Functionalized PLGA-doped zirconium oxide ceramics for bone tissue regeneration

Bone tissue engineering is an alternative approach to bone grafts. In our study we aim to develop a composite scaffold for bone regeneration made of doped zirconium oxide (ZrO₂) conjugated with poly(lactic-co-glycolic acid) (PLGA) particles for the delivery of growth factors. In this composite, the PLGA microspheres are designed to release a crucial growth factor for bone formation, bone morphogenetic protein-2 (BMP2). We found that by changing the polymer’s molecular weight and composition, we could control microsphere loading, release and size. The BMP2 released from PLGA microspheres retained its biological activity and increased osteoblastic marker expression in human mesenchymal stem cells (hMSCs). Uncapped PLGA microspheres were conjugated to ZrO₂ scaffolds using carbodiimide chemistry, and the composite scaffold was shown to support hMSCs growth. We also demonstrated that human umbilical vein endothelial cells (HUVECs) can be co-cultured with hMSCs on the ZrO₂ scaffold for future vascularization of the scaffold. The ZrO₂ composite scaffold could serve as a bone substitute for bone grafting applications with the added ability of releasing different growth factors needed for bone regeneration.     

Modulation of protein delivery from modular polymer scaffolds

Growth factors are increasingly employed to promote tissue regeneration with various biomaterial scaffolds. In vitro release kinetics of protein growth factors from tissue engineering scaffolds are often investigated in aqueous environment, which is significantly different from in vivo environment. This study investigates the release of model proteins with net-positive (histone) and net-negative charge (bovine serum albumin, BSA) from various scaffolding surfaces and from encapsulated microspheres in the presence of ions, proteins, and cells. The release kinetics of proteins in media with varying concentrations of ions (NaCl) suggests stronger electrostatic interaction between the positively charged histone with the negatively charged substrates. While both proteins released slowly from hydrophobic PCL surfaces, plasma etching resulted in rapid release of BSA, but not histone. Interestingly, although negatively charged BSA released readily from negatively charged collagen (col), BSA released slowly from col-coated PCL scaffolds. Such electrostatic interaction effects were abolished in the presence of serum proteins and cells as evidenced by the rapid release of proteins from col-coated scaffolds. To achieve sustained release in the complex environment of serum proteins and cells, the model proteins were encapsulated into poly(D,L-lactic-co-glycolic acid) (PLGA) microspheres, which were embedded within col-coated PCL scaffolds. Protein release from microspheres was modulated by changing the lactide-to-glycolide ratio of PLGA polymer. BSA adsorbed to col released faster than histone encapsulated in microspheres in the presence of serum and cells. Collectively, the data suggest that growth factor release is highly influenced by scaffold surface and the presence of ions, proteins, and cells in the media. Strategies to deliver multiple growth factors and studies which investigate their release should consider these important variables.     

Controlled drug release from a novel injectable biodegradable microsphere/scaffold composite based on poly(propylene fumarate)

The ideal biomaterial for the repair of bone defects is expected to have good mechanical properties, be fabricated easily into a desired shape, support cell attachment, allow controlled release of bioactive factors to induce bone formation, and biodegrade into nontoxic products to permit natural bone formation and remodeling. The synthetic polymer poly(propylene fumarate) (PPF) holds great promise as such a biomaterial. In previous work we developed poly(DL-lactic-co-glycolic acid) (PLGA) and PPF microspheres for the controlled delivery of bioactive molecules. This study presents an approach to incorporate these microspheres into an injectable, porous PPF scaffold. Model drug Texas red dextran (TRD) was encapsulated into biodegradable PLGA and PPF microspheres at 2 microg/mg microsphere. Five porous composite formulations were fabricated via a gas foaming technique by combining the injectable PPF paste with the PLGA or PPF microspheres at 100 or 250 mg microsphere per composite formulation, or a control aqueous TRD solution (200 microg per composite). All scaffolds had an interconnected pore network with an average porosity of 64.8 +/- 3.6%. The presence of microspheres in the composite scaffolds was confirmed by scanning electron microscopy and confocal microscopy. The composite scaffolds exhibited a sustained release of the model drug for at least 28 days and had minimal burst release during the initial phase of release, as compared to drug release from microspheres alone. The compressive moduli of the scaffolds were between 2.4 and 26.2 MPa after fabrication, and between 14.9 and 62.8 MPa after 28 days in PBS. The scaffolds containing PPF microspheres exhibited a significantly higher initial compressive modulus than those containing PLGA microspheres. Increasing the amount of microspheres in the composites was found to significantly decrease the initial compressive modulus. The novel injectable PPF-based microsphere/scaffold composites developed in this study are promising to serve as vehicles for controlled drug delivery 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.     

Novel scaffolds fabricated from protein-loaded microspheres for tissue engineering

Biodegradable scaffolds play an important role in tissue engineering by providing physical and biochemical support for both differentiated and progenitor cells. Here, we describe a novel method for incorporating proteins in 3D biodegradable scaffolds by utilizing protein-loaded microspheres as the building blocks for scaffold formation. Poly(l,d-lactic-co-glycolic acid) (PLGA) microspheres containing bovine serum albumin (BSA) were fused into scaffolds using dichloromethane vapor for various time intervals. Microspheres containing 0, 0.4, 1.5, 4.3% BSA showed that increased protein loading required increased fusion time for scaffold fabrication. Protein release from the scaffolds was quantified in vitro over 20 days and compared to that of loose microspheres. Scaffolds had a slightly lower (up to 20%) release over the first 10 days, however, the cumulative release from both microspheres and scaffolds at the end of the study was not statistically different and the rate of release was the same, indicating that microsphere release can be predictive of scaffold kinetics. Scaffolds fused from larger (113.3 +/- 58.0 microm) rather than smaller (11.15 +/- 11.08 microm) microspheres, generated pores on the order of 200 microm as compared to 20 microm, respectively, showing control over pore size. In addition, four dyes (carbon black, acid green, red 27, and fast green FCF) were encapsulated in PLGA microspheres and fused into homogeneous and partitioned scaffolds, indicating control over spatial distribution within the scaffold. Finally, the scaffolds were seeded with fibroblast cells, which attached and were well spread over the polymer surface after 4h of incubation. These results highlight the versatility of this simple scaffold fusion method for incorporating essentially any combination of loaded microspheres into a 3D structure, making this a powerful tool for tissue engineering and drug delivery applications.     

Apatite-coated poly(lactic-co-glycolic acid) microspheres as an injectable scaffold for bone tissue engineering

Biodegradable polymer/ceramic composite scaffold could overcome limitations of biodegradable polymers or ceramics for bone regeneration. Injectable scaffold has raised great interest for bone regeneration in vivo, since it allows one for easy filling of irregularly shaped bone defects and implantation of osteogenic cells through minimally invasive surgical procedures The purpose of this study was to determine whether apatite-coated poly(lactic-co-glycolic acid) (PLGA) microspheres could be used as an injectable scaffold to regenerate bone in vivo. Apatite-coated PLGA microspheres were fabricated by incubating PLGA microspheres in simulated body fluid. The apatite that coated the PLGA microsphere surfaces was similar to apatite in natural bone, as demonstrated by scanning electron microscopy, X-ray diffraction spectra, energy-dispersive spectroscopy, and Fourier transformed-infrared spectroscopy analyses. Rat osteoblasts were mixed with apatite-coated PLGA microspheres and injected immediately into subcutaneous sites of athymic mice. Osteoblast transplantation with plain PLGA microspheres served as a control. Histological analysis of the implants at 6 weeks with hematoxylin and eosin staining, Masson's trichrome staining, and von Kossa staining revealed much better regeneration of bone in the apatite-coated PLGA microsphere group than the plain PLGA microsphere group. The new bone formation area and the calcium content of the implants were significantly higher in the apatite-coated PLGA microsphere group than in the plain PLGA microsphere group. This study demonstrates the feasibility of using apatite-coated PLGA microspheres as an injectable scaffold for in vivo bone tissue engineering. This scaffold may be useful for bone regeneration through minimally invasive surgical procedures in orthopedic applications.     

Novel mesoporous silica-based antibiotic releasing scaffold for bone repair

Tissue engineering scaffolds with a micro- or nanoporous structure and able to deliver special drugs have already been confirmed to be effective in bone repair. In this paper, we first evaluated the biomineralization properties and drug release properties of a novel mesoporous silica–hydroxyapatite composite material (HMS–HA) which was used as drug vehicle and filler for polymer matrices. Biomineralization can offer a credible prediction of bioactivity for the synthetic bone regeneration materials. We found HMS–HA exhibited good apatite deposition properties after being soaked in simulated body fluid (SBF) for 7 days. Drug delivery from HMS–HA particle was in line with Fick’s law, and the release process lasted 12 h after an initial burst release with 60% drug release. A novel tissue engineering scaffold with the function of controlled drug delivery was developed, which was based on HMS–HA particles, poly(lactide-co-glycolide) (PLGA) and microspheres sintering techniques. Mechanical testing on compression, degradation behavior, pH-compensation effect and drug delivery behavior of PLGA/HMS–HA microspheres sintered scaffolds were analyzed. Cell toxicity and cell proliferation on the scaffolds was also evaluated. The results indicated that the PLGA/HMS–HA scaffolds could effectively compensate the increased pH values caused by the acidic degradation product of PLGA. The compressive strength and modulus of PLGA/HMS–HA scaffolds were remarkably high compared to pure PLGA scaffold. Drug delivery testing of the PLGA/HMS–HA scaffolds indicated that PLGA slowed gentamycin sulfate (GS) release from HMS–HA particles, and the release lasted for nearly one month. Adding HMS–HA to PLGA scaffolds improved cytocompatibility. The scaffolds demonstrated low cytotoxicity, and supported mesenchymal stem cells growth more effectively than pure PLGA scaffolds. To summarize, the data supports the development of PLGA/HMS–HA scaffolds as potential degradable and drug delivery materials for bone replacement.     

Effect of autologous bone marrow stromal cell seeding and bone morphogenetic protein-2 delivery on ectopic bone formation in a microsphere/poly(propylene fumarate) composite

A biodegradable microsphere/scaffold composite based on the synthetic polymer poly(propylene fumarate) (PPF) holds promise as a scaffold for cell growth and sustained delivery vehicle for growth factors for bone regeneration. The objective of the current work was to investigate the in vitro release and in vivo bone forming capacity of this microsphere/scaffold composite containing bone morphogenetic protein-2 (BMP-2) in combination with autologous bone marrow stromal cells (BMSCs) in a goat ectopic implantation model. Three composites consisting of 0, 0.08, or 8 microg BMP-2 per mg of poly(lactic-co-glycolic acid) microspheres, embedded in a porous PPF scaffold, were combined with either plasma (no cells) or culture-expanded BMSCs. PPF scaffolds impregnated with a BMP-2 solution and combined with BMSCs as well as empty PPF scaffolds were also tested. The eight different composites were implanted subcutaneously in the dorsal thoracolumbar area of goats. Incorporation of BMP-2-loaded microspheres in the PPF scaffold resulted in a more sustained in vitro release with a lower burst phase, as compared to BMP-2-impregnated scaffolds. Histological analysis after 9 weeks of implantation showed bone formation in the pores of 11/16 composites containing 8 microg/mg BMP-2-loaded microspheres with no significant difference between composites with or without BMSCs (6/8 and 5/8, respectively). Bone formation was also observed in 1/8 of the BMP-2-impregnated scaffolds. No bone formation was observed in the other conditions. Overall, this study shows the feasibility of bone induction by BMP-2 release from microspheres/scaffold composites.     

PLGA microsphere/calcium phosphate cement composites for tissue engineering: in vitro release and degradation characteristics

Bone cements with biodegradable poly(lactic-co-glycolic acid) (PLGA) microspheres have already been proven to provide a macroporous calcium phosphate cement (CPC) during in situ microsphere degradation. Furthermore, in vitro/in vivo release studies with these PLGA microsphere/CPC composites (PLGA/CPCs) showed a sustained release of osteo-inductive growth factor when drug was distributed inside/onto the microspheres. The goal of this study was to elucidate the mechanism behind drug release from PLGA/CPC. For this, in vitro release and degradation characteristics of a low-molecular-weight PLGA/CPC (M(w) = 5 kg/mol) were determined using bovine serum albumin (BSA) as a model protein. Two loading mechanisms were applied; BSA was either adsorbed onto the microspheres or incorporated inside the microspheres during double-emulsion. BSA release from PLGA microspheres and CPC was also measured and used as reference. Results show fast degrading polymer microspheres which produced a macroporous scaffold within 4 weeks, but also showed a concomitant release of acidic degradation products. BSA release from the PLGA/CPC was similar to the CPC samples and showed a pattern consisting of a small initial release, followed by a period of almost no sustained release. Separate PLGA microspheres exhibited a high burst release and release efficiency that was higher with the adsorbed samples. Combining degradation and release data we can conclude that for the PLGA/CPC samples BSA re-adsorbed to the cement surface after being released from the microspheres, which was mediated by the pH decrease during microsphere degradation.     

Poly(lactic-co-glycolic acid) microspheres as an injectable scaffold for cartilage tissue engineering

Injectable scaffold has raised great interest for tissue regeneration in vivo, because it allows easy filling of irregularly shaped defects and the implantation of cells through minimally invasive surgical procedures. In this study, we evaluated poly(lactic-co-glycolic acid) (PLGA) microsphere as an injectable scaffold for in vivo cartilage tissue engineering. PLGA microspheres (30-80 microm in diameter) were injectable through various gauges of needles, as the microspheres did not obstruct the needles and microsphere size exclusion was not observed at injection. The culture of chondrocytes on PLGA microspheres in vitro showed that the microspheres were permissive for chondrocyte adhesion to the microsphere surface. Rabbit chondrocytes were mixed with PLGA microspheres and injected immediately into athymic mouse subcutaneous sites. Chondrocyte transplantation without PLGA microspheres and PLGA microsphere implantation without chondrocytes served as controls. Four and 9 weeks after implantation, chondrocytes implanted with PLGA microspheres formed solid, white cartilaginous tissues, whereas no gross evidence of cartilage tissue formation was noted in the control groups. Histological analysis of the implants by hematoxylin and eosin staining showed mature and well-formed cartilage. Alcian blue/safranin O staining and Masson's trichrome staining indicated the presence of highly sulfated glycosaminoglycans and collagen, respectively, both of which are the major extracellular matrices of cartilage. Immunohistochemical analysis showed that the collagen was mainly type II, the major collagen type in cartilage. This study demonstrates the feasibility of using PLGA microspheres as an injectable scaffold for in vivo cartilage tissue engineering. This scaffold may be useful to regenerate cartilaginous tissues through minimally invasive surgical procedures in orthopedic, maxillofacial, and urologic applications.     

Surface studies of coated polymer microspheres and protein release from tissue-engineered scaffolds

The controlled release of growth factors from porous, polymer scaffolds is being studied for potential use as tissue-engineered scaffolds. Biodegradable polymer microspheres were coated with a biocompatible polymer membrane to permit the incorporation of the microspheres into tissue-engineered scaffolds. Surface studies with poly(D,L-lactic-co-glycolic acid) [PLGA], and poly(vinyl alcohol) [PVA] were conducted. Polymer films were dip-coated onto glass slides and water contact angles were measured. The contact angles revealed an initially hydrophobic PLGA film, which became hydrophilic after PVA coating. After immersion in water, the PVA coating was removed and a hydrophobic PLGA film remained. Following optimization using these 2D contact angle studies, biodegradable PLGA microspheres were prepared, characterized, and coated with PVA. X-ray photoelectron spectroscopy was used to further characterize coated slides and microspheres. The release of the model protein bovine serum albumin from PVA-coated PLGA microspheres was studied over 8 days. The release of BSA from PVA-coated PLGA microspheres embedded in porous PLGA scaffolds over 24 days was also examined. Coating of the PLGA microspheres with PVA permitted their incorporation into tissue-engineered scaffolds and resulted in a controlled release of BSA.     

In vivo degradation of calcium phosphate cement incorporated into biodegradable microspheres

In this study we have investigated the influence of the mechanism of microsphere degradation or erosion on the in vivo degradation of microsphere/calcium phosphate cement composites (microsphere CPCs) used in tissue engineering. Microspheres composed of poly(lactic-co-glycolic acid) (PLGA), gelatin and poly(trimethylene carbonate) (PTMC) were used as the model and the resulting microsphere CPCs were implanted subcutaneously for 4, 8 or 12 weeks in the back of New Zealand white rabbits. Besides degradation, the soft tissue response to these formulations was evaluated. After retrieval, specimens were analyzed by physicochemical characterization and histological analysis. The results showed that all microsphere CPCs exhibited microsphere degradation after 12 weeks of subcutaneous implantation, which was accompanied by decreasing compression strength. The PLGA microspheres exhibited bulk erosion simultaneously throughout the whole composite, whereas the gelatin type B microspheres were degradated from the outside to the center of the composite. High molecular weight PTMC microspheres exhibited surface erosion resulting in decreasing microsphere size. Furthermore, all composites showed a similar tissue response, with decreasing capsule thickness over time and a persistent moderate inflammatory response at the implant interface. In conclusion, microsphere CPCs can be used to generate porous scaffolds in an in vivo environment after degradation of microspheres by various degradation/erosion mechanisms.     

In vitro evaluation of chitosan/poly(lactic acid-glycolic acid) sintered microsphere scaffolds for bone tissue engineering

A three-dimensional (3-D) scaffold is one of the major components in many tissue engineering approaches. We developed novel 3-D chitosan/poly(lactic acid-glycolic acid) (PLAGA) composite porous scaffolds by sintering together composite chitosan/PLAGA microspheres for bone tissue engineering applications. Pore sizes, pore volume, and mechanical properties of the scaffolds can be manipulated by controlling fabrication parameters, including sintering temperature and sintering time. The sintered microsphere scaffolds had a total pore volume between 28% and 37% with median pore size in the range 170-200microm. The compressive modulus and compressive strength of the scaffolds are in the range of trabecular bone making them suitable as scaffolds for load-bearing bone tissue engineering. In addition, MC3T3-E1 osteoblast-like cells proliferated well on the composite scaffolds as compared to PLAGA scaffolds. It was also shown that the presence of chitosan on microsphere surfaces increased the alkaline phosphatase activity of the cells cultured on the composite scaffolds and up-regulated gene expression of alkaline phosphatase, osteopontin, and bone sialoprotein.     

Surface studies of coated polymer microspheres and protein release from tissue-engineered scaffolds

The controlled release of growth factors from porous, polymer scaffolds is being studied for potential use as tissue-engineered scaffolds. Biodegradable polymer microspheres were coated with a biocompatible polymer membrane to permit the incorporation of the microspheres into tissueengineered scaffolds. Surface studies with poly(D,L-lactic-co-glycolic acid) [PLGA], and poly(vinyl alcohol) [PVA] were conducted. Polymer films were dip-coated onto glass slides and water contact angles were measured. The contact angles revealed an initially hydrophobic PLGA film, which became hydrophilic after PVA coating. After immersion in water, the PVA coating was removed and a hydrophobic PLGA film remained. Following optimization using these 2D contact angle studies, biodegradable PLGA microspheres were prepared, characterized, and coated with PVA. X-ray photoelectron spectroscopy was used to further characterize coated slides and microspheres. The release of the model protein bovine serum albumin from PVA-coated PLGA microspheres was studied over 8 days. The release of BSA from PVA-coated PLGA microspheres embedded in porous PLGA scaffolds over 24 days was also examined. Coating of the PLGA microspheres with PVA permitted their incorporation into tissue-engineered scaffolds and resulted in a controlled release of BSA.     

Accelerated bonelike apatite growth on porous polymer/ceramic composite scaffolds in vitro

Although biodegradable polymer/ceramic composite scaffolds can overcome the limitations of conventional ceramic bone substitutes, the osteogenic potential of these scaffolds needs to be further enhanced for efficient bone tissue engineering. In this study, bonelike apatite was efficiently coated onto the scaffold surface by using polymer/ceramic composite scaffolds instead of polymer scaffolds and by using an accelerated biomimetic process to enhance the osteogenic potential of the scaffold. The creation of bonelike, apatite-coated polymer scaffold was achieved by incubating the scaffolds in simulated body fluid (SBF). The apatite growth on porous poly(D,L-lactic-co-glycolic acid)/nanohydroxyapatite (PLGA/ HA) composite scaffolds was significantly faster than on porous PLGA scaffolds. In addition, the distribution of coated apatite was more uniform on PLGA/HA scaffolds than on PLGA scaffolds. After a 5-day incubation period, the mass of apatite coated onto PLGA/HA scaffolds incubated in 5 x SBF was 2.3-fold higher than PLGA/HA scaffolds incubated in 1 x SBF. Furthermore, when the scaffolds were incubated in 5 x SBF for 5 days, the mass of apatite coated onto PLGA/HA scaffolds was 4.5-fold higher than PLGA scaffolds. These results indicate that the biomimetic apatite coating can be accelerated by using a polymer/ceramic composite scaffold and concentrated SBF. When seeded with osteoblasts, the apatite-coated PLGA/HA scaffolds exhibited significantly higher cell growth, alkaline phosphatase activity, and mineralization in vitro compared to the apatite-coated PLGA scaffolds. Therefore, the apatite-coated PLGA/HA scaffolds may provide enhanced osteogenic potential when used as scaffold for bone tissue engineering.     

复合壳聚糖纳米微球聚乳酸-羟基乙酸/纳米羟基磷灰石缓释载体系统对蛋白的缓释作用

背景：聚乳酸-羟基乙酸支架材料具有良好的生物相容性、无毒、可以良好的塑性,并具有一定的强度和韧性。但其降解产物为酸性,会影响局部pH值变化,不利组织生长。 目的：制备能够良好缓释蛋白类药物的复合支架。 方法：以牛血清蛋白为模型药物,以离子凝胶法制备壳聚糖微球。将微球与纳米羟基磷灰石和聚乳酸-羟基乙酸按一定比例混合,以冰粒子为致孔剂,采用粒子沥虑-冷冻干燥复合工艺制备CMs/nHA/PLGA复合缓释支架。利用扫描电镜、透射电镜、压泵仪和力学性能测试仪检测复合支架的形态和性能,并考察其在体外对蛋白类药物释放的规律。 结果与结论：制备的壳聚糖纳米微球形态良好,呈规则球形或类球形,粒径分布在220~770 nm,以380~650 nm为多。微球对药物的载药量为39.2%,包封率为68.3%,两者均与牛血清蛋白的初始量相关,载药量随牛血清蛋白初始量的增加而增加,包封率则反之。复合支架呈白色多孔状,孔径为125~355 mm,孔与孔之间联通良好,孔隙率达83.4%,压缩强度为1.4~ 2.1 MPa,10周降解率为28.6%。PLGA/nHA支架对牛血清蛋白的2 d累积释放量为85%,而壳聚糖和CMs/nHA/PLGA复合支架对牛血清蛋白的9 d累积释放量分别是为48.9%和35.7%。提示制作的壳聚糖纳米微球和CMs/nHA/PLGA支架材料对牛血清蛋白有良好的缓释作用,复合支架材料形态好,强度和降解速率合适。     

Controllable dual-release of dexamethasone and bovine serum albumin from PLGA/β-tricalcium phosphate composite scaffolds

Localized dual-drug delivery from biodegradable scaffolds is an important strategy in tissue engineering. In this study, porous poly(L-lactide-co-glycolide) (PLGA)/β-tricalcium phosphate scaffolds containing both dexamethasone (Dex) and bovine serum albumin (BSA) were prepared by incorporating Dex-loaded and BSA-loaded microspheres into the scaffolds. PLGA microspheres containing Dex or BSA were prepared by spray-drying and double emulsion/solvent evaporation, respectively. In vitro release studies indicated that microspheres prepared from PLGA in 3:1 molar ratio of L-lactide/glycolide and 89.5 kDa relative molecular mass showed prolonged release profiles compared with those prepared from PLGA in 1:1 L-lactide/glycolide molar ratio and 30.5 kDa relative molecular mass. Additionally, introduction of poly(ethylene glycol) in the PLGA chain could improve the encapsulation efficiency and reduce the release rate. Based on the above results, controllable dual-release of Dex and BSA with relatively higher or lower release rate was achieved by incorporating Dex-loaded and BSA-loaded microspheres with different release profiles into the PLGA/β-tricalcium phosphate scaffolds.     

Incorporation of polymer microspheres within fibrin scaffolds for the controlled delivery of FGF-1

The purpose of this work was to examine the feasibility of a hybrid scaffold in which fibroblast growth factor-1 (FGF-1)-encapsulated microspheres are embedded within a fibrin gel. Such a tissue-engineered scaffold could be incorporated into surgical procedures to promote healing while simultaneously delivering therapeutic agents that promote angiogenesis. Fibrin has been extensively studied as an adhesive in plastic and reconstructive surgery and the enhancement of wound healing with embedded growth factors is desirable. We report the release of a fluorescentlylabeled model protein, bovine serum albumin (BSA-FITC), from poly(D, L-lactic-co-glycolic acid) microspheres embedded in the fibrin scaffold. The protein release was found to be significantly delayed as compared to microspheres alone during the initial 24 h of release. Additionally, FGF-1 was examined for efficient incorporation into these scaffolds as a potential mitogen for fibroblasts. The optimal concentration of FGF-1 in the media that enhanced NIH-3T3 fibroblast proliferation over 48 h was determined to be 0.1μg/ml. The release of FGF-1 from microspheres embedded in fibrin gels was compared to FGF-1-encapsulated microspheres alone. The release of FGF-1 from the microsphere/scaffolds was delayed as compared to the release of FGF-1 from microspheres alone. This novel hybrid fibrin/microsphere scaffold is a feasible delivery system for growth factors.     

Incorporation of polymer microspheres within fibrin scaffolds for the controlled delivery of FGF-1

The purpose of this work was to examine the feasibility of a hybrid scaffold in which fibroblast growth factor-1 (FGF-1)-encapsulated microspheres are embedded within a fibrin gel. Such a tissue-engineered scaffold could be incorporated into surgical procedures to promote healing while simultaneously delivering therapeutic agents that promote angiogenesis. Fibrin has been extensively studied as an adhesive in plastic and reconstructive surgery and the enhancement of wound healing with embedded growth factors is desirable. We report the release of a fluorescently-labeled model protein, bovine serum albumin (BSA-FITC), from poly(D,L-lactic-co-glycolic acid) microspheres embedded in the fibrin scaffold. The protein release was found to be significantly delayed as compared to microspheres alone during the initial 24 h of release. Additionally, FGF-1 was examined for efficient incorporation into these scaffolds as a potential mitogen for fibroblasts. The optimal concentration of FGF-1 in the media that enhanced NIH-3T3 fibroblast proliferation over 48 h was determined to be 0.1 microg/ml. The release of FGF-1 from microspheres embedded in fibrin gels was compared to FGF-1-encapsulated microspheres alone. The release of FGF-1 from the microsphere/scaffolds was delayed as compared to the release of FGF-1 from microspheres alone. This novel hybrid fibrin/microsphere scaffold is a feasible delivery system for growth factors.     

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.