Morphology,wettability, and mechanical properties of polycaprolactone/hydroxyapatite composite scaffolds with interconnected pore structures fabricated by a mini‐deposition system

A new mini‐deposition system (MDS) was developed to fabricate scaffolds with interconnected pore structures and anatomical geometry for bone tissue engineering. Polycaprolactone/hydroxyapatite (PCL/HA) composites with varying hydroxyapatite (HA) content were adopted to manufacture scaffolds by using MDS with a porosity of 54.6%, a pore size of 716 μm in the x‐y plane, and 116 μm in the z direction. The water uptake ratio and compressive modulus of PCL/HA composite scaffold increase from 8 to 39% and from 26.5 to 49.8 MPa, respectively, as the HA content increases from 0 to 40%. PCL/HA composite scaffolds have better wettability and mechanical properties than pure PCL scaffold. A PCL/HA composite scaffold for mandible bone repair was successfully fabricated with both interconnected pore structures and anatomical shape to demonstrate the versatility of MDS. POLYM. ENG. SCI., 2012. © 2012 Society of Plastics Engineers     

Effect of PCL concentration on PCL/CaSiO3 porous composite scaffolds for bone engineering

Porous polycaprolactone (PCL)-coated calcium silicate (CaSiO₃) composite scaffolds were successfully prepared by 3D gel-printing (3DGP) and vacuum impregnation technology in this study. The effect of different PCL concentration on porous CaSiO₃ scaffolds prepared by 3DGP technology was studied. The composition and morphological characteristics of PCL/CaSiO₃ scaffolds were tested by using fourier transform infrared spectroscopy (FTIR), scanning electron microscope (SEM), and energy dispersive spectrometer (EDS) analysis. PCL coating amount on the scaffolds surface was calculated by thermogravimetric analysis (TGA). Compressive strength was tested by a universal testing machine, and degradability was tested by immersing the scaffolds in a simulated body fluid (SBF). The results show that PCL coating thickness increased from 7.29 μm to 12.2 μm, and the compressive strength of the corresponding composite scaffolds increased from 17.15 MPa to 24.12 MPa following with PCL concentration increasing from 7.5% to 12.5%. When the porous composite scaffolds were immersed in SBF for 28 days, the degradation ratio was 1.06% (CaSiO₃), 1.63% (CaSiO₃-7.5PCL), 1.81% (CaSiO₃-10PCL) and 1.55% (CaSiO₃-12.5PCL), respectively. It is obviously that PCL/CaSiO₃ composite scaffolds, which are suitable for bone growth in bone repair engineering, are beneficial to improve the mechanical properties and biodegradability of pure CaSiO₃ scaffolds.     

Ultraporous poly(lactic acid) scaffolds with improved mechanical performance using high‐pressure molding and salt leaching

A novel processing technique, i.e. high‐pressure compression molding/salt leaching, was developed to fabricate ultraporous poly(lactic acid) (PLA) scaffolds. The optimized composition was studied in relation to the porosity, pore morphology, thermal property, and mechanical performance of the PLA scaffolds. At a porogen (CaCO₃) content of 90 wt %, the scaffolds have an interconnected open pore structure and a porosity above 80%. It was truly interesting that the structural stability of high‐pressure molded scaffolds was remarkably improved based on the fact that its glass transition temperature (83.5°C) increased about 20°C, as compared to that of the conventional compression‐molded PLA (60°C), which is not far from physiological temperature (～37°C) at the risk of structural relaxation or physical aging. More importantly, the mechanical performance of PLA scaffolds was drastically enhanced under optimized processing conditions. At pressure and temperature of 1000 MPa and 190°C, the porous PLA scaffolds attained a storage modulus of 283.7 MPa, comparable to the high‐end value of trabecular bone (250 MPa) ever reported. In addition, our prepared PLA scaffolds showed excellent cellular compatibility and biocompatibility in vitro tests, further suggesting that the high‐pressure molded PLA scaffolds have high potential for bone tissue engineering applications. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 3509–3520, 2013     

Fabrication and Evaluation of Polycaprolactone–Poly(hydroxybutyrate) or Poly(3‐Hydroxybutyrate‐co‐3‐Hydroxyvalerate) Dual‐Leached Porous Scaffolds for Bone Tissue Engineering Applications

Polycaprolactone (PCL) blend with poly(hydroxybutyrate) (PHB) or poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate) (PHBV) dual‐leached scaffolds are prepared by using the solvent casting and salt–polymer‐leaching technique. The blending of the PHB and PHBV in PCL scaffolds results in decreased porosities of the scaffolds, and the water absorption capacities of the scaffolds also decrease. The compressive modulus of the PCL–PHB and PCL–PHBV dual‐leached scaffolds is greatly increased by the blending of PHB or PHBV matrix. An indirect cytotoxicity evaluation of all scaffolds with mouse fibroblastic cells (L929) and mouse calvaria‐derived preosteoblastic cell (MC3T3‐E1) indicates that all dual‐leached scaffolds are posed as nontoxic to cells. Both PCL–PHB and PCL–PHBV dual‐leached scaffolds are supported by the attachment of MC3T3‐E1 at significantly higher levels to tissue culture polystyrene plate (TCPS) and are able to support the proliferation of MC3T3‐E1 at higher levels to that cells on TCPS and PCL scaffolds. For mineralization, cells cultured on surfaces of PCL–PHB and PCL–PHBV dual‐leached scaffolds show higher mineral deposition than on TCPS and PCL scaffold.

     

Reinforcement of electrospun poly(ε‐caprolactone) scaffold using diopside nanopowder to promote biological and physical properties

Considerable efforts have been devoted toward the development of electrospun scaffolds based on poly(ε‐caprolactone) (PCL) for bone tissue engineering. However, most of previous scaffolds have lacked the structural and mechanical strength to engineer bone tissue constructs with suitable biological functions. Here, we developed bioactive and relatively robust hybrid scaffolds composed of diopside nanopowder embedded PCL electrospun nanofibers. Incorporation of various concentrations of diopside nanopowder from 0 to 3 wt % within the PCL scaffolds notably improved tensile strength (eight‐fold) and elastic modulus (two‐fold). Moreover, the addition of diopside nanopowder significantly improved bioactivity and degradation rate compared to pure PCL scaffold which might be due to their superior hydrophilicity. We investigated the proliferation and spreading of SAOS‐II cells on electrospun scaffolds. Notably, electrospun PCL‐diopside scaffolds induced significantly enhanced cell proliferation and spreading. Overall, we concluded that PCL‐diopside scaffold could potentially be used to develop clinically relevant constructs for bone tissue engineering. However, the extended in vivo studies are essential to evaluate the role of PCL‐diopside fibrous scaffolds on the new bone growth and regeneration. Therefore, in vivo studies will be the subject of our future work. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134 , 44433.     

Fabrication of LaCl3‐containing nanofiber scaffolds and their application in skin wound healing

Poly(?‐caprolactone) (PCL)/gelatin (GE) nanofiber scaffolds with varying concentrations of lanthanum chloride (LaCl₃, from 0 to 25 mM) were fabricated by electrospinning. The scaffolds were characterized by scanning electron microscopy, contact angle and porosity measurements, mechanical strength tests, and in vitro degradation studies. In vitro cytotoxicity and cell adhesion and proliferation studies were performed to assess the biocompatibility of the scaffolds, and in vivo wound healing studies were conducted to assess scaffold applications in the clinic. All prepared scaffolds were noncytotoxic, and the growth of adipose tissue–derived stem cells on LaCl₃‐containing scaffolds was better than on the pure PCL/GE scaffold. Cell proliferation studies showed the greatest cell growth in the PCL/GE/LaCl₃ scaffolds. Further, in vivo studies proved that the PCL/GE/LaCl₃ scaffolds can promote wound healing. The results suggest that nanofiber scaffolds containing LaCl₃ promote cell proliferation and have good biocompatibility, and thus potential for application in the treatment of skin wounds. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46672.     

Preparation and characterization of polylactide‐block‐poly(butylene adipate) polyurethane thermoplastic elastomer

Polylactide‐block‐poly(butylene adipate) poly(ester‐urethane) (PLAEU) thermoplastic elastomer was obtained by melt chain extending reaction with polylactide‐block‐poly(butylene adipate)‐block‐polylactide (PBLA) and hexamethylene diisocyanate (HDI). PBLA was previously prepared with L ‐lactide and poly(butylene adipate) diol (PBA diol). Experimental parameters including feed ratio, polymerization temperature, and time were optimized. The weight average molecular weight (M_w) of PLAEU surpassed 10⁵ g/mol. In contrast to corresponding PBLA, the crystallinity and melt temperature (T_m) of PLAEU decreased, whereas its glass transition (T_g) shifted to high temperature due to the “pseudoextension” structure of polylactide (PLA) block. Additionally, the crystallinity and T_m of PLAEU were subject to crystallization method and molecular weight. The tensile strength of PLAEU varied from 6.61 to 24.41 MPa and elongation from 190% to 780%. Therefore, the mechanical properties of PLAEU can be regulated by altering the length ratio of PLA to PBA block. The high elasticity of PLAEU can be explained with phase separation mechanism. POLYM. ENG. SCI., 2011. © 2011 Society of Plastics Engineers     

Polylactide toughening with epoxy‐functionalized grafted acrylonitrile–butadiene–styrene particles

Glycidyl methacrylate functionalized acrylonitrile–butadiene–styrene (ABS‐g‐GMA) particles were prepared and used to toughen polylactide (PLA). The characteristic absorption at 1728 cm^?1 of the Fourier transform infrared spectra indicated that glycidyl methacrylate (GMA) was grafted onto the polybutadiene phase of acrylonitrile–butadiene–styrene (ABS). Chemical reactions analysis indicated that compatibilization and crosslinking reactions took place simultaneously between the epoxy groups of ABS‐g‐GMA and the end carboxyl or hydroxyl groups of PLA and that the increase of GMA content improved the reaction degree. Scanning electron microscopy results showed that 1 wt % GMA was sufficient to satisfy the compatibilization and that ABS‐g‐GMA particles with 1 wt % GMA dispersed in PLA uniformly. A further increase of GMA content induced the agglomeration of ABS‐g‐GMA particles because of crosslinking reactions. Dynamic mechanical analysis testing showed that the miscibility between PLA and ABS improved with the introduction of GMA onto ABS particles because of compatibilization reactions. The storage modulus decreased for the PLA blends with increasing GMA content. The decrease in the storage modulus was due to the chemical reactions in the PLA/ABS‐g‐GMA blends, which improved the viscosity and decreased the crystallization of PLA. A notched impact strength of 540 J/m was achieved for the PLA/ABS‐g‐GMA blend with 1 wt % GMA, which was 27 times than the impact strength of pure PLA, and a further increase in the GMA content in the ABS‐g‐GMA particles was not beneficial to the toughness improvement. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Electrospun polylactide/silk fibroin–gelatin composite tubular scaffolds for small‐diameter tissue engineering blood vessels

Many synthetic scaffolds have been used as vascular substitutes for clinical use. However, many of these scaffolds may not show suitable properties when they are exposed to physiologic vascular environments, and they may fail eventually because of some unexpected conditions. Electrospinning technology offers the potential for controlling the composition, structure, and mechanical properties of scaffolds. In this study, a tubular scaffold (inner diameter = 4.5 mm) composed of a polylactide (PLA) fiber outside layer and a silk fibroin (SF)–gelatin fiber inner layer (PLA/SF–gelatin) was fabricated by electrospinning. The morphological, biomechanical, and biological properties of the composite scaffold were examined. The PLA/SF–gelatin composite tubular scaffold possessed a porous structure; the porosity of the scaffold reached 82 ± 2%. The composite scaffold achieved the appropriate breaking strength (1.28 ± 0.21 MPa) and adequate pliability (elasticity up to 41.11 ± 2.17% strain) and possessed a fine suture retention strength (1.07 ± 0.07 N). The burst pressure of the composite scaffold was 111.4 ± 2.6 kPa, which was much higher than the native vessels. A mitochondrial metabolic assay and scanning electron microscopy observations indicated that both 3T3 mouse fibroblasts and human umbilical vein endothelial cells grew and proliferated well on the composite scaffold in vitro after they were cultured for some days. The PLA/SF–gelatin composite tubular scaffolds presented appropriate characteristics to be considered as candidate scaffolds for blood vessel tissue engineering. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Development of fibrin conjugated chitosan/nano β‐TCP composite scaffolds with improved cell supportive property for bone tissue regeneration

In the present study, an attempt has been made to improve cell supportive property of chitosan/nano beta tri‐calcium phosphate (β‐TCP) composite scaffolds by modification of scaffold surface with fibrin using ethyl‐3‐(3‐dimethylaminopropyl) carbodimide (EDC) as crosslinking agent. The developed fibrin conjugated chitosan/nano β‐TCP composite scaffolds possess desired pore size and porosity in the range of 45–151 µm and 81.4 ± 4.1%, respectively. No significant change in compressive strength of scaffolds was observed before and after fibrin conjugation. The calculated compressive strength of fibrin conjugated and non‐conjugated chitosan/nano β‐TCP scaffolds are 2.71 ± 0.14 MPa and 2.67 ± 0.11 MPa, respectively. Results of cell culture study have further shown an enhanced cell attachment, cell number, proliferation, differentiation, and mineralization on fibrin conjugated chitosan/nano β‐TCP scaffold. The uniform cell distribution over the scaffold surface and cell infiltration into the scaffold pores were assessed by confocal laser scanning microscopy. Furthermore, higher expression of osteogenic specific genes such as bone sialo protein, osteonectin, alkaline phosphatase, and osteocalcin (OC) on fibrin conjugated scaffolds was observed when compared to scaffolds without fibrin. Altogether, results indicate the potentiality of developed fibrin conjugated composite scaffolds for bone tissue engineering applications. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41534.     

Fabrication of composition-graded collagen/chitosan–polylactide scaffolds with gradient architecture and properties

Chitosan–polylactide (CH–PLA) copolymers with various polylactide percentages changing from around 14 to 40 wt% were synthesized. CH–PLAs were then blended with type-II collagen to fabricate layered collagen/CH–PLA scaffolds that are potentially suitable for the applications in articular cartilage repair. Based on combinatorial processing techniques involving layer-superposition, thermal melting and freeze-drying, two types of stratified collagen/CH–PLA scaffolds were built. The content of collagen inside the scaffolds altered from the top layer to the bottom layer in a trend contrary to that of chitosan. One of them was fabricated using tripolyphosphate (TPP) as a single crosslinker and another type of scaffold was constructed via a dual-crosslinking pathway using TPP and genipin as two crosslinkers in a designated order. These collagen/CH–PLA scaffolds were found to have graded average pore-size and porosity, gradient swelling index and layer-dependent compressive modulus. The resulting scaffolds were thus partially similar to the articular cartilage extracellular matrix in composition, structure and property. In vitro cell culture on some optimized collagen/CH–PLA scaffolds for a period of time up to 3 weeks showed that the scaffolds were able to well support the growth of the seeded cells, suggesting that these collagen/CH–PLA scaffolds have promising potential for articular cartilage repair.     

Bone morphogenetic protein‐2 immobilization on porous PCL‐BCP‐Col composite scaffolds for bone tissue engineering

The objective of this study was to develop novel porous composite scaffolds for bone tissue engineering through surface modification of polycaprolactone–biphasic calcium phosphate‐based composites (PCL–BCP). PCL–BCP composites were first fabricated with salt‐leaching method followed by aminolysis. Layer by layer (LBL) technique was then used to immobilize collagen (Col) and bone morphogenetic protein (BMP‐2) on PCL–BCP scaffolds to develop PCL–BCP–Col–BMP‐2 composite scaffold. The morphology of the composite was examined by scanning electron microscopy (SEM). The efficiency of grafting of Col and BMP‐2 on composite scaffold was measured by X‐ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR). Both XPS and FTIR confirmed that Col and BMP‐2 were successfully immobilized into PCL–BCP composites. MC3TC3‐E1 preosteoblasts cells were cultivated on composites to determine the effect of Col and BMP‐2 immobilization on cell viability and proliferation. PCL–BCP–Col–BMP‐2 showed more cell attachment, cell viability, and proliferation bone factors compared to PCL–BCP‐Col composites. In addition, in vivo bone formation study using rat models showed that PCL–BCP–Col–BMP‐2 composites had better bone formation than PCL–BCP‐Col scaffold in critical size defect with 4 weeks of duration. These results suggest that PCL–BCP–Col–BMP‐2 composites can enhance bone regeneration in critical size defect in a rat model with 4 weeks of duration. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45186.     

Mechanical and thermal flow properties of wood flour–biodegradable polymer composites

Wood flour (WF)–polycaprolactone (PCL) and polybutylenesuccinate–butylenecarbonate (PBSC) composites were prepared by knead processing. The effects of a compatibilizer on the tensile and thermal flow properties of the composites were investigated. PCL‐graft‐maleic anhydride (PCL‐g‐MA) was used as a compatibilizer. Tensile properties were improved by adding PCL‐g‐MA to both composites. The tensile strength and Young's modulus were increased from 13 to 27 MPa and 581 to 1011 MPa in WF–PCL (50/50, w/w) composites, respectively, and from 17 to 28 MPa and 814 to 1007 Mpa in WF–PBSC (50/50, w/w) composites, respectively, with the addition of 5% PCL‐g‐MA. Elongation at break increased from 4 to 7% and from 3 to 6% in the WF–PCL and the WF–PBSC composites, respectively. Tensile strength was further increased with increasing WF content in the presence of PCL‐g‐MA. Thermal flow temperature and melt viscosity of the composites were increased, and water absorption and thickness swelling were improved with the addition of PCL‐g‐MA. It was found from the burial test that all composites were more than 40% degraded within 6 weeks, and there was no considerable difference in degradation between composites with PCL‐g‐MA and those without. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 1900–1905, 2003     

Evaluation of the chondrogenic differentiation of mesenchymal stem cells on hybrid biomimetic scaffolds

Hybrid materials are widely and promisingly used as scaffolds in cartilage tissue remodeling. In this study, hybrid scaffolds consist of polycaprolactone (PCL), poly(vinyl alcohol) (PVA) with/without gelatin (GEL) to mimic natural cartilage extracellular matrix (ECM) were investigated. Scaffolds were prepared by freeze drying and characterized by scanning electron microscopy and compressive mechanical testing. Biological assays of mesenchymal stem cell (MSC) cultures, 3‐(4,5‐dimethylthiazol‐2‐yl)‐2,5‐diphenyltetrazolium bromide, and dimethyl methylene blue were performed, and real‐time polymerization chain reaction analysis of the cartilage‐specific ECM gene marker expression was done. The results show an open interconnected porous structure with a compression modulus of 1.27 ± 0.04 MPa. The surface of the scaffolds showed an excellent efficiency in the adhesion and proliferation of MSCs. A significant increase in the proteoglycan content from 3.70 ± 0.96 to 5.4 ± 1.13 μg/mL was observed after 14 days in the PCL–PVA–GEL scaffolds. The expression amount of the sex‐determining region Y–Box 9 (SOX9) and collagen II (COL2) mRNA levels of the MSCs showed significant increases in SOX9 and COL2, respectively in comparison with PCL–PVA scaffold. The study revealed that the aforementioned scaffold as a blend of natural and synthetic polymers may be a promising substrate in tissue engineering for cartilage repair with MSC transplantation. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40635.     

Toward environment‐friendly composites of poly(ε‐caprolactone) reinforced with stereocomplex‐type poly(l‐lactide)/poly(d‐lactide)

In this work, stereocomplex‐poly(l ‐ and d ‐lactide) (sc‐PLA) was incorporated into poly(ε‐caprolactone) (PCL) to fabricate a novel biodegradable polymer composite. PCL/sc‐PLA composites were prepared by solution casting at sc‐PLA loadings of 5–30 wt %. Differential scanning calorimetry (DSC) and wide‐angle X‐ray diffraction (WAXD) demonstrated the formation of the stereocomplex in the blends. DSC and WAXD curves also indicated that the addition of sc‐PLA did not alter the crystal structure of PCL. Rheology and mechanical properties of neat PCL and the PCL/sc‐PLA composites were investigated in detail. Rheological measurements indicated that the composites exhibited evident solid‐like response in the low frequency region as the sc‐PLA loadings reached up to 20 wt %. Moreover, the long‐range motion of PCL chains was highly restrained. Dynamic mechanical analysis showed that the storage modulus (E′) of PCL in the composites was improved and the glass transition temperature values were hardly changed after the addition of sc‐PLA. Tensile tests showed that the Young's modulus, and yield strength of the composites were enhanced by the addition of sc‐PLA while the tensile strength and elongation at break were reduced. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40208.     

Predictors of glass transition in the biodegradable poly‐lactide and poly‐lactide‐co‐glycolide polymers

The biodegradable polylactide (PLA) and polylactide‐co‐glycolides (PLGAs) are being widely investigated for use as scaffolds in bone and ligament reconstruction. The glass transition temperatures (T_g) for these polymers are generally greater than 37°C, causing PLA and PLGA devices to possess brittle characteristics in physiological conditions. To evaluate the possibility of obtaining PLGA polymers with T_g values below 37°C, we evaluated the determinants of T_g in PLA and PLGA copolymers. The T_g, changes in specific heat capacity (ΔC_p), and enthalpic relaxation (ΔH_g) in two consecutive heating cycles were correlated with lactide/glycolide content and intrinsic viscosity [η] for PLA, PLGAs 90:10, 75:25, 65:35, and 50:50. A linear correlation was observed between T_g and intrinsic viscosity, with 0.1 dL/g increase in viscosity resulting in an increase in T_g by about 3.55°C. The selection of PLA and PLGA copolymers with [η] values <0.19 dL/g, corresponding to a viscosity average molecular weight of <70 kDa, will obtain PLA/PLGA polymers with T_g values below 37°C. The lowest attainable T_g values were found to be 28–30°C. Intrinsic viscosity also correlated with ΔC_p differences between aged and rapidly cooled polymers, and is therefore important in predicting free volume changes within these polymers upon aging. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 1983–1987, 2006     

Effects of micro and nano β‐TCP fillers in freeze‐gelled chitosan scaffolds for bone tissue engineering

Tissue engineering holds an exciting promise in providing a long‐term cure to bone‐related defects and diseases. However, one of the most important prerequisites for bone tissue engineering is an ideal platform that can aid tissue genesis by having biomimetic, mechanostable, and cytocompatible characteristics. Chitosan (CS) was chosen as the base polymer to incorporate filler, namely beta‐tri calcium phosphate (β‐TCP). This research deals with a comparative study on the properties of CS scaffolds prepared using micro‐ and nano‐sized β‐TCP as filler by freeze gelation method. The scaffolds were characterized for their morphology, porosity, swelling, structural, chemical, biodegradation, and bioresorption properties. Rheological behavior of polymer and polymer‐ceramic composite suspensions were analyzed and all the suspensions with varying ratios of β‐TCP showed non‐Newtonian behavior with shear thinning property. Pore size, porosity of micro‐ and nano‐sized composite scaffolds are measured as 48–158 μm and 77% and 43–155 μm and 81%, respectively. The scaffolds containing nano β‐TCP possess higher compressive strength (～2.67 MPa) and slower degradation rate as compared to composites prepared with micro‐sized β‐TCP (～1.52 MPa). Bioresorbability, in vitro cell viability by 3‐(4,5‐dimethylthiazol‐2‐yl)‐2,5‐diphenyltetrazolium bromide (MTT) assay, proliferation by Alamar blue assay, cell interaction by scanning electron microscope, and florescence microscopy further validates the potentiality of freeze‐gelled CS/β‐TCP composite scaffolds for bone tissue engineering applications. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 41025.     

Fabrication of a poly(ɛ‐caprolactone)/starch nanocomposite scaffold with a solvent‐casting/salt‐leaching technique for bone tissue engineering applications

A series of nanocomposite scaffolds of poly(?‐caprolactone) (PCL) and starch with a range of porosity from 50 to 90% were fabricated with a solvent‐casting/salt‐leaching technique, and their physical and mechanical properties were investigated. X‐ray diffraction patterns and Fourier transform infrared spectra confirmed the presence of the characteristic peaks of PCL in the fabricated scaffolds. Microstructure studies of the scaffolds revealed a uniform pore morphology and structure in all of the samples. The experimental measurements showed that the average contact angle of the PCL/starch composite was 88.05 ± 1.77°. All of the samples exhibited compressive stress/strain curves similar to those of polymeric foams. The samples with 50, 60, 70, and 80 wt % salt showed compressive‐load‐resisting capabilities in the range of human cancellous bone. With increasing porosity, a significant decrease in the mechanical properties of the scaffolds was observed. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43523.     

Crystallization,morphology, and mechanical behavior of polylactide/poly(ε‐caprolactone) blends

Optically pure polylactides, poly(L ‐lactide) (PLLA) and poly(D ‐lactide) (PDLA), were blended across the range of compositions with poly(ε‐caprolactone) (PCL) to study their crystallization, morphology, and mechanical behavior. Differential scanning calorimetry and dynamic mechanical analysis (DMA) of the PLA/PCL blends showed two T_gs at positions close to the pure components revealing phase separation. However, a shift in the tan δ peak position by DMA from 64 to 57°C suggests a partial solubility of PCL in the PLA‐rich phase. Scanning electron microscopy reveals phase separation and a transition in the phase morphology from spherical to interconnected domains as the equimolar blend approaches from the outermost compositions. The spherulitic growth of both PLA and PCL in the blends was followed by polarized optical microscopy at 140 and 37°C. From tensile tests at speed of 50 mm/min Young's modulus values between 5.2 and 0.4 GPa, strength values between 56 and 12 MPa, and strain at break values between 1 and 400% were obtained varying the blend composition. The viscoelastic properties (E′ and tan δ) obtained at frequency of 1 Hz by DMA are discussed and are found consistent with composition, phase separation, and crystallization behavior of the blends. POLYM. ENG. SCI., 46:1299–1308, 2006. © 2006 Society of Plastics Engineers     

Three​-dimensional porous poly(ε-caprolactone)/beta-tricalcium phosphate microsphere-aggregated scaffold for bone tissue engineering

In this study, porous scaffolds made of polycaprolactone (PCL)/β-tricalcium phosphate (BTCP) biocomposite were fabricated for bone tissue engineering (BTE) applications. The microsphere-aggregated scaffolds were prepared with various BTCP concentrations (10wt%, 20wt%, 50wt%) by the freeze-drying method. The porosity of obtained microsphere-aggregated scaffolds with various pore sizes was 80–85%, where this value was about 70% for the PCL/BTCP (50) sample with no microsphere formation. The results indicated that adding BTCP has enhanced mechanical strength, and the mineralization of PCL/BTCP composite scaffolds has been increased compared to the pure PCL scaffolds in simulated body fluid (SBF). The adhesion and proliferation of mouse bone marrow mesenchymal stem cells (mMSCs) seeded onto PCL/BTCP scaffolds were enhanced compared to the PCL. In addition, in terms of differentiation, the incorporation of BTCP led to increasing the mineral deposition and alkaline phosphatase activity of mMSCs. The synergistic effect of using microsphere-aggregated scaffolds along with BTCP as a reinforcing agent in PCL biocomposite showed that these porous biocomposite scaffolds have the potential application in BTE.