Effects of alginate/chondroitin sulfate-based hydrogels on bone defects healing

Dual-functional 3D-printed porous bioactive scaffold enhanced bone repair by promoting osteogenesis and angiogenesis

The treatment of bone defects is a difficult problem in orthopedics. The excessive destruction of local bone tissue at defect sites destroys blood supply and renders bone regeneration insufficient, which further leads to delayed union or even nonunion. To solve this problem, in this study, we incorporated icariin into alginate/mineralized collagen (AMC) hydrogel and then placed the drug-loaded hydrogel into the pores of a 3D-printed porous titanium alloy (AMCI/PTi) scaffold to prepare a bioactive scaffold with the dual functions of promoting angiogenesis and bone regeneration. The experimental results showed that the ACMI/PTi scaffold had suitable mechanical properties, sustained drug release function, and excellent biocompatibility. The released icariin and mineralized collagen (MC) synergistically promoted angiogenesis and osteogenic differentiation in vitro. After implantation into a rabbit radius defect, the composite scaffold showed a satisfactory effect in promoting bone repair. Therefore, this composite dual-functional scaffold could meet the requirements of bone defect treatment and provide a promising strategy for the repair of large segmental bone defects in clinic.

Plasma-Enabled Graphene Quantum Dot Hydrogel-Magnesium Composites as Bioactive Scaffolds for In Vivo Bone Defect Repair

Bioactive and mechanically stable metal-based scaffolds are commonly used for bone defect repair. However, conventional metal-based scaffolds induce nonuniform cell growth, limiting damaged tissue restoration. Here, we develop a plasma nanotechnology-enhanced graphene quantum dot (GQD) hydrogel-magnesium (Mg) composite scaffold for functional bone defect repair by integrating a bioresource-derived nitrogen-doped GQD (NGQD) hydrogel into the Mg ZK60 alloy. Each scaffold component brings major synergistic advantages over the current alloy-based state of the art, including (1) mechanical support of the cortical bone and calcium deposition by the released Mg2+ during degradation; (2) enhanced uptake, migration, and distribution of osteoblasts by the porous hydrogel; and (3) improved osteoblast adhesion and proliferation, osteogenesis, and mineralization by the NGQDs in the hydrogel. Through an in vivo study, the hybrid scaffold with the much enhanced osteogenic ability induced by the above synergy promotes a more rapid, uniform, and directional bone growth across the hydrogel channel, compared with the control Mg-based scaffold. This work provides insights into the design of multifunctional hybrid scaffolds, which can be applied in other areas well beyond the demonstrated bone defect repair.

A bioactive microparticle-loaded osteogenically enhanced bioprinted scaffold that permits sustained release of BMP-2

Extrusion-based bioprinting technology is widely used for tissue regeneration and reconstruction. However, the method that uses only hydrogel as the bioink base material exhibits limited biofunctional properties and needs improvement to achieve the desired tissue regeneration. In this study, we present a three-dimensionally printed bioactive microparticle-loaded scaffold for use in bone regeneration applications. The unique structure of the microparticles provided sustained release of growth factor for > 4 weeks without the use of toxic or harmful substances. Before and after printing, the optimal particle ratio in the bioink for cell viability demonstrated a survival rate of ≥ 85% over 7 days. Notably, osteogenic differentiation and mineralization-mediated by human periosteum-derived cells in scaffolds with bioactive microparticles-increased over a 2-week interval. Here, we present an alternative bioprinting strategy that uses the sustained release of bioactive microparticles to improve biofunctional properties in a manner that is acceptable for clinical bone regeneration applications.

A review on the synthesis and development of alginate hydrogels for wound therapy

Convenient and low-cost dressings can reduce the difficulty of wound treatment. Alginate gel dressings have the advantages of low cost and safe usage, and they have obvious potential for development in biomedical materials. Alginate gel dressings are currently a research area of great interest owing to their versatility, intelligent, and their application attempts in treating complex wounds. We present a detailed summary of the preparation of alginate hydrogels and a study of their performance improvement. Herein, we summarize the various applications of alginate hydrogels. The research focuses in this area mainly include designing multifunctional dressings for the treatment of various wounds and fabricating specialized dressings to assist physicians in the treatment of complex wounds (TOC). This review gives an outlook for future directions in the field of alginate hydrogel dressings. We hope to attract more research interest and studies in alginate hydrogel dressings, thus contributing to the creation of low-cost and highly effective wound treatment materials.

Partial sulfation of gellan gum produces cytocompatible, body temperature-responsive hydrogels

Gellan gum (GG) is a biodegradable polysaccharide and forms thermosensitive hydrogels by a helix-mediated mechanism. Unfortunately, the wide use of GG in tissue engineering has been restricted due to its dramatically higher gelation temperature than normal body temperature. Here, we show that partial sulfation of GG affords a cytocompatible body temperature-responsive hydrogel with an interesting thermoreversibility at 42 °C. The partial sulfation of GG was confirmed by FTIR, EDX and elemental analyses. The sulfated GGs (SGGs) had a higher swelling ratio and degradation in PBS compared to the neat GG. Based on the results of rheometry analysis, the SGG with a degree of sulfation of 0.27 (H3 sample) showed a gelation temperature close to the physiological temperature. In addition, the drop in mechanical properties of SGGs was compensated by a further calcium-mediated ionic crosslinking, where Young's modulus of H3 increased from 10.6 ± 1.9 kPa up to 38.4 ± 5.5 kPa. Finally, we showed that the partial sulfation reaction of GG is a simple and mild strategy to modify chemical structure of GG, and to produce a cytocompatible, body temperature-responsive hydrogel compared to other modifying reactions such as oxidation reaction.

Application of bioactive metal ions in the treatment of bone defects

The treatment of bone defects is an important problem in clinical practice. The rapid development of bone tissue engineering (BTE) may provide a new method for bone defect treatment. Metal ions have been widely studied in BTE and demonstrated a significant effect in promoting bone tissue growth. Different metal ions can be used to treat bone defects according to specific conditions, including promoting osteogenic activity, inhibiting osteoclast activity, promoting vascular growth, and exerting certain antibacterial effects. Multiple studies have confirmed that metal ions-modified composite scaffolds can effectively promote bone defect healing. By studying current extensive research on metal ions in the treatment of bone defects, this paper reviews the mechanism of metal ions in promoting bone tissue growth, analyzes the loading mode of metal ions, and lists some specific applications of metal ions in different types of bone defects. Finally, this paper summarizes the advantages and disadvantages of metal ions and analyzes the future research trend of metal ions in BTE. This article can provide some new strategies and methods for future research and applications of metal ions in the treatment of bone defects.

Chondroitin sulfate-based composites: a tour d'horizon of their biomedical applications

Chondroitin sulfate (CS), a natural anionic mucopolysaccharide, belonging to the glycosaminoglycan family, acts as the primary element of the extracellular matrix (ECM) of diverse organisms. It comprises repeating units of disaccharides possessing β-1,3-linked N-acetyl galactosamine (GalNAc), and β-1,4-linked D-glucuronic acid (GlcA), and exhibits antitumor, anti-inflammatory, anti-coagulant, anti-oxidant, and anti-thrombogenic activities. It is a naturally acquired bio-macromolecule with beneficial properties, such as biocompatibility, biodegradability, and immensely low toxicity, making it the center of attention in developing biomaterials for various biomedical applications. The authors have discussed the structure, unique properties, and extraction source of CS in the initial section of this review. Further, the current investigations on applications of CS-based composites in various biomedical fields, focusing on delivering active pharmaceutical compounds, tissue engineering, and wound healing, are discussed critically. In addition, the manuscript throws light on preclinical and clinical studies associated with CS composites. A short section on Chondroitinase ABC has also been canvassed. Finally, this review emphasizes the current challenges and prospects of CS in various biomedical fields.

3D-Printed Hybrid Collagen/GelMA Hydrogels for Tissue Engineering Applications

Bioprinting is an emerging technology involved in the fabrication of three-dimensional tissue constructs for the repair and regeneration of various tissues and organs. Collagen, a natural protein found abundantly in the extracellular matrix of several tissues, can be extracted from collagen-rich tissues of animals such as sheep, cows, rats, pigs, horses, birds, and marine animals. However, due to the poor printability of collagen bioinks, biocompatible collagen scaffolds that mimic the extracellular matrix (ECM) are difficult to fabricate using bioprinting techniques. Gelatin methacrylate (GelMA), a semi-synthetic polymer with tunable physical and chemical properties, has been found to be a promising biomaterial in various bioprinting applications. The printability of collagen can be improved by combining it with semi-synthetic polymers such as GelMA to develop hybrid hydrogels. Such hybrid hydrogels printed have also been identified to have enhanced mechanical properties. Hybrid GelMA meshes have not previously been prepared with collagen from ovine sources. This study provides a novel comparison between the properties of hybrid meshes with ovine skin and bovine hide collagen. GelMA (8% w/v) was integrated with three different concentrations (0.5%, 1%, and 2%) of bovine and ovine collagen forming hybrid hydrogels inks that were printed into meshes with enhanced properties. The maximum percentage of collagen suitable for integration with GelMA, forming hybrid hydrogels with a stable degradation rate was 1%. The water-soluble nature of ovine collagen promoted faster degradation of the hybrid meshes, although the structural crosslinking was identified to be higher than bovine hybrid meshes. The 1% bovine collagen hybrid meshes stood out in terms of their stable degradation rates.

Fabrication and Characterization of Chicken- and Bovine-Derived Chondroitin Sulfate/Sodium Alginate Hybrid Hydrogels

The physicochemical properties and microstructure of hybrid hydrogels prepared using sodium alginate (SA) and chondroitin sulfate (CS) extracted from two animal sources were investigated. SA-based hybrid hydrogels were prepared by mixing chicken- and bovine-derived CS (CCS and BCS, respectively) with SA at 1/3 and 2/3 (w/w) ratios. The results indicated that the evaporation water loss rate of the hybrid hydrogels increased significantly upon the addition of CS, whereas CCS/SA (2/3) easily absorbed moisture from the environment. The thermal stability of the BCS/SA (1/3) hybrid hydrogel was higher than that of CCS/SA (1/3) hybrid hydrogel, whereas the hardness and adhesiveness of the CCS/SA (1/3) hybrid hydrogel were lower and higher, respectively, than those of the BCS/SA (1/3) hybrid hydrogel. Low-field nuclear magnetic resonance experiments demonstrated that the immobilized water content of the CCS/SA (1/3) hybrid hydrogel was higher than that of the BCS/SA (1/3) hybrid hydrogel. FTIR showed that S=O characteristic absorption peak intensity of BCS/SA (2/3) was obviously higher, suggesting that BCS possessed more sulfuric acid groups than CCS. SEM showed that the hybrid hydrogels containing CCS have more compact porous microstructure and better interfacial compatibility compared to BCS.

Characteristics of Marine Biomaterials and Their Applications in Biomedicine

Oceans have vast potential to develop high-value bioactive substances and biomaterials. In the past decades, many biomaterials have come from marine organisms, but due to the wide variety of organisms living in the oceans, the great diversity of marine-derived materials remains explored. The marine biomaterials that have been found and studied have excellent biological activity, unique chemical structure, good biocompatibility, low toxicity, and suitable degradation, and can be used as attractive tissue material engineering and regenerative medicine applications. In this review, we give an overview of the extraction and processing methods and chemical and biological characteristics of common marine polysaccharides and proteins. This review also briefly explains their important applications in anticancer, antiviral, drug delivery, tissue engineering, and other fields.

AM1241-Loaded Poly(ethylene glycol)–Dithiothreitol Hydrogel Repairs Cranial Bone Defects by Promoting Vascular Endothelial Growth Factor and COL-1 Expression

Objective: To explore the repair effect of the prepared drug-loaded AM1241 poly(ethylene glycol)–dithiothreitol (PEG-DTT) hydrogel on cranial bone defects in SD rats.

Methods: The PEG-DTT hydrogel under borax catalysis was quickly prepared, and the characterization of the material was observed by a scanning electron microscope. The effect of AM1241 on cell activity and bone tissue differentiation was tested. The SD rat model of cranial bone defect was established, and the defect was repaired by injecting the prepared hydrogel into the defect. The defect was divided into four groups, namely, sham group, blank group, PEG-DTT group, and PEG-DTT + AM1241 group. The rats were euthanized, and whole cranial bone was taken out for micro-CT and histological observation.

Results: The prepared hydrogel is porous; it is liquid when heated to 80°C and a hydrogel when cooled to 25°C. 5–10 μM AM1241 increased osteoblast activity. A moderate amount of AM1241 can promote osteogenic differentiation. Both the PEG-DTT group and PEG-DTT + AM1241 group showed obvious new bone tissue formation, but the PEG-DTT + AM1241 group had a better effect. In addition, the new bone tissue in the PEG-DTT + AM1241 group was significantly more than that in the other groups.

Conclusion: The prepared AM1241-loaded PEG-DTT hydrogel showed a good repair effect on SD rats with cranial bone defects. It can be used as materials for cranial bone repair in SD rats with cranial bone defects, but the repair effect is weaker than that of normal bone. These results provide a theoretical and practical basis for its further clinical application.

Surface Modification of Poly(ether ether ketone) by Simple Chemical Grafting of Strontium Chondroitin Sulfate to Improve its Anti-Inflammation, Angiogenesis, Osteogenic Properties

Besides inducing osteogenic differentiation, the surface modification of poly(ether ether ketone) (PEEK) is highly expected to improve its angiogenic activity and reduce the inflammatory response in the surrounding tissue. Herein, strontium chondroitin sulfate is first attempted to be introduced into the surface of sulfonated PEEK (SPEEK-CS@Sr) based on the Schiff base reaction between PEEK and ethylenediamine (EDA) and the amidation reaction between EDA and chondroitin sulfate (CS). The surface characteristics of SPEEK-CS@Sr implant are systematically investigated, and its biological properties in vitro and in vivo are also evaluated. The results show that the surface of SPEEK-CS@Sr implant exhibits a 3D microporous structure and good hydrophilicity, and can steadily release Sr ions. Importantly, the SPEEK-CS@Sr not only displays excellent biocompatibility, but also can remarkably promote cell adhesion and spread, improve osteogenic activity and angiogenic activity, and reduce the inflammatory response compared to the original PEEK. Therefore, this study presents the surface modification of PEEK material by simple chemical grafting of strontium chondroitin sulfate to improve its angiogenesis, anti-inflammation, and osteogenic properties, and the as-fabricated SPEEK-CS@Sr has the potential to serve as a promising orthopedic implant in bone tissue engineering.

Hard, Soft, and Hard-and-Soft Drug Delivery Carriers Based on CaCO3 and Alginate Biomaterials: Synthesis, Properties, Pharmaceutical Applications

Because free therapeutic drug molecules often have adverse effects on normal tissues, deliver scanty drug concentrations and exhibit a potentially low efficacy at pathological sites, various drug carriers have been developed for preclinical and clinical trials. Their physicochemical and toxicological properties are the subject of extensive research. Inorganic calcium carbonate particles are promising candidates as drug delivery carriers owning to their hardness, porous internal structure, high surface area, distinctive pH-sensitivity, low degradability, etc, while soft organic alginate hydrogels are also widely used because of their special advantages such as a high hydration, bio-adhesiveness, and non-antigenicity. Here, we review these two distinct substances as well as hybrid structures encompassing both types of carriers. Methods of their synthesis, fundamental properties and mechanisms of formation, and their respective applications are described. Furthermore, we summarize and compare similarities versus differences taking into account unique advantages and disadvantages of these drug delivery carriers. Moreover, rational combination of both carrier types due to their performance complementarity (yin-&yang properties: in general, yin is referred to for definiteness as hard, and yang is broadly taken as soft) is proposed to be used in the so-called hybrid carriers endowing them with even more advanced properties envisioned to be attractive for designing new drug delivery systems.

Development and characterization of cannabidiol-loaded alginate copper hydrogel for repairing open bone defects in vitro

The clinical treatment of open bone defects caused by accidental bone trauma, bone tumors, bone diseases and bone infections is challenging. In this study, we designed and fabricated a multifunctional alginate-based hydrogel that contains cannabidiol (CBD), SA@Cu/CBD hydrogel, for repairing open bone defects. The results of physicochemical characterization showed that the SA@Cu/CBD hydrogel was successfully prepared and showed a suitable swelling ratio, high thermal stability, and stable mechanical properties. In vitro evaluation of antibacterial activity indicated that more than 90% of S. aureus and E. coli were inhibited compared to the control group. The ALP activity assay showed that the ALP expression level of MC3T3-E1cells in SA@Cu/CBD hydrogel was approximately 2-fold higher than that in the control group on day 7 and 14. Additionally, compared to the control group, the level of mineralized deposits in SA@Cu/CBD hydrogel was also improved by about 2 times on day 14. The PCR results indicated the mRNA expression levels of osteogenic markers (ALP, Col1α1, OCN, and RUNX2 genes) and angiogenic markers (EGFL6 and VEGF genes) in SA@Cu/CBD hydrogel were significantly upregulated compared to that in the control group, and the mRNA expression levels of critical inflammatory cytokines (TNF-α and IL-1β) in the SA@Cu/CBD hydrogel were significantly down-regulated compared to that in SA@Cu hydrogel. Taken together, these results demonstrated that the SA@Cu/CBD hydrogel showed significantly anti-bacterial, anti-inflammation, angiogenic and osteogenic activities in vitro studies. Thus, SA@Cu/CBD hydrogels may be a promising candidate in repairing open bone defects.

Injectable eggshell-derived hydroxyapatite-incorporated fibroin-alginate composite hydrogel for bone tissue engineering

Tissue engineering is a promising approach to repair and regenerate damaged or lost tissues or organs. In dental aspect, reconstruction of the resorbed alveolar bone after tooth extraction plays an important role in the success of dental substitution, especially in dental implant treatment. The hydroxyapatite (HA)-incorporated fibroin-alginate composite injectable hydrogel was fabricated to be used as scaffold for bone regeneration. HA was synthesized from eggshell biowaste. Fibroin was extracted from Bombyx mori cocoon. The synthesized HA, fibroin and alginate hydrogel were characterized. HA-incorporated fibroin-alginate hydrogel had decreased pore size and porosity compared with pure alginate hydrogel. Thermal analysis showed that hydrogel had a degradation peak of approximately 250 °C. Hydrogel could absorb water, with a swelling ratio of around 300% at 24 h. Hydrogel was degraded as time passed and almost completely degraded at day 7. Its compressive Young's modulus was approximately 0.04 ± 0.02 N/mm² to 0.10 ± 0.02 N/mm². Primary cytotoxicity test indicated non-toxic potential of the fabricated hydrogel. Increased ALP activity was observed in MC3T3-E1 cultured in HA-incorporated fibroin-alginate hydrogel. Results suggested the potential use of injectable HA fibroin-alginate hydrogel as dental scaffolding material. Further studies including in vivo examinations are needed prior to its clinical application.

Effectiveness of treating segmental bone defects with a synergistic co-delivery approach with platelet-rich fibrin and tricalcium phosphate

Several studies have applied tricalcium phosphate (TCP) or autografts in bone tissue engineering to enhance the clinical regeneration of bone. Unfortunately, there are several drawbacks related to the use of autografts, including a risk of infection, blood loss, limited quantities, and donor-site morbidities. Platelet-rich fibrin (PRF) is a natural extracellular matrix (ECM) biomaterial that possesses bioactive factors, which can generally be used in regenerative medicine. The goal of the present investigation was to develop osteoconductive TCP incorporated with bioactive PRF for bio-synergistic bone regeneration and examine the potential biological mechanisms and applications. Our in vitro results showed that PRF plus TCP had excellent biosafety and was favorable for initiating osteoblast cell attachment, slow release of bioactive factors, cell proliferation, cell migration, and ECM formation that potentially impacted bone repair. In a rabbit femoral segmental bone defect model, regeneration of bone was considerably augmented in defects locally implanted by PRF plus TCP according to radiographic and histologic examinations. Notably, the outcomes of this investigation suggest that the combination of PRF and TCP possesses novel synergistic and bio-inspired functions that facilitate bone regeneration.

Preparation of Alginate-Based Biomaterials and Their Applications in Biomedicine

Alginates are naturally occurring polysaccharides extracted from brown marine algae and bacteria. Being biocompatible, biodegradable, non-toxic and easy to gel, alginates can be processed into various forms, such as hydrogels, microspheres, fibers and sponges, and have been widely applied in biomedical field. The present review provides an overview of the properties and processing methods of alginates, as well as their applications in wound healing, tissue repair and drug delivery in recent years.

Glucuronoxylan-based quince seed hydrogel: A promising scaffold for tissue engineering applications

Natural gums and mucilages from plant-derived polysaccharides are potential candidates for a tissue-engineering scaffold by their ability of gelation and biocompatibility. Herein, we utilized Glucuronoxylan-based quince seed hydrogel (QSH) as a scaffold for tissue engineering applications. Optimization of QSH gelation was conducted by varying QSH and crosslinker glutaraldehyde (GTA) concentrations. Structural characterization of QSH was done by Fourier Transform Infrared Spectroscopy (FTIR). Furthermore, morphological and mechanical investigation of QSH was performed by Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM). The protein adsorption test revealed the suitability of QSH for cell attachment. Biocompatibility of QSH was confirmed by culturing NIH-3T3 mouse fibroblast cells on it. Cell viability and proliferation results revealed that optimum parameters for cell viability were 2 mg mL^-1 of QSH and 0.03 M GTA. SEM and DAPI staining results indicated the formation of spheroids with a diameter of approximately 300 μm. Furthermore, formation of extracellular matrix (ECM) microenvironment was confirmed with the Collagen Type-I staining. Here, it was demonstrated that the fabricated QSH is a promising scaffold for 3D cell culture and tissue engineering applications provided by its highly porous structure, remarkable swelling capacity and high biocompatibility.

The Marine Polysaccharide Ulvan Confers Potent Osteoinductive Capacity to PCL-Based Scaffolds for Bone Tissue Engineering Applications

Hybrid composites of synthetic and natural polymers represent materials of choice for bone tissue engineering. Ulvan, a biologically active marine sulfated polysaccharide, is attracting great interest in the development of novel biomedical scaffolds due to recent reports on its osteoinductive properties. Herein, a series of hybrid polycaprolactone scaffolds containing ulvan either alone or in blends with κ-carrageenan and chondroitin sulfate was prepared and characterized. The impact of the preparation methodology and the polysaccharide composition on their morphology, as well as on their mechanical, thermal, water uptake and porosity properties was determined, while their osteoinductive potential was investigated through the evaluation of cell adhesion, viability, and osteogenic differentiation of seeded human adipose-derived mesenchymal stem cells. The results verified the osteoinductive ability of ulvan, showing that its incorporation into the polycaprolactone matrix efficiently promoted cell attachment and viability, thus confirming its potential in the development of biomedical scaffolds for bone tissue regeneration applications.

Advances in Growth Factor Delivery for Bone Tissue Engineering

Shortcomings related to the treatment of bone diseases and consequent tissue regeneration such as transplants have been addressed to some extent by tissue engineering and regenerative medicine. Tissue engineering has promoted structures that can simulate the extracellular matrix and are capable of guiding natural bone repair using signaling molecules to promote osteoinduction and angiogenesis essential in the formation of new bone tissues. Although recent studies on developing novel growth factor delivery systems for bone repair have attracted great attention, taking into account the complexity of the extracellular matrix, scaffolding and growth factors should not be explored independently. Consequently, systems that combine both concepts have great potential to promote the effectiveness of bone regeneration methods. In this review, recent developments in bone regeneration that simultaneously consider scaffolding and growth factors are covered in detail. The main emphasis in this overview is on delivery strategies that employ polymer-based scaffolds for spatiotemporal-controlled delivery of both single and multiple growth factors in bone-regeneration approaches. From clinical applications to creating alternative structural materials, bone tissue engineering has been advancing constantly, and it is relevant to regularly update related topics.

Advancement of Nanobiomaterials to Deliver Natural Compounds for Tissue Engineering Applications

Recent advancement in nanotechnology has provided a wide range of benefits in the biological sciences, especially in the field of tissue engineering and wound healing. Nanotechnology provides an easy process for designing nanocarrier-based biomaterials for the purpose and specific needs of tissue engineering applications. Naturally available medicinal compounds have unique clinical benefits, which can be incorporated into nanobiomaterials and enhance their applications in tissue engineering. The choice of using natural compounds in tissue engineering improves treatment modalities and can deal with side effects associated with synthetic drugs. In this review article, we focus on advances in the use of nanobiomaterials to deliver naturally available medicinal compounds for tissue engineering application, including the types of biomaterials, the potential role of nanocarriers, and the various effects of naturally available medicinal compounds incorporated scaffolds in tissue engineering.