Biomimetic spiral-cylindrical scaffold based on hybrid chitosan/cellulose/nano-hydroxyapatite membrane for bone regeneration

Polysaccharide Hydroxyapatite (Nano)composites and Their Biomedical Applications: An Overview of Recent Years

Hydroxyapatite can combine with polysaccharide originating biomaterials with special applications in the biomedical field. In this review, the synthesis of (nano)composites is discussed, focusing on natural polysaccharides such as alginate, chitosan, and pectin. In this way, advances in recent years in the development of preparing materials are revised and discussed. Therefore, an overview of the recent synthesis and applications of polyssacharides@hydroxyapatites is presented. Several studies based on chitosan@hydroxyapatite combined with other inorganic matrices are highlighted, while pectin@hydroxyapatite is present in a smaller number of reports. Biomedical applications as drug carriers, adsorbents, and bone implants are discussed, combining their dependence with the nature of interactions on the molecular scale and the type of polysaccharides used, which is a relevant aspect to be explored.

Research trends of bio-application of major components in lignocellulosic biomass (cellulose, hemicellulose and lignin) in orthopedics fields based on the bibliometric analysis: A review

Cellulose, hemicellulose, and lignin are the major bio-components in lignocellulosic biomass (BC-LB), which possess excellent biomechanical properties and biocompatibility to satisfy the demands of orthopedic applications. To understand the basis and trends in the development of major bio-components in BC-LB in orthopedics, the bibliometric technology was applied to get unique insights based on the published papers (741) in the Web of Science (WOS) database from January 1st, 2001, to February 14th, 2023. The analysis includes the annual distributions of publications, keywords co-linearity, research hotspots exploration, author collaboration networks, published journals, and clustering of co-cited literature. The results reveal a steady growth in publications focusing on the application of BC-LB in orthopedics, with China and the United States leading in research output. The "International Journal of Biological Macromolecules" was identified as the most cited journal for BC-LB research in orthopedics. The research hotspots encompassed bone tissue engineering, cartilage tissue engineering, and drug delivery systems, indicating the fundamental research and potential development in these areas. This study also highlights the challenges associated with the clinical application of BC-LB in orthopedics and provides valuable insights for future advancements in the field.

Enhanced Proliferation and Differentiation of Human Osteoblasts by Remotely Controlled Magnetic-Field-Induced Electric Stimulation Using Flexible Substrates

With the progressive aging of the population, bone fractures are an increasing major health concern. Diverse strategies are being studied to reduce the recovery times using nonaggressive treatments. Electrical stimulation (either endogenous or externally applied electric pulses) has been found to be effective in accelerating bone cell proliferation and differentiation. However, the direct insertion of electrodes into tissues can cause undesirable inflammation or infection reactions. As an alternative, magnetoelectric heterostructures (wherein magnetic fields are applied to induce electric polarization) could be used to achieve electric stimulation without the need for implanted electrodes. Here, we develop a magnetoelectric platform based on flexible kapton/FeGa/P(VDF-TrFE) (flexible substrate/magnetostrictive layer/ferroelectric layer) heterostructures for remote magnetic-field-induced electric field stimulation of human osteoblast cells. We show that the use of flexible supports overcomes the clamping effects that typically occur when analogous magnetoelectric structures are grown onto rigid substrates (which preclude strain transfer from the magnetostrictive to the ferroelectric layers). The study of the diverse proliferation and differentiation markers evidence that in all the stages of bone formation (cell proliferation, extracellular matrix maturation, and mineralization), the electrical stimulation of the cells results in a remarkably better performance. The results pave the way for novel strategies for remote cell stimulation based on flexible platforms not only in bone regeneration but also in many other applications where electrical cell stimulation may be beneficial (e.g., neurological diseases or skin regeneration).

Fabrication and Evaluation of Porous dECM/PCL Scaffolds for Bone Tissue Engineering

Porous scaffolds play a crucial role in bone tissue regeneration and have been extensively investigated in this field. By incorporating a decellularized extracellular matrix (dECM) onto tissue-engineered scaffolds, bone regeneration can be enhanced by replicating the molecular complexity of native bone tissue. However, the exploration of porous scaffolds with anisotropic channels and the effects of dECM on these scaffolds for bone cells and mineral deposition remains limited. To address this gap, we developed a porous polycaprolactone (PCL) scaffold with anisotropic channels and functionalized it with dECM to capture the critical physicochemical properties of native bone tissue, promoting osteoblast cells' proliferation, differentiation, biomineralization, and osteogenesis. Our results demonstrated the successful fabrication of porous dECM/PCL scaffolds with multiple channel sizes for bone regeneration. The incorporation of 100 μm grid-based channels facilitated improved nutrient and oxygen infiltration, while the porous structure created using 30 mg/mL of sodium chloride significantly enhanced the cells' attachment and proliferation. Notably, the mechanical properties of the scaffolds closely resembled those of human bone tissue. Furthermore, compared with pure PCL scaffolds, the presence of dECM on the scaffolds substantially enhanced the proliferation and differentiation of bone marrow stem cells. Moreover, dECM significantly increased mineral deposition on the scaffold. Overall, the dECM/PCL scaffold holds significant potential as an alternative bone graft substitute for repairing bone injuries.

Cellulose-based composite scaffolds for bone tissue engineering and localized drug delivery

Natural bone constitutes a complex and organized structure of organic and inorganic components with limited ability to regenerate and restore injured tissues, especially in large bone defects. To improve the reconstruction of the damaged bones, tissue engineering has been introduced as a promising alternative approach to the conventional therapeutic methods including surgical interventions using allograft and autograft implants. Bioengineered composite scaffolds consisting of multifunctional biomaterials in combination with the cells and bioactive therapeutic agents have great promise for bone repair and regeneration. Cellulose and its derivatives are renewable and biodegradable natural polymers that have shown promising potential in bone tissue engineering applications. Cellulose-based scaffolds possess numerous advantages attributed to their excellent properties of non-toxicity, biocompatibility, biodegradability, availability through renewable resources, and the low cost of preparation and processing. Furthermore, cellulose and its derivatives have been extensively used for delivering growth factors and antibiotics directly to the site of the impaired bone tissue to promote tissue repair. This review focuses on the various classifications of cellulose-based composite scaffolds utilized in localized bone drug delivery systems and bone regeneration, including cellulose-organic composites, cellulose-inorganic composites, cellulose-organic/inorganic composites. We will also highlight the physicochemical, mechanical, and biological properties of the different cellulose-based scaffolds for bone tissue engineering applications.

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Cellulose and its derivatives are renewable and biodegradable natural polymers that with great potential for bone tissue engineering.

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Cellulose-based materials can be used various therapeutics directly to the bone to achieve bone regeneration.

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Bioinks made of cellulose-based materials hold great promise to develop patient specific solutions for bone repair using 3D printing.

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Challenges associated with inaccuracies in existing preclinical models, sterilization regulatory barriers still need to be addressed before clinical translation.

Improvement in osteogenesis, vascularization, and corrosion resistance of titanium with silicon-nitride doped micro-arc oxidation coatings

Titanium (Ti) implants have been widely used for the treatment of tooth loss due to their excellent biocompatibility and mechanical properties. However, modifying the biological properties of these implants to increase osteointegration remains a research challenge. Additionally, the continuous release of various metal ions in the oral microenvironment due to fluid corrosion can also lead to implant failure. Therefore, simultaneously improving the bioactivity and corrosion resistance of Ti-based materials is an urgent need. In recent decades, micro-arc oxidation (MAO) has been proposed as a surface modification technology to form a surface protective oxide layer and improve the comprehensive properties of Ti. The present study doped nano silicon nitride (Si₃N₄) particles into the Ti surface by MAO treatment to improve its corrosion resistance and provide excellent osteoinduction by enhancing alkaline phosphatase activity and osteogenic-related gene expression. In addition, due to the presence of silicon, the Si₃N₄-doped materials showed excellent angiogenesis properties, including the promotion of cell migration and tubule formation, which play essential roles in early recovery after implantation.

Active cell capturing for organ-on-a-chip systems: a review

Organ-on-a-chip (OOC) is an emerging technology that has been proposed as a new powerful cell-based tool to imitate the pathophysiological environment of human organs. For most OOC systems, a pivotal step is to culture cells in microfluidic devices. In active cell capturing techniques, external actuators, such as electrokinetic, magnetic, acoustic, and optical forces, or a combination of these forces, can be applied to trap cells after ejecting cell suspension into the microchannel inlet. This review paper distinguishes the characteristics of biomaterials and evaluates microfluidic technology. Besides, various types of OOC and their fabrication techniques are reported and various active cell capture microstructures are analyzed. Furthermore, their constraints, challenges, and future perspectives are provided.

In vitro and in vivo Repair Effects of the NCF-Col-NHA Aerogel Scaffold Loaded With SOST Monoclonal Antibody and SDF-1 in Steroid-Induced Osteonecrosis

In the current study, we synthesized nanocellulose (NCF)-collagen (Col)-nano hydroxyapatite (NHA) organic-inorganic hybrid aerogels loaded with stromal cell derived factor-1 (SDF-1) and sclerostin monoclonal antibody (SOST McAb) and investigated their ability to repair steroid-induced osteonecrosis. Rabbit bone marrow mesenchymal stem cells (BMSCs) and human vascular endothelial cells (HUVECs) were used for the in vitro study. A rabbit steroid-induced osteonecrosis model was used for the in vivo study. The best elastic modulus reached 12.95 ± 4.77 MPa with a mean compressive property of 0.4067 ± 0.084 MPa for the scaffold containing 100% mass fraction. The average pore diameter of the aerogel was 75 ± 18 µm with a porosity of more than 90% (96.4 ± 1.6%). The aerogel-loaded SDF-1 and SOST were released at 40–50% from the material within the initial 3 h and maintained a stable release for more than 21 days. The in vitro study showed osteogenesis and vascularization capabilities of the scaffold. The in vivo study showed that rabbits received implantation of the scaffold with SOST McAb and SDF-1 showed the best osteogenesis of the osteonecrosis zone in the femoral head. Imaging examination revealed that most of the necrotic area of the femoral head was repaired. These results suggest that this hybrid aerogel scaffold could be used for future steroid-induced osteonecrosis repair.

Emulsion templated scaffolds of poly(ε-caprolactone) - a review

The role of poly(ε-caprolactone) (PCL) and its 3D scaffolds in tissue engineering has already been established due to its ease of processing into long-term degradable implants and approval from the FDA. This review presents the role of high internal phase emulsion (HIPE) templating in the fabrication of PCL scaffolds, and the versatility of the technique along with challenges associated with it. Considering the huge potential of HIPE templating, which so far has mainly been focused on free radical polymerization of aqueous HIPEs, we provide a summary of how the technique has been expanded to non-aqueous HIPEs and other modes of polymerization such as ring-opening. The scope of coupling of HIPE templating with some of the advanced fabrication methods such as 3D printing or electrospinning is also explored.

Influence of Charge and Heat on the Mechanical Properties of Scaffolds from Ionic Complexation of Chitosan and Carboxymethyl Cellulose

As one of the most abundant, multifunctional biological polymers, polysaccharides are considered promising materials to prepare tissue engineering scaffolds. When properly designed, wetted porous scaffolds can have biomechanics similar to living tissue and provide suitable fluid transport, both of which are key features for in vitro and in vivo tissue growth. They can further mimic the components and function of glycosaminoglycans found in the extracellular matrix of tissues. In this study, we investigate scaffolds formed by charge complexation between anionic carboxymethyl cellulose and cationic protonated chitosan under well-controlled conditions. Freeze-drying and dehydrothermal heat treatment were then used to obtain porous materials with exceptional, unprecendent mechanical properties and dimensional long-term stability in cell growth media. We investigated how complexation conditions, charge ratio, and heat treatment significantly influence the resulting fluid uptake and biomechanics. Surprisingly, materials with high compressive strength, high elastic modulus, and significant shape recovery are obtained under certain conditions. We address this mostly to a balanced charge ratio and the formation of covalent amide bonds between the polymers without the use of additional cross-linkers. The scaffolds promoted clustered cell adhesion and showed no cytotoxic effects as assessed by cell viability assay and live/dead staining with human adipose tissue-derived mesenchymal stem cells. We suggest that similar scaffolds or biomaterials comprising other polysaccharides have a large potential for cartilage tissue engineering and that elucidating the reason for the observed peculiar biomechanics can stimulate further research.

Co-electrospun nano-/microfibrous composite scaffolds with structural and chemical gradients for bone tissue engineering

Recent trends in scaffold design for tissue engineering have focused on providing structural, mechanical and chemical cues for guiding cell behaviors. In this study, we presented a structural/compositional gradient nano-/microfibrous mesh by co-electrospinning, using silk fibroin-poly(ε-caprolactone) (SF-PCL) nanofibers and PCL microfibers. The pore size, porosity, and physical property of the gradient meshes were qualified. Cell proliferation of mouse osteoblast-like MC3T3-E1 cells was carried out to estimate the effect of structural and compositional gradients on biocompatibility. Furthermore, the 2-D mesh was rolled up and the compressive property of 3-D cylinder was investigated. The results suggested that the rolled-up gradient cylinder scaffold exhibited higher osteogenic differentiation compared to the pristine nanofibrous cylinder sample. By incorporating Chinese medicine ginsenoside Rg1, sustained release was achieved in composite meshes. Rg1-containing nanofibrous meshes and Rg1 gradient cylinders enhanced the cell proliferation of human umbilical vein endothelial cells (HUVECs). The developed fibrous scaffold may provide structural, compositional, and chemical gradients for bone regeneration. BRIEFS: Structural and chemical gradient fibrous scaffold fabricated by co-electrospinning.

Biomimetic cues from poly(lactic-co-glycolic acid)/hydroxyapatite nano-fibrous scaffolds drive osteogenic commitment in human mesenchymal stem cells in the absence of osteogenic factor supplements

Mimicking the complex hierarchical architecture of the 'osteon', the functional unit of cortical bone, from the bottom-up offers the possibility of generating mature bone tissue in tissue engineered bone substitutes. In this work, a modular 'bottom-up' approach has been developed to assemble bone niche-mimicking nanocomposite scaffolds composed of aligned electrospun nanofibers of poly(lactic-co-glycolic acid) (PLGA) encapsulating aligned rod-shape nano-sized hydroxyapatite (nHA). By encoding axial orientation of the nHA within these aligned nanocomposite fibers, significant improvements in mechanical properties, surface roughness, hydrophilicity and in vitro simulated body fluid (SBF) mineral deposition were achieved. Moreover, these hierarchical scaffolds induced robust formation of bone hydroxyapatite and osteoblastic maturation of human bone marrow-derived mesenchymal stem cells (hBMSCs) in growth media that was absent of any soluble osteogenic differentiation factors. The results of this investigation confirm that these tailored, aligned nanocomposite fibers, in the absence of media-bone inductive factors, offer the requisite biophysical and biochemical cues to hBMSCs to promote and support their differentiation into mature osteoblast cells and form early bone-like tissue in vitro.

Biomimetic periosteum-bone substitute composed of preosteoblast-derived matrix and hydrogel for large segmental bone defect repair

Repairing large segmental bone defects above a critical size remains challenging with high risk of delayed union or even non-union. From the perspective of bone development and clinical experience, periosteum plays an indispensable role in bone repair and reconstruction. In this study, we explored the feasibility of using preosteoblast-derived matrix (pODM) as a biomimetic periosteum. By culturing MC3T3-E1 cell sheet on poly(dimethylsiloxane) and performing decellularization, an integral cell-free sheet of pODM could be readily harvested. Bone marrow mesenchymal stem cells (BMSCs) adhered and proliferated well on pODM. In addition, pODM exhibited a chemotactic effect on BMSCs in a concentration-dependent manner and also promoted osteogenic differentiation of BMSCs. Following that, pODM was wrapped around a gelatin methacryloyl (GelMA) hydrogel to construct an engineered periosteum-bone substitute. A rabbit radius segmental bone defect model was used to examine the bone repair efficacy of pODM/GelMA. Upon implantation of pODM/GelMA construct for 12 weeks, the critical-sized bone defects completely healed with remarkable full reconstruction of medullary cavity at the radial diaphysis. Together, this work proposes a high potency of using precursor cell-derived matrix as a biomimetic periosteum, which preserves the beneficial biological factors while avoids the limitations of using exogenous cells for bone regeneration. Combining precursor cell-derived matrix with hydrogel may provide a promising periosteum-bone biomimetic substitute for bone repair. STATEMENT OF SIGNIFICANCE: Repairing large segmental bone defects above a critical size remains challenging. As the periosteum plays an essential role in bone repair, this study aimed to explore the use of preosteoblast-derived matrix (pODM), harvested from decellularized MC3T3-E1 cell sheet, as a biomimetic periosteum to facilitate bone repair. We found that in vitro, pODM exhibited considerable chemotactic effect and osteogenic induction capability to bone marrow mesenchymal stem cells (BMSCs). In vivo, implantation of pODM/gelatin methacryloyl (GelMA) constructs as engineered periosteum-bone substitutes effectively repaired the critical-sized segmental bone defects at rabbit radius. Surprisingly, remarkable full reconstruction of medullary cavity at the diaphysis was achieved. Therefore, combining pODM with hydrogel may provide a promising biomimetic substitute for bone repair.

Microfabrication of a biomimetic arcade-like electrospun scaffold for cartilage tissue engineering applications

In recent years, the engineering of biomimetic cellular microenvironments has emerged as a top priority for regenerative medicine, being the in vitro recreation of the arcade-like cartilaginous tissue one of the most critical challenges due to the notorious absence of cost- and time-efficient microfabrication techniques capable of building 3D fibrous scaffolds with precise anisotropic properties. Taking this into account, we suggest a feasible and accurate methodology that uses a sequential adaptation of an electrospinning-electrospraying set up to construct a hierarchical system comprising both polycaprolactone (PCL) fibres and polyethylene glycol sacrificial microparticles. After porogen leaching, the bi-layered PCL scaffold was capable of presenting not only a depth-dependent fibre orientation similar to natural cartilage, but also mechanical features and porosity proficient to encourage an enhanced cell response. In fact, cell viability studies confirmed the biocompatibility of the scaffold and its ability to guarantee suitable cell adhesion, proliferation and migration throughout the 3D anisotropic fibrous network during 21 days of culture. Additionally, likewise the hierarchical relationship between chondrocytes and their extracellular matrix, the reported PCL scaffold was able to induce depth-dependent cell-material interactions responsible for promoting a spatial modulation of the morphology, alignment and density of the cells in vitro.

Injectable thermosensitive hybrid hydrogel containing graphene oxide and chitosan as dental pulp stem cells scaffold for bone tissue engineering

Here, we fabricated thermosensitive injectable hydrogel containing poly (N-isopropylacrylamide) (PNIPAAm)-based copolymer/graphene oxide (GO) composite with different feed ratio to chitosan (CS) as a natural polymer through physical and chemical crosslinking for the proliferation and differentiation of the human dental pulp stem cells (hDPSCs) to the osteoblasts. The PNIPAAm copolymer/GO composite was synthesized by free-radical copolymerization of (N-isopropylacrylamide) (NIPAAm), itaconic acid (IA) and maleic anhydride-modified poly(ethylene glycol) (PEG) in the presence of GO and used for the preparation of the hydrogels. The formulated hydrogels were evaluated for the porous architecture, rheological behavior, compressive strength, swelling property, in vitro degradation, hemocompatibility, biocompatibility, and differentiation. The hydrogel could enhance the deposition of minerals and the activity of alkaline phosphatase (ALP), in large part attributable to the oxygen and amine-containing functional groups of GO and CS. The engineered hydrogel could also upregulate the expression of the Runt-related transcription factor 2 and osteocalcin in the hDPSCs cultivated in both the normal and osteogenic media. It seems to promote the absorption of osteogenic inducer too. Based on our findings, the engineered hydrogel demonstrated the osteogenic potential, upon which it is proposed as a constructing scaffold in bone tissue engineering for the transplantation of hDPSCs.

Recent Advances in Applications of Cellulose Derivatives-Based Composite Membranes with Hydroxyapatite

The development of novel polymeric composites based on cellulose derivatives and hydroxyapatite represents a fascinating and challenging research topic in membranes science and technology. Cellulose-based materials are a viable alternative to synthetic polymers due to their favorable physico-chemical and biological characteristics. They are also an appropriate organic matrix for the incorporation of hydroxyapatite particles, inter and intramolecular hydrogen bonds, as well as electrostatic interactions being formed between the functional groups on the polymeric chains surface and the inorganic filler. The current review presents an overview on the main application fields of cellulose derivatives/hydroxyapatite composite membranes. Considering the versatility of hydroxyapatite particles, the hybrid materials offer favorable prospects for applications in water purification, tissue engineering, drug delivery, and hemodialysis. The preparation technique and the chemical composition have a big influence on the final membrane properties. The well-established membrane fabrication methods such as phase inversion, electrospinning, or gradual electrostatic assembly are discussed, together with the various strategies employed to obtain a homogenous dispersion of the inorganic particles in the polymeric matrix. Finally, the main conclusions and the future directions regarding the preparation and applications of cellulose derivatives/hydroxyapatite composite membranes are presented.

Three-Dimensional High-Porosity Chitosan/Honeycomb Porous Carbon/Hydroxyapatite Scaffold with Enhanced Osteoinductivity for Bone Regeneration

Three-dimensional honeycomb porous carbon (HPC) has attracted increasing attention in bioengineering due to excellent mechanical properties and a high surface-to-volume ratio. In this paper, a three-dimensional chitosan (CS)/honeycomb porous carbon/hydroxyapatite composite was prepared by nano-sized hydroxyapatite (nHA) on the HPC surface in situ deposition, dissolved in chitosan solution, and vacuum freeze-dried. The structure and composition of CS/HPC/nHA were characterized by scanning electron microscopy, transmission electron miscroscopy, Fourier transform infrared, and X-ray photoelectron spectroscopy, and the porosity, swelling ratio, and mechanical properties of the scaffold were also tested. The as-prepared scaffolds possess hierarchical pores and organic-inorganic components, which are similar in composition and structure to bone tissues. The synthesized composite scaffold has high porosity and a certain mechanical strength. By culturing mouse bone marrow mesenchymal stem cells on the surface of the scaffold, it was confirmed that the scaffold facilitated its growth and promoted its differentiation into the osteogenesis direction. In vivo experiments further demonstrate that the CS/HPC/nHA composite scaffold has a significant advantage in promoting bone formation in the bone defect area. All the results suggested that the CS/HPC/nHA scaffolds have great application prospect in bone tissue engineering.

Cylindrical Layered Bone Scaffolds with Anisotropic Mechanical Properties as Potential Drug Delivery Systems

3D cylindrical layered scaffolds with anisotropic mechanical properties were prepared according to a new and simple method, which involves gelatin foaming, deposition of foamed strips, in situ crosslinking, strip rolling and lyophilization. Different genipin concentrations were tested in order to obtain strips with different crosslinking degrees and a tunable stability in biological environment. Before lyophilization, the strips were curled in a concentric structure to generate anisotropic spiral-cylindrical scaffolds. The scaffolds displayed significantly higher values of stress at break and of the Young modulus in compression along the longitudinal than the transverse direction. Further improvement of the mechanical properties was achieved by adding strontium-substituted hydroxyapatite (Sr-HA) to the scaffold composition and by increasing genipin concentration. Moreover, composition modulated also water uptake ability and degradation behavior. The scaffolds showed a sustained strontium release, suggesting possible applications for the local treatment of abnormally high bone resorption. This study demonstrates that assembly of layers of different composition can be used as a tool to obtain scaffolds with modulated properties, which can be loaded with drugs or biologically active molecules providing properties tailored upon the needs.

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.

Microporous Coatings of PEKK/SN Composites Integration with PEKK Exhibiting Antibacterial and Osteogenic Activity, and Promotion of Osseointegration for Bone Substitutes

To improve the antibacterial and osteogenic activities of poly(etherketoneketone) (PEKK), concentrated sulfuric acid (H₂SO₄) suspension with silicon nitride (SN) microparticle was utilized to modify PEKK surface. Through sulfonation reaction, microporous coatings of PEKK/SN composites were created on PEKK surface, which were integrated with PEKK substrate. The results showed that the content of SN in the microporous coatings increased with the increase of SN content in H₂SO₄ suspension (PKS without SN, PKSC5 and PKSC10 with 5 and 10 wt % SN content in H₂SO₄) and that the surface roughness and hydrophilicity of microporous coatings on PEKK were significantly improved with the SN content increasing. In addition, the microporous coating of PKSC10 with high SN content exhibited excellent antibacterial activity due to the synergistic action of the presence of amino (-NH₂) and sulfonic acid (-SO₃H) groups as well as the improvement of protein absorption. Moreover, the microporous coating of PKSC10 obviously stimulated adhesion, proliferation, and osteogenic differentiation of rat bone mesenchymal stem cells. Furthermore, histological and push-out load evaluation indicated that the microporous coating of PKSC10 significantly promoted osteogenesis and osseointegration in vivo. The results suggested that the microporous coating of PKSC10 with high SN content display good biocompatibility, antibacterial and osteogenic activities, and osseointegration ability, which would have great potential for bone substitutes.

Biomimetic composite scaffold from an in situ hydroxyapatite coating on cellulose nanocrystals

A novel nanocomposite scaffold was developed by homogeneous deposition of hydroxyapatite (HAP) on a cellulose nanocrystals (CNCs) matrix suspended in a simulated body fluid (SBF). By adjusting the pH of the SBF, the HAP content in the nanocomposite could be controlled between 15 wt% and 47 wt%. Physical and chemical characteristics of the nanocomposites were analyzed by SEM, FTIR, XRD, SAED, and TEM, which confirmed the successful incorporation of HAP onto the CNCs. The nanocomposites were then freeze-casted into porous scaffolds by different solidification technologies (i.e., directional freezing (DF), plunging in liquid N₂ (PL) or in a −20 °C freezer (FZ)) followed by lyophilization. Compression testing of the HAP/CNCs foams indicated that DF caused significant improvement in mechanical properties due to the specific orientation and anisotropic porous structure compared to conventional freezing methods such as PL and FZ. Moreover, the scaffold with high HAP content exhibited improved mechanical and thermal properties, which holds potential for application in bone tissue engineering.

A novel nanocomposite scaffold was developed by homogeneous deposition of hydroxyapatite (HAP) on a cellulose nanocrystal (CNCs) matrix suspended in a simulated body fluid (SBF).

Chemical Self-Assembly of Multifunctional Hydroxyapatite with a Coral-like Nanostructure for Osteoporotic Bone Reconstruction

Bone defects/fractures are common in older people suffering from osteoporosis. Traditional hydroxyapatite (HA) materials for osteoporotic bone repair face many challenges, including limited bone formation and aseptic loosening of orthopedic implants. In this study, a new multifunctional HA is synthesized by spontaneous assembly of alendronate (AL) and Fe₃O₄ onto HA nanocrystals for osteoporotic bone regeneration. The chemical coordination of AL and Fe₃O₄ with HA does not induce lattice deformation, resulting in a functionalized HA (Func-HA) with proper magnetic property and controlled release manner. The Func-HA nanocrystals have been encapsulated in polymer substrates to further investigate their osteogenic capability. In vitro and in vivo evaluations reveal that both AL and Fe₃O₄, especially the combination of two functional groups on HA, can inhibit osteoclastic activity and promote osteoblast proliferation and differentiation, as well as enhance implant osseointegration and accelerate bone remodeling under osteoporotic condition. The as-developed Func-HA with coordinating antiresorptive ability, magnetic property, and osteoconductivity might be a desirable biomaterial for osteoporotic bone defect/fracture treatment.

Hydroxyapatite nanowire/collagen elastic porous nanocomposite and its enhanced performance in bone defect repair

The synthetic bone grafts that mimic the composition and structure of human natural bone exhibit great potential for application in bone defect repair. In this study, a biomimetic porous nanocomposite consisting of ultralong hydroxyapatite nanowires (UHANWs) and collagen (Col) with 66.7 wt% UHANWs has been prepared by the freeze drying process and subsequent chemical crosslinking. Compared with the pure collagen as a control sample, the biomimetic UHANWs/Col porous nanocomposite exhibits significantly improved mechanical properties. More significantly, the rehydrated UHANWs/Col nanocomposite exhibits an excellent elastic behavior. Moreover, the biomimetic UHANWs/Col porous nanocomposite has a good degradable performance with a sustained release of Ca and P elements, and can promote the adhesion and spreading of mesenchymal stem cells. The in vivo evaluation reveals that the biomimetic UHANWs/Col porous nanocomposite can significantly enhance bone regeneration compared with the pure collagen sample. After 12 weeks implantation, the woven bone and lamellar bone are formed throughout the entire UHANWs/Col porous nanocomposite, and connect directly with the host bone to construct a relatively normal bone marrow cavity, leading to successful osteointegration and bone reconstruction. The as-prepared biomimetic UHANWs/Col porous nanocomposite is promising for applications in various fields such as bone defect repair.

Decellularized Periosteum-Covered Chitosan Globule Composite for Bone Regeneration in Rabbit Femur Condyle Bone Defects

Critical-sized bone defects are incapable of self-healing and are commonly seen in clinical practice. The authors explore a new treatment for this, decellularized periosteum is applied to chitosan globules (chitosan-DP globules) as a hybrid material. The efficacy of chitosan-DP globules on rabbit femoral condyle bone defects is assessed with biocompatibility, biomechanics, and osteogenic efficiency measurements, and compared with the results of chitosan globules and empty control. No difference in cytotoxicity is observed among chitosan-DP globules, chitosan globules, and the empty control. Chitosan-DP globules possesse a better surface for cell adhesion than did chitosan globules. Chitosan-DP globules demonstrate superior efficiency for osteogenesis in the defect area compared to chitosan globules as per microcomputed tomography examination and push-out testing, with relatively minor histological differences. Both chitosan globule groups show more satisfactory results than those for the empty control. The results implicate chitosan-DP globules as a promising solution for bone defects.

Reconstruction of Craniomaxillofacial Bone Defects Using Tissue-Engineering Strategies with Injectable and Non-Injectable Scaffolds

Engineering craniofacial bone tissues is challenging due to their complex structures. Current standard autografts and allografts have many drawbacks for craniofacial bone tissue reconstruction; including donor site morbidity and the ability to reinstate the aesthetic characteristics of the host tissue. To overcome these problems; tissue engineering and regenerative medicine strategies have been developed as a potential way to reconstruct damaged bone tissue. Different types of new biomaterials; including natural polymers; synthetic polymers and bioceramics; have emerged to treat these damaged craniofacial bone tissues in the form of injectable and non-injectable scaffolds; which are examined in this review. Injectable scaffolds can be considered a better approach to craniofacial tissue engineering as they can be inserted with minimally invasive surgery; thus protecting the aesthetic characteristics. In this review; we also focus on recent research innovations with different types of stem-cell sources harvested from oral tissue and growth factors used to develop craniofacial bone tissue-engineering strategies.

Resol based chitosan/nano-hydroxyapatite nanoensemble for effective bone tissue engineering

It is the first report where different amounts of resol resin (RS) were incorporated with chitosan-hydroxyapatite (CHA) to develop a triconstituent nanoensemble CHA-RS(0.5,1,2), via simple co-precipitation method. The results of SEM, TEM, TGA and mechanical analysis revealed irregular interconnected rough morphology with homogenous distribution of needle shaped particles having average size ranging between 12 and 19nm, possessing higher thermal stability and mechanical strength, respectively relative to CHA (binary) nanocomposite. The CHA-1RS nanocomposite showed enhanced protein adsorption and ALP activity with excellent apatite formation ability compared to CHA-RS(0.5,2) and CHA nanocomposites. Thus, CHA-1RS nanocomposite was selectively tested as bare implant in the repair of critical-size calvarium defect (8mm) in albino rat. The histopathological and radiological investigations indicated that CHA-1RS prompted the bone regeneration ability as early as 2 weeks postimplantation demonstrating remarkably faster healing of calvarial defect relative to Cerabone. These findings have placed CHA-1RS on the pedestal to be employed as a potential alternative biomaterial for bone tissue engineering.

MgAl layered double hydroxide/chitosan porous scaffolds loaded with PFTα to promote bone regeneration

Poor bone formation remains a key risk factor associated with acellular scaffolds that occurs in some bone defects, particularly in patients with metabolic bone disorders and local osteoporosis. We herein fabricated for the first time layered double hydroxide-chitosan porous scaffolds loaded with PFTα (LDH-CS-PFTα scaffolds) as therapeutic bone scaffolds for the controlled release of PFTα to enhance stem cell osteogenic differentiation and bone regeneration. The LDH-CS scaffolds had three-dimensional interconnected macropores, and plate-like LDH nanoparticles were uniformly dispersed within or on the CS films. The LDH-CS scaffolds exhibited appropriate PFTα drug delivery due to hydrogen bonding among LDH, CS and PFTα. In vitro functional studies demonstrated that the PFTα molecules exhibited potent ability to induce osteogenesis of hBMSCs via the GSK3β/β-catenin pathway, and the LDH-CS-PFTα scaffolds significantly enhanced the osteogenic differentiation of hBMSCs. In vivo studies revealed significantly increased repair and regeneration of bone tissue in cranial defect model rats compared to control rats at 12 weeks post-implantation. In conclusion, the LDH-CS-PFTα scaffolds exhibited excellent osteogenic differentiation and bone regeneration capability and hold great potential for applications in defined local bone regeneration.

Hydroxyapatite Nanowire@Magnesium Silicate Core-Shell Hierarchical Nanocomposite: Synthesis and Application in Bone Regeneration

Multifunctional biomaterials that simultaneously combine high biocompatibility, biodegradability, and bioactivity are promising for applications in various biomedical fields such as bone defect repair and drug delivery. Herein, the synthesis of hydroxyapatite nanowire@magnesium silicate nanosheets (HANW@MS) core-shell porous hierarchical nanocomposites (nanobrushes) is reported. The morphology of the magnesium silicate (MS) shell can be controlled by simply varying the solvothermal temperature and the amount of Mg²⁺ ions. Compared with hydroxyapatite nanowires (HANWs), the HANW@MS core-shell porous hierarchical nanobrushes exhibit remarkably increased specific surface area and pore volume, endowing the HANW@MS core-shell porous hierarchical nanobrushes with high-performance drug loading and sustained release. Moreover, the porous scaffold of HANW@MS/chitosan (HANW@MS/CS) is prepared by incorporating the HANW@MS core-shell porous hierarchical nanobrushes into the chitosan (CS) matrix. The HANW@MS/CS porous scaffold not only promotes the attachment and growth of rat bone marrow derived mesenchymal stem cells (rBMSCs), but also induces the expression of osteogenic differentiation related genes and the vascular endothelial growth factor (VEGF) gene of rBMSCs. Furthermore, the HANW@MS/CS porous scaffold can obviously stimulate in vivo bone regeneration, owing to its high bioactive performance on the osteogenic differentiation of rBMSCs and in vivo angiogenesis. Since Ca, Mg, Si, and P elements are essential in human bone tissue, HANW@MS core-shell porous hierarchical nanobrushes with multifunctional properties are expected to be promising for various biomedical applications such as bone defect repair and drug delivery.

Graphene oxide as an interface phase between polyetheretherketone and hydroxyapatite for tissue engineering scaffolds

The poor bonding strength between biopolymer and bioceramic has remained an unsolved issue. In this study, graphene oxide (GO) was introduced as an interface phase to improve the interfacial bonding between polyetheretherketone (PEEK) and hydroxyapatite (HAP) for tissue engineering scaffolds. On the one hand, the conjugated structure of GO could form strong π-π stacking interaction with the benzene rings in PEEK. On the other hand, GO with a negatively charge resulting from oxygen functional groups could adsorb the positively charged calcium atoms (C sites) of HAP. Consequently, the dispersibility and compatibility of HAP in the PEEK matrix increased with increasing GO content up to 1 wt%. At this time, the compressive strength and modulus of scaffolds increased by 79.45% and 42.07%, respectively. Furthermore, the PEEK-HAP with GO (PEEK-HAP/GO) scaffolds possessed the ability to induce formation of bone-like apatite. And they could support cellular adhesion, proliferation as well as osteogenic differentiation. More importantly, in vivo bone defect repair experiments showed that new bone formed throughout the scaffolds at 60 days after implantation. All these results suggested that the PEEK-HAP/GO scaffolds have a promising potential for bone tissue engineering application.

Versatility of Chitosan-Based Biomaterials and Their Use as Scaffolds for Tissue Regeneration

Chitosan is a naturally occurring polysaccharide obtained from chitin, present in abundance in the exoskeletons of crustaceans and insects. It has aroused great interest as a biomaterial for tissue engineering on account of its biocompatibility and biodegradation and its affinity for biomolecules. A significant number of research groups have investigated the application of chitosan as scaffolds for tissue regeneration. However, there is a wide variability in terms of physicochemical characteristics of chitosan used in some studies and its combinations with other biomaterials, making it difficult to compare results and standardize its properties. The current systematic review of literature on the use of chitosan for tissue regeneration consisted of a study of 478 articles in the PubMed database, which resulted, after applying inclusion criteria, in the selection of 61 catalogued, critically analysed works. The results demonstrated the effectiveness of chitosan-based biomaterials in 93.4% of the studies reviewed, whether or not combined with cells and growth factors, in the regeneration of various types of tissues in animals. However, the absence of clinical studies in humans, the inadequate experimental designs, and the lack of information concerning chitosan's characteristics limit the reproducibility and relevance of studies and the clinical applicability of chitosan.

Recent advances in nano scaffolds for bone repair

Biomedical applications of nanomaterials are exponentially increasing every year due to analogy to various cell receptors, ligands, structural proteins, and genetic materials (that is, DNA). In bone tissue, nanoscale materials can provide scaffold for excellent tissue repair via mechanical stimulation, releasing of various loaded drugs and mediators, 3D scaffold for cell growth and differentiation of bone marrow stem cells to osteocytes. This review will therefore highlight recent advancements on tissue and nanoscale materials interaction.

In vitro and in vivo study of microporous ceramics using MC3T3 cells, CAM assay and a pig animal model

Bone tissue engineering combines biomaterials with biologically active factors and cells to hold promise for reconstructing craniofacial defects. In this study the biological activity of biphasic hydroxyapatite ceramics (HA; a bone substitute that is a mixture of hydroxyapatite and β-tricalcium phosphate in fixed ratios) was characterized (1) in vitro by assessing the growth of MC3T3 mouse osteoblast lineage cells, (2) in ovo by using the chick chorioallantoic membrane (CAM) assay and (3) in an in vivo pig animal model. Biocompatibility, bioactivity, bone formation and biomaterial degradation were detected microscopically and by radiology and histology. HA ceramics alone demonstrated great biocompatibility on the CAM as well as bioactivity by increased proliferation and alkaline phosphatase secretion of mouse osteoblasts. The in vivo implantation of HA ceramics with bone marrow mesenchymal stem cells (MMSCs) showed de novo intramembranous bone healing of critical-size bone defects in the right lateral side of pig mandibular bodies after 3 and 9 weeks post-implantation. Compared with the HA ceramics without MMSCs, the progress of bone formation was slower with less-developed features. This article highlights the clinical use of microporous biphasic HA ceramics despite the unusually shaped elongated micropores with a high length/width aspect ratio (up to 20) and absence of preferable macropores (>100 µm) in bone regenerative medicine.