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

Integrating molecular-caged nano-hydroxyapatite into post-crosslinked PVA nanofibers for artificial periosteum

Artificial periosteum is deemed a novel strategy for inducing endogenous bone regeneration, but ideal periosteum substitutes achieved by orchestrating a biomimetic microenvironment for bone regeneration remain a significant challenge. Here, we design and fabricate a hybridized nanofiber-based artificial periosteum with boosted osteoinduction properties. Via a "molecular cage" biomineralization strategy, nano-hydroxyapatite (nano-HAp) with a controllable size (∼22 nm) and excellent dispersion serves as unique nano-additives for water-soluble polyvinyl-alcohol (PVA)-based artificial periosteum. The PVA/HAp composite is electrospun into nanofibers to replicate the extracellular-matrix-inspired nanostructure for inducing cell adhesion, proliferation, and fate manipulation. A simple post-crosslinking treatment is subsequently applied to further booster its mechanical strength (6.6 MPa) and swelling stability. The optimized sample of C-PVA/HAp (10 wt% nano-HAp) artificial periosteum features excellent biocompatibility and remarkable in vitro mineralization. Cell experiments demonstrate that its effectively boasted cell modulation for enhanced osteogenesis without the aid of growth factors, showing a possible activation of the ERK/MAPK signaling pathway. This work provides an effective strategy for designing novel HAp nano-additives and expands the possibility of biomimetic fabrication for more advanced nanofiber-based artificial periosteum.

Dual role of Sfrp4 in bone remodelling during orthodontic tooth movement

OBJECTIVES

The objective of this study was to determine changes in gene expression by establishing an orthodontic tooth movement (OTM) rat model with appropriate and excessive orthodontic force.

MATERIALS AND METHODS

Using a closed coil nickel-titanium spring, the OTM was carried out to apply a mesial force of 50 or 100 g to the maxillary first molars. Micro-CT, histological and immunohistochemical staining were used to evaluate the bone formation at the tension site and the bone resorption and bone formation at pressure site. Then RNA sequencing and bioinformatic analysis were performed.

RESULTS

According to the results of the Mirco-CT scan of OTM rat models, both the 50 g group and the 100 g group showed variable degrees of reduction in alveolar bone density on the tension and pressure sides. The results of histological and immunohistochemical staining demonstrated that the periodontal tissue and osteogenic ability of the 50 g group were restored at the 14 days, while the 100 g group caused severe periodontal tissue damage. The GO and KEGG analysis results, as well as the number of differentially expressed genes (DEGs), varied depending on the loading time and value of appliance, according to the results of the RNA sequencing. And the immunohistochemical staining results showed that Sfrp4 functioned by efficiently influencing both bone formation and bone absorption.

CONCLUSIONS

Appropriate orthodontic force value could cause appropriate movement of teeth in rats without adverse periodontal damage. Simultaneously, distinct gene expression patterns were observed at various force levels and time intervals.

Hybrid Hydroxyapatite-Metal Complex Materials Derived from Amino Acids and Nucleobases

Calcium phosphates (CaPs) and their substituted derivatives encompass a large number of compounds with a vast presence in nature that have aroused a great interest for decades. In particular, hydroxyapatite (HAp, Ca10(OH)2(PO4)6) is the most abundant CaP mineral and is significant in the biological world, at least in part due to being a major compound in bones and teeth. HAp exhibits excellent properties, such as safety, stability, hardness, biocompatibility, and osteoconductivity, among others. Even some of its drawbacks, such as its fragility, can be redirected thanks to another essential feature: its great versatility. This is based on the compound's tendency to undergo substitutions of its constituent ions and to incorporate or anchor new molecules on its surface and pores. Thus, its affinity for biomolecules makes it an optimal compound for multiple applications, mainly, but not only, in biological and biomedical fields. The present review provides a chemical and structural context to explain the affinity of HAp for biomolecules such as proteins and nucleic acids to generate hybrid materials. A size-dependent criterium of increasing complexity is applied, ranging from amino acids/nucleobases to the corresponding macromolecules. The incorporation of metal ions or metal complexes into these functionalized compounds is also discussed.

Dual Factor-Loaded Artificial Periosteum Accelerates Bone Regeneration

In the clinic, inactivation of osteosarcoma using microwave ablation would damage the periosteum, resulting in frequent postoperative complications. Therefore, the development of an artificial periosteum is crucial for postoperative healing. In this study, we prepared an artificial periosteum using silk fibroin (SF) loaded with stromal cell-derived factor-1α (SDF-1α) and calcitonin gene-related peptide (CGRP) to accelerate bone remodeling after the microwave ablation of osteosarcoma. The prepared artificial periosteum showed a sustained release of SDF-1α and CGRP after 14 days of immersion. In vitro culture of rat periosteal stem cells (rPDSCs) demonstrated that the artificial periosteum is favorable for cell recruitment, the activity of alkaline phosphatase, and bone-related gene expression. Furthermore, the artificial periosteum improved the tube formation and angiogenesis-related gene expression of human umbilical vein endothelial cells (HUVECs). In an animal study, the periosteum in the femur of a rabbit was inactivated through microwave ablation and then removed. The damaged periosteum was replaced with the as-prepared artificial periosteum and favored bone regeneration. In all, the designed dual-factor-loaded artificial periosteum is a promising strategy to replace the damaged periosteum in the therapy of osteosarcoma for a better bone-rebuilding process.

3D stem cell spheroids with urchin-like hydroxyapatite microparticles enhance osteogenesis of stem cells

Cell therapy (also known as cell transplantation) has been considered promising as a next-generation living-cell therapy strategy to surpass the effects of traditional drugs. However, their practical clinical uses and product conversion are hampered by the unsatisfied viability and efficacy of the transplanted cells. Herein, we propose a synergistic enhancement strategy to address these issues by constructing 3D stem cell spheroids integrated with urchin-like hydroxyapatite microparticles (uHA). Specifically, cell-sized uHA microparticles were synthesized via a simple hydrothermal method using glutamic acid (Glu, E) as the co-template with good biocompatibility and structural antimicrobial performance (denoted as E-uHA). Combining with a hanging drop method, stem cell spheroids integrated with E-uHA were successfully obtained by culturing bone marrow mesenchymal stem cells (BMSCs) with a low concentration of the E-uHA suspensions (10 μg mL-1). The resulting composite spheroids of BMSCs/E-uHA deliver a high cellular viability, migration activity, and a superior osteogenic property compared to the 2D cultured counterpart or other BMSC spheroids. This work provides an effective strategy for integrating a secondary bio-functional component into stem cell spheroids for designing more cell therapy options with boosted cellular viability and therapeutic effect.

Research advances of nanomaterials for the acceleration of fracture healing

The bone fracture cases have been increasing yearly, accompanied by the increased number of patients experiencing non-union or delayed union after their bone fracture. Although clinical materials facilitate fracture healing (e.g., metallic and composite materials), they cannot fulfill the requirements due to the slow degradation rate, limited osteogenic activity, inadequate osseointegration ability, and suboptimal mechanical properties. Since early 2000, nanomaterials successfully mimic the nanoscale features of bones and offer unique properties, receiving extensive attention. This paper reviews the achievements of nanomaterials in treating bone fracture (e.g., the intrinsic properties of nanomaterials, nanomaterials for bone defect filling, and nanoscale drug delivery systems in treating fracture delayed union). Furthermore, we discuss the perspectives on the challenges and future directions of developing nanomaterials to accelerate fracture healing.

Microwave-assisted synthesis of composites based on titanium and hydroxyapatite for dental implantation

Titanium (Ti) and its alloys are widely used in clinical practice. As they are not bioactive, hydroxyapatite (HA) is commonly used to modify them. This study offered a review of microwave-assisted synthesis of composites based on Ti and HA for dental implantation by exploring their interaction mechanisms with microwave and features of two main techniques, namely microwave coating and sintering, along with current challenges and potential solutions in the field. It was shown that microwave coating enables rapid deposition of HA, but suffers from problems such as uneven coating thickness, poor integrity and unstable composition of the products. They can be solved by creating interlayers, combining the spin coating technique, etc. Unlike microwave coating, microwave sintering can effectively modify the mechanical properties of the composites, despite the shortcomings of excessive elastic moduli and potential HA decomposition. These issues are expected to be addressed by adding alloying elements and employing appropriate materials as space holders and ion-doped HA for sintering.

Hyaluronic acid-mediated collagen intrafibrillar mineralization and enhancement of dentin remineralization

Non-collagenous proteins (NCPs) in the extracellular matrix (ECM) of bone and dentin are known to play a critical regulatory role in the induction of collagen fibril mineralization and are embedded in hyaluronic acid (HA), which acts as a water-retaining glycosaminoglycan and provides necessary biochemical and biomechanical cues. Our previous study demonstrated that HA could regulate the mineralization degree and mechanical properties of collagen fibrils, yet its kinetics dynamic mechanism on mineralization is under debate. Here, we further investigated the role of HA on collagen fibril mineralization and the possible mechanism. The HA modification can significantly promote intrafibrillar collagen mineralization by reducing the electronegativity of the collagen surface to enhance calcium ions (Ca2+) binding capacity to create a local higher supersaturation. In addition, the HA also provides additional nucleation sites and shortens the induction time of amorphous calcium phosphate (ACP)-mediated hydroxyapatite (HAP) crystallization, which benefits mineralization. The acceleration effect of HA on intrafibrillar collagen mineralization is also confirmed in collagen hydrogel and in vitro dentin remineralization. These findings offer a physicochemical view of the regulation effect of carbohydrate polymers in the body on biomineralization, the fine prospect for an ideal biomaterial to repair collagen-mineralized tissues.

Hydroxyapatite: A journey from biomaterials to advanced functional materials

Hydroxyapatite (HAp), a well-known biomaterial, has witnessed a remarkable evolution over the years, transforming from a simple biocompatible substance to an advanced functional material with a wide range of applications. This abstract provides an overview of the significant advancements in the field of HAp and its journey towards becoming a multifunctional material. Initially recognized for its exceptional biocompatibility and bioactivity, HAp gained prominence in the field of bone tissue engineering and dental applications. Its ability to integrate with surrounding tissues, promote cellular adhesion, and facilitate osseointegration made it an ideal candidate for various biomedical implants and coatings. As the understanding of HAp grew, researchers explored its potential beyond traditional biomaterial applications. With advances in material synthesis and engineering, HAp began to exhibit unique properties that extended its utility to other disciplines. Researchers successfully tailored the composition, morphology, and surface characteristics of HAp, leading to enhanced mechanical strength, controlled drug release capabilities, and improved biodegradability. These modifications enabled the utilization of HAp in drug delivery systems, biosensors, tissue engineering scaffolds, and regenerative medicine applications. Moreover, the exceptional biomineralization properties of HAp allowed for the incorporation of functional ions and molecules during synthesis, leading to the development of bioactive coatings and composites with specific therapeutic functionalities. These functionalized HAp materials have demonstrated promising results in antimicrobial coatings, controlled release systems for growth factors and therapeutic agents, and even as catalysts in chemical reactions. In recent years, HAp nanoparticles and nanostructured materials have emerged as a focal point of research due to their unique physicochemical properties and potential for targeted drug delivery, imaging, and theranostic applications. The ability to manipulate the size, shape, and surface chemistry of HAp at the nanoscale has paved the way for innovative approaches in personalized medicine and regenerative therapies. This abstract highlights the exceptional evolution of HAp, from a traditional biomaterial to an advanced functional material. The exploration of novel synthesis methods, surface modifications, and nanoengineering techniques has expanded the horizon of HAp applications, enabling its integration into diverse fields ranging from biomedicine to catalysis. Additionally, this manuscript discusses the emerging prospects of HAp-based materials in photocatalysis, sensing, and energy storage, showcasing its potential as an advanced functional material beyond the realm of biomedical applications. As research in this field progresses, the future holds tremendous potential for HAp-based materials to revolutionize medical treatments and contribute to the advancement of science and technology.

Progress in microsphere-based scaffolds in bone/cartilage tissue engineering

Bone/cartilage repair and regeneration have been popular and difficult issues in medical research. Tissue engineering is rapidly evolving to provide new solutions to this problem, and the key point is to design the appropriate scaffold biomaterial. In recent years, microsphere-based scaffolds have been considered suitable scaffold materials for bone/cartilage injury repair because microporous structures can form more internal space for better cell proliferation and other cellular activities, and these composite scaffolds can provide physical/chemical signals for neotissue formation with higher efficiency. This paper reviews the research progress of microsphere-based scaffolds in bone/chondral tissue engineering, briefly introduces types of microspheres made from polymer, inorganic and composite materials, discusses the preparation methods of microspheres and the exploration of suitable microsphere pore size in bone and cartilage tissue engineering, and finally details the application of microsphere-based scaffolds in biomimetic scaffolds, cell proliferation and drug delivery systems.

A chlorogenic acid-chitosan complex bifunctional coating for improving osteogenesis differentiation and bactericidal properties of zirconia implants

Poor osteogenesis caused by limited bioactivity and peri-implantitis caused by bacterial colonization are the main challenges affecting the use of zirconia-based materials in dental implants. Accordingly, the development of a surface treatment method with an antibacterial effect and that promotes osteogenesis without damage to cells is crucial for yttrium-stabilized tetragonal zirconia (Y-TZP) implants. Herein, we have developed a functional surface modification strategy whereby a poly (ethylene imine)/hyaluronic acid /chitosan-chlorogenic acid (PEI/HA/CGA-CS) conjugate is deposited on a zirconia surface by the layer-by-layer (LBL) technique, enhancing its osteogenic differentiation and antibacterial activities. The results showed that the PEI/HA/CGA-CS coating improved the wettability of the zirconia surface and maintained stable release of CGA. The PEI/HA/CGA-CS functional coating was found to promote early cell adhesion, proliferation, differentiation, and calcification. The results of bacterial adhesion and activity tests showed that the coating effectively inhibits the proliferation and activity of Porphyromonas gingivalis (P. gingivalis) and Aggregatibacter actinomycetemcomitans (A. actinomycetemcomitans) without impairing the biological activity of osteoblasts. In addition, we found that the PEI/HA/CGA-CS coating enhances the osteogenesis of MC3T3-E1 cells by promoting the protein expression of Nephronectin (NPNT) and activating the Wnt/β-catenin signaling pathway. The above results are of profound significance for the practical application of zirconia-based implants. DATA AVAILABILITY: Data will be made available on request.

Size-dependent gold nanoparticles induce macrophage M2 polarization and promote intracellular clearance of Staphylococcus aureus to alleviate tissue infection

Tissue infection typically results from blood transmission or the direct inoculation of bacteria following trauma. The pathogen-induced destruction of tissue prevents antibiotics from penetrating the infected site, and severe inflammation further impairs the efficacy of conventional treatment. The current study describes the size-dependent induction of macrophage polarization using gold nanoparticles. Gold nanoparticles with a diameter of 50 ​nm (Au50) can induce M2 polarization in macrophages by inhibiting the NF-κB signaling pathway and stimulate an inflammatory response in the environment by inhibiting the MAPK signaling pathway LPS. Furthermore, the induced polarization and anti-inflammatory effects of the Au50 nanoparticles promoted the osteogenic differentiation of BMSCs in vitro. In addition, the overexpression of TREM2 in macrophage induced by Au50 nanoparticles was found to promote macrophage phagocytosis of Staphylococcus aureus, enhance the fusion of autophagosomes and lysosomes, accelerate the intracellular degradation of S. aureus, in addition to achieving an effective local treatment of osteomyelitis and infectious skin defects in conjunction with inflammatory regulation and accelerating bone regeneration. The findings, therefore, demonstrate that Au50 nanoparticles can be utilized as a promising nanomaterial for in vivo treatment of infections.

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.

Small extracellular vesicles with nanomorphology memory promote osteogenesis

Nanotopographical cues endow biomaterials the ability to guide cell adhesion, proliferation, and differentiation. Cellular mechanical memory can maintain the cell status by retaining cellular information obtained from past mechanical microenvironments. Here, we propose a new concept “morphology memory of small extracellular vesicles (sEV)” for bone regeneration. We performed nanotopography on titanium plates through alkali and heat (Ti8) treatment to promote human mesenchymal stem cell (hMSC) differentiation. Next, we extracted the sEVs from the hMSC, which were cultured on the nanotopographical Ti plates for 21 days (Ti8-21-sEV). We demonstrated that Ti8-21-sEV had superior pro-osteogenesis ability in vitro and in vivo. RNA sequencing further confirmed that Ti8-21-sEV promote bone regeneration through osteogenic-related pathways, including the PI3K-AKT signaling pathway, MAPK signaling pathway, focal adhesion, and extracellular matrix-receptor interaction. Finally, we decorated the Ti8-21-sEV on a 3D printed porous polyetheretherketone scaffold. The femoral condyle defect model of rabbits was used to demonstrate that Ti8-21-sEV had the best bone ingrowth. In summary, our study demonstrated that the Ti8-21-sEV have memory function by copying the pro-osteogenesis information from the nanotopography. We expect that our study will encourage the discovery of other sEV with morphology memory for tissue regeneration.

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Nanotopography fabricated on titanium plates has superior promoted hMSCs differentiation ability.

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sEV extracted from hMSCs which were cultured on Ti8 plates for 21 days had the superior pro-osteogenesis ability.

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Ti8-21-sEV have memory function through copy the pro-osteogenesis information from nanotopography.

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RNA sequencing confirmed that Ti8-21-sEV promote bone regeneration through osteogenic-related pathways.

Microporous surface containing flower-like molybdenum disulfide submicro-spheres of sulfonated polyimide with antibacterial effect and promoting bone regeneration and osteointegration

Implanted materials with both osteogenic and antibacterial functions are promising for facilitating osteointegration and preventing infection for orthopedic applications. In this work, we synthesized flower-like molybdenum disulfide (fMD) submicro-spheres containing nanosheets, which were incorporated onto the microporous surface of polyimide (PI) via concentrated sulfuric acid, suspending fMD contents of 5 wt% (SPM1) and 10 wt% (SPM2). Compared with sulfonated polyimide (SPM0), both SPM1 and SPM2 with microporous surfaces containing fMD exhibited nano-submicro-microporous surfaces, which improved the surface roughness, wettability, and surface energy. Due to there being more fMD submicro-spheres on the microporous surface, SPM2 revealed a better antibacterial effect than SPM1. In addition, compared with SPM1 and SPM0, SPM2 with more fMD significantly promoted rat bone marrow-derived stromal cell response in vitro. Moreover, SPM2 remarkably enhanced new bone formation and osteointegration in vivo. In summary, the combination of fMD with the microporous surface of SPM2 resulted in a nano-submicro-microporous surface with optimized surface performance, which possessed not only osteogenic bioactivity but also an antibacterial effect. As a bone implant, SPM2 with osteogenic and antibacterial functions may have enormous potential as a bone tissue substitute.

Fucoidan (Undaria pinnatifida)/Polydopamine Composite-Modified Surface Promotes Osteogenic Potential of Periodontal Ligament Stem Cells

Fucoidan, a marine-sulfated polysaccharide derived from brown algae, has been recently spotlighted as a natural biomaterial for use in bone formation and regeneration. Current research explores the osteoinductive and osteoconductive properties of fucoidan-based composites for bone tissue engineering applications. The utility of fucoidan in a bone tissue regeneration environment necessitates a better understanding of how fucoidan regulates osteogenic processes at the molecular level. Therefore, this study designed a fucoidan and polydopamine (PDA) composite-based film for use in a culture platform for periodontal ligament stem cells (PDLSCs) and explored the prominent molecular pathways induced during osteogenic differentiation of PDLSCs through transcriptome profiling. Characterization of the fucoidan/PDA-coated culture polystyrene surface was assessed by scanning electron microscopy and X-ray photoelectron spectroscopy. The osteogenic differentiation of the PDLSCs cultured on the fucoidan/PDA composite was examined through alkaline phosphatase activity, intracellular calcium levels, matrix mineralization assay, and analysis of the mRNA and protein expression of osteogenic markers. RNA sequencing was performed to identify significantly enriched and associated molecular networks. The culture of PDLSCs on the fucoidan/PDA composite demonstrated higher osteogenic potency than that on the control surface. Differentially expressed genes (DEGs) (n = 348) were identified during fucoidan/PDA-induced osteogenic differentiation by RNA sequencing. The signaling pathways enriched in the DEGs include regulation of the actin cytoskeleton and Ras-related protein 1 and phosphatidylinositol signaling. These pathways represent cell adhesion and cytoskeleton organization functions that are significantly involved in the osteogenic process. These results suggest that a fucoidan/PDA composite promotes the osteogenic potential of PDLSCs by activation of critical molecular pathways.

Nanotopography Sequentially Mediates Human Mesenchymal Stem Cell-Derived Small Extracellular Vesicles for Enhancing Osteogenesis

Engineered small extracellular vesicles (sEVs) are used as tools to enhance therapeutic efficacy. However, such application of sEVs is associated with several issues, including high costs and a high risk of tumorigenesis. Nanotopography has a greater influence on bone-related cell behaviors. However, whether nanotopography specifically mediate sEV content to perform particular biological functions remains unclear. Here, we demonstrate that selective nanotopography may be used to sequentially mediate human bone mesenchymal stem cell (hBMSC) sEVs to enhance the therapeutic efficacy of hBMSCs-EVs for osteogenesis. We subjected sEVs harvested from hBMSCs cultured on polished titanium plates (Ti) or nanotopographical titanium plates (Ti4) after 7, 14, and 21 d for RNA sequencing, and we found that there was no significant difference in sEV-miRNA expression after 7 d. Differentially expressed osteogenic-related microRNAs were founded after 14 days, and KEGG analysis indicated that the main microRNAs were associated with osteogenesis-related pathways, such as TGF-beta, AMPK, and FoxO. A significant difference was found in sEV-miRNAs expression after 21 d. We loaded sEV secreted from hBMSCs cultured on Ti4 after 21 d on 3D-printed porous PEEK scaffolds with poly dopamine (PDA) and found that such scaffolds showed superior osteogenic ability after 6- and 12-weeks. Here, we demonstrate the alkali- and heat-treated nanotopography with the ability of stimulating osteogenic differentiation of hBMSC can induce the secretion of pro-osteogenesis sEV, and we also found that sEVs meditate osteogenesis through miRNA. Thus, whether nanotopography has the ability to regulate other contents of sEVs such as proteins for enhancing osteogenesis needs further research. These findings may help us use nanotopography to extract sEVs for other biomedical applications, including cancer therapy.

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.

Antibacterial and Cellular Behaviors of Novel Zinc-Doped Hydroxyapatite/Graphene Nanocomposite for Bone Tissue Engineering

Bacteria are one of the significant causes of infection in the body after scaffold implantation. Effective use of nanotechnology to overcome this problem is an exciting and practical solution. Nanoparticles can cause bacterial degradation by the electrostatic interaction with receptors and cell walls. Simultaneously, the incorporation of antibacterial materials such as zinc and graphene in nanoparticles can further enhance bacterial degradation. In the present study, zinc-doped hydroxyapatite/graphene was synthesized and characterized as a nanocomposite material possessing both antibacterial and bioactive properties for bone tissue engineering. After synthesizing the zinc-doped hydroxyapatite nanoparticles using a mechanochemical process, they were composited with reduced graphene oxide. The nanoparticles and nanocomposite samples were extensively investigated by transmission electron microscopy, X-ray diffraction, and Raman spectroscopy. Their antibacterial behaviors against Escherichia coli and Staphylococcus aureus were studied. The antibacterial properties of hydroxyapatite nanoparticles were found to be improved more than 2.7 and 3.4 times after zinc doping and further compositing with graphene, respectively. In vitro cell assessment was investigated by a cell viability test and alkaline phosphatase activity using mesenchymal stem cells, and the results showed that hydroxyapatite nanoparticles in the culture medium, in addition to non-toxicity, led to enhanced proliferation of bone marrow stem cells. Furthermore, zinc doping in combination with graphene significantly increased alkaline phosphatase activity and proliferation of mesenchymal stem cells. The antibacterial activity along with cell biocompatibility/bioactivity of zinc-doped hydroxyapatite/graphene nanocomposite are the highly desirable and suitable biological properties for bone tissue engineering successfully achieved in this work.

Signaling Pathway and Transcriptional Regulation in Osteoblasts during Bone Healing: Direct Involvement of Hydroxyapatite as a Biomaterial

Bone defects and periodontal disease are pathological conditions that may become neglected diseases if not treated properly. Hydroxyapatite (HA), along with tricalcium phosphate and bioglass ceramic, is a biomaterial widely applied to orthopedic and dental uses. The in vivo performance of HA is determined by the interaction between HA particles with bone cells, particularly the bone mineralizing cells osteoblasts. It has been reported that HA-induced osteoblastic differentiation by increasing the expression of osteogenic transcription factors. However, the pathway involved and the events that occur in the cell membrane have not been well understood and remain controversial. Advances in gene editing and the discovery of pharmacologic inhibitors assist researchers to better understand osteoblastic differentiation. This review summarizes the involvement of extracellular signal-regulated kinase (ERK), p38, Wnt, and bone morphogenetic protein 2 (BMP2) in osteoblastic cellular regulation induced by HA. These advances enhance the current understanding of the molecular mechanism of HA as a biomaterial. Moreover, they provide a better strategy for the design of HA to be utilized in bone engineering.

Local administration with tauroursodeoxycholic acid could improve osseointegration of hydroxyapatite-coated titanium implants in ovariectomized rats

Despite advances in the pathogenesis of Tauroursodeoxycholic acid (TUDCA) on bone, the understanding of the effects and mechanisms of bone osseointegration in TUDCA-associated Hydroxyapatite (HA)-coated titanium implants remains poor. Therefore, the present work was aimed to evaluate the effect of local administration with TUDCA on HA-coated titanium implants osseointegration in ovariectomized(OVX) rats and further investigation of the possible mechanism. Twelve weeks after bilateral ovariectomy, all animals were randomly divided into three groups: sham operation(Sham) group, OVX group and TUDCA group, and all the rats from Sham group and OVX group received HA implants and animals belonging to group TUDCA received TUDCA-HA implants until death at 12 weeks. The bilateral femurs of rats were harvested for evaluation. TUDCA increased new bone formation around the surface of titanium rods and push-out force other than group OVX. Histology, Micro-CT and biochemical analysis results showed systemic TUDCA showed positive effects than OVX group on bone formation in osteopenic rats, with beneficial effect on via activation OPG/RANKL pathway and BMP-2/Smad1 pathway and microarchitecture as well as by reducing protein expression of TNF-α and IFN-γ. The present study suggests that local use of TUDCA may bring benefits to the osseointegration of HA-coated titanium implants in patients with osteoporosis, and this effect may be related to the inhibition of inflammatory reaction and promotion of osteogenesis.

[Research progress of nanomaterials in osteomyelitis treatment]

Objective

To review the related studies on the application of nanomaterials in the treatment of osteomyelitis, and to provide new ideas for the research and clinical treatment of osteomyelitis.

Methods

The literature about the treatment of osteomyelitis with nanomaterials at home and abroad in recent years was reviewed and analyzed.

Results

At present, surgical treatment and antibiotic application are the main treatment options for osteomyelitis. But there are many defects such as antibiotic resistance, residual bone defect, and low effective concentration of local drugs. The application of nanomaterials can make up for the above defects. In recent years, nanomaterials play an important role in the treatment of osteomyelitis by filling bone defects, establishing local drug delivery system, and self-antibacterial properties.

Conclusion

It will provide a new idea and an important research direction for the treatment of osteomyelitis to fully study the related characteristics of nanomaterials and select beneficial materials to make drug delivery system or substitute drugs.

Construction of a hierarchical micro & nanoporous surface for loading genistein on the composite of polyetheretherketone/tantalum pentoxide possessing antibacterial activity and accelerated osteointegration

Nanoporous tantalum pentoxide (NTP) particles with a pore size of about 10 nm were synthesized and blended with polyetheretherketone (PEEK) to fabricate a PEEK/NTP composite (PN). Subsequently, PN was treated by concentrated sulfuric acid to create a microporous surface (pore size of around 2 μm) on sulfonated PN (SPN), which formed a hierarchical micro & nanoporous surface. Compared with PN, the porous surface of SPN exhibited higher roughness, hydrophilicity, and surface energy. In addition, genistein (GT) was loaded into the porous surface of SPN (SPNG), which showed high GT loading capacity and sustained release of GT into phosphate buffered saline (PBS). Moreover, SPNG revealed excellent antibacterial activity, which inhibited bacterial (E. coli and S. aureus) growth in vitro due to the synergistic effects of both sulfonic acid (SO3H) groups and the sustained release of GT. Compared with PN, SPN significantly improved the adhesion, proliferation, and osteogenic differentiation of bone mesenchymal stem cells in vitro. Moreover, compared with SPN, SPNG further enhances the cell responses. Compared with PN, SPN remarkably improved bone formation and osteointegration in vivo. Furthermore, compared with SPN, SPNG further enhanced the osteointegration. In short, SPNG with a micro & nanoporous surface, SO3H groups, and the sustained release of GT exhibited antibacterial activity and accelerated osteointegration, which would have tremendous potential as drug-loaded implants for bone substitute.

Bifunctional scaffolds of hydroxyapatite/poly(dopamine)/carboxymethyl chitosan with osteogenesis and anti-osteosarcoma effect

Bifunctional scaffolds prepared by hydroxyapatite/poly(dopamine)/carboxymethyl chitosan with good osteogenesis and anti-osteosarcoma effect is promising for bone tumor therapy.

Parathyroid hormone (1-34) can reverse the negative effect of valproic acid on the osseointegration of titanium rods in ovariectomized rats

Objective

The present work was aimed to evaluate the effect of valproic acid (VPA)，Parathyroid hormone (1–34) (PTH)+VPA on Ti rods osseointegration in ovariectomized rats and further investigation of the possible mechanism.

Methods

The MC3T3-E1 cells were co-cultured with VPA，PTH ​+ ​VPA and induced to osteogenesis, and the cell viability，mineralization ability were observed by MTT and ALP staining，Alizarin Red staining and Western blotting. Twelve weeks after bilateral ovariectomy, all animals were randomly divided into four groups: group OVX and VPA，PTH ​+ ​VPA, and all the rats received Ti implants and animals belong to group VPA，PTH ​+ ​VPA received valproic acid (300 ​mg/day), valproic acid (300 ​mg/day) plus Parathyroid hormone (1–34) every 3 days (60 ​μg/kg), respectively, treatment until death at 12 weeks. Micro-CT, histology, biomechanical testing, bone metabolism index and Reverse transcription-quantitative polymerase chain reaction (RT-qPCR) analysis were used to observe the therapeutic effect and explore the possible mechanism.

Results

Results shown that VPA decreased new bone formation around the surface of titanium rods and push-out force other than group OVX. Histology, Micro-CT and biochemical analysis results showed combined application of systemic VPA showed harmful effects than OVX group on bone formation in osteopenia rats, with the worse effects on CTX-1, P1NP and microarchitecture as well as biomechanical parameters by down-regulated gene expression of Runx2, OCN, Smad1, BMP-2 and OPG, while up-regulated RANKL. However, after PTH treatment, the above indicators were significantly improved.

Conclusions

The present study suggests that systemic use of VPA may bring harm to the stability of titanium implants in osteoporosis, PTH can reverse the negative effect of VPA on the osseointegration of titanium rods in ovariectomized rats.

Translational potential of this article

According to our research, when patients with epilepsy have osteoporotic fractures, after joint replacement or internal fixation, continue to use sodium valproate for anti-epileptic therapy, the possibility of postoperative loosening increases, again on the basis of It can be reversed with the anti-osteoporosis drug parathyroid hormone (1-34).

Simvastatin can enhance the osseointegration of titanium rods in ovariectomized rats maintenance treatment with valproic acid

The present work was aimed to evaluate the effect of valproic acid(VPA), simvastatin (SIM)+VPA on Ti(titanium) rods osseointegration in ovariectomized(OVX) rats and further investigation of the possible mechanism. The MC3T3-E1 cells were co-cultured with VPA, SIM + VPA and induced to osteogenesis, and the cell viability, mineralization ability were observed by MTT and ALP staining, Alizarin Red staining and Western blotting. Twelve weeks after bilateral ovariectomy, all animals were randomly divided into three groups: group OVX and VPA, SIM + VPA, and all the rats received Ti implants and animals belong to group VPA, SIM + VPA received valproic acid(300 mg/kg/day), valproic acid(300 mg/kg/day) plus SIM (25 mg/kg/day), respectively, treatment until death at 12 weeks. Micro-CT, histology, biomechanical testing, bone metabolism index and Reverse transcription-quantitative polymerase chain reaction (RT-qPCR) analysis were used to observe the therapeutic effect and explore the possible mechanism. Results shown that VPA decreased new bone formation around the surface of titanium rods and push-out force other than group OVX. Histology, Micro-CT and biochemical analysis results showed combined application of systemic VPA showed harmful effects than OVX group on bone formation in osteopenic rats, with the worse effects on CTX-1, P1NP and microarchitecture as well as biomechanical parameters by down-regulated gene expression of Runx2, OCN, Smad1, BMP-2 and OPG, while up-regulated RANKL. However, after SIM treatment, the above indicators were significantly improved. The present study suggests that systemic use of VPA may bring harm to the stability of titanium implants in osteoporosis, SIM can reverse the negative effect of VPA on the osseointegration of titanium rods in ovariectomized rats.

Hydroxyapatite-Incorporated Composite Gels Improve Mechanical Properties and Bioactivity of Bone Scaffolds

Reinforcing polymeric scaffolds with micro/nanoparticles improve their mechanical properties and render them bioactive. In this study, hydroxyapatite (HA) is incorporated into 5% (w/v) gelatin methacrylate (GelMA) hydrogels at 1, 5, and 20 mg mL^-1 concentrations. The material properties of these composite gels are characterized through swelling, degradation, and compression tests. Using 3D cell encapsulation, the cytocompatibility and osteogenic differentiation of preosteoblasts are evaluated to assess the biological properties of the composite scaffolds. The in vitro assays demonstrate increasing cell proliferation and metabolic activity over the course of 14 d in culture. Furthermore, the scaffolds support osteogenic differentiation of the microencapsulated preosteoblasts. For the in vivo study, the composite scaffolds are subcutaneously implanted in rats for 14 d. The histological staining of the explanted in vivo samples exhibits the functional advantages of the scaffold's biocompatibility, biodegradability, and integration into the existing host tissue. This work demonstrates the enhanced mechanical and biological performance of HA-gelatin composite hydrogels for bone tissue engineering applications.