Effect of SiO2 in situ cross-linked CS/PVA on SrFe12O19 scaffolds prepared by 3D gel printing for targeting

The design of magnetic composite scaffolds with superior properties has the potential to construct a targeted delivery platform with hyperthermia. In this study, strontium hexaferrite (SrFe₁₂O₁₉, SrM) magnetic nanoparticles (MNPs) were obtained by the chemical precipitation method. Non-toxic cross-linked biogels were prepared for adhesive ceramic scaffolds, and chitosan/polyvinylalcohol (CS/PVA)-bonded SrM magnetic nanoscaffolds were successfully prepared by 3D gel printing (3DGP) method. The effects of PVA physical cross-linking and in situ formed SiO₂ on the properties of CS-bonded scaffolds were evaluated, and the compressive strengths were increased from 6.13 ± 2.45 MPa to 8.80 ± 2.02 MPa and 17.18 ± 2.15 MPa, respectively. The results showed that the saturation magnetization of SiO₂/CS/PVA/SrM composite scaffolds was 59.96 emu/g. In vitro immersion experiments showed that the degradation rates of SiO₂/CS/PVA/SrM scaffolds were 4.90% after 28 days, and the in situ SiO₂ improved the deposition of calcium salts on the scaffolds. The experiments showed that the SrM magnetic scaffolds could not only concentrate magnetic fields to improve the efficiency of targeting deposition but also achieve a weak targeting process without external magnetic field assistance. In vitro cell proliferation test showed that MC3T3-E1 cells had good adhesion and proliferation on the surface of SiO₂/CS/PVA/SrM scaffolds, which indicated that the scaffolds may be used for bone repairing.     

Glutaraldehyde‐crosslinked chitosan/hydroxyapatite bone repair scaffold and its application as drug carrier for icariin

Chitosan/hydroxyapatite (CS/HA) bone repair scaffolds crosslinked by glutaraldehyde (GA) were prepared. Characterization of morphology, structure, mechanical property, and porosity of scaffolds were evaluated. The influences of CS viscosity, HA content, and crosslinking degree on properties of scaffolds were discussed. SEM images showed that CS/HA scaffolds were porous with short rod‐like HA particles dispersing evenly in CS substrate. When [η]_CS = 5.75 × 10^?4, HA content = 65%, and crosslinking degree = 10%, the resulting CS/HA scaffolds had a flexural strength of 20 MPa and porosity of 60%, which could meet the requirements of bone repair materials. The scaffolds were used as drug carriers for icariin, and the impacts of loading time and crosslinking degree of scaffolds on drug‐loading dose were discussed. The suitable loading time was 24 h and it would be better to keep crosslinking degree no more than 10%. The drug release behavior demonstrated that the icariin‐loading CS/HA scaffolds could achieve basic drug sustained release effect. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 1539–1547, 2013     

Direct-write assembly of silicate and borate bioactive glass scaffolds for bone repair

Silicate (13-93) and borate (13-93B3) bioactive glass scaffolds were created by robotic deposition (robocasting) of organic solvent-based suspensions and evaluated in vitro for potential application in bone repair. Suspensions (inks) were developed, characterized, and deposited layer-by-layer to form three-dimensional scaffolds with a grid-like microstructure (porosity ≈50%; pore width 420 ± 30 μm). The mechanical response of the scaffolds was tested in compression, and the conversion of the glass to hydroxyapatite (HA)-like material in a simulated body fluid (SBF) was evaluated. As fabricated, the 13-93 scaffolds had a compressive strength 142 ± 20 MPa, comparable to the strength of human cortical bone, while the strength of the 13-93B3 scaffolds (65 ± 11 MPa), was far higher than that for trabecular bone. When immersed in SBF, the borate 13-93B3 scaffolds converted faster than the silicate 13-93 scaffolds to an HA-like material, but they also showed a sharper decrease in strength with immersion time. Based on their high compressive strength and bioactivity, the scaffolds fabricated in this work by robocasting could have potential application in the repair of load-bearing bone.     

3D pore-interconnected calcium phosphate bone blocks for bone tissue engineering

Pore size and connectivity of artificial bone scaffolds play key role in regulating cell ingrowth and vascularization during healing. The objective of this study was to develop a novel process for preparing 3D pore-interconnected open-cell bone substitutes with varying pore sizes. This was achieved by thermal-induced expansion, drying, then sintering the mixture of biphasic calcium phosphate (BCP) and a thermal responsive porogen comprising chitosan (CS) and hydroxypropyl methyl cellulose (HPMC). The interpolymer complexes (IPCs) of CS/HPMC were prepared and investigated by FT-IR. The mixtures of IPCs/BCP were heated up to 100 °C for analyzing their thermal expansion properties. This resulted in ~13% and ~42% volume increment for IPC-1/BCP and IPC-2/BCP, respectively, while ~230% volume increased in the case of IPC-3/BCP (therefore chosen for sintering bone blocks). Heating rate-dependent (0.20–0.25 °C/min range) sintering profiles for IPC-3/BCP were utilized to produce BCP bone blocks. Gasification of IPC during sintering resulted in the formation of interconnected porous structures, and the morphology was investigated by SEM, revealing varying sizes ranging from 106 ± 13 μm to 1123 ± 75 μm. The pore size range of bone blocks from 235 ± 46 μm to 459 ± 76 μm portrayed significantly high MC3T3-E1 cell viability with prominent filopodial extensions, and elongated cells, depicting efficient biocompatibility. Therefore, the process for preparing porous interconnected 3D bone blocks were feasible, thereby serving as an alternative for potential bone tissue engineering applications.     

Novel hydroxyapatite/tussah silk fibroin/chitosan bone-like nanocomposites

The nanocomposite particles of hydroxyapatite–tussah silk fibroin (HA–TSF) and HA–chitosan (HA–CS) were developed by biomimetic synthesis using Ca(NO₃)₂ and Na₃PO₄ as the precursors of inorganic phase in the presence of TSF and CS. Both nanocomposite particles were carbonate-substituted HA with low crystallinity. TSF and CS induced preferential alignment of HA crystallites along the direction of c-axis, and the induction effect of TSF was more than of CS. HA–TSF and HA–CS nanocomposite particles were found to be needle-like in the shape with a typical size of 100–200 nm in length and about 20 nm in width, and 115–250 nm in length and about 25 nm in width, respectively, as the result of the preferential arrangement of HA crystallites along c-axis intensified by TSF and CS. Based on both nanocomposite particles, the bone-like nanocomposites of HA–TSF/CS and HA–CS/TSF with the same compositions were prepared by isostatic pressing using CS and TSF concentrated solutions as adhesive composition, respectively. However, the two bone-like nanocomposites exhibited significantly different mechanical properties. The compressive strength, compressive modulus, and bending strength of HA–TSF/CS composite were significantly higher than of HA–CS/TSF composite. The fracture mechanism of both composites was analyzed by SEM observation. The study result indicates that HA–TSF/CS nanocomposite is an ideal candidate for bone substitute materials.     

Degradable and bioactive scaffold of calcium phosphate and calcium sulphate from self-setting cement for bone regeneration

Calcium sulphate/phosphate cement (CSPC) porous scaffolds were fabricated by introduction of calcium sulphate (CS) into calcium phosphate cement utilizing particle-leaching method. The morphology, porosity and mechanical strength as well as degradation of the CSPC scaffolds were characterized. The results reveal that the CSPC with 40 wt% CS content (40 CSPC) scaffolds with a porosity of 81% showed open macropores with the pore size of 200–500 μm. In addition, the 40 CSPC scaffolds with good degree of interconnected macropores degraded 60 wt% in Tris–HCl solution after 12 weeks. The proliferation, differentiation and morphology of MG₆₃ cells on the 40 CSPC scaffolds were determined using MTT assay, ALP activity and SEM. The results suggest that the CSPC scaffolds could stimulate cell proliferation and differentiation, indicating that CSPC scaffolds were biocompatible and had no negative effects on the cells in vitro. The CSPC scaffolds were implanted in femur bone defect of rabbits, and the in vivo biocompatibility and osteogenicity of the scaffolds were investigated. The results indicate that CSPC scaffolds exhibited good biocompatibility, degradability and osteogenesis in vivo.     

Preparation of chitosan-sodium alginate/bioactive glass composite cartilage scaffolds with high cell activity and bioactivity

Chitosan-sodium alginate/bioactive glass (CSB) composite cartilage scaffold with outstanding in vitro mineralization property and cytocompatibility is synthesized by freeze drying method. The effect of bioactive glass (BG) addition on the microstructure, porosity, swelling/degradation ratio, in vitro mineralization property and cytocompatibility of CSB scaffold is investigated by the characterization techniques of SEM, XRD, FTIR and BET. Results showed that CSB composite cartilage scaffold had a three-dimensional (3D) porous structure, and both porosity and average pore size met the requirements of cartilage tissue repair. Among, the typical CSB-1.0 had the largest overall pore size and lowest compressive modulus (1.083 ± 0.002 MPa). As the amount of BG increased, pore volume and porosity of CSB scaffolds gradually decreased, and the swelling and degradation ratios gradually reduced. After immersing in SBF for 3 d, cauliflower like hydroxyapatite (HA) was formed on CSB surface, indicating that the scaffold had good in vitro mineralization property. Moreover, the introduction of BG into the composite scaffold can improve the relative cell viability of MC3T3-E1 cells, and CSB-1.0 has the strongest ability to promote the proliferation of cells. Therefore, the as-obtained CSB scaffold can be used as a strong candidate for cartilage tissue engineering scaffold to meet clinical needs.     

Preparation and characterization of three-dimensional nanostructured macroporous bacterial cellulose/agarose scaffold for tissue engineering

We fabricated a three-dimensional nanostructured macroporous bacterial cellulose scaffold (3D BC scaffold) and a three-dimensional nanostructured macroporous bacterial cellulose/agarose scaffold (3D BC/A). Results of scanning electron microscopy (SEM) and mercury intrusion porosimeter showed that both the 3D BC and the 3D BC/A have interconnected macropores characterized by nanofibrous pore walls (The diameter of the dominant pores was about 100 μm and ranges from <1 μm to >1,000 μm). 3D BC/A also has high surface area (80 ± 5 m²/g) and sufficient porosity (88.5 ± 0.4%) compare with 3D BC (surface area: 92.81 ± 2.02 m²/g; porosity 90.42 ± 0.24%). 3D BC/A do support C5.18 cell and hBMSC attachment, proliferation evaluated with SEM, confocal microscopy and cell proliferation assay. Furthermore, 3D/ABC has enhanced mechanical property (ultimate compressive strength: 26.26 ± 4.6 kPa, Young’s modulus: 39.26 ± 5.72 kPa)) than that 3D/BC has (ultimate compressive strength: 7.04 ± 2.34 kPa, Young’s modulus: 10.76 ± 3.52 kPa). Overall, the 3D BC/A scaffold had more potential than 3D BC scaffold for using as a scaffold for tissue engineering and tissue repair applications.     

Photothermal effect of 3D printed hydroxyapatite composite scaffolds incorporated with graphene nanoplatelets

Porous scaffolds with photothermal effect could be used in the treatment of malignant bone tumors. Herein, graphene nanoplatelets were incorporated into the apatite/gelatin composites to construct porous scaffolds by 3D printing. Under near infrared laser irradiation, the composite scaffolds demonstrated high photothermal conversion efficiency. The temperature of scaffolds could be heated to 43 °C by controlling time and power of the laser irradiation, and then cooled to room temperature subsequently. Mild photothermal treatment (40–43 °C) was applied on MC3T3-E1 cells cultured on the scaffolds. It was found that after 3 cycles of treatment, the proliferation of MC3T3-E1 cells was significantly accelerated. It was suggested that the incorporation of graphene nanoplatelets into 3D printed hydroxyapatite composite scaffolds have the potential to accelerate bone regeneration after photothermal treatment for malignant bone tumors.     

3D printing of bioactive macro/microporous continuous carbon fibre reinforced hydroxyapatite composite scaffolds with synchronously enhanced strength and toughness

Continuous carbon fibre (CF) reinforced HA (CF/HA) composite scaffolds were prepared using a self-designed and manufactured 3D printer. The optimised design of nozzle structure and the tailored viscoelastic property of HA inks ensured compound extrusion of monofilament and multifilament CF with HA rod. The composite scaffolds designed using the CAD programme and sintered via a suitable process exhibited a hierarchical macro/microporous structure and contained approximately 50% HA and 50% β-TCP. The continuous CF synchronously enhanced the strength and toughness of the scaffolds. The compressive strengths of 1CF/HA and 5CF/HA were 11.4 ± 1.7 MPa and 16.3 ± 2.6 MPa, respectively, which were approximately double and triple compared with that of HA scaffolds. The fracture toughness of 1CF/HA was approximately double that of HA scaffolds and close to that of cortical bone. In vitro and in vivo studies demonstrated that 1CF/HA also had apatite formation capability and adequate bone regeneration capacity.     

Fabrication and Characterization of Multicomponent Polysaccharide/Nanohydroxyapatite Composite Scaffolds

Carrageenan–hyaluronic acid/nanohydroxyapatite/microcrystalline cellulose composite scaffolds with various amounts of microcrystalline cellulose content (from 0 to 60?wt%) were prepared using freeze-drying method. The results showed highly porous (from 94.0?±?1.09 to 85.0?±?1.05%) composite scaffolds with high water-uptake capacity, average pore size ranging 200–650?µm, and improved mechanical properties (in dry and wet states). Additionally, cytocompatibility of composite scaffolds was evaluated by in vitro culture of osteoblast (MC3T3-E1) cells for 1 and 3 days of incubation and demonstrated good cell adhesion, infiltration, and proliferation. Thus, as-obtained composite scaffolds may have promising application in low-loading bone tissue engineering applications.     

Polymer template fabrication of porous hydroxyapatite scaffolds with interconnected spherical pores

Porous hydroxyapatite (HA) scaffolds with interconnected spherical pores were fabricated by slip casting using a polymer template. Templates were produced using polymer beads, NaCl, and adhesive (N100). Effects of the preparation process on the pore structures and mechanical properties of the porous HA scaffolds were investigated. Pore interconnectivity was improved by adding NaCl particles with appropriate diameters to the polymer template. The size of the adhesive area could be controlled by adjusting the concentration of N100. The pore size could be controlled between 200 ± 42 and 400 ± 81 μm, and the porosity between 50.2 and 73.1%, by changing the size of the polymer beads and the volume of the NaCl particles. The compressive strength decreased as the porosity or pore size increased.     

Compressive strength of β-TCP scaffolds fabricated via lithography-based manufacturing for bone tissue engineering

Bone is a vital organ that is responsible for the support and movement of body as well as the storage and transportation of cells and nutrients. Disease, along with traumatic events, can leave regions of bone with large voids and/or defects. Related surgical procedures, such as allografts, autografts, and arthroplasty, are reported to amount to roughly €9.6bn annually, emphasising the need for bone repair/replacement globally. Tricalcium phosphate (TCP) is a bioactive ceramic that has been identified as a suitable material for bone tissue engineering applications due to its excellent bioresorbability and overall biocompatibility. Through lithography-based ceramic manufacturing (LCM), β -TCP scaffolds were fabricated across nine different designs in this work. Pore size, unit cell size, and unit cell geometry were altered to vary the porosity of these scaffolds. Following fabrication, the material composition, topography, macrostructure, and microstructure of the β-TCP scaffolds were characterised. The effects of porosity and unit cell geometry on the compressive strengths of β -TCP scaffolds were analysed in detail. Compressive strengths of the scaffolds were measured between 1.4 ± 0.5 MPa and 67.6 ± 13.3 MPa across a porosity range of 5.58 ± 0.09% to 59.36 ± 0.18%. The strength of these scaffolds was considerably lower than that of the compressive strength of cortical bone (100–200 MPa), but mimic the compressive strength of cancellous bone well (0.1–16 MPa). While scaffolds of β-TCP alone may not be suitable for load-bearing applications, they demonstrate enough mechanical stability for bone regeneration/tissue engineering applications. They hold more potential in the regeneration of small bone defects/voids or in composite materials.     

Physico-chemical and biological studies on three-dimensional porous silk/spray-dried mesoporous bioactive glass scaffolds

The incorporation of a bioactive inorganic phase in polymeric scaffolds is a good strategy for the improvement of the bioactivity and the mechanical properties, which represent crucial features in the field of bone tissue engineering. In this study, spray-dried mesoporous bioactive glass particles (SD-MBG), belonging to the binary system of SiO₂-CaO (80:20 mol%), were used to prepare composite scaffolds by freeze-drying technique, using a silk fibroin matrix. The physico-chemical and biological properties of the scaffolds were extensively studied. The scaffolds showed a highly interconnected porosity with a mean pore size in the range of 150 µm for both pure silk and silk/SD-MBG scaffolds. The elastic moduli of the silk and silk/SD-MBG scaffolds were 1.1±0.2 MPa and 6.9±1.0 MPa and compressive strength were 0.5±0.05 MPa and 0.9±0.2 MPa, respectively, showing a noticeable increase of the mechanical properties of the composite scaffolds compared to the silk ones. The contact angle value decreased from 105.3° to 71.2° with the incorporation of SD-MBG particles. Moreover, the SD-MBG incorporation countered the lack of bioactivity of the silk scaffolds inducing the precipitation of hydroxyapatite layer on their surface already after 1 day of incubation in simulated body fluid. The composite scaffolds showed good biocompatibility and a good alkaline phosphatase activity toward human mesenchymal stromal cells, showing the ability for their use as three-dimensional constructs for bone tissue engineering.     

Fabrication and characterization of chitosan/PVA with hydroxyapatite biocomposite nanoscaffolds

Nanofibrous biocomposite scaffolds of chitosan (CS), PVA, and hydroxyapatite (HA) were prepared by electrospinning. The scaffolds were characterized by FTIR, SEM, TEM, and XRD techniques. Tensile testing was used for the characterization of mechanical properties. Mouse fibroblasts (L929) attachment and proliferation on the nanofibrous scaffold were investigated by MTT assay and SEM observation. FTIR, TEM, and XRD results showed the presence of nanoHA in the scaffolds. The scaffolds have porous nanofibrous morphology with random fibers in the range of 100–700 nm diameters. The CS/PVA (90/10) fibrous matrix (without HA) showed a tensile strength of 3.1 ± 0.2 MPa and a tensile modulus 10 ± 1 MPa with a strain at failure of 21.1 ± 0.6%. Increase the content of HA up to 2% increased the ultimate tensile strength and tensile modulus, but further increase HA up to 5–10% caused the decrease of tensile strength and tensile modulus. The attachment and growth of mouse fibroblast was on the surface of nanofibrous structure, and cells' morphology characteristics and viability were unaffected. A combination of nanofibrous CS/PVA and HA that mimics the nanoscale features of the extra cellular matrix could be promising for application as scaffolds for tissue regeneration, especially in low or nonload bearing areas. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Modification of hydroxyapatite (HA) powder by carboxymethyl chitosan (CMCS) for 3D printing bioceramic bone scaffolds

The poor mechanical properties of 3D printed HA bone scaffold is always a challenge in tissue engineering, to address this issue, carboxymethyl chitosan (CMCS) was proposed to modify HA bone scaffolds by a physical blending method in this research. A series of HA and HA/CMCS composite ceramic scaffolds were printed by using piezoelectric inkjet 3D printing technology, and their properties were investigated in terms of forming quality, structural morphology, mechanical properties, degradability, cytotoxicity, and cell adhesion growth. The results of forming quality and structural morphology show that with the increase of CMCS content, the forming quality of the samples deteriorated, the pore size and porosity increased. However, when the content of CMCS reached 5 wt%, obvious cracks appeared on the surface of the sample, and the forming quality was relatively poor. The mechanical testing results indicated the toughness of composites could be enhanced by incorporating CMCS into HA, which was attributed to the higher strength connections of the CMCS polymer network between HA particles and the stronger interaction between HA and CMCS molecules. FTIR spectra further revealed the strong hydrogen bonding interaction between CMCS and HA. Moreover, the degradation rate and mineralization ability of the sample increased with the content of CMCS, but the compressive strength during degradation increased with the CMCS content, indicating that incorporating CMCS into HA cannot only improve the mechanical property and biological activity of the scaffold but also makes up the defect of slow degradation of pure HA scaffold. Finally, the cytotoxicity, cell adhesion, and cell proliferation tests show that HA and HA/CMCS composite samples had good cytocompatibility, HA/CMCS sample with 3 wt% CMCS possessed the best bioactivity. In summary, HA/CMCS composite powder with 3 wt% CMCS content is the optimal matrix material for 3D printing bone scaffolds.     

Preparation and performance of hydroxyapatite/Ti porous biocomposite scaffolds

Hydroxyapatite/titanium (HA/Ti) porous biocomposite scaffolds were prepared via a powder metallurgical method using NH₄HCO₃ as the pore-forming agent. The scaffolds induced HA formation and showed high bioactivity, and their porosity and compressive strength could be regulated by changing the NH₄HCO₃ dosage. When the NH₄HCO₃ dosage was 40.0%, the porosity was 67.0 ± 0.8%, and compressive strength was 19.0 ± 0.6 MPa, indicating the corresponding scaffold was an ideal choice for spongy bone repair.     

Fabrication of Hydroxyapatite/Ethylene-Vinyl Acetate/Polyamide 66 Composite Scaffolds by the Injection-Molding Method

This research investigated the injection-molding techniques to produce hydroxyapatite (HA)/ethylene-vinyl acetate (EVA)/polyamide 66 (PA66) composite scaffolds. The effects of HA, EVA, azodicarbonamide (AC) content and shot size on the mechanical properties, pore morphology, porosity and crystallization behavior of the composite scaffolds were analyzed by XRD, DSC, SEM and mechanical test. The compressive modulus and strength of the HA/EVA/PA66 scaffolds with a pore size of 200–600 µm are close to the cancellous bone. Compared with common methods to fabricate scaffolds, this process makes the fabrication of composite scaffolds come true in a rapid and convenient manner.     

Fabrication and compressive strength of porous hydroxyapatite scaffolds with a functionally graded core/shell structure

A novel type of porous hydroxyapatite (HA) scaffolds with a functionally graded core/shell structure was fabricated by freeze casting HA/camphene slurries with various HA contents into fugitive molds containing a graphite template with three-dimensionally interconnected pores for the creation of a highly porous core. All the fabricated samples had functionally graded core/shell structures with 3-D periodic pore networks in a core surrounded by a relatively dense shell. The overall porosity of the sample decreased from 60 to 38 vol% with increasing HA content in the HA/camphene slurry from 20 to 36 vol% due to a decrease in porosity in both the core and shell regions. In addition, the compressive strength was improved remarkably from 12 ± 1.1 to 32 ± 3.0 MPa. The in vitro cell test using a pre-osteoblast cell line showed that the samples had good biocompatibility.     

Two-step modification process to improve mechanical properties and bioactivity of hydroxyfluorapatite scaffolds

Porous ceramic scaffolds are synthetic implants, which support cell migration and establish sufficient extracellular matrix (ECM) and cell-cell interactions to heal bone defects. Hydroxyapatite (HA) scaffolds is one of the most suitable synthetic scaffolds for hard tissue replacement due to their bioactivity, biocompatibility and biomimetic features. However, the major disadvantages of HA is poor mechanical properties as well as low degradability rate and apatite formation ability. In this study, we developed a new method to improve the bioactivity, biodegradability and mechanical properties of natural hydroxyfluorapatite (HFA) by applying two-step coating process including ceramic and polymer coats. The structure, morphology and bioactivity potential of the modified and unmodified nanocomposite scaffolds were evaluated using transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and energy dispersive spectroscopy (EDS). The scaffold with optimized mechanical properties was HFA-30?wt%HT (HT stands for hardystonite) with a total porosity and pore size of 89?±?1 and 900–1000?µm, respectively. The compressive modulus and strength of HFA (porosity ~ 93?±?1) were improved from 108.81?±?11.12–251.45?±?12.2?MPa and 0.46?±?0.1–1.7?±?0.3?MPa in HFA-30?wt%HT sample, respectively. After applying poly(ε-caprolactone fumarate) (PCLF) polymer coating, the compressive strength and modules increased to 2.8?±?0.15 and 426.1?±?15.14?MPa, respectively. The apatite formation ability of scaffolds was investigated using simulated body fluid (SBF). The results showed that applying the hardystonite coating improve the apatite formation ability; however, the release of ions increased the pH. Whereas, modified scaffolds with PCLF could control the release of ions and improve the apatite formation ability as well.