Small molecules modified biomimetic gelatin/hydroxyapatite nanofibers constructing an ideal osteogenic microenvironment with significantly enhanced cranial bone formation

Immunoregulation in Skull Defect Repair with a Smart Hydrogel Loaded with Mesoporous Bioactive Glasses

Skull defect repair is a complex and critical medical challenge, and there is an urgent need to develop multifunctional tissue engineering scaffolds for skull regeneration. The success of bone tissue engineering depends on the construction of scaffolds that can regulate the immune microenvironment of bone regeneration and mimic the liquid crystal and viscoelastic properties of natural bone extracellular matrix. Hence, a smart hydrogel (PEGDA5/AM15/CLC-BMP-4@MBG) with good biocompatibility and the ability to modulate the wound immune microenvironment has been developed for the repair of skull defects. The hydrogel consists of chitin liquid crystal hydrogel (PEGDA5/AM15/CLC) and mesoporous bioactive glasses (MBGs) loaded with bone morphogenetic protein-4 (BMP-4). The liquid crystal hydrogel not only offers the necessary biological support and mechanical properties but also maintains the stability of the liquid crystal state, facilitating adhesion and regeneration of surrounding bone tissue. In addition, BMP-4@MBG intelligently regulates the release rate of BMP-4 in response to changes in wound microenvironment, thus effectively promoting the transformation of macrophages from M1 to M2 macrophages. At the same time, Ca2+ and Si4+ released by MBG degradation and BMP-4 synergically promote bone repair process. The PEGDA5/AM15/CLC-BMP-4@MBG hydrogel shows excellent immunomodulatory and osteogenic properties of bone microenvironment and is a promising scaffold material for bone tissue engineering.

A variable mineralization time and solution concentration intervene in the microstructure of biomimetic mineralized collagen and potential osteogenic microenvironment

The absence of a conducive bone formation microenvironment between fractured ends poses a significant challenge in repairing large bone defects. A promising solution is to construct a bone formation microenvironment that mimics natural bone tissue. Biomimetic mineralized collagen possesses a chemical composition and microstructure highly similar to the natural bone matrix, making it an ideal biomimetic bone substitute material. The microstructure of biomimetic mineralized collagen is influenced by various factors, and its biomineralization and microstructure, in turn, affect its physicochemical properties and biological activity. We aimed to utilize mineralization time and solution concentration as variables and employed the polymer-induced liquid precursor strategy to fabricate mineralized collagen with diverse microstructures, to shed light on how mineralization parameters impact the material microstructure and physicochemical properties. We also investigated the influence of microstructure and physicochemical properties on cell biocompatibility and the bone-forming microenvironment. Through comprehensive characterization, we examined the physical and chemical properties of I-EMC under various mineralization conditions and assessed the in vitro and in vivo biocompatibility and osteogenic performance. By investigating the relationship between mineralization parameters, material physicochemical properties, and osteogenic performance, we revealed how microstructures influence cellular behaviors like biocompatibility and osteogenic microenvironment. Encouragingly, mineralization solutions with varying concentrations, stabilized by polyacrylic acid, successfully produced intrafibrillar and extrafibrillar mineralized collagen. Compared to non-mineralized collagen, all mineralized samples demonstrated improved bone-forming performance. Notably, samples prepared with a 1× mineralization solution exhibited relatively smooth surfaces with even mineralization. Extending the mineralization time enhanced the degree of mineralization and osteogenic performance. Conversely, samples prepared with a 2× mineralization solution had rough surfaces with large calcium phosphate particles, indicating non-uniform mineralization. Overall, our research advances the potential for commercial production of mineralized collagen protein products, characterized by dual biomimetic properties, and their application in treating various types of bone defects.

Bioactive Scaffolds as a Promising Alternative for Enhancing Critical-Size Bone Defect Regeneration in the Craniomaxillofacial Region

Reconstruction of critical-size bone defects (CSDs) in the craniomaxillofacial (CMF) region remains challenging. Scaffold-based bone-engineered constructs have been proposed as an alternative to the classical treatments made with autografts and allografts. Scaffolds, a key component of engineered constructs, have been traditionally viewed as biologically passive temporary replacements of deficient bone lacking intrinsic cues to promote osteogenesis. Nowadays, scaffolds are functionalized, giving rise to bioactive scaffolds promoting bone regeneration more effectively than conventional counterparts. This review focuses on the three approaches most used to bioactivate scaffolds: (1) conferring microarchitectural designs or surface nanotopography; (2) loading bioactive molecules; and (3) seeding stem cells on scaffolds, providing relevant examples of in vivo (preclinical and clinical) studies where these methods are employed to enhance CSDs healing in the CMF region. From these, adding bioactive molecules (specifically bone morphogenetic proteins or BMPs) to scaffolds has been the most explored to bioactivate scaffolds. Nevertheless, the downsides of grafting BMP-loaded scaffolds in patients have limited its successful translation into clinics. Despite these drawbacks, scaffolds containing safer, cheaper, and more effective bioactive molecules, combined with stem cells and topographical cues, remain a promising alternative for clinical use to treat CSDs in the CMF complex replacing autografts and allografts.

Application of 3D- printed hydrogels in wound healing and regenerative medicine

Hydrogels are three-dimensional polymer networks with hydrophilic properties. The modifiable properties of hydrogels and the structure resembling living tissue allow their versatile application. Therefore, increasing attention is focused on the use of hydrogels as bioinks for three-dimensional (3D) printing in tissue engineering. Bioprinting involves the fabrication of complex structures from several types of materials, cells, and bioactive compounds. Stem cells (SC), such as mesenchymal stromal cells (MSCs) are frequently employed in 3D constructs. SCs have desirable biological properties such as the ability to differentiate into various types of tissue and high proliferative capacity. Encapsulating SCs in 3D hydrogel constructs enhances their reparative abilities and improves the likelihood of reaching target tissues. In addition, created constructs can simulate the tissue environment and mimic biological signals. Importantly, the immunogenicity of scaffolds is minimized through the use of patient-specific cells and the biocompatibility and biodegradability of the employed biopolymers. Regenerative medicine is taking advantage of the aforementioned capabilities in regenerating various tissues- muscle, bones, nerves, heart, skin, and cartilage.

Novel PVAMA/GelMA aerogels prepared by liquid-phase collection of photoinitiated polymerisation: injectable and flowable low-density 3D scaffolds for bone regeneration

Nanofibrous scaffolds, which are morphologically/structurally similar to native extracellular matrix, are ideal biomaterials for tissue engineering and regenerative medicine. However, the use of traditional electrospinning techniques to produce three-dimensional (3D) nanofibrous scaffolds with desired structural properties presents difficulty. To address this challenge, we prepared a novel liquid-phase-collected photoinitiated polymerised aerogel 3D scaffold (LPPI-AG) using the thermally induced (nanofiber) self-aggregation method after liquid-phase electrospinning of the hydroxyapatite-doped methacrylated polyvinyl alcohol/methacrylated gelatine solution obtained by photoinitiated polymerisation. The fabricated aerogel scaffolds had a high porosity of approximately 99.01% ± 0.40% and an interconnected network structure with pore sizes ranging from submicron to ∼300 μm. The new aerogel rapidly became flowable when exposed to a solution, and it can fill gaps and repair gap edges effectively and be loaded with nutrients and growth factors that promote bone growth for bone tissue engineering. LPPI-AG scaffolds can considerably promote osteogenic differentiation of bone marrow mesenchymal stem cells in vitro. Furthermore, in vivo studies showed that the LPPI-AG scaffold significantly promoted bone formation in a mouse model of critical-size calvarial defects.

Preparation of hydroxyapatite nanofibers by using ionic liquids as template and application in enhancing hydrogel performance

Introduction: Hydroxyapatite (HAP or HA) nanofibers are very attractive in the field of biomedical engineering. However, templates used for preparing HAP nanofibers are usually hydrophobic molecules, like fatty acids and/or surfactants, which are difficult to remove and potentially toxic. Therefore, it is important to develop a green approach to prepare HAP nanofibers. Methods: Imidazolium-based ionic liquids (ILs) were used as templates to control the crystallization of HAP. The obtained HAP nanofibers were composited into polyvinyl alcohol-sodium alginate (PVA-Alg) hydrogel (HAP@H). The rheological performance, stretching, and compression properties were tested. Scanning electron microscope (SEM), high resolution transmission electron microscope (HRTEM), X-ray diffraction (XRD), Fourier-transform infrared (FT-IR), and differential scanning calorimetry (DSC) were adopted to characterize the morphology, size, crystallographic orientations, and phase of HAP@H. Results: HAP nanofibers with a length of ∼50 μm were harvested. The DSC results proved that water loss temperature increased from 98°C (for pure hydrogel) to 107°C (for HAP@H). Also, HAP@H hydrogel presented much better porous structure, tensile performance, and compressive performance than that of pure hydrogel. Discussion: The morphology, size, and growth direction of HAP could be modulated easily by altering the alkyl chain length of ILs' cations. This is possibly due to face-specific adsorption of imidazolium moieties on HAP nanocrystals. The enhancing performance of HAP@H is probably due to the composited highly oriented HAP nanofibers.

Evaluation of safety and efficacy of the bone marrow mesenchymal stem cell and gelatin-nano-hydroxyapatite combination in canine femoral defect repair

Femoral shaft fracture is a common bone trauma in dogs. The limitation of mesenchymal stem cells in bone defect applications is that the cell suspension cannot be fixed to the bone defect site. In the study, our objective was to substantiate the combined application of canine bone marrow mesenchymal stem cells (cBMSCs) and gelatin-nano-hydroxyapatite (Gel-nHAP) and evaluate its therapeutic effect on bone defect diseases in dogs. Experiments were performed to evaluate the following: (1) the porosity of Gel-nHAP; (2) the adhesion of cBMSCs to Gel-nHAP; and (3) the effect of Gel-nHAP on cBMSC proliferation. The efficacy and safety of the combination of cBMSC and Gel-nHAP in the repair of femoral shaft defects were evaluated in animal experiments. The results showed that Gel-nHAP supported the attachment of cBMSCs and exhibited good biocompatibility. In the animal bone defect repair experiment, significant cortical bone growth was observed in the Gel-nHAP group at week 8 (p < 0.05) and in the cBMSCs-Gel-nHAP group at week 4 (p < 0.01). We demonstrated that Gel-nHAP could promote the repair of bone defects, and the effect of cBMSC-Gel-nHAP on the repair of bone defects was profound.

A Novel Construct of Coral Granules-Poly-L-Lactic Acid Nanomembrane Sandwich Double Stem Cell Sheet Transplantation as Regenerative Therapy of Bone Defect Model

OBJECTIVES

We examined the use of a new approach in nanotechnology and stem cell research as regenerative therapy for bone tissue defects.

MATERIALS AND METHODS

We compared in vitro osteogenic potential of human Wharton jelly mesenchymal stem cells using coral granules and poly-L-lactic acid nanofiber according to proliferation (by cck-8 kit) and osteogenes (runt-related transcription factor 2, alkaline phosphatase, osteonectin) by quantitative reverse transcription-polymerase chain reaction, alkaline phosphatase assay, calcium measurement, and assessment of mineralization by Alizarin red and von Kossa staining. To overcome the limitations of natural coral, we made a modification by packaging the coral granules-human Wharton jelly mesenchymal stem cells by nanomembrane-human Wharton jelly mesenchymal stem cells to form sandwich double cell sheets and compared this hole with other holes (one was filled by human Wharton jelly mesenchymal stem cell suspension, and the other was filled by coral granules saturated with preinduced mesenchymal stem cells) by radiological and histopathological studies for repairing the bone gap.

RESULTS

Collagen-coated poly-L-lactic acid showed higher mRNA levels for all osteogenes (P < .001), higher alkaline phosphatase and calcium content (P < .001), and greater stainability. Our in vivo experiment showed that the holes implanted with sandwich double cell sheet-poly-L-lactic acid coral were completely filled mature compact bone. The holes implanted with human Wharton jelly mesenchymal stem cells alone were filled with immature compact bone. Holes implanted with coral granules-human Wharton jelly mesenchymal stem cells were filled with condensed connective tissue.

CONCLUSIONS

Poly-L-lactic acid nanofiber has greater osteogenic differentiating effect than the coral granules. The new approach of sDCS-PLLA-coral construct proved success for bone regeneration and repairing the bone gap and this may improve the design of tissue constructs for bone tissue regenerative therapy.

Characterization of a bioscaffold containing polysaccharide acemannan and native collagen for pulp tissue regeneration

Dental pulp regeneration exploits tissue engineering concepts using stem cells/scaffolds/growth-factors. Extracted collagen is commonly used as a biomaterial-scaffold due to its biocompatibility/biodegradability and mimics the natural extracellular matrix. Adding biomolecules into a collagen-scaffold enhanced pulp regeneration. Acemannan, β-(1-4)-acetylated-polymannose, is a polysaccharide extracted from aloe vera. Acemannan is a regenerative biomaterial. Therefore, acemannan could be a biomolecule in a collagen-scaffold. Here, acemannan and native collagen were obtained and characterized. The AceCol-scaffold's physical properties were investigated using FTIR, SEM, contact angle, swelling, pore size, porosity, compressive modulus, and degradation assays. The AceCol-scaffold's biocompatibility, growth factor secretion, osteogenic protein expression, and calcification were evaluated in vitro. The AceCol-scaffolds demonstrated higher hydrophilicity, swelling, porosity, and larger pore size than the collagen scaffolds (p < 0.05). Better cell-cell and cell-scaffold adhesion, and dentin extracellular matrix protein (BSP/OPN/DSPP) expression were observed in the AceCol-scaffold, however, DSPP expression was not detected in the collagen group. Significantly increased cellular proliferation, VEGF and BMP2 expression, and mineralization were detected in the AceCol-scaffold compared with the collagen-scaffold (p < 0.05). Computer simulation revealed that acemannan's 3D structure changes to bind with collagen. In conclusion, the AceCol-scaffold synergistically provides better physical and biological properties than collagen. The AceCol-scaffold is a promising material for tissue regeneration.

3D-Printed scaffolds based on poly(Trimethylene carbonate), poly(ε-Caprolactone), and β-Tricalcium phosphate

Three-dimensional (3D)-printed scaffolds of biodegradable polymers have been increasingly applied in bone repair and regeneration, which helps avoid the second surgery. PTMC/PCL/TCP composites were made using poly(trimethylene carbonate), poly(ε-caprolactone), and β-tricalcium phosphate. PTMC/PCL/TCP scaffolds were manufactured using a biological 3D printing technique. Furthermore, the properties of PTMC/PCL/TCP scaffolds, such as biodegradation, mechanic properties, drug release, cell cytotoxicity, cell proliferation, and bone repairing capacity, were evaluated. We showed that PTMC/PCL/TCP scaffolds had low cytotoxicity and good biocompatibility, and they also enhanced the proliferation of osteoblast MC3T3-E1 and rBMSC cell lines, which demonstrated improved adhesion, penetration, and proliferation. Moreover, PTMC/PCL/TCP scaffolds can enhance bone induction and regeneration, indicating that they can be used to repair bone defects in vivo.

Electrospun Biomimetic Nanofibrous Scaffolds: A Promising Prospect for Bone Tissue Engineering and Regenerative Medicine

Skeletal-related disorders such as arthritis, bone cancer, osteosarcoma, and osteoarthritis are among the most common reasons for mortality in humans at present. Nanostructured scaffolds have been discovered to be more efficient for bone regeneration than macro/micro-sized scaffolds because they sufficiently permit cell adhesion, proliferation, and chemical transformation. Nanofibrous scaffolds mimicking artificial extracellular matrices provide a natural environment for tissue regeneration owing to their large surface area, high porosity, and appreciable drug loading capacity. Here, we review recent progress and possible future prospective electrospun nanofibrous scaffolds for bone tissue engineering. Electrospun nanofibrous scaffolds have demonstrated promising potential in bone tissue regeneration using a variety of nanomaterials. This review focused on the crucial role of electrospun nanofibrous scaffolds in biological applications, including drug/growth factor delivery to bone tissue regeneration. Natural and synthetic polymeric nanofibrous scaffolds are extensively inspected to regenerate bone tissue. We focused mainly on the significant impact of nanofibrous composite scaffolds on cell adhesion and function, and different composites of organic/inorganic nanoparticles with nanofiber scaffolds. This analysis provides an overview of nanofibrous scaffold-based bone regeneration strategies; however, the same concepts can be applied to other organ and tissue regeneration tactics.

Functionalization of Electrospun Nanofiber for Bone Tissue Engineering

Bone-tissue engineering is an alternative treatment for bone defects with great potential in which scaffold is a critical factor to determine the effect of bone regeneration. Electrospun nanofibers are widely used as scaffolds in the biomedical field for their similarity with the structure of the extracellular matrix (ECM). Their unique characteristics are: larger surface areas, porosity and processability; these make them ideal candidates for bone-tissue engineering. This review briefly introduces bone-tissue engineering and summarizes the materials and methods for electrospining. More importantly, how to functionalize electrospun nanofibers to make them more conducive for bone regeneration is highlighted. Finally, the existing deficiencies of functionalized electrospun nanofibers for promoting osteogenesis are proposed. Such a summary can lay the foundation for the clinical practice of functionalized electrospun nanofibers.

Zingerone stimulates osteoblast differentiation by increasing Smad1/5/9 mediated HO-1 expression in MC3T3-E1 cells and primary mouse calvarial cells

Zingerone (Zin) is a non-volatile compound found mainly in dried ginger. Zingerone increases the expression of osteogenic markers and has antioxidant effects. A previous study showed that zingerone accelerated osteoblast differentiation by suppressing the expression of Smad7, a member of the inhibitory Smad (I-Smad) family. However, it is not known if zingerone can induce osteoblast differentiation by regulating Smad1/5/9, a member of the receptor-regulated Smad (R-Smad) famlily. In addition, osteoblast differentiation induced by Smad1/5/9 mediated increases in the expression of heme oxygenase 1 (HO-1) has not been reported. This study investigated the effects of zingerone on osteoblast differentiation and confirmed the relationship between Smad1/5/9 and HO-1. Zingerone increased the expression of osteogenic genes including Runx2, Dlx5 and OC, and also promoted Smad1/5/9 phosphorylation. Interestingly, HO-1 expression was also elevated by zingerone, and an inhibitor of HO-1 (Sn(IV) protoporphyrin IX dichloride, SnPP) suppressed the zingerone-induced increase in HO-1 expression and expression of osteogenic marker genes such as Dlx5, Runx2, and OC. Protein phosphatase 2A Cα (PP2A Cα, an inhibitor of Smad1/5/9) suppressed the zingerone-induced increase in HO-1 expression and expression of osteogenic marker genes. The zingerone-induced increase in HO-1 lucifeerase activity was suppressed by PP2A Cα. Taken together, our data demonstrate that zingerone promotes osteoblast differentiation by increasing Smad1/5/9 mediated HO-1 expression.

Reinforced Blood-Derived Protein Hydrogels Enable Dual-Level Regulation of Bio-Physiochemical Microenvironments for Personalized Bone Regeneration with Remarkable Enhanced Efficacy

Physiological microenvironment engineering has shown great promise in combating a variety of diseases. Herein, we present the rational design of reinforced and injectable blood-derived protein hydrogels (PDA@SiO₂-PRF) composed of platelet-rich fibrin (PRF), polydopamine (PDA), and SiO₂ nanofibers that can act as dual-level regulators to engineer the microenvironment for personalized bone regeneration with high efficacy. From the biophysical level, PDA@SiO₂-PRF with high stiffness can withstand the external loading and maintaining the space for bone regeneration in bone defects. Particularly, the reinforced structure of PDA@SiO₂-PRF provides bone extracellular matrix (ECM)-like functions to stimulate osteoblast differentiation via Yes-associated protein (YAP) signaling pathway. From the biochemical level, the PDA component in PDA@SiO₂-PRF hinders the fast degradation of PRF to release autologous growth factors in a sustained manner, providing sustained osteogenesis capacity. Overall, the present study offers a dual-level strategy for personalized bone regeneration by engineering the biophysiochemical microenvironment to realize enhanced osteogenesis efficacy.

Osteogenic Induction with Silicon Hydroxyapatite Using Modified Autologous Adipose Tissue-Derived Stromal Vascular Fraction: In Vitro and Qualitative Histomorphometric Analysis

Large bone defects requiring invasive surgical procedures have long been a problem for orthopedic surgeons. Despite the use of autologous bone grafting, satisfactory results are often not achieved due to associated limitations. Biomaterials are viable alternatives and have lately been used in association with Stromal Vascular Fraction (SVF), stem cells, and signaling factors for bone tissue engineering (BTE). The objective of the current study was to assess the biocompatibility of Silicon Hydroxyapatite (Si-HA) and to improve osteogenic potential by using autologous adipose-derived SVF with Si-HA in a rabbit bone defect model. Si-HA granules synthesized using a wet precipitation method were used. They were characterized using scanning electron microscopy (SEM), Fourier transform infrared (FTIR), and X-ray diffraction (XRD). A hemolysis assay was used to assess the hemolytic effects of Si-HA, while cell viability was assessed through Alamar Blue assay using MC3T3 mouse osteoblasts. The osteogenic potential of Si-HA both alone and with enzymatically/non-enzymatically-derived SVF (modified) was performed by implantation in a rabbit tibia model followed by histomorphometric analysis and SEM of dissected bone after six weeks. The results showed that Si-HA granules were microporous and phase pure and that the addition of Silicon did not influence Si-HA phase composition. Si-HA granules were found to be non-hemolytic on the hemolysis assay and non-toxic to MC3T3 mouse osteoblasts on the Alamar Blue assay. Six weeks following implantation Si-HA showed high biocompatibility, with increased bone formation in all groups compared to control. Histologically more mature bone was formed in the Si-HA implanted along with non-enzymatically-derived modified SVF. Bone formation was observed on and around Si-HA, reflecting osseointegration. In conclusion, Si-HA is osteoconductive and promotes osteogenesis, and its use with SVF enhances osteogenesis.

Chitosan in association with osteogenic factors as a cell-homing platform for dentin regeneration: Analysis in a pulp-in-a-chip model

OBJECTIVE

In this paper we propose the association of β-glycerophosphate (βGP) and calcium-hydroxide with chitosan (CH) to formulate a porous bioactive scaffold suitable as a cell-homing platform for dentin regeneration.

METHODS

Calcium hydroxide and βGP solutions were incorporated into chitosan to modulate scaffold architecture and composition by a phase separation technique. Architecture, chemical composition, and degradability were evaluated, and biological characterizations were performed by the seeding of dental pulp cells (DPCs) onto scaffolds, or by cultivating them in contact with leachable components (extracts), to determine cytocompatibility and odontoblastic differentiation. Cell-free scaffolds were then positioned in intimate contact with a 3D culture of DPCs in a pulp-in-a-chip platform under simulated pulp pressure. Cell mobilization and odontoblastic marker expression were evaluated. Deposition of mineralized matrix was assessed in direct contact with dentin, in the absence of osteogenic factors.

RESULTS

Incorporation of calcium hydroxide and βGP generated a stable porous chitosan scaffold containing Ca-P nanoglobule topography (CH-Ca-βGP), which favored cell viability, alkaline phosphatase activity, and mineralized matrix deposition by cells seeded onto the scaffold structure and at a distance. The pulp-in-a-chip assay denoted its chemotactic and bioactive potential, since dentin sialoprotein-positive DPCs from 3D culture adhered to CH-Ca-βGP more than to plain chitosan. The higher deposition of mineralized matrix onto the scaffold and surrounding dentin was also observed.

SIGNIFICANCE

A CH-Ca-βGP scaffold creates a microenvironment capable of mobilizing DPC migration toward its structure, harnessing the odontogenic potential and culminating in the expression of a highly mineralizing phenotype, key factors for a cell-homing strategy.

Biodegradable 3D Printed Scaffolds of Modified Poly (Trimethylene Carbonate) Composite Materials with Poly (L-Lactic Acid) and Hydroxyapatite for Bone Regeneration

Biodegradable scaffolds based on biomedical polymeric materials have attracted wide interest in bone transplantation for clinical treatment for bone defects without a second operation. The composite materials of poly(trimethylene carbonate), poly(L-lactic acid), and hydroxyapatite (PTMC/PLA/HA and PTMC/HA) were prepared by the modification and blending of PTMC with PLA and HA, respectively. The PTMC/PLA/HA and PTMC/HA scaffolds were further prepared by additive manufacturing using the biological 3D printing method using the PTMC/PLA/HA and PTMC/HA composite materials, respectively. These scaffolds were also characterized by Fourier transform infrared spectroscopy (FT-IR), gel permeation chromatography (GPC), automatic contact-angle, scanning electronic micrographs (SEM), diffraction of X-rays (XRD), differential scanning calorimetry (DSC), and thermogravimetry (TG). Subsequently, their properties, such as mechanical, biodegradation, cell cytotoxicity, cell compatibility in vitro, and proliferation/differentiation assay in vivo, were also investigated. Experiment results indicated that PTMC/PLA/HA and PTMC/HA scaffolds possessed low toxicity, good biodegradability, and good biocompatibility and then enhanced the cell multiplication ability of osteoblast cells (MC3T3-E1). Moreover, PTMC/PLA/HA and PTMC/HA scaffolds enhanced the adhesion and proliferation of MC3T3-E1 cells and enabled the bone cell proliferation and induction of bone tissue formation. Therefore, these composite materials can be used as potential biomaterials for bone repatriation and tissue engineering.

Local dual delivery therapeutic strategies: Using biomaterials for advanced bone tissue regeneration

Bone development is a complex process involving a vast number of growth factors and chemical substances. These factors include transforming growth factor-beta, platelet-derived growth factor, insulin-like growth factor, and most importantly, the bone morphogenetic protein, which exhibits excellent therapeutic value in bone repair. However, the spatial-temporal relationship in the expression of these factors during bone formation makes the bone repair a more complicated process to address. Thus, using a single therapeutic agent to address bone formation does not seem to provide a clinically effective option. Conversely, a dual delivery approach facilitating the co-delivery of agents has proved to be a dynamic alternative since such a strategy can provide more efficient spatial-temporal action. Such delivery systems can smartly target more than one pathway or differentiation lineage and thus offer more efficient bone regeneration. This review discusses various dual delivery strategies reported in the literature employed to achieve improved bone regeneration. These include concurrent use of different therapeutic agents (including growth factors and drugs), enhancing bone formation and cell recruitment, and improving the efficiency of bone healing.

Graphene and its Derivatives for Bone Tissue Engineering: In Vitro and In Vivo Evaluation of Graphene-Based Scaffolds, Membranes and Coatings

Bone regeneration or replacement has been proved to be one of the most effective methods available for the treatment of bone defects caused by different musculoskeletal disorders. However, the great contradiction between the large demand for clinical therapies and the insufficiency and deficiency of natural bone grafts has led to an urgent need for the development of synthetic bone graft substitutes. Bone tissue engineering has shown great potential in the construction of desired bone grafts, despite the many challenges that remain to be faced before safe and reliable clinical applications can be achieved. Graphene, with outstanding physical, chemical and biological properties, is considered a highly promising material for ideal bone regeneration and has attracted broad attention. In this review, we provide an introduction to the properties of graphene and its derivatives. In addition, based on the analysis of bone regeneration processes, interesting findings of graphene-based materials in bone regenerative medicine are analyzed, with special emphasis on their applications as scaffolds, membranes, and coatings in bone tissue engineering. Finally, the advantages, challenges, and future prospects of their application in bone regenerative medicine are discussed.

An excellent antibacterial and high self-adhesive hydrogel can promote wound fully healing driven by its shrinkage under NIR

The lacks of antibacterial properties, low adhesion and delayed wound healing of the hydrogel wound dressings limit their applications in wound treatment. To resolve these, a novel hydrogel composed of polydopamine (PDA), Ag and graphene oxide (GO) is fabricated for wound dressing via the chemical crosslinking of N-isopropylacrylamide (NIPAM) and N,N'-methylene bisacrylamide (BIS). The prepared hydrogel containing PDA@Ag5GO1 (Ag5GO1 denotes the mass ratio between Ag and GO is 5:1) exhibits effective antibacterial properties and high inhibition rate against E. coli and S. aureus. It shows high adhesion ability to various substrate materials, implying a simpler method to the wound obtained by self-fixing rather than suturing. More important, it can produce strong contractility under the irradiation of near-infrared light (NIR), exerting a centripetal force that helps accelerate wound healing. Thus, the hydrogel containing a high concentration PDA@Ag5GO1 irradiated by NIR can completely repair the wound defect (1.0 × 1.0 cm²) within 15 days, the wound healing rate can reach 100%, which was far higher than other groups. Taken together, the new hydrogel with excellent antibacterial, high adhesion and strong contractility will subvert the traditional treatment methods on wound defect, extending its new application range in wound dressing.

3D Printed Multi-Functional Scaffolds Based on Poly(ε-Caprolactone) and Hydroxyapatite Composites

3D Printed biodegradable polymeric scaffolds are critical to repair a bone defect, which can provide the individual porous and network microenvironments for cell attachment and bone tissue regeneration. Biodegradable PCL/HA composites were prepared with the blending of poly(ε-caprolactone) (PCL) and hydroxyapatite nanoparticles (HA). Subsequently, the PCL/HA scaffolds were produced by the melting deposition-forming method using PCL/HA composites as the raw materials in this work. Through a serial of in vitro assessments, it was found that the PCL/HA composites possessed good biodegradability, low cell cytotoxicity, and good biocompatibility, which can improve the cell proliferation of osteoblast cells MC3T3-E1. Meanwhile, in vivo experiments were carried out for the rats with skull defects and rabbits with bone defects. It was observed that the PCL/HA scaffolds allowed the adhesion and penetration of bone cells, which enabled the growth of bone cells and bone tissue regeneration. With a composite design to load an anticancer drug (doxorubicin, DOX) and achieve sustained drug release performance, the multifunctional 3D printed PCL/HA/DOX scaffolds can enhance bone repair and be expected to inhibit probably the tumor cells after malignant bone tumor resection. Therefore, this work signifies that PCL/HA composites can be used as the potential biodegradable scaffolds for bone repairing.

Current and Advanced Nanomaterials in Dentistry as Regeneration Agents: An Update

In modern dentistry, nanomaterials have strengthened their foothold among tissue engineering strategies for treating bone and dental defects due to a variety of reasons, including trauma and tumors. Besides their finest physiochemical features, the biomimetic characteristics of nanomaterials promote cell growth and stimulate tissue regeneration. The single units of these chemical substances are small-sized particles, usually between 1 to 100 nm, in an unbound state. This unbound state allows particles to constitute aggregates with one or more external dimensions and provide a high surface area. Nanomaterials have brought advances in regenerative dentistry from the laboratory to clinical practice. They are particularly used for creating novel biomimetic nanostructures for cell regeneration, targeted treatment, diagnostics, imaging, and the production of dental materials. In regenerative dentistry, nanostructured matrices and scaffolds help control cell differentiation better. Nanomaterials recapitulate the natural dental architecture and structure and form functional tissues better compared to the conventional autologous and allogenic tissues or alloplastic materials. The reason is that novel nanostructures provide an improved platform for supporting and regulating cell proliferation, differentiation, and migration. In restorative dentistry, nanomaterials are widely used in constructing nanocomposite resins, bonding agents, endodontic sealants, coating materials, and bioceramics. They are also used for making daily dental hygiene products such as mouth rinses. The present article classifies nanostructures and nanocarriers in addition to reviewing their design and applications for bone and dental regeneration.

Shapable bulk agarose-gelatine-hydroxyapatite-minocycline nanocomposite fabricated using a mineralising system aided with electrophoresis for bone tissue regeneration

To develop a shapable bulk antibacterial nanocomposite biomaterial for bone regeneration. A bulk agarose-gelatine hydrogel was through mineralised using a hydrogel mineralising system aided with electrophoresis, and the mineralised hydrogel was loaded with minocycline to obtain the agarose-gelatine-hydroxyapatite-minocycline nanocomposite. The nanocomposite had a large BET surface area of 44.4518m2/g and a high porosity of 76.9%. Hydroxyapatite crystals were well developed in the hydrogel matrix and exhibited a hybrid structure of microscale and nanoscale motifs. The addition of minocycline resulted in a continuous antibiotic release, inhibiting the growth of Staphylococcus aureus over two weeks in vitro. Exposed to rabbit bone marrow mesenchymal stem cells, the nanocomposite revealed good cytocompatibility in vitro. Furthermore, the biomaterial could effectively enhance the bone regeneration in a critical-size rabbit cranial defect model in vivo. These findings depicted that the nanocomposite, with good biocompatibility and good antibacterial property, is a promising candidate for future clinical application in bone tissue engineering or as a prospective bone replacement biomaterial.

Osteogenic effects of the bioactive small molecules and minerals in the scaffold-based bone tissue engineering

Reconstruction of the damaged bone is a striking challenge in the medical field. The bone grafts as a current treatment is associated with inherent limitations; hence, the bone tissue engineering as an alternative therapeutic approach has been considered in the recent decades. Bone tissue engineering aims at replacing the lost tissue and restoring its function by recapitulating the natural regeneration process. Concerted participation and combination of the biocompatible materials, osteoprogenitor/ stem cells and bioactive factors closely mimic the bone microenvironment. The bioactive factors regulate the cell behavior and they induce the stem cells to osteogenic differentiation by activating specific signaling cascades. Growth factors (GFs) are the most important bioactive molecules and mediators of the natural bone repair process. Although these soluble factors have approved applications in the bone regeneration, however, there are several limitations such as the instability, high dose requirements, and serious side effects which could restrict their clinical usage. Alternatively, a new generation of bioactive molecules with the osteogenic properties are used. The non-peptide organic or inorganic molecules are physiologically stable and non-immunogenic due to their small size. Many of them are obtained from the natural resources and some are synthesized through the chemical methods. As a result, these molecules have been introduced as the cost-effective osteogenic agents in the bone tissue regeneration. In this paper, three groups of these bioactive agents including the organic small molecules, minerals and metallic nanoparticles have been investigated, considering their function in accelerating the bone regeneration. We review the recent in vitro and in vivo studies that utilized the osteogenic molecules to promote the bone formation in the scaffold-based bone tissue engineering systems.

Advances of nanomaterial applications in oral and maxillofacial tissue regeneration and disease treatment

Using bioactive nanomaterials in clinical treatment has been widely aroused. Nanomaterials provide substantial improvements in the prevention and treatment of oral and maxillofacial diseases. This review aims to discuss new progresses in nanomaterials applied to oral and maxillofacial tissue regeneration and disease treatment, focusing on the use of nanomaterials in improving the quality of oral and maxillofacial healthcare, and discuss the perspectives of research in this arena. Details are provided on the tissue regeneration, wound healing, angiogenesis, remineralization, antitumor, and antibacterial regulation properties of nanomaterials including polymers, micelles, dendrimers, liposomes, nanocapsules, nanoparticles and nanostructured scaffolds, etc. Clinical applications of nanomaterials as nanocomposites, dental implants, mouthwashes, biomimetic dental materials, and factors that may interact with nanomaterials behaviors and bioactivities in oral cavity are addressed as well. In the last section, the clinical safety concerns of their usage as dental materials are updated, and the key knowledge gaps for future research with some recommendation are discussed. This article is categorized under: Implantable Materials and Surgical Technologies > Nanomaterials and Implants Implantable Materials and Surgical Technologies > Nanotechnology in Tissue Repair and Replacement.

Autophagy was involved in tumor necrosis factor-α-inhibited osteogenic differentiation of murine calvarial osteoblasts through Wnt/β-catenin pathway

Periodontitis is an inflammatory disease with a high incidence characterized by irreversible destruction of alveolar bone. This study aimed to investigate the effect of tumor necrosis factor-α (TNF-α) on osteogenic differentiation and its molecular mechanism. TNF-α inhibited osteogenic differentiation as revealed by the lower accumulation of osteoblastic genes like runt-related transcription factor (Runx2), alkaline phosphatase (ALP), osteoprotegerin (OPG), and osteocalcin (OCN). Moreover, TNF-α down-regulated the expressions of LC3II, ATG7, and beclin 1 (BECN1); suggesting that autophagy was inhibited during the process of osteogenic differentiation. Consistently, Wnt/β-catenin signaling pathway members such as low-density lipoprotein receptor-related protein 5 (LRP5), β-catenin, and phosphorylated-β-catenin (p-β-catenin) were reduced by TNF-α. Furthermore, the inhibitory effect of TNF-α on osteogenic differentiation and the Wnt/β-catenin signaling pathway could be abated by autophagy inducers but exacerbated by autophagy inhibitors. The most intriguing finding of all was that TNF-α inhibited osteoblastic differentiation and the Wnt/β-catenin signaling pathway by down-regulating autophagy, and autophagy positively regulated the Wnt/β-catenin pathway and thus influenced osteoblastic differentiation. Our study provides a theoretical basis for autophagy-inducer therapy for the alveolar bone loss caused by periodontitis.

Injectable thermosensitive chitosan/gelatin-based hydrogel carried erythropoietin to effectively enhance maxillary sinus floor augmentation in vivo

OBJECTIVE

Maxillary sinus floor augmentation (MSFA) is commonly used to increase the alveolar bone height in the posterior maxilla before implant placement. In the present study, we evaluated if the injectable thermosensitive chitosan/β-sodium glycerophosphate disodium salt hydrate/gelatin (CS/GP/GA) hydrogel carried erythropoietin (EPO) could enhance the new bone formation for MSFA in vivo.

METHODS

EPO-CS/GP/GA hydrogel was prepared by ionic crosslinking. Then, characteristics of EPO-CS/GP/GA were evaluated by morphology, injectable property and pH on the gelling time (GT). The release profile of EPO was evaluated by enzyme linked immunosorbent assay (ELISA), and effects of EPO on proliferation and osteoblastic differentiation of bone marrow stromal cells (BMSC) were analyzed by 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyl tetrazolium bromide (MTT) and reverse transcription quantitative real-time PCR (RT-qPCR), respectively. Finally, EPO-CS/GP/GA was injected into the maxillary sinus floor of the rabbit to test the potential application for MSFA.

RESULTS

Results showed that GT was decreased with the increase of pH value. The GT was 110±15s at pH 7.0. SEM images showed that the CS/GP/GA hydrogel had a sponge network structure. Results from ELISA assay revealed that the cumulative release of EPO from the EPO-CS/GP/GA hydrogel reached 67% at 4h, and 94% at 15 days. MTT assay showed that EPO within EPO-CS/GP/GA hydrogel could significantly promote proliferation of BMSCs compared to control group (p<0.001) . Results of RT-qPCR assays demonstrated that the expression of Sp7, Runx2, Col I and Alp were significantly increased from EPO-CS/GP/GA group compared to control group on day 14 (p<0.001). Importantly, EPO-CS/GP/GA hydrogel could significantly induce bone formation (81.98mm³) compared with control group (43.11mm³) after 12 weeks post-implantation in vivo. The calculation of thickness of mesenchymal condensation indicated that thickness of mesenchymal condensation was significantly increased from EPO-CS/GP/GA group (∼121.4μm) compared to control group (∼37μm) resulting in enhancing intramembranous ossification.

SIGNIFICANCE

The EPO-CS/GP/GA hydrogel provides a novel strategy for MSFA with a minimally invasive way.

Osteogenic potential of Zn2+-passivated carbon dots for bone regeneration in vivo

Carbon dots are a new kind of nanomaterial which has great potential in biomedical applications. Previously, we have synthesized novel Zn2+-passivated carbon dots (Zn-CDs) which showed good osteogenic activity in vitro. In this study, we will further investigate the osteogenic effects of Zn-CDs in vivo which is essential before their clinical use. Herein, Zn2+-passivated carbon dots (Zn-CDs) are prepared and characterized as previously reported. Then, the optimum dose for inducing osteoblasts was evaluated by MTS assay, intracellular reactive oxygen species (ROS) detection, alkaline phosphatase (ALP) activity test and alizarin red staining in vitro. Finally, a 5 mm diameter calvarial bone defect model was created in rats and Zn-CDs were applied for repairing the critical bone defect. It was shown that zinc gluconate (Zn-G) and Zn-CDs promoted the survival of bone marrow stromal cells (BMSCs) when the zinc ion concentration was 10-4 mol L-1 (Zn-G: 45.6 μg mL-1) and 10-5 mol L-1 (Zn-CDs: 300 μg mL-1) or below respectively. With regard to the osteogenic capability, the ALP activity induced by Zn-CDs was significantly higher than that by Zn-G. Besides, the results of alizarin red staining showed that the area of calcified nodules was increased in a dose-dependent manner in the Zn-CD group. Moreover, there were more calcium nodules in the Zn-CD group than in the Zn-G group at the same concentration of Zn2+ (10-5 mol L-1). Taken together, Zn-CDs achieved the highest osteogenic effect at the concentration of 10-5 mol L-1 without affecting cell proliferation in long-term stimulation. Importantly, the volume of new bone formation in the Zn-CD group (6.66 ± 1.25 mm3) was twice higher than that in the control group (3.33 ± 0.94 mm3) in vivo. Further histological evaluation confirmed the markedly new bone formation at 8 weeks in the Zn-CD group. The in vitro and in vivo experiments revealed that Zn-CDs could be a new predictable nanomaterial with good biocompatibility and fluorescence properties for guiding bone regeneration.

Promising Recent Strategies with Potential Clinical Translational Value to Combat Antibacterial Resistant Surge

Multiple drug resistance (MDR) for the treatment of bacterial infection has been a significant challenge since the beginning of the 21st century. Many of the small molecule-based antibiotic treatments have failed on numerous occasions due to a surge in MDR, which has claimed millions of lives worldwide. Small particles (SPs) consisting of metal, polymer or carbon nanoparticles (NPs) of different sizes, shapes and forms have shown considerable antibacterial effect over the past two decades. Unlike the classical small-molecule antibiotics, the small particles are less exposed so far to the bacteria to trigger a resistance mechanism, and hence have higher chances of fighting the challenge of the MDR process. Until recently, there has been limited progress of clinical treatments using NPs, despite ample reports of in vitro antibacterial efficacy. In this review, we discuss some recent and unconventional strategies that have explored the antibacterial efficacy of these small particles, alone and in combination with classical small molecules in vivo, and demonstrate possibilities that are favorable for clinical translations in near future.