Valve leaflet‐inspired elastomeric scaffolds with tunable and anisotropic mechanical properties

Fibrous scaffolds, which can mimic the elastic and anisotropic mechanical properties of native tissues, hold great promise in recapitulating the native tissue microenvironment. We previously fabricated electrospun fibrous scaffolds made of hybrid synthetic elastomers (poly(1,3‐diamino‐2‐hydroxypropane‐co‐glycerol sebacate)‐co‐poly (ethylene glycol) (APS‐co‐PEG) and polycaprolactone (PCL)) to obtain uniaxial mechanical properties similar to those of human aortic valve leaflets. However, conventional electrospinning process often yields scaffolds with random alignment, which fails to recreate the anisotropic nature of most of the soft tissues such as native heart valves. Inspired by the structure of native valve leaflet, we designed a novel valve leaflet‐inspired ring‐shaped collector to modulate the electrospun fiber alignment and studied the effect of polymer formulation (PEG amount [mole %] in APS‐co‐PEG; ratio between APS‐co‐PEG and PCL; and total polymer concentration) in tuning the biaxial mechanical properties of the fibrous scaffolds. The fibrous scaffolds collected on the ring‐shaped collector displayed anisotropic biaxial mechanical properties, suggesting that their biaxial mechanical properties are closely associated with the fiber alignment in the scaffold. Additionally, the scaffold stiffness was easily tuned by changing the composition and concentration of the polymer blend. Human valvular interstitial cells (hVICs) cultured on these anisotropic scaffolds displayed aligned morphology as instructed by the fiber alignment. Overall, we generated a library of biologically relevant fibrous scaffolds with tunable mechanical properties, which will guide the cellular alignment.     

Polycaprolactone-polymethyl methacrylate electrospun blends for biomedical applications

Electrospinning is one of most versatile process to fabricate porous scaffolds in biomedical field. Synthetic polymers such as polycaprolactone (PCL) and polymethyl methacrylate (PMMA) provide excellent properties for biomedical applications due to their biocompatibility and tunable mechanical properties. PCL-PMMA electrospun blends combine compressive/tensile properties of individual polymers as well as biocompatibility/biodegradability. Together with porosity of scaffold, drug/nutrient supply is required in tissue regeneration and healing. High pressure CO₂ has been investigated to plasticize many biopolymers and impregnate drugs in scaffolds. This study explores several compositions of PCL-PMMA electrospun scaffolds for morphological and mechanical properties. These scaffolds are impregnated with hydrophilic (Rhodamine B) and hydrophobic (Fluorescein) dyes using high pressure CO₂ and air plasma treatment. Furthermore, release profiles of dyes have been studied from thin films and porous scaffolds to understand several controlling factors for controlled release applications. Results show dye-polymer interactions, CO₂ impregnation and stress relaxation of electrospun fibers are key factors in release profile from electrospun fibers. This study is a step forward in developing PCL-PMMA based electrospun scaffolds for drug delivery and tissue engineering.     

Synthesis of PCL‐branched P(MMA‐co‐HEMA) to toughen electrospun PLLA fiber membrane

Electrospun biodegradable fiber mesh is a promising alternative scaffold for delivering progenitor cells for repairing damaged or diseased tissue, but its cripple mechanical stability has not met the requirement of tissue engineering yet. In this work, the well‐defined poly(ε‐caprolactone)‐branched poly(methyl methacrylate‐co‐hydroxyethylmethacrylate) (PCL‐PMH) has been successfully synthesized to toughen electrospun poly(l ‐lactide) (PLLA) fiber membrane. Characterization of the obtained nanofibrous meshes indicates that PCL‐PMH and PLLA can be well blended to make smooth fibers, and fibrous diameter vary little with blending PCL‐PMH. The aggregation state of two macromolecules is closely correlated with blend ratio, molecular structure, and molecular weight of PCL‐PMH, and only when PCL‐PMH and PLLA form good interfacial adhesion can PMH give full play to its potential for toughening the fiber membrane. The tensile strength and elongation at break of the blend are 6.20 MPa and 63.40% under the optimal conditions, respectively, and it also exhibits the representative feature of toughness materials. The blending fiber membrane is as no cytotoxic as original PLLA. This work will provide a new way for toughness of electrospun fiber membrane in practice.     

Synthesis and properties of biodegradable elastomeric epoxy modified polyurethanes based on poly(ε-caprolactone) and poly(ethylene glycol)

Biodegradable polyurethane elastomers with potential for applications in medical implants with tunable degradation rate and physical properties were synthesized from reaction of epoxy terminated polyurethanes (EUP) with 1,6-hexamethylene diamine (HMDA) as curing agent. Poly(ε-caprolactone) (PCL) and poly(ethylene glycol) (PEG) as well as 1,6-hexamethylene diisocyanate (HDI) were used for preparation of isocyanate terminated polyurethanes which were subsequently blocked with glycidol to prepare EUPs. All materials were characterized by conventional methods, and their properties were studied fully. Results showed that elastomers based on PEG exhibit superior degradation rate and inferior mechanical properties in comparison to elastomers based on PCL. Optimum degradation rate and mechanical properties were obtained from elastomers made from mixture of PCL and PEG base EUPs.     

Biodegradable photocrosslinkable poly(depsipeptide‐co‐ε‐caprolactone) for tissue engineering: Synthesis,characterization, and In vitro evaluation

Stereolithography has become increasingly popular in scaffold fabrication due to automation and well‐controlled geometry complexity, and consequently, there is a great need for new suitable biodegradable photocrosslinkable polymers. In this study, a new type of photocrosslinkable poly(ester amide) was synthesized based on ε‐caprolactone and l ‐alanine‐derived depsipeptide and was applied to fabrication of three‐dimensional (3D) scaffolds by stereolithography. ¹H nuclear magnetic resonance and Fourier transform infra‐red analysis confirmed the formation of new bonds during the polymer synthesis. Incorporation of depsipeptide increased the glass transition temperature and hydrophilicity of the polymer and accelerated hydrolytic degradation compared with the poly(ε‐caprolactone) homopolymer. The compressive strength of the 3D scaffolds increased with the increasing depsipeptide content. This work demonstrated that incorporation of depsipeptide into photocrosslinkable polyesters resulted in excellent cytocompatibility and tunable degradation rates and mechanical properties and thus expanded the repertoire of biomaterials suitable for 3D photofabrication of high‐resolution tissue engineering scaffolds. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 3307–3315     

Development of Non‐Cell Adhesive Vascular Grafts Using Supramolecular Building Blocks

Cell‐free approaches to in situ tissue engineering require materials that are mechanically stable and are able to control cell‐adhesive behavior upon implantation. Here, the development of mechanically stable grafts with non‐cell adhesive properties via a mix‐and‐match approach using ureido‐pyrimidinone (UPy)‐modified supramolecular polymers is reported. Cell adhesion is prevented in vitro through mixing of end‐functionalized or chain‐extended UPy‐polycaprolactone (UPy‐PCL or CE‐UPy‐PCL, respectively) with end‐functionalized UPy‐poly(ethylene glycol) (UPy‐PEG) at a ratio of 90:10. Further characterization reveals intimate mixing behavior of UPy‐PCL with UPy‐PEG, but poor mechanical properties, whereas CE‐UPy‐PCL scaffolds are mechanically stable. As a proof‐of‐concept for the use of non‐cell adhesive supramolecular materials in vivo, electrospun vascular scaffolds are applied in an aortic interposition rat model, showing reduced cell infiltration in the presence of only 10% of UPy‐PEG. Together, these results provide the first steps toward advanced supramolecular biomaterials for in situ vascular tissue engineering with control over selective cell capturing.

     

Electroactive 3D Scaffolds Based on Silk Fibroin and Water‐Borne Polyaniline for Skeletal Muscle Tissue Engineering

Silk fibroin (SF) with good biocompatibility and degradability has great potential for tissue engineering. However, the SF based scaffolds lack the electroactivity to regulate the myogenic differentiation for the regeneration of muscle tissue, which is sensitive to electrical signal. Herein, a series of electroactive biodegradable scaffolds based on SF and water‐soluble conductive poly(aniline‐co‐N‐(4‐sulfophenyl) aniline) (PASA) via a green method for skeletal muscle tissue engineering are designed. SF/PASA scaffolds are prepared by vortex of aqueous solution of SF and PASA under physiological condition. Murine‐derived L929 fibroblast and C2C12 myoblast cells are used to evaluate cytotoxicity of SF/PASA scaffolds. Moreover, myogenic differentiation of C2C12 cells is investigated by analyzing the morphology of myotubes and related gene expression. These results suggest that electroactive SF/PASA scaffolds with a suitable microenvironment, which can enhance the myogenic differentiation of C2C12 cells, have a great potential for skeletal muscle regeneration.     

Modular,synthetic, thiol-ene mediated hydrogel networks as potential scaffolds for 3D cell cultures and tissue regeneration

Natural polymers such as collagen are popular materials for tissue engineering scaffolds due to their innate bioactivity and biocompatibility. Being derived from animal sources, however, means that batch-to-batch consistency is often low and the extraction of collagen is costly. This conundrum facilitates the need for synthetic alternatives as scaffolding materials. In this study, a system of poly(ethylene glycol) (PEG)-based thiol-ene coupled (TEC) hydrogel scaffolds is presented for tissue engineering purposes. The platform includes several necessary features, namely cytocompatibility, high swelling ability, biodegradability, tunable stiffness, and fast, straightforward fabrication. The swelling ability is provided by the hydrophilicity of the ether-links of PEG, which facilitated the formation of high water content hydrogels that match the water content of soft tissues for the proper diffusion of nutrients and waste compounds. TEC ensures fast and facile fabrication, with cross-linking moieties that allow for the biodegradation of the hydrogel network through hydrolytic cleavage. The mechanical properties of the scaffolds are made tunable in the range of storage moduli spanning <1 kPa to >100 kPa. It is also shown that despite the synthetic nature of the hydrogels, human dermal fibroblasts and murine macrophages, Raw 264.7, were able to survive and produce extracellular protein excretions while embedded in the 3D hydrogels.     

Fabrication and Properties of Polycaprolactone Composites Containing Calcium Phosphate-Based Ceramics and Bioactive Glasses in Bone Tissue Engineering: A Review

Polycaprolactone (PCL) is a bioresorbable and biocompatible polymer that has been widely used in long-term implants and controlled drug release applications. However, when it comes to tissue engineering, PCL suffers from some shortcomings such as slow degradation rate, poor mechanical properties, and low cell adhesion. The incorporation of calcium phosphate-based ceramics and bioactive glasses into PCL has yielded a class of hybrid biomaterials with remarkably improved mechanical properties, controllable degradation rates, and enhanced bioactivity that are suitable for bone tissue engineering. This review presents a comprehensive study on recent advances in the fabrication and properties of PCL-based composite scaffolds containing calcium phosphate-based ceramics and bioglasses in terms of porosity, degradation rate, mechanical properties, in vitro and in vivo biocompatibility and bioactivity for bone regeneration applications. The fabrication routes range from traditional methods such as solvent casting and particulate leaching to novel approaches including solid free-form techniques.     

Conductive stretchable shape memory elastomers combining with electrical stimulation for synergistic osteogenic differentiation

The natural extracellular matrix (ECM) possessed varying biomechanical properties which played important roles in the dynamic cellular microenvironment. However, for the conventional bone tissue engineering scaffolds, stretchability and shape memory property were normally absent. Thus, the behaviors of responsive changes required in dynamic physiological settings were unsatisfactory. Herein, a series of conductive polyurethane shape memory elastomers (PCL-IPDI-AT) were synthesized, which based on conductive amino capped aniline trimer (AT), isophorone diisocyanate (IPDI) and poly(ԑ-caprolactone) (PCL). The conductive elastomers possessed high elasticity and flexibility, especially, the breaking elongation of copolymer with 15% AT content was up to 570 ± 56%. The mechanical properties of elastomers could be adjusted by regulating the content of AT in copolymers. The conductive elastomers exhibited excellent shape fixity ratio and good shape recovery ability at 37 °C. The electrical conductivity of elastomers was measured via the standard van der Pauw four-probe method. They were all around 10⁻⁷ S/cm and similar to that in human physiological environments. On the one hand, excellent cytocompatibility was demonstrated by the viability and proliferation results of MC3T3-E1 pre-osteoblasts seeded on the elastomer. On the other hand, the elastomer could synergistically promote the osteogenic differentiation compared to PCL in terms of ALP activity, calcium deposition, and bone-related protein and gene expression levels as combined with electrical stimulation (ES). Specifically, the ALP activity for conductive elastomer under ES was notably improved by 1.4-fold compared to PCL at 7 days. Overall, the conductive elastomers displayed excellent stretchability, shape memory property, fatigue resistance and osteogenic bioactivity. They may be applied as bone substitutes for electrical-signal-sensitive bone tissue engineering.     

Novel 3D printed shape-memory PLLA-TMC/GA-TMC scaffolds for bone tissue engineering with the improved mechanical properties and degradability

The biodegradable substitution materials for bone tissue engineering have been a research hotspot. As is known to all, the biodegradability, biocompatibility, mechanical properties and plasticity of the substitution materials are the important indicators for the application of implantation materials. In this article, we reported a novel binary substitution material by blending the poly(lactic-acid)-co-(trimethylene-carbonate) and poly(glycolic-acid)-co-(trimethylene-carbonate), which are both biodegradable polymers with the same segment of flexible trimethylene-carbonate in order to accelerate the degradation rate of poly(lactic-acid)-co-(trimethylene carbonate) substrate and improve its mechanical properties. Besides, we further fabricate the porous poly(lactic-acid)-co-(trimethylene-carbonate)/poly(glycolic-acid)-co-(trimethylene-carbonate) scaffolds with uniform microstructure by the 3D extrusion printing technology in a mild printing condition. The physicochemical properties of the poly(lactic-acid)-co-(trimethylene-carbonate)/poly(glycolic-acid)-co-(trimethylene-carbonate) and the 3D printing scaffolds were investigated by universal tensile dynamometer, fourier transform infrared reflection (FTIR), scanning electron microscope (SEM) and differential scanning calorimeter (DSC). Meanwhile, the degradability of the PLLA-TMC/GA-TMC was performed in vitro degradation assays. Compared with PLLA-TMC group, PLLA-TMC/GA-TMC groups maintained the decreasing T_g, higher degradation rate and initial mechanical performance. Furthermore, the PLLA-TMC/GA-TMC 3D printing scaffolds provided shape-memory ability at 37 ℃. In summary, the PLLA-TMC/GA-TMC can be regarded as an alternative substitution material for bone tissue engineering.     

Electrospun Poly(ε‐caprolactone)/Polyhedral Oligomeric Silsesquioxane‐Based Copolymer Blends: Evolution of Fiber Internal Structures

This study reports the structural transition of electrospun poly(ε‐caprolactone) (PCL)/poly[(propylmethacryl‐heptaisobutyl‐polyhedral oligomeric silsesquioxane)‐co‐(methyl meth­acrylate)] (POSS‐MMA) blends, from PCL‐rich fibers, to bicontinuous PCL core/POSS‐MMA shell fibers, to POSS‐MMA‐rich fibers with a discontinuous PCL inner phase. A ternary phase diagram depicting the electrospinnability of PCL/POSS‐MMA solutions is constructed by evaluating the morphological features of fibers electrospun from solutions with various concentrations and PCL/POSS‐MMA blend ratios. X‐ray diffraction, Raman spectroscopy, and differential scanning calorimetry are further used to characterize the electrospun PCL/POSS‐MMA hybrid fibers. These physicochemical characterization results are thoroughly discussed to understand the internal structures of the hybrid fibers, which are directly correlated to the phase separation behavior of the electrospun solutions. The current study provides further insight into the complex phase behavior of POSS‐copolymer‐based systems, which hold great potential for a broad spectrum of biomedical applications.

     

Synthesis and characterization of functionalized poly(ɛ‐caprolactone)

Polyesters constitute an important class of materials for in vivo biomedical applications. Poly(?‐caprolactone) (PCL) is a hydrophobic biodegradable polyester which is employed to a lesser extent in drug delivery applications due to its rather limited range of physicochemical characteristics. Here, we present a new paradigm for the synthesis of functionalized PCL via copolymerization of caprolactone with α,ω‐epoxy esters. Ethyl 2‐methyl‐4‐pentenoate oxide was used as a monomer which was copolymerized with ?‐caprolactone to yield random copolymers of poly(?‐caprolactone‐co‐ethyl‐2‐methyl‐4‐pentenoate oxide). The reaction conditions were optimized to generate functionalization greater than 25%. The use of ester‐epoxides favors a statistical and uniform distribution of monomer along the polymer backbone, which while preserving some of the key properties of PCL such as glass transition that is below room temperature, allows the tailoring of the melting behavior of PCL. The strategy presented herein opens up new avenues for engineering PCL properties for biomedical applications. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013 , 51, 3375–3382     

Thermoplastic elastomers based on poly(l‐Lysine)‐Poly(ε‐Caprolactone) multi‐block copolymers

Novel thermoplastic elastomers based on multi‐block copolymers of poly(l ‐lysine) (PLL), poly(N‐ε‐carbobenzyloxyl‐l ‐lysine) (PZLL), poly(ε‐caprolactone) (PCL), and poly(ethylene glycol) (PEG) were synthesized by combination of ring‐opening polymerization (ROP) and chain extension via l ‐lysine diisocyanate (LDI). SEC and ¹H NMR were used to characterize the multi‐block copolymers, with number‐average molecular weights between 38,900 and 73,400 g/mol. Multi‐block copolymers were proved to be good thermoplastic elastomers with Young's modulus between 5 and 60 MPa and tensile strain up to 1300%. The PLL‐containing multi‐block copolymers were electrospun into non‐woven mats that exhibited high surface hydrophilicity and wettability. The polypeptide–polyester materials were biocompatible, bio‐based and environment‐friendly for promising wide applications. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 3012–3018     

Synthesis and properties of Polycaprolactone‐graft‐poly(2‐(dimethylamino)ethyl methacrylate‐co‐methoxy polyethylene glycol monomethacrylate) as non‐viral gene vector

Polycaprolactone‐graft‐Poly(2‐(dimethylamino)ethyl methacrylate‐co‐methoxy polyethylene glycol monomethacrylate) (PCL‐graft‐P(DMAEMA‐co‐mPEGMMA)) was synthesized by combination of ring‐opening polymerization (ROP) and atom transfer radical polymerization (ATRP). PCL‐graft‐P(DMAEMA‐co‐mPEGMMA) was characterized by FTIR, ¹H NMR, and GPC. PCL‐graft‐P(DMAEMA‐co‐mPEGMMA) with expected composition and structure was achieved. pH‐ and thermo‐sensitive properties of the PCL‐graft‐P(DMAEMA‐co‐mPEGMMA) nanoparticles prepared by the nanoprecipitation method were investigated by TEM and DLS. With increase in the temperature, the size of PCL‐graft‐P(DMAEMA‐co‐mPEGMMA) nanoparticles is decreased under base environment. Furthermore, in vitro transfection and toxicity assays were tested in 293T cells. The results indicate that PCL‐graft‐P(DMAEMA‐co‐PEGMMA) has lower cytotoxicity at N/P ratios less than 10 with transfection efficiency concomitantly reducing at N/P ratios less than 20 compared to PCL‐graft‐PDMAEMA as the control. However, PCL‐graft‐P(DMAEMA‐co‐PEGMMA) presents higher transfection efficiency at N/P ratios more than 20 compared to PCL‐graft‐PDMAEMA. Copyright © 2010 John Wiley & Sons, Ltd.     

Synthesis and characterization of novel h‐HTBN/PEG PU copolymers: effect of surface properties on hemocompatibility

This work reported the hydrophilicity, hemocompatibility, and cytotoxicity of novel polyurethane (PU) scaffolds for tissue engineering, especially the hydrolysis effect of a soft‐segmented component, a hydrolytically‐modified hydroxyl‐terminated poly(butadiene‐co‐acrylonitrile) (h‐HTBN), on these properties. The PU copolymers were prepared by coupling poly(ethylene glycol) (PEG) with the h‐HTBN together with the help of 1,1‐methylene bis‐(4‐isocyanatocyclohexane) as a bridging reagent. The structure of PU copolymers was characterized by Fourier transformation infrared spectrometry (FTIR). The experimental results indicated that the hydrolytically‐modified HTBN increases water absorption and decreases water contact angles, improving surface hydrophilicity. The synthesized h‐HTBN/PEG PU copolymers display low hemolysis activity, and a little amount of platelet adhesion and activation, implying good compatibility. The methyl tretrazolium (MTT) assays elicited that the cytotoxicity is related to the component ratios of h‐HTBN to PEG and the hydrolysis modification of HTBN. The PU scaffolds can be employed as potential candidates for blood contacting applications. Copyright © 2009 John Wiley & Sons, Ltd.     

Poly(l‐glutamic acid)‐based micellar hydrogel with improved mechanical performance and proteins loading

Soft tissues, such as fat and skin, present high flexibility and are capable of withstanding large deformation in various functions. Hydrogels that can resemble the mechanical performance of soft tissue are unique and widely demanded. In this study, micellar hydrogels based on biocompatible poly(l ‐glutamic acid) (PLGA) were designed with the enhanced capacity to bear large deformation. Amphipathic triblock copolymer poly(ethylene glycol) acrylate‐co‐poly(ε‐caprolactone)‐co‐poly (ethylene glycol) acrylate (APEG‐PCL‐APEG) with two terminal double bonds was synthesized and self‐assembled into micelles. At the same time, graft copolymers, poly(l ‐glutamic acid)‐g‐hydroxyethyl methacrylate (PLGA‐g‐HEMA) with double bonds were synthesized. APEG‐PCL‐APEG micelles and PLGA‐g‐HEMA were mixed to construct micellar hydrogel via radical polymerization. The crystalline structure and hydrophobic aggregation of copolymers (APEG‐PCL‐APEG) were found to associate with PCL molecular weight. Due to the hydrophobic stress dissipation and crystalline structure of the micelles, the softness and toughness of hydrogels were promoted, exhibiting a 25% increase in ultimate strain. Moreover, the micellar hydrogels were able to load proteins with long‐term retention. In addition, under dynamic mechanical stimulation, the release of proteins could be accelerated. Besides, the micellar hydrogels also supported rabbit adipose‐derived stem cells (rASCs) growth, thus exhibiting the potential toward soft tissue engineering. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2019 , 57, 1115–1125     

The electrospun poly(ε‐caprolactone)/fluoridated hydroxyapatite nanocomposite for bone tissue engineering

Biodegradable cell‐incorporated scaffolds can guide the regeneration process of bone defects such as physiological resorption, tooth loss, and trauma which medically, socially, and economically hurt patients. Here, 0, 5, 10, and 15 wt% fluoridated hydroxyapatite (FHA) nanoparticles containing 25 wt% F^? and 75 wt% OH^? were incorporated into poly(ε‐caprolactone) (PCL) matrix to produce PCL/FHA nanocomposite scaffolds using electrospinning method. Then, scanning electron microscopy (SEM), X‐ray diffraction (XRD) pattern, and Fourier transform infrared spectroscopy (FTIR) were used to evaluate the morphology, phase structure, and functional groups of prepared electrospun scaffolds, respectively. Furthermore, the tensile strength and elastic modulus of electrospun scaffolds were investigated using the tensile test. Moreover, the biodegradation behavior of electrospun PCL/FHA scaffolds was studied by the evaluation of weight loss of mats and the alternation of pH in phosphate buffer saline (PBS) up to 30 days of incubation. Then, the biocompatibility of prepared mats was investigated by culturing MG‐63 osteoblast cell line and performing MTT assay. In addition, the adhesion of osteoblast cells on prepared electrospun scaffolds was studied using their SEM images. Results revealed that the fiber diameter of prepared electrospun PCL/FHA scaffolds alters between 700 and 900 nm. The mechanical assay illustrated the mat with 10 wt% FHA nanoparticles revealed the highest tensile strength and elastic modulus. The weight loss alternation of mats determined around 1% to 8% after 30 days of incubation. The biocompatibility and cell adhesion of mats improved by increasing the amounts of FHA nanoparticles.     

Phase behavior,crystallization, and morphology in thermosetting blends of a biodegradable poly(ethylene glycol)‐type epoxy resin and poly(ϵ‐caprolactone)

Thermosetting blends of a biodegradable poly(ethylene glycol)‐type epoxy resin (PEG‐ER) and poly(?‐caprolactone) (PCL) were prepared via an in situ curing reaction of poly(ethylene glycol) diglycidyl ether (PEGDGE) and maleic anhydride (MAH) in the presence of PCL. The miscibility, phase behavior, crystallization, and morphology of these blends were investigated. The uncured PCL/PEGDGE blends were miscible, mainly because of the entropic contribution, as the molecular weight of PEGDGE was very low. The crystallization and melting behavior of both PCL and the poly(ethylene glycol) (PEG) segment of PEGDGE were less affected in the uncured PCL/PEGDGE blends because of the very close glass‐transition temperatures of PCL and PEGDGE. However, the cured PCL/PEG‐ER blends were immiscible and exhibited two separate glass transitions, as revealed by differential scanning calorimetry and dynamic mechanical analysis. There existed two phases in the cured PCL/PEG‐ER blends, that is, a PCL‐rich phase and a PEG‐ER crosslinked phase composed of an MAH‐cured PEGDGE network. The crystallization of PCL was slightly enhanced in the cured blends because of the phase‐separated nature; meanwhile, the PEG segment was highly restricted in the crosslinked network and was noncrystallizable in the cured blends. The phase structure and morphology of the cured PCL/PEG‐ER blends were examined with scanning electron microscopy; a variety of phase morphologies were observed that depended on the blend composition. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 2833–2843, 2004     

Development of Electrospun Three‐arm Star Poly(ε‐caprolactone) Meshes for Tissue Engineering Applications

We have developed three‐dimensional electrospun microfibrous meshes of a novel star branched three‐arm poly(ε‐caprolactone) (*PCL) as potential scaffolds for tissue engineering applications. The processing conditions required to obtain uniform fibers were optimized by studying their influence on fiber morphology and size. Polymer molecular weight and solution feed rate influenced both the mesh microstructure and the tensile properties of the developed mats. Electrospun samples were also tested for their mechanical properties in wet conditions, showing higher yield strength and strain in comparison to that observed in dry conditions. Cell culture experiments employing MC3T3‐E1 osteoblast like cells showed good cell viability adhesion and collagen production on the *PCL scaffolds.