Facile preparation and cytocompatibility of poly(lactic acid)/poly(3‐hydroxybutyrate‐co‐4‐hydroxybutyrate) hybrid fibrous scaffolds

A fibrous scaffold is required to provide three‐dimensional (3D) cell growth microenvironments and appropriate synergistic cell guidance cues. In this study, porous scaffolds with different mass ratio of poly(lactic acid) to poly(3‐hydroxybutyrate‐co‐4‐hydroxybutyrate) (P(3HB‐co‐4HB)) for tissue engineering were prepared by a modified particle leaching method. The effect of the addition of P(3HB‐co‐4HB) on microstructural morphology, compression property, swelling behavior, and enzymatic degradation of hybrid scaffolds was systematically investigated. The results indicated that this method was simple but efficient to prepare highly interconnected biomimetic 3D hybrid scaffolds (PP50/50 and PP33/67) with fibrous pore walls. The cytocompatibility of hybrid scaffolds was evaluated by in vitro culture of mesenchymal stem cells. The cell‐cultured hybrid scaffolds presented a complete 3D porous structure, thus allowing cell proliferation on the surface and infiltration into the inner part of scaffolds. The obtained hybrid scaffolds with pore size ranging from 200 to 450 µm, over 90% porosity, adjustable biodegradability, and water‐uptake capability will be promising for cartilage tissue engineering applications. POLYM. ENG. SCI., 54:2902–2910, 2014. © 2014 Society of Plastics Engineers     

Development of bone scaffold using Puntius conchonius fish scale derived hydroxyapatite: Physico-mechanical and bioactivity evaluations

Naturally derived Hydroxyapatite (HAp) from fish scale is finding wide applications in the development of bone scaffold to promote bone regeneration. But porous HAp scaffold is fragile in nature making it unsuitable for bone repair or replacement applications. Thus, it is essential to improve the mechanical property of HAp scaffolds while retaining the interconnected porous structure for tissue ingrowth in vivo. In this study solvent casting particulate leaching technique is used to develop novel Puntius conchonius fish scale derived HAp bone scaffold by varying the wt.% of the HAp from 60 to 80% in PMMA matrix. Physico-chemical, mechanical, structural and bioactive properties of the developed scaffolds are investigated. The obtained results indicate that HAp-PMMA scaffold at 70?wt % HAp loading shows optimal properties with 7.26?±?0.45?MPa compressive strength, 75?±?0.8% porosity, 8.0?±?0.68% degradation and 190?±?11% water absorption. The obtained results of the scaffold can meet the physiological demands to guide bone regeneration. Moreover, in vitro bioactivity analysis also confirms the formation of bone like apatite in the scaffold surface after 28 days of SBF immersion. Thus, the developed scaffold has the potential to be effectively used in bone tissue engineering applications.     

Mechanical strength and biocompatibility of bredigite (Ca7MgSi4O16) tissue-engineering scaffolds modified by aliphatic polyester coatings

Bredigite (Ca₇MgSi₄O₁₆) is a bioceramic with excellent bioactivity and bioresorbability; nonetheless, its inadequate mechanical strength and biocompatibility limit its tissue-engineering application. In this research, interconnected porous bredigite scaffolds were fabricated by sol-gel, sacrificial sponge replica and sintering processes for bone tissue engineering. In order to improve their strength and cytocompatibility, the scaffolds were coated with poly(lactic-co-glycolic acid) (PLGA) via immersion in acetone-based solutions containing different concentrations (5, 10 and 15% w/v) of the polymer. Based on the results, the PLGA coatings to 10% do not suppress the porosity characteristics of the scaffolds appropriate for tissue engineering. It was also found that the polymeric coatings significantly enhance the compressive strength of the ceramic scaffolds, where this alteration is improved by increasing the PLGA concentration of the coating solution. In addition, the viability of stem cells on the bredigite scaffolds are improved by using the PLGA coatings, with the optimal concentration of 10% PLGA according to MTT and cell attachment studies.     

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.     

Extrusion-based 3D printing of gelatin methacryloyl with nanocrystalline hydroxyapatite

The particle shape and size distribution of inorganic fillers play a crucial role in the scaffold buildability when those are incorporated in the viscoelastic polymers. In order to address this issue, the phase pure rod-shaped nanocrystalline hydroxyapatite (HAp) powders with varying particle sizes and shapes were synthesized by a one-pot hydrothermal method without any regulatory surfactant at an initial solution pH of 9. As-synthesized nanocrystalline HAp particles (0–5 wt%) were incorporated into 15 wt% pre-cross-linked gelatin methacryloyl (GelMA) hydrogel matrix to fabricate a predesigned scaffold architecture using a custom-made 3D bioprinter. The printing parameters (nozzle diameter, extrusion pressure, and printing speed) were optimized for each composition. The biophysical properties (uniaxial compression behavior, swelling ratio, and in vitro degradation) of the composite hydrogel scaffolds were critically analyzed to unravel the role of nano-sized HAp addition. The compression strength and modulus were substantially improved, while the rate of water uptake and bio-enzymatic degradation significantly reduced with HAp content. We propose that the inorganic–organic nanocomposite hydrogel could be efficiently assembled to formulate a potential bioink for 3D bioprinting applications toward tissue regeneration.     

Highly interconnected macroporous MBG/PLGA scaffolds with enhanced mechanical and biological properties via green foaming strategy

In this study, mesoporous bioactive glass particles (MBGs) are incorporated into poly(lactic-co-glycolic acid) (PLGA) to fabricate highly interconnected macroporous composite scaffolds with enhanced mechanical and biological properties via a developed supercritical carbon dioxide (scCO₂) foaming method. Scaffolds show favorable highly interconnected and macroporous structure through a high foaming pressure and long venting time foaming strategy. Specifically, scaffolds with porosity from 73% to 85%, pore size from 120 μm to 320 μm and interconnectivity of over 95% are controllably fabricated at MBG content from 0 wt% to 20 wt%. In comparison with neat PLGA scaffolds, composite scaffolds perform improved strength (up to 1.5 folds) and Young's modulus (up to 3 folds). The interconnected macroporous structure is beneficial to the ingrowth of cells. More importantly, composite scaffolds also provide a more promising microenvironment for cellular proliferation and adhesion with the release of bioactive ions. Hopefully, MBG/PLGA scaffolds developed by the green foaming strategy in this work show promising morphological, mechanical and biological features for tissue regeneration.     

Electrospun poly(L‐lactic acid)/hydroxyapatite composite fibrous scaffolds for bone tissue engineering

Poly(L ‐lactic acid) (PLLA) is one of the most studied synthetic biodegradable polymeric materials as a bone graft substitute. Taking into account the osteoconductive property of hydroxyapatite (HAp), we prepared fibrous matrices of PLLA without and with HAp particles in amounts of 0.25 or 0.50% (w/v, based on the volume of the base 15% w/v PLLA solution in 70:30 v/v dichloromethane/tetrahydrofuran). These fibrous matrices were assessed for their potential as substrates for bone cell culture. The presence of HAp in the composite fibre mats was confirmed using energy dispersive X‐ray spectroscopy mapping. The average diameters of both neat PLLA and PLLA/HAp fibres, as determined using scanning electron microscopy, ranged between 2.3 and 3.5 µm, with the average spacing between adjacent fibres ranging between 5.7 and 8.5 µm. The porosity of these fibrous membranes was high (ca 97–98%). A direct cytotoxicity evaluation with L929 mouse fibroblasts indicated that the neat PLLA fibre mats released no substance at a level that was toxic to the cells. The presence of HAp particles at 0.50% w/v in the PLLA fibrous scaffolds not only promoted the attachment and the proliferation of MC3T3‐E1 mouse pre‐osteoblastic cells, but also increased the expression of osteocalcin mRNA and the extent of mineralization after the cells had been cultured on the scaffolds for 14 and 21 days, respectively. The results obtained suggested that the PLLA/HAp fibre mats could be materials of choice for bone tissue engineering. Copyright © 2009 Society of Chemical Industry     

Bi-/multi-modal pore formation of PLGA/hydroxyapatite composite scaffolds by heterogeneous nucleation in supercritical CO2 foaming

Scaffolds with multimodal pore structure are essential to cells differentiation and proliferation in bone tissue engineering.Bi-/multi-modal porous PLGA/hydroxyapatite composite scaffolds were prepared by supercritical CO_2 foaming in which hydroxyapatite acted as heterogeneous nucleation agent.Bimodal porous scaffolds were prepared under certain conditions,i.e.hydroxyapatite addition of 5%,depressurization rate of 0.3 MPa·min~(-1),soaking temperature of 55℃,and pressure of 9 MPa.And scaffolds presented specific structure of small pores(122 μm±66 μm)in the cellular walls of large pores(552μm±127μm).Furthermore,multimodal porous PLGA scaffolds with micro-pores(37 μm±11 μm)were obtained at low soaking pressure of 7.5 MPa.The interconnected porosity of scaffolds ranged from(52.53±2.69)% to(83.08±2.42)%by adjusting depressurization rate,while compression modulus satisfied the requirement of bone tissue engineering.Solvent-free CO_2 foaming method is promising to fabricate bi-/multi-modal porous scaffolds in one step,and bioactive particles for osteogenesis could serve as nucleation agents.     

Sustained release of dexamethasone from drug‐loading PLGA scaffolds with specific pore structure fabricated by supercritical CO2 foaming

Inducing differentiation of bone marrow stem cells to generate new bone tissue is highly desirable by controlling the release of some osteoinductive or osteoconductive factors from porous scaffolds. In this study, dexamethasone was selected as a representative of small molecule drugs and dexamethasone‐loading porous poly(lactide‐co‐glycolide) (PLGA) scaffolds were successfully fabricated by supercritical CO₂ foaming. Scanning electron microscopy images showed that scaffolds had rough and relatively interconnected pores facilitating cells adhesion and growth. Specially, dexamethasone which was incorporated into PLGA matrix in a molecularly dispersed state could serve as a nucleation agent to be helpful for the formation of interconnected pores. Dexamethasone‐loading porous PLGA scaffolds exhibited sustained release profile, and the delivery of dexamethasone from porous scaffolds could last for up to 2 months. The cumulative released amount of dexamethasone was relevant with drug loading capacity (1.66%–2.95%) and pore structure of scaffolds; while the release behavior was anomalous (non‐Fickian) transport by fitting with the simple exponential equation, which had a diffusional exponent n higher than 0.5. It is feasible to fabricate drug‐loading porous scaffolds by supercritical CO₂ foaming with specific pore structure and sustained release profile, which can be well applied in bone tissue engineering. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46207.     

Study on development and in vitro biodegradation behaviour of poly(D,L-lactide-co-glycolide) 75/25 bioscaffolds

Abstract

Three-dimensional porous scaffolds based on biodegradable polymers are widely researched for applications to replace and restore the functions of diseased or damaged organs. The requirements for the scaffolds include: highly interconnected pore structures to facilitate cell adhesion for tissue regeneration, maintenance of mechanical properties and structural integrity until cells adapt to its environment and biodegradability with a controlled degradation rate. This paper focuses on the development and in vitro biodegradation behaviour of poly (D,L-lactide-co-glycolide acid) (PLGA) 75/25 and changes on pore morphology affected by initial pore sizes and degradation media. The pore morphology, mechanical properties, and geometric transformation were examined over the course of 13 weeks. It is concluded that the PLGA 75/25 scaffolds degraded after seven weeks and completely degraded after 13 weeks. The degradation time of scaffolds with small pores and in distilled water was comparatively shorter due to poorer interconnectivity of the pores and a more aggressive environment.     

I‐Optimal design of poly(lactic‐co‐glycolic) acid/hydroxyapatite three‐dimensional scaffolds produced by thermally induced phase separation

In bone tissue engineering, three‐dimensional (3D) scaffolds are often designed to have adequate modulus while taking into consideration the requirement for a highly porous network for cell seeding and tissue growth. This article presents the design optimization of 3D scaffolds made of poly(lactic‐co‐glycolic) acid (PLGA) and nanohydroxyapatite (nHA), produced by thermally induced phase separation (TIPS). Slow cooling at a rate of 1°C/min enabled a uniform temperature and produced porous scaffolds with a relatively uniform pore size. An I‐optimal design of experiments (DoE) with 18 experimental runs was used to relate four responses (scaffold thickness, density, porosity, and modulus) to three experimental factors, namely the TIPS temperature (?20, ?10, and 0°C), PLGA concentration (7%, 10%, and 13% w/v), and nHA content (0%, 15%, and 30% w/w). The response surface analysis using JMP® software predicted a temperature of ?18.3°C, a PLGA concentration of 10.3% w/v, and a nHA content of 30% w/w to achieve a thickness of 3 mm, a porosity of 83%, and a modulus of ~4 MPa. The set of validation scaffolds prepared using the predicted factor levels had a thickness of 3.05 ± 0.37 mm, a porosity of 86.8 ± 0.9%, and a modulus of 3.57 ± 2.28 MPa. POLYM. ENG. SCI., 59:1146–1157 2019. © 2019 Society of Plastics Engineers     

Effects of pore size on the mechanical and biological properties of stereolithographic 3D printed HAp bioceramic scaffold

In this study, hydroxyapatite (HAp) scaffolds with the pore size of 400, 500, and 600 μm were prepared by stereolithographic 3D printing (SL-3DP). The effects of pore size on mechanical and biological properties of the HAp scaffolds were investigated. Firstly, the macro- and microstructure of the HAp scaffolds were observed. Then, the compressive strength of the HAp scaffolds were tested. Finally, the biological properties of the HAp scaffolds were further characterized in vitro by the synthetic body fluid (SBF) solution immersion testing, as well as by using the cell proliferation and 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazolium bromide (MTT) assay. From this study, it was found that the HAp scaffold with a pore size of 600 μm had the most promising application prospect.     

Effect of Morphological Characteristics and Biomineralization of 3D-Printed Gelatin/Hyaluronic Acid/Hydroxyapatite Composite Scaffolds on Bone Tissue Regeneration

The use of porous three-dimensional (3D) composite scaffolds has attracted great attention in bone tissue engineering applications because they closely simulate the major features of the natural extracellular matrix (ECM) of bone. This study aimed to prepare biomimetic composite scaffolds via a simple 3D printing of gelatin/hyaluronic acid (HA)/hydroxyapatite (HAp) and subsequent biomineralization for improved bone tissue regeneration. The resulting scaffolds exhibited uniform structure and homogeneous pore distribution. In addition, the microstructures of the composite scaffolds showed an ECM-mimetic structure with a wrinkled internal surface and a porous hierarchical architecture. The results of bioactivity assays proved that the morphological characteristics and biomineralization of the composite scaffolds influenced cell proliferation and osteogenic differentiation. In particular, the biomineralized gelatin/HA/HAp composite scaffolds with double-layer staggered orthogonal (GEHA20-ZZS) and double-layer alternative structure (GEHA20-45S) showed higher bioactivity than other scaffolds. According to these results, biomineralization has a great influence on the biological activity of cells. Hence, the biomineralized composite scaffolds can be used as new bone scaffolds in bone regeneration.     

A kind of injectable Angelica sinensis polysaccharide(ASP)/hydroxyapatite (HAp) material for bone tissue engineering promoting vascularization,hematopoiesis, and osteogenesis in mice

Scaffolds made from single hydroxyapatite (HAp) possess neither biological properties of bone nor functions of promoting vascularization and inhibiting immune rejection. To overcome these drawbacks of HAp, Angelica sinensis polysaccharide (ASP)/HAp composite scaffolds were prepared and its application possibility in bone tissue engineering was studied. The scaffolds were examined by mechanical test, releasing test, degradation test, and histological evaluation. The results showed that the scaffolds had good degradation and ASP releasing. The histological examination indicated that ASP/HAp material could effectively promote vascularization, hematopoiesis, and osteogenesis in mice. In conclusion, the composite material could be used for bone tissue engineering with good prospect.     

Fabrication of co‐continuous poly(ε‐caprolactone)/polyglycolide blend scaffolds for tissue engineering

The apparent inability of a single biomaterial to meet all the requirements for tissue engineering scaffolds has led to continual research in novel engineered biomaterials. One method to provide new materials and fine‐tune their properties is via mixing materials. In this study, a biodegradable powder blend of poly(ε‐caprolactone) (PCL), polyglycolide (PGA), and poly(ethylene oxide) (PEO) was prepared and three‐dimensional interconnected porous PCL/PGA scaffolds were fabricated by combining cryomilling and compression molding/polymer leaching techniques. The resultant porous scaffolds exhibited co‐continuous morphologies with ～50% porosity. Mean pore sizes of 24 and 56 μm were achieved by varying milling time. The scaffolds displayed high mechanical properties and water uptake, in addition to a remarkably fast degradation rate. The results demonstrate the potential of this fabrication approach to obtain PCL/PGA blend scaffolds with interconnected porosity. In general, these results provide significant insight into an approach that will lead to the development of new composites and blends in scaffold manufacturing. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42471.     

聚乳酸⁃羟基乙酸共聚物涂层对聚乳酸3D打印支架的性能影响

通过熔融沉积（FDM）三维（3D）打印技术制备了61.7 %孔隙率和良好连通性的3D多孔聚乳酸（PLA）支架,使用浸涂法对PLA支架表面涂覆浓度分别为2 %、4 %、6 %、8 %的聚乳酸⁃羟基乙酸共聚物（PLGA）涂层,获得了不同浓度涂层的PLA/PLGA复合支架。通过扫描电子显微镜（SEM）、接触角测量仪、万能试验机和细胞计数试剂盒⁃8方法等测试手段,探究了不同浓度PLGA涂层对PLA支架的断面微观形貌、支架表面亲水性、力学强度以及细胞在支架上增殖活性等性能的影响规律。结果表明,与未经包裹的PLA支架相比,包裹PLGA的PLA支架表面接触角显著减小,PLGA的质量分数为6 %时接触角最小为（64.7±1.1） °;接种后经24 h培养PLA/PLGA支架表面细胞活性较纯PLA支架显著增强。     

Electrospinning of chitosan/poly(lactic acid-co-glycolic acid)/hydroxyapatite composite nanofibrous mats for tissue engineering applications

Electrospinning, which is a fiber fabrication technique using electrical forces to produce fibers with diameters ranging from nanometers to several micrometers, can be used to prepare materials mimicking the extracellular matrix proteins for potential use as tissue engineering scaffolds. In this study, nanofibrous mats of chitosan (CH) and poly(lactic acid-co-glycolic acid) (PLGA) having fiber diameters between 167 to 525 nm, and containing hydroxyapatite (HAp), were prepared by electrospinning technique. Morphological, chemical, thermal and degradation tests and cell affinity tests were carried out. Chitosan mats were stable in aqueous media and showed degradability in the presence of lysozyme. In PBS solution, PLGA mats disintegrated completely in 2 weeks. Meanwhile, CH-PLGA mats containing equal amounts of both CH and PLGA fibers and CH-PLGA-HAp samples containing 20 % HAp lost 50 and 40 % of their initial weight in 4 weeks, respectively. Cell culture tests showed that all electrospun fibrous mats promoted SaOs-2 cell attachment and proliferation. However, cell proliferation on CH-PLGA-HAp fibrous mats was higher compared to the others after 7 days demonstrating the positive effect of HAp on cell affinity properties compared to pristine CH or PLGA fibrous scaffolds.     

Fabrication of bimodal porous PLGA scaffolds by supercritical CO2 foaming/particle leaching technique

Specific pore structure is a vital essential for scaffolds applied in tissue engineering. In this article, poly(lactide‐co‐glycolide) (PLGA) scaffolds with a bimodal pore structure including macropores and micropores to facilitate nutrient transfer and cell adhesion were fabricated by combining supercritical CO₂ (scCO₂) foaming with particle leaching technique. Three kinds of NaCl particles with different scales (i.e., 100–250, <75, <10 μm) were used as porogens, respectively. In particular, heterogeneous nucleation occurred to modify scCO₂ foaming/particle leaching process when NaCl submicron particles (<10 μm) were used as porogens. The observation of PLGA scaffolds gave a formation of micropores (pore size <10 μm) in the cellular walls of macropores (pore size around 100–300 μm) to present a bimodal pore structure. With different mass fractions of NaCl introduced, the porosity of PLGA scaffolds ranged from 68.4 ± 1.4 to 88.7 ± 0.4% for three NaCl porogens. The results of SEM, EDS, and in vitro cytotoxicity test of PLGA scaffolds showed that they had uniform structures and were compatible for cell proliferation with no toxicity. This novel scCO₂ foaming/particle leaching method was promising in tissue engineering due to its ability to fabricate scaffolds with precise pore structure and high porosity. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43644.     

Fabrication and characterization of electrospun fibrous nanocomposite scaffolds based on poly(lactide‐co‐glycolide)/poly(vinyl alcohol) blends

Tissue engineering involves the fabrication of three‐dimensional scaffolds to support cellular in‐growth and proliferation. Ideally, the scaffolds should be similar to the native extracellular matrix (ECM). Electrospun polymer nanofibrous scaffolds are appropriate candidates for ECM mimetic materials since they mimic the nanoscale properties of ECM. Electrospun polymer nanocomposites based on poly(lactide‐co‐glycolide) (PLGA)/poly(vinyl alcohol) (PVA) and organically modified montmorillonite (OMMT) were prepared by a solution intercalation technique followed by electrospinning. The morphology of fibrous scaffolds based on these nanocomposites was investigated using scanning electron microscopy. The scaffolds showed highly porous structure within the nanofibres of diameters ranging from 400 to 700 nm. X‐ray diffractometry gave evidence of good dispersion of the OMMT in the blends with exfoliated morphology. Measurements of the water uptake and water contact angle of the fibrous scaffolds indicated significant improvement in the hydrophilicity of the scaffolds. Evaluations of the mechanical properties and unrestricted somatic stem cell culture of the electrospun fibrous nanocomposite scaffolds revealed that the PLGA90/PVA10/1.5% OMMT and PLGA90/PVA10/3% OMMT samples are the most useful from the tissue engineering application viewpoint. Copyright © 2010 Society of Chemical Industry     

3D Printed SiOC(N) Ceramic Scaffolds for Bone Tissue Regeneration: Improved Osteogenic Differentiation of Human Bone Marrow-Derived Mesenchymal Stem Cells

Bone tissue engineering has developed significantly in recent years as there has been increasing demand for bone substitutes due to trauma, cancer, arthritis, and infections. The scaffolds for bone regeneration need to be mechanically stable and have a 3D architecture with interconnected pores. With the advances in additive manufacturing technology, these requirements can be fulfilled by 3D printing scaffolds with controlled geometry and porosity using a low-cost multistep process. The scaffolds, however, must also be bioactive to promote the environment for the cells to regenerate into bone tissue. To determine if a low-cost 3D printing method for bespoke SiOC(N) porous structures can regenerate bone, these structures were tested for osteointegration potential by using human mesenchymal stem cells (hMSCs). This includes checking the general biocompatibilities under the osteogenic differentiation environment (cell proliferation and metabolism). Moreover, cell morphology was observed by confocal microscopy, and gene expressions on typical osteogenic markers at different stages for bone formation were determined by real-time PCR. The results of the study showed the pore size of the scaffolds had a significant impact on differentiation. A certain range of pore size could stimulate osteogenic differentiation, thus promoting bone regrowth and regeneration.