Electrospun bioactive nanocomposite scaffolds of polycaprolactone and nanohydroxyapatite for bone tissue engineering

Nanocomposite scaffolds based on nanofibrous poly(epsilon-caprolactone) (PCL) and nanohydroxyapatite (nanoHA) with different compositions (wt%) were prepared by electrostatic co-spinning to mimic the nano-features of the natural extracellular matrix (ECM). NanoHA was found to be well dispersed in polymers up to the addition of 20 wt%, after ultrasonication. The composite scaffolds were characterized for structure and morphology using XRD, EDX, SEM, and DSC. The scaffolds have a porous nanofibrous morphology with fibers (majority) having diameters in the range of 450-650 nm, depending on composition, and interconnected pore structures. SEM, EDX, and XRD analyses have confirmed the presence of nanoHA in the fibers. As the nanoHA content in the fibers increases, the surface of fibers becomes rougher. The mechanical (tensile) property measurement of the electrospun composites reveals that as the nanoHA content increases, the ultimate strength increases from 1.68 MPa for pure PCL to 2.17, 2.65, 3.91, and 5.49 MPa for PCL/nanoHA composites with the addition of 5, 10, 15, and 20 wt% nanoHA, respectively. Similarly the tensile modulus also increases gradually from 6.12 MPa to 21.05 MPa with the increase of nanoHA content in the PCL/nanoHA fibers, revealing an increase in stiffness of the fibers due to the presence of HA. DSC analysis reveals that as nanoHA in the composite scaffolds increases, the melting point slightly increases due to the good dispersion and interface bonding between PCL and nanoHA.     

Fabrication and characterization of chitosan microspheres agglomerated scaffolds for bone tissue engineering

In the presented paper authors describe a method for bone scaffolds fabrication. The technique is based on the agglomeration of chitosan microspheres. The fabrication process is complex and consists of a few steps: chitosan spheres extrusion, scaffold formation by compression followed by the spheres agglomeration and bonding with cross-linking agent (STPP, sodium tripolyphosphate). The described method allows manufacturing of porous materials with controllable shape, pore size distribution and their interconnectivity. In this technique 3D scaffold porosity can be regulated by altering spheres diameter. Authors studied influence of cross-linker concentrations and time of cross-linking process on the scaffold morphology, mechanical properties, enzymatic degradation rate (in the presence of lysozyme) and human osteoblasts response. Surface morphology and topography were evaluated by SEM. Porosity and pore interconnectivity were observed via μCT scanning. Mechanical tests showed that chitosan scaffolds perform compression characteristic (Young Modulus) similar to natural bone. Cytotoxicity established by XTT assay confirmed that most of the developed composite materials do not show toxic properties. Osteoblast adhesion and morphology were analyzed by SEM and optical microscopy.     

Macroporous bioactive glass-ceramic scaffolds for tissue engineering

Highly bioactive scaffolds for tissue engineering were synthesized using a glass belonging to the SiO₂-CaO-K₂O (SCK) system. The glass SCK was prepared by a traditional melting-quenching route and its bioactivity was assessed by in vitro tests in a simulated body fluid (SBF). The glass was ground and sieved to obtain powders of specific size that were subsequently mixed with polyethylene particles of two different dimensions. The powders were then uniaxially pressed to obtain a crack free green compact that was thermally treated to remove the organic component and to sinter the inorganic phase. The obtained biomaterial was characterised by means of X-ray Diffraction, SEM equipped with EDS, mercury intrusion porosimetry, density measurements, image analysis, mechanical tests and in vitro evaluations. A glass-ceramic macroporous scaffold with a homogenously distributed and highly interconnected porosity was obtained. The amount and size of the introduced porosity could be tailored using various amounts of polyethylene powders of different size.     

Synthesis, neutralization and blocking procedures of organic/inorganic hybrid scaffolds for bone tissue engineering applications

Bioactive glasses (BaG) can bind to human bone tissues and have been used in many biomedical applications for the last 30 years. However they usually are weak and brittle. On the other hand, composites that combine polymers and BaG are of particular interest, since they often show an excellent balance between stiffness and toughness. Bioactive glass-poly(vinyl alcohol) foams to be used in tissue engineering applications were previously developed by our group, using the sol-gel route. Since bioactive glass-polymer composite derived from the sol-gel process cannot be submitted to thermal treatments at high temperatures (above 400 degrees C), they usually have unreacted species that can cause cytotoxicity. This work reports a technique for stabilizing the sol-gel derived bioactive glass/poly(vinyl alcohol) hybrids by using glutaraldehyde (GA), NH(4)OH solutions and a blocking solution containing bovine serum albumin. PVA/BaG/GA hybrids were characterized by Fourier Transform Infrared Spectroscopy (FTIR) and Scanning Electron Microscopy (SEM/EDX) analyses. Moreover, MTT (3-[4,5-dimethylthiazole-2-yl]-2,5-diphenyltetrazolium bromide) biocompatibility and cytotoxicity assays were also conducted. The hybrids exhibited pore size varying from 80 to 820 mum. After treatments, no major changes in the pore structure were observed and high levels of cell viability were obtained.     

壳聚糖支架在组织工程中的应用

综述了壳聚糖作为细胞生长载体在软骨组织工程，骨组织工程和皮肤组织工程等方面的应用进展，表明壳聚糖有望成为优异的组织工程支架材料。     

含Zn生物玻璃、玻璃陶瓷与聚酯复合骨组织工程支架的制备及性能

采用溶胶凝胶法在58S生物玻璃的基础上用氧化锌取代3? mol％的氧化钙制备了含锌的生物玻璃粉体 (58S3Z),对合成的粉体采用有机泡沫浸渍法在700℃及1200℃制备出58S3Z-700℃、58S3Z-1200℃玻璃及玻璃陶瓷多孔支架。在所得支架表面涂覆PLGA及PBS薄膜制备出58S3Z-1200℃-PLGA及58S3Z-1200℃-PBS复合支架。对其形貌、 孔隙率、 力学性能、 体外降解性及细胞相容性进行了系统研究。复合后多孔支架仍然保持三维连通的多孔结构,孔隙率与复合前(86.9%±0.8% (58S3Z-700℃),80.1%±0.6% (58S3Z-1200℃)）相比稍有下降,分别为75.9%±0.6% (58S3Z-1200℃-PLGA)和77.9%±0.9% (58S3Z-1200℃-PBS)。但复合多孔支架显示出较高的抗压强度,分别达到1509.4 kPa±162.8 kPa (PLGA) 和901.6 kPa±94.5 kPa (PBS),与玻璃和玻璃陶瓷支架 (258.4 kPa±23.6 kPa) 相比具有较大的提高。体外降解实验表明58S3Z-1200℃-PLGA、58S3Z-1200℃-PBS复合多孔支架可降解, 经过28天的浸泡其失重率分别达到13.3％和2.1％。体外研究结果表明:58S3Z玻璃陶瓷支架复合PBS或PLGA后支持成骨细胞黏附、铺展和生长。这种新型的复合支架具有三维的网状多孔结构,良好的力学性能、降解性和细胞相容性,有望成为一种较理想的骨组织工程支架。      

Tungsten disulfide nanoparticle-containing PCL and PLGA-coated bioactive glass composite scaffolds for bone tissue engineering applications

Journal of Materials Science - In the study, tungsten disulfide (WS2) nanoparticle-containing polymer-coated bioactive glass composite scaffolds were prepared for bone tissue engineering...     

Thermal-crosslinked porous chitosan scaffolds for soft tissue engineering applications

The aim of this study was to demonstrate the feasibility of using a steam autoclave process for sterilization and simultaneously thermal-crosslinking of lyophilized chitosan scaffolds. This process is of great interest in biomaterial development due to its simplicity and low toxicity. The steam autoclave process had no significant effect on the average pore diameter (~ 70 μm) and overall porosity (> 80%) of the resultant chitosan scaffolds, while the sterilized scaffolds possessed more homogenous pore size distribution. The sterilized chitosan scaffolds exhibited an enhanced compressive modulus (109.8 kPa) and comparable equilibrium swelling ratio (23.3). The resultant chitosan scaffolds could be used directly for in vitro cell culture without extra sterilization. The data of in vitro studies demonstrated that the scaffolds facilitated cell attachment and proliferation, indicating great potential for soft tissue engineering applications.     

Alginate based scaffolds for bone tissue engineering

The design and production of scaffolds for bone tissue regeneration is yet unable to completely reproduce the native bone properties. In the present study new alginate microparticle and microfiber aggregated scaffolds were produced to be applied in this area of regenerative medicine.The scaffolds' mechanical properties were characterized by thermo mechanical assays. Their morphological characteristics were evaluated by isothermal nitrogen adsorption and scanning electron microscopy. The density of both types of scaffolds was determined by helium pycnometry and mercury intrusion porosimetry. Furthermore, scaffolds' cytotoxic profiles were evaluated in vitro by seeding human osteoblast cells in their presence.The results obtained showed that scaffolds have good mechanical and morphological properties compatible with their application as bone substitutes. Moreover, scaffold's biocompatibility was confirmed by the observation of cell adhesion and proliferation after 5 days of being seeded in their presence and by non-radioactive assays.     

A modular and supramolecular approach to bioactive scaffolds for tissue engineering

Bioactive polymeric scaffolds are a prerequisite for the ultimate formation of functional tissues. Here, we show that supramolecular polymers based on quadruple hydrogen bonding ureido-pyrimidinone (UPy) moieties are eminently suitable for producing such bioactive materials owing to their low-temperature processability, favourable degradation and biocompatible behaviour. Particularly, the reversible nature of the hydrogen bonds allows for a modular approach to gaining control over cellular behaviour and activity both in vitro and in vivo. Bioactive materials are obtained by simply mixing UPy-functionalized polymers with UPy-modified biomolecules. Low-molecular-weight bis-UPy-oligocaprolactones with cell adhesion promoting UPy-Gly-Arg-Gly-Asp-Ser (UPy-GRGDS) and the synergistic UPy-Pro-His-Ser-Arg-Asn (UPy-PHSRN) peptide sequences are synthesized and studied. The in vitro results indicate strong and specific cell binding of fibroblasts to the UPy-functionalized bioactive materials containing both UPy-peptides. An even more striking effect is seen in vivo where the formation of single giant cells at the interface between bioactive material and tissue is triggered.     

Nanoindentation on porous bioceramic scaffolds for bone tissue engineering

We report nanoindentation mechanical properties measurements on porous ceramic scaffolds made for tissue engineering applications. The scaffolds have been made from tricalcium phosphate (TCP), hydroxyapatite (HA) nanopowder and mixed powders of HA (50 wt%) and TCP (50 wt%) using the polyurethane sponge method, which produces open porous ceramic scaffolds through replication of a porous polymer template. The scaffolds prepared by this method have a controllable pore size and interconnected pore structure. The crystal structures and morphology of porous scaffolds were determined by X-ray diffraction (XRD) and atomic force microscopy (AFM) respectively. Nanoindentation measurements to a depth of 600 nm showed a Young's modulus value of 10.3 GPa for HA+TCP composite scaffolds and 1.5 GPa for TCP scaffolds. The hardness values were 240 MPa for HA+TCP composites and 21 MPa for TCP sample respectively. The results showed that the mechanical properties of the biodegradable scaffolds can be considerably enhanced with the addition of HA while maintaining the interconnected open pores and pore geometry desirable for bone tissue engineering.     

Manufacture and evaluation of bioactive and biodegradable materials and scaffolds for tissue engineering

For tissue regeneration and tissue engineering applications, a number of bioactive and biodegradable composites, either porous or non-porous, were fabricated. The newly developed materials included tricalcium phosphate reinforced polyhydroxybutyrate and its copolymer, poorly crystallized hydroxyapatite reinforced chitin, and plasma sprayed hydroxyapatite reinforced poly(L-lactic acid). It was shown that these new materials could be successfully produced using the manufacturing techniques adopted. In vitro experiments revealed that the incorporation of bioceramic particles in biodegradable polymers rendered the composites bioactive and significantly improved the ability of composites to induce the formation of bone-like apatite on their surfaces. Degradation of composite scaffolds in simulated body fluid was observed and could be due to the simultaneous degradation of polymer matrix and dissolution of bioceramic particles.     

骨组织工程多孔支架材料性质及制备技术

多孔性生物可降解支架的选择和制备是组织工程技术成功运用的关键。从骨架的材料要求、常用的骨架材料、骨架的制备技术等几个方面对组织工程和生物降解支架的研究进行了综述 ,并对该研究的前景进行了展望     

Controlling the processing of collagen-hydroxyapatite scaffolds for bone tissue engineering

Scaffolds are an important aspect of the tissue engineering approach to tissue regeneration. This study shows that it is possible to manufacture scaffolds from type I collagen with or without hydroxyapatite (HA) by critical point drying. The mean pore sizes of the scaffolds can be altered from 44 to 135 μm depending on the precise processing conditions. Such pore sizes span the range that is likely to be required for specific cells. The mechanical properties of the scaffolds have been measured and behave as expected of foam structures. The degradation rate of the scaffolds by collagenase is independent of pore size. Dehydrothermal treatment (DHT), a common method of physically crosslinking collagen, was found to denature the collagen at a temperature of 120^∘C resulting in a decrease in the scaffold’s resistance to collagenase. Hybrid scaffold structures have also been manufactured, which have the potential to be used in the generation of multi-tissue interfaces. Microchannels are neatly incorporated via an indirect solid freeform fabrication (SFF) process, which could aid in reducing the different constraints commonly observed with other scaffolds.     

Effect of multiple unconfined compression on cellular dense collagen scaffolds for bone tissue engineering

Plastic compression of hydrated collagen gels rapidly produces biomimetic scaffolds of improved mechanical properties. These scaffolds can potentially be utilised as cell seeded systems for bone tissue engineering. This work investigated the influence of multiple unconfined compression on the biocompatibility and mechanical properties of such systems. Single and double compressed dense collagen matrices were produced and characterised for protein dry weight, morphology and mechanical strength. Compression related maintenance of the seeded HOS TE85 cell line viability in relation to the extent of compression was evaluated up to 10 days in culture using the TUNEL assay. Fluorescence Live/Dead assay was conducted to examine overall cell survival and morphology. Cell induced structural changes in the dense collagenous scaffolds were assessed by routine histology. The mechanical properties of the cellular scaffolds were also evaluated as a function of time in culture. It is clear that a single plastic compression step produced dense collagenous scaffolds capable of maintaining considerable cell viability and function as signs of matrix remodeling, and maintenance of mechanical properties were evident. Such scaffolds should therefore be further developed as systems for bone tissue regeneration.     

Processing and characterization of innovative scaffolds for bone tissue engineering

A new protocol, based on a modified replication method, is proposed to obtain bioactive glass scaffolds. The main feature of these samples, named "shell scaffolds", is their external surface that, like a compact and porous shell, provides both high permeability to fluids and mechanical support. In this work, two different scaffolds were prepared using the following slurry components: 59 % water, 29 % 45S5 Bioglass(?) and 12 % polyvinylic binder and 51 % water, 34 % 45S5 Bioglass(?), 10 % polyvinylic binder and 5 % polyethylene. All the proposed samples were characterized by a widespread microporosity and an interconnected macroporosity, with a total porosity of 80 % vol. After immersion in a simulated body fluid (SBF), the scaffolds showed strong ability to develop hydroxyapatite, enhanced by the high specific surface of the porous systems. Moreover preliminary biological evaluations suggested a promising role of the shell scaffolds for applications in bone tissue regeneration. As regards the mechanical behaviour, the shell scaffolds could be easily handled without damages, due to their resistant external surface. More specifically, they possessed suitable mechanical properties for bone regeneration, as proved by compression tests performed before and after immersion in SBF.     

Effect of surfactant concentration and composition on the structure and properties of sol-gel-derived bioactive glass foam scaffolds for tissue engineering

Bioactive glasses are known to have the ability to regenerate bone, and to release ionic biological stimuli that promote bone cell proliferation by gene activation, but their use has been restricted mainly to the form of powder, granules or small monoliths. Resorbable 3D macroporous bioactive scaffolds have been produced for tissue engineering applications by foaming sol-gel-derived bioactive glasses. The foams exhibit a hierarchical structure, with interconnected macropores (10–500 m), which provide the potential for tissue ingrowth and mesopores (2–50 nm), which enhance bioactivity and release of ionic products. The macroporous matrices were produced by the foaming of sol-gel glasses with the use of a surfactant. Three glass systems SiO₂, SiO₂-CaO and SiO₂-CaO-P₂O₅were foamed using various concentrations of surfactant, in order to investigate the effect of surfactant concentration and composition on the structure and properties of the hierarchical construct.     

Tuning polycaprolactone-carbon nanotube composites for bone tissue engineering scaffolds

This report describes the mechanical, thermal and biological characterisation of a solid free form microfabricated carbon nanotube-polycaprolactone composite, in which both the quantity of nanotubes in the matrix as well as the scaffold design were varied in order to tune the mechanical properties of the material. The creep and stress relaxation behaviour of the composite material was analysed to identify an optimal composition for bone tissue engineering. Moreover, the morphology and viability of osteoblast-like cells (MG63) on composite scaffolds were analysed using scanning electron microscopy and MTT assays. Our data demonstrate that by changing the ratio of CNT to PCL, the elastic modulus of the nanocomposite can be varied between 10 and 75 MPa. In this range, the geometry of the scaffold can be used to finely tune its stiffness. However our PCL-CNT nanocomposites were able to sustain osteoblast proliferation and modulate cell morphology. Thus we show the potential of custom designed CNT nanocomposites for bone tissue engineering.     

Nano-composite scaffolds for bone tissue engineering containing silver nanoparticles: preparation, characterization and biological properties

In this study nano-composite scaffolds to be used as bone grafts have been endowed with antibacterial properties owing to the presence of silver nanoparticles. The alginate/hydroxyapatite composite scaffolds were prepared by internal gelation followed by a freeze-drying procedure to obtain a porous structure. The nanoparticles were prepared in presence of a lactose modified-chitosan and this colloidal solution was adsorbed on the scaffolds by exploiting electrostatic interactions. The adsorption and release of the silver from the composite scaffold was measured by ICP-AES and spectrofluorimetry measurements. Micro-computed tomography analysis of the scaffolds showed a homogeneous porous structure with average pore sizes of 341.5 μm and porosity of 80 %. In vitro biological tests (MTS and killing kinetics assays) demonstrated that silver does not affect the ability of the scaffolds to promote osteoblasts proliferation and that at the same time it exerts a strong bactericidal effect against both Gram+ and Gram? bacterial strains. Overall, the combined results indicate that these biocompatible antimicrobial scaffolds possess ideal characteristics for tissue engineering applications.     

Preparation and characterization of macroporous chitosan/wollastonite composite scaffolds for tissue engineering

Chitosan/wollastonite composite scaffolds were prepared by a thermally induced phase separation method. The microstructure, mechanical performance and in vitro bioactivity of the composite scaffolds were investigated. The composite scaffolds were macroporous and wollastonite particles were dispersed uniformly on the surface of the pore walls. Scanning electron microscope images of the composite scaffolds demonstrated that the scaffolds had interconnected pores with diameters from 60 to 200 microm. Both the pore size and structure were affected by freezing temperature. The mechanical performance of the composite scaffolds was improved compared to that of pure chitosan scaffolds. The in vitro bioactivity of the scaffolds was evaluated by soaking samples in simulated body fluid and the apatite layer was observed on the surface of the pore walls of the composite scaffolds. Our results suggest that the incorporation of wollastonite into chitosan could enhance both the mechanical strength and the in vitro bioactivity of the resultant composite. The macroporous chitosan/wollastonite scaffolds may be a potential candidate for application in tissue engineering.