Facilitate Bone Regeneration Research Articles

Multifunctional BPs/MT@PLGA‐ALE Nanospheres for Treatment of Osteoporotic Fracture with Near‐Infrared Irradiation

AbstractOsteoporotic fracture, which is a clinical complication of osteoporosis featured with the imbalance of bone homeostasis. Non‐surgical intervention is frequently required post‐operatively to ameliorate the fracture healing. Nevertheless, current non‐surgical therapies are mostly performed in a non‐targeted manner without giving enough consideration to the pathological characteristics of osteoporosis. Therefore, it is highly desirable to develop an optimal strategy for promoting fracture healing under osteoporotic conditions. In this study, a multifunctional therapeutic nanoplatform is designed to work in conjunction with near‐infrared irradiation. Specifically, poly (lactic‐co‐glycolic acid) (PLGA) is functionalized with alendronate (ALE) and black phosphorus nanosheets (BPs) together with melatonin (MT) molecules are encapsulated by PLGA‐ALE to produce the multifunctional BPs/MT@PLGA‐ALE nanospheres. In this structure, BPs degrade gradually and deliver mild photothermal effects to facilitate bone regeneration, whereas MT has the dual‐capability of suppressing osteoclastogenesis and promoting osteogenesis. Moreover, ALE endows the nanoplatform with the reliable bone‐targeting capacity to improve the therapeutic effects. The combination of BPs/MT@PLGA‐ALE nanospheres and photothermal therapy significantly improve post‐surgical healing of osteoporotic fracture by modulating the tumor necrosis factor and cell death‐related signaling pathways. This study reveals a promising strategy to treat osteoporotic fracture and broadens the application of nanomaterials in the biomedical field.

Sustained release silicon from 3D bioprinting scaffold using silk/gelatin inks to promote osteogenesis

Repairing extensive bone defects that cannot self-heal has been a clinical challenge. The construction of scaffolds with osteogenic activity through tissue engineering can provide an effective strategy for bone regeneration. This study utilized gelatin, silk fibroin, and Si3N4 as scaffold materials to prepare silicon-functionalized biomacromolecules composite scaffolds using three-dimensional printing (3DP) technology. This system delivered positive outcomes when Si3N4 levels were 1 % (1SNS). The results showed that the scaffold had a porous reticular structure with a pore size of 600–700 μm. The Si3N4 nanoparticles were distributed uniformly in the scaffold. The scaffold could release Si ions for up to 28 days. In vitro experiments showed that the scaffold had good cytocompatibility, promoting the osteogenic differentiation of mesenchymal stem cells (MSCs). In vivo experiments on bone defects in rats showed that the 1SNS group facilitated bone regeneration. Therefore, the composite scaffold system showed potential for application in bone tissue engineering.

Biomimetic hydroxyapatite coating on the 3D-printed bioactive porous composite ceramic scaffolds promoted osteogenic differentiation via PI3K/AKT/mTOR signaling pathways and facilitated bone regeneration in vivo

• Bionic hierarchical scaffold fabricated by 3D-printing and surface mineralization. • The obtained biomimetic multi-structured scaffolds facilitate bone regeneration. • Regulation of cell fate in activated PI3K/AKT/mTOR signaling were confirmed. • Hydroxyapatite coating accelerates osseointegration and enhance bone-augmentation. • A two-step method enriches and guides the design of modified bone graft materials. The architecture and surface modifications have been regarded as effective methods to enhance the biological response of biomaterials in bone tissue engineering. The porous architecture of the implantation was essential conditions for bone regeneration. Meanwhile, the design of biomimetic hydroxyapatite (HAp) coating on porous scaffolds was demonstrated to strengthen the bioactivity and stimulate osteogenesis. However, bioactive bio-ceramics such as β-tricalcium phosphate (β-TCP) and calcium silicate (CS) with superior apatite-forming ability were reported to present better osteogenic activity than that of HAp. Hence in this study, 3D-printed interconnected porous bioactive ceramics β-TCP/CS scaffold was fabricated and the biomimetic HAp apatite coating were constructed in situ via hydrothermal reaction, and the effects of HAp apatite layer on the fate of mouse bone mesenchymal stem cells (mBMSCs) and the potential mechanisms were explored. The results indicated that HAp apatite coating enhanced cell proliferation, alkaline phosphatase (ALP) activity, and osteogenic gene expression. Furthermore, PI3K/AKT/mTOR signaling pathway is proved to have an important impact on cellular functions. The present results demonstrated that the key molecules of phosphatidylinositol 3-kinase (PI3K), protein kinase B (AKT) and mammalian target of rapamycin (mTOR) were activated after the biomimetic hydroxyapatite coating were constructed on the 3D-printed ceramic scaffolds. Besides, the activated influence on the protein expression of Runx2 and BMP2 could be suppressed after the treatment of inhibitor HY-10358. In vivo studies showed that the constructed HAp coating promoted bone formation and strengthen the bone quality. These results suggest that biomimetic HAp coating constructed on the 3D-printed bioactive composite scaffolds could strengthen the bioactivity and the obtained biomimetic multi-structured scaffolds might be a potential alternative bone graft for bone regeneration.

Bioactive elements manipulate bone regeneration.

While bone tissue is known for its inherent regenerative abilities, various pathological conditions and trauma can disrupt its meticulously regulated processes of bone formation and resorption. Bone tissue engineering aims to replicate the extracellular matrix of bone tissue as well as the sophisticated biochemical mechanisms crucial for effective regeneration. Traditionally, the field has relied on external agents like growth factors and pharmaceuticals to modulate these processes. Although efficacious in certain scenarios, this strategy is compromised by limitations such as safety issues and the transient nature of the compound release and half-life. Conversely, bioactive elements such as zinc (Zn), magnesium (Mg) and silicon (Si), have garnered increasing interest for their therapeutic benefits, superior stability, and reduced biotic risks. Moreover, these elements are often incorporated into biomaterials that function as multifaceted bioactive components, facilitating bone regeneration via release on-demand. By elucidating the mechanistic roles and therapeutic efficacy of the bioactive elements, this review aims to establish bioactive elements as a robust and clinically viable strategy for advanced bone regeneration.

Promotion of osteoporotic bone healing by a tannic acid modified strontium-doped biomimetic bone lamella with ROS scavenging capacity and pro-osteogenic effect

The impaired osteogenic ability and excessive accumulation of reactive oxygen species (ROS) under osteoporosis severely weaken repair performance of biomimetic bone grafts. Currently, biomimetic bone grafts, capable of highly simulating bone hierarchy, could remarkably promote bone regeneration without systemic disease. Decorating biomimetic bone grafts with bioactivities without compromising hierarchical biomimicry stands as a feasible approach to treat the osteoporotic bone defect. Herein, through mineralizing decellularized collagen lamellae via strontium (Sr)- amorphous calcium phosphate and further modifying with tannic acid (TA), TA modified Sr-doped biomimetic bone lamellae was engineered. The physicochemical properties, ROS scavenging capacity and pro-osteogenic effect on osteoporotic bone marrow mesenchymal stem cells of construct were systemically evaluated. The results showed that TA and Sr can be successfully decorated without impairing the nano- and micro-architecture of biomimetic bone lamellae. The construct not only exhibited a potent and long-standing performance to eliminate ROS, but also effectively fostered the proliferation and osteogenic differentiation of osteoporotic bone marrow mesenchymal stem cells under oxidative stress environment. After implantation in the critical-sized bone defect of osteoporotic rat, it potently facilitated bone regeneration via synergistically activating PI3K/AKT signaling pathway. Hence, this construct is projected to be candidate for further engineering biomimetic bone grafts with more complicated hierarchy for accelerated healing of the osteoporotic bone defect.

Building Osteogenic Microenvironments with a Double-Network Composite Hydrogel for Bone Repair.

The critical factor determining the in vivo effect of bone repair materials is the microenvironment, which greatly depends on their abilities to promote vascularization and bone formation. However, implant materials are far from ideal candidates for guiding bone regeneration due to their deficient angiogenic and osteogenic microenvironments. Herein, a double-network composite hydrogel combining vascular endothelial growth factor (VEGF)-mimetic peptide with hydroxyapatite (HA) precursor was developed to build an osteogenic microenvironment for bone repair. The hydrogel was prepared by mixing acrylated β-cyclodextrins and octacalcium phosphate (OCP), an HA precursor, with gelatin solution, followed by ultraviolet photo-crosslinking. To improve the angiogenic potential of the hydrogel, QK, a VEGF-mimicking peptide, was loaded in acrylated β-cyclodextrins. The QK-loaded hydrogel promoted tube formation of human umbilical vein endothelial cells and upregulated the expression of angiogenesis-related genes, such as Flt1, Kdr, and VEGF, in bone marrow mesenchymal stem cells. Moreover, QK could recruit bone marrow mesenchymal stem cells. Furthermore, OCP in the composite hydrogel could be transformed into HA and release calcium ions facilitating bone regeneration. The double-network composite hydrogel integrated QK and OCP showed obvious osteoinductive activity. The results of animal experiments showed that the composite hydrogel enhanced bone regeneration in skull defects of rats, due to perfect synergistic effects of QK and OCP on vascularized bone regeneration. In summary, improving the angiogenic and osteogenic microenvironments by our double-network composite hydrogel shows promising prospects for bone repair.

LL-37-Coupled Porous Composite Scaffold for the Treatment of Infected Segmental Bone Defect.

Increased multiantibiotic-resistant bacteria means that infected bone defects remain a significant challenge to clinics. Great interest has emerged in the use of non-antibiotic antimicrobials to reduce the rate of multiantibiotic-resistant bacterial infection and facilitate bone regeneration. The cationic antimicrobial peptide LL-37 is the sole human cathelicidin and has shown nonspecific activity against a broad spectrum of microorganisms. In this study, we fabricated the poly(lactic-co-glycolic acid)/β-calcium phosphate/peptide LL-37 (PLGA/TCP/LL-37, PTL) scaffold with low-temperature 3D-printing technology for the treatment of infected segmental bone defects. The prepared scaffolds were divided into three groups: a high LL-37 concentration group (PTHL), low LL-37 concentration group (PTLL) and blank control group (PT). The cytocompatibility and antimicrobial activity of the engineered scaffolds were tested in vitro, and their osteogenesis properties were assessed in vivo in a rat infected bone defect model. We found the fabricated PTL scaffold had a well-designed porous structure that could support a steady and prolonged LL-37 release. Furthermore, the PTHL group showed strong antibacterial activity against Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli) without any inhibition of the proliferation or alkaline phosphatase activity of rat bone marrow mesenchymal stem cells (BMSCs) in vitro. In addition, the infected femoral defects implanted with PTHL group displayed new bone formation in four weeks without any evidence of residual bacteria, which showed similar antibacterial outcomes to the vancomycin and cancellous bone mixture group. In conclusion, the PTHL composite scaffold is a promising non-antibiotic antimicrobial graft with good biodegradability, biocompatibility, and osteogenic capability for infected bone defects.

Se-doped plasma electrolytic oxidation coating enhances angiogenesis induction performance of Ti implant

Vessel formation is crucial for bone remodeling process. In this study, we fabricated a selenium (Se) incorporated plasma electrolytic oxidation (PEO) coating on titanium (Ti) surface and its influence on the angiogenesis behaviors of human umbilical vein endothelial cells (HUVECs) were investigated. The Se-doped PEO coating exhibited a porous morphology and a sustained low does release of Se ions. Although the cells cultured on the coated Ti showed few differences in proliferation comparing to uncoated Ti, the cells exhibited a higher migration ratio and up-regulated angiogenesis-related genes (including KDR, VEGF, and HIF-α). Therefore, the Se-doped PEO coating provides a new strategy to enhance vascularization surrounding the bone and thus facilitating bone regeneration after implantation.

Effects of Exercise or Mechanical Stimulation on Bone Development and Bone Repair.

The development and regeneration of the bone are tightly regulated by mechanical cues. Multiple cell types, including osteoblasts, osteocytes, osteoclasts, mesenchymal stem cells (MSCs), and recently found skeletal stem cells (SSCs), are responsible for efficient bone development and injury repair. The immune cells in the environment interact with bone cells to maintain homeostasis and facilitate bone regeneration. Investigation of the mechanism by which these cells sense and respond to mechanical signals in bone is fundamental for optimal clinical intervention in bone injury healing. We discuss the effects of exercise programs on fracture healing in animal models and human patients, which encouragingly suggest that carefully designed exercise prescriptions can improve the result of fracture healing during the remodeling phase. However, additional clinical tracing and date accumulation are still required for the pervasive application of exercise prescriptions to improve fracture healing.

Mechanically Robust Hydrogels Facilitating Bone Regeneration through Epigenetic Modulation.

Development of artificial biomaterials by mimicking extracellular matrix of bone tissue is a promising strategy for bone regeneration. Hydrogel has emerged as a type of viable substitute, but its inhomogeneous networks and weak mechanics greatly impede clinical applications. Here, a dual crosslinked gelling system is developed with tunable architectures and mechanics to promote osteogenic capacity. Polyhedral oligomeric silsesquioxane (POSS) is designated as a rigid core surrounded by six disulfide-linked PEG shells and two 2-ureido-4[1H]-pyrimidinone (UPy) groups. Thiol-disulfide exchange is employed to fabricate chemical network because of the pH-responsive "on/off" function. While self-complementary UPy motif is capable of optimizing local microstructure to enhance mechanical properties. Taking the merits of biocompatibility and high-mechanics in periodontal ligament stem cells (PDLSCs) proliferation, attachment, and osteogenesis, hybrid hydrogel exhibits outstanding osteogenic potential both in vitro and in vivo. Importantly, it is the first time that a key epigenetic regulator of ten-eleven translocation 2 (Tet2) is discovered to significantly elevate the continuously active the WNT/β-catenin through Tet2/HDAC1/E-cadherin/β-catenin signaling cascade, thereby promoting PDLSCs osteogenesis. This work represents a general strategy to design the hydrogels with customized networks and biomimetic mechanics, and illustrates underlying osteogenic mechanisms that will extend the design rationales for high-functional biomaterials in tissue engineering.

Bridging technique and science: A review of the molecular signals from long bone development that guiding bone regeneration

Bone development is a sequence of coordinated events that eventually forms the skeleton. The regenerative capacity of bone is preserved through adulthood. After injury, bone can be restored to its functional and homeostatic state. Orthopaedic surgeons take advantage of this regenerative potential in procedures such as distraction osteogenesis where a low-energy fracture is created followed by distraction at a controlled rate to form new bone. This review uses the fundamental elements of distraction osteogenesis to understand the molecular pathways underlying skeletal development harnessed during injury and orthopaedic surgery to regenerate bone. We highlight the developmental origins of the axial skeleton with an emphasis on the molecular signals driving the bone development. Additionally, we discuss the role of major signaling pathways during bone regeneration and highlight how bone regeneration recapitulates skeletal development. Although other pathways exist for this phenomenon such as anoxia, these pathways function during distraction osteogenesis has not been delineated from a basic science perspective. Finally, we review the four components of distraction osteogenesis that facilitate bone regeneration specifically outlining the best practices for tibial distraction. • Relationship of skeletal development to bone formation. • Bone formation via distraction osteogenesis. • Preservation of bone regenerative capacity through adulthood. • Signaling pathways that recapitulate skeletal development. • Signaling pathways involved in distraction osteogenesis.

The efficacy of a semi-resorbable membrane based on silk fibroin-Glycerol on bone regeneration in rabbit calvarial defects compared to a commercial collagen membrane.

Silk fibroin-glycerol-based membranes were fabricated and characterized for use as a self-maintaining and non-collapsible semi-resorbable membrane in guided bone regeneration. The study assessed the bone regeneration capacity of silk fibroin-glycerol-based membranes compared to a collagen membrane in 10-mm circular bilateral calvarial defects of 20 male New Zealand white rabbits. The animals were divided into two sets of time frames of 4 and 12 weeks and allocated into four groups (n = 5/group); an empty defect (E), a collagen membrane (Bio-Gide®; BG), a silk fibroin-glycerol-collagen membrane (SGC), and a silk fibroin-glycerol membrane (SG). The bone density (optical density, OD) from the 2D radiographs, tissue reaction from histological sections, new bone volume, and area from micro-CT and the histomorphometry were evaluated. The Mean OD of the E (34.49 ± 14.21%) and BG groups (35.71 ± 9.65%) at 12 weeks were higher than at 4 weeks, but the SGC (39.04 ± 7.94%) and SG (40.96 ± 9.25%) groups were lower at 4 weeks. The new bone volumes at 4 weeks of the SG (24.19 ± 1.35%) and SGC groups (24.19 ± 3.47%) were significantly higher than the BG group (16.93 ± 2.95%) but were not different from the E group (18.39±4.78%). At 12 weeks, the new bone volumes in the SGC (29.09 ± 3.81%), SG (29.11 ± 5.94%), and BG groups (26.26 ± 4.42%) were higher than in the E group (21.63 ± 5.81%) without statistical significance. Histological images in the SGC and SG groups showed slow biodegradation without a foreign body reaction. The new bone area at 4 weeks was lowest in BG (12.95 ± 5.44%), and the others were comparable. At 12 weeks, the new bone area in the E group (23.55±8.69%) was lower than the BG (31.42 ± 6.18%), SG (35.25 ± 13.92%), and SGC groups (36.35 ± 10.23%). Silk fibroin-glycerol-based membranes are semi-resorbable membranes that possess a self-maintaining property, have a barrier function without collapsing, and are successful in facilitating bone regeneration.

A Bilayer Membrane Doped with Struvite Nanowires for Guided Bone Regeneration.

Guided bone regeneration (GBR) therapy demonstrates a prominent curative effect on the management of craniomaxillofacial (CMF) bone defects. In this study, a GBR membrane consisting of a microporous layer and a struvite-nanowire-doped fibrous layer is constructed via non-solvent induced phase separation, followed by an electrospinning procedure to treat critical-sized calvarial defects. The microporous layer shows selective permeability for excluding the rapid-growing non-osteogenic tissues and potential wound stabilization. The nanowire-like struvite is synthesized as the deliverable therapeutic agent within the fibrous layer to facilitate bone regeneration. Such a membrane displays a well-developed heterogeneous architecture, satisfactory mechanical performance, and long-lasting characteristics. The in vitro biological evaluation reveals that apart from being a strong barrier, the bilayer struvite-laden membrane can actively promote cellular adhesion, proliferation, and osteogenic differentiation. Consequently, the multifunctional struvite-doped membranes are applied to treat 5mm-sized bilateral calvarial defects in rats, resulting in overall improved healing outcomes compared with the untreated or the struvite-free membrane-treated group, which is characterized by enhanced osteogenesis and significantly increased new bone formation. The encouraging preclinical results reveal the great potential of the bilayer struvite-doped membrane as a clinical GBR device for augmenting large-area CMF bone reconstruction.

Strontium-incorporated bioceramic scaffolds for enhanced osteoporosis bone regeneration

The restoration of bone defects caused by osteoporosis remains a challenge for surgeons. Strontium ranelate has been applied in preventative treatment approaches due to the biological functions of the trace element strontium (Sr). In this study, we aimed to fabricate bioactive scaffolds through Sr incorporation based on our previously developed modified amino-functional mesoporous bioactive glass (MBG) and to systematically investigate the bioactivity of the resulting scaffold in vitro and in vivo in an osteoporotic rat model. The results suggested that Sr-incorporated amino-functional MBG scaffolds possessed favorable biocompatibility. Moreover, with the incorporation of Sr, osteogenic and angiogenic capacities were upregulated in vitro. The in vivo results showed that the Sr-incorporated amino-functional MBG scaffolds achieved better bone regeneration and vessel formation. Furthermore, bioinformatics analysis indicated that the Sr-incorporated amino-functional MBG scaffolds could reduce reactive oxygen species levels in bone marrow mesenchymal stem cells in the osteoporotic model by activating the cAMP/PKA signaling pathway, thus playing an anti-osteoporosis role while promoting osteogenesis. This study demonstrated the feasibility of incorporating trace elements into scaffolds and provided new insights into biomaterial design for facilitating bone regeneration in the treatment of osteoporosis.

Physio-mechanical and Biological Effects Due to Surface Area Modifications of 3D Printed β-tri- calcium phosphate: An In Vitro Study

Bone defects are associated with trauma, congenital disorders, non-unions, or infections following surgical procedures. Defects which are unable to heal spontaneously are categorized as “critical sized” and are commonly treated using bone grafts in an effort to facilitate bone regeneration and stabilization. Grafting materials can be either natural or synthetic, each having their respective advantages and disadvantages. Synthetic bone grafts are favored due to their ability to be tailored to exhibit desired properties and geometric configurations. β-tricalcium phosphate (β-TCP) is a synthetic grafting material that has been widely utilized for regenerative purposes due to its favorable osteoconductive properties. In combination with 3D printing, grafting materials can be further customized with respect to their macro and micro features. One way to customize devices is by using 3D printing and varying the surface area, by varying the internal component measurements. The objective of this study was to compare the effect of porosity and surface area of 3D printed β-TCP scaffolds with different strut diameters and the effect on cell proliferation in vitro. ß-TCP scaffolds were printed using a custom-built 3D direct-write micro printer with syringes equipped with different extrusion tip diameters (fdiameter: 200 µm, 250 µm and 330 µm). After sintering and post processing, scaffolds were subjected to micro-computed tomography (µCT) and a Scanning Electron Microscope (SEM) to evaluate surface area and porosity, respectively. Compressive strength was assessed using a universal testing machine. Cell proliferation was assessed through cellular viability, using human osteoprogenitor cells. The surface area of the scaffolds was found to increase with smaller strut diameters. Statistically significant differences (p<0.05) were detected for cellular proliferation, between the smallest extrusion diameter, 200 μm, and the largest diameter, 330 μm, after 48-, 72-, and 168-hours. No statistical significances were detected (p>0.05) with regards to the mechanical properties between groups. This study demonstrated that a smaller diameter rod yielded a higher surface area resulting in increased levels of cellular proliferation. Therefore, tailoring rod dimensions has the capacity to enhance cellular adhesion and ultimately, proliferation.

Modified Biodegradation Behavior Induced Beneficial Microenvironments for Bone Regeneration by Low Addition of Gadolinium in Zinc.

Zinc (Zn) shows a great potential as a biodegradable material for bone implants after a decade of systematic research and development. However, uncontrollable biodegradation behavior and biphasic dose-response prevent Zn from fulfilling its essential role in facilitating bone regeneration. In this study, the low addition of gadolinium (Gd) modifies the intrinsic microstructure of Zn in terms of grain size distribution, grain boundary misorientation, and texture. Adding Gd refines grain size distribution and creates a stronger basal plane texture in Zn, consequently, changing the current density distribution and reducing the anode dissolution rate during corrosion. As a result, uniform degradation is more predominant in Zn-0.4Gd alloy implant, in comparison to localized degradation in pure Zn implant in bone environments. The modified biodegradation behavior of the Zn-0.4Gd alloy implant induces significantly better new bone formation and osseointegration compared to the pure Zn implant. Therefore, Gd with trace amounts is able to tune the degradation behavior and improve the performance of Zn-based implants in promoting bone regeneration.

Biomimetic Remineralization of an Extracellular Matrix Collagen Membrane for Bone Regeneration.

Natural extracellular matrix (ECM) collagen membranes are frequently used for bone regeneration procedures. Some disadvantages, such as rapid degradation and questionable mechanical properties, limit their clinical use. These membranes have a heterologous origin and may proceed from different tissues. Biomineralization is a process in which hydroxyapatite deposits mainly in collagen fibrils of the matrices. However, when this deposition occurs on the ECM, its mechanical properties are increased, facilitating bone regeneration. The objective of the present research is to ascertain if different membranes from distinct origins may undergo biomineralization. Nanomechanical properties, scanning electron (SEM) and multiphoton (MP) microscopy imaging were performed in three commercially available ECMs before and after immersion in simulated body fluid solution for 7 and 21 d. The matrices coming from porcine dermis increased their nanomechanical properties and they showed considerable mineralization after 21 d, as observed in structural changes detected through SEM and MP microscopy. It is hypothesized that the more abundant crosslinking and the presence of elastin fibers within this membrane explains the encountered favorable behavior.

Electreted Sandwich Membranes with Persistent Electrical Stimulation for Enhanced Bone Regeneration.

Physiologically relevant electrical microenvironments play an indispensable role in manipulating bone metabolism. Although implanted biomaterials that simulate the electrical properties of natural tissues using conductive or piezoelectric materials have been introduced in the field of bone regeneration, the application of electret materials to provide stable and persistent electrical stimulation has rarely been studied in biomaterial design. In this study, a silicon dioxide electret-incorporated poly(dimethylsiloxane) (SiO2/PDMS) composite electroactive membrane was designed and fabricated to explore its bone regeneration efficacy. SiO2 electrets were homogeneously dispersed in the PDMS matrix, and sandwich-like composite membranes were fabricated using a facile layer-by-layer blade-coating method. Following the encapsulation, electret polarization was conducted to obtain the electreted composite membranes. The surface potential of the composite membrane could be adjusted to a bone-promotive biopotential by tuning the electret concentration, and the prepared membranes exhibited favorable electrical stability during an observation period of up to 42 days. In vitro biological experiments indicated that the electreted SiO2/PDMS membrane promoted cellular activity and osteogenic differentiation of mesenchymal stem cells. In vivo, the electreted composite membrane remarkably facilitated bone regeneration through persistent endogenous electrical stimulation. These findings suggest that the electreted sandwich-like membranes, which maintain a stable and physiological electrical microenvironment, are promising candidates for enhancing bone regeneration.

The construction of a self-assembled coating with chitosan-grafted reduced graphene oxide on porous calcium polyphosphate scaffolds for bone tissue engineering

Bone regeneration in large bone defects remains one of the major challenges in orthopedic surgery. Calcium polyphosphate (CPP) scaffolds possess excellent biocompatibility and exhibits good bone ingrowth. However, the present CPP scaffolds lack enough osteoinductive activity to facilitate bone regeneration at bone defects that exceed the critical size threshold. To endow CPP scaffolds with improved osteoinductive activity for better bone regeneration, in this study, a self-assembled coating with chitosan-grafted reduced graphene oxide (CS-rGO) sheets was successfully constructed onto the surface of CPP scaffolds through strong electrostatic interaction and hydrogen bonds. Our results showed that the obtained CPP/CS-rGO composite scaffolds exhibited highly improved biomineralization and considerable antibacterial activity. More importantly, CPP/CS-rGO composite scaffolds could drive osteogenic differentiation of BMSCs and significantly up-regulate the expression of osteogenesis-related proteins in vitro. Meanwhile, the CS-rGO coating could inhibit aseptic loosening and improve interfacial osseointegration through stimulating bone marrow mesenchymal stem cells (BMSCs) to secrete more osteoprotegerin (OPG) and lesser receptor activator of nuclear factor-κB ligand (RANKL). Overall, the CS-rGO coating adjusts CPP scaffolds’ biological environment interface and endows CPP scaffolds with more bioactivity.

Mussel-inspired multifunctional surface through promoting osteogenesis and inhibiting osteoclastogenesis to facilitate bone regeneration

Osteogenesis and osteoclastogenesis are closely associated during the bone regeneration process. The development of multifunctional bone repair scaffolds with dual therapeutic actions (pro-osteogenesis and anti-osteoclastogenesis) is still a challenging task for bone tissue engineering applications. Herein, through a facile surface coating process, mussel-inspired polydopamine (PDA) is adhered to the surface of a biocompatible porous scaffold followed by the immobilization of a small-molecule activator (LYN-1604 (LYN)) and the subsequent in situ coprecipitation of hydroxyapatite (HA) nanocrystals. PDA, acting as an intermediate bridge, can provide strong LYN immobilization and biomineralization ability, while LYN targets osteoclast precursor cells to inhibit osteoclastic differentiation and functional activity, which endows LYN/HA-coated hybrid scaffolds with robust anti-osteoclastogenesis ability. Due to the synergistic effects of the LYN and HA components, the obtained three-dimensional hybrid scaffolds exhibited the dual effects of osteoclastic inhibition and osteogenic stimulation, thereby promoting bone tissue repair. Systematic characterization experiments confirmed the successful fabrication of LYN/HA-coated hybrid scaffolds, which exhibited an interconnected porous structure with nanoroughened surface topography, favorable hydrophilicity, and improved mechanical properties, as well as the sustained sequential release of LYN and Ca ions. In vitro experiments demonstrated that LYN/HA-coated hybrid scaffolds possessed satisfactory cytocompatibility, effectively promoting cell adhesion, spreading, proliferation, alkaline phosphatase activity, matrix mineralization, and osteogenesis-related gene and protein secretion, as well as stimulating angiogenic differentiation of endothelial cells. In addition to osteogenesis, the engineered scaffolds also significantly reduced osteoclastogenesis, such as tartrate-resistant acid phosphatase activity, F-actin ring staining, and osteoclastogenesis-related gene and protein secretion. More importantly, in a rat calvarial defect model, the newly developed hybrid scaffolds significantly promoted bone repair and regeneration. Microcomputed tomography, histological, and immunohistochemical analyses all revealed that the LYN/HA-coated hybrid scaffolds possessed not only reliable biosafety but also excellent osteogenesis-inducing and osteoclastogenesis-inhibiting effects, resulting in faster and higher-quality bone tissue regeneration. Taken together, this study offers a powerful and promising strategy to construct multifunctional nanocomposite scaffolds by promoting osteo/angiogenesis and suppressing osteoclastogenesis to accelerate bone regeneration.