In vivo biocompatibility and osteogenesis of electrospun poly(ε-caprolactone)-poly(ethylene glycol)-poly(ε-caprolactone)/nano-hydroxyapatite composite scaffold

A flexible and fibrous composite scaffold composed of poly(ε-caprolactone)-poly(ethylene glycol)-poly(ε-caprolactone) (PCL-PEG-PCL, PCEC) and 30?wt.% nano-hydroxyapatite (n-HA) was fabricated through electrospinning. In the present study, we investigated its in?vitro and in?vivo performance by means of hydrolytic degradation, muscle pouch implantation, as well as repair the calvarial defects in New Zealand white rabbits. The results demonstrated that the degradable scaffold held good biocompatibility. Qualitative analysis of bone regeneration process was performed by radiological examination and histological analysis. The results indicated that new bone formed originally from the margin of host bone, and then grew toward the center of defects. Moreover, the quantitative determination of newly formed bone was performed using statistical analysis of histological sections at predetermined time points. At 20th week, the defects of treatment group were covered with the new solid cortical bone. In comparison, the control group was filled with a large amount of cancelous bone and bone marrow. It suggested that the composite scaffold had better activity of guided bone regeneration than that of self-healing. So the electrospun PCEC/n-HA fibrous scaffold had the great potential application in bone tissue engineering.     

Electrospun gelatin/poly(L-lactide-co-ε-caprolactone) nanofibers for mechanically functional tissue-engineering scaffolds

Recently, much attention has been given to the fabrication of tissue-engineering scaffolds with nano-scaled structure to stimulate cell adhesion and proliferation in a microenvironment similar to the natural extracellular matrix milieu. In the present study, blends of gelatin and poly(L-lactide-co-ε-caprolactone) (PLCL) (blending ratio: 0, 30, 70 and 100 wt% gelatin to PLCL) were electrospun to prepare nano-structured non-woven fibers for the development of mechanically functional engineered skin grafts. The resulting nanofibers demonstrated the uniform and smooth fibers with mean diameters ranging from approx. 50 to 500 nm with interconnected pores, regardless of the composition. The contact angle decreased with increasing amount of gelatin in the blend and the water content of the nanofibers increased concurrently. PLCL nanofibers retained significant levels of recovery following application of uniaxial stress; GP-3 with 70% PLCL blend returned to the original length within less than 10% of deformation following 200% of uniaxial elongation. The overall tensile strength was inversely affected by increase in the gelatin content and degradation rates of the nanofibers were accelerated as the gelatin concentration increased. When seeded with human primary dermal fibroblasts and keratinocytes on the nanofibers, both initial cell adhesion and proliferation rate increased as a function of the gelatin content in the blend. Additionally, the total cell number was significantly greater on the nanofiber scaffolds than on polymer-coated glasses, indicating that nanofibrous structure facilitates cell proliferation. Taken together, gelatin/PLCL blend nanofiber scaffolds may serve as a promising artificial extracellular matrix for regeneration of mechanically functional skin tissue.     

In vitro and in vivo degradation of non-woven materials made of poly(ε-caprolactone) nanofibers prepared by electrospinning under different conditions

The aim of this study was to prepare non-woven materials from a biodegradable polymer, poly(ε-caprolactone) (PCL) by electrospinning. PCL was synthesized by ring-opening polymerization of ε-caprolactone in bulk using stannous octoate as the catalyst under nitrogen atmosphere. PCL was then processed into non-woven matrices composed of nanofibers by electrospinning of the polymer from its solution using a high voltage power supply. The effects of PCL concentration, composition of the solvent (a mixture of chloroform and DMF with different DMF content), applied voltage and tip–collector distance on fiber diameter and morphology were investigated. The diameter of fibers increased with the increase in the polymer concentration and decrease in the DMF content significantly. Applied voltage and tip–collector distance were found critical to control 'bead' formation. Elongation-at-break, ultimate strength and Young's modulus were obtained from the mechanical tests, which were all increased by increasing fiber diameter. The fiber diameter significantly influenced both in vitro degradation (performed in Ringer solution) and in vivo biodegradation (conducted in rats) rates. In vivo degradation was found to be faster than in vitro. Electrospun membranes were more hydrophobic than PCL solvent-casted ones; therefore, their degradation was a much slower process.     

Electrospun nanofibers of poly(ε-caprolactone)/depolymerized chitosan for respiratory tissue engineering applications

Synthetic grafts comprised of a porous scaffold in the size and shape of the natural tracheobronchial tree, and autologous stem cells have shown promise in the ability to restore the structure and function of a severely damaged airway system. For this specific application, the selected scaffold material should be biocompatible, elicit limited cytotoxicity, and exhibit sufficient mechanical properties. In this research, we developed composite nanofibers of polycaprolactone (PCL) and depolymerized chitosan using the electrospinning technique and assessed the properties of the fibers for its potential use as a scaffold for regenerating tracheal tissue. Water-soluble depolymerized chitosan solution was first prepared and mixed with polycaprolactone solution making it suitable for electrospinning. Morphology and chemical structure analysis were performed to confirm the structure and composition of the fibers. Mechanical testing of nanofibers demonstrated both elastic and ductile properties depending on the ratio of PCL to chitosan. To assess biological potential, porcine tracheobronchial epithelial (PTBE) cells were seeded on the nanofibers with composition ratios of PCL/chitosan: 100/0, 90/10, 80/20, and 70/30. Transwell inserts were modified with the nanofiber membrane and cells were seeded according to air–liquid interface culture techniques that mimics the conditions found in the human airways. Lactase dehydrogenase assay was carried out at different time points to determine cytotoxicity levels within PTBE cell cultures on nanofibers. This study shows that PCL/chitosan nanofiber has sufficient structural integrity and serves as a potential candidate for tracheobronchial tissue engineering.     

Porous crosslinked poly(ε-caprolactone fumarate)/nanohydroxyapatite composites for bone tissue engineering

Porous nanocomposites based on poly(ε-caprolactone fumarate) (PCLF) resin matrix; N-vinyl pyrrolidone (NVP) as a reactive diluents and nanohydroxyapatite (nHA) filler were developed for bone tissue engineering applications. Nanocomposite scaffolds with three different contents of nHA [5, 10, and 20 (w/w %)] were prepared by thermal crosslinking of PCLF followed by particulate leaching and characterized in terms of mechanical properties (cyclic loading) and in vitro cell-material interaction by MTT assay and alkaline phosphatase activity measurements. Five osteoblastic cell lines were used to investigate the ability of the nanocomposites to support cell attachment, spreading, and proliferation after 3, 7, and 14 days. By adding the nHA filler phase, elastic modulus of the nanocomposites increased significantly. Scaffolds showed comparable biocompatibility to neat nHA particles, commercial bone graft (Bio-Oss) and tissue culture polystyrene as control groups. According to the results it can be concluded that these scaffolds are potential candidates for bone substitution because of their mechanical strength and bioactivity.     

Preparation and preliminary in vitro evaluation of a bFGF-releasing heparin-conjugated poly(ε-caprolactone) membrane for guided bone regeneration

In an effort to improve guided bone regeneration (GBR), we successfully fabricated a novel basic fibroblast growth factor (bFGF)-releasing heparin-conjugated poly(ε-caprolactone) membrane (hep-PCL/bFGF). This material has a porous microstructure with smooth and rough pore walls before and after heparinization, respectively. Our FTIR analyses indicated that chemical bonds were formed between PCL and heparin with a new amide C=O band at 1660 cm^?1 and a band at 3400 cm^?1 that can be attributed to –OH stretching in cross-linked heparin. We showed that bFGF was released from hep-PCL/bFGF in a continuous pattern, which remained for 3 weeks. We evaluated MG63 cell proliferation and biocompatibility of GBR membrane by a CCK-8 assay and a live/dead assay. The CCK-8 results revealed that the hep-PCL/bFGF group had superiority compared to other groups. Furthermore, cell morphology of hep-PCL membrane exhibited larger projected areas than those of PCL surfaces based on scanning electron microscopy analysis and immunofluorescent staining of cell cytoskeleton and vinculin expression. Our alkaline phosphatase activity assay also confirmed better performance of the hep-PCL/bFGF group. These results suggested that this novel hep-PCL/bFGF membrane is suitable for osteoblast-like cells to attach, proliferate, and differentiate. Therefore, the hep-PCL/bFGF membrane has potential to be a biodegradable membrane for GBR and warrants further investigation.     

Characterization of electrospun core/shell poly(vinyl pyrrolidone)/poly(L-lactide-co-ε-caprolactone) fibrous membranes and their cytocompatibility in vitro

Coaxial electrospinning is a new technique to fabricate continuous composite ultrafine fibers with core/shell structure, which has a broad application perspective in the biomedical field. In this study, ultrafine fibrous membranes of core/shell poly(vinyl pyrrolidone)/poly(L-lactide-co-ε-caprolactone) (PVP/PLCL) were produced by coaxial electrospinning and the structural morphology of the obtained ultrafine fibers was observed by scanning electron microscopy and transmission electron microscopy. Electrospun PLCL and chitosan membranes were also prepared by traditional electrospinning as controls. The electrospun PVP/PLCL membranes showed the largest water absorption (501.3%) in phosphate buffer solution due to introduction of the PVP component and the core/shell fiber structure. Results of tensile tests indicated that the electrospun PVP/PLCL membranes possessed higher tensile strength and elongation-at-break, and lower Young's modulus than those of PLCL and chitosan membranes in both dry and wet states. Studies on cell adhesion, viability and morphology on the fibrous membranes showed that PVP/PLCL membranes could mimic the structure of natural extracellular matrices and positively promote cell–cell and cell–matrix interactions because of hydrophilicity/hydrophobicity balance.     

Controlled heparin conjugation on electrospun poly(ε-caprolactone)/gelatin fibers for morphology-dependent protein delivery and enhanced cellular affinity

Electrospun fibrous scaffolds have now been shown to possess great potential for tissue engineering applications, owing to their unique mimicry of natural extracellular matrix structure. In this study, poly(ε-caprolactone) and gelatin were electrospun to fabricate tissue-engineered scaffolds with three different fiber morphologies (1.0 μm, 3.0 μm and co-electrospun containing both 1.0 and 3.0 μm diameter fibers). Subsequently, these scaffolds were conjugated with heparin to immobilize a bioactive molecule by electrostatic interactions. This study determined the quantity of heparin conjugation on the scaffolds and that the crosslinking time and the fiber morphologies govern the extent of heparin conjugation on the fibers. In order to evaluate the release capacity of the heparin-conjugated scaffolds, lysozyme was used as a model protein for conjugation. The heparin-conjugated scaffolds provided high loading efficiency and cumulative release of lysozyme with a relatively linear relationship. In addition, the release kinetics was significantly dependent on heparin conjugation and fiber morphology. This fundamental investigation into how fiber morphology and crosslinking protocols can affect the heparin binding ability of electrospun fibers is crucial for predicting the delivery of many different types of bioactive molecules from an electrospun scaffold for tissue engineering applications.     

Porous alginate/poly(ε-caprolactone) scaffolds: preparation, characterization and in vitro biological activity

In bone tissue engineering, scaffolds with controlled porosity are required to allow cell ingrowth, nutrient diffusion and sufficient formation of vascular networks. The physical properties of synthetic scaffolds are known to be dependent on the biomaterial type and its processing technique. In this study, we demonstrate that the separation phase technique is a useful method to process poly(ε-caprolactone) (PCL) into a desired shape and size. Moreover, using poly(ethylene glycol), sucrose, fructose and Ca2+ alginate as porogen agents, we obtained PCL scaffolds with three-dimensional porous structures characterized by different pore size and geometry. Scanning electron microscopy and porosity analysis indicated that PCL scaffolds prepared with Ca2+ alginate threads resemble the porosity and the homogeneous pore size distribution of native bone. In parallel, MicroCT analysis confirmed the presence of interconnected void spaces suitable to guarantee a biological environment for cellular growth, as demonstrated by a biocompatibility test with MC3T3-E1 murine preosteoblastic cells. In particular, scaffolds prepared with Ca2+ alginate threads increased adhesion and proliferation of MC3T3-E1 cells under basal culture conditions, and upon stimulation with a specific differentiation culture medium they enhanced the early and later differentiated cell functions, including alkaline phosphatase activity and mineralized extracellular matrix production. These results suggest that PCL scaffolds, obtained by separation phase technique and prepared with alginate threads, could be considered as candidates for bone tissue engineering applications, possessing the required physical and biological properties.     

Lamellar stack formation and degradative behaviors of hydrolytically degraded poly(ε-caprolactone) and poly(glycolide-ε-caprolactone) blended fibers

Electrospun fibrous mats have gained popularity in bioengineering over the past decade, but few papers detail their degradative mechanisms. To address this, blends of hydrophobic poly(ε-caprolactone) (PCL) and hydrophilic PGA-PCL-PGA triblock copolymer were electrospun into aligned fibrous mats to assess the copolymers' mechanical and degradative properties. Increased hydrophilic triblock content led to enhanced morphological uniformity of fiber, tightening of fiber diameters, increased storage and Young's modulus, and decreased elongation. The corresponding decrease in hydrophobic PCL content led to faster hydrolytic degradation rate, as reflected by enhanced decrease in mass, molecular weight, and modulus loss at 25, 37, and 45°C. The activation energy for hydrolytic degradation for 15:85 PCL: triblock copolymer was approximately half that of 85:15 PCL: triblock copolymer. Detailed examination of fiber morphology and crystallinity revealed initial surface erosion followed by the evolution of crystalline lamellar stacks and bulk degradation at 37°C. Because of the high surface to volume and short diffusion length scale of the small diameter fibers, surface and bulk degradation may both contribute to the hydrolytic degradative behavior of these electrospun fibrous mats. Electrospun mats' distinct architecture that embodies high specific surface to volume and interfiber porous ultrastructures that lead to their unique degradative behaviors hold much potential for significant impact in the field of tissue engineering and controlled drug delivery.     

New poly(ε-caprolactone)/chitosan blend fibers for tissue engineering applications

This study reports for the first time on the production of poly(ε-caprolactone)/chitosan blend fibers for future application as tissue engineering scaffolds. Fibers of chitosan and poly(ε-caprolactone) were prepared by wet spinning from blend solutions, using a formic acid/acetone 70:30 vol.% mixture as common solvent and methanol as coagulant. By this method, blend fibers with a wide compositional range and controllable diameters could be produced. Scanning electron microscopy shows the existence of roughness and porosity at the micron level scale in the blend fiber surface that could be potentially advantageous for cell attachment. Studies were also conducted using both conventional and innovative techniques to evaluate compatibility between the polymers, including FTIR imaging and investigation of the glass transition of chitosan using dynamic mechanical analysis on samples with controlled swelling. The data suggest that a certain degree of interaction exists, although it does not seem to be a result of chemical interaction. The designed fibers could be potentially used for the development of scaffolds for tissue engineering applications.     

Phase transfer and characterization of poly(ε-caprolactone) and poly(L-lactide) microspheres

A method suitable for transfer of poly(ε-caprolactone) and poly(L-lactide) microspheres (synthesized by pseudoanionic dispersion polymerization of ε-caprolactone and L-lactide in heptane1,4-dioxane mixed solvent) from heptane to water was developed. This method consists of treating the microspheres with KOH-ethanol in the presence of surfactants (nonionic Triton X-405, anionic sodium dodecyl sulfate (SDS), and zwitterionic ammonium sulfobetaine-2 (ASB)). Partial hydrolysis of polyesters results in the formation of hydroxyl and carboxyl groups in the surface layer of microspheres and enhances their stability in water-based media. Minimal concentrations of surfactants, needed to obtain stable suspensions of particles, were equal to 3 × 10^-2, and 6 × 10^-2, and 3 × 10^-2 mol l^-1 for Triton X-405, SDS, and ASB, respectively. In the case of poly(ε-caprolactone) microspheres, suspensions in water were stable for all three surfactants for pH values ranging from 3 to 11. Suspensions of poly(L-lactide) were stable in the same range of pH values only for ASB. Surface charge density determined by electrophoretic mobility varied for poly(ε-caprolactone) microspheres from 2.6 × 10^-7 to 8.9 × 10^-7 mol m^-2, for particles stabilized with Triton X-405 and ASB, respectively. In the case of poly(L-lactide) microspheres, surface charge density varied from 3.9 × 10-7 (stabilizer: Triton X-405) to 7.4 × 10^-7 mol m^-2 (stabilizer: ASB). Carboxyl groups located in the surface layer of poly(L-lactide) microspheres were used for covalent immobilization of 6-aminoquinoline, a fluorophore with an amino group. Maximum surface concentration of immobilized 6-aminoquinoline was equal to 1.9 × 10^-6 mol m^-2. Poly(ε-caprolactone) microspheres transferred into water were loaded with ethyl salicylate. Loading up to 38% (w/w) was obtained.     

Preparation and characterization of novel poly(ε-caprolactone)/biphasic calcium phosphate hybrid composite microspheres

Desirably porous biodegradable hybrid composite microspheres were fabricated for use in bone graft and bone substitute applications. In this study, novel poly(ε-caprolactone)/biphasic calcium phosphate (70/30) composite microspheres (PCL/BCP MPs) were prepared using the emulsion solvent-evaporation method. Throughout this process, the ammonium bicarbonate (NH?HCO?) content was changed to obtain the desired porous structure. However, to maintain the spherical shape, the NH?HCO? content should not be higher than 5%. In the optical images of the PCL/BCP MPs, almost all the microparticles had a spherical shape, and the average diameter was about 600 μm. The scanning electron microscopy and cross-sectional optical images showed that the pore density and pore diameter of PCL/BCP MPs increased with increasing initial NH?HCO? concentrations. In the phase-composition analysis of the PCL/BCP MPs, which was characterized by X-ray diffraction and EDS, the two crystals BCP and PCL phases were shown to be miscible in PCL/BCP MPs. When the degradation of these microspheres was characterized, PCL/BCP MPs-0, PCL/BCP MPs-2, and PCL/BCP MPs-5 were found to display a sustained biodegradability, and the rate of degradation increased at higher initial NH?HCO? concentrations. Proliferation of cells on three different sample types was assessed and compared, and based on these results, the PCL/BCP MPs-5 was chosen to study MG-63 osteoblast-cell adhesion, growth, and proliferation. Furthermore, confocal images indicated that the cells effectively adhered, spread, and proliferated on PCL/BCP MPs-5 during a 5-day culture period.     

Chitosan–poly(lactide-co-glycolide) microsphere-based scaffolds for bone tissue engineering: In vitro degradation and in vivo bone regeneration studies

Natural polymer chitosan and synthetic polymer poly(lactide-co-glycolide) (PLAGA) have been investigated for a variety of tissue engineering applications. We have previously reported the fabrication and in vitro evaluation of a novel chitosan/PLAGA sintered microsphere scaffold for load-bearing bone tissue engineering applications. In this study, the in vitro degradation characteristics of the chitosan/PLAGA scaffold and the in vivo bone formation capacity of the chitosan/PLAGA-based scaffolds in a rabbit ulnar critical-sized-defect model were investigated. The chitosan/PLAGA scaffold showed slower degradation than the PLAGA scaffold in vitro. Although chitosan/PLAGA scaffold showed a gradual decrease in compressive properties during the 12-week degradation period, the compressive strength and compressive modulus remained in the range of human trabecular bone. Chitosan/PLAGA-based scaffolds were able to guide bone formation in a rabbit ulnar critical-sized-defect model. Microcomputed tomography analysis demonstrated that successful bridging of the critical-sized defect on the sides both adjacent to and away from the radius occurred using chitosan/PLAGA-based scaffolds. Immobilization of heparin and recombinant human bone morphogenetic protein-2 on the chitosan/PLAGA scaffold surface promoted early bone formation as evidenced by complete bridging of the defect along the radius and significantly enhanced mechanical properties when compared to the chitosan/PLAGA scaffold. Furthermore, histological analysis suggested that chitosan/PLAGA-based scaffolds supported normal bone formation via intramembranous formation.     

Osteogenic differentiation of bone marrow stromal cells on poly(ε-caprolactone) nanofiber scaffolds

Nanofiber poly(ε-caprolactone) (PCL) scaffolds were fabricated by electrospinning, and their ability to enhance the osteoblastic behavior of marrow stromal cells (MSCs) in osteogenic media was investigated. MSCs were isolated from Wistar rats and cultured on nanofiber scaffolds to assess short-term cytocompatibility and long-term phenotypic behavior. Smooth PCL substrates were used as control surfaces. The short-term cytocompatibility results indicated that nanofiber scaffolds supported greater cell adhesion and viability compared with control surfaces. In osteogenic conditions, MSCs cultured on nanofiber scaffolds also displayed increased levels of alkaline phosphatase activity for 3 weeks of culture. Calcium phosphate mineralization was substantially accelerated on nanofiber scaffolds compared to control surfaces as indicated through von Kossa and calcium staining, scanning electron microscopy and energy-dispersive X-ray spectroscopy. Increased levels of intra- and extracellular levels of osteocalcin and osteopontin were observed on nanofiber scaffolds using immunofluorescence techniques after 3 weeks of culture. These results demonstrate the enhanced tissue regeneration property of nanofiber scaffolds, which may be of potential use for engineering osteogenic scaffolds for orthopedic applications.     

Nanostructured poly(ε-caprolactone)–silica xerogel fibrous membrane for guided bone regeneration

A novel fibrous membrane was developed for guided bone regeneration (GBR) through electrospinning a uniform poly(ε-caprolactone) (PCL)–silica hybrid sol. The membrane was composed of fibers with a mean diameter of approximately 400 nm. The hybrid fibers were nano-sized with uniform patterns throughout the fibers, in contrast to the homogeneous structure of pure PCL fibers. The tensile strengths and elastic moduli of the membranes were significantly enhanced with increasing silica content up to 40%. The surfaces of the hybrid membranes were highly hydrophilic with a water contact angle of almost zero. The hybrid membranes possessed excellent in vitro cellular responses in terms of proliferation and differentiation of pre-osteoblast cells. The in vivo animal tests not only confirmed excellent biocompatibility but also revealed bioresorbability of the membranes. These mechanical and biomedical properties make the hybrid membranes very attractive as GBR applications.     

Diaphragmatic muscle reconstruction with an aligned electrospun poly(ε-caprolactone)/collagen hybrid scaffold

Large diaphragmatic muscle defects in congenital diaphragmatic hernia (CDH) are reconstructed by prosthetic materials or autologous grafts, which are associated with high complications and reherniation. In this study we examined the feasibility of using aligned electrospun poly(ε-caprolactone) (PCL)/collagen hybrid scaffolds for diaphragmatic muscle reconstruction. The hybrid scaffolds were implanted into a central left hemi-diaphragmatic defect (approximately 70% of the diaphragmatic tissue on the left side) in rats. Radiographic and magnetic resonance imaging (MRI) analyses showed no evidence of herniation or retraction up to 6 months after implantation. Histological and immunohistochemical evaluations revealed ingrowth of muscle tissue into the scaffolds. The mechanical properties of the retrieved diaphragmatic scaffolds were similar to those of normal diaphragm at the designated time points. Our results show that the aligned electrospun hybrid scaffolds allowed muscle cell migration and tissue formation. The aligned scaffolds may provide implantable functional muscle tissues for patients with diaphragmatic muscle defects.     

Fabrication and characterization of chitosan/OGP coated porous poly(ε-caprolactone) scaffold for bone tissue engineering

As one of the stimulators on bone formation, osteogenic growth peptide (OGP) improves both proliferation and differentiation of the bone cells in vitro and in vivo. The aim of this work was the preparation of three dimensional porous poly(ε-caprolactone) (PCL) scaffold with high porosity, well interpore connectivity, and then its surface was modified by using chitosan (CS)/OGP coating for application in bone regeneration. In present study, the properties of porous PCL and CS/OGP coated PCL scaffold, including the microstructure, water absorption, porosity, hydrophilicity, mechanical properties, and biocompatibility in vitro were investigated. Results showed that the PCL and CS/OGP-PCL scaffold with an interconnected network structure have a porosity of more than 91.5, 80.8%, respectively. The CS/OGP-PCL scaffold exhibited better hydrophilicity and mechanical properties than that of uncoated PCL scaffold. Moreover, the results of cell culture test showed that CS/OGP coating could stimulate the proliferation and growth of osteoblast cells on CS/OGP-PCL scaffold. These finding suggested that the surface modification could be a effective method on enhancing cell adhesion to synthetic polymer-based scaffolds in tissue engineering application and the developed porous CS/OGP-PCL scaffold should be considered as alternative biomaterials for bone regeneration.     

Hollow fibers of poly(lactide-co-glycolide) and poly(ε-caprolactone) blends for vascular tissue engineering applications

At present the manufacture of small-diameter blood vessels is one of the main challenges in the field of vascular tissue engineering. Currently available vascular grafts rapidly fail due to development of intimal hyperplasia and thrombus formation. Poly(lactic-co-glycolic acid) (PLGA) hollow fiber (HF) membranes have previously been proposed for this application, but as we show in the present work, they have an inhibiting effect on cell proliferation and rather poor mechanical properties. To overcome this we prepared HF membranes via phase inversion using blends of PLGA with poly(ε-caprolactone) (PCL). The influence of polymer composition on the HF physicochemical properties (topography, water transport and mechanical properties) and cell attachment and proliferation were studied. Our results show that only the ratio PCL/PLGA of 85/15 (PCL/PLGA85/15) yielded a miscible blend after processing. A higher PLGA concentration in the blend led to immiscible PCL/PLGA phase-separated HFs with an inhomogeneous morphology and variation in the cell culture results. In fact, the PCL/PLGA85/15 blend, which had the most homogeneous morphology and suitable pore structure, showed better human adipose stem cell (hASC) attachment and proliferation compared with the homopolymers. This, combined with the good mechanical and transport properties, makes them potentially useful for the development of small-caliber vascular grafts.     

In vivo biocompatibility and biodegradation of 3D-printed porous scaffolds based on a hydroxyl-functionalized poly(ε-caprolactone)

The aim of this study was to evaluate the in vivo biodegradation and biocompatibility of three-dimensional (3D) scaffolds based on a hydroxyl-functionalized polyester (poly(hydroxymethylglycolide-co-ε-caprolactone), PHMGCL), which has enhanced hydrophilicity, increased degradation rate, and improved cell-material interactions as compared to its counterpart poly(ε-caprolactone), PCL. In this study, 3D scaffolds based on this polymer (PHMGCL, HMG:CL 8:92) were prepared by means of fiber deposition (melt-plotting). The biodegradation and tissue biocompatibility of PHMGCL and PCL scaffolds after subcutaneous implantation in Balb/c mice were investigated. At 4 and 12 weeks post implantation, the scaffolds were retrieved and evaluated for extent of degradation by measuring the residual weight of the scaffolds, thermal properties (DSC), and morphology (SEM) whereas the polymer was analyzed for both its composition ((1)H NMR) and molecular weight (GPC). The scaffolds with infiltrated tissues were harvested, fixed, stained and histologically analyzed. The in vitro enzymatic degradation of these scaffolds was also investigated in lipase solutions. It was shown that PHMGCL 3D-scaffolds lost more than 60% of their weight within 3 months of implantation while PCL scaffolds showed no weight loss in this time frame. The molecular weight (M(w)) of PHMGCL decreased from 46.9 kDa before implantation to 23.2 kDa after 3 months of implantation, while the molecular weight of PCL was unchanged in this period. (1)H NMR analysis showed that the degradation of PHMGCL was characterized by a loss of HMG units. In vitro enzymatic degradation showed that PHMGCL scaffolds were degraded within 50 h, while the degradation time for PCL scaffolds of similar structure was 72 h. A normal foreign body response to both scaffold types characterized by the presence of macrophages, lymphocytes, and fibrosis was observed with a more rapid onset in PHMGCL scaffolds. The extent of tissue-scaffold interactions as well as vascularization was shown to be higher for PHMGCL scaffolds compared to PCL ones. Therefore, the fast degradable PHMGCL which showed good biocompatibility is a promising biomaterial for tissue engineering applications.