adhesion-related and osteogenic differentiation-related genes expression. In vivo rabbit tibia model, Sr-S64 provided significantly greater bone-bonding strength and bone-implant contact area than those in controls (STi and S64) in the early phase (2-4 weeks) after implantation; however, there was no statistical difference between Ca-S64 and controls. In conclusion, Sr solution and heat treatment was a safe and effective method to enhance early bone-bonding ability of S-64 by improving the surface characteristics and sustained delivery for Sr., Competing Interests: Declaration of competing interest None., (Copyright © 2019 Elsevier B.V. All rights reserved.)

Surface chemistry and topography can determinatively affect the osseointegration of dental implants. Strontium (Sr) has a significant effect on the promotion of bone formation and inhibitation of bone resorption. The emphasis of this study lies on the evaluation of a new surface treatment that aims to improve the early osseointegration of dental implantation both in vitro and in vivo. A hydrothermal method was used to prepare an SrTiO 3 incorporation on sandblasted large-grit double acid-etched (SLA) titanium surfaces in SrCl 2 solution. The composition and morphology of the SrTiO 3 doped surface were analyzed by X-ray diffraction, X-ray photoelectron spectroscopy，and scanning electron microscopy. In addition, the external release figure of Sr was examined by inductively coupled plasma mass spectrometry. The proliferation, adhesion and differentiation of MC3T3-E1 cells on this surface were evaluated in vitro and presented a significant increase in SLA-Sr group compared with that in SLA group. An in vivo study in 24 New Zealand rabbits indicated a remarkable growth in the volume of direct bone-to-implant contact and peri-implant bone in SLA-Sr group, which were compared with SLA group after 3 and 6 weeks, and removal torque tests exhibited a higher torque removal value of SLA-Sr implants. The study gave the result that the biological effect of SLA-Sr implants was significantly superior to that of the SLA implants at the early stage of osseointegration., (Copyright © 2019 Elsevier B.V. All rights reserved.)

The two major causes for implant failure are postoperative infection and poor osteogenesis. Initial period of osteointegration is regulated by immunocytes and osteogenic-related cells resulting in inflammatory response and tissue healing. The healing phase can be influenced by various environmental factors and biological cascade effect. To synthetically orchestrate bone-promoting factors on biomaterial surface, built is a dual delivery system coated on a titanium surface (abbreviated as AH-Sr-AgNPs). The results show that this programmed delivery system can release Ag + and Sr 2+ in a temporal-spatial manner to clear pathogens and activate preosteoblast differentiation partially through manipulating the polarization of macrophages. Both in vitro and in vivo assays show that AH-Sr-AgNPs-modified surface renders a microenvironment adverse for bacterial survival and favorable for macrophage polarization (M2), which further promotes the differentiation of preosteoblasts. Infected New Zealand rabbit femoral metaphysis defect model is used to confirm the osteogenic property of AH-Sr-AgNPs implants through micro-CT, histological, and histomorphometric analyses. These findings demonstrate that the programmed surface with dual delivery of Sr 2+ and Ag + has the potential of achieving an enhanced osteogenic outcome through favorable immunoregulation., (© 2019 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

BACKGROUND To fabricate strontium (Sr)-incorporated titanium (Ti) surfaces by a novel 1-step phase-transited lysozyme (PTL) treatment, and investigate the effects of the prepared samples on osteogenesis and osteoimmunoregulation. MATERIAL AND METHODS Five groups of titanium specimens were prepared, including Ti, PTL, PTL@10Sr (PTL coating with 10 mg/mL Sr), PTL@20Sr PTL coating with 20 mg/mL Sr), and PTL@50Sr (PTL coating with 50 mg/mL Sr) groups. Behaviors of bone marrow mesenchymal stem cells (BMSCs) such as initial attachment, spread, proliferation, and migration, on different surfaces were examined by immunofluorescence, MTS assay, and Transwell system. Then the osteogenic differentiation of BMSCs was detected. When an immune response was factored in, the polarization of macrophages induced by the prepared surfaces was detected by real-time PCR, and the response of BMSCs to macrophage-conditioned medium was assessed in terms of cell migration and osteogenic differentiation. Finally, an in vivo study was performed, using the rat femora implant model, to evaluate the potential for osteogenic induction and osteoimmunoregulation of materials. RESULTS Our in vitro experiments indicated that PTL coating could improve cell spread and adhesion, and the stable Sr release of PTL@Sr layers could promote cell migration and osteogenesis. Moreover, PTL@Sr surface could regulate the immune response of macrophages resulting in enhanced BMSCs recruitment and osteogenic differentiation. The in vivo evaluation showed less inflammatory infiltration and improved bone formation in the PTL@20Sr group. CONCLUSIONS The Sr-loaded PTL layers have greater potential for the induction of osteogenic differentiation of BMSCs, meanwhile Sr-loaded PTL layers could adjust the immune response and thus promote osteogenesis both in vitro and in vivo.

Fabrication of titanium (Ti)-based biomedical implants with appropriate topography as well as capacity for drug delivery is highly pursued in the field of orthopedic and dental implants. In this study, a biomimetic mesoporous coating imbedded with strontium (MPs-Sr) is prepared by the high current anodization (HCA) and hydrothermal treatment (HT). This coating provides a more stable mechanical performance than the conventional nanotube arrays. The Sr loading is regulated by the HT reaction time and the Sr is released in a controllable manner from the MPs-Sr surface. The hydrophilic performance of MPs-Sr are significantly improved. Furthermore, it is showed that the attachment and spreading of preosteoblast MC3T3-E1 cells are significantly up-regulated by the nanoscale topology of MPs and the doped Sr. The improved collagen secretion and matrix mineralization levels of cells are closely related with the Sr release. The excellent osteogenic properties of MPs-Sr samples highlight their promising potential for use in clinical application., (Copyright © 2018 Elsevier B.V. All rights reserved.)

The microstructure of hydroxyapatite is known to influence cellular behavior, can be used as a substrate for osteoblast growth, and exploited as a drug-release platform. However, easy delamination and self-decomposition of hydroxyapatite caused by poor adhesion with substrates are the main problems currently. In this paper, we successfully fabricated titanium dioxide/strontium-doped hydroxyapatite (TiO 2 /SrHA) composite scaffolds by self-generated strontium-substituted hydroxyapatite microspheres in TiO 2 nanotubes. Moreover, the active compound 1-(5-bromo-2-hydroxy-methoxyphenyl)-ethanone (BHM) from Seahorse ( Hippocampus kuda Bleeler) was loaded in this scaffold, and the controlled release kinetics of BHM was studied. It was found that in the first 5 h, the release concentration and time of BHM had a good linear relationship, and the correlation coefficient reached 0.98. TiO 2 /SrHA/BHM composites exhibited favorable cytocompatibility at a given concentration of BHM (20 μmol/L). Compared to pure SrHA, TiO 2 nanotubes, and traditional TiO 2 /SrHA composites, superior cytocompatibility (cell adhesion and proliferation) of MC3T3-E1 was obtained on TiO 2 /SrHA/BHM composites. The expression levels of osteogenic marker genes such as alkaline phosphatase, osteopontin, osteocalcin, runt-related transcription factor 2, and collagen I are also upregulated to varying degrees. This TiO 2 /SrHA composite scaffold-mediated phenolic compound BHM could be applied in bone tissue repair.

Recruitment of endogenous bone marrow-derived mesenchymal stem cells (BMSCs) has been widely discussed as an alternative strategy for bone regeneration. Strontium (Sr) is known to direct the BMSCs' commitment to the bone lineage and encourage bone formation; however, the underlying mechanisms remain elusive. In this study, an Sr-incorporated micro/nano rough titanium surface (MNT-Sr) was fabricated by hydrothermal treatment in an attempt to facilitate BMSCs' recruitment and their osteogenic differentiation to enhance rapid osseointegration. Micro rough titanium (MT) was set as the control biomaterial. In vitro, MNT-Sr and its extracts promoted the migration and osteogenic differentiation of BMSCs. In animal studies, green fluorescent protein (GFP)-labeled BMSCs were intravenously injected into wild-type rats for tracing before tibial implantation surgery. The GFP+BMSC recruitment to the implantation site was successfully triggered by MNT-Sr implantation. A trend for increased bone area (BA%), bone-implant contact (BIC%) and removal torque values (RTVs) was observed for the MNT-Sr implant compared to that observed for MT at 2 weeks. Advanced mechanism analysis indicated that Sr2+ enhanced the SDF-1α/CXCR4 signaling pathway both in vitro and in vivo. Taken together, these findings suggest that MNT-Sr has promising therapeutic potential for future use in dental implants by homing endogenous stem cells to stimulate bone regeneration.

Commercially pure Titanium (Cp-Ti) was electrophoretically modified using double layer coatings consisting of TiO 2 -SrHAP as the first layer (TH) followed by vancomycin incorporated Chitosan/Gelatin as the second layer (THV). The nano crystalline phase of coated Strontium incorporated hydroxyapatite (Sr-HAP) confirmed through X-ray diffraction studies (XRD). The polyelectrolyte complex formation between chitosan and gelatin, the stability of the drug, the bonding between chitosan and Sr-HAP were confirmed through infra-red spectroscopic studies (IR). The average roughness (R a ) value calculated from atomic force microscopy (AFM) corroborates with the water contact angle data, which clearly confirms the tuning property of the surface in relation to the surface energy and roughness of the coated samples. The total amount of vancomycin encapsulated was calculated to be 11.5 μg. Antibacterial activity was found against both Staphylococcus aureus strains methicillin resistant Staphylococcus aureus (MRSA) and methicillin sensitive Staphylococcus aureus (MRSA) for a drug concentration of 2.74 μg released after 12 h of immersion. The in-vitro cell culture studies showed enhanced cellular activity for THV samples. Thus, THV samples have a dual action at the surface, by resisting the bacterial adhesion and enhancing cellular interaction at the bio-interface, making it a promising candidate to treat osteomyelitis infection., (Copyright © 2018. Published by Elsevier B.V.)

We have previously developed the "alkali and heat treatment" method to confer bioactivity (bone-bonding ability) to titanium metal (Ti). As strontium (Sr) and magnesium (Mg) ions reportedly promote osteoblastic cell proliferation and differentiation and accelerate bone formation, we improved this method to induce the release of Sr (Sr-Ti) or Mg (Mg-Ti) ions from Ti in a previous study. Here, we evaluated the bioactivity of these novel surface treatments, Sr-Ti and Mg-Ti. In vitro evaluation of cell viability, expression of integrin β1, β catenin, and cyclin D1, osteogenic gene expression, alkaline phosphatase activity, and extracellular mineralization using MC3T3-E1 cells revealed that Sr-Ti and Mg-Ti enhanced proliferation and osteogenic differentiation. In rabbit in vivo studies, Sr-Ti and Mg-Ti also provided greater biomechanical strength and bone-implant contact than the positive control Ti (Ca-Ti), especially at the early stage (4-8weeks), and maintained these properties for a longer period (16-24weeks). Advantages of the improved method include process simplicity, applicability for any implant shape, and lack of adverse effects on implant composition and structure. Therefore, our treatment is promising for clinical applications to achieve early bone bonding., Statement of Significance: Implantation into osteoporotic bone constitutes a challenging problem because of early migration or loosening of the implant, which is primarily due to insufficient initial fixation in porotic bone. Therefore, it is desirable to provide implants with a capacity for early bone bonding. We have achieved conferring early bone bonding ability to titanium metal by releasing strontium ions or magnesium ions. Our treatment is promising for clinical applications to achieve early bone bonding of orthopedic or dental Ti-based implants., (Copyright © 2017 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.)

Implant-related infection in primary total joint prostheses has attracted considerable research attention. As a measure to improve the antimicrobial properties of implant materials, silver (Ag) was incorporated into calcium phosphate (CaP) coatings on Titanium (Ti) via a hydrothermal method. Further, strontium (Sr) was added as a binary dopant to reduce the cytotoxicity of Ag in the coatings. Results showed that the CaP coatings were uniformly deposited on Ti with enhanced hydrophilicity and nanoscale surface roughness. Moreover, cell adhesion, proliferation, and differentiation were improved after the CaP coating deposition. The antibacterial properties of the coatings were distinctly improved by the incorporation of Ag, but the cell proliferation and differentiation were significantly decreased. Owing to the incorporation of Sr, the Ag-CaP coatings were able to effectively counteract the negative effects of Ag while maintaining good antibacterial properties. In summary, hydrothermally deposited CaP coatings doped with Ag and Sr exhibit excellent biocompatibility and antimicrobial activity. Thus, such co-doped CaP coatings have considerable potential for orthopaedic implant modification., (Copyright © 2016 Elsevier B.V. All rights reserved.)

A new approach is provided for preparing radiopaque and angiogenic poly(propylene fumarate) (PPF) bone cements by integrating Sr-doped n-TiO 2 nanowires and ginsenoside Rg1 suitable for treating osteonecrosis. High aspect ratio radiopaque TiO 2 -nanowires are synthesized by strontium doping in supercritical CO 2 for the first time, showing a new phase, SrTiO 3 . PPF is synthesized using a transesterification method by reacting diethyl fumarate and propylene glycol, then functionalized using maleic anhydride to produce terminal carboxyl groups, which are subsequently linked to the nanowires. The strong interfacial adhesion between functionalized PPF and nanowires is examined by scanning electron microscopy, Fourier transform infrared, X-ray photoelectron spectroscopy, thermal analysis, and mechanical testing. An angiogenic modulator, ginsenoside Rg 1 , is integrated into the bone cement formulation with the mechanical properties, radiopacity, drug release, and angiogenesis behavior of the formed composites explored. The results show superior radiopacity and excellent release of ginsenoside Rg 1 in vitro, as well as a dose-dependent increase in the branching point numbers. The present study suggests this new methodology provides sufficient mechanical properties, radiopacity, and angiogenic activity to be suitable for cementation of necrotic bone., (© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Wear-particle-induced chronic inflammation and osteoclastogenesis have been identified as critical factors of aseptic loosening. Although strontium is known to be involved in osteoclast differentiation, its effect on particle-induced inflammatory osteolysis remains unclear. In this study, we investigate the potential impact and underling mechanism of strontium on particle-induced osteoclast activation and chronic inflammation in vivo and in vitro. As expected, strontium significantly inhibited titanium particle-induced inflammatory infiltration and prevented bone loss in a murine calvarial osteolysis model. Interestingly, the number of mature osteoclasts decreased after treatment with strontium in vivo, suggesting osteoclast formation might be inhibited by strontium. Additionally, low receptor activator of nuclear factor-κB ligand (RANKL), tumor necrosis factor-α, interleukin-1β, interleukin-6 and p65 immunochemistry staining were observed in strontium-treatment groups. In vitro, strontium obviously decreased osteoclast formation, osteoclastogenesis-related gene expression, osteoclastic bone resorption and pro-inflammatory cytokine expression in bone-marrow-derived macrophages in a dose-dependent manner. Furthermore, we demonstrated that strontium impaired osteoclastogenesis by blocking RANKL-induced activation of NF-κB pathway. In conclusion, our study demonstrated that strontium can significantly inhibit particle-induced osteoclast activation and inflammatory bone loss by disturbing the NF-κB pathway, and is an effective therapeutic agent for the treatment of wear particle-induced aseptic loosening.

Since strontium (Sr) is known for its anabolic and anticatabolic effect on bone, research has been focused on its potential impact on osseointegration. The objective of this study was to investigate the performance of nanotopographic implants with a Sr-functionalized titanium (Ti) coating (Ti-Sr-O) with respect to osseointegration in osteoporotic bone. The trial was designed to examine the effect of sustained-release characteristics of Sr in poor-quality bone. Three Ti-Sr-O groups, which differed from each other in coating thickness, Sr contents, and Sr release, were examined. These were prepared by a magnetron sputtering process and compared to uncoated grade 4 Ti. Composition, morphology, and mechanical stability of the coatings were analyzed, and Sr release data were gained from in vitro washout experiments. In vivo investigation was carried out in an osteoporotic rat model and analyzed histologically, 6 weeks and 12 weeks after implantation. Median values of bone-to-implant contact and new bone formation after 6 weeks were found to be 84.7% and 54.9% (best performing Sr group) as compared to 65.2% and 23.8% (grade 4 Ti reference), respectively. The 12-week observation period revealed 84.3% and 56.5% (best performing Sr group) and 81.3% and 39.4% (grade 4 Ti reference), respectively, for the same measurements. The increase in new bone formation was found to correlate with the amount of Sr released in vitro. The results indicate that sputtered nanostructured Ti-Sr-O coatings showed sustained release of Sr and accelerate osseointegration even in poor-quality bone, and thus, may have impact on practical applications for medical implants.

Nanoscale topographical modification and surface chemistry alteration using bioactive ions are centrally important processes in the current design of the surface of titanium (Ti) bone implants with enhanced bone healing capacity. Macrophages play a central role in the early tissue healing stage and their activity in response to the implant surface is known to affect the subsequent healing outcome. Thus, the positive modulation of macrophage phenotype polarization (i.e. towards the regenerative M2 rather than the inflammatory M1 phenotype) with a modified surface is essential for the osteogenesis funtion of Ti bone implants. However, relatively few advances have been made in terms of modulating the macrophage-centered early healing capacity in the surface design of Ti bone implants for the two important surface properties of nanotopography and and bioactive ion chemistry. We investigated whether surface bioactive ion modification exerts a definite beneficial effect on inducing regenerative M2 macrophage polarization when combined with the surface nanotopography of Ti. Our results indicate that nanoscale topographical modification and surface bioactive ion chemistry can positively modulate the macrophage phenotype in a Ti implant surface. To the best of our knowledge, this is the first demonstration that chemical surface modification using divalent cations (Ca and Sr) dramatically induces the regenerative M2 macrophage phenotype of J774.A1 cells in nanostructured Ti surfaces. In this study, divalent cation chemistry regulated the cell shape of adherent macrophages and markedly up-regulated M2 macrophage phenotype expression when combined with the nanostructured Ti surface. These results provide insight into the surface engineering of future Ti bone implants that are harmonized between the macrophage-governed early wound healing process and subsequent mesenchymal stem cell-centered osteogenesis function.