Spontaneously promoted osteogenic differentiation of MC3T3-E1 preosteoblasts on ultrathin layers of black phosphorus

Roles of circular RNAs in osteogenic/osteoclastogenic differentiation

The process of bone remodeling occurs and is regulated through interactions between osteoclasts, which resorb bone, and osteoblasts, which generate bone tissue. When the homeostatic balance between these two cell types is dysregulated, this can contribute to abnormal bone remodeling resulting in a loss of bone mass as is observed in osteoporosis (OP) and other forms of degenerative bone metabolic diseases. At present, details of molecular mechanism underlying the development of bone metabolic diseases such as OP remain to be elucidated. Circular RNAs (circRNAs) are small non-coding RNA molecules with a closed-loop structure that can regulate the differentiation of osteoclasts and osteoblasts. The present review provides a systematic overview of recent literature on the processes through which circRNAs regulate the dynamic balance between osteoblasts and osteoclasts that ultimately preserve bone homeostasis. It will also give insight that can shape current understanding of the pathogenesis of OP and other bone metabolic diseases to better guide diagnostic and treatment strategies for affected patients.

Construction of multifunctional coating with cationic amino acid-coupled peptides for osseointegration of implants

Osseointegration is an important indicator of implant success. This process can be improved by coating modified bioactive molecules with multiple functions on the surface of implants. Herein, a simple multifunctional coating that could effectively improve osseointegration was prepared through layer-by-layer self-assembly of cationic amino acids and tannic acid (TA), a negatively charged molecule. Osteogenic growth peptide (OGP) and the arginine-glycine-aspartic acid (RGD) functional polypeptides were coupled with Lys6 (K6), the two polypeptides then self-assembled with TA layer by layer to form a composite film, (TA-OGP@RGD)n. The surface morphology and biomechanical properties of the coating were analyzed in gas and liquid phases, and the deposition process and kinetics of the two peptides onto TA were monitored using a quartz crystal microbalance. In addition, the feeding consistency and adsorption ratios of the two peptides were explored by using fluorescence visualization and quantification. The (TA-OGP@RGD)n composite membrane mediated the early migration and adhesion of cells and significantly promoted osteogenic differentiation and mineralization of the extracellular matrix in vitro. Additionally, the bifunctional peptide exhibited excellent osteogenesis and osseointegration owing to the synergistic effect of the OGP and RGD peptides in vivo. Simultaneously, the (TA-OGP@RGD)n membrane regulated the balance of reactive oxygen species in the cell growth environment, thereby influencing the complex biological process of osseointegration. Thus, the results of this study provide a novel perspective for constructing multifunctional coatings for implants and has considerable application potential in orthopedics and dentistry.

Attributes of Nanomaterials and Nanotopographies for Improved Bone Tissue Engineering and Regeneration

Bone tissue engineering (BTE) is a multidisciplinary area that can solve the limitation of conventional grafting methods by developing viable and biocompatible bone replacements. The three essential components of BTE, i.e., Scaffold material and Cells and Growth factors altogether, facilitate support and guide for bone formation, differentiation of the bone tissues, and enhancement in the cellular activities and bone regeneration. However, there is a scarcity of the appropriate materials that can match the mechanical property as well as functional similarity to native tissue, considering the bone as hard tissue. In such scenarios, nanotechnology can be leveraged upon to achieve the desired aspects of BTE, and that is the key point of this review article. This review article examines the significant areas of nanotechnology research that have an impact on regeneration of bone: (a) scaffold with nanomaterials helps to enhance physicochemical interactions, biocompatibility, mechanical stability, and attachment; (b) nanoparticle-based approaches for delivering bioactive chemicals, growth factors, and genetic material. The article begins with the introduction of components and healing mechanisms of bone and the factors associated with them. The focus of this article is on the various nanotopographies that are now being used in scaffold formation, by describing how they are made, and how these nanotopographies affect the immune system and potential underlying mechanisms. The advantages of 4D bioprinting in BTE by using nanoink have also been mentioned. Additionally, we have investigated the importance of an in silico approach for finding the interaction between drugs and their related receptors, which can help to formulate suitable systems for delivery. This review emphasizes the role of nanoscale approach and how it helps to increase the efficacy of parameters of scaffold as well as drug delivery system for tissue engineering and bone regeneration.

Combined photothermal and sonodynamic therapy using a 2D black phosphorus nanosheets loaded coating for efficient bacterial inhibition and bone-implant integration

Surgical site infection (SSI) remains a major threat for implant failure in orthopedics. Herein, we report a dual-functional coating on Ti implants (named Ti/PDA/BP) with the integration of two-dimensional (2D) photo-sono sensitive black phosphorus nanosheets (BPNSs) and polydopamine (PDA) for efficient bacterial inhibition and bone-implant integration. For the first time, we employ BPNSs as generators of reactive radicals (ROS) under ultrasound (US) stimuli for implant associated infection. Additionally, the application of PDA improves the stability of BPNSs, the biocompatibility and photothermal performance of this hybrid coating. The as-prepared Ti/PDA/BP coating exhibits superior biocompatibility, bioactivity, photothermal and sonodynamic conversion abilities. Owing to the synergistic effect of hyperthermia and ·OH, Ti/PDA/BP damages the membrane and antioxidant system of Staphylococcus aureus, reaching a high antibacterial activity of 96.6% in vitro and 97.3% in vivo with rapid 10 min NIR irradiation and 20 min US treatment. In addition, we firstly unveil the significant effect of Ti/PDA/BP-based sonodynamic therapy (SDT) on bacterial membrane and oxidative stress at the transcriptome level. Moreover, the Ti/PDA/BP coating remarkably promotes osteogenesis in vitro and bone-implant osseointegration in vivo. Overall, development of Ti/PDA/BP bioactive coating provides a new strategy for combating the implant associated infection.

Combined Black Phosphorus Nanosheets with ICG/aPDT is an Effective Anti-Inflammatory Treatment for Periodontal Disorders

Introduction

Antibacterial photodynamic treatment (aPDT) has indispensable significance as a means of treating periodontal disorders because of its extraordinary potential for killing pathogenic bacteria by generating an overpowering amount of reactive oxygen species (ROS). The elevated ROS that may result from the antibacterial treatment procedure, however, could exert oxidative pressure inside periodontal pockets, causing irreparable damage to surrounding tissue, an issue that has severely restricted its medicinal applications. Accordingly, herein, we report the use of black phosphorus nanosheets (BPNSs) that can eliminate the side effects of ROS-based aPDT as well as scavenge ROS to produce an antibacterial effect.

Methods

The antibacterial effect of ICG/aPDT was observed by direct microscopic colony counting. A microplate reader and confocal microscope enabled measurements of cell viability and the quantification of ROS fluorescence. BPNS administration regulated the oxidative environment. IL-1β, IL-6, TNF-α, IL-10, TGF-β, and Arg-1 mRNA expression levels were used to assess the inflammatory response after BPNS treatment. In vivo, the efficacy of the combination of BPNSs and ICG/aPDT was evaluated in rats with periodontal disease by histomorphometric and immunohistochemical analyses.

Results

The CFU assay results verified the antibacterial effect of ICG/aPDT treatment, and ROS fluorescence quantification by CLSM indicated the antioxidative ability of the BPNSs. IL-1β, IL-6, TNF-α, IL-10, TGF-β, and Arg-1 mRNA expression levels were significantly decreased after BPNS treatment, confirming the in vitro anti-inflammatory effect of this nanomaterial. The histomorphometric and immunohistochemical analyses showed that the levels of proinflammatory factors decreased, suggesting that the BPNSs had anti-inflammatory effects in vivo.

Conclusion

Treatment with antioxidative BPNSs gives new insights into future anti-inflammatory therapies for periodontal disease and other infection-related inflammatory illnesses and provides an approach to combat the flaws of aPDT.

The Application of Black Phosphorus Nanomaterials in Bone Tissue Engineering

Recently, research on and the application of nanomaterials such as graphene, carbon nanotubes, and metal-organic frameworks has become increasingly popular in tissue engineering. In 2014, a two-dimensional sheet of black phosphorus (BP) was isolated from massive BP crystals. Since then, BP has attracted significant attention as an emerging nanomaterial. BP possesses many advantages such as light responsiveness, electrical conductivity, degradability, and good biocompatibility. Thus, it has broad prospects in biomedical applications. Moreover, BP is composed of phosphorus, which is a key bone tissue component with good biocompatibility and osteogenic repair ability. Thereby, BP exhibits excellent advantages for application in bone tissue engineering. In this review, the structure and the physical and chemical properties of BP are described. In addition, the current applications of BP in bone tissue engineering are reviewed to aid the future research and application of BP.

Selective Polyetheretherketone Implants Combined with Graphene Cause Definitive Cell Adhesion and Osteogenic Differentiation

INTRODUCTION

Polyetheretherketone (PEEK) has good biosafety and chemical stability for bone repair. However, PEEK is biologically inert and cannot promote bone apposition. This study investigated whether graphene-modified PEEK (G-PEEK) could improve cell adhesion and osteogenic differentiation.

METHODS

G-PEEK was prepared by melted blending and was characterized. In vitro, the biocompatibility of G-PPEK and the ability to promote cell adhesion and osteogenic differentiation in rabbit bone marrow mesenchymal stem cells (rBMSCs) were examined using live and dead cell double staining, the cell counting kit-8 (CCK-8) assay, immunofluorescence and quantitative real-time PCR (qRT‒PCR). An in vivo rabbit extra-articular graft-to-bone healing model was established. At 4 and 12 weeks after surgery, CT analysis and histological evaluation were performed.

RESULTS

In vitro, G-PEEK significantly improved the adhesion and proliferation of rBMSCs, with good biocompatibility. In vivo, G-PEEK promoted new bone formation at the site of the bone defect.

CONCLUSION

G-PEEK showed excellent osteogenesis performance, which promises new applications in implant materials.

Mangiferin promotes osteogenic differentiation and alleviates osteoporosis in the ovariectomized mouse via the AXL/ERK5 pathway

Mangiferin is a xanthone glucoside extracted from multiple plants, which has been shown to inhibit bone resorption and alleviate osteoporosis. However, the effect of purified Mangiferin on osteoporosis and its specific mechanisms is unknown. This study aimed to explore whether Mangiferin can promote osteogenic differentiation and alleviate osteoporosis in ovariectomized (OVX) mice and explore the potential mechanisms. Different concentrations and durations of Mangiferin were applied to MC3T3-E1 cells. The optimal concentration and duration of Mangiferin were determined by evaluating the cell viability via cell count kit-8 (CCK-8). The gene and protein expressions of AXL, ERK5, and osteogenic differentiation markers, including BMP2, Collagen1, OPN, Osterix, and Runx2, were detected using western blotting, qRT-PCR, immunofluorescence, and flow cytometry. Mangiferin was administered to OVX mice, and the severity of osteoporosis was evaluated by H and E staining, immunohistochemistry (IHC), microscopic computed-tomography (micro-CT) scanning, western blotting, and immunofluorescence of bone tissue. We found that Mangiferin promoted osteogenic differentiation in a dose-dependent manner at concentrations less than 30 μM. The 30 μM Mangiferin significantly upregulated the expression of AXL, ERK5, and osteogenic differentiation, including the ALP activity, percentage of alizarin red, and the levels of osteogenic differentiation markers. However, these expression levels decreased when AXL was knocked down in MC3T3-E1 cells and it could not be rescued by Mangiferin. Mangiferin relieved osteoporosis in OVX mice without causing severe organ damage. This study concluded that Mangiferin promoted osteogenic differentiation of MC3T3-E1 cells and alleviated osteoporosis in OVX mice. The potential mechanism was via the AXL/ERK5 pathway.

Ternary MXene-loaded PLCL/collagen nanofibrous scaffolds that promote spontaneous osteogenic differentiation

Conventional bioinert bone grafts often have led to failure in osseointegration due to low bioactivity, thus much effort has been made up to date to find alternatives. Recently, MXene nanoparticles (NPs) have shown prominent results as a rising material by possessing an osteogenic potential to facilitate the bioactivity of bone grafts or scaffolds, which can be attributed to the unique repeating atomic structure of two carbon layers existing between three titanium layers. In this study, we produced MXene NPs-integrated the ternary nanofibrous matrices of poly(L-lactide-co-ε-caprolactone, PLCL) and collagen (Col) decorated with MXene NPs (i.e., PLCL/Col/MXene), as novel scaffolds for bone tissue engineering, via electrospinning to explore the potential benefits for the spontaneous osteogenic differentiation of MC3T3-E1 preosteoblasts. The cultured cells on the physicochemical properties of the nanofibrous PLCL/Col/MXene-based materials revealed favorable interactions with the supportive matrices, highly suitable for the growth and survival of preosteoblasts. Furthermore, the combinatorial ternary material system of the PLCL/Col/MXene nanofibers obviously promoted spontaneous osteodifferentiation with positive cellular responses by providing effective microenvironments for osteogenesis. Therefore, our results suggest that the unprecedented biofunctional advantages of the MXene-integrated PLCL/Col nanofibrous matrices can be expanded to a wide range of strategies for the development of effective scaffolds in bone tissue regeneration.

PCL/Col I-based magnetic nanocomposite scaffold provides an osteoinductive environment for ADSCs in osteogenic cues-free media conditions

Background

The bone tissue engineering (BTE) approach has been introduced as an alternative to conventional treatments for large non-healing bone defects. Magnetism promotes stem cells' adherence to biocompatible scaffolds toward osteoblast differentiation. Furthermore, osteogenic differentiation media are expensive and any changes in its composition affect stem cells differentiation. Moreover, media growth factors possess a short half-life resulting in the rapid loss of their functions in vivo. With the above in mind, we fabricated a multilayered nanocomposite scaffold containing the wild type of Type I collagen (Col I) with endogenous magnetic property to promote osteogenesis in rat ADSCs with the minimum requirement of osteogenic differentiation medium.

Methods

Fe₃O₄ NPs were synthesized by co-precipitation method and characterized using SEM, VSM, and FTIR. Then, a PCL/Col I nanocomposite scaffold entrapping Fe₃O₄ NPs was fabricated by electrospinning and characterized using SEM, TEM, AFM, VSM, Contact Angle, tensile stretching, and FTIR. ADSCs were isolated from rat adipose tissue and identified by flow cytometry. ADSCs were loaded onto PCL/Col I and PCL/Col I/Fe₃O₄-scaffolds for 1–3 weeks with/without osteogenic media conditions. The cell viability, cell adhesion, and osteogenic differentiation were evaluated using MTT assay, SEM, DAPI staining, ALP/ARS staining, RT-PCR, and western blotting, respectively.

Results

SEM, VSM, and FTIR results indicated that Fe₃O₄ was synthesized in nano-sized (15–30 nm) particles with spherical-shaped morphology and superparamagnetic properties with approved chemical structure as FTIR revealed. According to SEM images, the fabricated magnetic scaffolds consisted of nanofiber (500–700 nm). TEM images have shown the Fe₃O₄ NPs entrapped in the scaffold's fiber without bead formation. FTIR spectra analysis confirmed the maintenance of the natural structure of Col I, PCL, and Fe₃O₄ upon electrospinning. AFM data have shown that MNPs incorporation introduced stripe-like topography to nanofibers, while the depth of the grooves has decreased from 800 to 500 nm. Flow cytometry confirmed the phenotype of ADSCs according to their surface markers (i.e., CD29 and CD105). Additionally, Fe₃O₄ NP improved nanocomposite scaffold strength, wettability, porosity, biocompatibility and also facilitates the ALP activity, calcium-mineralization. Finally, magnetic nanocomposite scaffolds upregulated osteogenic-related genes or proteins’ expression (e.g., Col I, Runx2, OCN, ON, BMP2) in seeded ADSCs with/without osteo-differentiation media conditions.

Conclusions

Together, these results indicate that Fe₃O₄ NPs within the natural structure of Col I increase osteogenic differentiation in osteogenic cues-free media conditions. This effect could be translated in vivo toward bone defects healing. These findings support the use of natural ECM materials alongside magnetic particles as composite scaffolds to achieve their full therapeutic potential in BTE treatments.

Graphical Abstract

Enhanced osseointegration of dental implants with reduced graphene oxide coating

BACKGROUND

The implants of pure titanium (Ti) and its alloys can lead to implant failure because of their poor interaction with bone-associated cells during bone regeneration. Surface modification over implants has achieved successful implants for enhanced osseointegration. Herein, we report a robust strategy to implement bioactive surface modification for implant interface enabled by the combinatorial system of reduced graphene oxide (rGO)-coated sandblasted, large-grit, and acid-etched (SLA) Ti to impart benefits to the implant.

METHODS

We prepared SLA Ti (ST) implants with different surface modifications [i.e., rGO and recombinant human bone morphogenetic protein-2 (rhBMP-2)] and investigated their dental tissue regenerating ability in animal models. We performed comparative studies in surface property, in vitro cellular behaviors, and in vivo osseointegration activity among different groups, including ST (control), rhBMP-2-immobilized ST (BI-ST), rhBMP-2-treated ST (BT-ST), and rGO-coated ST (R-ST).

RESULTS

Spectroscopic, diffractometric, and microscopic analyses confirmed that rGO was coated well around the surfaces of Ti discs (for cell study) and implant fixtures (for animal study). Furthermore, in vitro and in vivo studies revealed that the R-ST group showed significantly better effects in cell attachment and proliferation, alkaline phosphatase activity, matrix mineralization, expression of osteogenesis-related genes and protein, and osseointegration than the control (ST), BI-ST, and BT-ST groups.

CONCLUSION

Hence, we suggest that the rGO-coated Ti can be a promising candidate for the application to dental or even orthopedic implants due to its ability to accelerate the healing rate with the high potential of osseointegration.

Potential Load-Bearing Bone Substitution Material: Carbon-Fiber-Reinforced Magnesium-Doped Hydroxyapatite Composites with Excellent Mechanical Performance and Tailored Biological Properties

A potential load-bearing bone substitution and repair material, that is, carbon fiber (CF)-reinforced magnesium-doped hydroxyapatite (CF/Mg-HAs) composites with excellent mechanical performance and tailored biological properties, was constructed via the hydrothermal method and spark plasma sintering. A high-resolution transmission electron microscopy (TEM) was employed to characterize the nanostructure of magnesium-doped hydroxyapatite (Mg-HA). TEM images showed that the doping of Mg-induced distortions and dislocations in the hydroxyapatite lattice, resulting in decreased crystallinity and enhanced dissolution. Compressive strengths of 10% magnesium-doped hydroxyapatite (1Mg-HAs) and CF-reinforced 1Mg-HAs (CF/1Mg-HAs) were within the range of that of cortical bone. Compared with 1Mg-HAs, the fracture toughness of CF/1Mg-HAs increased by approximately 38%. The bioactivity, biocompatibility, and osteogenic induction properties of Mg-HAs and CF/Mg-HAs composites were evaluated in vitro using simulated body fluid (SBF) immersion, cell culture, osteogenic differentiation of bone marrow mesenchymal stem cells (BMSCs), and expression of genes associated with osteogenesis. When Mg-HAs were immersed in SBF, Mg²⁺ continued to release for up to 21 days. Mg-HAs demonstrated a satisfactory ability to induce apatite formation in comparison with HAs. The cell proliferation and morphology on CF/1Mg-HAs were similar to those of 1Mg-HAs, suggesting that adding CF had no adverse effect on cellular activity. The expression levels of osteogenesis-related genes [osteocalcin (OPN), osteopontin (OCN), and runt-related transcription factor 2 (Runx2)] on 1Mg-HAs were significantly higher at days 3 and 7 than those on HAs and 0.5Mg-HAs groups. This finding suggests that a certain amount of Mg doping had beneficial influences in the different stages of osteogenic differentiation and could induce osteogenic differentiation of BMSCs. The new bone volume to total volume ratio of implanted 1Mg-HAs (30.9% ± 4.1%) and CF/1Mg-HAs (25.4% ± 5.4%) was remarkably higher than that of HAs (21.6% ± 3.9%). 1Mg-HAs and CF/1Mg-HAs tailored an ideal effect of new bone information and implant osseointegration. The excellent mechanical performance and tailored biological properties of CF/Mg-HAs were attributed to nano Mg-doped HA, CF reinforcing, refined microstructure, and controlled composition.

Phenotypic change of mesenchymal stem cells into smooth muscle cells regulated by dynamic cell-surface interactions on patterned arrays of ultrathin graphene oxide substrates

The topographical interface of the extracellular environment has been appreciated as a principal biophysical regulator for modulating cell functions, such as adhesion, migration, proliferation, and differentiation. Despite the existed approaches that use two-dimensional nanomaterials to provide beneficial effects, opportunities evaluating their impact on stem cells remain open to elicit unprecedented cellular responses. Herein, we report an ultrathin cell-culture platform with potential-responsive nanoscale biointerfaces for monitoring mesenchymal stem cells (MSCs). We designed an intriguing nanostructured array through self-assembly of graphene oxide sheets and subsequent lithographical patterning method to produce chemophysically defined regions. MSCs cultured on anisotropic micro/nanoscale patterned substrate were spontaneously organized in a highly ordered configuration mainly due to the cell-repellent interactions. Moreover, the spatially aligned MSCs were spontaneously differentiated into smooth muscle cells upon the specific crosstalk between cells. This work provides a robust strategy for directing stem cells and differentiation, which can be utilized as a potential cell culture platform to understand cell-substrate or cell-cell interactions, further developing tissue repair and stem cell-based therapies.