In vivo evaluation of porous hydroxyapatite/chitosan-alginate composite scaffolds for bone tissue engineering

The Synergetic Effect of 3D Printing and Electrospinning Techniques in the Fabrication of Bone Scaffolds

The primary goal of bone tissue engineering is to restore and rejuvenate bone defects by using a suitable three-dimensional scaffold, appropriate cells, and growth hormones. Various scaffolding methods are used to fabricate three-dimensional scaffolds, which provide the necessary environment for cell activity and bone formation. Multiple materials may be used to create scaffolds with hierarchical structures that are optimal for cell growth and specialization. This study examines a notion for creating an optimal framework for bone regeneration using a combination of the robocasting method and the electrospinning approach. Research indicates that the integration of these two procedures enhances the benefits of each method and provides a rationale for addressing their shortcomings via this combination. The hybrid approach is anticipated to provide a manufactured scaffold that can effectively replace bone defects while possessing the necessary qualities for bone regeneration.

Pioneering a paradigm shift in tissue engineering and regeneration with polysaccharides and proteins-based scaffolds: A comprehensive review

In the realm of modern medicine, tissue engineering and regeneration stands as a beacon of hope, offering the promise of restoring form and function to damaged or diseased organs and tissues. Central to this revolutionary field are biological macromolecules-nature's own blueprints for regeneration. The growing interest in bio-derived macromolecules and their composites is driven by their environmentally friendly qualities, renewable nature, minimal carbon footprint, and widespread availability in our ecosystem. Capitalizing on these unique attributes, specific composites can be tailored and enhanced for potential utilization in the realm of tissue engineering (TE). This review predominantly concentrates on the present research trends involving TE scaffolds constructed from polysaccharides, proteins and glycosaminoglycans. It provides an overview of the prerequisites, production methods, and TE applications associated with a range of biological macromolecules. Furthermore, it tackles the challenges and opportunities arising from the adoption of these biomaterials in the field of TE. This review also presents a novel perspective on the development of functional biomaterials with broad applicability across various biomedical applications.

Advancements in drug-loaded hydrogel systems for bone defect repair

Bone defects are primarily the result of high-energy trauma, pathological fractures, bone tumor resection, or infection debridement. The treatment of bone defects remains a huge clinical challenge. The current treatment options for bone defects include bone traction, autologous/allogeneic bone transplantation, gene therapy, and bone tissue engineering amongst others. With recent developments in the field, composite scaffolds prepared using tissue engineering techniques to repair bone defects are used more often. Among the various composite scaffolds, hydrogel exhibits the advantages of good biocompatibility, high water content, and degradability. Its three-dimensional structure is similar to that of the extracellular matrix, and as such it is possible to load stem cells, growth factors, metal ions, and small molecule drugs upon these scaffolds. Therefore, the hydrogel-loaded drug system has great potential in bone defect repair. This review summarizes the various natural and synthetic materials used in the preparation of hydrogels, in addition to the latest research status of hydrogel-loaded drug systems.

Fabrication and characterization of ceramic-polymer composite 3D scaffolds and demonstration of osteoinductive propensity with gingival mesenchymal stem cells

The fabrication of biomaterial 3D scaffolds for bone tissue engineering applications involves the usage of metals, polymers, and ceramics as the base constituents. Notwithstanding, the composite materials facilitating enhanced osteogenic differentiation/regeneration are endorsed as the ideally suited bone grafts for addressing critical-sized bone defects. Here, we report the successful fabrication of 3D composite scaffolds mimicking the ECM of bone tissue by using ∼30 wt% of collagen type I (Col-I) and ∼70 wt% of different crystalline phases of calcium phosphate (CP) nanomaterials [hydroxyapatite (HAp), beta-tricalcium phosphate (βTCP), biphasic hydroxyapatite (βTCP-HAp or BCP)], where pH served as the sole variable for obtaining these CP phases. The different Ca/P ratio and CP nanomaterials orientation in these CP/Col-I composite scaffolds not only altered the microstructure, surface area, porosity with randomly oriented interconnected pores (80-450 μm) and mechanical strength similar to trabecular bone but also consecutively influenced the bioactivity, biocompatibility, and osteogenic differentiation potential of gingival-derived mesenchymal stem cells (gMSCs). In fact, BCP/Col-I, as determined from micro-CT analysis, achieved the highest surface area (∼42.6 m2 g-1) and porosity (∼85%), demonstrated improved bioactivity and biocompatibility and promoted maximum osteogenic differentiation of gMSCs among the three. Interestingly, the released Ca2+ ions, as low as 3 mM, from these scaffolds could also facilitate the osteogenic differentiation of gMSCs without even subjecting them to osteoinduction, thereby attesting these CP/Col-I 3D scaffolds as ideally suited bone graft materials.

State of Innovation in Alginate-Based Materials

This review article presents past and current alginate-based materials in each application, showing the widest range of alginate's usage and development in the past and in recent years. The first segment emphasizes the unique characteristics of alginates and their origin. The second segment sets alginates according to their application based on their features and limitations. Alginate is a polysaccharide and generally occurs as water-soluble sodium alginate. It constitutes hydrophilic and anionic polysaccharides originally extracted from natural brown algae and bacteria. Due to its promising properties, such as gelling, moisture retention, and film-forming, it can be used in environmental protection, cosmetics, medicine, tissue engineering, and the food industry. The comparison of publications with alginate-based products in the field of environmental protection, medicine, food, and cosmetics in scientific articles showed that the greatest number was assigned to the environmental field (30,767) and medicine (24,279), whereas fewer publications were available in cosmetic (5692) and food industries (24,334). Data are provided from the Google Scholar database (including abstract, title, and keywords), accessed in May 2023. In this review, various materials based on alginate are described, showing detailed information on modified composites and their possible usage. Alginate's application in water remediation and its significant value are highlighted. In this study, existing knowledge is compared, and this paper concludes with its future prospects.

Open fractures: Current treatment perspective

Severe open fractures present challenges to orthopaedic surgeons worldwide, with increased risks of significant complications. Although different global regions have different resources and systems, there continue to be many consistent approaches to open fracture care. Management of these complex injures continues to evolve in areas ranging from timing of initial operative debridement to the management of critical-sized bone defects. This review, compiled by representative members of the International Orthopaedic Trauma Association, focuses on several critical areas of open fracture management, including antibiotic administration, timing of debridement, bone loss, soft tissue management, and areas of need for future investigation.

Mechanical, biocompatibility and antibacterial studies of gelatin/polyvinyl alcohol/silkfibre polymeric scaffold for bone tissue engineering

The current study focuses on the incorporation of natural polymers (gelatin, silk fibre) and synthetic (polyvinyl alcohol) polymer towards the fabrication of a novel composite for bone tissue engineering. The Electrospinning method was used to fabricate the novel gelatin/polyvinyl alcohol/silk fibre scaffold. XRD, FTIR and SEM-EDAX analysis was performed to characterize the composite. The characterized composite was investigated for its physical properties (porosity and mechanical studies) and biological studies (antimicrobial activity, hemocompatibility, bioactivity). The fabricated composite showed high porosity and the highest tensile strength of 34 MPa, with elongation at a break of 35.82 for the composite. The antimicrobial activity of the composite was studied and the zone of inhibition was measured around 51 ± 0.54 for E. coli, 48 ± 0.48 for S. aureus and 50 ± 0.26 for C. albicans. The hemolytic % was noted around 1.36 for the composite and the bioactivity assay revealed the formation of apatite on composite surfaces.

Surgical cotton microfibers loaded with proteins and apatite: A potential platform for bone tissue engineering

Tissue engineering has emerged as the best alternative to replacing damaged tissue/organs. However, the cost of scaffold materials continues to be a significant obstacle; thus, developing inexpensive scaffolds is strongly encouraged. In this study, cellulose microfibers (C), gelatin (G), egg white (EW), and nanohydroxyapatite (nHA) were assembled into a quaternary scaffold using EDC-NHS crosslinking, followed by freeze-drying method. Cellulose microfibers as a scaffold have only received a limited amount of research due to the absence of an intrinsic three-dimensional structure. Gelatin, more likely to interact chemically with collagen, was used to provide a stable structure to the cellulose microfibers. EW was supposed to provide the scaffold with numerous cell attachment sites. nHA was chosen to enhance the scaffold's bone-bonding properties. Physico-chemical, mechanical, and biological characterization of scaffolds were studied. In-vitro using MG-63 cells and in-ovo studies revealed that all scaffolds were biocompatible. The results of the DPPH assay demonstrate the ability of CGEWnHA to reduce free radicals. The CGEWnHA scaffold exhibits the best properties with 56.84 ± 28.45 μm average pore size, 75 ± 1.4 % porosity, 39.23 % weight loss, 109.19 ± 0.98 kPa compressive modulus, and 1.72 Ca/P ratio. As a result, the constructed CGEWnHA scaffold appears to be a viable choice for BTE applications.

Alginates Combined with Natural Polymers as Valuable Drug Delivery Platforms

Alginates (ALG) have been used in biomedical and pharmaceutical technologies for decades. ALG are natural polymers occurring in brown algae and feature multiple advantages, including biocompatibility, low toxicity and mucoadhesiveness. Moreover, ALG demonstrate biological activities per se, including anti-hyperlipidemic, antimicrobial, anti-reflux, immunomodulatory or anti-inflammatory activities. ALG are characterized by gelling ability, one of the most frequently utilized properties in the drug form design. ALG have numerous applications in pharmaceutical technology that include micro- and nanoparticles, tablets, mucoadhesive dosage forms, wound dressings and films. However, there are some shortcomings, which impede the development of modified-release dosage forms or formulations with adequate mechanical strength based on pure ALG. Other natural polymers combined with ALG create great potential as drug carriers, improving limitations of ALG matrices. Therefore, in this paper, ALG blends with pectins, chitosan, gelatin, and carrageenans were critically reviewed.

Hemostatic Alginate/Nano-Hydroxyapatite Composite Aerogel Loaded with Tranexamic Acid for the Potential Protection against Alveolar Osteitis

Wound control in patients on anticoagulants is challenging and often leads to poor hemostasis. They have a higher tendency to develop alveolar osteitis after tooth extraction. The application of a hemostatic dressing that has a high absorbing capacity and is loaded with an antifibrinolytic drug could help in controlling the bleeding. Alginate/nano-hydroxyapatite (SA/Nano-HA) composite aerogels loaded with tranexamic acid (TXA) were prepared. Nano-HA served as a reinforcing material for the alginate matrix and a source of calcium ions that helps in blood clotting. It influenced the porosity and the water uptake capacity. TXA release from SA/Nano-HA aerogels showed a biphasic profile for up to 4 h. Blood coagulation studies were performed on human whole blood. The TXA-loaded aerogel significantly reduced the clotting time by 69% compared to the control (p < 0.0001). Recalcification time was significantly reduced by 80% (p < 0.0001). Scanning electron microscopy analysis revealed the porous nature of the aerogels and the ability of the optimum aerogel to activate and adhere platelets to its porous surface. The cell migration assay showed that there was a delay in wound healing caused by the TXA aerogel compared to the control sample after treating human fibroblasts. Results suggest that the developed aerogel is a promising dressing that will help in hemostasis after tooth extraction.

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

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

Mineralization in a Critical Size Bone-Gap in Sheep Tibia Improved by a Chitosan-Calcium Phosphate-Based Composite as Compared to Predicate Device

Deacetylated chitin derivatives have been widely studied for tissue engineering purposes. This study aimed to compare the efficacy of an injectable product containing a 50% deacetylated chitin derivative (BoneReg-Inject™) and an existing product (chronOS Inject^®) serving as a predicate device. A sheep model with a critical size drill hole in the tibial plateau was used. Holes of 8 mm diameter and 30 mm length were drilled bilaterally into the proximal area of the tibia and BoneReg-Inject™ or chronOS Inject^® were injected into the right leg holes. Comparison of resorption and bone formation in vivo was made by X-ray micro-CT and histological evaluation after a live phase of 12 weeks. Long-term effects of BoneReg-Inject™ were studied using a 13-month live period. Significant differences were observed in (1) amount of new bone within implant (p < 0.001), higher in BoneReg-Inject^TM, (2) signs of cartilage tissue (p = 0.003), more pronounced in BoneReg-Inject^TM, and (3) signs of fibrous tissue (p < 0.001), less pronounced in BoneReg-Inject^TM. Mineral content at 13 months postoperative was significantly higher than at 12 weeks (p < 0.001 and p < 0.05, for implant core and rim, respectively). The data demonstrate the potential of deacetylated chitin derivatives to stimulate bone formation.

Biological Response to a Novel Hybrid Polyoligomer: in vitro and in vivo Models

The aim of the study is to evaluate biocompatibility of a novel hybrid polyoligomer in in vitro and in vivo models.

Effect of cellulose nanocrystals on chitosan/PVA/nano β-TCP composite scaffold for bone tissue engineering application

The need for an ideal tissue construct has lead to the search of a myriad of polymer composites with desirable properties. The nature, location and type of tissue to be regenerated determines the type of material to be used. A bone construct has its own requirements such as osteoconductivity, mineralization tendency, synchronized degradation rate, osteogenic differentiation potential etc, which results in search of new possible combination of materials aimed to improve tissue response. The present study involves fabrication of Chitosan/Polyvinyl alcohol (PVA)/β-Tricalcium Phosphate (β-TCP)/Cellulose nanocrystals (CNC) porous composite by freeze drying process to be used as bone tissue engineering matrix. CNCs were isolated by acid hydrolysis of cellulose derived from pistachio shells. The prepared scaffold samples were characterized by Fourier-transform infrared spectroscopy (FTIR), Thermogravimetric analysis (TGA), Atomic Force Microscopy (AFM), Scanning Electron Microscopy (SEM) and X-RAY Diffraction analysis (XRD). The scaffolds exhibited refinement in pore morphology and increased mineralization tendency on increasing CNC concentration. Samples with 1% and 5% CNC concentration have deposited apatite crystals with Ca/P ratio of 1.61 and 1.66 which is very close to the stoichiometric ratio of natural bone apatite. Compressive modulus of CS/PVA/β-TCP/CNC composite increased on increasing the CNC concentration to 5%. The highest cell viability was recorded in scaffolds with 5% CNC content. Though cell attachment tendency was observed in all samples but the samples with 5 and 10% CNC content demonstrated higher cell densities with significant calcium depositions when cultured for 72 h. Samples with 5% CNC concentration also possessed highest cell differentiation capabilities.

Vancomycin Hydrochloride Loaded Hydroxyapatite Mesoporous Microspheres with Micro/Nano Surface Structure to Increase Osteogenic Differentiation and Antibacterial Ability

As infection induced by the implant will lead to operation failure, the implant material must be endowed with certain antibacterial properties. Hydroxyapatite (HA) mesoporous microspheres have been widely used in bone repair due to their advantages, including simple synthesis, good osteogenic properties and drug loading capacity. In this study, vancomycin hydrochloride-loaded mesoporous hydroxyapatite microspheres with micro/nanosurface structures were synthesized to increase osteogenic differentiation and antibacterial ability. Phytic acid (IP6) was used as a template to prepare mesoporous hydroxyapatite microspheres composed of fibres, flakes and smooth surfaces by the hydrothermal homogeneous precipitation method, and the corresponding specific surface areas were 65.20 m²/g, 75.13 m²/g and 71.27 m²/g, respectively. Vancomycin hydrochloride (Van) was used as the drug model to study the drug loading and release characteristics of the microspheres, as well as the in vitro antibacterial properties after treatment. In addition, during cocultivation with MC3T3-E1 preosteoblasts, HA microspheres assembled via flakes exhibited better cell compatibility, which promoted cell proliferation, alkaline phosphatase (ALP) activity, and the formation of calcium nodules and increased the expression of osteogenic differentiation-related proteins such as Runx-2, osteopontin (OPN) and collagen I (COL I). These results indicated that the HA microspheres prepared in this experiment have broad application prospects in drug delivery systems and bone repair.

Skeletal microenvironment system utilising bovine bone scaffold co-cultured with human osteoblasts and osteoclast-like cells

A three-dimensional ex vivo bone cell culture system mimicking the skeletal system is useful for bone tissue engineering and as drug discovery platforms. The present study aimed to establish a three-dimensional skeletal culture system using native bovine bone scaffolds and human bone cells. Bovine bone scaffolds were cultured with human foetal osteoblasts 1.19 and human peripheral blood mononuclear cells for 21 days under standard culture conditions. The following groups were established: Decalcified unseeded bone scaffold (DUBS) as baseline control, decalcified seeded bone scaffold (DSBS) to mimic osteoporosis condition and undecalcified seeded bone scaffold to mimic normal condition. The scaffold's porosity and cell attachment on the scaffolds were determined using scanning electron microscopy. Histological evaluation was used to examine changes in trabecular bone structure. Dual-energy X-ray absorptiometry analysis was performed to determine the bone mineral density (BMD) and bone mineral content (BMC) of the scaffolds. A compression test was performed to examine the total biomechanical strength of the scaffolds. The trabecular thickness and number increased, while the trabecular separationwas reduced slightly in DSBS than in DUBS (P>0.05). The BMD and BMC increased significantly (P<0.05), while the compressive strength only increased slightly in DSBS than in DUBS (P>0.05). In conclusion, the ex vivo skeletal microenvironment comprising native bovine bone scaffolds seeded with bone cells is structurally, functionally and mechanically comparable with natural bone. This system may be used as a platform to understand bone physiology and screen for potential drug candidates.

Synthetic and Bone tissue engineering graft substitutes: What is the future?

The management of large segmental bone defects caused by trauma or disease remains clinically challenging within orthopaedics. The major impediment to bone healing with current treatment options is insufficient vascularization and incorporation of graft material. Lack of rapid adequate vascularization leads to cellular necrosis within the inner regions of the implanted material and a failure of bone regeneration. Current treatment options for critical size bone defects include the continued "gold standard" autograft, allograft, synthetic bone graft substitutes, vascularized fibular graft, induced membrane technique, and distraction osteogenesis. Bone tissue engineering (BTE) remains an exciting prospect for the treatment of large segmental bone defects; however, current clinical integration of engineered scaffolds remains low. We believe that the barrier to clinical application of bone tissue engineering constructs lies in the lack of concomitant vascularization of these scaffolds. This mini-review outlines the progress made and the significant limitations remaining in successful clinical incorporation of engineered synthetic bone substitutes for segmental defects.

Urine-derived stem cells loaded onto a chitosan-optimized biphasic calcium-phosphate scaffold for repairing large segmental bone defects in rabbits

The treatment of large segmental bone defects can be challenging for orthopedic surgeons. The development of bone tissue engineering technology, including the selection of seeding cells and the construction of scaffolds, provides a promising solution. In this study, we investigated osteogenic differentiation of human urine-derived stem cells (hUSCs, a newly identified class of stem cells), and developed a novel porous hybrid scaffold using biphasic calcium phosphate (BCP) bioceramic ornamented with chitosan sponges (CS). We combined hUSCs with a CS/BCP hybrid scaffold to construct tissue-engineered bone and evaluated whether the combination promotes bone regeneration in large segmental bone defects in rabbits. The study showed that hUSCs can differentiate into osteoblasts, and the hUSCs adhered, proliferated, and differentiated on CS/BCP hybrid scaffolds. Micro-computed tomography measurements, biomechanical detection, and histological analyses revealed that the combination of hUSCs and the CS/BCP hybrid scaffold enhanced bone regeneration more effectively compared with conventional pure BCP scaffolds, indicating that hUSCs can be used as a cell source for bone tissue engineering and that cell-scaffold-based biomimetic bone may be a promising approach to the repair of bone defects.

Chitosan-based blends for biomedical applications

Polysaccharides are the most abundant naturally available carbohydrate polymers; composed of monosaccharide units covalently connected together. Chitosan is the most widely used polysaccharides because of its exceptional biocompatibility, mucoadhesion, and chemical versatility. However, it suffers from a few drawbacks, e.g. poor mechanical properties and antibacterial activity for biomedical applications. Blending chitosan with natural or synthetic polymers may not merely improve its physicochemical and mechanical properties, but may also improve its bioactivity-induced properties. This review paper summarizes progress in chitosan blends with biodegradable polymers and polysaccharides and their biomedical applications. Blends of chitosan with alginate, starch, cellulose, pectin and dextran and their applications were particularly addressed. The critical and challenging aspects as well as the future ahead of the use of chitosan-based blends were eventually enlightened.

Alginate and alginate composites for biomedical applications

Alginate is an edible heteropolysaccharide that abundantly available in the brown seaweed and the capsule of bacteria such as Azotobacter sp. and Pseudomonas sp. Owing to alginate gel forming capability, it is widely used in food, textile and paper industries; and to a lesser extent in biomedical applications as biomaterial to promote wound healing and tissue regeneration. This is evident from the rising use of alginate-based dressing for heavily exuding wound and their mass availability in the market nowadays. However, alginate also has limitation. When in contact with physiological environment, alginate could gelate into softer structure, consequently limits its potential in the soft tissue regeneration and becomes inappropriate for the usage related to load bearing body parts. To cater this problem, wide range of materials have been added to alginate structure, producing sturdy composite materials. For instance, the incorporation of adhesive peptide and natural polymer or synthetic polymer to alginate moieties creates an improved composite material, which not only possesses better mechanical properties compared to native alginate, but also grants additional healing capability and promote better tissue regeneration. In addition, drug release kinetic and cell viability can be further improved when alginate composite is used as encapsulating agent. In this review, preparation of alginate and alginate composite in various forms (fibre, bead, hydrogel, and 3D-printed matrices) used for biomedical application is described first, followed by the discussion of latest trend related to alginate composite utilization in wound dressing, drug delivery, and tissue engineering applications.

Biomechanical Evaluation of an Injectable Alginate / Dicalcium Phosphate Cement Composites for Bone Tissue Engineering

Biocompatible dicalcium phosphate (DCP) cements are widely used as bone repair materials. In this study, we aimed to investigate the impact of different amounts of sodium alginate (SA) on the microstructural, mechanical, and biological properties of DCP cements. Beta-tricalcium phosphate (β-TCP) was prepared using a microwave-assisted wet precipitation system. Lattice parameters of the obtained particles determined from X-ray diffraction (XRD), were in good match with a standard phase of β-TCP. Scanning electron microscopy (SEM) examination revealed that the particles were in globular shape. Furthermore, all functional groups of β-TCP were also detected using Fourier-transform infrared spectroscopy (FTIR) spectra. DCP cement (pure phase) was synthesized using monocalcium phosphate monohydrate (MCPM)/β-TCP powder mixture blended with 1.0 mL of water. SA/DCP cement composites were synthesized by dissolving different amounts of SA into water (1.0 mL) to obtain different final concentrations (0.5%, 1%, 2% and 3%). The prepared cements were characterized with XRD, SEM, FTIR and Thermogravimetric analysis (TGA). XRD results showed that pure DCP and SA/DCP cements were in a good match with Monetite phase. SEM results confirmed that addition of SA inhibited the growth of DCP particles. Setting time and injectability behaviour were significantly improved upon increasing the SA amount into DCP cements. In vitro biodegradation was evaluated using Simulated body fluid (SBF) over 21 days at 37 °C. The highest cumulative weight loss (%) in SBF was observed for 2.0% SA/DCP (about 26.52%) after 21 days of incubation. Amount of Ca²⁺ ions released in SBF increased with the addition of SA. DCP and SA/DCP cements showed the highest mechanical strength after 3 days of incubation in SBF and declined with prolonged immersion periods. In vitro cell culture experiments were conducted using Dental pulp stem cells (DPSCs). Viability and morphology of cells incubated in extract media of DCP and SA/DCP discs after 24 h incubation was studied with MTT assay and fluorescence microscopy imaging, respectively. All cements were cytocompatible and viability of cells incubated in extracts of cements was higher than observed in the control group. Based on the outcomes, SA/DCP bone cements have a promising future to be utilized as bone filler.

Efficacy of Nano Composite Porous 3D Scaffold of Crab Shell and Al-Kharit Histological and Radiological for Bone Repair in Vivo

The present study was conducted to evaluate the effect of scaffold fabricated from Nano crab shell and Al-kharit (Papyrus Vaccine) for enhancing the healing of the experimentally induced bone defect in dogs. For this purpose, twenty healthy adult mongrel dogs were used in this study which divided randomly into two equal groups, under general anesthesia, 1 cm bone gap was created in the distal part of the tibia, that fixed by bone plate and screws. Nano crab shell scaffold was implanted. All experimental animals showed normal situation without any infection at the site of operation, while the radiography showed a periosteal and endosteal reaction. Moreover, the gaps were bridged faster in the treated group as compared with the control group. Treated animals showed new bone formation which represented by obvious lamellar bone, haversian canal and osteocyte cells in 90 days. In conclusion, the Nano crab shell scaffold gave better acceleration in the bone healing process, also this scaffolds may provide insight into the clinical repair of large bone defects

Stem Cell-Friendly Scaffold Biomaterials: Applications for Bone Tissue Engineering and Regenerative Medicine

Bone is a dynamic organ with high regenerative potential and provides essential biological functions in the body, such as providing body mobility and protection of internal organs, regulating hematopoietic cell homeostasis, and serving as important mineral reservoir. Bone defects, which can be caused by trauma, cancer and bone disorders, pose formidable public health burdens. Even though autologous bone grafts, allografts, or xenografts have been used clinically, repairing large bone defects remains as a significant clinical challenge. Bone tissue engineering (BTE) emerged as a promising solution to overcome the limitations of autografts and allografts. Ideal bone tissue engineering is to induce bone regeneration through the synergistic integration of biomaterial scaffolds, bone progenitor cells, and bone-forming factors. Successful stem cell-based BTE requires a combination of abundant mesenchymal progenitors with osteogenic potential, suitable biofactors to drive osteogenic differentiation, and cell-friendly scaffold biomaterials. Thus, the crux of BTE lies within the use of cell-friendly biomaterials as scaffolds to overcome extensive bone defects. In this review, we focus on the biocompatibility and cell-friendly features of commonly used scaffold materials, including inorganic compound-based ceramics, natural polymers, synthetic polymers, decellularized extracellular matrix, and in many cases, composite scaffolds using the above existing biomaterials. It is conceivable that combinations of bioactive materials, progenitor cells, growth factors, functionalization techniques, and biomimetic scaffold designs, along with 3D bioprinting technology, will unleash a new era of complex BTE scaffolds tailored to patient-specific applications.

Hydroxyapatite Nanoparticles Fortified Xanthan Gum-Chitosan Based Polyelectrolyte Complex Scaffolds for Supporting the Osteo-Friendly Environment

Nanoparticle-reinforced polymer-based scaffolding matrices as artificial bone-implant materials are potential suitors for bone regenerative medicine as they simulate the native bone. In the present work, a series of bioinspired, osteoconductive tricomposite scaffolds made up of nano-hydroxyapatite (NHA) embedded xanthan gum-chitosan (XAN-CHI) polyelectrolyte complex (PEC) are explored for their bone-regeneration potential. The Fourier transform infrared spectroscopy studies confirmed complex formation between XAN and CHI and showed strong interactions between the NHA and PEC matrix. The X-ray diffraction studies indicated regulation of the nanocomposite (NC) scaffold crystallinity by the physical cues of the PEC matrix. Further results exhibited that the XAN-CHI/NHA5 scaffold, with a 50/50 (polymer/NHA) ratio, has optimized porous structure, appropriate compressive properties, and sufficient swelling ability with slower degradation rates, which are far better than those of CHI/NHA and other XAN-CHI/NHA NC scaffolds. The simulated body fluid studies showed XAN-CHI/NHA5 generated apatite-like surface structures of a Ca/P ratio ∼1.66. Also, the in vitro cell-material interaction studies with MG-63 cells revealed that relative to the CHI/NHA NC scaffold, the cellular viability, attachment, and proliferation were better on XAN-CHI/NHA scaffold surfaces, with XAN-CHI/NHA5 specimens exhibiting an effective increment in cell spreading capacity compared to XAN-CHI/NHA4 and XAN-CHI/NHA6 specimens. The presence of an osteo-friendly environment is also indicated by enhanced alkaline phosphatase expression and protein adsorption ability. The higher expression of extracellular matrix proteins, such as osteocalcin and osteopontin, finally validated the induction of differentiation of MG-63 cells by tricomposite scaffolds. In summary, this study demonstrates that the formation of PEC between XAN and CHI and incorporation of NHA in XAN-CHI PEC developed tricomposite scaffolds with robust potential for use in bone regeneration applications.

Recent Trends in Three-Dimensional Bioinks Based on Alginate for Biomedical Applications

Three-dimensional (3D) bioprinting is an appealing and revolutionary manufacturing approach for the accurate placement of biologics, such as living cells and extracellular matrix (ECM) components, in the form of a 3D hierarchical structure to fabricate synthetic multicellular tissues. Many synthetic and natural polymers are applied as cell printing bioinks. One of them, alginate (Alg), is an inexpensive biomaterial that is among the most examined hydrogel materials intended for vascular, cartilage, and bone tissue printing. It has also been studied pertaining to the liver, kidney, and skin, due to its excellent cell response and flexible gelation preparation through divalent ions including calcium. Nevertheless, Alg hydrogels possess certain negative aspects, including weak mechanical characteristics, poor printability, poor structural stability, and poor cell attachment, which may restrict its usage along with the 3D printing approach to prepare artificial tissue. In this review paper, we prepare the accessible materials to be able to encourage and boost new Alg-based bioink formulations with superior characteristics for upcoming purposes in drug delivery systems. Moreover, the major outcomes are discussed, and the outstanding concerns regarding this area and the scope for upcoming examination are outlined.

In vivo Regeneration of Mineralized Bone Tissue in Anisotropic Biomimetic Sponges

In the last two decades, alginate scaffolds have been variously studied as extracellular matrix analogs for tissue engineering. However, relevant evidence is still lacking concerning their ability to mimic the microenvironment of hierarchical tissues such as bone. Hence, an increasing amount of attention has recently been devoted to the fabrication of macro/microporous sponges with pore anisotropy able to more accurately replicate the cell niche structure as a trigger for bioactive functionalities. This paper presents an in vivo study of alginate sponges with anisotropic microporous domains (MAS) formed by ionic crosslinking in the presence of different fractions (30 or 50% v) of hydroxyapatite (HA). In comparison with unloaded sponges (MAS0), we demonstrated that HA confers peculiar physical and biological properties to the sponge, depending upon the inorganic fraction used, enabling the sponge to bio-mimetically support the regeneration of newly formed bone. Scanning electron microscopy analysis showed a preferential orientation of pores, ascribable to the physical constraints exerted by HA particles during the pore network formation. Energy dispersive spectroscopy (EDS) and X-Ray diffraction (XRD) confirmed a chemical affinity of HA with the native mineral phase of the bone. In vitro studies via WST-1 assay showed good adhesion and proliferation of human Dental Pulp-Mesenchymal Stem Cells (hDP-MSC) that increased in the presence of the bioactive HA signals. Moreover, in vivo studies via micro-CT and histological analyses of a bone model (e.g., a rat calvaria defect) confirmed that the maximum osteogenic response after 90 days was achieved with MAS30, which supported good regeneration of the calvaria defect without any evidence of inflammatory reaction. Hence, all of the results suggested that MAS is a promising scaffold for supporting the regeneration of hard tissues in different body compartments.

Microspheres containing biosynthesized silver nanoparticles with alginate-nano hydroxyapatite for biomedical applications

Scaffolding system plays an important role in the development of artificial bone for treatment of defective or diseased bone tissue. In the present work, we have developed microspheres (COS-Ag-Alg-HA) containing chitooligosaccharide (COS) coated silver nanoparticles (Ag NPs) with alginate (Alg) and hydroxyapatite (HA) as bone graft substitutes. The developed microspheres were characterized through various analytical techniques such as UV-visible spectroscopy, Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction, field emission scanning electron microscopy with EDX and evaluated the mechanical strength by using universal testing machine. In addition to this, antimicrobial activity and biocompatibility of the developed microspheres were evaluated with pathogenic microbes and osteoblast-like cells, respectively. Results suggest that microspheres are rigid, and strong chemical interactions were observed between the materials. The size of the microspheres was ranging from 1.5 ± 0.5 to 4.0 ± 0.5 mm. Significant microbial inhibition was observed against Staphylococcus aureus, and the developed microspheres are biocompatible with osteoblast-like cells. Based on the aforementioned finding results, the developed microsphere is proposed to be a potential candidate for bone tissue repair and regeneration.

A Concise Review on Tissue Engineered Artificial Skin Grafts for Chronic Wound Treatment: Can We Reconstruct Functional Skin Tissue In Vitro?

Chronic wounds occur as a consequence of a prolonged inflammatory phase during the healing process, which precludes skin regeneration. Typical treatment for chronic wounds includes application of autografts, allografts collected from cadaver, and topical delivery of antioxidant, anti-inflammatory, and antibacterial agents. Nevertheless, the mentioned therapies are not sufficient for extensive or deep wounds. Moreover, application of allogeneic skin grafts carries high risk of rejection and treatment failure. Advanced therapies for chronic wounds involve application of bioengineered artificial skin substitutes to overcome graft rejection as well as topical delivery of mesenchymal stem cells to reduce inflammation and accelerate the healing process. This review focuses on the concept of skin tissue engineering, which is a modern approach to chronic wound treatment. The aim of the article is to summarize common therapies for chronic wounds and recent achievements in the development of bioengineered artificial skin constructs, including analysis of biomaterials and cells widely used for skin graft production. This review also presents attempts to reconstruct nerves, pigmentation, and skin appendages (hair follicles, sweat glands) using artificial skin grafts as well as recent trends in the engineering of biomaterials, aiming to produce nanocomposite skin substitutes (nanofilled polymer composites) with controlled antibacterial activity. Finally, the article describes the composition, advantages, and limitations of both newly developed and commercially available bioengineered skin substitutes.

Natural Polymeric Scaffolds in Bone Regeneration

Despite considerable advances in microsurgical techniques over the past decades, bone tissue remains a challenging arena to obtain a satisfying functional and structural restoration after damage. Through the production of substituting materials mimicking the physical and biological properties of the healthy tissue, tissue engineering strategies address an urgent clinical need for therapeutic alternatives to bone autografts. By virtue of their structural versatility, polymers have a predominant role in generating the biodegradable matrices that hold the cells in situ to sustain the growth of new tissue until integration into the transplantation area (i.e., scaffolds). As compared to synthetic ones, polymers of natural origin generally present superior biocompatibility and bioactivity. Their assembly and further engineering give rise to a wide plethora of advanced supporting materials, accounting for systems based on hydrogels or scaffolds with either fibrous or porous architecture. The present review offers an overview of the various types of natural polymers currently adopted in bone tissue engineering, describing their manufacturing techniques and procedures of functionalization with active biomolecules, and listing the advantages and disadvantages in their respective use in order to critically compare their actual applicability potential. Their combination to other classes of materials (such as micro and nanomaterials) and other innovative strategies to reproduce physiological bone microenvironments in a more faithful way are also illustrated. The regeneration outcomes achieved in vitro and in vivo when the scaffolds are enriched with different cell types, as well as the preliminary clinical applications are presented, before the prospects in this research field are finally discussed. The collection of studies herein considered confirms that advances in natural polymer research will be determinant in designing translatable materials for efficient tissue regeneration with forthcoming impact expected in the treatment of bone defects.

Nanocomposite scaffold seeded with mesenchymal stem cells for bone repair

The mechanical property of bone tissue scaffolds is one of the most important aspects in bone tissue engineering that has remained problematic. In our previous study, we fabricated a three-dimensional scaffold from nano-hydroxyapatite/gelatin (nHA/Gel) and investigated its efficiency in promoting bone regeneration both in vitro and in vivo. In the present study, the effect of adding silicon carbide (SiC) on the mechanical and biological behaviors of the nHA/Gel/SiC and bone regeneration in vivo were determined. nHA and SiC were synthesized and characterized by the X-ray diffraction pattern and transmission electron microscope image. Layer solvent casting, freeze drying, and lamination techniques were applied to prepare these scaffolds. Then, the biocompatibility and cell adhesion behavior of the synthesized nHA/Gel/SiC scaffolds were investigated. For in vivo studies, rats were categorized into three groups: blank defect, blank scaffold, and rat bone marrow mesenchymal stem cells (rBM-MSCs)/scaffold. After 1, 4, and 12 weeks post-injury, the rats were sacrificed and the calvaria were harvested. Sections with a thickness of 5 µm thickness were prepared and stained with hematoxylin-eosin and Masson's Trichrome, and immunohistochemistry was performed. Our results showed that SiC effectively increased the mechanical properties of the nHA/Gel/SiC scaffold. No significant differences were observed in biocompatibility, cell adhesion, and cytotoxicity of the nHA/Gel/SiC in comparison with the nHA/Gel nanocomposite. Based on histological and immunohistochemical studies, both osteogenesis and collagenization were significantly higher in the rBM-MSCs/scaffold group, quantitatively and qualitatively. The present study strongly suggests the potential of SiC as an alternative strategy to improve the mechanical and biological properties of bone tissue engineering scaffolds, and shows that the pre-seeded nHA/Gel/SiC scaffold with rBM-MSCs improves osteogenesis in the engineered bone implant.

Application of Chitosan in Bone and Dental Engineering

Chitosan is a deacetylated polysaccharide from chitin, the natural biopolymer primarily found in shells of marine crustaceans and fungi cell walls. Upon deacetylation, the protonation of free amino groups of the d-glucosamine residues of chitosan turns it into a polycation, which can easily interact with DNA, proteins, lipids, or negatively charged synthetic polymers. This positive-charged characteristic of chitosan not only increases its solubility, biodegradability, and biocompatibility, but also directly contributes to the muco-adhesion, hemostasis, and antimicrobial properties of chitosan. Combined with its low-cost and economic nature, chitosan has been extensively studied and widely used in biopharmaceutical and biomedical applications for several decades. In this review, we summarize the current chitosan-based applications for bone and dental engineering. Combining chitosan-based scaffolds with other nature or synthetic polymers and biomaterials induces their mechanical properties and bioactivities, as well as promoting osteogenesis. Incorporating the bioactive molecules into these biocomposite scaffolds accelerates new bone regeneration and enhances neovascularization in vivo.

Chitin/Chitosan: Versatile Ecological, Industrial, and Biomedical Applications

Chitin is a linear polysaccharide of N-acetylglucosamine, which is highly abundant in nature and mainly produced by marine crustaceans. Chitosan is obtained by hydrolytic deacetylation. Both polysaccharides are renewable resources, simply and cost-effectively extracted from waste material of fish industry, mainly crab and shrimp shells. Research over the past five decades has revealed that chitosan, in particular, possesses unique and useful characteristics such as chemical versatility, polyelectrolyte properties, gel- and film-forming ability, high adsorption capacity, antimicrobial and antioxidative properties, low toxicity, and biocompatibility and biodegradability features. A plethora of chemical chitosan derivatives have been synthesized yielding improved materials with suggested or effective applications in water treatment, biosensor engineering, agriculture, food processing and storage, textile additives, cosmetics fabrication, and in veterinary and human medicine. The number of studies in this research field has exploded particularly during the last two decades. Here, we review recent advances in utilizing chitosan and chitosan derivatives in different technical, agricultural, and biomedical fields.

Chitosan as a Bone Scaffold Biomaterial

The current standard of care for bone reconstruction, whether secondary to injury, nonunion, cancer resection, or idiopathic bone loss, is autologous bone grafting. Alternatives to autograft and allograft bone substitutes currently being researched are synthetic and natural graft materials that are able to guide bone regeneration. One promising material currently being researched is chitosan, a highly versatile, naturally occurring polysaccharide, derived from the exoskeleton of arthropods that is comprised of glucosamine and N-acetylglucosamine. Research on chitosan as a bone scaffold has been promising. Chitosan is efficacious in bone regeneration due to its lack of immunogenicity, its biodegradability, and its physiologic features. Chitosan combined with growth factors and/or other scaffold materials has proven to be an effective alternative to autologous bone grafts. Additionally, current studies have shown that it can provide the additional benefit of a local drug delivery system. As research in the area of bone scaffolding continues to grow, further clinical research on chitosan in conjunction with growth factors, proteins, and alloplastic materials will likely be at the forefront.

Immunocompatibility of poly(ethylene glycol)-penetrated alginate–chitosan hydrogels

Scaffold-guided tissue regeneration using hydrogels has been emerging as an ideal alternative for the management of terminal-stage organ damage. Design of scaffolds for tissue regrowth mainly focuses on their immuno/biocompatibility as well as physiochemical characteristics. The focus of this study is on the biocompatibility evaluations of a panel of four hydrogel scaffolds fabricated using alginate, chitosan and hydroxyapatite reinforced with poly(ethylene glycol). The hydrogels were subsequently cross-linked with calcium ions and glutaraldehyde. Immunocompatibility was assessed by interacting Raw 264.7 cell lines with these hydrogels. MTT cell viability assay revealed the non-cytotoxic nature of the hydrogels, and the macrophages grown in contact with the hydrogels exhibited no alteration in their morphology and were similar to the untreated normal cells. The concentration of nitric oxide, activity of myeloperoxidase and the messenger ribonucleic acid transcripts of proinflammatory cytokines, interleukin 6 and tumour necrosis factor alpha exhibited no considerable increase in the macrophages cultured with the hydrogels when compared to lipopolysaccharide-stimulated cells. In short, the absence of macrophage activation on contact with hydrogels is a clear indication of their in vitro immunocompatibility, suggesting their potential application as tissue engineering templates.

Effect of cellulose nanocrystals on scaffolds comprising chitosan, alginate and hydroxyapatite for bone tissue engineering

In this study, chitosan/alginate/hydroxyapatite/nanocrystalline cellulose scaffolds were successfully fabricated by the using of freeze-drying method, followed by dicationic crosslinking using CaCl₂. The chemical structure and morphology along with mechanical properties of the formed scaffolds respecting to various CNC contents were studied by Fourier-transform infrared spectroscopy (FTIR), X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM) and mechanical compression test. Chemical interaction and electrostatic attraction between chitosan (CS) and alginate with various CNC ratios were affirmed by FTIR spectroscopy. Results depicted that, scaffolds containing CNC exhibited remarkable improvement in both swelling ratio up to 110% compared without CNC (63%) and compressive strength when compared with other scaffolds. In addition, the average pore size increased, dramatically, with increasing of CNC up to 230 μm. Porosity was also obeyed the sequence and attainted a maximum value at 93.6%. The growth and cell attachment of fibroblast cells of the selected scaffold were examined prolonging to the cell viability by using Alamar Blue (AB) and then confirmed using SEM. The results indicated that the scaffold comprising CNC has a promising cell growth and cell adherence, and thus expected to have a potent possibility for applications in bone tissue culture.

Preparation, bioactivity and mechanism of nano-hydroxyapatite/sodium alginate/chitosan bone repair material

BACKGROUND

As the major inorganic component of natural bone, nano-hydroxyapatite (n-HA) on its own is limited in its use in bone repair, due to its brittleness. Chitosan (CS) and sodium alginate (SAL) are used to reduce its brittleness and tendency to degradation. However, the compressive strength of the composite is still low, and its biological performance needs further study.

METHODS

Nano-hydroxyapatite/sodium alginate/chitosan (n-HA/SAL/CS) composite was prepared via an in situ synthesis method. Further, we prepared the n-HA/SAL/CS self-setting bone repair material by mixing n-HA/SAL/CS powder with a curing liquid (20 wt.% citric acid). In addition, the in vitro bioactivity and cell cytotoxicity were also explored.

RESULTS

Transmission electron microscopy photos revealed that the n-HA crystals were uniformly distributed throughout the polymer matrix. Infrared IR spectroscopy indicated that the HA interacted with the COO^- of SAL and NH₂^- of CS. The compressive strength of the n-HA/SAL/CS bone cement was 34.3 MPa and matched the demands of weight-bearing bones. Soaking in vitro in simulated body fluid demonstrated that the composite material had reasonably good bioactivity, while cytotoxicity tests indicated that the n-HA/SAL/CS cement could promote cell proliferation and was biocompatible.

CONCLUSIONS

Compressive strength of n-HA/SAL/CS can satisfy the needs of cancellous bone, and in vitro bioactivity and cytotoxicity tests results indicated that the n-HA/SAL/CS composite could act as an optimal bone repair material.

Improvement of physico-chemical properties of dextran-chitosan composite scaffolds by addition of nano-hydroxyapatite

Nano-hydroxyapatite was incorporated into polymer matrix of Dextran/Chitosan to achieve a novel composite scaffold by freeze drying technique. The synthesized composite scaffolds were recognized by different performances such as: X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR) and Scanning electron microscope (SEM). The results revealed the complex formation between dextran and chitosan with an excellent dispersion of nHA inside the polymer matrix. The SEM images showed the presence of interconnected pore structure inside the scaffolds. The porosity of the composites was found to decrease from 82% to 67% by adding nanohydroxyapatite to the polymer matrix of Dextran/Chitosan. The mechanical properties of the scaffolds were measured by compression test. The obtained results verified that the presence of nHA can noticeably enhance young’s modulus and compressive strength of the composite scaffolds. All the obtained results essentially recommend that these composites can be a good candidate for bone tissue engineering applications.

Alginate/Hydroxyapatite-Based Nanocomposite Scaffolds for Bone Tissue Engineering Improve Dental Pulp Biomineralization and Differentiation

Tissue engineering is widely recognized as a promising approach for bone repair and reconstruction. Several attempts have been made to achieve materials that must be compatible, osteoconductive, and osteointegrative and have mechanical strength to provide a structural support. Composite scaffolds consisting in biodegradable natural polymers are very promising constructs. Hydroxyapatite (HAp) can support alginate as inorganic reinforcement and osteoconductive component of alginate/HAp composite scaffolds. Therefore, HAp-strengthened polymer biocomposites offer a solid system to engineer synthetic bone substitutes. In the present work, HAp was incorporated into an alginate solution and internal gelling was induced by addition of slowly acid-hydrolyzing D-gluconic acid delta-lactone for the direct release of calcium ions from HAp. It has been previously demonstrated that alginate-based composites efficiently support adhesion of cancer bone cell lines. Human dental pulp stem cells (DPSCs) identified in human dental pulp are clonogenic cells capable of differentiating in multiple lineage. Thus, this study is aimed at verifying the mineralization and differentiation potential of human DPSCs seeded onto scaffolds based on alginate and nano-hydroxyapatite. For this purpose, gene expression profile of early and late mineralization-related markers, extracellular matrix components, viability parameters, and oxidative stress occurrence were evaluated and analyzed. In summary, our data show that DPSCs express osteogenic differentiation-related markers and promote calcium deposition and biomineralization when growing onto Alg/HAp scaffolds. These findings confirm the use of Alg/HAp scaffolds as feasible composite materials in tissue engineering, being capable of promoting a specific and successful tissue regeneration as well as mineralized matrix deposition and sustaining natural bone regeneration.

Synthesis, characterization and in vitro screening of a nano-hydroxyapatite/chitosan/Euryale ferox nanoensemble – an inimitable approach for bone tissue engineering

In order to explore novel synthetic bone scaffolds, a biomimmetic, osteoinductive, tricomposite scaffold has been synthesized incorporating Euryale ferox (EF) with nano-hydroxyapatite and chitosan.

The effect of different hydroxyapatite microparticles on the osteogenic differentiation of MC3T3-E1 preosteoblasts

HA microparticles with different sizes and shapes played obvious different roles in promoting the osteogenic differentiation of MC3T3-E1 preosteoblasts. HA microspheres played a better role in promoting the osteogenic differentiation of MC3T3-E1 preosteoblasts than HA whiskers.