Promoting Osseointegration of Ti Implants through Micro/Nanoscaled Hierarchical Ti Phosphate/Ti Oxide Hybrid Coating

Evaluation of bioactivity and antibacterial properties of Ti6Al4V-based green biocomposite implant encompassing TiO2 nanotube arrays and garlic extract

This study involved the incorporation of an antibacterial garlic extract into titanium oxide nanotubes (TNTs) formed via the anodization of Ti6Al4V implants. The garlic extract, obtained through low-temperature extraction aided by ultrasound waves, was loaded into the nanotubes. The presence of the nanotubes was confirmed through X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDS), and scanning electron microscopy (SEM). Fourier-transform infrared spectroscopy (FT-IR) and gas chromatography-mass spectrometry (GC-MS) were used to investigate the presence of bioactive compounds, particularly sulfur compounds responsible for garlic's antibacterial effects. The impact of loading two concentrations (0.1 and 0.2 g per milliliter) of garlic extract on Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) bacteria was examined. Results indicated a decrease in the growth range of S. aureus from 109 to 106 (CFU/ml) and E. coli from 1011 to 109 (CFU/ml) upon treatment. Additionally, cell adhesion and viability tests conducted on MG63 cells revealed an 8% increase in cell viability with the 0.1 g per milliliter concentration and a 35% decrease with the 0.2 g per milliliter concentration of garlic extract after 72 h of incubation (They have been evaluated by Microculture tetrazolium (MTT) assay). GC-MS analysis identified the presence of diethyl phthalate compounds in the garlic extract, suggesting a potential correlation with cellular toxicity observed in the sample with the higher concentration (0.2 g per milliliter) of garlic extract. Overall, the TNTs loaded with 0.1 g per milliliter of garlic extract simultaneously demonstrated antibacterial activity, cell viability, adhesion, and growth enhancement.

Black phosphorus-incorporated novel Ti-12Mo-10Zr implant for multimodal treatment of osteosarcoma

The repair and reconstruction of large bone defects after bone tumor resection is still a great clinical challenge. At present, orthopedic implant reconstruction is the mainstream treatment for repairing bone defects. However, according to clinical feedback, local tumor recurrence and nonunion of bone graft are common reasons leading to the failure of bone defect repair and reconstruction after bone tumor resection, which seriously threaten the physical and mental health of patients. On this basis, here the self-developed low modulus Ti-12Mo-10Zr alloy (TMZ) was chosen as substrate material. To improve its biological activity and osteointegration, calcium, oxygen, and phosphorus co-doped microporous coating was prepared on TMZ alloy by microarc oxidation (MAO). Then, black phosphorus (BP) nanosheets were incorporated onto MAO treated TMZ alloy to obtain multifunctional composites. The obtained BP-MAO-TMZ implant exhibited excellent photothermal effects and effective ablation of osteosarcoma cancer cells under the irradiation of 808 nm near infrared laser, while no photothermal or therapeutic effects were observed for TMZ alloy. Meanwhile, the structure/component bionic coating obtained after MAO treatment as well as the P-driven in situ biomineralization performance after incorporation of BP nanosheets endowed BP-MAO-TMZ implant with synergistic promoting effect on MC3T3-E1 osteoblasts' activity, proliferation and differentiation ability. This study is expected to provide effective clinical solutions for problems of difficult bone regeneration and tumor recurrence after tumor resection in patients with bone tumors and to solve a series of medical problems such as poor prognosis and poor postoperative quality of patients life with malignant bone tumors.

Surface-modified titanium and titanium-based alloys for improved osteogenesis: A critical review

As implantable materials, titanium, and its alloys have garnered enormous interest from researchers for dental and orthopedic procedures. Despite their success in wide clinical applications, titanium, and its alloys fail to stimulate osteogenesis, resulting in poor bonding strength with surrounding bone tissue. Optimizing the surface topology and altered compositions of titanium and titanium-based alloys substantially promotes peri-implant bone regeneration. This review summarizes the utilization and importance of various osteogenesis components loaded onto titanium and its alloys. Further, different surface-modification methods and the release efficacy of loaded substances are emphasized. Finally, we summarize the article with prospects. We believe that further investigation studies must focus on identifying novel loading components, exploring various innovative, optimized surface-modification methods, and developing a sustained-release system on implant surfaces to improve peri-implant bone formation.

Metal ions: the unfading stars of bone regeneration-from bone metabolism regulation to biomaterial applications

In recent years, bone regeneration has emerged as a remarkable field that offers promising guidance for treating bone-related diseases, such as bone defects, bone infections, and osteosarcoma. Among various bone regeneration approaches, the metal ion-based strategy has surfaced as a prospective candidate approach owing to the extensive regulatory role of metal ions in bone metabolism and the diversity of corresponding delivery strategies. Various metal ions can promote bone regeneration through three primary strategies: balancing the effects of osteoblasts and osteoclasts, regulating the immune microenvironment, and promoting bone angiogenesis. In the meantime, the complex molecular mechanisms behind these strategies are being consistently explored. Moreover, the accelerated development of biomaterials broadens the prospect of metal ions applied to bone regeneration. This review highlights the potential of metal ions for bone regeneration and their underlying mechanisms. We propose that future investigations focus on refining the clinical utilization of metal ions using both mechanistic inquiry and materials engineering to bolster the clinical effectiveness of metal ion-based approaches for bone regeneration.

Advances and Prospects in Materials for Craniofacial Bone Reconstruction

The craniofacial region is composed of 23 bones, which provide crucial function in keeping the normal position of brain and eyeballs, aesthetics of the craniofacial complex, facial movements, and visual function. Given the complex geometry and architecture, craniofacial bone defects not only affect the normal craniofacial structure but also may result in severe craniofacial dysfunction. Therefore, the exploration of rapid, precise, and effective reconstruction of craniofacial bone defects is urgent. Recently, developments in advanced bone tissue engineering bring new hope for the ideal reconstruction of the craniofacial bone defects. This report, presenting a first-time comprehensive review of recent advances of biomaterials in craniofacial bone tissue engineering, overviews the modification of traditional biomaterials and development of advanced biomaterials applying to craniofacial reconstruction. Challenges and perspectives of biomaterial development in craniofacial fields are discussed in the end.

Efficient Osteogenic Activity of PEEK Surfaces Achieved by Femtosecond Laser-Hydroxylation

Poly(etheretherketone) (PEEK) is regarded as an attractive orthopedic material because of its good biocompatibility and mechanical properties similar to natural bone. The efficient activation methods for the surfaces of PEEK matrix materials have become a hot research topic. In this study, a method using a femtosecond laser (FSL) followed by hydroxylation was developed to achieve efficient bioactivity. It produces microstructures, amorphous carbon, and grafted -OH groups on the PEEK surface to enhance hydrophilicity and surface energy. Both experimental and simulation results show that our modification leads to a superior ability to induce apatite deposition on the PEEK surface. The results also demonstrate that efficient grafting of C-OH through FSL-hydroxylation can effectively enhance cell proliferation and osteogenic differentiation compared to other modifications, thus improving osteogenic activity. Overall, FSL hydroxylation treatment is proved to be a simple, efficient, and environmentally friendly modification method for PEEK activation. It could expand the applications of PEEK in orthopedics, as well as promote the surface modification and structural design of other polymeric biomaterials to enhance bioactivity.

A Bioinspired Gelatin-Amorphous Calcium Phosphate Coating on Titanium Implant for Bone Regeneration

Biocompatible and bio-active coatings can enhance and accelerate osseointegration via chemical binding onto substrates. Amorphous calcium phosphate (ACP) has been shown as a precursor to achieve mineralization in vertebrates and invertebrates under the control of biological macromolecules. This work presents a simple bioinspired Gelatin-CaPO4 (Gel-CaP) composite coating on titanium surfaces to improve osseointegration. The covalently bound Gel-CaP composite is characterized as an ACP-Gel compound via SEM, FT-IR, XRD, and HR-TEM. The amorphous compound coating exhibits a nanometer range thickness and improved elastic modulus, good wettability, and nanometric roughness. The amount of grafted carboxyl groups and theoretical thickness of the coatings are also investigated. More importantly, MC3T3 cells, an osteoblast cell line, show excellent cell proliferation and adhesion on the Gel-CaP coating. The level of osteogenic genes is considerably upregulated on Ti with Gel-CaP coatings compared to uncoated Ti, demonstrating that Gel-CaP coatings possess a unique osteogenic ability. To conclude, this work offers a new perspective on functional, bioactive titanium coatings, and Gel-CaP composites can be a low-cost and promising candidate in bone regeneration.

Hierarchically Structured Hydroxyapatite Particles Facilitate the Enhanced Integration and Selective Anti-Tumor Effects of Amphiphilic Prodrug for Osteosarcoma Therapy

Efficient delivery of cargo into target cells is a formidable challenge in modern medicine. Despite the great promise of biomimetic hydroxyapatite (HA) particles in tissue engineering, their potential applications in bone tumor therapy, particularly their structure-function relationships in cargo delivery to target cells, have not yet been well explored. In this study, biomimetic multifunctional composite microparticles (Bm-cMPs) are developed by integrating an amphiphilic prodrug of curcumin with hierarchically structured HA microspheres (Hs-hMPs). Then, the effects of the hierarchical structure of vehicles on the integration and delivery of cargo as well as the anti-osteosarcoma (OS) effect of the composite are determined. Different hierarchical structures of the vehicles strongly influence the self-assembly behavior of the prodrug. The flake-like crystals of Hs-hMPs enable the highest loading capacity and enhance the stability of the cargo. Compared to the normal cells, OS cells exhibit 3.56-times better uptake of flake-like Hs-hMPs, facilitating the selective anti-tumor effect of the prodrug. Moreover, Bm-cMPs suppress tumor growth and metastasis by promoting apoptosis and inhibiting cell proliferation and tumor vascularization. The findings shed light on the potential application of Bm-cMPs and suggest a feasible strategy for developing an effective targeted therapy platform using hierarchically structured minerals for OS treatment.

Construction of a Ni(OH)2@CaTiO3 heterostructure on a Ti implant for enhanced osseointegration through NIR photoactivated bacterial inactivation and microenvironment optimization

Desirable antibacterial and osseointegration abilities are essentially important for long-term survival of a Ti-orthopedic implant. Herein, a near-infrared light (NIR) excited antibacterial platform with excellent osseointegration composed of perovskite calcium titanate/nickel hydroxide on a Ti implant (Ni(OH)₂@CaTiO₃/Ti) was designed and successfully fabricated. The construction of the heterostructure efficiently separated the photogenerated electron-hole pairs to produce sufficient reactive oxygen species (ROS), which enabled the photoactivated bacterial inactivation (PBI) of Ti implants. The results showed that the surface-modified Ti implant displayed remarkable antibacterial ability with bacterial inhibition rates of 95.5% for E. coli and 93.8% for S. aureus under NIR excitation. Also, the intervention of Ni(OH)₂ could create a slightly alkaline surface on the Ti implant, which synchronized with Ca-rich CaTiO₃ to regulate the osteogenic microenvironment in favor of the adhesion, proliferation and differentiation of MC3T3-E1 cells as well as the up-regulation of osteogenesis-related gene expressions. The in vivo implantation experiments further confirmed that the heterostructured coating prominently accelerated the formation of new bone and promoted the osseointegration of Ti implants. Our work may provide a novel concept for improving the antibacterial and osseointegration abilities of Ti implants in orthopedic and dental applications.

Wetting of Cell Aggregates on Microdisk Topography Structures Achieved by Maskless Optical Projection Lithography

Cell aggregates as a 3D culture model can effectively mimic the physiological processes such as embryonic development, immune response, and tissue renewal in vivo. Researches show that the topography of biomaterials plays an important role in regulating cell proliferation, adhesion, and differentiation. It is of great significance to understand how cell aggregates respond to surface topography. Herein, microdisk array structures with the optimized size are used to investigate the wetting of cell aggregates. Cell aggregates exhibit complete wetting with distinct wetting velocities on the microdisk array structures of different diameters. The wetting velocity of cell aggregates reaches a maximum of 293 µm h^-1 on microdisk structures with a diameter of 2 µm and is a minimum of 247 µm h^-1 on microdisk structures of 20 µm diameter, which suggests that the cell-substrates adhesion energy on the latter is smaller. Actin stress fibers, focal adhesions (FAs), and cell morphology are analyzed to reveal the mechanisms of variation of wetting velocity. Furthermore, it is demonstrated that cell aggregates adopt climb and detour wetting modes on small and large-sized microdisk structures, respectively. This work reveals the response of cell aggregates to micro-scale topography, providing guidance for better understanding of tissue infiltration.

Mussel-inspired alkaline phosphatase-specific coating on orthopedic implants for spatiotemporal modulating local osteoimmune microenvironment to facilitate osseointegration

Inadequate initial osseointegration and consequent prosthesis loosening are the most severe complications after artificial arthroplasty. Proper immune responses are crucial for the successful implantation of artificial prostheses. Macrophages are central in osteoimmunomodulation because they exert distinct functions with highly plasticity. Herein, we developed an alkaline phosphatase (ALP) sensitive mussel-inspired coating on orthopedic implants for promoting osseointegration. First, the resveratrol-alendronate complexes were deposited on titanium implant surface through mussel-inspired interfacial interactions. Upon prosthesis implantation, macrophages first polarized towards M1 type to initiate inflammatory responses and bone regeneration. As osteogenesis progresses, increasing amounts of ALP secreted by osteoblasts was cleaved the resveratrol-alendronate complexes. Then, the released resveratrol further promoted osteogenic differentiation of BMSCs and induced locoregional macrophages M2 polarization. Our results demonstrated that the bioinspired osteoimmunomodulation coating remarkably facilitated the prosthesis-bone integration by spatiotemporally modulating macrophages switching from M1 to M2 polarization in response to a real-time healing signal during osteogenesis. In summary, the mussel-inspired osteoimmunomodulation coating technology may provide a new approach for promoting osseointegration after artificial arthroplasty.

In situ titanium phosphate formation on a titanium implant as ultrahigh bonding with nano-hydroxyapatite coating for rapid osseointegration

Titanium (Ti) has been widely used as a dental implant material due to its excellent mechanical property and good biocompatibility. However, its poor biological activity severely limits its ability to bond with bony tissues. To ameliorate this situation, a preparation method of ultra-high bonding nano-hydroxyapatite (n-HA) coating on the Ti surface is urgently needed. Here, Ti phosphate/n-HA (TiP-Ca) composite coatings with ultra-high bonding were prepared by a two-step hydrothermal treatment. The TiP coating was first formed in situ on the pure Ti substrate and then n-HA crystals further grew on the TiP surface. The formation mechanism of composite coating and reasons for increased bonding strength were systematically investigated. The results show that the TiP-Ca coating remains stable and exhibits an ultra-high bonding strength with the Ti implant (up to 783.30 ± 207.46 N). An effective solution was designed to address the problems of easy peel off. Cell experiments showed that TiP-Ca could promote the adhesion of MC3T3-E1 and expression of OCN, Runx2, and ALP. In vivo evaluation further confirmed that the TiP-Ca composite coating significantly enhanced osseointegration. The designed coating shows great potential in clinical application of implants.

Micron/Submicron Scaled Hierarchical Ti Phosphate/Ti Oxide Hybrid Coating on 3D Printed Scaffolds for Improved Osteointegration

Three-dimensional (3D) printed implants have attracted substantial attention in the field of personalized medicine, but negative impacts on mechanical properties or initial osteointegration have limited their application. To address these problems, we prepared hierarchical Ti phosphate/Ti oxide (TiP-Ti) hybrid coatings on 3D printed Ti scaffolds. The surface morphology, chemical composition, and bonding strength of the scaffolds were characterized by scanning electron microscopy (SEM), atomic force microscopy (AFM), contact angle measurement, X-ray diffraction (XRD), and scratch test. In vitro performance was analyzed by colonization and proliferation of rat bone marrow mesenchymal stem cells (BMSCs). In vivo osteointegration of the scaffolds in rat femurs was assessed by micro-CT and histological analyses. The results demonstrated improved cell colonization and proliferation as well as excellent osteointegration obtained by incorporation of our scaffolds with the novel TiP-Ti coating. In conclusion, micron/submicron scaled Ti phosphate/Ti oxide hybrid coatings on 3D printed scaffolds have promising potential in future biomedical applications.

Novel Titanium Implant: A 3D Multifunction Architecture with Charge-Trapping and Piezoelectric Self-Stimulation

Implant-associated infection and inflammation are the main causes of implant failure, causing irreversible damage and significantly increasing clinical risks and economic losses. In this study, a 3D multifunctional architecture is constructed that consisted of hierarchical TiO₂ nanotubes (NTs) and electrospun polyvinylidene fluoride nanofiber layers on the surface of a titanium implant. The movement of bacteria through the nanofiber layer is facilitated by its appropriate pore sizes and electrostatic interactions to reach the NT layer where the bacteria are killed by positive charge traps. In contrast, the macrophages tend to adhere to the nanofiber layer. The mechanical interactions between the macrophages and piezoelectric nanofibers generate a self-stimulated electric field that regulated an anti-inflammatory phenotype. This study provides a new method for multifunctional implant materials with antibacterial, piezoelectrically self-stimulated anti-inflammatory, and osteointegration properties that are driven by electrical stimulation.

Gene-activated titanium implants for gene delivery to enhance osseointegration

Osseointegration is the direct and intimate contact between mineralized tissue and titanium implant at the bone-implant interface. Early establishment and stable maintenance of osseointegration is the key to long-term implant success. However, in patients with compromised conditions such as osteoporosis and patients beginning early load-bearing activities such as walking, lower osseointegration around titanium implants is often observed, which might result in implant early failure. Gene-activated implants show an exciting prospect of combining gene delivery and biomedical implants to solve the problems of poor osseointegration formation, overcoming the shortcomings of protein therapy, including rapid degradation and overdose adverse effects. The conception of gene-activated titanium implants is based on "gene-activated matrix" (GAM), which means scaffolds using non-viral vectors for in situ gene delivery to achieve a long-term and efficient transfection of target cells. Current preclinical studies in animal models have shown that plasmid DNA (pDNA), microRNA (miRNA), and small interference RNA (siRNA) functionalized titanium implants can enhance osseointegration with safety and efficiency, leading to the expectation of applying this technique in dental and orthopedic clinical scenarios. This review aims to comprehensively summarize fabrication strategies, current applications, and futural outlooks of gene-activated implants, emphasizing nucleic acid targets, non-viral vectors, implant surface modification techniques, nucleic acid/vector complexes loading strategies.

Surface modification of new innocuous Ti-Mo-Zr based alloys for biomedical applications

To address the clinical challenges of modulus mismatch, lack of initial osteointegration and contain toxic elements towards traditional titanium and its alloys with surrounding bone tissue, a new β-type titanium alloy (Ti-12Mo-10Zr) designed by our group will be chosen as dental implant in this proposal due to its excellent properties, e.g. low young's modulus (~ 50.8 GPa) and excellent compressive yield strength (~ 430.89 MPa). A modified hydrothermal and pressure method will be deployed to create tailored micro/nano topography and chemistry (phosphorus) on implant surface with the aim of promoting osteointegration. The formation process and mechanism of micro/nano-scaled hierarchical hybrid coating containing phosphorous will be revealed from the perspective of energetics and crystallography to realize co-design of multiple structure and chemical on Ti-12Mo-10Zr surface. The in vitro cytological performance of this hierarchical hybrid coating containing phosphorous will also be evaluated by co-culturing with rat bone marrow stromal cells This proposal will not only provide guidance and experimental database for next generation potential implant named Ti-12Mo-10Zr, but also display new insights to improve long-lasting stability for dental implant which demonstrate tremendous scientific significance.

Surface Functionalization of Hydroxyapatite Scaffolds with MgAlEu-LDH Nanosheets for High-Performance Bone Regeneration

Although artificial bone repair scaffolds, such as titanium alloy, bioactive glass, and hydroxyapatite (HAp), have been widely used for treatment of large-size bone defects or serious bone destruction, they normally exhibit unsatisfied bone repair efficiency because of their weak osteogenic and angiogenesis performance as well as poor cell crawling and adhesion properties. Herein, the surface functionalization of MgAlEu-layered double hydroxide (MAE-LDH) nanosheets on porous HAp scaffolds is reported as a simple and effective strategy to prepare HAp/MAE-LDH scaffolds for enhanced bone regeneration. The surface functionalization of MAE-LDHs on the porous HAp scaffold can significantly improve its surface roughness, specific surface, and hydrophilicity, thus effectively boosting the cells adhesion and osteogenic differentiation. Importantly, the MAE-LDHs grown on HAp scaffolds enable the sustained release of Mg2+ and Eu3+ ions for efficient bone repair and vascular regeneration. In vitro experiments suggest that the HAp/MAE-LDH scaffold presents much enhanced osteogenesis and angiogenesis properties in comparison with the pristine HAp scaffold. In vivo assays further reveal that the new bone mass and mineral density of HAp/MAE-LDH scaffold increased by 3.18- and 2.21-fold, respectively, than that of pristine HAp scaffold. The transcriptome sequencing analysis reveals that the HAp/MAE-LDH scaffold can activate the Wnt/β-catenin signaling pathway to promote the osteogenic and angiogenic abilities.

Applications of Titanium Dioxide Nanostructure in Stomatology

Breakthroughs in the field of nanotechnology, especially in nanochemistry and nanofabrication technologies, have been attracting much attention, and various nanomaterials have recently been developed for biomedical applications. Among these nanomaterials, nanoscale titanium dioxide (nano-TiO₂) has been widely valued in stomatology due to the fact of its excellent biocompatibility, antibacterial activity, and photocatalytic activity as well as its potential use for applications such as dental implant surface modification, tissue engineering and regenerative medicine, drug delivery carrier, dental material additives, and oral tumor diagnosis and treatment. However, the biosafety of nano-TiO₂ is controversial and has become a key constraint in the development of nano-TiO₂ applications in stomatology. Therefore, in this review, we summarize recent research regarding the applications of nano-TiO₂ in stomatology, with an emphasis on its performance characteristics in different fields, and evaluations of the biological security of nano-TiO₂ applications. In addition, we discuss the challenges, prospects, and future research directions regarding applications of nano-TiO₂ in stomatology that are significant and worthy of further exploration.

Immunomodulation and osseointegration activities of Na2TiO3 nanorods-arrayed coatings doped with different Sr content

To endow Ti-based orthopedic implants immunomodulatory capability and thus enhanced osseointegration, different amounts of Sr are doped in Na2TiO3 nanorods in the arrays with identical nanotopographic parameters (rod diameter, length and inter-rod spacing) by substitution of Na+ using hydrothermal treatment. The obtained arrays are denoted as STSr2, STSr4, and STSr7, where the arabic numbers indicate the incorporating amounts of Sr in Na2TiO3. The modulation effects of the Sr-doped nanorods arrays on macrophage polarization and osteogenetic functions of osteoblasts are investigated, together with the array without Sr (ST). Moreover, osseointegration of these arrays are also assayed in rat femoral condyles. Sr-doped nanorods arrays accelerate M1 (pro-inflammatory phenotype)-to-M2 (anti-inflammatory phenotype) transformation of the adhered macrophages, enhancing secretion of pro-osteogenetic cytokines and growth factors (TGF-β1 and BMP2), moreover, the Sr doped arrays directly enhance osteogenetic functions of osteoblasts. The enhancement of paracrine of M2 macrophages and osteogenetic function of osteoblasts is promoted with the increase of Sr incorporating amounts. Consequently, Sr doped arrays show significantly enhanced osseointegration in vivo compared to ST, and STSr7 exhibits the best performance. Our work sheds a new light on the design of surface chemical components and structures for orthopedic implants to enhance their osseointegration.

Icariin-loaded Sulfonated Polyetheretherketone with Osteogenesis Promotion and Osteoclastogenesis Inhibition Properties via Immunomodulation for Advanced Osseointegration

Preventing prosthesis loosening due to insufficient osseointegration is critical for patients with osteoporosis. Endowing implants with immunomodulatory function can effectively enhance osseointegration. In this work, we loaded icariin (ICA) onto...

Hierarchical microgroove/nanopore topography regulated cell adhesion to enhance osseointegration around intraosseous implants in vivo

Implant surface topography plays a crucial role in achieving successful implantation. Simple and controllable surface topographical modifications are considered a promising method to accelerate bone osseointegration for biomedical applications. Moreover, comprehension of the mechanism between surface topography and cell osteogenic differentiation is vital for the manipulation of these processes to promote bone tissue regeneration. In this study, we investigated the effects of implant surfaces with various sized hierarchical microgroove/nanopore topographies on cell adhesion, osteogenesis, and their underlying mechanism both in vitro and in vivo. Our findings reveal that a titanium surface with an appropriately sized microgroove/nanopore topography (SLM-1MAH) exhibits the more satisfactory adhesive and osteogenic efficiency than the clinically used sand-blasted, large-grit, and acid-etched (SLA) surface. The underlying molecular mechanism lies in the activation of the integrin α2-PI3K-Akt signaling pathway, where the SLM-1MAH surface increased the protein expressions of integrin α2 (Itga2), phosphatidylinositol 3-kinase (PI3K), and phosphorylated serine/threonine kinase Akt (p-Akt) to enhance osteogenesis and osseointegration. Furthermore, the SLM-1MAH surface also displays better osseointegration efficiency with stronger bonding strength than that on the SLA surface. This work provides a novel strategy for implant surface topography design to improve bone-implant osseointegration.

Cyclic Mechanical Strain Regulates Osteoblastic Differentiation of Mesenchymal Stem Cells on TiO2 Nanotubes Through GCN5 and Wnt/β-Catenin

Bone marrow mesenchymal stem cells (BMSCs) play a critical role in bone formation and are extremely sensitive to external mechanical stimuli. Mechanical signals can regulate the biological behavior of cells on the surface of titanium-related prostheses and inducing osteogenic differentiation of BMSCs, which provides the integration of host bone and prosthesis benefits. But the mechanism is still unclear. In this study, BMSCs planted on the surface of TiO₂ nanotubes were subjected to cyclic mechanical stress, and the related mechanisms were explored. The results of alkaline phosphatase staining, real-time PCR, and Western blot showed that cyclic mechanical stress can regulate the expression level of osteogenic differentiation markers in BMSCs on the surface of TiO₂ nanotubes through Wnt/β-catenin. As an important member of the histone acetyltransferase family, GCN5 exerted regulatory effects on receiving mechanical signals. The results of the ChIP assay indicated that GCN5 could activate the Wnt promoter region. Hence, we concluded that the osteogenic differentiation ability of BMSCs on the surface of TiO₂ nanotubes was enhanced under the stimulation of cyclic mechanical stress, and GCN5 mediated this process through Wnt/β-catenin.

Antimicrobial Peptides-Loaded Hydroxyapatite Microsphere With Different Hierarchical Structures for Enhanced Drug Loading, Sustained Release and Antibacterial Activity

Antimicrobial peptides (AMPs) have great potential for clinical treatment of bacterial infection due to the broad-spectrum and highly effective antibacterial activity. However, the easy degradation and inactivation in vivo has been a major obstacle for their application and an effective delivery system is demanding. The surface physicochemical properties of the carrier, including surface potential, surface polarity, pore structure and morphology, have exerted great effects on the adsorption and release behavior of AMPs. This study investigated the influence of micro/nano carriers with different hierarchical structures on the loading, release and biological behavior of AMPs. Three types of AMPs-loaded hydroxyapatite microspheres (HA/AMPs MSs) with different hierarchical structures (needle-like, rod-like, and flake-like) were developed, which was investigated by the surface morphology, chemical composition and surface potential in detail. The different hierarchical structures of hydroxyapatite microspheres (HA MSs) had noticeable impact on the loading and release behavior of AMPs, and the flake-like HA MSs with hierarchical structure showed the highest loading efficiency and long-lasting release over 9 days. Meanwhile, the stability of AMPs released from HA MSs was effectively maintained. Moreover, the antibacterial test indicated that the flake-like HA/AMPs MSs showed more sustained antibacterial properties among three composites. In view of the excellent biocompatibility and osteogenic property, high loading efficiency and the long-term release properties of HA MSs with hierarchical structure, the HA/AMPs MSs have a great potential in bone tissue engineering.

Improved activity of MC3T3-E1 cells by the exciting piezoelectric BaTiO3/TC4 using low-intensity pulsed ultrasound

Developing bioactive materials for bone implants to enhance bone healing and bone growth has for years been the focus of clinical research. Barium titanate (BT) is an electroactive material that can generate electrical signals in response to applied mechanical forces. In this study, a BT piezoelectric ceramic coating was synthesized on the surface of a TC4 titanium alloy, forming a BT/TC4 material, and low-intensity pulsed ultrasound (LIPUS) was then applied as a mechanical stimulus. The combined effects on the biological responses of MC3T3-E1 cells were investigated. Results of scanning electron microscopy, energy-dispersive X-ray spectroscopy, and X-ray diffraction showed that an uniform nanospheres -shaped BT coating was formed on TC4 substrate. Piezoelectric behaviors were observed using piezoelectric force microscopy with the piezoelectric coefficient d33 of 0.42 pC/N. Electrochemical measures indicated that LIPUS-stimulated BT/TC4 materials could produce a microcurrent of approximately 10 μA/cm2. In vitro, the greatest osteogenesis (cell adhesion, proliferation, and osteogenic differentiation) was found in MC3T3-E1 cells when BT/TC4 was stimulated using LIPUS. Furthermore, the intracellular calcium ion concentration increased in these cells, possibly because opening of the L-type calcium ion channels was promoted and expression of the CaV1.2 protein was increased. Therefore, the piezoelectric BT/TC4 material with LIPUS loading synergistically promoted osteogenesis, rending it a potential treatment for early stage formation of reliable bone-implant contact.

3D Printed Multifunctional Ti6Al4V-Based Hybrid Scaffold for the Management of Osteosarcoma

Osteosarcoma is a challenging bone disease which is commonly associated with critically sized bone defects and cancer recurrence. Here, we designed and developed a multifunctional, hierarchical structured bone scaffold which can meet the demanding requirements for osteosarcoma management. The 3D printed Ti6Al4V scaffold with hydrothermally induced TiO2/TiP coating can offer a unique photothermal conversion property for in vitro bone cancer ablation. The scaffold is also infused with drug-laden gelatin/hydroxyapatite nanocomposite, which provides the ideal porous structure for cell adhesion/bone ingrowth and promotes bone regeneration. The scaffold has been thoroughly characterized by SEM/EDX, TEM, XPS, XRD, TGA, and UV-vis, and its in vitro bone cancer ablation efficiency has been validated using MG-63 cells. The hybrid scaffold showed excellent biocompatibility, and its osteointegration function has been demonstrated using an animal model.

Boron-incorporated micro/nano-topographical calcium silicate coating dictates osteo/angio-genesis and inflammatory response toward enhanced osseointegration

Orthopedic implant coatings with optimal surface features to achieve favorable osteo/angio-genesis and inflammatory response would be of great importance. However, to date, few coatings are capable of fully satisfying these requirements. In this work, to take advantage of the structural complexity of micro/nano-topography and benefits of biological trace elements, two types of boron-containing nanostructures (nanoflakes and nanolamellars) were introduced onto plasma-sprayed calcium silicate (F-BCS and L-BCS) coatings via hydrothermal treatment. The C-CS coating using deionized water as hydrothermal medium served as control. Boron-incorporated CS coating stimulated osteoblastic differentiation of bone marrow-derived mesenchymal stem cells (BMSCs). Specifically, the combination of β1 integrin-vinculin-mediated cell spreading and activation of bone morphogenetic protein signaling pathway acted synergistically to cause significant upregulation of runt-related transcription factor 2 (RUNX2) protein and Runx2 gene expression in BMSCs on the F-BCS coating surface, which induced the transcription of downstream osteogenic differentiation marker genes. F-BCS coating allowed specific boron ion release, which favored angiogenesis as evidenced by the enhanced migration and tube formation of human umbilical vein endothelial cells in the coating extract. Boron-incorporated coatings significantly suppressed the expression of toll-like receptor adaptor genes in RAW264.7 macrophages and subsequently the degradation of nuclear factor-κB inhibitor α, accompanied by the inactivation of the downstream pro-inflammatory genes. In vivo experiments confirmed that F-BCS-coated Ti implant possessed enhanced osseointegration compared with L-BCS- and C-CS-coated implants. These data highlighted the synergistic effect of specific nanotopography and boron release from orthopedic implant coating on improvement of osseointegration.

Modification of polyetheretherketone implants: From enhancing bone integration to enabling multi-modal therapeutics

Polyetheretherketone (PEEK) is a popular thermoplastic material widely used in engineering applications due to its favorable mechanical properties and stability at high temperatures. With the first implantable grade PEEK being commercialized in 1990s, the use of PEEK has since grown exponentially in the biomedical field and has rapidly transformed a large section of the medical devices landscape. Nowadays, PEEK is a standard biomaterial used across a wide range of implant applications, however, its bioinertness remains a limitation for bone repair applications. The increasing demand for enhanced treatment efficacy/improved patient quality of life, calls for next-generation implants that can offer fast bone integration as well as other desirable therapeutic functions. As such, modification of PEEK implants has progressively shifted from offering desirable mechanical properties, enhancing bioactivity/fast osteointegration, to more recently, tackling post-surgery bacterial infection/biofilm formation, modulation of inflammation and management of bone cancers. Such progress is also accompanied by the evolution of the PEEK manufacturing technologies, to meet the ever increasing demand for more patient specific devices. However, no review has comprehensively covered the recently engaged application areas to date. This paper provides an up-to-date review on the development of PEEK-based biomedical devices in the past 10 years, with particularly focus on modifying PEEK for multi-modal therapeutics. The aim is to provide the peers with a timely update, which may guide and inspire the research and development of next generation PEEK-based healthcare products. STATEMENT OF SIGNIFICANCE: Significant progress has been made in PEEK processing and modification techniques in the past decades, which greatly contributed to its wide applications in the biomedical field. Despite the high volume of published literature on PEEK implant related research, there is a lack of review on its emerging applications in multi-modal therapeutics, which involve bone regeneration, anti-bacteria/anti-inflammation, and cancer inhibition, etc. This timely review covers the state-of-the-art in these exciting areas and provides the important guidance for next generation PEEK based biomedical device research and development.

Layered Double Hydroxide Modified Bone Cement Promoting Osseointegration via Multiple Osteogenic Signal Pathways

Poly(methyl methacrylate) (PMMA) bone cement has been widely used in orthopedic surgeries including total hip/knee replacement, vertebral compression fracture treatment, and bone defect filling. However, aseptic loosening of the interface between PMMA bone cement and bone often leads to failure. Hence, the development of modified PMMA that facilitates the growth of bone into the modified PMMA bone cement is key to reducing the incidence of aseptic loosening. In this study, MgAl-layered double hydroxide (LDH) microsheets modified PMMA (PMMA&LDH) bone cement with superior osseointegration performance has been synthesized. The maximum polymerization reaction temperature of PMMA&LDH decreased by 7.0 and 11.8 °C, respectively, compared with that of PMMA and PMMA&COL-I (mineralized collagen I modified PMMA). The mechanical performance of PMMA&LDH decreased slightly in comparison with PMMA, which is beneficial to alleviate stress-shielding osteolysis, and indirectly promote osseointegration. The superior osteogenic ability of PMMA&LDH has been demonstrated in vivo, which boosts bone growth by 2.17- and 18.34-fold increments compared to the PMMA&COL-I and PMMA groups at 2 months, postoperatively. Moreover, transcriptome sequencing revealed four key osteogenic pathways: p38 MAPK, ERK/MAPK, FGF, and TGF-β, which were further confirmed by IPA, qPCR, and Western blot assays. Hence, LDH-modified PMMA bone cement is a promising biomaterial to enhance bone growth with potential applications in relevant orthopedic surgeries.

Ag- and Sr-enriched nanofibrous titanium phosphate phases as potential antimicrobial cement and coating for a biomedical alloy

Biomaterials and their surfaces regulate the biological response and ultimately the quality of healing at a possible site of implantation. The physical, chemical and topographical properties of implants' surfaces play a decisive role in the biological integration process for their immediate loading and long-term success. Since at this level of biological interaction nano-dimensionality is basically entailed, bio-functional nanostructured composites either as filling/cement or coating to metallic implants are required. This study shows the possibility of synthesizing two phases of nanostructured titanium phosphate (π and ρ polymorphs) and enriching them with silver nanoparticles and strontium. More importantly, Ag-Sr-enriched nanostructured π‑titanium phosphate is induced to grow on a commercially available titanium alloy (Ti-6Al-4V), widely used in orthopedic and dental implants, under highly controlled conditions. Structural and microscopic studies, using XRD, HRTEM and SEM altogether confirm the resultant phases and their enrichment with strontium and silver nanoparticles with an average particle size around 6 nm. Using confocal laser scanning microscopy, the surface roughness was measured and is found to lay at the interface between the nanosized and microsized topologies. Ion release assessments showed that the presence of strontium controlled the release rate of silver ions and this could be beneficial in terms of decreasing the accompanied cytotoxicity that is usually encountered at high concentrations of silver release. Antimicrobial and cell proliferation assays have proved that enriching titanium phosphate with strontium and silver nanoparticles has improved their antimicrobial properties, while the cytotoxicity could be controlled.

Nanotube-decorated hierarchical tantalum scaffold promoted early osseointegration

This study aimed to fabricate a hierarchical tantalum scaffold mimicking natural bone structure to enhance osseointegration. Porous tantalum scaffolds (p-Ta) with microgradients were fabricated by selective laser melting according to a computer-aided design model. Electrochemical anodization produced nanotubes on the p-Ta surface (p-Ta-nt). SEM verified the construction of a unique nanostructure on p-Ta-nt. Contact angle and protein adsorption measurements demonstrated that p-Ta-nt have enhanced hydrophilicity and protein absorption. MC3T3-E1 preosteoblasts showed increased filamentous pseudopods and comparable cell proliferation when cultured on p-Ta-nt. Osteogenic marker gene (Osterix, Runx2, COL-I) transcription was significantly upregulated in MC3T3-E1 cells cultured on p-Ta-nt after 7 days. After implantation into the femurs of New Zealand white rabbits for 2 weeks, histological examination found improved early osseointegration in the p-Ta-nt group. This study showed that a hierarchical tantalum structure could enhance early osteogenic effects in vitro and in vivo.

Injectable open-porous PLGA microspheres as cell carriers for cartilage regeneration

Minimally invasive treatment via injectable delivery of cells has drawn extensive attention for tissue regeneration because it reduces the need for substantial open surgery and fits tissue defects with complex shapes, making it a suitable option for repairing articular cartilage defects. This work presents an alkaline treatment method to fabricate open-porous poly (lactic-co-glycolic acid) microspheres (OPMs) as bone marrow stromal cells (BMSCs) carriers for cartilage regeneration. OPMs have better biodegradation property and the extended pores can provide easier access for cells to the internal space. The BMSCs cultured with OPMs can display enhanced cell proliferation, up-regulated expression of cartilage-related mRNAs and proteins, and improved cartilage regeneration in vitro and in vivo. These results highlight the advantage and potential of using OPMs fabricated via simple alkaline treatment as injectable stem cell carriers for cartilage regeneration through minimally invasive procedures.

Titanium and Protein Adsorption: An Overview of Mechanisms and Effects of Surface Features

Titanium and its alloys, specially Ti6Al4V, are among the most employed materials in orthopedic and dental implants. Cells response and osseointegration of implant devices are strongly dependent on the body-biomaterial interface zone. This interface is mainly defined by proteins: They adsorb immediately after implantation from blood and biological fluids, forming a layer on implant surfaces. Therefore, it is of utmost importance to understand which features of biomaterials surfaces influence formation of the protein layer and how to guide it. In this paper, relevant literature of the last 15 years about protein adsorption on titanium-based materials is reviewed. How the surface characteristics affect protein adsorption is investigated, aiming to provide an as comprehensive a picture as possible of adsorption mechanisms and type of chemical bonding with the surface, as well as of the characterization techniques effectively applied to model and real implant surfaces. Surface free energy, charge, microroughness, and hydroxylation degree have been found to be the main surface parameters to affect the amount of adsorbed proteins. On the other hand, the conformation of adsorbed proteins is mainly dictated by the protein structure, surface topography at the nano-scale, and exposed functional groups. Protein adsorption on titanium surfaces still needs further clarification, in particular concerning adsorption from complex protein solutions. In addition, characterization techniques to investigate and compare the different aspects of protein adsorption on different surfaces (in terms of roughness and chemistry) shall be developed.

An alternative ex vivo method to evaluate the osseointegration of Ti-6Al-4V alloy also combined with collagen

Due to the increasing number of orthopedic implantation surgery and advancements in biomaterial manufacturing, chemistry and topography, there is an increasing need of reliable and rapid methods for the preclinical investigation of osseointegration and bone ingrowth. Implant surface composition and topography increase osteogenicity, osteoinductivity, osteoconductivity and osseointegration of a prosthesis. Among the biomaterials used to manufacture an orthopedic prosthesis, titanium alloy (Ti-6Al-4V) is the most used. Type I collagen (COLL I) induces cell function, adhesion, differentiation and bone extracellular matrix component secretion and it is reported to improve osseointegration if immobilized on the alloy surface. The aim of the present study was to evaluate the feasibility of an alternative ex vivo model, developed by culturing rabbit cortical bone segments with Ti-6Al-4V alloy cylinders (Ti-POR), fabricated through the process of electron beam melting (EBM), to evaluate osseointegration. In addition, a comparison was made with Ti-POR coated with COLL I (Ti-POR-COLL) to evaluate osseointegration in terms of bone-to-implant contact (BIC) and new bone formation (nBAr/TAr) at 30, 60 and 90 d of culture. After 30 and 60 d of culture, BIC and nBAr/TAr resulted significantly higher in Ti-POR-COLL implants than in Ti-POR. No differences have been found at 90 d of culture. With the developed model it was possible to distinguish the biomaterial properties and behavior. This study defined and confirmed for the first time the validity of the alternative ex vivo method to evaluate osseointegration and that COLL I improves osseointegration and bone growth of Ti-6Al-4V fabricated through EBM.

Pro-osteogenesis and in vivo tracking investigation of a dental implantation system comprising novel mTi implant and HYH-Fe particles

Insufficient early osteogenesis seriously affects the later stage osteogenic quality and osseointegration of dental implants. To promote early osteogenesis, we first designed a Ti dental implant with a built-in magnet (mTi) to produce a local static magnetic field (SMF). Then, a dental implantation system comprising the mTi implant and the superparamagnetic hydroxyapatite (HA:Yb/Ho-Fe, named HYH-Fe) particles was implanted into the alveolar bone of beagles. The results showed that the mTi + HYH-Fe group displayed better early osteogenesis and later stage osseointegration than the Ti + HA and mTi + HA groups. A combination of the local SMF (mTi) and superparamagnetic HYH-Fe particles had a positive effect on the pro-osteogenesis of Ti implants. The results also indicated that week 10 could be adopted as the key time point to evaluate the early osteogenic effect of the mTi + HYH-Fe implantation system, which would be a promising prospect for promotion of osteogenesis, in vivo tracking investigation of material-bone relationships, and clinical applications.

Tannic acid/Mg2+-based versatile coating to manipulate the osteoimmunomodulation of implants

Instead of directly stimulating osteogenesis, endowing an implant surface with a favourable osteoimmunomodulatory (OIM) function has emerged as a new effective strategy to enhance osteointegration. Though metal-phenolic coatings have demonstrated to possess an immunomodulatory function, their potential application in manipulating an osteoimmune response has not been well explored. Herein, in order to develop a simple, rapid and universal coating method to impart excellent OIM to hard tissue implants, tannic acid (TA) and Mg²⁺ were selected to form a coating on Ti plate based on metal-phenolic chemistry. Besides its virtues of simplicity, ultrafastness, low-cost, and versatility, another merit for the coating method is that it can easily combine the unique functions of metal ions and phenolic ligands. The chelated Mg²⁺ can not only activate macrophage polarization towards the anti-inflammatory phenotype but also directly stimulate the osteogenic differentiation of bone marrow-derived stem cells (BMSCs). TA motifs rendered the coating with an excellent reactive oxygen species (ROS) scavenging capacity. TA and Mg²⁺ showed synergistic effects on regulating macrophage biological behaviour, suppressing its polarization towards the M1 phenotype, and promoting its polarization towards the M2 phenotype. In vivo histological analysis also demonstrated that the TA/Mg²⁺ coating could effectively inhibit the host response. Finally, the formed osteoimmune environment obviously enhanced the osteogenic differentiation of BMSCs. The above results demonstrated that the designed TA/Mg²⁺ coating not only possessed the function of directly stimulating osteogenesis but also the function of manipulating OIM to a desired one. Hence, it has great potential to be applied on advanced hard tissue implants to enhance osteointegration.

In vitro evaluation of electrochemically bioactivated Ti6Al4V 3D porous scaffolds

Triply periodic minimal surfaces (TPMS) are known for their advanced mechanical properties and are wrinkle-free with a smooth local topology. These surfaces provide suitable conditions for cell attachment and proliferation. In this study, the in vitro osteoinductive and antibacterial properties of scaffolds with different minimal pore diameters and architectures were investigated. For the first time, scaffolds with TPMS architecture were treated electrochemically by plasma electrolytic oxidation (PEO) with and without silver nanoparticles (AgNPs) to enhance the surface bioactivity. It was found that the scaffold architecture had a greater impact on the osteoblast cell activity than the pore size. Through control of the architecture type, the collagen production by osteoblast cells increased by 18.9% and by 43.0% in the case of additional surface PEO bioactivation. The manufactured scaffolds demonstrated an extremely low quasi-elastic modulus (comparable with trabecular and cortical bone), which was 5-10 times lower than that of bulk titanium (6.4-11.4 GPa vs 100-105 GPa). The AgNPs provided antibacterial properties against both gram-positive and gram-negative bacteria and had no significant impact on the osteoblast cell growth. Complex experimental results show the in vitro effectiveness of the PEO-modified TPMS architecture, which could positively impact the clinical applications of porous bioactive implants.

Novel Bionic Topography with MiR-21 Coating for Improving Bone-Implant Integration through Regulating Cell Adhesion and Angiogenesis

Implant loosening is still the major form of the failure of artificial joints. Herein, inspired by the operculum of the river snail, we prepared a novel bionic micro/nanoscale topography on a titanium surface. This bionic topography promoted early cell adhesion through up-regulating the expression of ITG α5β1 and thus accelerated the following cell spreading, proliferation, and differentiation. Moreover, a miR-21 coating, which promoted the angiogenic differentiation of MSCs, was fabricated on the bionic topography. Benefiting from both bionic micro/nanoscale topography and miR-21, blood vessel growth and bone formation and mineralization around the implant, as well as bone-implant bonding strength, were significantly improved. Collectively, the present study highlights the combination of the bionic micro/nanoscale topography and miR-21 on promoting cell adhesion and angiogenic differentiation and improving in vivo angiogenesis and bone-implant osseointegration. This work provides a new train of thought propelling the development of implants for potential application in the orthopedics field.

Activation of Nell-1 in BMSC Sheet Promotes Implant Osseointegration Through Regulating Runx2/Osterix Axis

Neural epidermal growth factor-like 1 protein (Nell-1) is first studied because of its association with human craniosynostosis. Nell-1 has been used to accelerate the process of fracture healing because of the osteoinductive ability in recent years. However, the role of Nell-1 during the process of osteointegration is unknown. Here we show that activation of Nell-1 in the BMSC sheet promotes osseointegration in vivo and in vitro. We found that overexpression of Nell-1 improved osteogenic differentiation and enhanced matrix mineralization of BMSCs through increasing expression of Runx2 and Osterix. Activation of Nell-1 up-regulated the expression ratio of OPG/RANKL, which might have a negative influence on osteoclast differentiation. Furthermore, we obtained BMSC sheet-implant complexes transfected with lentivirus overexpressing and interfering Nell-1 in in vivo study, and confirmed that overexpression of Nell-1 promoted new bone formation around the implant and increased the bone-implant contacting area percentage. Our results demonstrate that activation of Nell-1 improves implant osteointegration by regulating Runx2/Osterix axis and shows the potential of BMSC sheet-implant complexes in gene therapy.

Approaches to promoting bone marrow mesenchymal stem cell osteogenesis on orthopedic implant surface

Bone marrow-derived mesenchymal stem cells (BMSCs) play a critical role in the osseointegration of bone and orthopedic implant. However, osseointegration between the Ti-based implants and the surrounding bone tissue must be improved due to titanium’s inherent defects. Surface modification stands out as a versatile technique to create instructive biomaterials that can actively direct stem cell fate. Here, we summarize the current approaches to promoting BMSC osteogenesis on the surface of titanium and its alloys. We will highlight the utilization of the unique properties of titanium and its alloys in promoting tissue regeneration, and discuss recent advances in understanding their role in regenerative medicine. We aim to provide a systematic and comprehensive review of approaches to promoting BMSC osteogenesis on the orthopedic implant surface.

Characterization of the in Vitro Osteogenic Response to Submicron TiO2 Particles of Varying Structure and Crystallinity

Titanium oxide (TiO2) nano-/microparticles have been widely used in orthopedic and dental sciences because of their excellent mechanical properties, chemical stability, and ability to promote the osseointegration of implants. However, how the structure and crystallinity of TiO2 particles may affect their osteogenic activity remains elusive. Herein, we evaluated the osteogenic response to submicron amorphous, anatase, and rutile TiO2 particles with controlled size and morphology. First, the ability of TiO2 particles to precipitate apatite was assessed in an acellular medium by using a simulated body fluid (SBF). Three days after the addition to SBF, anatase and rutile TiO2 particles induced the precipitation of aggregates of nanoparticles with a platelike morphology, typical for biomimetic apatite. Conversely, amorphous TiO2 particles induced the precipitation of particles with poor Ca/P atomic ratio only after 14 days of exposure to SBF. Next, the osteogenic response to TiO2 particles was assessed in vitro by incubating MC3T3-E1 preosteoblasts with the particles. The viability and mineralization efficiency of osteoblastic cells were maintained in the presence of all the tested TiO2 particles despite the differences in the induction of apatite precipitation in SBF by TiO2 particles with different structures. Analysis of the particles' surface charge and of the proteins adsorbed onto the particles from the culture media suggested that all the tested TiO2 particles acquired a similar biological identity in the culture media. We posited that this phenomenon attenuated potential differences in osteoblast response to amorphous, anatase, and rutile particles. Our study provides an important insight into the complex relationship between the physicochemical properties and function of TiO2 particles and sheds light on their safe use in medicine.

Tremella-Like ZnO@Col-I-Decorated Titanium Surfaces with Dual-Light-Defined Broad-Spectrum Antibacterial and Triple Osteogenic Properties

The growing population of peri-implant diseases (PIDs) has become a public obsession, mainly due to the lack of antibacterial ability and osteogenic promotion of titanium (Ti) implants. Herein, inspired by tremella, we reported zinc oxide (ZnO)@collagen type I (Col-I)-decorated Ti for PIDs treatments. Compared with pure Ti implants, ZnO@Col-I-decorated Ti could be activated by a safe visible yellow light and showed excellent broad-spectrum antibacterial properties. The proliferation and osteogenic gene expression of bone marrow mesenchymal stem cells (BMSCs) indicated that the triple osseointegration of implants was realized through (I) the remarkedly improved surface hydrophilicity of ZnO@Col-I-decorated Ti, (II) the function of Col-I, and (III) the excellent near-infrared (NIR)-induced photothermal performance of ZnO. Collectively, the proposed dual-light-defined ZnO@Col-I coating was a promising implant surface modification system to provide customized treatments for each PID patient.

Tailorable hierarchical structures of biomimetic hydroxyapatite micro/nano particles promoting endocytosis and osteogenic differentiation of stem cells

Hydroxyapatite (HA) micro/nano particles show great promise as artificial bone and dental substitutes, or drug carrier systems. However, the precise regulation of hydroxyapatite micro/nano particles with controllable physicochemical properties (such as hierarchical structure, particle size, potential and crystallinity) is still a challenge. Furthermore, the effects of different hierarchical structures on biological responses have been rarely reported. Herein, the HA particles with a precisely tailored micro/nano hierarchical structure have been developed using an elaborate biomimetic synthesis technology. Three representative particles, namely, micro/nano needle-like HA particles, micro/nano rod-like HA particles, and micro/nano flake-like HA particles, were featured to evaluate their biological responses to stem cells. The pore structure facilitated the adsorption of serum adhesive proteins, which together with the unique hierarchical architecture of micro/nano flake-like HA particles remarkably promoted the endocytosis efficiency in a concentration-dependent manner. The qRT-PCR together with RNA-seq and western blot analyses showed that micro/nano flake-like HA particles more significantly up-regulated the expression of genes and production of proteins related to osteogenic differentiation among the three particles through the activated ERK/MAPK signalling pathway. RNA-seq further revealed a complex mechanism of cell interface events, suggesting that the hierarchical architecture of HA particles is of crucial importance for the regulation of actin cytoskeleton involved in the modulation of cell adhesion which positively stimulated osteogenic differentiation of stem cells. Moreover, the endocytosis of particles into lysosomes resulted in an increase in the intracellular Ca²⁺ levels, which activated possible intracellular Ca²⁺-mediated signaling cascades (Ras/cAMP/Rap1/MAPK signaling pathways) related to osteogenic differentiation of stem cells. Our findings shed light on the effects of different hierarchical structures of HA particles on stem cell differentiation and contribute to the optimal design of implant materials.

Antibacterial and hydroxyapatite-forming coating for biomedical implants based on polypeptide-functionalized titania nanospikes

Titanium (Ti)-based implants often suffer from detrimental bacterial adhesion and inefficient healing, so it is crucial to design a dual-functional coating that prevents bacterial infection and enhances bioactivity for a successful implant. Herein, we successfully devised a cationic polypeptide (Pep)-functionalized biomimetic nanostructure coating with superior activity, which could not only kill pathogenic bacteria rapidly and inhibit biofilm formation for up to two weeks, but also promote in situ hydroxyapatite (HAp) formation. Specifically, a titania (TiO2) nanospike coating (TNC) was fabricated by alkaline hydrothermal treatment firstly, followed by immobilization of rationally synthesized Pep via robust coordinative interactions, named TNPC. This coating was able to effectively kill (>99.9%) both Gram-positive Staphylococcus aureus (S. aureus) and Gram-negative Escherichia coli (E. coli) bacteria, while being non-toxic to murine MC3T3-E1 osteoblastic cells. Furthermore, the in vivo infection studies denoted that the adherent bacteria numbers on the TNPC implants were significantly reduced by 6 orders of magnitude than those on the pure Ti implants (p < 0.001). Importantly, in the presence of cationic amino groups and residual Ti-OH groups, substantial HAp deposition on the TNPC surface in Kokubo's simulated body fluid (SBF) occurred after 14 days. Altogether, our results support the clinical potential of this biomimetic dual-functional coating as a new approach with desirable antibacterial properties and HAp-forming ability in orthopedic and dental applications.

Precision Medicine in Tissue Engineering on Bone

With the rapidly development of clinical treatments, precision medicine has come to people eyes with the requirement according to different people and different disease situation. So precision medicine is called personalized medicine which is a new frontier of healthcare. Bone tissue engineering developed from traditional bone graft to precise medicine era. So scientists seek approaches to harness stem cells, scaffolds, growth factors, and extracellular matrix to promise enhanced and more reliable bone formation. This review provides an overview of novel developments on precision medicine in tissue engineering of bone hoping it can open new perspectives of strategies on bone treatment.

Modulation of the mechanosensing of mesenchymal stem cells by laser-induced patterning for the acceleration of tissue reconstruction through the Wnt/β-catenin signaling pathway activation

Growing evidence suggests that the physical microenvironment can guide cell fate. However, cells sense cues from the adjacent physical microenvironment over a limited distance. In the present study, murine mesenchymal stem cells (MSCs) and murine preosteoblastic cells (MC3T3-E1) behaviors are regulated by the cell-material interface using ordered-micro and disordered-nano patterned structures on Ti implants. The optimal bone formation structure is a stable wave (horizontal direction: ridge, 2.7 µm; grooves, 5.3 µm; and vertical direction: distance, 700 µm) with the appropriate density of nano-branches (6.0 per µm²). The repeated waves provide cells with directional guidance, and the disordered branches influence cell geometry by providing different spacing and density nanostructure. And micro-nano patterned structure can provide biophysical cues to direct cell phenotype development, including cell size, shape, and orientation, to influence cellular processes including survival, growth, and differentiation. Thus, the overlaid isotropic and anisotropic cues, ordered-micro and disordered-nano patterned structures, could transfer further and alter cell shape and induce nuclear orientation by activating Wnt/β-catenin signaling to promote integrin α5, integrin β1, cadherin 2, Runx2, Opn, and Ocn. That canonical Wnt signaling inhibitor dickkopf1 further demonstrates osteogenic differentiation induced by ordered-micro and disordered-nano patterned structures, which is related to Wnt/β-catenin signaling. Our findings show the role of ordered microstructures and disordered nanostructures in modulating stem cell differentiation with potential medical applications. STATEMENT OF SIGNIFICANCE: It remains a challenge to modify poor osteogenic and osteoconductive properties of titanium alloy bases on the inherent poverty of titanium. We demonstrate that ordered microtopography and disordered nano topography pattern structure could lead to osteogenic differentiation in vitro and bone regeneration in vivo. Furthermore, the pattern structure is created through selective laser melting and alkali heat. And the structure only takes advantage of titanium itself and does not bring in active film, such as hydroxyapatite. On the other hand, we find that cell shape and orientation show angle-orientation tendency due to the polarity, which involves with mechanical signal created via patterned structure. Meanwhile, the Wnt/Ca²⁺ signaling pathway is activated.