Fabrication and characterization of porous alginate/polyvinyl alcohol hybrid scaffolds for 3D cell culture

Porous alginate/polyvinyl alcohol (PVA) hybrid scaffolds as bioartificial cell scaffolds were fabricated to improve cell compatibility as well as flexibility of the scaffolds. The alginate/PVA hybrid scaffolds with different PVA compositions up to 50 wt% were fabricated by a modified freeze-drying method including the physical cross-linking of PVA and the following chemical cross-linking of alginate. The prepared alginate/PVA hybrid scaffolds were characterized by morphology observations using scanning electron microscopy (SEM), the measurements of porosity and average pore sizes and the measurements of compressive strength and modulus. The scaffolds exhibited highly porous, open-cellular pore structures with almost the same surface and cross-sectional porosities (total porosities about 85%, regardless of PVA composition) and the pore sizes from about 290 microm to about 190 microm with increasing PVA composition. The alginate/PVA hybrid scaffolds were more soft and elastic than the control alginate scaffold without significant changes of mechanical strength. The scaffolds were examined for their in vitro cell compatibility by the culture of chondrocytes (human chondrocyte cell line) in the scaffolds and the following analyses by MTT assay and SEM observation. It was observed that the alginate/PVA scaffolds had better cell adhesion and faster growth than the control alginate scaffold. It seems that 30 wt% addition of PVA to alginate in the fabrication of the hybrid scaffolds is desirable for improving their flexibility and cell compatibility.     

Preparation and properties of poly(lactide-co-glycolide) (PLGA)/ nano-hydroxyapatite (NHA) scaffolds by thermally induced phase separation and rabbit MSCs culture on scaffolds

Biodegradable polymer/bioceramic composites scaffold can overcome the limitation of conventional ceramic bone substitutes such as brittleness and difficulty in shaping. To better mimic the mineral component and the microstructure of natural bone, novel nano-hydroxyapatite (NHA)/polymer composite scaffolds with high porosity and well-controlled pore architectures as well as high exposure of the bioactive ceramics to the scaffold surface is developed for efficient bone tissue engineering. In this article, regular and highly interconnected porous poly(lactide-co-glycolide) (PLGA)/NHA scaffolds are fabricated by thermally induced phase separation technique. The effects of solvent composition, polymer concentration, coarsening temperature, and coarsening time as well as NHA content on the micro-morphology, mechanical properties of the PLGA/NHA scaffolds are investigated. The results show that pore size of the PLGA/NHA scaffolds decrease with the increase of PLGA concentration and NHA content. The introduction of NHA greatly increase the mechanical properties and water absorption ability which greatly increase with the increase of NHA content. Mesenchymal stem cells are seeded and cultured in three-dimensional (3D) PLGA/NHA scaffolds to fabricate in vitro tissue engineering bone, which is investigated by adhesion rate, cell morphology, cell numbers, and alkaline phosphatase assay. The results display that the PLGA/NHA scaffolds exhibit significantly higher cell growth, alkaline phosphatase activity than PLGA scaffolds, especially the PLGA/NHA scaffolds with 10 wt.% NHA. The results suggest that the newly developed PLGA/NHA composite scaffolds may serve as an excellent 3D substrate for cell attachment and migration in bone tissue engineering.     

Alginate/poly (lactic-co-glycolic acid)/calcium phosphate cement scaffold with oriented pore structure for bone tissue engineering

In this study, the alginate/calcium phosphate cement (CPC) scaffolds with oriented pore structure were fabricated by unidirectional freeze casting and poly (lactic-co-glycolic acid) (PLGA) was used to infiltrate into the macropores to strengthen the scaffolds. By modifying the liquid to powder ratio, the porosity and pore size of the alginate/CPC scaffold could be controlled. At the liquid to powder (L/P) ratio of 3.25, scaffolds possessing open directional macropores and a total porosity of 89.24% could be achieved. The size of the tubule-like macropores could reach 100-200 mum in their radial dimension and more than 1000 mum in the axial one, with macropores well-regulated arrayed. Increasing the L/P ratio would significantly decrease the mechanical strength of alginate/CPC scaffolds. The compressive strength and toughness of scaffolds could be greatly improved via PLGA reinforcement. Three mechanisms of PLGA reinforcement ran as follows: participating in the external load, strengthening the matrix, and patching the defects of CPC pores wall. Alginate/PLGA/CPC scaffold preserved the open directional macropores and might be a potential scaffold for bone tissue engineering.     

聚乳酸-羟基乙酸共聚物/硅酸钙三维多孔骨组织工程支架的构建与性能

BACKGROUND: Some disadvantages exsist in commonly used poly(lactic-co-glycolic acid) (PLGA) scaffolds, including acidic degradation products, suboptimal mechanical properties, low pore size, poor porosity and pore connectivity rate and uncontrollable shape. OBJECTIVE: To construct a scaffold with three-dimensional (3D) pores by adding calcium silicate to improve the properties of PLGA, and then detect its degradability, mechanical properties and biocompatibility. METHODS: PLGA/calcium silicate porous composite microspheres were prepared by the emulsion-solvent evaporation method, and PLGA 3D porous scaffold was established by 3D-Bioplotter, and then PLGA/calcium silicate composite porous scaffolds were constructed by combining the microspheres with the scaffold using low temperature fusion technology. The compositions, morphology and degradability of the PLGA/calcium silicate porous composite microspheres and PLGA microspheres, as well as the morphology, pore properties and compression strength of the PLGA 3D scaffolds and PLGA/calcium silicate composite porous scaffolds were measured, respectively. Mouse bone marrow mesenchymal stem cells were respectively cultivated in the extracts of PLGA/calcium silicate porous composite microspheres and PLGA microspheres, and then were respectively seeded onto the PLGA 3D scaffolds and PLGA/calcium silicate composite porous scaffolds. Thereafter, the cell proliferation activity was detected at 1, 3 and 5 days. RESULTS AND CONCLUSION: Regular pores on the PLGA microspheres and internal cavities were formed, and the PH values of the degradation products were improved after adding calcium silicate. The fiber diameter, pore, porosity and average pore size of the composite porous scaffolds were all smaller than those of the PLGA scaffolds. The compression strength and elasticity modulus of the composite porous scaffolds were both higher than those of the PLGA scaffolds (P < 0.05). Bone marrow mesenchymal stem cells grew well in above microsphere extracts and scaffolds. These results indicate that PLGA/calcium silicate composite porous scaffolds exhibit good degradability in vitro, mechanical properties and biocompatibility.     

Biocompatibility of electrospun halloysite nanotube-doped poly(lactic-co-glycolic acid) composite nanofibers

Organic/inorganic hybrid nanofiber systems have generated great interest in the area of tissue engineering and drug delivery. In this study, halloysite nanotube (HNT)-doped poly(lactic-co-glycolic acid) (PLGA) composite nanofibers were fabricated via electrospinning and the influence of the incorporation of HNTs within PLGA nanofibers on their in vitro biocompatibility was investigated. The morphology, mechanical and thermal properties of the composite nanofibers were characterized by scanning electron microscopy (SEM), tensile test, differential scanning calorimetry and thermogravimetric analysis. The adhesion and proliferation of mouse fibroblast cells cultured on both PLGA and HNT-doped PLGA fibrous scaffolds were compared through 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide assay of cell viability and SEM observation of cell morphology. We show that the morphology of the PLGA nanofibers does not appreciably change with the incorporation of HNTs, except that the mean diameter of the fibers increased with the increase of HNT incorporation in the composite. More importantly, the mechanical properties of the nanofibers were greatly improved. Similar to electrospun PLGA nanofibers, HNT-doped PLGA nanofibers were able to promote cell attachment and proliferation, suggesting that the incorporation of HNTs within PLGA nanofibers does not compromise the biocompatibility of the PLGA nanofibers. In addition, we show that HNT-doped PLGA scaffolds allow more protein adsorption than those without HNTs, which may provide sufficient nutrition for cell growth and proliferation. The developed electrospun HNT-doped composite fibrous scaffold may find applications in tissue engineering and pharmaceutical sciences.     

Control of degradation rate and hydrophilicity in electrospun non-woven poly(D,L-lactide) nanofiber scaffolds for biomedical applications

Typical properties of poly(D,L-lactide) (PLA)-based scaffolds (films and foams), such as long degradation time, mechanical stiffness and hydrophobicity, are sometimes not suitable for biomedical applications. These properties can be substantially altered by electrospinning of PLA blends with miscible poly(lactide-co-glycolide) (PLGA) random copolymers, poly(lactide-b-ethylene glycol-b-lactide) (PLA-b-PEG-b-PLA) triblock copolymers, and a lactide (used as a hydrolytic catalyst). Electrospun scaffolds based on the multi-component PLA blends, comprised of randomly interconnected webs of sub-micron sized fibers, have a bulk density of 0.3-0.4 g/cm3. In this study, the concentration effects of PLA-b-PEG-b-PLA triblock copolymer and lactide on the cell proliferation and the hydrophilicity of electrospun scaffolds were investigated. Based on in vitro degradation study, we found that the electrospun scaffold having PLA (40 wt%), PLGA (LA/GA=50/50, 25 wt%), PLA-b-PEG-b-PLA (20 wt%), and lactide (15 wt%) underwent a rapid weight loss of approximately 65% in 7 weeks. The hydrophobicity of this membrane, as determined by contact angle measurements in a cell buffer solution, decreased by approximately 50% from 105 degrees (of an electrospun PLA scaffold) to 50 degrees. The selection of suitable chemical compositions in conjunction with the non-invasive electrospinning process is useful in the production of a new kind of biodegradable scaffolds suitable for different biomedical applications such as cell storage and delivery as well as prevention of post-surgical adhesion because of their porosity, mechanical flexibility and tunable biodegradability.     

Property of Polyvinyl Alcohol-Calcium Alginate as Composite Scaffolds for Tissue Engineering

Objective:A novel PVA-CaAIg composite material by polyvinyl alcohol (PVA) and sodium alginate(SA) was fabricated to investigate the feasibility serving as a scaffold for tissue engineering and to find out the most ideal proportion according to their properties.Methods: Film,graininess and sponge scaffolds of PVA-CaAlg were fabricated by three different methods.Water content and swelling ratio were tested.SEM was used to observe the configuration of the cross section.Results:Different proportional scaffolds could be obtained with different PVA molecular weight,alcoholysis degree and different SA dosages.The water content of different scaffolds ranged from 48% to 93% and showed different inner configuration with swelling ratio between 120% and 470%.SEM proved that different composite materials had different porous structures.Conclusion:A scaffold for tissue engineering with high water content and proper swelling ratio can be fabricated using PVA and SA.The porous structure shows potential in tissue engineering and cell culture.     

Polyurethane/poly(lactic-co-glycolic) acid composite scaffolds fabricated by thermally induced phase separation

In this study, we present a novel composite scaffold fabricated using a thermally induced phase separation (TIPS) process from poly(lactic-co-glycolic) (PLGA) and biomedical polyurethane (PU). This processing method has been tuned to allow intimate (molecular) mixing of these two very different polymers, giving rise to a unique morphology that can be manipulated by controlling the phase separation behaviour of an initially homogenous polymer solution. Pure PLGA scaffolds possessed a smooth, directional fibrous sheet-like structure with pore sizes of 0.1-200mum, a porous Young's modulus of 93.5kPa and were relatively brittle to touch. Pure PU scaffolds had an isotropic emulsion-like structure, a porous Young's modulus of 15.7kPa and were much more elastic than the PLGA scaffolds. The composite PLGA/PU scaffold exhibits advantageous morphological, mechanical and cell adhesion and growth supporting properties, when compared with scaffolds fabricated from PLGA or PU alone. This novel method provides a mechanism for the formation of tailored bioactive scaffolds from nominally incompatible polymers, representing a significant step forward in scaffold processing for tissue-engineering applications.     

Hydrophilized 3D porous scaffold for effective plasmid DNA delivery

In this study, hydrophilic PLGA/Pluronic F127 scaffolds loaded with a pDNA/PEI-PEG complex were prepared to estimate their potential use as a polymeric matrix for pDNA delivery. The scaffold was fabricated by a novel precipitation/particulate leaching method. The prepared pDNA/PEI-PEG complex-loaded PLGA/Pluronic F127 scaffold exhibited a highly porous (porosity, 93-95%) and open pore structure, as well as hydrophilicity, which can provide the good environment for cell adhesion and growth. The pDNA/PEI-PEG complexes were efficiently loaded into the PLGA/Pluronic F127 scaffold and continuously released from the scaffolds up to ~90% of the initial loading amount over a period of 8 wk, which may lead to continuous gene transfection into human bone marrow mesenchymal stem cells (hBMMSCs). From the in vitro cell culture in the scaffolds for transfection, it was observed that the pDNA/PEI-PEG complex-loaded hydrophilic PLGA/Pluronic F127 scaffold has a higher transfection efficiency of the pDNA/PEI-PEG complexes into hBMMSCs than the hydrophobic PLGA ones. The cell viability associated with the pDNA/PEI-PEG complexes released from the PLGA/Pluronic F127 scaffold was not significantly different from that of the PLGA/Pluronic F127 scaffold without pDNA, indicating its low cytotoxicity, probably due to the sustained release of the pDNA/PEI-PEG complex from the scaffolds. From these results, we could suggest that the pDNA/PEI-PEG complex-loaded hydrophilic PLGA/Pluronic F127 scaffold can be an effective gene delivery system for 3D tissue formation.     

Macroporous biodegradable natural/synthetic hybrid scaffolds as small intestine submucosa impregnated poly(D,L-lactide-co-glycolide) for tissue-engineered bone

Poly(D,L-lactide-co-glycolide) (PLGA), a biodegradable synthetic polymer, is widely used in a variety of tissue-engineered applications, including drug-delivery systems. However, the PLGA scaffolds, macroporous and three-dimensional structure, are difficult to cell attachment and in-growth due to surface hydrophobicity. In order to introduce in new bioactive functionality from porcine small intestine submucosa (SIS) as natural source for PLGA, we fabricated SIS-powder-impregnated PLGA (SIS/PLGA) hybrid scaffolds. Fabrication parameters, including ratios of SIS, PLGA and salt, were optimized to produce the desired macroporous foam. The scaffolds had a relatively homogeneous pore structure, good interconnected pores from the surface to core region and showed an average pore size in the range 69.23-105.82 microm and over 90% porosity. The SIS/PLGA scaffolds degraded with a rate depending on the contents of the SIS. After the fabrication of the SIS/PLGA hybrid scaffolds the wettability of the scaffold was greatly enhanced, resulting in uniform cell seeding and distribution. So, it was observed that BMSC attachment to the SIS/PLGA scaffolds increased gradually with increasing SIS contents. Scaffolds of PLGA alone and SIS/PLGA were implanted subcutaneously under dorsal skin of athymic nude mouse to observe the osteoconductivity. It was found from the result that the effects of the SIS/PLGA scaffolds on bone formation are stronger than control PLGA scaffolds. In summary, the SIS/PLGA scaffolds have osteoconductive effects to allow remodeling and replacement by osseous tissue.     

Evaluation of functions and tissue compatibility of poly (D,L-lactic-co-glycolic acid) seeded with human dermal fibroblasts

In tissue engineering and wound-healing applications, dermal substitutes are used to provide fibroblasts with the mechanical support for their growth and then to facilitate the skin formation. In this study, three-dimensional porous poly(lactic-co-glycolic acid) (PLGA) 65/35 scaffolds were prepared and then the composites of the scaffolds and human fetal dermal fibroblasts were fabricated as a tissue-engineered dermal substitute. The function and tissue compatibility of the artificial dermal substitute were evaluated at the levels of gene expression (by RT-PCR) and protein expression (total collagen quantities), as well as by histological and immunohistochemical analysis. The PCR products indicated that the mRNA of type-I collagen, mainly secreted by the fibroblasts onto the PLGA scaffolds, was clearly expressed after 4 weeks. The amount of total collagen synthesized from the cells was shown to increase gradually during the initial culture period and slightly decreased afterwards. After 8 weeks of culture, the fibroblasts were well attached and migrated entirely throughout the pores of the PLGA scaffold with normal function. Furthermore, the positively stained type-I collagen was intensively detected throughout the pores. These results suggest that the function and tissue compatibility may be important criteria in evaluating an artificial tissue-engineered skin.     

Effect of demineralized bone particle/poly(lactic-co-glycolic acid) scaffolds on the attachment and proliferation of mesenchymal stem cells

The aim of this study was to investigate the effect of demineralized bone particle/ poly(lactic-co-glycolic acid) (DBP/PLGA) scaffolds on the proliferation of mesenchymal stem cells (MSCs). DBP/PLGA hybrid scaffolds were fabricated by solvent casting/salt-leaching with DBP contents of 0, 20, 40, and 80 wt%. MSCs were seeded on the DBP/PLGA scaffolds and then evaluated by a series of analytical process: SEM, MTT, RT-PCR, and in vivo histological assay. As the DBP contents increased, the cell attachment behavior and cell viability also increased. A DBP content of 80 wt% marked the best water absorption performance and the highest cell viability. Gene expression of aggrecan on DBP/PLGA scaffolds tended to increase, whereas that on PLGA scaffolds was decreased at 1 week. However, strong expression of aggrecan was observed at 2 weeks regardless of the contents of DBP. Scaffolds showed a trend of increasing type II and I collagen at 2 weeks. The results showed that MSCs on DBP/PLGA scaffolds showed more efficient cell proliferation and tissue formation in the presence of tissue-inductive stimuli. Suitable biomaterials could be more conducive to proliferation of MSCs. These results suggest that the DBP/PLGA scaffolds are a feasible biomaterial for intervertebral disc regeneration.     

Evaluation of functions and tissue compatibility of poly (D,L-lactic-co-glycolic acid) seeded with human dermal fibroblasts

In tissue engineering and wound-healing applications, dermal substitutes are used to provide fibroblasts with the mechanical support for their growth and then to facilitate the skin formation. In this study, three-dimensional porous poly(lactic-co-glycolic acid) (PLGA) 65/35 scaffolds were prepared and then the composites of the scaffolds and human fetal dermal fibroblasts were fabricated as a tissue-engineered dermal substitute. The function and tissue compatibility of the artificial dermal substitute were evaluated at the levels of gene expression (by RT-PCR) and protein expression (total collagen quantities), as well as by histological and immunohistochemical analysis. The PCR products indicated that the mRNA of type-I collagen, mainly secreted by the fibroblasts onto the PLGA scaffolds, was clearly expressed after 4 weeks. The amount of total collagen synthesized from the cells was shown to increase gradually during the initial culture period and slightly decreased afterwards. After 8 weeks of culture, the fibroblasts were well attached and migrated entirely throughout the pores of the PLGA scaffold with normal function. Furthermore, the positively stained type-I collagen was intensively detected throughout the pores. These results suggest that the function and tissue compatibility may be important criteria in evaluating an artificial tissue-engineered skin.     

Macroporous biodegradable natural/synthetic hybrid scaffolds as small intestine submucosa impregnated poly(D,L-lactide-co-glycolide) for tissue-engineered bone

—Poly( D , L-lactide-co-glycolide) (PLGA), a biodegradable synthetic polymer, is widely used in a variety of tissue-engineered applications, including drug-delivery systems. However, the PLGA scaffolds, macroporous and three-dimensional structure, are difficult to cell attachment and in-growth due to surface hydrophobicity. In order to introduce in new bioactive functionality from porcine small intestine submucosa (SIS) as natural source for PLGA, we fabricated SIS-powder-impregnated PLGA (SIS/PLGA) hybrid scaffolds. Fabrication parameters, including ratios of SIS, PLGA and salt, were optimized to produce the desired macroporous foam. The scaffolds had a relatively homogeneous pore structure, good interconnected pores from the surface to core region and showed an average pore size in the range 69.23–105.82 μm and over 90% porosity. The SIS/PLGA scaffolds degraded with a rate depending on the contents of the SIS. After the fabrication of the SIS/PLGA hybrid scaffolds the wettability of the scaffold was greatly enhanced, resulting in uniform cell seeding and distribution. So, it was observed that BMSC attachment to the SIS/PLGA scaffolds increased gradually with increasing SIS contents. Scaffolds of PLGA alone and SIS/PLGA were implanted subcutaneously under dorsal skin of athymic nude mouse to observe the osteoconductivity. It was found from the result that the effects of the SIS/PLGA scaffolds on bone formation are stronger than control PLGA scaffolds. In summary, the SIS/PLGA scaffolds have osteoconductive effects to allow remodeling and replacement by osseous tissue.     

In vitro characterization of hepatocyte growth factor release from PHBV/PLGA microsphere scaffold

Polymer scaffolds which can support cells to grow as well as deliver growth factors to the cells simultaneously have great potential for the successful regeneration of failed tissues. As popularly used vehicles to deliver anti-cancer drugs and growth factors, microspheres also show many advantages as substrates to guide the growth of cells. Therefore, we aimed to examine the feasibility of using microspheres as ideal scaffolds for liver tissue engineering. To determine the capabilities of previously used microsphere scaffold to deliver growth factors simultaneously, this work investigated a long-term (about three months) release of bovine serum albumin (BSA) from microsphere scaffolds fabricated by using two different polymers, poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV, 8% PHV), poly(lactide-co-glycolide) acid (PLGA, 5050) and a blend of PLGA and PHBV. BSA served as a model for hepatocyte growth factor (HGF) since both proteins have similar molecular weights and hydrophilicity. Furthermore, HGF was encapsulated into the PLGA/PHBV composite microsphere with a core-shell structure, and sustained delivery of HGF with maintained bioactivity was achieved for at least 40 days. The moderate degradation rate (about 55% loss of the initial mass) and well-preserved structure after three months of incubation indicated that the PLGA/PHBV composite microspheres would therefore be more suitable than the pure PHBV or PLGA microspheres as a scaffold for engineering liver tissue.     

Pores Created by Laser Surface Modification of Poly(vinylalcohol)-Collagen with Glycosaminoglycan Scaffold for Cell Culture in Tissue Engineering

A PVA-GAG-COL composite scaffold is fabricated by polyvinyl alcohol (PVA),glycosaminoglycan (GAG) and collagen (COL).Laser surface modification technology is used to make holes on the surface of the sc...     

Elastic biodegradable poly(glycolide-co-caprolactone) scaffold for tissue engineering

Cyclic mechanical strain has been demonstrated to enhance the development and function of engineered smooth muscle (SM) tissues, and it would be necessary for the development of the elastic scaffolds if one wishes to engineer SM tissues under cyclic mechanical loading. This study reports on the development of an elastic scaffold fabricated from a biodegradable polymer. Biodegradable poly(glycolide-co-caprolactone) (PGCL) copolymer was synthesized from glycolide and epsilon-caprolactone in the presence of stannous octoate as catalyst. The copolymer was characterized by (1)H-NMR, gel permeation chromatography and differential scanning calorimetry. Scaffolds for tissue engineering applications were fabricated from PGCL copolymer using the solvent-casting and particle-leaching technique. The PGCL scaffolds produced in this fashion had open pore structures (average pore size = 250 microm) without the usual nonporous skin layer on external surfaces. Mechanical testing revealed that PGCL scaffolds were far more elastic than poly(lactic-co-glycolic acid) (PLGA) scaffolds fabricated using the same method. Tensile mechanical tests indicated that PGCL scaffolds could withstand an extension of 250% without cracking, which was much higher than withstood by PLGA scaffolds (10-15%). In addition, PGCL scaffolds achieved recoveries exceeding 96% at applied extensions of up to 230%, whereas PLGA scaffolds failed (cracked) at an applied strain of 20%. Dynamic mechanical tests showed that the permanent deformation of the PGCL scaffolds in a dry condition produced was less than 4% of the applied strain, when an elongation of 20% at a frequency of 1 Hz (1 cycle per second) was applied for 6 days. Moreover, PGCL scaffolds in a buffer solution also had permanent deformations less than 5% of the applied strain when an elongation of 10% at a frequency of 1 Hz was applied for 2 days. The usefulness of the PGCL scaffolds was demonstrated by engineering SM tissues in vivo. This study shows that the elastic PGCL scaffolds produced in this study could be used to engineer SM-containing tissues (e.g. blood vessels and bladders) in mechanically dynamic environments.     

胶原复合梯度磷酸三钙负载软骨细胞的体外培养

目的 观察新型三维支架材料胶原复合梯度磷酸三钙在体外与软骨细胞的相容性和黏附性,评价其作为软骨组织工程支架的可行性.方法 取8周龄新两兰大白兔膝关节软骨,以酶消化法获得高纯度软骨细胞,培养3代后与三维支架材料胶原复合梯度磷酸三钙在体外复合培养.用倒置相差显微镜、HE染色、免疫组织化学及扫描电镜观察软骨细胞形态、Ⅱ型胶原表达及成软骨能力,同时观察支架材料与软骨细胞的相容性.结果 扫描电镜观察显示支架材料具有疏松多孔结构,孔隙结构规则,孔径100～150 μm,材料内部孔与孔之间贯通良好.支架亲水性好.软骨细胞吸附于支架表面,增殖并逐渐顺孔隙迁徙至支架内部,在孔壁贴附良好,表型维持稳定,可分泌细胞外基质.结论 胶原复合梯度磷酸三钙三维支架具有良好的细胞相容性.     

A novel strontium-doped calcium polyphosphate/erythromycin/poly(vinyl alcohol) composite for bone tissue engineering

It is our goal to develop bactericidal bone scaffolds with osteointegration potential. In this study, poly(vinyl alcohol) (PVA) coating (7%) was applied to an erythromycin (EM)-impregnated strontium-doped calcium polyphosphate (SCPP) scaffold using a simple slurry dipping method. MicroCT analysis showed that PVA coating reduced the average pore size and the percentage of pore interconnectivity to some extent. Compressive strength tests confirmed that the PVA coating significantly increased material elasticity and slightly enhanced the scaffold mechanical strength. It was also confirmed that the PVA coatings allowed a sustained EM release that is controlled by diffusion through the intact PVA hydrogel layer, irrespective of the drug solubility. PVA coating did not inhibit the EM bioactivity when the scaffolds were immersed in simulated body fluid for up to 4 weeks. EM released from SCPP-EM-PVA composite scaffolds maintained its capability of bacterial growth (S. aureus) inhibition. PVA coating is biocompatible and nontoxic to MC3T3 preosteoblast cells. Furthermore, we found that SCPP-EM-PVA composite scaffolds and their eluants remarkably inhibited RANKL-induced osteoclastogenesis in a murine RAW 264.7 macrophage cell line. Thus, this unique multifunctional bioactive composite scaffold has the potential to provide controlled delivery of relevant drugs for bone tissue engineering.     

Development of biodegradable poly(propylene fumarate)/poly(lactic-co-glycolic acid) blend microspheres. I. Preparation and characterization

We developed poly(propylene fumarate)/poly(lactic-co-glycolic acid) (PPF/PLGA) blend microspheres and investigated the effects of various processing parameters on the characteristics of these microspheres. The advantage of these blend microspheres is that the carbon-carbon double bonds along the PPF backbone could be used for their immobilization in a PPF scaffold. Microspheres containing the model drug Texas red dextran were fabricated using a double emulsion-solvent extraction technique. The effects of the following six processing parameters on the microsphere characteristics were investigated: PPF/PLGA ratio, polymer viscosity, vortex speed during emulsification, amount of internal aqueous phase, use of poly(vinyl alcohol) (PVA) in the internal aqueous phase, and PVA concentration in the external aqueous phase. Our results showed that the microsphere surface morphology was affected most by the viscosity of the polymer solution. Microspheres fabricated with a kinematic viscosity of 39 centistokes had a smooth, nonporous surface. In most microsphere formulations, the model drug was dispersed uniformly in the polymer matrix. For all fabricated formulations, the average microsphere diameter ranged between 19.0 and 76.9 microm. The external PVA concentration and vortex speed had most effect on the size distribution. Entrapment efficiencies varied from 60 to 98% and were most affected by the amount of internal aqueous phase, vortex speed, and polymer viscosity. Overall, we demonstrated the ability to fabricate PPF/PLGA blend microspheres with similar surface morphology, entrapment efficiency, and size distribution as conventional PLGA microspheres.