Mesenchymal stem cell responses to bone-mimetic electrospun matrices composed of polycaprolactone, collagen I and nanoparticulate hydroxyapatite

The performance of biomaterials designed for bone repair depends, in part, on the ability of the material to support the adhesion and survival of mesenchymal stem cells (MSCs). In this study, a nanofibrous bone-mimicking scaffold was electrospun from a mixture of polycaprolactone (PCL), collagen I, and hydroxyapatite (HA) nanoparticles with a dry weight ratio of 50/30/20 respectively (PCL/col/HA). The cytocompatibility of this tri-component scaffold was compared with three other scaffold formulations: 100% PCL (PCL), 100% collagen I (col), and a bi-component scaffold containing 80% PCL/20% HA (PCL/HA). Scanning electron microscopy, fluorescent live cell imaging, and MTS assays showed that MSCs adhered to the PCL, PCL/HA and PCL/col/HA scaffolds, however more rapid cell spreading and significantly greater cell proliferation was observed for MSCs on the tri-component bone-mimetic scaffolds. In contrast, the col scaffolds did not support cell spreading or survival, possibly due to the low tensile modulus of this material. PCL/col/HA scaffolds adsorbed a substantially greater quantity of the adhesive proteins, fibronectin and vitronectin, than PCL or PCL/HA following in vitro exposure to serum, or placement into rat tibiae, which may have contributed to the favorable cell responses to the tri-component substrates. In addition, cells seeded onto PCL/col/HA scaffolds showed markedly increased levels of phosphorylated FAK, a marker of integrin activation and a signaling molecule known to be important for directing cell survival and osteoblastic differentiation. Collectively these results suggest that electrospun bone-mimetic matrices serve as promising degradable substrates for bone regenerative applications.     

Fabrication of porous polycaprolactone/hydroxyapatite (PCL/HA) blend scaffolds using a 3D plotting system for bone tissue engineering

For tissue engineering and regeneration, a porous scaffold with interconnected networks is needed to guide cell attachment and growth/ingrowth in three-dimensional (3D) structure. Using a rapid prototyping (RP) technique, we designed and fabricated 3D plotting system and three types of scaffolds: those from polycaprolactone (PCL), those from PCL and hydroxyapatite (HA), and those from PCL/HA and with a shifted pattern structure (PCL/HA/SP scaffold). Shifted pattern structure was fabricated to increase the cell attachment/adhesion. The PCL/HA/SP scaffold had a lower compressive modulus than PCL and PCL/HA scaffold. However, it has a better cell attachment than the scaffolds without a shifted pattern. MTT assay and alkaline phosphatase activity results for the PCL/HA/SP scaffolds were significantly enhanced compared to the results for the PCL and PCL/HA scaffolds. According to their degree of cell proliferation/differentiation, the scaffolds were in the following order: PCL/HA/SP > PCL/HA > PCL. These 3D scaffolds will be applicable for tissue engineering based on unique plotting system.     

仿生聚己内酯支架用于乳房组织工程的可行性研究

目的探讨聚己内酯（PCL）乳房形态支架用于组织工程乳房的构建的可能性。 方法通过熔融沉积3D打印制备形态仿生的PCL支架,测量其机械性能,并使用新西兰大白兔动物模型,皮下植入该PCL支架12周和18周后,利用核磁共振成像（MRI）观察支架内部新生组织分布情况,在组织学（HE、Masson及EVG染色）上评估支架内部的脂肪、纤维及血管的分布情况,并进一步使用qRT-PCR检测了12周时PCL支架内部组织的成脂相关基因（PPAR-γ、C/EBP-β、AP-2）、炎症相关基因TNF-α及巨噬细胞标记物F4-80的表达情况,同时使用凝胶渗透色谱法分析了PCL植入体内后平均分子量的变化。2组间均数比较采用独立样本t检验,多组间比较采用单因素方差分析,组间两两比较采用LSD-t检验,配对设计的均数比较采用配对t检验。 结果制备的PCL支架孔隙率为（85.30±1.12）%,压缩模量为（8.18±1.39）MPa,植入新西兰大白兔动物模型皮下12周后,MRI影像学显示脂肪组织已由支架周围向内部侵入,HE、Masson及EVG染色同样在该支架边缘观察到部分新生脂肪组织及血管,而支架内部则以疏松排列的纤维组织为主;与原生脂肪比较,12周PCL支架内组织的基因表达分析成脂相关基因C/EBPβ表达水平（2.32±0.28比1.00±0.02）升高,而巨噬细胞标记物F4/80表达（0.80±0.12比1.00±0.03）降低（P均< 0.01）;18周后,HE染色证实支架内部已充满脂肪组织。基因表达证实,与原生脂肪比较,支架内部组织C/EBP-β （3.30±0.63比1.00±0.02）,PPAR-γ （1.81±0.71比0.99±0.02）及AP-2表达水平（1.38±0.16比1.01±0.01）升高（P均< 0.01）;而TNF-α（0.50±0.15比1.00±0.01）及F4/80表达水平（0.52±0.09比1.00±0.03）均降低（P均< 0.001）。而植入体内PCL支架的分子量（M_n）在18周内变化不大[（65.04±2.24）kDa比（64.20±4.09） kDa]。 结论PCL支架具有较好的生物相容性,可用于组织工程乳房的构建,该新西兰大白兔动物模型的建立有利于乳房组织工程的进一步临床转化。     

A complete structural performance analysis and modelling of hydroxyapatite scaffolds with variable porosity

The use of hydroxyapatite (HA) scaffolds for bone regeneration is an alternative procedure to treat bone defects due to cancer, other diseases or traumas. Although the use of HA has been widely studied in the literature, there are still some disparities regarding its mechanical performance. This paper presents a complete analysis of the structural performance of porous HA scaffolds based on experimental tests, numerical simulations and theoretical studies. HA scaffolds with variable porosity were considered and fabricated by the water-soluble polymer method, using poly vinyl alcohol as pore former. These scaffolds were then characterised by scanning electron microscopy, stereo microscopy, X-ray diffraction, porosity analysis and mechanical tests. Different scaffold models were proposed and analysed by the finite element method to obtain numerical predictions of the mechanical properties. Also theoretical predictions based on the (Gibson LJ, Ashby MF. 1988. Cellular solids: structure and properties. Oxford: Pergamon Press) model were obtained. Finally the experimental, numerical and theoretical results were compared. From this comparison, it was observed that the proposed numerical and theoretical models can be used to predict, with adequate accuracy, the mechanical performance of HA scaffolds for different porosity values.     

Characterization of tissue scaffolds for time-dependent biotransport criteria – a novel computational procedure

This study aims to establish a new computational framework that allows modeling transient oxygen diffusion in tissue scaffolds more efficiently. It has been well known that the survival of cells strongly relies on continuous oxygen/nutrient supply and metabolite removal. With optimal design in scaffold architecture, its ability to sustain long distance oxygen supply could be improved considerably. In this study, finite element based homogenization procedure is first used to characterize the initial effective biotransport properties in silico. These initial properties are proper indicators to prediction of the on-going performance of tissue scaffolds over time. The transient model by adopting an edge-based smoothed finite element method with combination of mass-redistributed method is then established to more efficiently simulate the transient oxygen transfer process in tissue scaffolds. The proposed new method allows large time steps to model the oxygen diffusion process without losing numerical accuracy, thereby enhancing the computational efficiency significantly, in particular for the design optimization problems which typically require numerous analysis iterations. A number of different scaffold designs are examined either under net diffusion without cell seeding, or under cellular oxygen/nutrient uptake with or without considering cell viability. The association between the homogenized effective diffusivity of net scaffold microstructures and corresponding transient diffusion and time-dependent cellular activities is divulged. This study provides some insights into scaffold design.     

Electrospun Poly(L-lactide)/Poly(ε-caprolactone) Blend Nanofibrous Scaffold: Characterization and Biocompatibility with Human Adipose-Derived Stem Cells

The essence of tissue engineering is the fabrication of autologous cells or induced stem cells in naturally derived or synthetic scaffolds to form specific tissues. Polymer is thought as an appealing source of cell-seeded scaffold owing to the diversity of its physicochemical property and can be electrospun into nano-size to mimic natural structure. Poly (L-lactic acid) (PLLA) and poly (ε-caprolactone) (PCL) are both excellent aliphatic polyester with almost “opposite” characteristics. The controlling combination of PLLA and PCL provides varying properties and makes diverse applications. Compared with the copolymers of the same components, PLLA/PCL blend demonstrates its potential in regenerative medicine as a simple, efficient and scalable alternative. In this study, we electrospun PLLA/PCL blends of different weight ratios into nanofibrous scaffolds (NFS) and their properties were detected including morphology, porosity, degradation, ATR-FTIR analysis, stress-stain assay, and inflammatory reaction. To explore the biocompatibility of the NFS we synthesized, human adipose-derived stem cells (hASCs) were used to evaluate proliferation, attachment, viability and multi-lineage differentiation. In conclusion, the electrospun PLLA/PCL blend nanofibrous scaffold with the indicated weight ratios all supported hASCs well. However, the NFS of 1/1 weight ratio showed better properties and cellular responses in all assessments, implying it a biocompatible scaffold for tissue engineering.     

Processing/structure/property relationship of multi-scaled PCL and PCL-HA composite scaffolds prepared via gas foaming and NaCl reverse templating

In this study, we investigated the processing/structure/property relationship of multi-scaled porous biodegradable scaffolds prepared by combining the gas foaming and NaCl reverse templating techniques. Poly(ε-caprolactone) (PCL), hydroxyapatite (HA) nano-particles and NaCl micro-particles were melt-mixed by selecting different compositions and subsequently gas foamed by a pressure-quench method. The NaCl micro-particles were finally removed from the foamed systems in order to allow for the achievement of the multi-scaled scaffold pore structure. The control of the micro-structural properties of the scaffolds was obtained by the optimal combination of the NaCl templating concentration and the composition of the CO2-N2 mixture as the blowing agent. In particular, these parameters were accurately selected to allow for the fabrication of PCL and PCL-HA composite scaffolds with multi-scaled open pore structures. Finally, the biocompatibility of the scaffolds has been assessed by cultivating pre-osteoblast MG63 cells in vitro, thus demonstrating their potential applications for bone regeneration.     

利用聚己内酯/羟基磷灰石复合支架修复犬胸骨缺损

目的：探讨利用生物可降解支架修复动物胸骨缺损,为临床手术治疗提供新的可行性方法。方法：对于12只比格犬进行手术切除部分胸骨,并利用聚己内酯/羟基磷灰石（PCL/HA）复合支架,并制备出与临床相似的胸骨缺损模型。实验动物分成2组,分别是：空白对照组和PCL/HA支架组。分别于术后第4、12周进行胸部CT扫描,并对胸廓进行三维重建,观察胸骨缺损部位的修复情况,并在第12周取胸骨缺损部位组织进行硬组织切片,苦味酸-品红染色,观察缺损部位的骨组织修复情况,并利用软件进行骨组织比率分析,评估修复情况。结果：通过检查发现空白对照组的胸骨缺损部位未见明显骨连接,胸廓的骨性结构有明显畸形,PCL/HA支架组能很好地维持胸廓的完整性,组织学检查发现PCL/HA支架组的缺损部位有明显新生骨形成,通过软件分析可发现支架组的骨组织比率较空白组的高（P〈0.05）。结论：这些结果表明采用PCL/HA复合材料支架能很好地修复胸骨缺损。     

A structural model for the flexural mechanics of nonwoven tissue engineering scaffolds

The development of methods to predict the strength and stiffness of biomaterials used in tissue engineering is critical for load-bearing applications in which the essential functional requirements are primarily mechanical. We previously quantified changes in the effective stiffness (E) of needled nonwoven polyglycolic acid (PGA) and poly-L-lactic acid (PLLA) scaffolds due to tissue formation and scaffold degradation under three-point bending. Toward predicting these changes, we present a structural model for E of a needled nonwoven scaffold in flexure. The model accounted for the number and orientation of fibers within a representative volume element of the scaffold demarcated by the needling process. The spring-like effective stiffness of the curved fibers was calculated using the sinusoidal fiber shapes. Structural and mechanical properties of PGA and PLLA fibers and PGA, PLLA, and 50:50 PGA/PLLA scaffolds were measured and compared with model predictions. To verify the general predictive capability, the predicted dependence of E on fiber diameter was compared with experimental measurements. Needled nonwoven scaffolds were found to exhibit distinct preferred (PD) and cross-preferred (XD) fiber directions, with an E ratio (PD/XD) of approximately 3:1. The good agreement between the predicted and experimental dependence of E on fiber diameter (R2 = 0.987) suggests that the structural model can be used to design scaffolds with E values more similar to native soft tissues. A comparison with previous results for cell-seeded scaffolds (Engelmayr, G. C., Jr., et al., 2005, Biomaterials, 26(2), pp. 175-187) suggests, for the first time, that the primary mechanical effect of collagen deposition is an increase in the number of fiber-fiber bond points yielding effectively stiffer scaffold fibers. This finding indicated that the effects of tissue deposition on needled nonwoven scaffold mechanics do not follow a rule-of-mixtures behavior. These important results underscore the need for structural approaches in modeling the effects of engineered tissue formation on nonwoven scaffolds, and their potential utility in scaffold design.     

Three-dimensional hierarchical composite scaffolds consisting of polycaprolactone, β-tricalcium phosphate, and collagen nanofibers: fabrication, physical properties, and in vitro cell activity for bone tissue regeneration

β-Tricalcium phosphate (β-TCP) and collagen have been widely used to regenerate various hard tissues, but although Bioceramics and collagen have various biological advantages with respect to cellular activity, their usage has been limited due to β-TCP's inherent brittleness and low mechanical properties, along with the low shape-ability of the three-dimensional collagen. To overcome these material deficiencies, we fabricated a new hierarchical scaffold that consisted of a melt-plotted polycaprolactone (PCL)/β-TCP composite and embedded collagen nanofibers. The fabrication process was combined with general melt-plotting methods and electrospinning. To evaluate the capability of this hierarchical scaffold to act as a biomaterial for bone tissue regeneration, physical and biological assessments were performed. Scanning electron microscope (SEM) micrographs of the fabricated scaffolds indicated that the β-TCP particles were uniformly embedded in PCL struts and that electrospun collagen nanofibers (diameter = 160 nm) were well layered between the composite struts. By accommodating the β-TCP and collagen nanofibers, the hierarchical composite scaffolds showed dramatic water-absorption ability (100% increase), increased hydrophilic properties (20%), and good mechanical properties similar to PCL/β-TCP composite. MTT assay and SEM images of cell-seeded scaffolds showed that the initial attachment of osteoblast-like cells (MG63) in the hierarchical scaffold was 2.2 times higher than that on the PCL/β-TCP composite scaffold. Additionally, the proliferation rate of the cells was about two times higher than that of the composite scaffold after 7 days of cell culture. Based on these results, we conclude that the collagen nanofibers and β-TCP particles in the scaffold provide good synergistic effects for cell activity.     

Fabrication of gelatin-hyaluronic acid hybrid scaffolds with tunable porous structures for soft tissue engineering

The development of three-dimensional (3-D) scaffolds with highly open porous structure is one of the most important issues in tissue engineering. In this study, 3-D macroporous gelatin/hyaluronic acid (GE/HA) hybrid scaffolds with varying porous morphology were prepared by freeze-drying their blending solutions and subsequent chemical crosslinking by using 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrochloride (EDC). The resulting scaffolds were characterized by scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR). Their swelling, in vitro degradation properties and compressive strength were also investigated. To evaluate in vitro cytocompatibility of scaffolds, mouse L929 fibroblasts were seeded onto the scaffolds for cell morphology and cell viability studies. It was found that the porous structure of scaffolds can be tailored by varying the ratios of gelatin to HA, both the swelling ratios and degradation rate increased with the increase of HA content in hybrid scaffolds, and crosslinking the scaffolds with EDC improved the degradation resistance of the scaffold in culture media and increased the mechanical strength of scaffolds. The in vitro results revealed that the prepared scaffolds do not induce cytotoxic effects and suitable for cell growth, especially in the case of scaffolds with higher gelatin content. The combined results of the physicochemical and biological studies suggested that the developed GE/HA hybrid scaffolds exhibit good potential and biocompatibility for soft tissue engineering applications.     

Promotion of human mesenchymal stem cell differentiation on bioresorbable polycaprolactone/biphasic calcium phosphate composite scaffolds for bone tissue engineering

An artificial construct mimicking the intrinsic properties of the natural extracellular matrix in bones has been considered an ideal platform for bone tissue engineering, as it can present an appropriate microenvironment and regulate cell behaviours. In this report, we introduce biodegradable composite scaffolds consisting of polycaprolactone (PCL) and biphasic calcium phosphate (BCP). The scaffolds were fabricated by a salt-leaching process, and the ability of the scaffolds to facilitate osteogenic differentiation was investigated using human mesenchymal stem cells (hMSCs). The scaffolds had an inter-connected porous structure with quadrilateral pores of approximately 200 ～ 500 μm in width. The mechanical properties of the scaffolds changed as the BCP content was increased in the starting mixture. In the hMSC experiment, although we found that hMSCs adhered to the surface, as well as the inside, of the scaffolds, the incorporated BCP did not increase the proliferation of the hMSCs over 7 days in culture. Interestingly, the alkaline phosphatase (ALP) activity was 4 times higher on the PCL/BCP composite scaffold (0.12 ± 0.03 nmol/min/μg protein) thanon the PCL scaffold (0.03 ± 0.01 nmol/min/μg protein), suggesting that BCP can aid in generating a local environment that promotes bone regeneration. Therefore, a strategy combining polymers and ceramics can be considered a useful platform for bone tissue engineering.     

Porous scaffolds from high molecular weight polyesters synthesized via enzyme-catalyzed ring-opening polymerization

Several aliphatic polyesters have been synthesized until now using enzyme-catalyzed ring-opening polymerization (ROP) of different lactones, although their molecular weight, hence mechanical strength, was not sufficient enough to fabricate porous scaffolds from them. To achieve this target, 1,5-dioxepan-2-one (DXO) and epsilon-caprolactone (CL) were polymerized in bulk with Lipase CA as catalyst at 60 degrees C, and porous scaffolds were prepared from the polymers obtained thereof using a salt leaching technique. The CL/DXO molar feed ratio was varied from 1.5 to 10, and the reactivity ratios of CL and DXO were determined using the Kelen-Tudos method under such conditions of polymerization. NMR results showed a slightly lower CL/DXO molar ratio in the copolymers than in the feed due to high reactivity of DXO toward Lipase CA catalysis. The crystallinity of the PCL segment of the copolymers was affected by the presence of soft and amorphous DXO domains. The copolymers having high CL content were thermally more stable. The porosity of the scaffolds was in the range 82-88%, and the SEM analysis showed interconnected pores in the scaffolds. Of the two parameters which could affect the mechanical properties, viz., the copolymer composition and the scaffold pore size, the pore size showed a significant effect on the mechanical properties of the scaffolds. The porous scaffolds developed in this way for tissue engineering are free from toxic organometallic catalyst residues, and they are highly suitable for biomedical applications.     

Biodegradable polyurethane ureas with variable polyester or polycarbonate soft segments: effects of crystallinity, molecular weight, and composition on mechanical properties

Biodegradable polyurethane urea (PUU) elastomers are ideal candidates for fabricating tissue engineering scaffolds with mechanical properties akin to strong and resilient soft tissues. PUU with a crystalline poly(ε-caprolactone) (PCL) macrodiol soft segment (SS) showed good elasticity and resilience at small strains (<50%) but showed poor resilience under large strains because of stress-induced crystallization of the PCL segments, with a permanent set of 677 ± 30% after tensile failure. To obtain softer and more resilient PUUs, we used noncrystalline poly(trimethylene carbonate) (PTMC) or poly(δ-valerolactone-co-ε-caprolactone) (PVLCL) macrodiols of different molecular weights as SSs that were reacted with 1,4-diisocyanatobutane and chain extended with 1,4-diaminobutane. Mechanical properties of the PUUs were characterized by tensile testing with static or cyclic loading and dynamic mechanical analysis. All of the PUUs synthesized showed large elongations at break (800-1400%) and high tensile strength (30-60 MPa). PUUs with noncrystalline SSs all showed improved elasticity and resilience relative to the crystalline PCL-based PUU, especially for the PUUs with high molecular weight SSs (PTMC 5400 M(n) and PVLCL 6000 M(n)), of which the permanent deformation after tensile failure was only 12 ± 7 and 39 ± 4%, respectively. The SS molecular weight also influenced the tensile modulus in an inverse fashion. Accelerated degradation studies in PBS containing 100 U/mL lipase showed significantly greater mass loss for the two polyester-based PUUs versus the polycarbonate-based PUU and for PVLCL versus PCL polyester PUUs. Basic cytocompatibility was demonstrated with primary vascular smooth muscle cell culture. The synthesized families of PUUs showed variable elastomeric behavior that could be explained in terms of the underlying molecular design and crystalline behavior. Depending on the application target of interest, these materials may provide options or guidance for soft tissue scaffold development.     

Electrospun poly (ɛ-caprolactone)/silk fibroin core-sheath nanofibers and their potential applications in tissue engineering and drug release

One of the key tenets of tissue engineering is to develop scaffold materials with favorable biodegradability, surface properties, outstanding mechanical strength and controlled drug release property. In this study, we generated core-sheath nanofibers composed of poly (?-caprolactone) (PCL) and silk fibroin (SF) blends via emulsion electrospinning. Nanofibrous scaffolds were characterized by combined techniques of scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), differential scanning calorimetry (DSC), contact angle and tensile measurements. An in vitro FITC release study was conducted to evaluate sustained release potential of the core-sheath structured nanofibers. We found that the conformation of SF contained in PCL/SF composite nanofibers was transformed from random coil to β-sheet when treated with methanol, leading to improved crystallinity and tensile strength of nanofibrous scaffolds. The hydrophobicity and diameter of nanofibers decreased when we increased the content of SF in PCL/SF composite nanofibers. Furthermore, we evaluated the potential of fabricated PCL/SF composite nanofibers as scaffold in vitro. The results confirmed that fabricated PCL/SF scaffolds improved cell attachment and proliferation. Our results demonstrated the feasibility to generate core-sheath nanofibers composed of PCL and SF using a single-nozzle technique. The produced nanofibrous scaffolds with sustained drug release have potential application in tissue engineering.     

Fabrication and evaluation of poly(epsilon-caprolactone)/silk fibroin blend nanofibrous scaffold

In this study we investigated the blend electrospinning of poly(?‐caprolactone) (PCL) and silk fibroin (SF) to improve the biodegradability and biocompatibility of PCL‐based nanofibrous scaffolds. Optimal conditions to fabricate PCL/SF (50/50) blend nanofiber were established for electrospinning using formic acid as a cosolvent and three‐dimensional (3D) PCL/SF blend nanofibrous scaffolds were prepared by a modified electrospinning process using methanol coagulation bath. The physical properties of 2D PCL/SF blend nanofiber mats and 3D highly porous blend nanofibrous scaffolds were measured and compared. To evaluate cytocompatibility of the 3D blend scaffolds as compared to 3D PCL nanofibrous scaffold, normal human dermal fibroblasts were cultured. It is concluded that biodegradability and cytocompatibility could be improved for the 3D highly porous PCL/SF (50/50) blend nanofibrous scaffold prepared by blending PCL with SF in electrospinning. In addition to the blending of PCL and SF, the 3D structure and high porosity of electrospun nanofiber assemblies may also be important factors for enhancing the performance of scaffolds. © 2011 Wiley Periodicals, Inc. Biopolymers 97: 265–275, 2012.     

Microporous Dermal-Mimetic Electrospun Scaffolds Pre-Seeded with Fibroblasts Promote Tissue Regeneration in Full-Thickness Skin Wounds

Electrospun scaffolds serve as promising substrates for tissue repair due to their nanofibrous architecture and amenability to tailoring of chemical composition. In this study, the regenerative potential of a microporous electrospun scaffold pre-seeded with dermal fibroblasts was evaluated. Previously we reported that a 70% collagen I and 30% poly(Ɛ-caprolactone) electrospun scaffold (70:30 col/PCL) containing 160 μm diameter pores had favorable mechanical properties, supported fibroblast infiltration and subsequent cell-mediated deposition of extracellular matrix (ECM), and promoted more rapid and effective in vivo skin regeneration when compared to scaffolds lacking micropores. In the current study we tested the hypothesis that the efficacy of the 70:30 col/PCL microporous scaffolds could be further enhanced by seeding scaffolds with dermal fibroblasts prior to implantation into skin wounds. To address this hypothesis, a Fischer 344 (F344) rat syngeneic model was employed. In vitro studies showed that dermal fibroblasts isolated from F344 rat skin were able to adhere and proliferate on 70:30 col/PCL microporous scaffolds, and the cells also filled the 160 μm pores with native ECM proteins such as collagen I and fibronectin. Additionally, scaffolds seeded with F344 fibroblasts exhibited a low rate of contraction (~14%) over a 21 day time frame. To assess regenerative potential, scaffolds with or without seeded F344 dermal fibroblasts were implanted into full thickness, critical size defects created in F344 hosts. Specifically, we compared: microporous scaffolds containing fibroblasts seeded for 4 days; scaffolds containing fibroblasts seeded for only 1 day; acellular microporous scaffolds; and a sham wound (no scaffold). Scaffolds containing fibroblasts seeded for 4 days had the best response of all treatment groups with respect to accelerated wound healing, a more normal-appearing dermal matrix structure, and hair follicle regeneration. Collectively these results suggest that microporous electrospun scaffolds pre-seeded with fibroblasts promote greater wound-healing than acellular scaffolds.     

Computational modelling of local calcium ions release from calcium phosphate-based scaffolds

A variety of natural or synthetic calcium phosphate (CaP)-based scaffolds are currently produced for dental and orthopaedic applications. These scaffolds have been shown to stimulate bone formation due to their biocompatibility, osteoconductivity and osteoinductivity. The release of the \(\hbox {Ca}^{2+}\) ions from these scaffolds is of great interest in light of the aforementioned properties. It can depend on a number of biophysicochemical phenomena such as dissolution, diffusion and degradation, which in turn depend on specific scaffold characteristics such as composition and morphology. Achieving an optimal release profile can be challenging when relying on traditional experimental work alone. Mathematical modelling can complement experimentation. In this study, the in vitro dissolution behaviour of four CaP-based scaffold types was investigated experimentally. Subsequently, a mechanistic finite element method model based on biophysicochemical phenomena and specific scaffold characteristics was developed to predict the experimentally observed behaviour. Before the model could be used for local \(\hbox {Ca}^{2+}\) ions release predictions, certain parameters such as dissolution constant (\(k_{\mathrm{dc}}\)) and degradation constant (\(k_\mathrm{sc}\)) for each type of scaffold were determined by calibrating the model to the in vitro dissolution data. The resulting model showed to yield release characteristics in satisfactory agreement with those observed experimentally. This suggests that the mathematical model can be used to investigate the local \(\hbox {Ca}^{2+}\) ions release from CaP-based scaffolds.     

Novel hybrid scaffolds for the cultivation of osteoblast cells

In this study, natural biodegradable polysaccharide, chitosan, and synthetic biodegradable polymer, poly(?-caprolactone) (PCL) were used to prepare 3D, hybrid polymeric tissue scaffolds (PCL/chitosan blend and PCL/chitosan/PCL layer by layer scaffolds) by using the electrospinning technique. The hybrid scaffolds were developed through HA addition to accelerate osteoblast cell growth. Characteristic examinations of the scaffolds were performed by micrometer, SEM, contact angle measurement system, ATR-FTIR, tensile machine and swelling experiments. The thickness of all electrospun scaffolds was determined in the range of 0.010 ± 0.001-0.012 ± 0.002 mm. In order to optimize electrospinning processes, suitable bead-free and uniform scaffolds were selected by using SEM images. Blending of PCL with chitosan resulted in better hydrophilicity for the PCL/chitosan scaffolds. The characteristic peaks of PCL and chitosan in the blend and layer by layer nanofibers were observed. The PCL/chitosan/PCL layer by layer structure had higher elastic modulus and tensile strength values than both individual PCL and chitosan structures. The layer by layer scaffolds exhibited the PBS absorption values of 184.2; 197.2% which were higher than those of PCL scaffolds but lower than those of PCL/chitosan blend scaffolds. SaOs-2 osteosarcoma cell culture studies showed that the highest ALP activities belonged to novel PCL/chitosan/PCL layer by layer scaffolds meaning better cell differentiation on the surfaces.