Quercetin Inlaid Silk Fibroin/Hydroxyapatite Scaffold Promotes Enhanced Osteogenesis

Preparation of SF-gel-CS-Hap bionic biphasic porous scaffolds and evaluation of physical, mechanical and biological properties

Objective: Full-thickness cartilage defect are usually accompanied by subchondral bone damage, which is difficult to self-repair once damaged due to the lack of vascularization and innervation. In this study, a biphasic composite scaffold was developed by combining vacuum freeze-drying and iterative freeze-thawing with gelatin, chitosan, silk fibroin, and hydroxyapatite as the basic materials to explore the feasibility of using them for the repair of total cartilage defects. Methods and Results: Six groups of SF-CS-Gel-nHap porous scaffolds (Hap-0%, Hap-1%, Hap- 2%, Hap-3%, Hap-4%, Hap-5%) were prepared by vacuum freeze-drying and chemical cross-linking using filipin protein (SF), gelatin (Gel), chitosan (CS) and hydroxyapatite (Hap) as the base materials. A series of characterization methods were used to systematically analyze and test the morphological features as well as physical and mechanical properties of the scaffolds. Then a novel bionic biphasic porous scaffold was developed by a combination of freeze-drying and freeze-thawing using the SF-CS-Gel as the cartilage phase and the SF-CS-Gel-2%Hap as the subchondral bone phase. Finally, it was co-cultured with chondrocytes to verify the biological properties of the SF-CS-Gel/SF-CS-Gel-2%Hap bionic biphasic porous composite scaffold in vitro. The results showed that the SF-CS-Gel/SF-CS-Gel-2%Hap biphasic scaffolds had a highly porous mesh structure, with an average pore size of 156.06 ± 42.36 μm in the cartilage phase and 214.38 ± 65.82 μm in the subchondral bone phase. Co-cultured with chondrocytes, the live and dead cells stained, cck-8 growth and proliferation curves showed that the bionic scaffolds had good biocompatibility and cytotoxicity. Cytoskeletal staining showed that the morphology of chondrocytes in the bionic scaffolds could maintain three-dimensional growth as in vivo. Conclusion: The results showed that SF-CS-Gel/SF-CS-Gel-2%Hap biphasic scaffolds have good biocompatibility, biodegradability, stability, appropriate mechanical properties and porosity, and are suitable for repairing articular cartilage and subchondral bone. It is expected to be used as a repair material for articular cartilage in clinical applications.

Silk fibroin/chitosan thiourea hydrogel scaffold with vancomycin and quercetin-loaded PLGA nanoparticles for treating chronic MRSA osteomyelitis in rats

Chronic osteomyelitis presents significant treatment challenges, necessitating an efficient system for infection elimination and bone repair. This study developed a natural hydrogel scaffold using silk fibroin (SF) and chitosan thiourea (CST), incorporating vancomycin (VC) and quercetin (QC) loaded PLGA nanoparticles (NPs) for dual-purpose treatment. SF/CST hydrogel scaffolds exhibited homogeneous porosity and smaller interconnected pore size than pure SF and pure CST hydrogel scaffolds. Optimal PLGA/QC NPs measured 206 nm in size, displayed spherical morphology, had uniform distribution, and achieved 87 % QC loading. The release study showed sustained long-term release of VC and QC from the hydrogel scaffolds for over 20 days. Biocompatibility tests indicated that hydrogel scaffolds promoted osteoblast adhesion without cytotoxicity, with QC-containing scaffolds enhancing osteoblast growth. Antibacterial tests confirmed retained VC activity against methicillin-resistant Staphylococcus aureus (MRSA) in SF/CST. An experimental study assessed the efficacy of the hydrogel scaffolds in a MRSA-infected rat osteomyelitis model. Radiographic scores demonstrated a significant reduction for SF/CST-VC-PLGA/QC NPs compared to control, indicating reduced osteomyelitis effects. Macroscopic evaluations showed notable reductions in gross pathological effects for VC-containing groups. Histopathological assessments revealed significantly lower osteomyelitis scores and higher healing scores in the SF/CST-VC-PLGA/QC NPs, with reduced inflammatory cell infiltration and more organized connective tissue formation. In conclusion, SF/CST-VC-PLGA/QC NPs is an effective dual drug delivery system for osteomyelitis treatment, demonstrating significant antibacterial activity, enhanced bone regeneration, and reduced infection rate.

Quercetin-based biomaterials for enhanced bone regeneration and tissue engineering

Quercetin, a natural flavonoid, has been extensively researched for its potential in promoting bone regeneration and tissue engineering. This review aimed to provide a comprehensive overview of the applications of quercetin-based biomaterials in bone regeneration and tissue engineering. The review discusses several studies that have integrated quercetin into biomaterials such as electrospun fibers, hydrogels, microspheres, and nanoparticles. These biomaterials are engineered to imitate the natural extracellular matrix of bone, creating an environment conducive to cell attachment, growth, and differentiation. The investigations presented emphasize the potential of quercetin-derived biomaterials in improving bone regeneration, decreasing oxidative stress and inflammation, and facilitating bone tissue restoration. These biomaterials have demonstrated the ability to facilitate cell encapsulation, maintain consistent quercetin release patterns, and have been applied in a range of uses such as bone grafts, implants, and tissue engineering scaffolds. Biomaterials derived from quercetin are utilized in the treatment of bone-related disorders, including osteoporosis and bone defects. These materials enhance bone regeneration by providing a scaffold for new bone growth, promoting the development of new bone tissue, and improving the mechanical properties of bone tissue.

Hydroxyapatite/Silk Fibroin Composite Scaffold with a Porous Structure and Mechanical Strength Similar to Cancellous Bone by Electric Field-Induced Gel Technology

Repair and regeneration of bone tissue defects is a multidimensional process that has been highly challenging to date. The artificial bone scaffold materials, which play a core role, still face the conflict that a biofriendly porous structure will reduce the mechanical performance and accelerate degradation. Herein, a multistage porous structured hydroxyapatite (HA)/silk fibroin (SF) composite scaffold (e-HA/SF) was successfully constructed by cleverly utilizing electric field-induced gel technology. The results indicated that the prepared e-HA/SF scaffolds possess biomimetic hierarchical porous structures with a suitable porosity similar to that of cancellous bone. The HA nanocrystals were uniformly encapsulated in the three-dimensional space of the composite scaffold, thus endowing the e-HA/SF composite scaffolds with an enhanced mechanical performance. Notably, the maximum compression stress and Young's modulus of e-HA/SF-2 scaffolds can reach 24.66 ± 0.88 and 28.91 ± 3.19 MPa, respectively, which are equivalent to those of cancellous bone. Such mechanical performance enhancement was previously unattainable through conventional freeze-drying strategies. Moreover, the introduction of bioactive nano-HA can trigger the optimal cell response in both static and dynamic cell culture experiments in vitro. The e-HA/SF composite scaffold developed in this study can better balance the conflict between the porous structure and mechanical and degradation properties of porous scaffolds.

The release behavior and in vitro osteogenesis of quercetin-loaded bioactive glass/hyaluronic acid/sodium alginate nanocomposite paste

Injectable pastes based on bioactive compounds and natural polymers are of interest in non-invasive bone surgeries. Several quantities of quercetin (100, 150, and 200 μM) were added to a sol-gel derived mesoporous bioactive glass. Injectable pastes based on quercetin-loaded bioactive glass, sodium alginate, and hyaluronic acid were prepared. Aggregated nanoparticles of bioactive glass and quercetin-loaded bioactive glass with mesoporous morphologies were confirmed by TEM and BET techniques. The quercetin release study was assessed in phosphate-buffered solution medium over 200 h and the obtained data were fitted by different eqs. A sustained release of quercetin was found, in which a better regression coefficient was achieved using Weibull equation. Human-derived mesenchymal stem cells were utilized to determine alkaline phosphatase activity and bone-related protein expression by western blotting and real-time PCR evaluations. Quercetin-loaded pastes increased the levels of alkaline phosphatase activity and the expression of Collagen-1, Osteopontin, Osteocalcin, and Runx2 proteins in a concentration-dependent manner. Due to the mesoporous architecture and high specific surface area of bioactive glass, the paste made of these particles and sodium alginate/hyaluronic acid macromolecules is appropriate matrix for quercetin release, resulting in promoted osteogenesis. The further in vivo studies can support the osteogenesis capacity of the quercetin-loaded paste.

Application of Antioxidant Compounds in Bone Defect Repair

Bone defects caused by trauma, tumor resection, and infections are significant clinical challenges. Excessive reactive oxygen species (ROS) usually accumulate in the defect area, which may impair the function of cells involved in bone formation, posing a serious challenge for bone repair. Due to the potent ROS scavenging ability, as well as potential anti-inflammatory and immunomodulatory activities, antioxidants play an indispensable role in the maintenance and protection of bone health and have gained increasing attention in recent years. This narrative review aims to give an overview of the main research directions on the application of antioxidant compounds in bone defect repair over the past decade. In addition, the positive effects of various antioxidants and their biomaterial delivery systems in bone repair are summarized to provide new insights for exploring antioxidant-based strategies for bone defect repair.

Mussel-inspired antimicrobial hydrogel with cellulose nanocrystals/tannic acid modified silver nanoparticles for enhanced calvarial bone regeneration

Bacterial infection is a serious challenge in the treatment of open bone defects, and reliance on antibiotic therapy may contribute to the emergence of drug-resistant bacteria. To solve this problem, this study developed a mineralized hydrogel (PVA-Ag-PHA) with excellent antibacterial properties and osteogenic capabilities. Silver nanoparticles (CNC/TA@AgNPs) were greenly synthesized using natural macromolecular cellulose nanocrystals (CNC) and plant polyphenolic tannins (TA) as stabilizers and reducing agents respectively, and then introduced into polyvinyl alcohol (PVA) and polydopamine-modified hydroxyapatite (PDA@HAP) hydrogel. The experimental results indicate that the PVA-Ag-PHA hydrogel, benefiting from the excellent antibacterial properties of CNC/TA@AgNPs, can not only eliminate Staphylococcus aureus and Escherichia coli, but also maintain a sustained sterile environment. At the same time, the HAP modified by PDA is uniformly dispersed within the hydrogel, thus releasing and maintaining stable concentrations of Ca2+ and PO43- ions in the local environment. The porous structure of the hydrogel with excellent biocompatibility creates a suitable bioactive environment that facilitates cell adhesion and bone regeneration. The experimental results in the rat critical-sized calvarial defect model indicate that the PVA-Ag-PHA hydrogel can effectively accelerate the bone healing process. Thus, this mussel-inspired hydrogel with antibacterial properties provides a feasible solution for the repair of open bone defects, demonstrating the considerable potential for diverse applications in bone repair.

Efficient three-dimensional (3D) human bone differentiation on quercetin-functionalized isotropic nano-architecture chitinous patterns of cockroach wings

Developing cost-effective, biocompatible scaffolds with nano-structured surface that truthfully replicate the physico-(bio)chemical and structural properties of bone tissue's extracellular matrix (ECM) is still challenging. In this regard, surface functionalization of natural scaffolds to enhance capability of mimicking 3D niches of the bone tissue has been suggested as a solution. In the current study, we aimed to investigate the potential of chitin-based cockroach wings (CW) as a natural scaffold for bone tissue engineering. To raise the osteogenic differentiation capacity of such a scaffold, a quercetin coating was also applied (hereafter this scaffold is referred as QCW). Moreover, the QCW scaffold exhibited effective antibacterial properties against gram-positive S. aureus bacteria. With respect to bone regeneration, the QCW scaffold optimally induced the differentiation of adipose-derived human mesenchymal stem cells (AD-hMSCs) into osteoblasts, as validated by mineralization assays, alkaline phosphatase (ALP) activity measurements, expression of pre-osteocyte marker genes, and immunocytochemical staining. Confirmation of the potent biocompatibility and physicochemical characteristics of the QCW scaffold through a series of in vitro and in vivo analysis revealed that surface modification had significant effect on multi-purpose features of obtained scaffold. Altogether, surface modification of QCW made it as an affordable bioinspired scaffold for bone tissue engineering.

A multifunctional quercetin/polycaprolactone electrospun fibrous membrane for periodontal bone regeneration

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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.

Flavonoid-Loaded Biomaterials in Bone Defect Repair

Skeletons play an important role in the human body, and can form gaps of varying sizes once damaged. Bone defect healing involves a series of complex physiological processes and requires ideal bone defect implants to accelerate bone defect healing. Traditional grafts are often accompanied by issues such as insufficient donors and disease transmission, while some bone defect implants are made of natural and synthetic polymers, which have characteristics such as good porosity, mechanical properties, high drug loading efficiency, biocompatibility and biodegradability. However, their antibacterial, antioxidant, anti-inflammatory and bone repair promoting abilities are limited. Flavonoids are natural compounds with various biological activities, such as antitumor, anti-inflammatory and analgesic. Their good anti-inflammatory, antibacterial and antioxidant activities make them beneficial for the treatment of bone defects. Several researchers have designed different types of flavonoid-loaded polymer implants for bone defects. These implants have good biocompatibility, and they can effectively promote the expression of angiogenesis factors such as VEGF and CD31, promote angiogenesis, regulate signaling pathways such as Wnt, p38, AKT, Erk and increase the levels of osteogenesis-related factors such as Runx-2, OCN, OPN significantly to accelerate the process of bone defect healing. This article reviews the effectiveness and mechanism of biomaterials loaded with flavonoids in the treatment of bone defects. Flavonoid-loaded biomaterials can effectively promote bone defect repair, but we still need to improve the overall performance of flavonoid-loaded bone repair biomaterials to improve the bioavailability of flavonoids and provide more possibilities for bone defect repair.

Resorbable Membranes for Guided Bone Regeneration: Critical Features, Potentials, and Limitations

Lack of horizontal and vertical bone at the site of an implant can lead to significant clinical problems that need to be addressed before implant treatment can take place. Guided bone regeneration (GBR) is a commonly used surgical procedure that employs a barrier membrane to encourage the growth of new bone tissue in areas where bone has been lost due to injury or disease. It is a promising approach to achieve desired repair in bone tissue and is widely accepted and used in approximately 40% of patients with bone defects. In this Review, we provide a comprehensive examination of recent advances in resorbable membranes for GBR including natural materials such as chitosan, collagen, silk fibroin, along with synthetic materials such as polyglycolic acid (PGA), polycaprolactone (PCL), polyethylene glycol (PEG), and their copolymers. In addition, the properties of these materials including foreign body reaction, mechanical stability, antibacterial property, and growth factor delivery performance will be compared and discussed. Finally, future directions for resorbable membrane development and potential clinical applications will be highlighted.

Quercetin-solid lipid nanoparticle-embedded hyaluronic acid functionalized hydrogel for immunomodulation to promote bone reconstruction

Bone defects are a persistent challenge in clinical practice. Although repair therapies based on tissue-engineered materials, which are known to have a crucial role in defective bone regeneration, have gathered increased attention, the current treatments for massive bone defects have several limitations. In the present study, based on the immunomodulatory inflammatory microenvironment properties of quercetin, we encapsulated quercetin-solid lipid nanoparticles (SLNs) in a hydrogel. Temperature-responsive poly(ε-caprolactone-co-lactide)-b-poly(ethylene glycol)-b-poly(ε-caprolactone-co-lactide) modifications were coupled to the main chain of hyaluronic acid hydrogel, constructing a novel, injectable bone immunomodulatory hydrogel scaffold. Extensive in vitro and in vivo data showed that this bone immunomodulatory scaffold forms an anti-inflammatory microenvironment by decreasing M1 polarization, while elevating the M2 polarization. Synergistic effects on angiogenesis and anti-osteoclastic differentiation were observed. These findings further proved that administering quercetin SLNs encapsulated in a hydrogel can aid bone defect reconstruction in rats, providing new insights for large-scale bone defect repair.

Polymeric and Composite Carriers of Protein and Non-Protein Biomolecules for Application in Bone Tissue Engineering

Conventional intake of drugs and active substances is most often based on oral intake of an appropriate dose to achieve the desired effect in the affected area or source of pain. In this case, controlling their distribution in the body is difficult, as the substance also reaches other tissues. This phenomenon results in the occurrence of side effects and the need to increase the concentration of the therapeutic substance to ensure it has the desired effect. The scientific field of tissue engineering proposes a solution to this problem, which creates the possibility of designing intelligent systems for delivering active substances precisely to the site of disease conversion. The following review discusses significant current research strategies as well as examples of polymeric and composite carriers for protein and non-protein biomolecules designed for bone tissue regeneration.

Accelerating bone regeneration using poly(lactic-co-glycolic acid)/hydroxyapatite scaffolds containing duck feet-derived collagen

Collagen, with low antigenicity and excellent cell adhesion, is a biomaterial mainly used for regenerating bone, cartilage, and skin, owing to its biocompatibility and biodegradability. Results from a previous study confirmed that a scaffold mixed with duck feet-derived collagen (DC) and Poly(lactic-co-glycolic acid) (PLGA) reduced inflammatory reaction and increased bone regeneration. To develop an optimal bone substitute we included hydroxyapatite (HAp), a key osteoconductive material, in a DC and PLGA mixture. We fabricated 0, 10, 20, 40, 60, and 80 wt% DC/PLGA/HAp scaffolds and studied their potential for bone tissue engineering. Characteristic analysis of the scaffold and seeding of rabbit bone marrow mesenchymal stem cells (rBMSCs) on the scaffold were conducted to investigate cell proliferation, osteogenic differentiation, and bone formation. We confirmed that increasing DC concentration not only improved the compressive strength of the DC/PLGA/HAp scaffold but also cell proliferation and osteogenic differentiation. It was found through comparison with previous studies that including HAp in the scaffold also promotes osteogenic differentiation. Our study thus shows through in vivo results that the 80 wt% DC/PLGA/HAp scaffold promotes bone mineralization and collagen deposition while reducing the inflammatory response. Hence, 80 wt% DC/PLGA/HAp has excellent potential as a biomaterial for bone regeneration applications.

Development and evaluation of local regenerative biomimetic bone-extracellular matrix scaffold loaded with nano-formulated quercetin for orthopedic fractures

The prevalence of bone injuries is greatly increasing each year and the proper healing of fractures without any complications is very challenging. Self-setting calcium phosphate cements (CPCs) have attracted great attention as bioactive synthetic bone substitutes. Quercetin (QT) is a multipurposed drug with reported bone-conserving properties. The loading of QT and QT-phospholipid complex within nanostructured lipid carriers (NLC) was proposed to overcome the poor physical properties of the drug and to introduce the use of bioactive excipients as phospholipids and olive oil. The aim of this work was to formulate a regenerative scaffold loaded with nano-formulated QT for local treatment of orthopedic fractures. For the first time, scaffolds composed of brushite CPC were prepared and loaded with quercetin lipid nano-systems. In vitro tests proved that the addition of lipid nano-systems did not deteriorate the properties of CPC where QT-NLC/CPC showed an adequate setting time, appropriate compressive strength, and porosity. The scanning electron microscope confirmed maintenance of nanoparticles integrity within the cement. Using a rat femur bone defect animal model, the histological results showed that the QT-NLC/CPC had a superior bone healing potential compared to crude unformulated QT/CPC. In conclusion, QT-NLC /CPC are promising lipid nano-composite materials that could enhance bone regeneration.

Research progress of natural silk fibroin and the appplication for drug delivery in chemotherapies

Silk fibroin has been widely used in biological fields due to its biocompatibility, mechanical properties, biodegradability, and safety. Recently, silk fibroin as a drug carrier was developed rapidly and achieved remarkable progress in cancer treatment. The silk fibroin-based delivery system could effectively kill tumor cells without significant side effects and drug resistance. However, few studies have been reported on silk fibroin delivery systems for antitumor therapy. The advancement of silk fibroin-based drug delivery systems research and its applications in cancer therapy are highlighted in this study. The properties, applications, private opinions, and future prospects of silk fibroin carriers are discussed to understand better the development of anti-cancer drug delivery systems, which may also contribute to advancing silk fibroin innovation.

Advances in cell membrane-coated nanoparticles and their applications for bone therapy

Due to the specific structure of natural bone, most of the therapeutics are incapable to be delivered into the targeted site with effective concentrations. Nanotechnology has provided a good way to improve this issue, cell membrane mimetic nanoparticles (NPs) have been emerging as an ideal nanomaterial which integrates the advantages of natural cell membranes with synthetic NPs to significantly improve the biocompatibility as well as achieving long-lasting circulation and targeted delivery. In addition, functionalized modifications of the cell membrane facilitate more precise targeting and therapy. Here, an overview of the preparation of cell membrane-coated NPs and the properties of cell membranes from different cell sources has been given to expatiate their function and potential applications. Strategies for functionalized modification of cell membranes are also briefly described. The application of cell membrane-coated NPs for bone therapy is then presented according to the function of cell membranes. Moreover, the prospects and challenges of cell membrane-coated NPs for translational medicine have also been discussed.

A hydrogel-fiber-hydrogel composite scaffold based on silk fibroin with the dual-delivery of oxygen and quercetin

Supplying sufficient oxygen within the scaffolds is one of the essential hindrances in tissue engineering that can be resolved by oxygen-generating biomaterials (OGBs). Two main issues related to OGBs are controlling oxygenation and reactive oxygen species (ROS). To address these concerns, we developed a composite scaffold entailing three layers (hydrogel-electrospun fibers-hydrogel) with antioxidant and antibacterial properties. The fibers, the middle layer, reinforced the composite structure, enhancing the mechanical strength from 4.27 ± 0.15 to 8.27 ± 0.25 kPa; also, this layer is made of calcium peroxide and silk fibroin (SF) through electrospinning, which enables oxygen delivery. The first and third layers are physical SF hydrogels to control oxygen release, containing quercetin (Q), a nonenzymatic antioxidant. This composite scaffold resulted in almost more than 40 mmHg of oxygen release for at least 13 days, and compared with similar studies is in a high range. Here, Q was used for the first time for an OGB to scavenge the possible ROS. Q delivery not only led to antioxidant activity but also stabilized oxygen release and enhanced cell viability. Based on the given results, this composite scaffold can be introduced as a safe and controllable oxygen supplier, which is promising for tissue engineering applications, particularly for bone.

Surface modification of titanium substrate via combining photothermal therapy and quorum-sensing-inhibition strategy for improving osseointegration and treating biofilm-associated bacterial infection

Insufficient osseointegration and biofilm-associated bacterial infection are important challenges for clinical application of titanium (Ti)-based implants. Here, we constructed mesoporous polydopamine (MPDA) nanoparticles (NPs) loaded with luteolin (LUT, a quorum sensing inhibitor), which were further coated with the shell of calcium phosphate (CaP) to construct MPDA-LUT@CaP nanosystem. Then, MPDA-LUT@CaP NPs were immobilized on the surface of Ti implants. Under acidic environment of bacterial biofilm-infection, the CaP shell of MPDA-LUT@CaP NPs was rapidly degraded and released LUT, Ca2+ and PO4 3- from the surface of Ti implant. LUT could effectively inhibit and disperse biofilm. Furthermore, under near-infrared irradiation (NIR), the thermotherapy induced by the photothermal conversion effect of MPDA destroyed the integrity of the bacterial membrane, and synergistically led to protein leakage and a decrease in ATP levels. Combined with photothermal therapy (PTT) and quorum-sensing-inhibition strategy, the surface-functionalized Ti substrate had an antibacterial rate of over 95.59% against Staphylococcus aureus and the elimination rate of the formed biofilm was as high as 90.3%, so as to achieve low temperature and efficient treatment of bacterial biofilm infection. More importantly, the modified Ti implant accelerated the growth of cell and the healing process of bone tissue due to the released Ca2+ and PO4 3-. In summary, this work combined PTT with quorum-sensing-inhibition strategy provides a new idea for surface functionalization of implant for achieving effective antibacterial and osseointegration capabilities.

Synthesis and characterization of a calcium phosphate bone cement with quercetin-containing PEEK/PLGA microparticles

This study aimed to describe the synthesis and characterization of a calcium phosphate cement (CPC) with polyetheretherketone/poly (lactic-co-glycolic) acid (PEEK/PLGA) micro-particles containing quercetin. CPC powder was synthesized by mixing dicalcium phosphate anhydrate and tetracalcium phosphate. To synthesize PEEK/PLGA microparticles, PLGA85:15 was mixed with 90 wt% PEEK. The weight ratio of quercetin/PLGA/PEEK was 1:9:90 wt%. PEEK/PLGA/quercetin microparticles with 3, 5, and 6 wt% was added to CPC. The setting time, compressive strength, drug release profile, solubility, pH, and porosity of synthesized cement were evaluated. The morphology and physicochemical properties of particles was analyzed by scanning electron microscopy, Fourier-transform infrared spectroscopy (FTIR), x-ray diffraction (XRD), and inductively coupled plasma. Cytotoxicity was assessed by the methyl thiazolyl tetrazolium assay using dental pulp stem cells. Expression of osteoblastic differentiation genes was evaluated by real-time polymerase chain reaction. Data were analyzed by one-way ANOVA and Tukey's test (alpha = 0.05). The setting time of 3 wt% CPC was significantly longer than 5 and 6 wt% CPC (P< 0.001). The 6 wt% CPC had significantly higher compressive strength than other groups (P= 0.001). The release of quercetin from CPCs increased for 5 d, and then reached a plateau. XRD and FTIR confirmed the presence of hydroxyapatite in cement composition. Significantly higher expression of osteocalcin (OCN) and osteopontin (OPN) was noted in 3 wt% and 6 wt% CPCs. Addition of quercetin-containing PEEK/PLGA microparticles to CPC enhanced its compressive strength, decreased its setting time, enabled controlled drug release, and up-regulated OPN and OCN.

Femtosecond laser optimization of PEEK: efficient bioactivity achieved by synergistic surface chemistry and structures

Poly-ether-ether-ketone (PEEK) is considered a potential orthopedic material due to the excellent mechanical properties and chemical resistance, but its biological inertness hampers its further clinical application. In this study, advanced femtosecond laser microfabrication technology was utilized to induce the change of the surface characteristics of PEEK to improve its bioactivity. Meanwhile, the mechanism of surface reaction and improved bioactivity was interpreted in detail from the perspective of material science. The surface physical-chemical characterization results showed that femtosecond laser etching could increase the surface energy, and the contents of active sites including amorphous carbon and carbon-hydroxyl on PEEK surfaces. In vitro validation experiments demonstrated that the samples etched with a femtosecond laser had a better ability to induce apatite deposition and cell proliferation than those treated with popular sulfonation modification, which would lead to better bioactivity and osteointegration. The current work fully presents the mechanism of the femtosecond laser low-temperature plasma effect on PEEK and the resulting surface characteristics, which could broaden the application of PEEK in the orthopedic field. Moreover, it has great potential in the surface design and modification of other biomaterials with enhanced bioactivity.

Mineralized Enzyme-Based Biomaterials with Superior Bioactivities for Bone Regeneration

The formation and metabolic balance of bone tissue is a controllable process of biomineralization, which is regulated by various cells, biomolecules, and ions. Enzyme molecules play an important role in this process, and alkaline phosphatase (ALP) is one of the most critical factors. In this study, inspired by the process of bone biomineralization, a biomimetic strategy is achieved for the preparation of mineralized ALP nanoparticles (MALPNs), by taking advantages of the unique reaction between ALP and calcium ions in Dulbecco's modified Eagle's medium. Benefiting from the mild biomineralization reaction, the MALPN system highly maintains the activity of ALP. Furthermore, the in vitro studies show that the MALPN system significantly enhances the proliferation of bone marrow mesenchymal stem cells and upregulates their osteogenic differentiation. When evaluated as synthetic graft materials for bone regeneration, the MALPN-incorporated gelatin methacryloyl graft shows excellent mechanical properties, a sustained release profile of ALP, and high biocompatibility and efficacy in guiding bone regeneration and vascularization for critical-sized rat calvarial defect. Moreover, we also demonstrate that the biomimetic mineralization strategy can be adopted for other proteins such as acid phosphatase, bovine serum albumin, fibrinogen, and gelatin, suggesting its universality for constructing mineralized protein-/enzyme-based bioactive materials for the application of tissue regeneration.

The Role of Flavonoids in the Osteogenic Differentiation of Mesenchymal Stem Cells

Mesenchymal stem cells (MSCs) play an important role in developing bone tissue engineered constructs due to their osteogenic and chondrogenic differentiation potential. MSC-based tissue engineered constructs are generally considered a safe procedure, however, the long-term results obtained up to now are far from satisfactory. The main causes of these therapeutic limitations are inefficient homing, engraftment, and directional differentiation. Flavonoids are a secondary metabolite, widely existed in nature and have many biological activities. For a long time, researchers have confirmed the anti-osteoporosis effect of flavonoids through in vitro cell experiments, animal studies. In recent years the regulatory effects of flavonoids on mesenchymal stem cells (MSCs) differentiation have been received increasingly attention. Recent studies revealed flavonoids possess the ability to modulate self-renewal and differentiation potential of MSCs. In order to facilitate further research on MSCs osteogenic differentiation of flavonoids, we surveyed the literature published on the use of flavonoids in osteogenic differentiation of MSCs, and summarized their pharmacological activities as well as the underlying mechanisms, aimed to explore their promising therapeutic application in bone disorders and bone tissue engineered constructs.

Traditional Chinese Medicine Compound-Loaded Materials in Bone Regeneration

Bone is a dynamic organ that has the ability to repair minor injuries via regeneration. However, large bone defects with limited regeneration are debilitating conditions in patients and cause a substantial clinical burden. Bone tissue engineering (BTE) is an alternative method that mainly involves three factors: scaffolds, biologically active factors, and cells with osteogenic potential. However, active factors such as bone morphogenetic protein-2 (BMP-2) are costly and show an unstable release. Previous studies have shown that compounds of traditional Chinese medicines (TCMs) can effectively promote regeneration of bone defects when administered locally and systemically. However, due to the low bioavailability of these compounds, many recent studies have combined TCM compounds with materials to enhance drug bioavailability and bone regeneration. Hence, the article comprehensively reviewed the local application of TCM compounds to the materials in the bone regeneration in vitro and in vivo. The compounds included icariin, naringin, quercetin, curcumin, berberine, resveratrol, ginsenosides, and salvianolic acids. These findings will contribute to the potential use of TCM compound-loaded materials in BTE.

Re-appraising the role of flavonols, flavones and flavonones on osteoblasts and osteoclasts- A review on its molecular mode of action

Bone disorders have become a global concern illustrated with decreased bone mineral density and disruption in microarchitecture of natural bone tissue organization. Natural compounds that promote bone health by augmenting osteoblast functions and suppressing osteoclast functions has gained much attention and offer greater therapeutic value compared to conventional therapies. Amongst several plant-based molecules, flavonoids act as a major combatant in promoting bone health through their multi-faceted biological activities such as antioxidant, anti-inflammatory, and osteogenic properties. They protect bone loss by regulating the signalling cascades involved in osteoblast and osteoclast functions. Flavonoids augment osteoblastogenesis and inhibits osteoclastogenesis through their modulation of various signalling pathways. This review discusses the role of various flavonoids and their molecular mechanisms involved in maintaining bone health by regulating osteoblast and osteoclast functions.

Sustained release of naringin from silk-fibroin-nanohydroxyapatite scaffold for the enhancement of bone regeneration

Bone defects are a common challenge in the clinical setting. Bone tissue engineering (BTE) is an effective treatment for the clinical problem of large bone defects. In this study, we fabricated silk fibroin (SF)/hydroxyapatite (HAp) scaffolds inlaid with naringin poly lactic-co-glycolic acid (PLGA) microspheres, investigating the feasibility of their application in BTE. Naringin PLGA microspheres were manufactured and adhered to the SF/HAp scaffold. Bone mesenchymal stem cells (BMSCs) were inoculated onto the SF/HAp scaffold containing naringin PLGA microsphere to examine the biocompatibility of the SF/HAp scaffolds. A rabbit femoral distal bone defect model was used to evaluate the in vivo function of the SF/HAp scaffolds containing naringin-loaded PLGA microspheres. The current study demonstrated that SF/HAp scaffolds containing naringin-loaded PLGA microspheres show promise as osteo-modulatory biomaterials for bone regeneration.

Concomitant Effect of Quercetin- and Magnesium-Doped Calcium Silicate on the Osteogenic and Antibacterial Activity of Scaffolds for Bone Regeneration

Quercetin is a bioflavonoid which has a broad spectrum of biological activity. Due to its lower chemical stability, it is usually encapsulated, or a metal–quercetin complex is formed to enhance its biological activity at a lower concentration. Here, our novel approach was to form a quercetin complex to magnesium-doped calcium silicate (CMS) ceramics through a coprecipitation technique so as to take advantage of quercetin’s antibacterial activity within the antibacterial and osteogenic potential of the silicate. Due to quercetin’s inherent metal-chelating ability, (Ca+Mg)/Si increased with quercetin concentration. Quercetin in magnesium-doped calcium silicate ceramic showed concentration-dependent pro-oxidant and antioxidant activity in SaOS-2 with respect to quercetin concentration. By optimizing the relative concentration, we were able to achieve 3-fold higher proliferation and 1.6-fold higher total collagen at day 14, and a 1.7-fold higher alkaline phosphatase production at day 7 with respect to polycaprolactone/polyvinylpyrrolidone (PCL/PVP) scaffold. Quercetin is effective against Gram-positive bacteria such as S. aureus. Quercetin is coupled with CMS provided similar effect with lower quercetin concentration than quercetin alone. Quercetin reduced bacterial adhesion, proliferation and biofilm formation. Therefore, quercetin-coupled magnesium-doped calcium silicate not only enhanced osteogenic potential, but also reduced bacterial adhesion and proliferation.

Coating Polyelectrolyte Multilayers Loaded with Quercetin on Titanium Surfaces by Layer-By-Layer Assembly Technique to Improve Surface Osteogenesis Under Osteoporotic Condition

Titanium (Ti) and its alloy implants are widely used in the field of orthopedics, and osteoporosis is an important reason for implantation failure. This study aimed to establish a quercetin (QTN) controlled release system on the surface of titanium implants and to study its effects on osteogenesis and osseointegration on the surface of implants. Polyethylenimine (PEI) was first immobilized on a titanium substrate as the base layer, and then, hyaluronic acid/chitosan-quercetin (HA/CS-QTN) multilayer films were assembled on the PEI layer by a self-assembly technique. Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM) and contact angle measurements were used to characterize and analyze the samples. The release characteristics of QTN were studied by release assays. The osteogenic ability of the samples was evaluated by experiments on an osteoporosis rat model and MC3T3-E1 cells. The FTIR, SEM, and contact angle measurements all showed that the PEI substrate layer and HA/CS-QTN multilayer film were successfully immobilized on the titanium matrix. The drug release test showed the successful establishment of a QTN controlled release system. The in vitro results showed that osteoblasts exhibited higher adhesion, proliferation and differentiation ability on the coated titanium matrix than on the pure titanium surface. In addition, the in vivo results showed that the HA/CS-QTN coating significantly increased the new bone mass around the implant. By depositing a PEI matrix layer and HA/CS-QTN multilayer films on titanium implants, a controlled release system of QTN was established, which improved implant surface osseointegration under osteoporotic conditions. This study proposes a new implant therapy strategy for patients with osteoporosis.

Electrospun chitosan oligosaccharide/polycaprolactone nanofibers loaded with wound-healing compounds of Rutin and Quercetin as antibacterial dressings

Burn injury has posed devastating burdens on the public health due to its inevitable damage to the skin structure resulting in the increased risk of infection. Therefore, it is highly demanding to develop efficacious antibacterial wound-healing dressing. Despite the favourable wound-healing activities, the curative efficacy of phytochemical compounds of quercetin (Qe) and its derivatives is limited by their poor water solubility. Here, we have fabricated a novel electrospun nanofiber membrane (ENM) consisting of polycaprolactone (PCL), chitosan oligosaccharides (COS), and Qe/Rutin (Ru) as the potential bioactive dressing for wound healing. The incorporation of chitosan oligosaccharides (COSs) in the PCL scaffold at the optimized molar ratio not only contributed to the improved hydrophilicity and water absorption performance of the ENM but effectively increased the specific surface area of the formed nanofibers. In particular, the antioxidant and antibacterial activities of the Qe/rutin-loaded nanofiber membranes were tested, which revealed that the PCL-COS-Qe membrane exhibited superior performance among all nanofiber membranes. Therefore, the developed PCL-COS-Qe/Ru nanofiber membranes hold enormous potential as healthcare products, such as wound dressings for burn injuries.

The synergistic effects of quercetin-containing 3D-printed mesoporous calcium silicate/calcium sulfate/poly-ε-caprolactone scaffolds for the promotion of osteogenesis in mesenchymal stem cells

BACKGROUND/PURPOSE

Several growth factors were proven to be effective in the treatment of bone defects and fractures and thus have great potential for bone regeneration applications. However, it needs low-temperature storage and transportation. This study aimed to investigate the herbal extract quercetin, a candidate for natural flavonoid compounds that have been reported to be involved in regulating inflammation and improving immunity and health.

METHODS

In this study, we prepared quercetin (Q)/mesoporous calcium silicate calcium sulfate (MSCS)/polycaprolactone (PCL) composite scaffolds using the 3D printing technique, where we immersed it in simulated body fluid (SBF) solution and soaked it for up to 60 days. The characteristics of quercetin scaffold were examined by scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), immunofluorescence, and Alizarin Red S staining.

RESULTS

We found precipitation of apatite on the surface of the scaffold. The in vitro results for cell proliferation, cytotoxicity, and immunofluorescence staining revealed that Wharton's jelly mesenchymal stem cells (WJMSCs) with a 2% quercetin (Q2) scaffold were significantly higher in number than with 1% quercetin (Q1) and MSCS scaffolds. The phalloidin staining of cell skeletons on the surface of Q2 revealed powerful cell-to-cell adhesion and high expression of green fluorescence. The Q2 scaffold also had the highest calcium deposit levels based on Alizarin Red S staining in all scaffolds. This indicated that quercetin was able to induce cell growth and mitosis, echoing the previous preliminary results.

CONCLUSION

Our initial results indicate that this natural herbal extract can be a good bone-based gene substitution for bone regeneration.

Bioactive Zinc(II) complex incorporated PCL/gelatin electrospun nanofiber enhanced bone tissue regeneration

Bone tissue regeneration is augmented by biocompatible nanofiber scaffolds, that supports reliable and enhanced bone formation. Zinc is an essential mineral that is vital for routine skeletal growth and it emerges to be able to improve bone regeneration. Phytochemicals, particularly flavonoids have achieved prominent interest for their therapeutic ability, they have demonstrated promising effects on bone by encouraging osteoblastogenesis, which finally leads to bone formation. In this study, we have synthesized bioactive zinc(II) quercetin complex material and used for nanofibers scaffold fabrication to enhance bone tissue regeneration property. Two derivatives of zinc(II) quercetin complexes [(Zn(quercetin) (H₂O)₂) (Zn+Q), and Zn(quercetin)(phenanthroline) (Zn+Q(PHt)) have been synthesized and characterized using UV-Visible spectrophotometer and Fourier Transform-IR spectroscopy. The UV-Visible absorption and IR spectra prove the B-ring chelation of the flavonoid quercetin to zinc(II) rather C-ring chelation. The potential ability of the above synthesized metal complexes on osteogenesis and angiogenesis have been studied. Besides the bioactivity of the metal complexes, the control quercetin has also been examined. The chick embryo chorioallantoic membrane (CAM) assay demonstrated that the angiogenic parameters were increased by the (Zn+Q(PHt)) complex. Amongst, (Zn+Q(PHt)) complex showed significant activity and thereby this complex has been further examined for the bone tissue activity by incorporating the complex into a nanofiber through electrospinning method. At the molecular level, Runx2, mRNA and protein, ALP and type 1 collagen mRNAs, and osteoblast-specific microRNA, pre-mir-15b were examined using real time RT-PCR and Western blot assay. Histology studies showed that the (PCL/gelatin/Zn+Q(PHt)) was biocompatibility in-ovo. Overall, the present study showed that quercetin-zinc complex (Zn+Q(PHt)) incorporated into PCL/gelatin nanofiber can act as a pharmacological agent for treating bone associated defects and promote bone regeneration.

Polyphenols as a versatile component in tissue engineering

The fabrication of functional tissue or organs substitutes has always been the pursuit of goals in the field of tissue engineering. But even biocompatible tissue-engineered scaffolds still suffer from immune rejection, subsequent long-term oxidative stress and inflammation, which can delay normal tissue repair and regeneration. As a well-known natural antioxidant, polyphenols have been widely used in tissue engineering in recent years. The introduced polyphenols not only reduce the damage of oxidative stress to normal tissues, but show specific affinity to functional molecules, such as receptors, enzyme, transcription and transduction factors, etc. Therefore, polyphenols can promote the recovery process of damaged tissues by both regulating tissue microenvironment and participating in cell events, which embody specifically in antioxidant, anti-inflammatory, antibacterial and growth-promoting properties. In addition, based on its hydrophilic and hydrophobic moieties, polyphenols have been widely used to improve the mechanical properties and anti-degradation properties of tissue engineering scaffolds. In this review, the research advances of tissue engineering scaffolds containing polyphenols is discussed systematically from the aspects of action mechanism, introduction method and regulation effect of polyphenols, in order to provide references for the rational design of polyphenol-related functional scaffolds.

Bioactive Herbal Extracts of Traditional Chinese Medicine Applied with the Biomaterials: For the Current Applications and Advances in the Musculoskeletal System

Traditional Chinese medicine (TCM) has demonstrated superior therapeutic effect for musculoskeletal diseases for thousands of years. Recently, the herbal extracts of TCM have received rapid advances in musculoskeletal tissue engineering (MTE). A literature review collecting both English and Chinese references on bioactive herbal extracts of TCM in biomaterial-based approaches was performed. This review provides an up-to-date overview of application of TCMs in the field of MTE, involving regulation of multiple signaling pathways in osteogenesis, angiogenesis, anti-inflammation, and chondrogenesis. Meanwhile, we highlight the potential advantages of TCM, opening the possibility of its extensive application in MTE. Overall, the superiority of traditional Chinese medicine turns it into an attractive candidate for coupling with advanced additive manufacturing technology.

Biomimetic and osteogenic 3D silk fibroin composite scaffolds with nano MgO and mineralized hydroxyapatite for bone regeneration

Artificial bioactive materials have received increasing attention worldwide in clinical orthopedics to repair bone defects that are caused by trauma, infections or tumors, especially dedicated to the multifunctional composite effect of materials. In this study, a weakly alkaline, biomimetic and osteogenic, three-dimensional composite scaffold (3DS) with hydroxyapatite (HAp) and nano magnesium oxide (MgO) embedded in fiber (F) of silkworm cocoon and silk fibroin (SF) is evaluated comprehensively for its bone repair potential in vivo and in vitro experiments, particularly focusing on the combined effect between HAp and MgO. Magnesium ions (Mg²⁺) has long been proven to promote bone tissue regeneration, and HAp is provided with osteoconductive properties. Interestingly, the weak alkaline microenvironment from MgO may also be crucial to promote Sprague-Dawley (SD) rat bone mesenchymal stem cells (BMSCs) proliferation, osteogenic differentiation and alkaline phosphatase (ALP) activities. This SF/F/HAp/nano MgO (SFFHM) 3DS with superior biocompatibility and biodegradability has better mechanical properties, BMSCs proliferation ability, osteogenic activity and differentiation potential compared with the scaffolds adding HAp or MgO alone or neither. Similarly, corresponding meaningful results are also demonstrated in a model of distal lateral femoral defect in SD rat. Therefore, we provide a promising 3D composite scaffold for promoting bone regeneration applications in bone tissue engineering.

Histomorphometric, Immunohistochemical, Ultrastructural Characterization of a Nano-Hydroxyapatite/Beta-Tricalcium Phosphate Composite and a Bone Xenograft in Sub-Critical Size Bone Defect in Rat Calvaria

Nowadays, we can observe a worldwide trend towards the development of synthetic biomaterials. Several studies have been conducted to better understand the cellular mechanisms involved in the processes of inflammation and bone healing related to living tissues. The aim of this study was to evaluate tissue behaviors of two different types of biomaterials: synthetic nano-hydroxyapatite/beta-tricalcium phosphate composite and bone xenograft in sub-critical bone defects in rat calvaria. Twenty-four rats underwent experimental surgery in which two 3 mm defects in each cavity were tested. Rats were divided into two groups: Group 1 used xenogen hydroxyapatite (Bio Oss™); Group 2 used synthetic nano-hydroxyapatite/beta-tricalcium phosphate (Blue Bone™). Sixty days after surgery, calvaria bone defects were filled with biomaterial, animals were euthanized, and tissues were stained with Masson’s trichrome and periodic acid–Schiff (PAS) techniques, immune-labeled with anti-TNF-α and anti-MMP-9, and electron microscopy analyses were also performed. Histomorphometric analysis indicated a greater presence of protein matrix in Group 2, in addition to higher levels of TNF-α and MMP-9. Ultrastructural analysis showed that biomaterial fibroblasts were associated with the tissue regeneration stage. Paired statistical data indicated that Blue Bone™ can improve bone formation/remodeling when compared to biomaterials of xenogenous origin.

Quercetin as an Agent for Protecting the Bone: A Review of the Current Evidence

Quercetin is a flavonoid abundantly found in fruits and vegetables. It possesses a wide spectrum of biological activities, thus suggesting a role in disease prevention and health promotion. The present review aimed to uncover the bone-sparing effects of quercetin and its mechanism of action. Animal studies have found that the action of quercetin on bone is largely protective, with a small number of studies reporting negative outcomes. Quercetin was shown to inhibit RANKL-mediated osteoclastogenesis, osteoblast apoptosis, oxidative stress and inflammatory response while promoting osteogenesis, angiogenesis, antioxidant expression, adipocyte apoptosis and osteoclast apoptosis. The possible underlying mechanisms involved are regulation of Wnt, NF-κB, Nrf2, SMAD-dependent, and intrinsic and extrinsic apoptotic pathways. On the other hand, quercetin was shown to exert complex and competing actions on the MAPK signalling pathway to orchestrate bone metabolism, resulting in both stimulatory and inhibitory effects on bone in parallel. The overall interaction is believed to result in a positive effect on bone. Considering the important contributions of quercetin in regulating bone homeostasis, it may be considered an economical and promising agent for improving bone health. The documented preclinical findings await further validation from human clinical trials.

Repositioning Natural Antioxidants for Therapeutic Applications in Tissue Engineering

Although a large panel of natural antioxidants demonstrate a protective effect in preventing cellular oxidative stress, their low bioavailability limits therapeutic activity at the targeted injury site. The importance to deliver drug or cells into oxidative microenvironments can be realized with the development of biocompatible redox-modulating materials. The incorporation of antioxidant compounds within implanted biomaterials should be able to retain the antioxidant activity, while also allowing graft survival and tissue recovery. This review summarizes the recent literature reporting the combined role of natural antioxidants with biomaterials. Our review highlights how such functionalization is a promising strategy in tissue engineering to improve the engraftment and promote tissue healing or regeneration.

Gaseous sulfur trioxide induced controllable sulfonation promoting biomineralization and osseointegration of polyetheretherketone implants

Fabricating a desired porous structure on the surface of biomedical polyetheretherketone (PEEK) implants for enhancing biological functions is crucial and difficult due to its inherent chemical inertness. In this study, a porous surface of PEEK implants was fabricated by controllable sulfonation using gaseous sulfur trioxide (SO₃) for different time (5, 15, 30, 60 and 90 min). Micro-topological structure was generated on the surface of sulfonated PEEK implants preserving original mechanical properties. The protein absorption capacity and apatite forming ability was thus improved by the morphological and elemental change with higher degree of sulfonation. In combination of the appropriate micromorphology and bioactive sulfonate components, the cell adhesion, migration, proliferation and extracellular matrix secretion were obviously enhanced by the SPEEK-15 samples which were sulfonated for 15 min. Finding from this study revealed that controllable sulfonation by gaseous SO₃ would be an extraordinarily strategy for improving osseointegration of PEEK implants by adjusting the microstructure and chemical composition while maintaining excellent mechanical properties.

Tanshinone IIA Delivery Silk Fibroin Scaffolds Significantly Enhance Articular Cartilage Defect Repairing via Promoting Cartilage Regeneration

Cartilage tissue engineering is a promising approach for repairing articular cartilage defects and requires proper scaffolds and necessary growth factors. Herein, tanshinone IIA (TAN) delivery silk fibroin scaffolds were prepared for efficient cartilage defect repair by bioactivities of TAN. By incubating with the TAN delivery silk fibroin scaffold, the transcription of the chondrocytic activity-related genes was enhanced in chondrocytes, and it also can inhibit cell apoptosis and reduce the oxidative stress by regulating the transcription of related genes, indicating that these scaffolds may promote cartilage regeneration. TAN10 delivery silk fibroin scaffolds, in which the concentration of TAN is 10 μg/mL, significantly promotes chondrocytes to generate the cartilage-specific extracellular matrix and tissue both in vitro and in vivo, compared with silk fibroin scaffolds. By treating rabbit articular cartilage defects with TAN10 delivery silk fibroin scaffolds, cartilage defects were filled with hyaline-cartilage-like tissue that integrated with the surrounding cartilage perfectly and displayed strong mechanical properties and higher extracellular matrix content. Hence, TAN facilitates cartilage regeneration, and TAN delivery silk fibroin scaffolds can be potentially applied in the clinics treating cartilage defects in the future.

Engineered three-dimensional scaffolds for enhanced bone regeneration in osteonecrosis

Osteonecrosis, which is typically induced by trauma, glucocorticoid abuse, or alcoholism, is one of the most severe diseases in clinical orthopedics. Osteonecrosis often leads to joint destruction, and arthroplasty is eventually required. Enhancement of bone regeneration is a critical management strategy employed in osteonecrosis therapy. Bone tissue engineering based on engineered three-dimensional (3D) scaffolds with appropriate architecture and osteoconductive activity, alone or functionalized with bioactive factors, have been developed to enhance bone regeneration in osteonecrosis. In this review, we elaborate on the ideal properties of 3D scaffolds for enhanced bone regeneration in osteonecrosis, including biocompatibility, degradability, porosity, and mechanical performance. In addition, we summarize the development of 3D scaffolds alone or functionalized with bioactive factors for accelerating bone regeneration in osteonecrosis and discuss their prospects for translation to clinical practice.

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Engineered three-dimensional scaffolds boost bone regeneration in osteonecrosis.

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The ideal properties of three-dimensional scaffolds for osteonecrosis treatment are discussed.

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Bioactive factors-functionalized three-dimensional scaffolds are promising bone regeneration devices for osteonecrosis management.

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The challenges and opportunities of engineered three-dimensional scaffolds for osteonecrosis therapy are predicted.

Tough Anisotropic Silk Nanofiber Hydrogels with Osteoinductive Capacity

Multiple physical cues such as hierarchical microstructures, topography, and stiffness influence cell fate during tissue regeneration. Yet, introducing multiple physical cues to the same biomaterial remains a challenge. Here, a synergistic cross-linking strategy was developed to fabricate protein hydrogels with multiple physical cues based on combinations of two types of silk nanofibers. β-sheet-rich silk nanofibers (BSNFs) were blended with amorphous silk nanofibers (ASNFs) to form composite nanofiber systems. The composites were transformed into tough hydrogels through horseradish peroxidase (HRP) cross-linking in an electric field, where ASNFs were cross-linked with HRP, while BSNFs were aligned by the electrical field. Anisotropic morphologies and higher stiffness of 120 kPa were achieved. These anisotropic hydrogels induced osteogenic differentiation and the aligned aggregation of stem cells in vitro while also exhibiting osteoinductive capacity in vivo. Improved tissue outcomes with the hydrogels suggest promising applications in bone tissue engineering, as the processing strategy described here provides options to form hydrogels with multiple physical cues.

Mesenchymal stem cell-loaded thermosensitive hydroxypropyl chitin hydrogel combined with a three-dimensional-printed poly(ε-caprolactone) /nano-hydroxyapatite scaffold to repair bone defects via osteogenesis, angiogenesis and immunomodulation

Chitin-derived hydrogels are commonly used in bone regeneration because of their high cell compatibility; however, their poor mechanical properties and little knowledge of the interaction between the materials and host cells have limited their practical application. Methods: To evaluate osteoinductivity and enhance the mechanical properties of a newly synthesized thermosensitive hydroxypropyl chitin hydrogel (HPCH), a mesenchymal stem cell (MSC)-encapsulated HPCH was infused into a three-dimensional-printed poly (ε-caprolactone) (PCL)/ nano-hydroxyapatite (nHA) scaffold to form a hybrid scaffold. The mechanical properties and cell compatibility of the scaffold were tested. The interaction between macrophages and scaffold for angiogenesis and osteogenesis were explored in vitro and in vivo. Results: The hybrid scaffold showed improved mechanical properties and high cell viability. When MSCs were encapsulated in HPCH, osteo-differentiation was promoted properly via endochondral ossification. The co-culture experiments showed that the hybrid scaffold facilitated growth factor secretion from macrophages, thus promoting vascularization and osteoinduction. The Transwell culture proved that MSCs modulated the inflammatory response of HPCH. Additionally, subcutaneous implantation of MSC-encapsulated HPCH confirmed M2 activation. In situ evaluation of calvarial defects confirmed that the repair was optimal in the MSC-loaded HPCH + PCL/nHA group. Conclusions: PCL/nHA + HPCH hybrid scaffolds effectively promoted vascularization and osteoinduction via osteogenesis promotion and immunomodulation, which suggests promising applications for bone regeneration.

Biomacromolecules for Tissue Engineering: Emerging Biomimetic Strategies

Biomacromolecules used for tissue engineering must possess either inherent biochemical cues for tissue regeneration or be chemically modified to incorporate bioactive, tissue-specific moieties. To this end, many strategies have emerged recently in the field to both utilize novel bioinspired macromolecules for tissue engineering and apply bioconjugation strategies for the functionalization of biomacromolecules with tissue-specific cues and other biological properties of interest. Furthermore, biomacromolecules have been processed into more highly biomimetic and clinically deliverable scaffold and hydrogel systems using 3D printing and the fabrication of in situ forming hydrogels, respectively. To support these advances, tissue engineers have also pursued greater spatiotemporal control over macromolecular bioactivity and the modulation of scaffold and hydrogel properties in response to both physiological and external stimuli. This Perspective thus highlights a few notable advances and techniques in the usage of biomacromolecules for tissue engineering applications, including new bioinspired macromolecules, advanced hydrogel and scaffold fabrication techniques, and spatiotemporal control over biomacromolecule constructs.

Licorice isoliquiritigenin-encapsulated mesoporous silica nanoparticles for osteoclast inhibition and bone loss prevention

Mesoporous silica nanoparticles (MSNs) are extensively used in bone tissue regeneration and local drug delivery. However, the effects of MSNs alone on osteoclast formation and function, as well as the utilization of MSNs to deliver natural molecules against bone resorption, remain unexplored. Here, we report the development of licorice-derived bioactive flavonoid isoliquiritigenin (ISL)-encapsulated MSNs (MSNs-ISL) as a potent bone-bioresponsive nanoencapsulation system for prevention of osteoclast-mediated bone loss in vitro and in vivo.

Methods: We synthesized MSNs-ISL and then investigated the drug loading and release characteristics of the resulting nanoparticles. In vitro experiments on osteoclast differentiation and bone resorption were performed using mouse primary bone marrow-derived macrophages (BMMs). In vivo animal experiments were conducted using a lipopolysaccharide (LPS)-mediated calvarial bone erosion model.

Results: The resulting MSNs-ISL were spherical and highly monodispersed; they possessed a large specific surface area and superior biocompatibility, and allowed acid-sensitive sustained drug release. Compared with free ISL and MSNs alone, MSNs-ISL significantly and additively inhibited receptor activator of nuclear factor-κB ligand (RANKL)-induced osteoclast generation, decreased the size and quantity of sealing zones, and reduced the osteolytic capacity of osteoclasts in vitro. MSNs-ISL treatment also downregulated RANKL-stimulated mRNA expression of osteoclast-associated genes and transcription factors. Mechanistically, MSNs-ISL remarkably attenuated the RANKL-initiated expression of tumor necrosis factor receptor-associated factor 6 (TRAF6), phosphorylation of mitogen-activated protein kinases (MAPKs), and phosphorylation and degradation of inhibitor of κBα (IκBα), together with the nuclear translocation of nuclear factor-κB (NF-κB) p65 and the activator protein (AP)-1 component c-Fos. Moreover, MSNs-ISL almost completely restrained the expression of nuclear factor of activated T cells (NFATc1). Consistent with the in vitro results, MSNs-ISL could block osteoclast activity; relieve inflammation-related calvarial bone destruction in vivo; and suppress c-Fos, NFATc1, and cathepsin K expression levels.

Conclusion: Licorice ISL-encapsulated MSNs exhibit notable anti-osteoclastogenetic effects and protect against inflammatory bone destruction. Our findings reveal the feasibility of applying MSNs-ISL as an effective natural product-based bone-bioresponsive nanoencapsulation system to prevent osteoclast-mediated bone loss.

Sustained Release SDF-1α/TGF-β1-Loaded Silk Fibroin-Porous Gelatin Scaffold Promotes Cartilage Repair

Continuous delivery of growth factors to the injury site is crucial to creating a favorable microenvironment for cartilage injury repair. In the present study, we fabricated a novel sustained-release scaffold, stromal-derived factor-1α (SDF-1α)/transforming growth factor-β1 (TGF-β1)-loaded silk fibroin-porous gelatin scaffold (GSTS). GSTS persistently releases SDF-1α and TGF-β1, which enhance cartilage repair by facilitating cell homing and chondrogenic differentiation. Scanning electron microscopy showed that GSTS is a porous microstructure and the protein release assay demonstrated the sustainable release of SDF-1α and TGF-β1 from GSTS. Bone marrow-derived mesenchymal stem cells (MSCs) maintain high in vitro cell activity and excellent cell distribution and phenotype after seeding into GSTS. Furthermore, MSCs acquired enhanced chondrogenic differentiation capability in the TGF-β1-loaded scaffolds (GSTS or GST: loading TGF-β1 only) and the conditioned medium from SDF-1α-loaded scaffolds (GSTS or GSS: loading SDF-1α only) effectively promoted MSCs migration. GSTS was transplanted into the osteochondral defects in the knee joint of rats, and it could promote cartilage regeneration and repair the cartilage defects at 12 weeks after transplantation. Our study shows that GSTS can facilitate in vitro MSCs homing, migration, chondrogenic differentiation and SDF-1α and TGF-β1 have a synergistic effect on the promotion of in vivo cartilage forming. This SDF-1α and TGF-β1 releasing GSTS have promising therapeutic potential in cartilage repair.

Fluorine-contained hydroxyapatite suppresses bone resorption through inhibiting osteoclasts differentiation and function in vitro and in vivo

Objectives

Fluorine, an organic trace element, has been shown to unfavourably effect osteoclasts function at a low dose. Use of hydroxyapatite (HA) has been effective in exploring its roles in promoting bone repair. In this study, we used HA modified with fluorine to investigate whether it could influence osteoclastic activity in vitro and ovariectomy‐induced osteoclasts hyperfunction in vivo.

Materials and methods

Fluorohydroxyapatite (FHA) was obtained and characterized by scanning electron microscope (SEM). Osteoclasts proliferation and apoptosis treated with FHA were assessed by MTT and TUNEL assay. SEM, F‐actin, TRAP activity and bone resorption experiment were performed to determine the influence of FHA on osteoclasts differentiation and function. Moreover, HA and FHA were implanted into ovariectomized osteoporotic and sham surgery rats. Histology and Micro‐CT were examined for further verification.

Results

Fluorine released from FHA slowly and sustainably. FHA hampered osteoclasts proliferation, promoted osteoclasts apoptosis, suppressed osteoclasts differentiation and function. Experiments in vivo validated that FHA participation brought about an inhibitory effect on osteoclasts hyperfunction and less bone absorption.

Conclusion

The results indicated that FHA served as an efficient regulator to attenuate osteoclasts formation and function and was proposed as a candidature for bone tissue engineering applications.