Smart stimuli-responsive strategies for titanium implant functionalization in bone regeneration and therapeutics

Cascade catalysis nanozyme for interfacial functionalization in combating implant infections associated with diabetes via sonodynamic therapy and adaptive immune activation

Innovative solutions are required for the intervention of implant associated infections (IAIs), especially for bone defect patients with chronic inflammatory diseases like diabetes mellitus (DM). The complex immune microenvironment of infections renders implants with direct antibacterial ability inadequate for the prolonged against of bacterial infections. Herein, a synergistic treatment strategy was presented that combined sonodynamic therapy (SDT) with adaptive immune modulation to treat IAIs in diabetes patients. A multifunctional coating was created on the surface of titanium (Ti) implants, consisting of manganese dioxide nanoflakes (MnO2 NFs) with cascade catalytic enzyme activity and a responsive degradable hydrogel containing a sonosensitizer. The reactive oxygen species (ROS) generated by glucose-hydrogen peroxide (H2O2) cascade catalysis and ultrasound (US) activation sonosensitizer helped kill bacteria and release bacterial antigens. Meanwhile, Mn2+ facilitated dendritic cells (DCs) maturation, enhancing antigen presentation to activate both cellular and humoral adaptive immunity against bacterial infections. This approach effectively eliminated bacteria in established diabetic IAIs model and activated systemic antibacterial immunity, providing long-term antibacterial protection. This study presents a non-antibiotic immunotherapeutic strategy for fighting IAIs in chronic diseases.

Zinc finger-inspired peptide-metal-phenolic nanointerface enhances bone-implant integration under bacterial infection microenvironment through immune modulation and osteogenesis promotion

Orthopedic and dental implantations under bacterial infection microenvironment face significant challenges in achieving high-quality bone-implant integration. Designing implant coatings that incorporate both immune defense and anti-inflammation is difficult in conventional single-functional coatings. We introduce a multifunctional nanointerface using a zinc finger-inspired peptide-metal-phenolic nanocoating, designed to enhance implant osseointegration under such conditions. Abaloparatide (ABL), a second-generation anabolic drug for treating osteoporosis, can be integrated into the design of a zinc-phenolic network constructed on the implant surface (ABL@ZnTA). Importantly, the phenolic-coordinated Zn2+ ions in ABL@ZnTA can act as zinc finger motif to co-stabilize the configuration of ABL through multiple molecular interactions, enabling high bioactivity, high loading capacity (1.36 times), and long-term release (>7 days) of ABL. Our results showed that ABL@ZnTA can modulate macrophage polarization from the pro-inflammatory M1 towards the anti-inflammatory M2 phenotype, promoting immune osteogenesis with increased OCN, ALP, and SOD 1 expression. Furthermore, the ABL@ZnTA significantly reduces inflammatory fibrous tissue encapsulation and enhances the long-term stability of the implants, indicated by enhanced binding strength (6 times) and functional connectivity (1.5-3 times) in the rat bone defect model infected by S. aureus. Overall, our research offers a nano-enabled synergistic strategy that balances infection defense and osteogenesis promotion in orthopedic and dental implantations.

Black phosphorus for bone regeneration: Mechanisms involved and influencing factors

BP has shown good potential for promoting bone regeneration. However, the understanding of the mechanisms of BP-enhanced bone regeneration is still limited. This review first summarizes the recent advances in applications of BP in bone regeneration. We further highlight the possibility that BP enhances bone regeneration by regulating the behavior of mesenchymal stem cells (MSCs), osteoblasts, vascular endothelial cells (VECs), and macrophages, mainly through the regulation of cytoskeletal remodeling, energy metabolism, oxidation resistance and surface adsorption properties, etc. In addition, moderating the physicochemical properties of BP (i.e., shape, size, and surface charge) can alter the effects of BP on bone regeneration. This review reveals the underlying mechanisms of BP-enhanced bone regeneration and provides strategies for further material design of BP-based materials for bone regeneration.

Unveiling the governing role of 'remodeling triangle area' in soft-hard tissue interface equilibrium for metal implants advancement

Metal implants holds significant promise for diverse fixed prostheses. However, their long-term reliability and broader application are hindered by challenges related to the disequilibrium at the soft-hard tissue interface. By using anti-inflammatory (PDA/IL4) and pro-inflammatory (PDA/LPS/IFNγ) coatings to modulate distinct immune characteristics, we discovered a dynamic bioactive structure at the soft-hard tissue interface around metal implant, which we have named the 'Remodeling Triangle Area' (RTA). We further demonstrate that the RTA can be influenced by the PDA/IL4 coating to favor a phenotype that enhances both innate and adaptive immunity. This leads to stronger epithelial adhesion, the formation of dense connective tissue via IGF1 secretion, and a more balanced soft-hard tissue interface through the OPG/RANKL axis. Conversely, the PDA/LPS/IFNγ coating shifts the RTA towards a phenotype that activates the innate immune response. This results in a less cohesive tissue structure and bone resorption, characterized by reduced IGF1 secretion and an imbalanced OPG/RANKL axis. Over all, our study introduces the novel concept termed the 'Remodeling Triangle Area' (RTA), an immune-rich anatomical region located at the nexus of the implant interface, epithelial, connective, and bone tissue, which becomes highly interactive post-implantation to modulate the soft-hard tissue interface equilibrium. We believe that an RTA-centric, immunomodulatory approach has the potential to revolutionize the design of next-generation metal implants, providing unparalleled soft-hard tissue interface equilibrium properties.

Nanoarchitecture-Integrated Hydrogel Boosts Angiogenesis-Osteogenesis-Neurogenesis Tripling for Infected Bone Fracture Healing

Infected fracture healing is a complicated process that includes intricate interactions at the cellular and molecular levels. In addition to angiogenesis and osteogenesis, the significance of neurogenesis in fracture healing has also been recognized in recent years. Here, a nanocomposite hydrogel containing pH-responsive zinc-gallium-humic acids (HAs) nanoparticles is developed. Through the timed release of Zn2+, Ga3+, and HAs, the hydrogel exhibits potent antibacterial effects and promotes angiogenesis, osteogenesis, and neurogenesis. The enhanced neurogenesis further promotes angiogenesis and osteogenesis, forming a mutually supportive angiogenesis-osteogenesis-neurogenesis cycle at the fracture site. The hydrogel achieves rapid infected fracture healing and improves tissue regeneration in mice. This study proposes a comprehensive treatment approach that combines antibacterial effects with the regulation of tissue regeneration to improve infected fracture healing.

Effect of graphene oxide in an injectable hydrogel on the osteogenic differentiation of mesenchymal stem cells

Graphene oxide (GO) is widely used in bone tissue engineering due to its good biocompatibility and proliferation, and is often used in combination with other hydrogels, which not only reduces the cytotoxicity of GO but also improves the mechanical properties of the hydrogels. We developed injectable carboxymethyl chitosan (CMC)/hydroxyethyl cellulose (HEC)/β-tricalcium phosphate (β-TCP)/GO hydrogel via hydrogen bonding cross-linked between (CMC) and (HEC), also, calcium cross-linked by β-TCP was also involved to further improvement of mechanical properties of the hydrogel, and incorporate different concentration of GO in these hydrogel systems. The characterization of the novel hydrogel was tested by scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FT-IR). The swelling ratio and mechanical properties were investigated, the results showed that the addition of GO was able to reduce the swelling rate of hydrogels and improve their mechanical properties, with the best effect in the case of 1 mg/mL content. In vivo experimental studies showed that the hydrogel significantly promoted the osteogenic differentiation of rat bone marrow mesenchymal stem cells (rBMSCs), with the best effect at a concentration of 2 mg/mL. The results of the cellular experiments were similar. Therefore, the novel environment-friendly and non-toxic injectable CMC/HEC/β-TCP/GO hydrogel system may have potential applications in bone tissue engineering.

Dual-functional Hydroxyapatite scaffolds for bone regeneration and precision drug delivery

Addressing infected bone defects remains a significant challenge in orthopedics, requiring effective infection control and bone defect repair. A promising therapeutic approach involves the development of dual-functional engineered biomaterials with drug delivery systems that combine antibacterial properties with osteogenesis promotion. The Hydroxyapatite composite scaffolds offer a one-stage treatment, eliminating the need for multiple surgeries and thereby streamlining the process and reducing treatment time. This review delves into the impaired bone repair mechanisms within pathogen-infected and inflamed microenvironments, providing a theoretical foundation for treating infectious bone defects. Additionally, it explores composite scaffolds made of antibacterial and osteogenic materials, along with advanced drug delivery systems that possess both antibacterial and bone-regenerative properties. By offering a comprehensive understanding of the microenvironment of infectious bone defects and innovative design strategies for dual-function scaffolds, this review presents significant advancements in treatment methods for infectious bone defects. Continued research and clinical validation are essential to refine these innovations, ensuring biocompatibility and safety, achieving controlled release and stability, and developing scalable manufacturing processes for widespread clinical application.

Smart zwitterionic coatings with precise pH-responsive antibacterial functions for bone implants to combat bacterial infections

Hydrophilic antifouling coatings based on zwitterionic polymers have been widely applied for the surface modification of bone implants to combat biofilm formation and reduce the likelihood of implant-related infections. However, their long-term effectiveness is significantly limited by the lack of effective and precise antibacterial activity. Here, a pH-responsive smart zwitterionic antibacterial coating (PSB/GS coating) was designed and robustly fabricated onto titanium-base bone implants by using a facile two-step method. First, dopamine (DA) and a poly(sulfobetaine methacrylate-co-dopamine methacrylamide) (PSBDA) copolymer were deposited on implants via mussel-inspired surface chemistry, resulting in a hydrophilic base coating with abundant catechol residues. Next, an amino-rich antibiotic, gentamicin sulfate (GS), was covalently linked to the coating through the formation of acid-sensitive Schiff base bonds between the amine groups of GS and the catechol residues present in both the zwitterionic polymer and the DA component. During the initial implantation period, the hydrophilic zwitterionic polymers demonstrated the desired anti-fouling properties that could effectively reduce protein and bacterial adhesion by over 90%. With time, the bacterial proliferation led to a decrease in the microenvironment pH value, resulting in the hydrolysis of the acid-sensitive Schiff base bonds, thereby releasing GS on demand and effectively enhancing the anti-biofilm properties of coatings. Benefiting from this synergistic antifouling and smart antibacterial activities, the PSB/GS coating exerted an excellent anti-infective activity in both in vivo preoperative and postoperative infection rat models. This proposed facile yet effective coating strategy is expected to provide a promising solution to combat bone implant-related infections.

Photothermal driven BMSCs osteogenesis and M2 macrophage polarization on polydopamine-coated Ti3C2 nanosheets/poly(vinylidene fluoride trifluoroethylene) nanocomposite coatings

Mild thermal stimulation plays an active role in bone tissue repair and regeneration. In this work, a bioactive polydopamine/Ti3C2/poly(vinylidene fluoride trifluoroethylene) (PDA/Ti3C2/P(VDF-TrFE)) nanocomposite coating with excellent near-infrared light (NIR)-triggered photothermal effect was designed to improve the osteogenic ability of implants. By incorporating dopamine (DA)-modified Ti3C2 nanosheets into the P(VDF-TrFE) matrix and combining them with alkali initiated in situ polymerization, the resulting PDA/Ti3C2/P(VDF-TrFE) nanocomposite coating gained high adhesion strength on Ti substrate, excellent tribological and corrosion resistance properties, which was quite important for clinical application of implant coatings. Cell biology experiments showed that NIR-triggered mild thermal stimulation on the coating surface promoted cell spreading and growth of BMSCs, and also greatly upregulated the osteogenic markers, including Runt-Related Transcription Factor 2 (RUNX2), alkaline phosphatase (ALP), osteopontin (OPN), osteocalcin (OCN). Simultaneously, the synthesis of heat shock protein 47 (HSP47) was significantly promoted by the mild thermal stimulation, which strengthened the specific interaction between HSP47 and collagen Ⅰ (COL-Ⅰ), thereby activating the integrin-mediated MEK/ERK osteogenic differentiation signaling pathway. In addition, the results also showed that the mild thermal stimulation induced the polarization of macrophages towards M2 phenotype, which can attenuate the inflammatory response of injured bone tissue. Antibacterial results indicated that the coating exhibited an outstanding antibacterial ability against S. aureus and E. coli. Conceivably, the versatile implant bioactive coatings developed in this work will show great application potential for implant osseointegration.

Natural Affinity Driven Modification by Silicene to Construct a "Thermal Switch" for Tumorous Bone Loss

Tumorous bone defects present significant challenges for surgical bio-reconstruction due to the dual pathological conditions of residual tumor presence and extensive bone loss following excision surgery. To address this challenge, a "thermal switch" smart bone scaffold based on the silicene nanosheet-modified decalcified bone matrix (SNS@DBM) is developed by leveraging the natural affinity between collagen and silicene, which is elucidated by molecular dynamics simulations. Benefitting from its exceptional photothermal ability, biodegradability, and bioactivity, the SNS@DBM "thermal switch" provides an integrated postoperative sequential thermotherapy for tumorous bone loss by exerting three levels of photothermal stimulation (i.e., strong, moderate, and nonstimulation). During the different phases of postoperative bioconstruction, the SNS@DBM scaffold realizes simultaneous residual tumor ablation, tumor recurrence prevention, and bone tissue regeneration. These biological effects are verified in the tumor-bearing nude mice of patient-derived tissue xenografts and critical cranium defect rats. Mechanism research prompts moderate heat stimulus generated by and coordinating with SNSs can upregulate osteogenic genes, promote macrophages M2 polarization, and intensify angiogenesis of H-type vessels. This study introduces a versatile approach to the management of tumorous bone defects.

The Effect of Antibacterial-Osteogenic Surface Modification on the Osseointegration of Titanium Implants: A Static and Dynamic Strategy

Titanium (Ti) and its alloys are widely used biomaterials in bone repair. Although these biomaterials possess stable properties and good biocompatibility, the high elastic modulus and low surface activity of Ti implants have often been associated with infection, inflammation, and poor osteogenesis. Therefore, there is an urgent need to modify the surface of Ti implants, where changes in surface morphology or coatings loading can confer specific functions to help them adapt to the osseointegration formation phase and resist bacterial infection. This can further ensure a healthy microenvironment for bone regeneration as well as the promotion of immunomodulation, angiogenesis, and osteogenesis. Therefore, in this review, we evaluated various functional Ti implants after surface modification, both in terms of static modifications and dynamic response strategies, mainly focusing on the synergistic effects of antimicrobial activities and functionalized osteogenic. Finally, the current challenges and future perspectives are summarized to provide innovative and effective solutions for osseointegration and bone defect repair.

Advances in biomaterials for oral-maxillofacial bone regeneration: spotlight on periodontal and alveolar bone strategies

The intricate nature of oral-maxillofacial structure and function, coupled with the dynamic oral bacterial environment, presents formidable obstacles in addressing the repair and regeneration of oral-maxillofacial bone defects. Numerous characteristics should be noticed in oral-maxillofacial bone repair, such as irregular morphology of bone defects, homeostasis between hosts and microorganisms in the oral cavity and complex periodontal structures that facilitate epithelial ingrowth. Therefore, oral-maxillofacial bone repair necessitates restoration materials that adhere to stringent and specific demands. This review starts with exploring these particular requirements by introducing the particular characteristics of oral-maxillofacial bones and then summarizes the classifications of current bone repair materials in respect of composition and structure. Additionally, we discuss the modifications in current bone repair materials including improving mechanical properties, optimizing surface topography and pore structure and adding bioactive components such as elements, compounds, cells and their derivatives. Ultimately, we organize a range of potential optimization strategies and future perspectives for enhancing oral-maxillofacial bone repair materials, including physical environment manipulation, oral microbial homeostasis modulation, osteo-immune regulation, smart stimuli-responsive strategies and multifaceted approach for poly-pathic treatment, in the hope of providing some insights for researchers in this field. In summary, this review analyzes the complex demands of oral-maxillofacial bone repair, especially for periodontal and alveolar bone, concludes multifaceted strategies for corresponding biomaterials and aims to inspire future research in the pursuit of more effective treatment outcomes.

pH-Responsive Mesoporous Silica Nanoparticles Loaded with Naringin for Targeted Osteoclast Inhibition and Bone Regeneration

Background

It is well-established that osteoclast activity is significantly influenced by fluctuations in intracellular pH. Consequently, a pH-sensitive gated nano-drug delivery system represents a promising therapeutic approach to mitigate osteoclast overactivity. Our prior research indicated that naringin, a natural flavonoid, effectively mitigates osteoclast activity. However, naringin showed low oral availability and short half-life, which hinders its clinical application. We developed a drug delivery system wherein chitosan, as gatekeepers, coats mesoporous silica nanoparticles loaded with naringin (CS@MSNs-Naringin). However, the inhibitory effects of CS@MSNs-Naringin on osteoclasts and the underlying mechanisms remain unclear, warranting further research.

Methods

First, we synthesized CS@MSNs-Naringin and conducted a comprehensive characterization. We also measured drug release rates in a pH gradient solution and verified its biosafety. Subsequently, we investigated the impact of CS@MSNs-Naringin on osteoclasts induced by bone marrow-derived macrophages, focusing on differentiation and bone resorption activity while exploring potential mechanisms. Finally, we established a rat model of bilateral critical-sized calvarial bone defects, in which CS@MSNs-Naringin was dispersed in GelMA hydrogel to achieve in situ drug delivery. We observed the ability of CS@MSNs-Naringin to promote bone regeneration and inhibit osteoclast activity in vivo.

Results

CS@MSNs-Naringin exhibited high uniformity and dispersity, low cytotoxicity (concentration≤120 μg/mL), and significant pH sensitivity. In vitro, compared to Naringin and MSNs-Naringin, CS@MSNs-Naringin more effectively inhibited the formation and bone resorption activity of osteoclasts. This effect was accompanied by decreased phosphorylation of key factors in the NF-κB and MAPK signaling pathways, increased apoptosis levels, and a subsequent reduction in the production of osteoclast-specific genes and proteins. In vivo, CS@MSNs-Naringin outperformed Naringin and MSNs-Naringin, promoting new bone formation while inhibiting osteoclast activity to a greater extent.

Conclusion

Our research suggested that CS@MSNs-Naringin exhibited the strikingly ability to anti-osteoclasts in vitro and in vivo, moreover promoted bone regeneration in the calvarial bone defect.

An osteoinductive surface by adhesive bone morphogenetic protein-2 prepared using the bioorthogonal approach for tight binding of titanium with bone

Inorganic biomaterials are used in various orthopedic and dental implants. Nevertheless, they cause clinical issues such as loosening of implants and patient morbidity. Therefore, inspired by mussel adhesive proteins, we aimed to design an adhesive and dimer-forming highly active bone morphogenetic protein-2 (BMP-2) using bioorthogonal chemistry, in which recombinant DNA technology was combined with enzymatic modifications, to achieve long-term osseointegration with titanium. The prepared BMP-2 exhibited substantially higher binding activity than wild-type BMP-2, while the adhered BMP-2 was more active than soluble BMP-2. Therefore, the adhesive BMP-2 was immobilized onto titanium wires and screws and implanted into rat bones, and long-term osteogenesis was evaluated. Adhesive BMP-2 promoted the mechanical binding of titanium to bones, enabling efficient bone regeneration and effective stabilization of implants. Thus, such adhesive biosignaling proteins can be used in regenerative medicine.

External Stimuli-Responsive Strategies for Surface Modification of Orthopedic Implants: Killing Bacteria and Enhancing Osteogenesis

Bacterial infection and insufficient osteogenic activity are the main causes of orthopedic implant failure. Conventional surface modification methods are difficult to meet the requirements for long-term implant placement. In order to better regulate the function of implant surfaces, especially to improve both the antibacterial and osteogenic activity, external stimuli-responsive (ESR) strategies have been employed for the surface modification of orthopedic implants. External stimuli act as "smart switches" to regulate the surface interactions with bacteria and cells. The balance between antibacterial and osteogenic capabilities of implant surfaces can be achieved through these specific ESR manifestations, including temperature changes, reactive oxygen species production, controlled release of bioactive molecules, controlled release of functional ions, etc. This Review summarizes the recent progress on different ESR strategies (based on light, ultrasound, electric, and magnetic fields) that can effectively balance antibacterial performance and osteogenic capability of orthopedic implants. Furthermore, the current limitations and challenges of ESR strategies for surface modification of orthopedic implants as well as future development direction are also discussed.

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.

Dimethyloxallyl glycine-loaded mesoporous bioactive glass/poly(D,L-lactide) composite scaffolds with ultrasound stimulation for promoting bone repair

Introduction: Bone tissue engineering is considered the ideal approach for bone repair. Mesoporous bioactive glass (MBG) possesses the characteristics of high drug-loading capacity and bioactivity. Low-intensity pulsed ultrasound contributes to promoting fracture healing and bone defect repair, and dimethyloxalyl glycine (DMOG) is a small molecular inhibitor that can suppress prolyl hydroxylase, reducing the degradation of hypoxia-inducible factor. Methods: In this study, we proposed to prepare DMOG-loaded MBG/poly(D,L-lactide) composite scaffolds (DMOG-MBG/PDLLA) for promoting bone repair. The effects of ultrasound stimulation and DMOG release on the cell responses of rat bone marrow mesenchymal stem cells (BMSCs) and human umbilical vein endothelial cells (HUVECs) and bone repair in vivo were investigated. Results and Discussion: The results showed that both ultrasound stimulation and DMOG release could promote the proliferation, adhesion and differentiation of BMSCs and HUVECs, respectively. After the implantation of scaffolds in rat cranial bone defect model for 8 weeks, the results indicated that the combined ultrasound stimulation and DMOG release contributed to the highest ability for promoting bone repair. Hence, the DMOG-MBG/PDLLA scaffolds with ultrasound stimulation are promising for application in bone repair.

Effect of the Sr-Fe layered double hydroxide coating based on the microenvironment response on implant osseointegration in osteoporotic rats

Osteoporosis is a disease that manifests itself as an abnormality of bone metabolism and is characterized by low bone mass and destruction of the bone microstructure. Since bone resorption occurs more rapidly than new bone formation, osteoporosis leads to reduced orthopedic implant stability. From a microenvironmental point of view, the rationale for this outcome is that osteoclasts are overactive in the bone tissue of patients with osteoporosis, and the large amount of H+ they produce leads to local chronic acidosis, which promotes bone mineral loss. Therefore, we designed a weakly alkaline layered double hydroxide (LDH) coating to modulate the pathologically acidic microenvironment and the osteogenic-osteoclastic coupling by releasing Sr2+. We prepared Sr-Fe LDH coatings on pure titanium implants using a hydrothermal method in this study and characterized the material using SEM, AFM, XRD, XPS, EDS, ICP, pH acidimeter, etc. We found that the coatings had good nanomorphology and were able to efficiently neutralize H+ as well as steadily release Sr2+ for up to 21 days. In vitro, the coating not only significantly promoted the adhesion, proliferation, and differentiation of osteoblasts, but also inhibited the differentiation of osteoclasts at the same time. In addition, in animal experiments, the coating significantly improved the mechanical stability of the implant in osteoporotic rats, increasing Sr-Fe LDH@Ti maximal push-out force by 72.2% compared to Ti. At the same time, the coating was effective in reversing the osteoporotic state, resulting in a 58.5% increase in BV/TV (%), and a 12.4% increase in Tb. N (1 mm-1), a 31.6% increase in Tb. Th (μm), and a 30.9% increase in BA (%). Our results suggest that this Sr-Fe LDH nanocoating material with acid-neutralizing, as well as long-term Sr2+-releasing capabilities, is a novel and effective orthopedic implant coating material under osteoporotic conditions.

Synergistic Amelioration of Osseointegration and Osteoimmunomodulation with a Microarc Oxidation-Treated Three-Dimensionally Printed Ti-24Nb-4Zr-8Sn Scaffold via Surface Activity and Low Elastic Modulus

Biomaterial scaffolds, including bone substitutes, have evolved from being primarily a biologically passive structural element to one in which material properties such as surface topography and chemistry actively direct bone regeneration by influencing stem cells and the immune microenvironment. Ti-6Al-4V(Ti6Al4V) implants, with a significantly higher elastic modulus than human bone, may lead to stress shielding, necessitating improved stability at the bone-titanium alloy implant interface. Ti-24Nb-4Zr-8Sn (Ti2448), a low elastic modulus β-type titanium alloy devoid of potentially toxic elements, was utilized in this study. We employed 3D printing technology to fabricate a porous scaffold structure to further decrease the structural stiffness of the implant to approximate that of cancellous bone. Microarc oxidation (MAO) surface modification technology is then employed to create a microporous structure and a hydrophilic oxide ceramic layer on the surface and interior of the scaffold. In vitro studies demonstrated that MAO treatment enhances the proliferation, adhesion, and osteogenesis capabilities on the scaffold surface. The chemical composition of the MAO-Ti2448 oxide layer is found to enhance the transcription and expression of osteogenic genes in bone mesenchymal stem cells (BMSCs), potentially related to the enrichment of Nb2O5 and SnO2 in the oxide layer. The MAO-Ti2448 scaffold, with its synergistic surface activity and low stiffness, significantly activates the anti-inflammatory macrophage phenotype, creating an immune microenvironment that promotes the osteogenic differentiation of BMSCs. In vivo experiments in a rabbit model demonstrated a significant improvement in the quantity and quality of the newly formed bone trabeculae within the scaffold under the contact osteogenesis pattern with a matched elastic modulus. These trabeculae exhibit robust connections to the external structure of the scaffold, accelerating the formation of an interlocking structure between the bone and implant and providing higher implantation stability. These findings suggest that the MAO-Ti2448 scaffold has significant potential as a bone defect repair material by regulating osteoimmunomodulation and osteogenesis to enhance osseointegration. This study demonstrates an optional strategy that combines the mechanism of reducing the elastic modulus with surface modification treatment, thereby extending the application scope of β-type titanium alloy.

Nanoscaled Titanium Oxide Layer Provokes Quick Osseointegration on 3D-Printed Dental Implants: A Domino Effect Induced by Hydrophilic Surface

Three-dimensional printing is a revolutionary strategy to fabricate dental implants. Especially, 3D-printed dental implants modified with nanoscaled titanium oxide layer (H-SLM) have impressively shown quick osseointegration, but the accurate mechanism remains elusive. Herein, we unmask a domino effect that the hydrophilic surface of the H-SLM facilitates blood wetting, enhances the blood shear rate, promotes blood clotting, and changes clot features for quick osseointegration. Combining computational fluid dynamic simulation and biological verification, we find a blood shear rate during blood wetting of the hydrophilic H-SLM 1.2-fold higher than that of the raw 3D-printed implant, which activates blood clot formation. Blood clots formed on the hydrophilic H-SLM demonstrate anti-inflammatory and pro-osteogenesis effects, leading to a 1.5-fold higher bone-to-implant contact and a 1.8-fold higher mechanical anchorage at the early stage of osseointegration. This mechanism deepens current knowledge between osseointegration speed and implant surface characteristics, which is instructive in surface nanoscaled modification of multiple 3D-printed intrabony implants.