Synthesis and evaluation of collagen-chitosan-hydroxyapatite nanocomposites for bone grafting

Chitosan-collagen-hydroxyapatite membranes for tissue engineering

Tissue engineering is growing in developing new technologies focused on providing effective solutions to degenerative pathologies that affect different types of connective tissues. The search for biocompatible, bioactive, biodegradable, and multifunctional materials has grown significantly in recent years. Chitosan, calcium phosphates collagen, and their combination as composite materials fulfill the required properties and could result in biostimulation for tissue regeneration. In the present work, the chitosan/collagen/hydroxyapatite membranes were prepared with different concentrations of collagen and hydroxyapatite. Cell adhesion was evaluated by MTS assay for two in vitro models. Additionally, cytotoxicity of the different membranes employing hemolysis of erythrocytes isolated from human blood was carried out. The structure of the membranes was analyzed by X-rays diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and thermal stability properties by thermogravimetric methods (TGA). The highest cell adhesion after 48 h was obtained for chitosan membranes with the highest hydroxyapatite and collagen content. All composite membranes showed good cell adhesion and low cytotoxicity, suggesting that these materials have a significant potential to be used as biomaterials for tissue engineering. Graphical abstract.

Highly Segregated Biocomposite Membrane as a Functionally Graded Template for Periodontal Tissue Regeneration

Guided tissue regeneration (GTR) membranes are used for treating chronic periodontal lesions with the aim of regenerating lost periodontal attachment. Spatially designed functionally graded bioactive membranes with surface core layers have been proposed as the next generation of GTR membranes. Composite formulations of biopolymer and bioceramic have the potential to meet these criteria. Chitosan has emerged as a well-known biopolymer for use in tissue engineering applications due to its properties of degradation, cytotoxicity and antimicrobial nature. Hydroxyapatite is an essential component of the mineral phase of bone. This study developed a GTR membrane with an ideal chitosan to hydroxyapatite ratio with adequate molecular weight. Membranes were fabricated using solvent casting with low and medium molecular weights of chitosan. They were rigorously characterised with scanning electron microscopy, Fourier transform infrared spectroscopy in conjunction with photoacoustic sampling accessory (FTIR-PAS), swelling ratio, degradation profile, mechanical tensile testing and cytotoxicity using human osteosarcoma and mesenchymal progenitor cells. Scanning electron microscopy showed two different features with 70% HA at the bottom surface packed tightly together, with high distinction of CH from HA. FTIR showed distinct chitosan dominance on top and hydroxyapatite on the bottom surface. Membranes with medium molecular weight showed higher swelling and longer degradation profile as compared to low molecular weight. Cytotoxicity results indicated that the low molecular weight membrane with 30% chitosan and 70% hydroxyapatite showed higher viability with time. Results suggest that this highly segregated bilayer membrane shows promising potential to be adapted as a surface layer whilst constructing a functionally graded GTR membrane on its own and for other biomedical applications.

Hidrogeles de colágeno acoplados con hidroxiapatita para aplicaciones en ingeniería tisular

Los hidrogeles basados en colágeno son redes tridimensionales (3D) con la capacidad de absorber agua y una alta biocompatibilidad para utilizarlos en la reparación de tejidos dañados. Estos materiales presentan pobres propiedades mecánicas y velocidades de degradación rápidas, limitando su aplicación a estrategias de ingeniería tisular y biomedicina; por ésto, la incorporación de fases inorgánicas en la matriz 3D del colágeno como la hidroxiapatita ha contribuido en la mejora de sus propiedades, incrementado la eficiencia de los hidrogeles híbridos obtenidos. Este trabajo, presenta las contribuciones más relevantes relacionadas con los sistemas de hidrogeles basados en colágeno y partículas de hidroxiapatita dispersas dentro de la matriz colagénica, lo que evidencia que la combinación de los materiales no altera la biocompatibilidad y biodegradabilidad típicas del colágeno, permitiendo la adhesión, proliferación, crecimiento celular y control del metabolismo de las células implicadas en los procesos de una reparación ósea, presentando a los hidrogeles como una estrategia para su uso potencial en la ingeniería tisular.

Bioenergetic-active materials enhance tissue regeneration by modulating cellular metabolic state

Cellular bioenergetics (CBE) plays a critical role in tissue regeneration. Physiologically, an enhanced metabolic state facilitates anabolic biosynthesis and mitosis to accelerate regeneration. However, the development of approaches to reprogram CBE, toward the treatment of substantial tissue injuries, has been limited thus far. Here, we show that induced repair in a rabbit model of weight-bearing bone defects is greatly enhanced using a bioenergetic-active material (BAM) scaffold compared to commercialized poly(lactic acid) and calcium phosphate ceramic scaffolds. This material was composed of energy-active units that can be released in a sustained degradation-mediated fashion once implanted. By establishing an intramitochondrial metabolic bypass, the internalized energy-active units significantly elevate mitochondrial membrane potential (ΔΨm) to supply increased bioenergetic levels and accelerate bone formation. The ready-to-use material developed here represents a highly efficient and easy-to-implement therapeutic approach toward tissue regeneration, with promise for bench-to-bedside translation.

Thermal and mechanical behavior of ultra-high molecular weight polyethylene/collagen blends

Bone defects or diseases significantly affect quality of life, thus the development of materials with improved performance that can be used as bone substitutes is increasingly studied. As an alternative, ultra-high molecular weight polyethylene (UHMWPE) has been employed for orthopedic applications since it combines high wear resistance, high impact resistance and low friction coefficient. However, it is a bioinert material and difficult to process. In the present work, the addition of collagen (hydrolyzed or type II), one of the constituents of natural bone, to UHMWPE was studied aiming to improve its processability and possibly its biocompatibility. The blends were prepared by compression and twin-screw extrusion. The results show that addition of higher amounts of both collagens to UHMWPE reduced the degree of crystallinity. However, crystallization and melting temperatures were not affected. The thermogravimetric analysis exhibited two thermal events correlated to the degradation of collagens (Tmax~300 °C) and of UHMWPE (Tmax~480 °C), corroborating the FTIR analysis that presented bands corresponding to these materials. The extrusion process promoted a better dispersion of the collagens, especially the hydrolyzed one. In addition, the obtained materials presented better mechanical properties when extruded. Torque reduction during extrusion showed that hydrolyzed collagen aid processing, even more than collagen due to its smaller molecular weight.

Hydroxyapatite/sericin composites: A simple synthesis route under near-physiological conditions of temperature and pH and preliminary study of the effect of sericin on the biomineralization process

Synthesis of hydroxyapatite (HAp) and sericin (SS) nanocomposites was carried out by a simple precipitation method performed in batch in a stirred tank reactor (ST). The reaction was achieved by mixing a solution of calcium chloride dihydrate, in which SS was dissolved, with a solution of disodium hydrogen phosphate at 37 °C. Three experimental conditions were studied by varying the concentration of SS: HAp, HAp/SS1 (0.01 g/L of SS) and HAp/SS2 (1 g/L of SS). The chemical and physical properties of the resulting HAp/SS nanocomposites were studied using several techniques (Atomic Absorption Spectrometry, Ultraviolet-Visible Spectrophotometry, Fourier Transform Infrared Spectroscopy (FTIR), X-ray diffraction (XRD), Scanning electron microscopy (SEM), Transmission electron microscopy (TEM), Selected area diffraction (SAED) and Thermogravimetric analysis (TGA)). pH profile was also monitored over time for each experimental condition. The results revealed that nano single-phased HAp was formed with both rod and plate-like shape. Additionally, the particles have low crystallinity, characteristic similar to biological HAp. Regarding the influence of SS, one observed that with increasing SS concentration there is an increase in the mean particle size and the number of plate-like particles, as well as an increase in the aggregation degree and a decrease of the crystallinity. Further, the composites obtained have an inorganic/organic composition comparable to bone. Finally, in vitro cytotoxicity showed that the synthetized nanoparticles are non-toxic and cell viability is higher for HAp and HAp/SS samples when compared to a commercially available HAp. The produced materials can thus be considered suitable candidates for bone related applications.

A Composite Chitosan-Reinforced Scaffold Fails to Provide Osteochondral Regeneration

Several biomaterials have recently been developed to address the challenge of osteochondral regeneration. Among these, chitosan holds promises both for cartilage and bone healing. The aim of this in vivo study was to evaluate the regeneration potential of a novel hybrid magnesium-doped hydroxyapatite (MgHA), collagen, chitosan-based scaffold, which was tested in a sheep model to ascertain its osteochondral regenerative potential, and in a rabbit model to further evaluate its ability to regenerate bone tissue. Macroscopic, microtomography, histology, histomorphometry, and immunohistochemical analysis were performed. In the sheep model, all analyses did not show significant differences compared to untreated defects (p > 0.05), with no evidence of cartilage and subchondral bone regeneration. In the rabbit model, this bone scaffold provided less ability to enhance tissue healing compared with a commercial bone scaffold. Moreover, persistence of scaffold material and absence of integration with connective tissue around the scaffolds were observed. These results raised some concerns about the osteochondral use of this chitosan composite scaffold, especially for the bone layer. Further studies are needed to explore the best formulation of chitosan-reinforced composites for osteochondral treatment.

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.

Bioperformance of chitosan/fluoride-doped diopside nanocomposite coatings deposited on medical stainless steel

This work focuses on the structure, bioactivity, corrosion, and biocompatibility characteristics of chitosan-matrix composites reinforced with various amounts of fluoride-doped diopside nanoparticles (at 20, 40, 60, and 80 wt%) deposited on stainless steel 316 L. Bioactivity studies reveal that the presence of the nanoparticles in the coatings induces apatite-forming ability to the surfaces. Based on electrochemical impedance spectroscopy and polarization experiments, the in vitro corrosion resistance of the substrate was enhanced by increasing the level of the nanoparticles in the coating. The sample containing 60% of the nanoparticles presented the highest osteoblast-like MG63 cell viability, in comparison to the other prepared and even control samples. Also, the cell attachment on the surfaces was improved with increasing the amount of the nanoparticles in the coatings. It is eventually concluded that the application of chitosan/fluoride-doped diopside nanocomposite coatings improves the bioperformance of metallic implants.

Marine Waste Utilization as a Source of Functional and Health Compounds

Consumer demand for convenience has led to large quantities of seafood being value-added processed before marketing, resulting in large amounts of marine by-products being generated by processing industries. Several bioconversion processes have been proposed to transform some of these by-products. In addition to their relatively low value conventional use as animal feed and fertilizers, several investigations have been reported that have demonstrated the potential to add value to viscera, heads, skins, fins, trimmings, and crab and shrimp shells by extraction of lipids, bioactive peptides, enzymes, and other functional proteins and chitin that can be used in food and pharmaceutical applications. This chapter is focused on reviewing the opportunities for utilization of these marine by-products. The chapter discusses the various products and bioactive compounds that can be obtained from seafood waste and describes various methods that can be used to produce these products with the aim of highlighting opportunities to add value to these marine waste streams.

Construction and evaluation of fibrillar composite hydrogel of collagen/konjac glucomannan for potential biomedical applications

Konjac glucomannan (KGM) is recognized as a safe material for its health-promoting benefits and thus widely used in various fields including pharmaceutical industry. In recent decades, the combination of collagen and KGM attracts more attentions for biomedical purpose, especially the hybrid films of collagen–KGM or collagen–KGM–polysaccharide. In this study, to further and deeply develop the intrinsic values of both collagen and KGM as biomaterials, a novel kind of composite hydrogel comprising collagen and KGM at a certain ratio was fabricated under mild conditions via fibrillogenesis process of the aqueous blends of collagen and KGM that experienced deacetylation simultaneously. The chemical composition, microcosmic architectures, swelling behavior, biodegradation and dynamic mechanic properties of such resulted composite hydrogels were systematically investigated. Biologic experiments, including cell culture in vitro and hypodermic implantation in vivo, were also conducted on these collagen/KGM composite hydrogels to evaluate their biologic performances. The relevant results prove that, based on collagen self-assembly behavior, this synthesis strategy is efficient to construct a composite hydrogel of collagen/KGM with improved mechanical properties, biodegradability, excellent biocompatibility and bioactivity, which are promising for potential biomedical applications such as tissue engineering and regenerative medicine.

RhBMP-2 and concomitant rapid material degradation synergistically promote bone repair and regeneration with collagen-hydroxyapatite nanocomposites

The effective treatment of bone defects is still a great challenge in clinical practice. Synthetic bone-grafting substitutes of composition and structure analogous to bone as well as incorporated with growth factors are considered to be a promising solution. In this study, a collagen-hydroxyapatite (CHA) nanocomposite scaffold was developed by collagen self-assembly with simultaneous HA synthesis. The physicochemical properties such as morphology, inorganic phase, thermal decomposition, specific surface area and pore size distribution were characterized. The osteogenicity of CHA in the absence or presence of recombinant human bone morphogenetic protein-2 (rhBMP-2) was assessed both by cell culturing and animal implantation experiments. The gene expression results showed that the osteogenic differentiation capacity of rat bone mesenchymal stem cells (rBMSCs) has been enhanced both by CHA and rhBMP-2. The efficient bone regeneration of femoral defects in rabbits was achieved with CHA and CHA pre-absorbed rhBMP-2 (CHA/B), confirmed by micro-computed tomography measurements, histological observation and immunohistochemical analyses. The CHA nanocomposite was completely degraded within 8 weeks and replaced by new bone. It was found that rhBMP-2 not only accelerated and enhanced bone formation, but also expedited the degradation of CHA. It is believed that the rhBMP-2 and concomitant rapid material degradation synergistically promote bone repair and regeneration with CHA. The biodegradation behavior of CHA in the presence of rhBMP-2 can be further investigated to gain an in-depth understanding of the complex interplays among biomaterials, growth factors and their target cells. The relevant knowledge will facilitate the search for a reasonable, safe and efficient methodology for the introduction of growth factors to biomaterials so as to achieve satisfactory tissue regeneration.

Novel cellulose/hydroxyapatite scaffolds for bone tissue regeneration: In vitro and in vivo study

Cellulose scaffolds containing nano- or micro-hydroxyapatite (nHA or μHA) were prepared by the regeneration of cellulose from its acetylated derivative and the mechanical immobilization of inorganic particles, followed by freeze-drying. Microtomographic (micro-computed tomography) evaluation revealed that both scaffolds presented a highly interconnected porous structure, with a mean pore diameter of 490 ± 94 and 540 ± 132 μm for cellulose/nHA and cellulose/μHA, respectively. In vitro and in vivo characterizations of the developed scaffolds were investigated. Commercially available bone allograft was used as a control material. For the in vitro characterization, osteoblastic cell cultures were used and characterized over time to evaluate cell adhesion, metabolic activity, and functional output (alkaline phosphatase activity and osteoblastic gene expression). The results revealed greater spreading cell distribution alongside an increased number of filopodia, higher MTT values, and significantly increased expression of osteoblastic genes (Runx-2, alkaline phosphatase, and BMP-2) for cellulose/nHA, compared with cellulose/μHA and the control. The in vivo biocompatibility was evaluated in a rabbit calvarial defect model. The investigated scaffolds were implanted in circular rabbit calvaria defects. Four- and 12-week bone biopsies were investigated using micro-computed tomography and histological analysis. Although both cellulose/HA scaffolds outperformed the assayed control, a significantly higher amount of newly formed mineralized tissue was found within the defects loaded with cellulose/nHA. Within the limitations of this study, the developed cellulose/HA scaffolds showed promising results for bone regeneration applications. The biological response to the scaffold seems to be greatly dependent on the HA particles' characteristics, with cellulose scaffolds loaded with nHA eliciting an enhanced bone response.

Enhanced bone regeneration composite scaffolds of PLLA/β-TCP matrix grafted with gelatin and HAp

The composite polylactide PLLA/β-TCP scaffolds were fabricated by solution casting and were coated with gelatin/hydroxyapatite (Gel/HAp) to improve the biological properties of the composite scaffolds. The Gel/HAp mixture was prepared using an in situ reaction, and a grafting-coating method was used to increase the efficiency of coating the PLLA/β-TCP matrix with Gel/HAp. First, free amino groups were introduced by 1,6-hexanediamine to aminolyze the PLLA/β-TCP matrix surface. Second, glutaraldehyde was coupled to Gel/HAp as a crosslinking agent. The structure and properties of Gel/HAp-modified PLLA/β-TCP films were characterized by Fourier transform infrared spectroscopy (FT-IR), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), and water contact angle measurements (WCA). The experimental results show that 23 wt% HAp was uniformly dispersed in the gelatin coating by in situ synthesis. The Gel/HAp composite coating was successfully immobilized on the aminolyzed PLLA/β-TCP surface via a chemical grafting method, which promoted a lower degradation rate and was more hydrophilic than a physical grafting method. The Gel/HAp composite coating adhered tightly and homogeneously to the hydrophobic PLLA/β-TCP surface. Moreover, mouse embryo osteoblast precursor (MC3T3-E1) cells grown on the scaffolds were behaviorally and morphologically characterized. The results indicated that the Gel/HAp composite coating was favorable for the attachment and proliferation of preosteoblasts and that Gel/HAp-NH-PLLA/β-TCP would be a candidate scaffold for bone repair.

An overview of chitin or chitosan/nano ceramic composite scaffolds for bone tissue engineering

Chitin and chitosan based nanocomposite scaffolds have been widely used for bone tissue engineering. These chitin and chitosan based scaffolds were reinforced with nanocomponents viz Hydroxyapatite (HAp), Bioglass ceramic (BGC), Silicon dioxide (SiO₂), Titanium dioxide (TiO₂) and Zirconium oxide (ZrO₂) to develop nanocomposite scaffolds. Plenty of works have been reported on the applications and characteristics of the nanoceramic composites however, compiling the work done in this field and presenting it in a single article is a thrust area. This review is written with an aim to fill this gap and focus on the preparations and applications of chitin or chitosan/nHAp, chitin or chitosan/nBGC, chitin or chitosan/nSiO₂, chitin or chitosan/nTiO₂ and chitin or chitosan/nZrO₂ in the field of bone tissue engineering in detail. Many reports so far exemplify the importance of ceramics in bone regeneration. The effect of nanoceramics over native ceramics in developing composites, its role in osteogenesis etc. are the gist of this review.

BAG-S53P4 as an additive to bone allografts: A laboratory study using an uniaxial compression test

We want to address the clinical issue of too sparse supply of allograft in total hip replacement and ambitions of controlling the grain size distribution. Bioglass BAG-S53P4 was evaluated as a bone graft additive to chemically treated allografts with controlled grain size distribution. Allografts were chemically cleaned (CG) and mixed with BAG-S53P4 additive (BG) for comparison. All samples were compacted with a dropped weight apparatus and then underwent a uniaxial compression test. The yield limit was determined by a uniaxial compression test and density was recorded while flowability was calculated. There was no difference between the yield stress limit of BG and CG after compaction (p=0.432). Adding BAG-S53P4 reduced flowability and could indicate better interlocking mechanism between particles. Adding BAG-S53P4 seems to have no impact on the yield stress limit. The extended allografts withstand the compaction equally good which makes it a valid bone substitute in total hip replacement. An in vivo loaded study is needed before clinical use can be recommended.

Chitin and chitosan composites for bone tissue regeneration

In the present world, where there is increased obesity and poor physical activity, the occurrence of bone disorders has also been increased steeply. Therefore, a significant progress has been made in organ transplantation, surgical reconstruction, and the use of artificial prostheses to treat the loss or failure of an organ or bone tissue in the recent years. Bone contains considerable amounts of minerals and proteins. The major component of bone is hydroxyapatite [Ca(10)(PO(4))(6)(OH)(2)] (60-65%) and is one of the most stable forms of calcium phosphate and it occurs along with other materials including collagen, chondroitin sulfate, keratin sulfate, and lipids. To remedy bone defects, new natural and synthetic materials are needed, which will have very similar properties as that of natural bone. Bone tissue engineering is a relatively new and emerging field, which paves the way for bone repair or regeneration. Polymers can serve as a matrix to support cell growth by having various properties such as biocompatibility, biodegradability, porosity, charge, mechanical strength, and hydrophobicity. Considerable attention has been given to chitin and chitosan composite materials and their applications in the field of bone tissue engineering in the recent years, which are natural biopolymers. This chapter reviews the various composites of chitin and chitosan, which are proved to be potential materials for bone tissue regeneration.

Physical properties and in vitro evaluation of collagen-chitosan-calcium phosphate microparticle-based scaffolds for bone tissue regeneration

Due to limitations of bone autografts and allografts, synthetic bone grafts using osteoconductive biomaterials have been designed. In this study, collagen-chitosan-calcium phosphate microparticle-based scaffolds fused with glycolic acid were compared to their counterparts without collagen in terms of degradation, cytocompatibility, porosity, and Young's modulus. It was found that 26-30% collagen was incorporated and that hydroxyapatite was present. Moreover, there were no differences between control and collagen scaffolds in degradation, cytocompatibility, porosity, and Young's modulus. In general, scaffolds exhibited 23% porosity, 0.6-1.2 MPa Young's modulus, 23% degradation over 4 weeks, and supported a four to seven fold increase in osteoblast cell number over 7 days in culture. Collagen can be incorporated into these bone graft substitute scaffolds, which show an improved degradation profile.

Mimicking natural bio-mineralization processes: a new tool for osteochondral scaffold development

In recent years, the concept of regenerative medicine has gained great importance, particularly in the field of orthopaedics, in which current solutions are based mainly on the replacement of damaged tissues with devices that function only as structural replacements with limited regenerative capacity. New regenerative solutions can be obtained by taking inspiration from nature, which surrounds us with a multitude of organisms endowed with extraordinary performance. In particular, bio-mineralization, which is the basis of the formation of load-bearing structures in vertebrate and invertebrate organisms, can be exploited to achieve innovative devices for the repair and reconstruction of bone and osteo-cartilaginous tissues.

Bone-like nanocomposites based on self-assembled protein-based matrices with Ca2+ capturing capability

In the present work, bone-like nanocomposites have been successfully synthesized based on the mineralization of self-assembled protein-based microgels. Such mircogels were achieved by the in vitro reconstitution of collagen monomeric solutions in the presence of alginate in a microemulsion system. Microstructural observations revealed that the collagen-alginate composite beads possessed a nanofibrous three dimensional (3D) interconnected porous microstructure. The obtained microgels were pre-incubated in calcium-containing solution to capture Ca(2+) ions, and subsequently immersed in phosphate-containing solution to initiate the formation of hydroxyapatite (HA) by an alternative incubating procedure. It was observed that a substantial amount of bone-like apatite nanocrystals were orderly and homogeneously deposited throughout the porous fibrillar networks. Herein, the collagen-alginate composite microgels served as a mineralization template for the synthesis of HA-polymer nanocomposites, which could be ideal vehicles potentially for cell carriers, bone repair and proteins and drugs delivery in tissue regeneration.

Chitosan composites for bone tissue engineering--an overview

Bone contains considerable amounts of minerals and proteins. Hydroxyapatite [Ca₁₀(PO₄)₆(OH)₂] is one of the most stable forms of calcium phosphate and it occurs in bones as major component (60 to 65%), along with other materials including collagen, chondroitin sulfate, keratin sulfate and lipids. In recent years, significant progress has been made in organ transplantation, surgical reconstruction and the use of artificial protheses to treat the loss or failure of an organ or bone tissue. Chitosan has played a major role in bone tissue engineering over the last two decades, being a natural polymer obtained from chitin, which forms a major component of crustacean exoskeleton. In recent years, considerable attention has been given to chitosan composite materials and their applications in the field of bone tissue engineering due to its minimal foreign body reactions, an intrinsic antibacterial nature, biocompatibility, biodegradability, and the ability to be molded into various geometries and forms such as porous structures, suitable for cell ingrowth and osteoconduction. The composite of chitosan including hydroxyapatite is very popular because of the biodegradability and biocompatibility in nature. Recently, grafted chitosan natural polymer with carbon nanotubes has been incorporated to increase the mechanical strength of these composites. Chitosan composites are thus emerging as potential materials for artificial bone and bone regeneration in tissue engineering. Herein, the preparation, mechanical properties, chemical interactions and in vitro activity of chitosan composites for bone tissue engineering will be discussed.