In vitro evaluation for apatite-forming ability of cellulose-based nanocomposite scaffolds for bone tissue engineering

Nanocellulose-based hydrogels as versatile materials with interesting functional properties for tissue engineering applications

Tissue engineering has emerged as a remarkable field aiming to restore or replace damaged tissues through the use of biomimetic constructs. Among the diverse materials investigated for this purpose, nanocellulose-based hydrogels have garnered attention due to their intriguing biocompatibility, tunable mechanical properties, and sustainability. Over the past few years, numerous research works have been published focusing on the successful use of nanocellulose-based hydrogels as artificial extracellular matrices for regenerating various types of tissues. The review emphasizes the importance of tissue engineering, highlighting hydrogels as biomimetic scaffolds, and specifically focuses on the role of nanocellulose in composites that mimic the structures, properties, and functions of the native extracellular matrix for regenerating damaged tissues. It also summarizes the types of nanocellulose, as well as their structural, mechanical, and biological properties, and their contributions to enhancing the properties and characteristics of functional hydrogels for tissue engineering of skin, bone, cartilage, heart, nerves and blood vessels. Additionally, recent advancements in the application of nanocellulose-based hydrogels for tissue engineering have been evaluated and documented. The review also addresses the challenges encountered in their fabrication while exploring the potential future prospects of these hydrogel matrices for biomedical applications.

Degradable biomedical elastomers: paving the future of tissue repair and regenerative medicine

Degradable biomedical elastomers (DBE), characterized by controlled biodegradability, excellent biocompatibility, tailored elasticity, and favorable network design and processability, have become indispensable in tissue repair. This review critically examines the recent advances of biodegradable elastomers for tissue repair, focusing mainly on degradation mechanisms and evaluation, synthesis and crosslinking methods, microstructure design, processing techniques, and tissue repair applications. The review explores the material composition and cross-linking methods of elastomers used in tissue repair, addressing chemistry-related challenges and structural design considerations. In addition, this review focuses on the processing methods of two- and three-dimensional structures of elastomers, and systematically discusses the contribution of processing methods such as solvent casting, electrostatic spinning, and three-/four-dimensional printing of DBE. Furthermore, we describe recent advances in tissue repair using DBE, and include advances achieved in regenerating different tissues, including nerves, tendons, muscle, cardiac, and bone, highlighting their efficacy and versatility. The review concludes by discussing the current challenges in material selection, biodegradation, bioactivation, and manufacturing in tissue repair, and suggests future research directions. This concise yet comprehensive analysis aims to provide valuable insights and technical guidance for advances in DBE for tissue engineering.

Proliferation and differential regulation of osteoblasts cultured on surface-phosphorylated cellulose nanofiber scaffolds

Phosphorus-containing polymers have received much attention for their excellent ability to regulate bone cell differentiation and calcification. Given the increasing concern about environmental issues, it is promising to utilize "green" biomaterials to construct novel cell culture scaffolds for bone tissue engineering. Herein, surface-phosphorylated cellulose nanofibers (P-CNFs) were fabricated as a novel green candidate for osteoblast culture. Compared with native CNF, P-CNFs possessed shorter fiber morphology with tunable phosphate group content (0-1.42 mmol/g). The zeta-potential values of CNFs were enhanced after phosphorylation, resulting in the formation of uniform and stable scaffolds. The cell culture behavior of mouse osteoblast (MC3T3-E1) cells showed a clear phosphate content-dependent cell proliferation. The osteoblast cells adhered well and proliferated efficiently on P-CNF0.78 and P-CNF1.05, with phosphate contents of 0.78 and 1.05 mmol/g, respectively, whereas the cells grown on native CNF substrate formed aggregates due to poor cell attachment and exhibited limited cell proliferation. In addition, the P-CNF substrates with optimal phosphate content provided a favorable cellular microenvironment and significantly promoted osteogenic differentiation and calcification, even in the absence of a differentiation inducer. The bio-based P-CNFs are expected to mimic the bone components and provide a means to regulate osteoblast proliferation and differentiation in bone tissue engineering.

The Diamond Concept Enigma: Recent Trends of Its Implementation in Cross-linked Chitosan-Based Scaffolds for Bone Tissue Engineering

An increasing number of publications over the past ten years have focused on the development of chitosan-based cross-linked scaffolds to regenerate bone tissue. The design of biomaterials for bone tissue engineering applications relies heavily on the ideals set forth by a polytherapy approach called the "Diamond Concept". This methodology takes into consideration the mechanical environment, scaffold properties, osteogenic and angiogenic potential of cells, and benefits of osteoinductive mediator encapsulation. The following review presents a comprehensive summarization of recent trends in chitosan-based cross-linked scaffold development within the scope of the Diamond Concept, particularly for nonload-bearing bone repair. A standardized methodology for material characterization, along with assessment of in vitro and in vivo potential for bone regeneration, is presented based on approaches in the literature, and future directions of the field are discussed.

Bioactive hybrid membrane-based cellulose acetate/bioactive glass/hydroxyapatite/carbon nanotubes nanocomposite for dental applications

The present work aimed to fabricate a set of hybrid bioactive membrane in the form of bio-nanocomposite films for dental applications using the casting dissolution procedures. The formulation of the targeted materials was consisting of cellulose acetate/bioactive glass/hydroxyapatite/carbon nanotubes with a general abbreviation CA-HAP-BG-SWCNTs. The nanocomposites were characterized using XRD, FTIR, SEM-EDX and Raman spectroscopy. XRD, FTIR and SEM characters confirm the nanocomposites formation with good compatibility. The fabricated materials had a semi crystalline structure. The mechanical and thermal properties, as well as contact angle and bioactivity of the fabricated nanocomposites were investigated. The SEM images for showed beehive-like architectures with a thicker frame for the second material. All fabricated materials showed good thermal behaviors. Furthermore, the agar diffusion antimicrobial study showed that the prepared nanocomposites do not exhibit an antibacterial activity against five pathogenic bacterial strains. Additionally, cytotoxicity of a dental nanocomposite filling agent was evaluated. Vero normal cells were incubated with test materials for 72h at 37 °C and 5% CO₂. Cell viability was detected using a SRB assay. All nanocomposites were mildly to non-cytotoxic to Vero cells at high concentration in contrast to the inhibitory effect of doxorubicin which was added at 10-fold lower concertation than the nanocomposites. Hence, the proposed nanocomposite is promising candidates for dental applications.

Frontiers of Hydroxyapatite Composites in Bionic Bone Tissue Engineering

Bone defects caused by various factors may cause morphological and functional disorders that can seriously affect patient's quality of life. Autologous bone grafting is morbid, involves numerous complications, and provides limited volume at donor site. Hence, tissue-engineered bone is a better alternative for repair of bone defects and for promoting a patient's functional recovery. Besides good biocompatibility, scaffolding materials represented by hydroxyapatite (HA) composites in tissue-engineered bone also have strong ability to guide bone regeneration. The development of manufacturing technology and advances in material science have made HA composite scaffolding more closely related to the composition and mechanical properties of natural bone. The surface morphology and pore diameter of the scaffold material are more important for cell proliferation, differentiation, and nutrient exchange. The degradation rate of the composite scaffold should match the rate of osteogenesis, and the loading of cells/cytokine is beneficial to promote the formation of new bone. In conclusion, there is no doubt that a breakthrough has been made in composition, mechanical properties, and degradation of HA composites. Biomimetic tissue-engineered bone based on vascularization and innervation show a promising future.

Polysaccharide-based nanocomposites for biomedical applications: a critical review

Polysaccharides (PSA) have taken specific position among biomaterials for advanced applications in medicine. Nevertheless, poor mechanical properties are known as the main drawback of PSA, which highlights the need for PSA modification. Nanocomposites PSA (NPSA) are a class of biomaterials widely used as biomedical platforms, but despite their importance and worldwide use, they have not been reviewed. Herein, we critically reviewed the application of NPSA by categorizing them into generic and advanced application realms. First, the application of NPSA as drug and gene delivery systems, along with their role in the field as an antibacterial platform and hemostasis agent is discussed. Then, applications of NPSA for skin, bone, nerve, and cartilage tissue engineering are highlighted, followed by cell encapsulation and more critically cancer diagnosis and treatment potentials. In particular, three features of investigations are devoted to cancer therapy, i.e., radiotherapy, immunotherapy, and photothermal therapy, are comprehensively reviewed and discussed. Since this field is at an early stage of maturity, some other aspects such as bioimaging and biosensing are reviewed in order to give an idea of potential applications of NPSA for future developments, providing support for clinical applications. It is well-documented that using nanoparticles/nanomaterials above a critical concentration brings about concerns of toxicity; thus, their effect on cellular interactions would become critical. We compared nanoparticles used in the fabrication of NPSA in terms of toxicity mechanism to shed more light on future challenging aspects of NPSA development. Indeed, the neutralization mechanisms underlying the cytotoxicity of nanomaterials, which are expected to be induced by PSA introduction, should be taken into account for future investigations.

Biocompatibility of hydroxyethyl cellulose/glycine/RuO2 composite scaffolds for neural-like cells

Fabrication of scaffolds for nerve regeneration is one of the most challenging topics in regenerative medicine at the moment, which is also interlinked with the development of biocompatible substrates for cells growth. This work is targeted towards the development of green biomaterial composite scaffolds for nerve cell culture applications. Hybrid scaffolds of hydroxyethyl cellulose/glycine (HEC/Gly) composite doped with different concentrations of green ruthenium oxide (RuO₂) were synthesized and characterized via a combination of different techniques. X-rays diffraction (XRD) and differential scanning calorimetry (DSC) analyses showed a crystalline nature for all the samples with noticeable decrease in the peak intensity of the fabricated scaffolds as compared to that for pure glycine. Fourier transform infrared spectroscopy (FTIR) tests revealed an increase in the vibrational bands of the synthesized RuO₂ containing scaffolds which are related to the functional groups of the natural plant extract (Aspalathuslinearis) used for RuO₂ nanoparticles (NPs) synthesis. Scanning electron microscopy (SEM) results revealed a 3D porous structure of the scaffolds with variant features attributed to the concentration of RuO₂ NPs in the scaffold. The compressive test results recorded an enhancement in mechanical properties of the fabricated scaffolds (up to 8.55 MPa), proportionally correlated to increasing the RuO₂ NPs concentration in HEC/Gly composite scaffold. Our biocompatibility tests revealed that the composite scaffolds doped with 1 and 2 ml of RuO₂ demonstrated the highest proliferation percentages (152.2 and 135.6%) compared to control. Finally, the SEM analyses confirmed the impressive cells attachments and differentiation onto the scaffold surfaces as evidenced by the presence of many neuron-like cells with apparent cell bodies and possessing few short neurite-like processes. The presence of RuO₂ and glycine was due to their extraordinary biocompatibility due to their cytoprotective and regenerative effects. Therefore, we conclude that these scaffolds are promising for accommodation and growth of neural-like cells.

Tricomposite gelatin-carboxymethylcellulose-alginate bioink for direct and indirect 3D printing of human knee meniscal scaffold

The development of technologies that could ease the production of customizable patient-specific tissue engineering constructs having required biomechanical properties and restoring function in damaged tissue is the need of the hour. In this study, we report the optimization of composite, bioactive and biocompatible tripolymeric hydrogel bioink, suitable for both direct and indirect printing of customizable scaffolds for cartilage tissue engineering applications. A customized hierarchical meniscal scaffold was designed using solid works software and developed using a negative mould made of polylactic acid (PLA) filament and by a direct 3D printing process. A composite tripolymeric bioink made of gelatin, carboxymethyl cellulose (CMC) and alginate was optimized and characterized for its printability, structural, bio-mechanical and bio-functional properties. The optimized composite hydrogel bioink was extruded into the negative mould with and without live cells, cross-linked and the replica of meniscus structure was retrieved aseptically. The cellular proliferation, apatite formation, and extracellular matrix secretion from negative printed meniscal scaffold were determined using MTT, live/dead and collagen estimation assays. A significant increase in collagen secretion, cellular proliferation and changes in biomechanical properties was observed in the 3D scaffolds with MG63-osteosarcoma cells indicating its suitability for cartilage tissue engineering.

Development of Porous Photopolymer Resin-SWCNT Produced by Digital Light Processing Technology Using for Bone Femur Application

BACKGROUND

Although bone tissue has the unique characteristic of self-repair in fractures, bone grafting is needed in some situations. The synthetic substances that are used in such situations should bond to the porous bones, be biocompatible and biodegradable, and do not stimulate the immune responses. Biomaterial engineering is the science of finding and designing novel products. In principle, the most suitable biodegradable matrix should have adequate compressive strength of more than two megapascals. At this degradation rate, the matrix can eventually be replaced by the newly formed bone, and the osteoprogenitor cells migrate into the scaffold. This study aimed to evaluate the fabrication of a scaffold made of polymer-ceramic nanomaterials with controlled porosity resembling that of spongy bone tissue.

METHODS

A compound of resin polymer, single-walled carbon nanotube (SWCNT) as reinforcement, and hydroxyapatite (HA) were dissolved using an ultrasonic and magnetic stirrer. A bio-nano-composite scaffold model was designed in the SolidWorks software and built using the digital light processing (DLP) method. Polymer-HA scaffolds with the solvent system were prepared with similar porosity to that of human bones.

RESULTS

HA-polymer scaffolds had a random irregular microstructure with homogenizing porous architecture. The SWCNT improved the mechanical properties of the sample from 25 MPa to 36 MPa besides having a proper porosity value near 55%, which can enhance the transformation and absorption of protein in human bone.

CONCLUSION

The combined bio-nanocomposite had a suitable porous structure with acceptable strength that allowed it to be used as a bone substitute in orthopedic surgery.

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.

In-Situ Synthesis and Characterization of Chitosan/Hydroxyapatite Nanocomposite Coatings to Improve the Bioactive Properties of Ti6Al4V Substrates

Ti6Al4V alloy is still attracting great interest because of its application as an implant material for hard tissue repair. This research aims to produce and investigate in-situ chitosan/hydroxyapatite (CS/HA) nanocomposite coatings based on different amounts of HA (10, 50 and 60 wt.%) on alkali-treated Ti6Al4V substrate through the sol-gel process to enhance in vitro bioactivity. The influence of different contents of HA on the morphology, contact angle, roughness, adhesion strength, and in vitro bioactivity of the CS/HA coatings was studied. Results confirmed that, with increasing the HA content, the surface morphology of crack-free CS/HA coatings changed for nucleation modification and HA nanocrystals growth, and consequently, the surface roughness of the coatings increased. Furthermore, the bioactivity of the CS/HA nanocomposite coatings enhanced bone-like apatite layer formation on the material surface with increasing HA content. Moreover, CS/HA nanocomposite coatings were biocompatible and, in particular, CS/10 wt.% HA composition significantly promoted human mesenchymal stem cells (hMSCs) proliferation. In particular, these results demonstrate that the treatment strategy used during the bioprocess was able to improve in vitro properties enough to meet the clinical performance. Indeed, it is predicted that the dense and crack-free CS/HA nanocomposite coatings suggest good potential application as dental implants.

Bioactive polymeric scaffolds for osteogenic repair and bone regenerative medicine

The loss of bone tissue is a striking challenge in orthopedic surgery. Tissue engineering using various advanced biofunctional materials is considered a promising approach for the regeneration and substitution of impaired bone tissues. Recently, polymeric supportive scaffolds and biomaterials have been used to rationally promote the generation of new bone tissues. To restore the bone tissue in this context, biofunctional polymeric materials with significant mechanical robustness together with embedded materials can act as a supportive matrix for cellular proliferation, adhesion, and osteogenic differentiation. The osteogenic regeneration to replace defective tissues demands greater calcium deposits, high alkaline phosphatase activity, and profound upregulation of osteocalcin as a late osteogenic marker. Ideally, the bioactive polymeric scaffolds (BPSs) utilized for bone tissue engineering should impose no detrimental impacts and function as a carrier for the controlled delivery and release of the loaded molecules necessary for the bone tissue regeneration. In this review, we provide comprehensive insights into different synthetic and natural polymers used for the regeneration of bone tissue and discuss various technologies applied for the engineering of BPSs and their physicomechanical properties and biological effects.

Effect of Different Concentration of Cellulose Nanocrystals Comprising Hydroxyethyl Cellulose / Poly(Vinyl Alcohol) as a Bone Tissue Engineering Scaffold

In this study, biodegradable scaffolds based on hydroxyethyl cellulose (HEC) (5 wt%) and poly (vinyl alcohol) (PVA) (15 wt%) with different percentages of celullose nanocrystal (CNC) (1 and 7 wt%) were fabricated by lyophilization method to get highly porous scaffolds. These scaffolds were made water insoluble by cross-linking via heat treatment. The morphology and thermal properties of HEC/PVA/CNCs scaffolds were characterized by using Scanning Electron Microscope (SEM) and Thermogravimetric Analysis (TGA). The morphological study showed that both prepared scaffold have highly porous structures with good pore interconnected structure. It was observed that thermal properties of scaffolds increased significantly as the concentration of CNCs increased. Cytotoxicity studies on scaffolds were carried out by utilizing human fetal osteoblast (hFOB) cells using DAPI nuclear stain and then confirmed using SEM. hFOB cells were able to attach and spread on all scaffolds. Incorporated CNCs as reinforcing nanofiller on scaffolds promising a superior functionality in bone tissue engineering.

The effect of biomimetic coating and cuttlebone microparticle reinforcement on the osteoconductive properties of cellulose-based scaffolds

Polymer-based scaffolds have already gained popularity in many biomedical applications due to convenient routes for fabrication and favourable structural, physicochemical and functional characteristics. However, polymeric scaffolds lack osteoconductivity and some synthetic polymers carry the risk of inflammatory response caused by degradation by-products. Those facts limit their practical use in bone tissue engineering. In this study, three-dimensional (3D) porous scaffolds from naturally derived polymer, namely regenerated cellulose, were prepared using a non-hydrolytic sol-gel and lyophilization techniques. To induce osteoconductive properties of the polymeric scaffolds, cuttlebone microparticles were immobilized and the surface coating was achieved via in vitro mineralization using 10-fold concentrated simulated body fluid (10x SBF). Biogenic activity of cuttlebone is explained by its chemical composition, which includes polysaccharide β-chitin and macro-, micro- and trace elements favourable for mineralization. Parallel the scaffolds were examined during long-term (24 weeks) in vitro mineralization in 1x SBF for the purpose to investigate apatite-forming ability of the scaffolds. A nice cauliflower-like structures and needle-like dents of the spherical aggregates, which are characteristic to hydroxyapatite precursors, were observed on the surface of cellulose/cuttlebone scaffolds by SEM. 10x SBF coating enhanced cell attachment to the scaffolds because SBF elements are known to increase bioactivity by inducing re-deposition of carbonate apatite crystallites on scaffold surface. Additionally, calcium and phosphate depositions were clearly observed on the developed scaffolds using von Kossa and Alizarin Red S staining. Proliferative and osteoconductive effects on the osteoblast-like MG-63 cells demonstrate the cellulose/cuttlebone scaffolds soaked in 10x SBF as a favourable material for bone tissue engineering.

A novel magnetic bifunctional nanocomposite scaffold for photothermal therapy and tissue engineering

In recent years, porous bifunctional scaffolds with hyperthermal and tissue regeneration functions play an essential role in the efficient cancerous bone tumors treatment. In this work, the nanocomposite scaffolds of gelatin (polymer phase) and akermanite (ceramic phase) were prepared by entrapping carboxyl-functionalized multi-walled carbon nanotube (MWNT) and embedding magnetic nanoparticles of iron oxide into the porous matrix as photothermal conversion agents. The obtained scaffolds and their components were characterized using FTIR, FESEM, TEM, EDS, DLS, and VSM analysis. The mechanical properties of the prepared scaffolds were also investigated. The swelling behavior of the scaffolds in PBS as well as biodegradation and protein adsorption capability were evaluated. The addition of nanoparticles into the gelatin/akermanite matrix efficiently increased the adsorption of bovine serum albumin on the surface of the composite scaffold and contrarily decreased its degradation rate in the presence of lysozyme. The prepared scaffolds exhibited a high photothermal performance using NIR laser with different power intensity and irradiation time. Finally, the biocompatibility of the scaffold was confirmed using G292 osteoblastic cells through MTT assays. It can therefore be concluded that synthesized scaffolds have a great potential in bone tissue engineering and probably treatment of tumor related bone defects.

Using Chitosan Besides Nano Hydroxyapatite and Fluorohydroxyapatite Boost Dental Pulp Stem Cell Proliferation

The dental tissue scaffold must provide a favorable surface for dental pulp stem cell attachment and proliferation. Employing nanohydroxyapatite (HA) and nanofluorohydroxyapatite (FHA) beside synthetic and organic polymer in favor of scaffolds would be used in bone and dental tissue engineering. In this research, nanoHA and FHA/chitosan scaffolds were synthesized by freeze-drying technique. Surface morphology, chemical composition and hydrophilicity have a great impact on initial cell attachment which will further affect the cell viability and proliferation which evaluated by SEM, XRD and contact angle measurement. Bioactivity of scaffolds was investigated by immersion in simulated body fluid (SBF) and cell proliferation assay. In freeze-drying technique percentage usage of hydroxyapatite could be risen up to 40% and shown better macro-mechanical and physical properties and bioactivity. According to obtained results by adding chitosan, contact angle was decreased by %54 and %37 for polycaprolactone (PCL)/HA and PCL/FHA scaffolds. In addition, addition of chitosan causes significant increase in the cell proliferation for PCL/HA and PCL/FHA up to 81% and 164%, respectively. These results indicate that PCL/FHA/chitosan scaffold represent a big potential for dental tissue engineering.

3D-printed scaffolds of mesoporous bioglass/gliadin/polycaprolactone ternary composite for enhancement of compressive strength, degradability, cell responses and new bone tissue ingrowth

BACKGROUND

Due to the increasing number of patients with bone defects, bone nonunion and osteo-myelitis, tumor and congenital diseases, bone repair has become an urgent problem to be solved.

METHODS

In this study, the 3D-printed scaffolds of ternary composites containing mesoporous bioglass fibers of magnesium calcium silicate (mMCS), gliadin (GA) and polycaprolactone (PCL) were fabricated using a 3D Bioprinter.

RESULTS

The compressive strength and in vitro degradability of the mMCS/GA/PCL composites (MGPC) scaffolds were improved with the increase of mMCS content. In addition, the attachment and proliferation of MC3T3-E1 cells on the scaffolds were significantly promoted with the increase of mMCS content. Moreover, the cells with normal phenotype attached and spread well on the scaffolds surfaces, indicating good cytocompatibility. The scaffolds were implanted into the femur defects of rabbits, and the results demonstrated that the scaffold containing mMCS stimulated new bone formation and ingrowth into the scaffolds through scaffolds degradation in vivo. Moreover, the expression of type I collagen into scaffolds was enhanced with the increase of mMCS content.

CONCLUSION

The 3D-printed MGPC scaffold with controllable architecture, good biocompatibility, high compressive strength, proper degradability and excellent in vivo osteogenesis has great potential for bone regeneration.

Novel alginate/hydroxyethyl cellulose/hydroxyapatite composite scaffold for bone regeneration: In vitro cell viability and proliferation of human mesenchymal stem cells

Sodium alginate (SA)/hydroxyethylcellulose (HEC)/hydroxyapatite (HA) composite scaffolds were explored for enhanced in vitro bone regeneration. The SA/HEC/HA composites were synthesized using the lyophilization technique and further cross-linked in the presence of calcium ions to form composite hydrogel networks. The physicochemical, thermal behavior and morphology properties of the prepared scaffolds were characterized through XRD, DSC/TGA, FTIR and SEM. Furthermore, the mechanical behavior of the under investigated scaffolds was determined using texture analyzer. The in vitro bioactivity in SBF and adsorption of bovine serum albumin as well as cell viability for all the prepared scaffolds were also tested. The results indicated that the higher HA concentration (40wt%) enhanced the mechanical properties (23.9MPa), bioactivity and protein adsorption. Cell viability of the tested scaffolds confirmed the non-toxicity of the fabricated systems on the human mesenchymal stem cells (hMSCs). Proliferation capability was also confirmed for the tested scaffolds after 3 and 7days, but the higher HA-containing scaffold showed increased cell populations specially after 7days compared to HA-free scaffolds. This novel composite material could be used in bone tissue engineering as a scaffold material to deliver cells and biologically active molecules.

Biocompatible nanocomposite scaffolds based on copolymer-grafted chitosan for bone tissue engineering with drug delivery capability

Significant efforts have been made to develop a suitable biocompatible scaffold for bone tissue engineering. In this work, a chitosan-graft-poly(acrylic acid-co-acrylamide)/hydroxyapatite nanocomposite scaffold was synthesized through a novel multi-step route. The prepared scaffolds were characterized for crystallinity, morphology, elemental analysis, chemical bonds, and pores size in their structure. The mechanical properties (i.e. compressive strength and elastic modulus) of the scaffolds were examined. Further, the biocompatibility of scaffolds was determined by MTT assays on HUGU cells. The result of cell culture experiments demonstrated that the prepared scaffolds have good cytocompatibility without any cytotoxicity, and with the incorporation of hydroxyapatite in their structure improves cell viability and proliferation. Finally, celecoxib as a model drug was efficiently loaded into the prepared scaffolds because of the large specific surface area. The in vitro release of the drug displayed a biphasic pattern with a low initial burst and a sustained release of up to 14days. Furthermore, different release kinetic models were employed for the description of the release process. The results suggested that the prepared cytocompatible and non-toxic nanocomposite scaffolds might be efficient implants and drug carriers in bone-tissue engineering.

The effect of hydroxyapatite in biopolymer-based scaffolds on release of naproxen sodium

A scaffold capable of controlling drug release is highly desirable for bone tissue engineering. The objective of this study was to develop and characterize a highly porous biodegradable scaffold and evaluate the kinetic release behavior for the application of anti-inflammatory drug delivery. Porous scaffolds consisting of chitosan, poly(acrylic acid), and nano-hydroxyapatite were prepared using the freeze-drying method. The nanocomposite scaffolds were characterized for structure, pore size, porosity, and mechanical properties. The nanocomposite scaffolds were tested and characterized using Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), energy-dispersive analysis of X-ray (EDS), X-ray diffraction (XRD) analysis, and tensile test instrument. The results showed that the pores of the scaffolds were interconnected, and their sizes ranged from 145 µm to 213 μm. The mechanical properties were found close to those of trabecular bone of the same density. The ability of the scaffolds to deliver naproxen sodium as a model drug in vitro was investigated. The release profile of naproxen sodium was measured in a phosphate-buffered saline solution by a ultra-violet spectrophotometer that was controlled by the Fickian diffusion mechanism. These results indicated that the chitosan-graft-poly(acrylic acid)/nano-hydroxyapatite scaffold may be a promising biomedical scaffold for clinical use in bone tissue engineering with a potential for drug delivery. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 104A: 2992-3003, 2016.

Grafting of poly[(methyl methacrylate)-block-styrene] onto cellulose via nitroxide-mediated polymerization, and its polymer/clay nanocomposite

For the first time, nitroxide-mediated polymerization (NMP) was used for synthesis of graft and block copolymers using cellulose (Cell) as a backbone, and polystyrene (PSt) and poly(methyl metacrylate) (PMMA) as the branches. For this purpose, Cell was acetylated by 2-bromoisobutyryl bromide (BrBiB), and then the bromine group was converted to 4-oxy-2,2,6,6-tetramethylpiperidin-1-oxyl group by a substitution nucleophilic reaction to afford a macroinitiator (Cell-TEMPOL). The macroinitiator obtained was subsequently used in controlled graft and block copolymerizations of St and MMA monomers to yield Cell-g-PSt and Cell-g-(PMMA-b-PSt). The chemical structures of all samples as representatives were characterized by FTIR and (1)H NMR spectroscopies. In addition, Cell-g-(PMMA-b-PSt)/organophilic montmorillonite nanocomposite was prepared through a solution intercalation method. TEM was used to evaluate the morphological behavior of the polymer-clay system. It was demonstrated that the addition of small percent of organophilic montmorillonite (O-MMT; 3wt.%) was enough to improve the thermal stability of the nanocomposite.