Combining collagen and bioactive glasses for bone tissue engineering: a review

Decellularized Bone Matrix/45S5 Bioactive Glass Biocomposite Hydrogel-Based Constructs with Angiogenic and Osteogenic Properties: Ex Ovo and Ex Vivo Evaluations

Decellularized extracellular matrix is often used to create an in vivo-like environment that supports cell growth and proliferation, as it reflects the micro/macrostructure and molecular composition of tissues. On the other hand, bioactive glasses (BG) are surface-reactive glass-ceramics that can convert to hydroxyapatite in vivo and promote new bone formation. This study is designed to evaluate the key properties of a novel angiogenic and osteogenic biocomposite graft made of bovine decellularized bone matrix (DBM) hydrogel and 45S5 BG microparticles (10 and 20 wt%) to combine the existing superior properties of both biomaterial classes. Morphological, physicochemical, mechanical, and thermal characterizations of DBM and DBM/BG composite hydrogels are performed. Their in vitro biocompatibility is confirmed by cytotoxicity and hemocompatibility analyses. Ex vivo chick embryo aortic arch and ex ovo chick chorioallantoic membrane (CAM) assays reveal that the present pro-angiogenic property of DBM hydrogels is enhanced by the incorporation of BG. Histochemical stainings (Alcian blue and Alizarin red) and digital image analysis of ossification on hind limbs of embryos used in the CAM model reveal the osteogenic potential of biomaterials. The findings support the notion that the developed DBM/BG composite hydrogel constructs have the potential to be a suitable graft for bone repair.

Research Progress on Injectable Microspheres as New Strategies for the Treatment of Osteoarthritis Through Promotion of Cartilage Repair

Osteoarthritis (OA) is a degenerative disease caused by a variety of factors with joint pain as the main symptom, including fibrosis, chapping, ulcers, and loss of cartilage. Traditional treatment can only delay the progression of OA, and classical delivery system have many side effects. In recent years, microspheres have shown great application prospects in the field of OA treatment. Microspheres can support cells, reproduce the natural tissue microenvironment in vitro and in vivo, and are an efficient delivery system for the release of drugs or biological agents, which can promote cell proliferation, migration, and differentiation. Thus, they have been widely used in cartilage repair and regeneration. In this review, preparation processes, basic materials, and functional characteristics of various microspheres commonly used in OA treatment are systematically reviewed. Then it is introduced surface modification strategies that can improve the biological properties of microspheres and discussed a series of applications of microsphere functionalized scaffolds in OA treatment. Finally, based on bibliometrics research, the research development, future potential, and possible research hotspots of microspheres in the field of OA therapy is systematically and dynamically evaluated. The comprehensive and systematic review will bring new understanding to the field of microsphere treatment of OA.

Bioactive gelatin-sheets as novel biopapers to support prevascularization organized by laser-assisted bioprinting for bone tissue engineering

Despite significant advances in the management of patients with oral cancer, maxillofacial reconstruction after ablative surgery remains a clinical challenge. In bone tissue engineering, biofabrication strategies have been proposed as promising alternatives to solve issues associated with current therapies and to produce bone substitutes that mimic both the structure and function of native bone. Among them, laser-assisted bioprinting (LAB) has emerged as a relevant biofabrication method to print living cells and biomaterials with micrometric resolution onto a receiving substrate, also called 'biopaper'. Recent studies have demonstrated the benefits of prevascularization using LAB to promote vascularization and bone regeneration, but mechanical and biological optimization of the biopaper are needed. The aim of this study was to apply gelatin-sheet fabrication process to the development of a novel biopaper able to support prevascularization organized by LAB for bone tissue engineering applications. Gelatin-based sheets incorporating bioactive glasses (BGs) were produced using various freezing methods and crosslinking (CL) parameters. The different formulations were characterized in terms of microstructural, physical, mechanical, and biological properties in monoculture and coculture. Based on multi-criteria analysis, a rank scoring method was used to identify the most relevant formulations. The selected biopaper underwent additional characterization regarding its ability to support mineralization and vasculogenesis, its bioactivity potential andin vivodegradability. The biopaper 'Gel5wt% BG1wt%-slow freezing-CL160 °C 24 h' was selected as the best candidate, due to its suitable properties including high porosity (91.69 ± 1.55%), swelling ratio (91.61 ± 0.60%), Young modulus (3.97 × 104± 0.97 × 104Pa) but also its great cytocompatibility, osteogenesis and bioactivity properties. The preorganization of human umbilical vein endothelial cell using LAB onto this new biopaper led to the formation of microvascular networks. This biopaper was also shown to be compatible with 3D-molding and 3D-stacking strategies. This work allowed the development of a novel biopaper adapted to LAB with great potential for vascularized bone biofabrication.

Promote lipolysis in white adipocytes by magnetic hyperthermia therapy with Fe3O4microsphere-doped hydrogel

Obesity has become an ongoing global crisis, since it increases the risks of cardiovascular disease, type 2 diabetes, fatty liver, cognitive decline, and some cancers. Adipose tissue is closely associated with the disorder of lipid metabolism. Several efforts have been made toward the modulation of lipid accumulation, but have been hindered by poor efficiency of cellular uptake, low safety, and uncertain effective dosage. Herein, we design an Fe3O4microsphere-doped composite hydrogel (Fe3O4microspheres @chitosan/β-glycerophosphate/collagen), termed as Fe3O4@Gel, as the magnetocaloric agent for magnetic hyperthermia therapy (MHT), aiming to promote lipolysis in white adipocytes. The experimental results show that the obtained Fe3O4@Gel displays a series of advantages, such as fast sol-gel transition, high biocompatibility, and excellent magneto-thermal performance. MHT, which is realized by Fe3O4@Gel subjected to an alternating magnetic field, leads to reduced lipid accumulation, lower triglyceride content, and increased mitochondrial activity in white adipocytes. This work shows that Fe3O4@Gel-mediated MHT can effectively promote lipolysis in white adipocytesin vitro, which provides a potential approach to treat obesity and associated metabolic disorders.

Cell unit-inspired natural nano-based biomaterials as versatile building blocks for bone/cartilage regeneration

The regeneration of weight-bearing bone defects and critical-sized cartilage defects remains a significant challenge. A wide range of nano-biomaterials are available for the treatment of bone/cartilage defects. However, their poor compatibility and biodegradability pose challenges to the practical applications of these nano-based biomaterials. Natural biomaterials inspired by the cell units (e.g., nucleic acids and proteins), have gained increasing attention in recent decades due to their versatile functionality, compatibility, biodegradability, and great potential for modification, combination, and hybridization. In the field of bone/cartilage regeneration, natural nano-based biomaterials have presented an unparalleled role in providing optimal cues and microenvironments for cell growth and differentiation. In this review, we systematically summarize the versatile building blocks inspired by the cell unit used as natural nano-based biomaterials in bone/cartilage regeneration, including nucleic acids, proteins, carbohydrates, lipids, and membranes. In addition, the opportunities and challenges of natural nano-based biomaterials for the future use of bone/cartilage regeneration are discussed.

Intervertebral disc degeneration-Current therapeutic options and challenges

Degeneration of the intervertebral disc (IVD) is a normal part of aging. Due to the spine's declining function and the development of pain, it may affect one's physical health, mental health, and socioeconomic status. Most of the intervertebral disc degeneration (IVDD) therapies today focus on the symptoms of low back pain rather than the underlying etiology or mechanical function of the disc. The deteriorated disc is typically not restored by conservative or surgical therapies that largely focus on correcting symptoms and structural abnormalities. To enhance the clinical outcome and the quality of life of a patient, several therapeutic modalities have been created. In this review, we discuss genetic and environmental causes of IVDD and describe promising modern endogenous and exogenous therapeutic approaches including their applicability and relevance to the degeneration process.

Nanoscale borosilicate bioactive glass for regenerative therapy of full-thickness skin defects in rabbit animal model

Bioactive glass (BG) occupies a significant position in the field of hard and soft tissue regeneration. Different processing techniques and formulas have been introduced to expand their regenerative, angiogenic, and antibacterial properties. In the present study, a new formula of bborosilicate bioactive glass nanofibers was prepared and tested for its wound-healing efficacy in a rabbit animal model. The glass formula ((1-2) mol% of B₂O₃ (68-69) mol% of SiO2, and (29-30) mol% of CaO) was prepared primarily by the sol-gel technique followed by the electrospinning technique. The material was characterized for its ultrastructure using scanning electron microscopy, chemical composition using FTIR, and its dynamic in vitro biodegradability using ICP-AES. Twelve rabbits were subjected to surgical induction of full-thickness skin defects using a 1 cm² custom-made stainlessteel skin punch. The bioactive glass nanofibers were used as a grafting material in 6 experimental rabbits, while the defects in the remaining rabbits were considered as the negative control samples. All defects were assessed clinically for the decrease in wound size and clinical signs of healing and histologically for angiogenesis, collagen density, inflammatory response, cell recruitment, epithelial lining, and appendages at 1,2 and 3 weeks following the intervention. Structural analysis of the glass fibers confirmed their nano-size which ranged from 150 to 700 nm. Moreover, the chemical analysis confirmed the presence of SiO₂ and B₂O₃ groups within the structure of the nanofibers. Additionally, dynamic biodegradation analysis confirmed the rapid degradation of the material starting from the first 24 h and rapid leaching of calcium, silicon, and boron ions confirming its bioactivity. The wound healing study of the nanofibrous scaffold confirmed its ability to accelerate wound healing and the closure rate in healthy rabbits. Histological analysis of the defects confirmed the angiogenic, regenerative and antibacterial ability of the material throughout the study period. The results unveil the powerful therapeutic properties of the formed nanofibers and open a new gate for more experimental and clinical applications.

Human umbilical cord mesenchymal stem cells prevent glucocorticoid-induced osteonecrosis of the femoral head by promoting angiogenesis

The impairment of angiogenesis is an outstanding pathogenic characteristic of glucocorticoid (GC)-induced osteonecrosis of the femoral head (ONFH). Human umbilical cord mesenchymal stem cells (hUC-MSCs) have been used in several diseases models, which were reported to be involved in the angiogenesis. However, whether hUC-MSCs suppress the GC-induced ONFH via promoting angiogenesis is still unclear. hUC-MSCs were isolated from the Wharton's jelly using the explant culture method. A GC-induced ONFH model was established in vitro and in vivo. The angiogenesis, proliferation and migration ability of HMECs were determined using the tube-forming, CCK-8, transwell and scratching assays in vitro. The protective role of hUC-MSCs in GC-induced ONFH was evaluated using micro-CT scanning and histological, immunohistochemical (IHC) and Quantitative reverse transcription-polymerase chain reaction (qRT-PCR) assays in vivo. The results showed that hUC-MSCs treatment improved the tube-forming, proliferation and migration ability of HMECs in vitro. Moreover, hUC-MSCs treatment enhanced the integrity of trabecular bone of the femoral head, and the tube-forming ability in vivo. hUC-MSCs prevent the femoral head against necrosis and damage caused by GCs though promoting angiogenesis.

Harnessing electromagnetic fields to assist bone tissue engineering

Bone tissue engineering (BTE) emerged as one of the exceptional means for bone defects owing to it providing mechanical supports to guide bone tissue regeneration. Great advances have been made to facilitate the success of BTE in regenerating bone within defects. The use of externally applied fields has been regarded as an alternative strategy for BTE. Electromagnetic fields (EMFs), known as a simple and non-invasive therapy, can remotely provide electric and magnetic stimulation to cells and biomaterials, thus applying EMFs to assist BTE would be a promising strategy for bone regeneration. When combined with BTE, EMFs improve cell adhesion to the material surface by promoting protein adsorption. Additionally, EMFs have positive effects on mesenchymal stem cells and show capabilities of pro-angiogenesis and macrophage polarization manipulation. These advantages of EMFs indicate that it is perfectly suitable for representing the adjuvant treatment of BTE. We also summarize studies concerning combinations of EMFs and diverse biomaterial types. The strategy of combining EMFs and BTE receives encouraging outcomes and holds a promising future for effectively treating bone defects.

Extrusion 3D printing of a multiphase collagen‐based material: An optimized strategy to obtain biomimetic scaffolds with high shape fidelity

Extrusion printing represents one of the leading additive manufacturing techniques for tissue engineering purposes due to the possibility of achieving accurate control of the final shape and porosity of the scaffold. Despite many polymeric materials having already been optimized for this application, the processing of biopolymer-based systems still presents several limitations mainly ascribed to their poor rheological properties. Moreover, the introduction of inorganic components into the biomaterial formulation may introduce further difficulties related to system homogeneity, finally compromising its extrudability. In this context, the present study aimed at developing a new multi-phase biomaterial ink able to mimic the native composition of bone extracellular matrix, combining type-I-collagen with nano-hydroxyapatite and mesoporous bioactive glass nanoparticles. Starting from a comprehensive rheological assessment, computational-fluid-dynamics-based models were exploited to describe the material flow regime and define the optimal printing process planning. During printing, a gelatin-based bath was exploited to support the deposition of the material, while the gelation of collagen and its further chemical crosslinking with genipin enabled the stabilization of the printed structure, characterized by high shape fidelity. The developed strategy enables the extrusion printing of complex multi-phase systems and the design of high-precision biomimetic scaffolds with great potential for bone tissue engineering.

Smart biomaterials and their potential applications in tissue engineering

Smart biomaterials have been rapidly advancing ever since the concept of tissue engineering was proposed. Interacting with human cells, smart biomaterials can play a key role in novel tissue morphogenesis. Various aspects of biomaterials utilized in or being sought for the goal of encouraging bone regeneration, skin graft engineering, and nerve conduits are discussed in this review. Beginning with bone, this study summarizes all the available bioceramics and materials along with their properties used singly or in conjunction with each other to create scaffolds for bone tissue engineering. A quick overview of the skin-based nanocomposite biomaterials possessing antibacterial properties for wound healing is outlined along with skin regeneration therapies using infrared radiation, electrospinning, and piezoelectricity, which aid in wound healing. Furthermore, a brief overview of bioengineered artificial skin grafts made of various natural and synthetic polymers has been presented. Finally, by examining the interactions between natural and synthetic-based biomaterials and the biological environment, their strengths and drawbacks for constructing peripheral nerve conduits are highlighted. The description of the preclinical outcome of nerve regeneration in injury healed with various natural-based conduits receives special attention. The organic and synthetic worlds collide at the interface of nanomaterials and biological systems, producing a new scientific field including nanomaterial design for tissue engineering.

Comparison Capacity of Collagen Hydrogel and Collagen/Strontium Bioglass Nanocomposite Scaffolds With and Without mesenchymal Stem Cells in Regeneration of Critical Sized Bone Defect in a Rabbit Animal Model

Bone self-healing is limited and requires additional or external intervention to promote and accelerate bone regeneration. Therefore, the aim of this study was to investigate the potential capacity of hydrogel collagen (Co) nanocomposite alone, and in combination with 2% strontium (Co/BGSr2%) in presence of mesenchymal stem cells (MSCs) in full-thickness bone defect regeneration in the rabbit animal model. A total of 72 New Zealand white rabbits were randomly divided in 6 groups of 12 rabbits with full-thickness bone defect. In five groups, the bone defect was treated with MSC, Co, Co/BGSr2%, Co + MSCs, and Co/BGSr2% + MSCs. No treatment was done in the control group. The treatments were assessed radiographically, histopathologically, and immunohistochemically on days 14, 28, 42, and 56 post-treatment. The highest radiographical and histological scores were belonged to the Co/BGSr2% + MSC followed by Co + MSCs, Co/BGSr2%, Co, MSC, and the control groups. The highest and lowest mean expression level of osteocalcin was detected in the Co/BGSr2% + MSC and control groups by 28th dayof post-implantation, respectively. In contrast, the highest and lowest mean expression level of osteocalcin on day 56 post-implantation was belonged to the control and Co/BGSr2% + MSC, respectively. The Co/BGSr2% nanocomposite scaffold seeded with MSC can accelerate bone regeneration resulted from osteoblastic production of osteocalcin protein. Therefore, collagen hydrogel combined with 2% strontium in nanocomposite form is a suitable candidate scaffold for bone tissue engineering.

Effect of protein adsorption on the dissolution kinetics of silica nanoparticles

Nanoparticulate systems in the presence of proteins are highly relevant for various biomedical applications such as photo-thermal therapy and targeted drug delivery. These involve a complex interplay between the charge state of nanoparticles and protein, the resulting protein conformation, adsorption equilibrium and adsorption kinetics, as well as particle dissolution. SiO₂ is a common constituent of bioactive glasses used in biomedical applications. In this context, the dissolution behavior of silica particles in the presence of a model protein, bovine serum albumin (BSA), at physiologically relevant pH conditions was studied. Sedimentation analysis using an analytical ultracentrifuge showed that BSA in the supernatant solution is not affected by the presence of silica nanoparticles. However, zeta potential measurements revealed that the presence of the protein alters the particles' charge state. Adsorption and dissolution studies demonstrated that the presence of the protein significantly enhances the dissolution kinetics via interactions of positively charged amino acids in the protein with the negative silica surface and interaction of BSA with dissolved silicate species. Our study provides comprehensive insights into the complex interactions between proteins and oxide nanoparticles and establishes a reliable protocol paving the way for future investigations in more complex systems involving biological solutions as well as bioactive materials.

Sustainable Natural Bio-Origin Materials for Future Flexible Devices

Flexible devices serve as important intelligent interfaces in various applications involving health monitoring, biomedical therapies, and human-machine interfacing. To address the concern of electronic waste caused by the increasing usage of electronic devices based on synthetic polymers, bio-origin materials that possess environmental benignity as well as sustainability offer new opportunities for constructing flexible electronic devices with higher safety and environmental adaptivity. Herein, the bio-source and unique molecular structures of various types of natural bio-origin materials are briefly introduced. Their properties and processing technologies are systematically summarized. Then, the recent progress of these materials for constructing emerging intelligent flexible electronic devices including energy harvesters, energy storage devices, and sensors are introduced. Furthermore, the applications of these flexible electronic devices including biomedical implants, artificial e-skin, and environmental monitoring are summarized. Finally, future challenges and prospects for developing high-performance bio-origin material-based flexible devices are discussed. This review aims to provide a comprehensive and systematic summary of the latest advances in the natural bio-origin material-based flexible devices, which is expected to offer inspirations for exploitation of green flexible electronics, bridging the gap in future human-machine-environment interactions.

Recent Advances in Synthetic and Natural Biomaterials-Based Therapy for Bone Defects

Synthetic and natural biomaterials are a promising alternative for the treatment of critical-sized bone defects. Several parameters such as their porosity, surface, and mechanical properties are extensively pointed out as key points to recapitulate the bone microenvironment. Many biomaterials with this pursuit are employed to provide a matrix, which can supply the specific environment and architecture for an adequate bone growth. Nevertheless, some queries remain unanswered. This review discusses the recent advances achieved by some synthetic and natural biomaterials to mimic the native structure of bone and the manufacturing technology applied to obtain biomaterial candidates. The focus of this review is placed in the recent advances in the development of biomaterial-based therapy for bone defects in different types of bone. In this context, this review gives an overview of the potentialities of synthetic and natural biomaterials: polyurethanes, polyesters, hyaluronic acid, collagen, titanium, and silica as successful candidates for the treatment of bone defects.

Assessment of Collagen-Based Nanostructured Biomimetic Systems with a Co-Culture of Human Bone-Derived Cells

Osteoporosis is a worldwide disease resulting in the increase of bone fragility and enhanced fracture risk in adults. In the context of osteoporotic fractures, bone tissue engineering (BTE), i.e., the use of bone substitutes combining biomaterials, cells, and other factors, is considered a potential alternative to conventional treatments. Innovative scaffolds need to be tested in in vitro systems where the simultaneous presence of osteoblasts (OBs) and osteoclasts (OCs), the two main players of bone remodeling, is required to mimic their crosstalk and molecular cooperation. To this aim, two composite materials were developed, based on type I collagen, and containing either strontium-enriched mesoporous bioactive glasses or rod-like hydroxyapatite nanoparticles. The developed nanostructured systems underwent genipin chemical crosslinking and were then tested with an indirect co-culture of human trabecular bone-derived OBs and buffy coat-derived OC precursors, for 2–3 weeks. The favorable structural and biological properties of the materials proved to successfully support the viability, adhesion, and differentiation of cells, encouraging a further investigation of the developed bioactive systems as biomaterial inks for the 3D printing of more complex scaffolds for BTE.

Multifarious applications of bioactive glasses in soft tissue engineering

Tissue engineering (TE), a new paradigm in regenerative medicine, repairs and restores the diseased or damaged tissues and eliminates drawbacks associated with autografts and allografts. In this context, many biomaterials have been developed for regenerating tissues and are considered revolutionary in TE due to their flexibility, biocompatibility, and biodegradability. One such well-documented biomaterial is bioactive glasses (BGs), known for their osteoconductive and osteogenic potential and their abundant orthopedic and dental clinical applications. However, in the last few decades, the soft tissue regenerative potential of BGs has demonstrated great promise. Therefore, this review comprehensively covers the biological application of BGs in the repair and regeneration of tissues outside the skeleton system. BGs promote neovascularization, which is crucial to encourage host tissue integration with the implanted construct, making them suitable biomaterial scaffolds for TE. Moreover, they heal acute and chronic wounds and also have been reported to restore the injured superficial intestinal mucosa, aiding in gastroduodenal regeneration. In addition, BGs promote regeneration of the tissues with minimal renewal capacity like the heart and lungs. Besides, the peripheral nerve and musculoskeletal reparative properties of BGs are also reported. These results show promising soft tissue regenerative potential of BGs under preclinical settings without posing significant adverse effects. Albeit, there is limited bench-to-bedside clinical translation of elucidative research on BGs as they require rigorous pharmacological evaluations using standardized animal models for assessing biomolecular downstream pathways.

Collagen-based biocomposites inspired by bone hierarchical structures for advanced bone regeneration: ongoing research and perspectives

Bone is a hard-connective tissue composed of matrix, cells and bioactive factors with a hierarchical structure, where the matrix is mainly composed of type I collagen and hydroxyapatite. Collagen fibers assembled by collagen are the template for mineralization and make an important contribution to bone formation and the bone remodeling process. Therefore, collagen has been widely clinically used for bone/cartilage defect regeneration. However, pure collagen implants, such as collagen scaffolds or sponges, have limitations in the bone/cartilage regeneration process due to their poor mechanical properties and osteoinductivity. Different forms of collagen-based composites prepared by incorporating natural/artificial polymers or bioactive inorganic substances are characterized by their interconnected porous structure and promoting cell adhesion, while they improve the mechanical strength, structural stability and osteogenic activities of the collagen matrix. In this review, various forms of collagen-based biocomposites, such as scaffolds, sponges, microspheres/nanoparticles, films and microfibers/nanofibers prepared by natural/synthetic polymers, bioactive ceramics and carbon-based materials compounded with collagen are reviewed. In addition, the application of collagen-based biocomposites as cytokine, cell or drug (genes, proteins, peptides and chemosynthetic) delivery platforms for proangiogenesis and bone/cartilage tissue regeneration is also discussed. Finally, the potential application, research and development direction of collagen-based biocomposites in future bone/cartilage tissue regeneration are discussed.

Polymer Composite Sponges with Inherent Antibacterial, Hemostatic, Inflammation-Modulating and Proregenerative Performances for Methicillin-Resistant Staphylococcus aureus-Infected Wound Healing

Clinical wound management remains a major challenge due to massive bleeding, bacterial infection, and difficult wound healing after tissue trauma. To simultaneously address these issues, composite polymer sponges for accelerating drug-resistant bacterial infected wound healing are fabricated by facilely mixing sodium polyacrylate (PAAS), double quaternary ammonium salts-conjugated chitosan (QAS-CS), and collagen (COL) in aqueous solution, followed by lyophilization. Composite sponges (PAAS/QAS-CS/COL, PQC) show highly porous microstructures (porosity ≈90%) with moderate compress modulus (≈0.3 MPa), tensile strength (0.004 MPa), and high swelling ratio (≈3500%). Importantly, PQC sponge demonstrates superior hemostasis ability over commercially available CS sponge by inducing rapid hemagglutination, and exhibits significantly better antibacterial activity against both methicillin-resistant Staphylococcus aureus (MRSA) and Escherichia coli by destroying cell membrane and causing the leakage of bioactive components such as potassium ion and β-galactosidase from treated bacterial. Furthermore, PQC sponge can efficiently promote cell proliferation. Significantly, the sponge greatly expedites the regeneration of MRSA-infected full-thickness skin wound in rabbit by successfully eradicating bacterial infection, and reducing inflammation. PQC sponge also improves both early angiogenesis and blood vessel maturation at the wound site. Overall, this multifunctional sponge is a promising wound dressing for clinical use and holds great potential for rapid clinical translation.

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.

Biomimetic Scaffolds Obtained by Electrospinning of Collagen-Based Materials: Strategies to Hinder the Protein Denaturation

The use of biomaterials and scaffolds to boost bone regeneration is increasingly gaining interest as a complementary method to the standard surgical and pharmacological treatments in case of severe injuries and pathological conditions. In this frame, the selection of biomaterials and the accurate assessment of the manufacturing procedures are considered key factors in the design of constructs able to resemble the features of the native tissue and effectively induce specific cell responses. Accordingly, composite scaffolds based on type-I-collagen can mimic the composition of bone extracellular matrix (ECM), while electrospinning technologies can be exploited to produce nanofibrous matrices to resemble its architectural organization. However, the combination of collagen and electrospinning reported several complications due to the frequent denaturation of the protein and the variability of results according to collagen origin, concentration, and solvent. In this context, the strategies optimized in this study enabled the preparation of collagen-based electrospun scaffolds characterized by about 100 nm fibers, preserving the physico-chemical properties of the protein thanks to the use of an acetic acid-based solvent. Moreover, nanoparticles of mesoporous bioactive glasses were combined with the optimized collagen formulation, proving the successful design of composite scaffolds resembling the morphological features of bone ECM at the nanoscale.

Silica-Based Bioactive Glasses and Their Applications in Hard Tissue Regeneration: A Review

Regenerative medicine is a field that aims to influence and improvise the processes of tissue repair and restoration and to assist the body to heal and recover. In the field of hard tissue regeneration, bio-inert materials are being predominantly used, and there is a necessity to use bioactive materials that can help in better tissue-implant interactions and facilitate the healing and regeneration process. One such bioactive material that is being focused upon and studied extensively in the past few decades is bioactive glass (BG). The original bioactive glass (45S5) is composed of silicon dioxide, sodium dioxide, calcium oxide, and phosphorus pentoxide and is mainly referred to by its commercial name Bioglass. BG is mainly used for bone tissue regeneration due to its osteoconductivity and osteostimulation properties. The bioactivity of BG, however, is highly dependent on the compositional ratio of certain glass-forming system content. The manipulation of content ratio and the element compositional flexibility of BG-forming network developed other types of bioactive glasses with controllable chemical durability and chemical affinity with bone and bioactivity. This review article mainly discusses the basic information about silica-based bioactive glasses, including their composition, processing, and properties, as well as their medical applications such as in bone regeneration, as bone grafts, and as dental implant coatings.

Graphene-Based Biomaterials for Bone Regenerative Engineering: A Comprehensive Review of the Field and Considerations Regarding Biocompatibility and Biodegradation

Graphene and its derivatives have continued to garner worldwide interest due to their unique characteristics. Having expanded into biomedical applications, there have been efforts to employ their exceptional properties for the regeneration of different tissues, particularly bone. This article presents a comprehensive review on the usage of graphene-based materials for bone regenerative engineering. The graphene family of materials (GFMs) are used either alone or in combination with other biomaterials in the form of fillers in composites, coatings for both scaffolds and implants, or vehicles for the delivery of various signaling and therapeutic agents. The applications of the GFMs in each of these diverse areas are discussed and emphasis is placed on the characteristics of the GFMs that have implications in this regard. In tandem and of importance, this article evaluates the safety and biocompatibility of the GFMs and carefully elucidates how various factors influence the biocompatibility and biodegradability of this new class of nanomaterials. In conclusion, the challenges and opportunities regarding the use of the GFMs in regenerative engineering applications are discussed, and future perspectives for the developments in this field are proposed.

A Review of Bioactive Glass/Natural Polymer Composites: State of the Art

Collagen, gelatin, silk fibroin, hyaluronic acid, chitosan, alginate, and cellulose are biocompatible and non-cytotoxic, being attractive natural polymers for medical devices for both soft and hard tissues. However, such natural polymers have low bioactivity and poor mechanical properties, which limit their applications. To tackle these drawbacks, collagen, gelatin, silk fibroin, hyaluronic acid, chitosan, alginate, and cellulose can be combined with bioactive glass (BG) nanoparticles and microparticles to produce composites. The incorporation of BGs improves the mechanical properties of the final system as well as its bioactivity and regenerative potential. Indeed, several studies have demonstrated that polymer/BG composites may improve angiogenesis, neo-vascularization, cells adhesion, and proliferation. This review presents the state of the art and future perspectives of collagen, gelatin, silk fibroin, hyaluronic acid, chitosan, alginate, and cellulose matrices combined with BG particles to develop composites such as scaffolds, injectable fillers, membranes, hydrogels, and coatings. Emphasis is devoted to the biological potentialities of these hybrid systems, which look rather promising toward a wide spectrum of applications.

Are recent available blended collagen-calcium phosphate better than collagen alone or crystalline calcium phosphate? Radiotextural analysis of a 1-year clinical trial

OBJECTIVES

The purpose of this study is to compare bone regeneration properties of recently available collagen-calcium phosphate (C-CP) blend as bone substitute (BS) material in oral surgery with calcium phosphate (CP) as well as collagen material (Collagen). Is C-CP better than the classic loose CP, or is it at least equally effective in the jawbone regeneration with the superiority of a coherent consistency?

MATERIALS AND METHODS

This study included 102 patients during 12-month follow-up. All patients underwent the following surgical procedures: sinus lift (52patients) and tooth extraction (50patients). Patients were divided into 3 groups which are as follows: experimental group with C-CP, CP and pure Collagen as control groups. Texture analysis was performed in intra-oral radiographs. Analyses were performed in the MaZda 4.6 software. Average 2444-pixel ROIs were established in the image of BS materials and normal trabecular bone for texture comparison to evaluate the jawbone regeneration process. Four features were calculated and investigated.

RESULTS

Texture analyses revealed that all 4 features described the healing process well. Reference textural value of feature SumOfSqrs < 102.37 was soft tissue, DifEntr < 1.1 was not the bone, Entr < 2.62 was not a bone and LngREmph > 1.8 was soft tissue. For 12 months, bone regeneration was proved by 3 of 4 investigated features. Only Entr indicated to CP remnants in the ROI (p < 0.05).

CONCLUSIONS

This study proves that blended collagen-calcium phosphate as a BS material can bring satisfactory and predictable outcomes in jawbone regeneration.

CLINICAL RELEVANCE

Clinicians can choose a satisfactory and predictable material for bone regeneration treatment.

Acellular dense collagen-S53P4 bioactive glass hybrid gel scaffolds form more bone than stem cell delivered constructs

Dense collagen (DC) gels facilitate the osteoblastic differentiation of seeded dental pulp stem cells (DPSCs) and undergo rapid acellular mineralization when incorporated with bioactive glass particles, both in vitro and subcutaneously in vivo. However, the potential of DC-bioactive glass hybrid gels in delivering DPSCs for bone regeneration in an osseous site has not been investigated. In this study, the efficacies of both acellular and DPSC-seeded DC-S53P4 bioactive glass [(53)SiO₂-(23)Na₂O-(20)CaO-(4)P₂O₅, wt%] hybrid gels were investigated in a critical-sized murine calvarial defect. The incorporation of S53P4, an osteostimulative bioactive glass, into DC gels led to its accelerated acellular mineralization in simulated body fluid (SBF), in vitro, where hydroxycarbonated apatite was detected within 1 day. By day 7 in SBF, micro-mechanical analysis demonstrated an 8-fold increase in the compressive modulus of the mineralized gels. The in-situ effect of the bioactive glass on human-DPSCs within DC-S53P4 was evident, by their osteogenic differentiation in the absence of osteogenic supplements. The production of alkaline phosphatase and collagen type I was further increased when cultured in osteogenic media. This osteostimulative effect of DC-S53P4 constructs was confirmed in vivo, where after 8 weeks implantation, both acellular scaffolds and DPSC-seeded DC-S53P4 constructs formed mineralized and vascularized bone matrices with osteoblastic and osteoclastic cell activity. Surprisingly, however, in vivo micro-CT analysis confirmed that the acellular scaffolds generated larger volumes of bone, already visible at week 3 and exhibiting superior trabecular architecture. The results of this study suggest that DC-S53P4 scaffolds negate the need for stem cell delivery for effective bone tissue regeneration and may expedite their path towards clinical applications.

Bioglass incorporated methacrylated collagen bioactive ink for 3D printing of bone tissue

Bioactive 3D printed scaffolds are promising candidates for bone tissue engineering (BTE) applications. Here, we introduce a bioactive ink composed of Bioglass 45S5 (BG) and methacrylated collagen (CMA) for 3D printing of biomimetic constructs that resemble the organic and inorganic composition of native bone tissue. A uniform dispersion of BG particles within the collagen network improved stability and reduced swelling of collagen hydrogels. Rheological testing showed significant improvement in the yield stress and percent recovery of 3D printed constructs upon BG incorporation. Further, addition of BG improved the bone bioactivity of 3D printed constructs in stimulated body fluid. BG incorporated CMA (BG-CMA) constructs maintained high cell viability and enhanced alkaline phosphatase activity of human mesenchymal stem cells. In addition, cell-mediated calcium deposition was significantly higher on BG-CMA constructs, compared to CMA alone. In conclusion, 3D printed BG-CMA constructs have significant potential for use in BTE applications.

Additive manufacturing of PLA-based scaffolds intended for bone regeneration and strategies to improve their biological properties

Polylactic acid (PLA) is one of the most commonly used materials in the biomedical sector because of its processability, mechanical properties and biocompatibility. Among the different techniques that are feasible to process this biomaterial, additive manufacturing (AM) has gained attention recently, as it provides the possibility of tuning the design of the structures. This flexibility in the design stage allows the customization of the parts in order to optimize their use in the tissue engineering field. In the recent years, the application of PLA for the manufacture of bone scaffolds has been especially relevant, since numerous studies have proven the potential of this biomaterial for bone regeneration. This review contains a description of the specific requirements in the regeneration of bone and how the state of the art have tried to address them with different strategies to develop PLA-based scaffolds by AM techniques and with improved biofunctionality.

Collagen Hybrid Formulations for the 3D Printing of Nanostructured Bone Scaffolds: An Optimized Genipin-Crosslinking Strategy

Bone-tissue regeneration induced by biomimetic bioactive materials is the most promising approach alternative to the clinical ones used to treat bone loss caused by trauma or diseases such as osteoporosis. The goal is to design nanostructured bioactive constructs able to reproduce the physiological environment: By mimicking the natural features of bone tissue, the cell behavior during the regeneration process may be addressed. At present, 3D-printing technologies are the only techniques able to design complex structures avoiding constraints of final shape and porosity. However, this type of biofabrication requires complex optimization of biomaterial formulations in terms of specific rheological and mechanical properties while preserving high biocompatibility. In this work, we combined nano-sized mesoporous bioactive glasses enriched with strontium ions with type I collagen, to formulate a bioactive ink for 3D-printing technologies. Moreover, to avoid the premature release of strontium ions within the crosslinking medium and to significantly increase the material mechanical and thermal stability, we applied an optimized chemical treatment using ethanol-dissolved genipin solutions. The high biocompatibility of the hybrid system was confirmed by using MG-63 and Saos-2 osteoblast-like cell lines, further highlighting the great potential of the innovative nanocomposite for the design of bone-like scaffolds.

Toxicological evaluation of ionic liquid in a biological functional tissue construct model based on nano-hydroxyapatite/chitosan/gelatin hybrid scaffolds

The application of ionic liquid is attracting more attentions as green replacement for volatile organic solvents. However, the toxic effects and risks of ionic liquid in different biological systems for human health and environment are poorly evaluated. Among all ionic liquids, 1-ethyl-3-methylimidazolium diethylphosphate ([Emim]DEP-type) ionic liquid is still at the early phase of development, and its toxicity remains unclear. In this study, we fabricated a 3D biological functional tissue construct model based on nano-hydroxyapatite, chitosan and gelatin hybrid scaffold and evaluated its toxic effects of [Emim]DEP-type ionic liquid. As a control group, the examination of ionic liquid's toxic effects on the pre-osteoblast cell line (MC3T3-E1) was detected in 2D cultures. The MTT assay showed that [Emim]DEP-type ionic liquid inhibited the proliferation of cells on both 2D cultures and 3D tissue constructs. This effect was correlated with culturing time and concentration, while the IC50 on 3D scaffolds (12,566, 9015, 7896 μg/mL, at 24 h, 48 h and 72 h, respectively) was found significantly higher compared to 2D cultures (3959, 2226, 1884 μg/mL). Flow cytometry analysis and scanning electron microscope demonstrated that when [Emim]DEP-type ionic liquid acted on MC3T3-E1 cells for 48 h, the shape of 2D cells shrank, together with decreased surface adhesion.

Biofabrication of SDF-1 Functionalized 3D-Printed Cell-Free Scaffolds for Bone Tissue Regeneration

Large segmental bone defects occurring after trauma, bone tumors, infections or revision surgeries are a challenge for surgeons. The aim of our study was to develop a new biomaterial utilizing simple and cheap 3D-printing techniques. A porous polylactide (PLA) cylinder was printed and functionalized with stromal-derived factor 1 (SDF-1) or bone morphogenetic protein 7 (BMP-7) immobilized in collagen type I. Biomechanical testing proved biomechanical stability and the scaffolds were implanted into a 6 mm critical size defect in rat femur. Bone growth was observed via x-ray and after 8 weeks, bone regeneration was analyzed with µCT and histological staining methods. Development of non-unions was detected in the control group with no implant. Implantation of PLA cylinder alone resulted in a slight but not significant osteoconductive effect, which was more pronounced in the group where the PLA cylinder was loaded with collagen type I. Addition of SDF-1 resulted in an osteoinductive effect, with stronger new bone formation. BMP-7 treatment showed the most distinct effect on bone regeneration. However, histological analyses revealed that newly formed bone in the BMP-7 group displayed a holey structure. Our results confirm the osteoinductive character of this 3D-biofabricated cell-free new biomaterial and raise new options for its application in bone tissue regeneration.

Phosphorylated Chitosan Hydrogels Inducing Osteogenic Differentiation of Osteoblasts via JNK and p38 Signaling Pathways

Phosphorous-containing biopolymers have been applied to expedite the regeneration of damaged bone tissue by stimulating the function of phosphorous groups in natural bones. However, the underlying mechanism of phosphorous-containing biopolymers in promoting osteogenic differentiation is unclarified. Herein, we synthesized phosphorylated chitosan hydrogels by incorporating phosphocreatine into chitosan molecular chains under mild conditions. The introduction of phosphate groups improved properties of protein adsorption and calcium deposition without affecting the morphology of hydrogels. Our results showed that phosphorylated chitosan hydrogels could not only promote alkaline phosphatase activity and mineralization but also upregulate the expression of osteogenic-related genes and proteins. Meanwhile, application of c-Jun N-terminal kinase inhibitor SP600125 and p38 mitogen-activated protein kinase inhibitor SB203580 repressed the expression of osteogenic-related markers in gene and protein levels. To the best of our knowledge, it is reported for the first time that phosphorous-containing biopolymers promote osteogenic differentiation of osteoblasts via JNK and p38 signaling pathways.

Synthesis and characterization of osteoinductive visible light-activated adhesive composites with antimicrobial properties

Orthopedic surgical procedures based on the use of conventional biological graft tissues are often associated with serious post-operative complications such as immune rejection, bacterial infection, and poor osseointegration. Bioresorbable bone graft substitutes have emerged as attractive alternatives to conventional strategies because they can mimic the composition and mechanical properties of the native bone. Among these, bioactive glasses (BGs) hold great potential to be used as biomaterials for bone tissue engineering owing to their biomimetic composition and high biocompatibility and osteoinductivity. Here, we report the development of a novel composite biomaterial for bone tissue engineering based on the incorporation of a modified strontium- and lithium-doped 58S BG (i.e., BG-5/5) into gelatin methacryloyl (GelMA) hydrogels. We characterized the physicochemical properties of the BG formulation via different analytical techniques. Composite hydrogels were then prepared by directly adding BG-5/5 to the GelMA hydrogel precursor, followed by photocrosslinking of the polymeric network via visible light. We characterized the physical, mechanical, and adhesive properties of GelMA/BG-5/5 composites, as well as their in vitro cytocompatibility and osteoinductivity. In addition, we evaluated the antimicrobial properties of these composites in vitro, using a strain of methicillin-resistant Staphylococcus Aureus. GelMA/BG-5/5 composites combined the functional characteristics of the inorganic BG component, with the biocompatibility, biodegradability, and biomimetic composition of the hydrogel network. This novel biomaterial could be used for developing osteoinductive scaffolds or implant surface coatings with intrinsic antimicrobial properties and higher therapeutic efficacy.

Biomaterials for stem cell engineering and biomanufacturing

Recent years have witnessed the expansion of tissue failures and diseases. The uprising of regenerative medicine converges the sight onto stem cell-biomaterial based therapy. Tissue engineering and regenerative medicine proposes the strategy of constructing spatially, mechanically, chemically and biologically designed biomaterials for stem cells to grow and differentiate. Therefore, this paper summarized the basic properties of embryonic stem cells (ESCs), induced pluripotent stem cells (iPSCs) and adult stem cells. The properties of frequently used biomaterials were also described in terms of natural and synthetic origins. Particularly, the combination of stem cells and biomaterials for tissue repair applications was reviewed in terms of nervous, cardiovascular, pancreatic, hematopoietic and musculoskeletal system. Finally, stem-cell-related biomanufacturing was envisioned and the novel biofabrication technologies were discussed, enlightening a promising route for the future advancement of large-scale stem cell-biomaterial based therapeutic manufacturing.

Biocompatibility Investigation of Hybrid Organometallic Polymers for Sub-Micron 3D Printing via Laser Two-Photon Polymerisation

Hybrid organometallic polymers are a class of functional materials which can be used to produce structures with sub-micron features via laser two-photon polymerisation. Previous studies demonstrated the relative biocompatibility of Al and Zr containing hybrid organometallic polymers in vitro. However, a deeper understanding of their effects on intracellular processes is needed if a tissue engineering strategy based on these materials is to be envisioned. Herein, primary rat myogenic cells were cultured on spin-coated Al and Zr containing polymer surfaces to investigate how each material affects the viability, adhesion strength, adhesion-associated protein expression, rate of cellular metabolism and collagen secretion. We found that the investigated surfaces supported cellular growth to full confluency. A subsequent MTT assay showed that glass and Zr surfaces led to higher rates of metabolism than did the Al surfaces. A viability assay revealed that all surfaces supported comparable levels of cell viability. Cellular adhesion strength assessment showed an insignificantly stronger relative adhesion after 4 h of culture than after 24 h. The largest amount of collagen was secreted by cells grown on the Al-containing surface. In conclusion, the materials were found to be biocompatible in vitro and have potential for bioengineering applications.

Enhanced osseointegration of double network hydrogels via calcium polyphosphate incorporation for bone regeneration

To overcome the low mechanical strength and difficult bonding of hydrogels to bones which are the major limitations of hydrogels used in bone-regeneration, a new type of calcium polyphosphate incorporated into bioinspired alginate/polyacrylic acid (CPP/PAA-Alg) hybrid double network (DN) hydrogel with both high strength and enhanced osseointergration was prepared by a two-step polymerization with alginate and polyacrylic acid for bone regeneration. The morphology, mechanical properties, swelling, biocompatibility, osseointegration and osteogenic ability of this CPP/PAA-Alg DN hydrogel were investigated. The results show that CPP/PAA-Alg DN hydrogel with highly porous microstructure possesses high water absorption capacity and highly strength properties which meet the requirements of bone repairing. The results of in vitro studies revealed that the CPP/PAA-Alg DN hydrogels can support the spread of cells and promote the cell proliferation. Animal studies demonstrated that the CPP incorporated would enhance the osseointegration of DN hydrogel with host bone at an early stage after implantation to accelerate the regeneration of bone. This research may provide a new way to develop biocompatible biomaterials with high mechanical strength and good osseointegration to meet the needs of bone regeneration.

Development and Biocompatibility of Collagen-Based Composites Enriched with Nanoparticles of Strontium Containing Mesoporous Glass

In the last years bone tissue engineering has been increasingly indicated as a valid solution to meet the challenging requirements for a healthy bone regeneration in case of bone loss or fracture. In such a context, bioactive glasses have already proved their great potential in promoting the regeneration of new bone tissue due to their high bioactivity. In addition, their composition and structure enable us to incorporate and subsequently release therapeutic ions such as strontium, enhancing the osteogenic properties of the material. The incorporation of these inorganic systems in polymeric matrices enables the formulation of composite systems suitable for the design of bone scaffolds or delivery platforms. Among the natural polymers, type I collagen represents the main organic phase of bone and thus is a good candidate to develop biomimetic bioactive systems for bone tissue regeneration. However, alongside the specific composition and structure, the key factor in the design of new biosystems is creating a suitable interaction with cells and the host tissue. In this scenario, the presented study aimed at combining nano-sized mesoporous bioactive glasses produced by means of a sol–gel route with type I collagen in order to develop a bioactive hybrid formulation suitable for bone tissue engineering applications. The designed system has been fully characterized in terms of physico-chemical and morphological analyses and the ability to release Sr²⁺ ions has been studied observing a more sustained profile in presence of the collagenous matrix. With the aim to improve the mechanical and thermal stability of the resulting hybrid system, a chemical crosslinking approach using 4-star poly (ethylene glycol) ether tetrasuccinimidyl glutarate (4-StarPEG) has been explored. The biocompatibility of both non-crosslinked and 4-StarPEG crosslinked systems was evaluated by in vitro tests with human osteoblast-like MG-63 cells. Collected results confirmed the high biocompatibility of composites, showing a good viability and adhesion of cells when cultured onto the biomaterial samples.

Biomaterials for bone tissue engineering scaffolds: a review

Bone tissue engineering has been continuously developing since the concept of "tissue engineering" has been proposed. Biomaterials that are used as the basic material for the fabrication of scaffolds play a vital role in bone tissue engineering. This paper first introduces a strategy for literature search. Then, it describes the structure, mechanical properties and materials of natural bone and the strategies of bone tissue engineering. Particularly, it focuses on the current knowledge about biomaterials used in the fabrication of bone tissue engineering scaffolds, which includes the history, types, properties and applications of biomaterials. The effects of additives such as signaling molecules, stem cells, and functional materials on the performance of the scaffolds are also discussed.

A New Bioactive Glass/Collagen Hybrid Composite for Applications in Dentistry

Bioactive glasses (BGs) are currently employed in a wide range of medical and dentistry applications by virtue of their bone-bonding ability. The incorporation of BGs into a collagen matrix may be used to combine the regenerative potential of these materials with the specific biological advantages of collagen. However, most of the collagen/BG composites reported in the literature are scaffolds and there is a lack of moldable putties or injectable systems. Here, granules of an innovative BG containing strontium and magnesium were mixed with collagen and PEG to obtain a putty (BGMS/C) suitable for dental applications. For the sake of comparison, granules of 45S5 Bioglass^®, the gold standard among BGs, were used to prepare a 45S5/collagen putty. Both the composites were evaluated in vitro with respect to murine fibroblasts. The materials showed an excellent biocompatibility, making them interesting for possible applications in dentistry and reconstructive surgery. Moreover, BGMS/C seems to stimulate cell proliferation.

Intervertebral disc tissue engineering: A brief review

Intervertebral disc (IVD) degeneration (IDD) is associated with low back pain and significantly affects the patient's quality of life. Degeneration of the IVD alters disk height and the mechanics of the spine, leading to chronic segmental spinal instability. The pathophysiology of IVD disease is still not well understood. Current therapies for IDD include conservative and invasive approaches, but none of those treatments are able to restore the disc structure and function. Recently, tissue engineering techniques emerged as a possible approach to treat IDD, by replacing a damaged IVD with scaffolds and appropriate cells. Advances in manufacturing techniques, material processing and development, surface functionalization, drug delivery systems and cell incorporation furthered the development of tissue engineering therapies. In this review, biomaterial scaffolds and cell-based therapies for IVD regeneration are briefly discussed.

Bioactive glass ions induce efficient osteogenic differentiation of human adipose stem cells encapsulated in gellan gum and collagen type I hydrogels

BACKGROUND

Due to unmet need for bone augmentation, our aim was to promote osteogenic differentiation of human adipose stem cells (hASCs) encapsulated in gellan gum (GG) or collagen type I (COL) hydrogels with bioactive glass (experimental glass 2-06 of composition [wt-%]: Na₂O 12.1, K₂O 14.0, CaO 19.8, P₂O5 2.5, B₂O₃ 1.6, SiO₂ 50.0) extract based osteogenic medium (BaG OM) for bone construct development. GG hydrogels were crosslinked with spermidine (GG-SPD) or BaG extract (GG-BaG).

METHODS

Mechanical properties of cell-free GG-SPD, GG-BaG, and COL hydrogels were tested in osteogenic medium (OM) or BaG OM at 0, 14, and 21 d. Hydrogel embedded hASCs were cultured in OM or BaG OM for 3, 14, and 21 d, and analyzed for viability, cell number, osteogenic gene expression, osteocalcin production, and mineralization. Hydroxyapatite-stained GG-SPD samples were imaged with Optical Projection Tomography (OPT) and Selective Plane Illumination Microscopy (SPIM) in OM and BaG OM at 21 d. Furthermore, Raman spectroscopy was used to study the calcium phosphate (CaP) content of hASC-secreted ECM in GG-SPD, GG-BaG, and COL at 21 d in BaG OM.

RESULTS

The results showed viable rounded cells in GG whereas hASCs were elongated in COL. Importantly, BaG OM induced significantly higher cell number and higher osteogenic gene expression in COL. In both hydrogels, BaG OM induced strong mineralization confirmed as CaP by Raman spectroscopy and significantly improved mechanical properties. GG-BaG hydrogels rescued hASC mineralization in OM. OPT and SPIM showed homogeneous 3D cell distribution with strong mineralization in BaG OM. Also, strong osteocalcin production was visible in COL.

CONCLUSIONS

Overall, we showed efficacious osteogenesis of hASCs in 3D hydrogels with BaG OM with potential for bone-like grafts.