Handling characteristics of poly(L-lactide-co-epsilon-caprolactone) monofilament suture

A monofilament suture made of poly(L-lactide-co-epsilon-caprolactone) was examined by several mechanical tests to evaluate handling characteristics for tight tying. Six types of other monofilament sutures were also examined for comparisons. Two of these were nonabsorbable, while the others were absorbable sutures. Sutures consisting of glicolide were strongest among all the sutures examined. On the other hand, PROLENE and P(LA/CL) sutures showed high knot-pull strength despite low straight pull strength. Untying performance was evaluated by viscoelasticity, bending plasticity and tying test. A good correlation between tan delta and bending plasticity index was observed and the poly(L-lactide-co-epsilon-caprolactone) suture exhibited high tan delta, high bending plasticity and good resistance against untying.     

Electrospun gelatin/poly(L-lactide-co-epsilon-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-epsilon-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 vivo biocompatibilty and degradation behavior of elastic poly(L-lactide-co-epsilon-caprolactone) scaffolds

Tubular scaffolds were fabricated from very elastic poly(L-lactide-co-epsilon-caprolactone) (PLCL, 50:50). The scaffolds were seeded with smooth muscle cells (SMCs) and implanted in nude mice to investigate the tissue compatibility and in vivo degradation behavior. Histological examination of all the implants with haematoxylin and eosin staining, masson trichrome staining, SM alpha-actin antibody, and CM-DiI labeling confirmed that the regular morphology and biofunction of the SMCs seeded and the expression of the vascular smooth muscle matrices in PLCL scaffolds. The implanted PLCL scaffolds displayed a slow degradation on time, where caprolactone units were faster degraded than lactide did. This could be explained by the fact that amorphous regions composed of mainly CL moieties degraded earlier than hard domains where most of the LA units were located. From these results, the scaffolds applied in this study were found to exhibit excellent tissue compatibility to SMCs and might be very useful for vascular tissue engineering.     

Cartilage regeneration with highly-elastic three-dimensional scaffolds prepared from biodegradable poly(L-lactide-co-epsilon-caprolactone)

Compressive mechanical stimuli are crucial in regenerating cartilage with tissue engineering, which creates a need for scaffolds that can maintain their mechanical integrity while delivering mechanical signals to adherent cells during strain applications. With these goals in mind, the aim of this study was to develop a mechano-active scaffold that facilitated effective cartilaginous tissue formation under dynamic physiological environments. Using a gel-pressing method, we fabricated a biodegradable and highly-elastic scaffold from poly(L-lactide-co-epsilon-caprolactone) (PLCL; 5:5), with 85% porosity and a 300-500-microm pore size, and we compared it to control scaffolds made of rigid polylactide (PLA) or poly(lactide-co-glycolide) (PLGA). After tensile mechanical tests and recovery tests confirmed the elasticity of the PLCL scaffolds, we seeded them with rabbit chondrocytes, cultured them in vitro, and subcutaneously implanted them into nude mice for up to eight weeks. The PLCL scaffolds possessed a completely rubber-like elasticity, were easily twisted and bent, and exhibited an almost complete (over 97%) recovery from applied strain (up to 500%); the control PLA scaffolds showed little recovery. In vitro and in vivo accumulations of extracellular matrix on the cell-PLCL constructs demonstrated that they could not only sustain but also significantly enhance chondrogenic differentiation. Moreover, the mechanical stimulation of the dynamic in vivo environment promoted deposition of the chondral extracellular matrix onto the PLCL. In contrast, on the PLA scaffolds, most of the chondrocytes had de-differentiated and formed fibrous tissues. In a rabbit defect model, the groups treated with PLCL scaffolds exhibited significantly enhanced cartilage regeneration compared to groups harboring an empty control or PLGA scaffolds. These results indicated that the mechano-active PLCL scaffolds effectively delivered mechanical signals associated with biological environments to adherent chondrocytes, suggesting that these elastic PLCL scaffolds could successfully be used for cartilage regeneration.     

Characterization, degradation, and mechanical strength of poly(D,L-lactide-co-epsilon-caprolactone)-poly(ethylene glycol)-poly(D,L-lactide-co-epsilon-caprolactone)

A series of three biocompatible P(CL-co-LA)-PEG-P(CL-co-LA) copolymers were synthesized using ring-opening polymerization and characterized by 1H-NMR, gel permeation chromatography, DSC, dynamic-mechanical analysis, and X-ray diffraction. The number of monomer units was kept constant, while the D,L-LA fraction was varied so as to constitute 0, 30, or 70% of the end segments. The molecular weights were sufficiently high to eventually permit 3D scaffold preparation. A degradation study was carried out over 26 weeks, and the effect of monomer composition on the rate of degradation as well as on changes in mechanical strength was investigated. Pure polycaprolactone (PCL)-poly(ethylene glycol) (PEG)-PCL copolymer, P(100/0), was a crystalline material displaying no measurable mass loss, a 30% reduction in mean molecular weight (Mn), and only very slight changes in tensile strength. The random incorporation of 30 and 70% D,L-LA into the end sections of the polymer chain, produced more and more amorphous materials, exhibiting increasingly high rates of degradation, mass loss, and loss of tensile strength. Compared with random P(CL-co-LA), the presence of the PEG block was found both to improve hydrophilicity and thus the rate of degradation and to infer a stabilizing quality, thereby pacing the decrease in tensile strength during degradation. The tested copolymers range from materials exhibiting low mechanical strength and high rate of degradation to slow-degrading materials with high mechanical strength suitable, e.g., for three-dimensional scaffolding.     

Surface modified poly(L-lactide-co-epsilon-caprolactone) microspheres as scaffold for tissue engineering

P-15 modified poly(L-lactide-co-epsilon-caprolactone) (PLCL) microspheres were investigated as scaffolds for tissue engineering applications. PLCL copolymer was synthesized by ring opening polymerization and was composed of a soft matrix of mainly epsilon-caprolactone moieties and hard domains containing more of L-lactide units thus exhibiting a rubber like elasticity responsible for providing mechanical strength to scaffolds. Microspheres were fabricated by solvent evaporation method and surface modified with P-15, a synthetic analogue of collagen. These were then evaluated for cell adhesion, ECM formation and cell proliferation. Anchorage dependent cell lines LLCPK-1 and L6 were seeded on PLCL microspheres (unmodified surface activated microspheres) and P-15-PLCL microspheres (P-15 modified microspheres). P-15 modified microspheres showed significantly higher cell adhesion and viability than unmodified microspheres. Scanning electron microscopy also revealed copious amount of extra-cellular matrix production by P-15. Initial results of cell culture experiment on two different cell lines suggested that the growth of LLCPK-1 in a 3D environment with P-15 modified microspheres is via spreading and flattening on the surface of scaffold followed by formation of a sheet-like structure while L6 grew in the form of multilayered structures with formation of interparticulate cellular bridges. The 3D moldable nature, combined with modification of surface chemistry with cell adhesion molecules such as P-15 to enhance proliferation of epithelial cells and myoblasts, recommends further investigation of P-15-PLCL microspheres for production of an ideal scaffold for soft tissue engineering.     

Mechanical responses of a compliant electrospun poly(L-lactide-co-epsilon-caprolactone) small-diameter vascular graft

To design a "mechano-active" small-diameter artificial vascular graft, a tubular scaffold made of elastomeric poly(L-lactide-co-epsilon-caprolactone) fabrics at different wall thicknesses was fabricated using an electrospinning (ELSP) technique. The wall thickness of the fabricated tube (inner diameter; approximately 2.3-2.5 mm and wall thickness; 50-340 microm) increased proportionally with ELSP time. The wall thickness dependence of mechanical responses including intraluminal pressure-induced inflation was determined under static and dynamic flow conditions. From the compliance-related parameters (stiffness parameter and diameter compliance) measured under static condition, the smaller the wall thickness, the more compliant the tube. Under dynamic flow condition (1 Hz, maximal/minimal pressure of 90 mmHg/45 mmHg) produced by a custom-designed arterial circulatory system, strain, defined as the relative increase in diameter per pulse, increased with the decrease in wall thickness, which approached that of a native artery. Thus, a mechano-active scaffold that pulsates synchronously by responding to pulsatile flow was prepared using elastomeric PLCL as a base material and an ELSP technique.     

The effect of gelatin incorporation into electrospun poly(L-lactide-co-epsilon-caprolactone) fibers on mechanical properties and cytocompatibility

Very elastic poly(L-lactide-co-epsilon-caprolactone) (PLCL) (50:50) copolymer blended with gelatin was electrospun into microfibers from a hexafluoroisopropanol solution. PLCL fiber sheet exhibited the unique soft and flexible behavior while gelatin fiber was hard and brittle. As the gelatin content of PLCL/gelatin fibers increased, Young's modulus was increased, but the elongation was decreased compared to those of PLCL. However, fibers containing 10-30 wt% gelatin demonstrated an enhanced tensile strength with still high elongation to be beneficial for tissue engineering scaffolds. The cytocompatibility of electrospun fiber sheets was evaluated by fibroblasts (NIH-3T3) cell culture. The initial cell adhesion on various fibers after 5h was somewhat similar, but in the order of PLCL>PLCL70/gelatin30 approximately PLCL50/gelatin50>PLCL90/gelatin10 approximately gelatin>PLCL30/gelatin70. However, the cell proliferation exhibited a completely different and strong dependence on the fiber composition: a very high proliferation rate on PLCL90/gelatin10, followed by PLCL>gelatin>PLCL70/gelatin30. Such an enhanced effect of gelatin, especially at 10 wt% content, on strength and cytocompatibility of PLCL/gelatin fibers would be very preferable for tissue engineering scaffolds.     

Application of an elastic biodegradable poly(L-lactide-co-epsilon-caprolactone) scaffold for cartilage tissue regeneration

In cartilage tissue regeneration, it is important that an implant inserted into a defect site can maintain its mechanical integrity and endure stress loads from the body, in addition to being biocompatible and able to induce tissue growth. These factors are crucial in the design of scaffolds for cartilage tissue engineering. We developed an elastic biodegradable scaffold from poly(L-lactideco-epsilon-caprolactone) (PLCL) for application in cartilage treatment. Biodegradable PLCL co-polymer was synthesized from L-lactide and epsilon-caprolactone in the presence of stannous octoate as a catalyst. A highly elastic PLCL scaffold was fabricated by a gel-pressing method with 80% porosity and 300-500 microm pore size. The tensile mechanical and recovery tests were performed in order to examine mechanical and elastic properties of the PLCL scaffold. They could be easily twisted and bent and exhibited almost complete (over 94%) recoverable extension up to breaking point. For examining cartilaginous tissue formation, rabbit chondrocytes were seeded on scaffolds. They were then cultured in vitro for 5 weeks or implanted in nude mice subcutaneously. From in vitro and in vivo tests, the accumulation of extracellular matrix on the constructs showed that chondrogenic differentiation was sustained onto PLCL scaffolds. Histological analysis showed that cells onto PLCL scaffolds formed mature and well-developed cartilaginous tissue, as evidenced by chondrocytes within lacunae. From these results, we are confident that elastic PLCL scaffolds exhibit biocompatibility and as such would provide an environment where cartilage tissue growth is enhanced and facilitated.     

Surface characteristics and biocompatibility of lactide-based poly(ethylene glycol) scaffolds for tissue engineering

Novel lactide-based poly(ethylene glycol) (PEG) polymer networks (GL9-PEGs) were prepared by UV copolymerization of a glycerol-lactide triacrylate (GL9-Ac) with PEG monoacrylate (PEG-Ac) to use as scaffolds in tissue engineering, and the surface properties and biocompatibility of these networks were investigated as a function of PEG molecular weight and content. Analysis by ATR-FTIR and ESCA reveled that PEG was incorporated well within the GL9-PEG polymer networks and was enriched at the surfaces. From the results of SEM, AFM, and contact angle analyses, GL9-PEG networks showed relatively rough and irregular surfaces compared to GL9 network, but the mobile PEG chains coupled at their termini were readily exposed toward the aqueous environment when contacting water such that the surfaces became smoother and more hydrophilic. This reorientation and increase in hydrophilicity were more extensive with increasing PEG molecular weight and content. As compared to GL9 network lacking PEG, protein adsorption as well as platelet and S. epidermidis adhesion to GL9-PEG networks were significantly reduced as the molecular weight and content of PEG was increased, indicating that GL9-PEG networks are more biocompatible than the GL9 network due to PEG's passivity. Based on the physical and biological characterization reported, the GL9-PEG materials would appear to be interesting candidates as matrices for tissue engineering.     

Role of poly(lactide-co-glycolide) particle size on gas-foamed scaffolds

Macroporous polymeric scaffolds are frequently used in tissue engineering to allow for cell seeding and host cell invasion of the scaffold following implantation. The process of gas foaming/particulate leaching (GF/PL) is one method to form porous three dimensional scaffolds from particulate poly(lactide-co-glycolide) (PLG). The current study was designed to test the hypothesis that the size of the polymer particles used in this process will control the properties of the scaffolds. Scaffolds were prepared from PLG particles of various sizes (less than 75 microm, 75-106 microm, 106-250 microm and 250-425 microm) and subsequently analyzed. Scaffolds formed from large particles (250-425 microm) displayed significantly decreased compressive moduli, as compared to scaffolds fabricated from smaller particles. In addition, these scaffolds have a pore structure that is less interconnected and contains closed pores. Analysis of tissue in-growth, utilizing a novel computer-aided method, demonstrated that scaffolds formed from smaller particle sizes (less than 106 microm) have significantly more tissue penetration than those formed from larger particle sizes (greater than 106 microm). These results indicate that using small PLG particles (less than 106 microm) leads to high elastic moduli, provides a more interconnected pore structure and promotes greater tissue penetration into the scaffolds in vivo.     

Role of poly(lactide-co-glycolide) particle size on gas-foamed scaffolds

Macroporous polymeric scaffolds are frequently used in tissue engineering to allow for cell seeding and host cell invasion of the scaffold following implantation. The process of gas foaming/particulate leaching (GF/PL) is one method to form porous three dimensional scaffolds from particulate poly(lactide-co-glycolide) (PLG). The current study was designed to test the hypothesis that the size of the polymer particles used in this process will control the properties of the scaffolds. Scaffolds were prepared from PLG particles of various sizes (less than 75μ m, 75–106 μm, 106–250 μm and 250–425 μm) and subsequently analyzed. Scaffolds formed from large particles (250–425 μm) displayed significantly decreased compressive moduli, as compared to scaffolds fabricated from smaller particles. In addition, these scaffolds have a pore structure that is less interconnected and contains closed pores. Analysis of tissue in-growth, utilizing a novel computer-aided method, demonstrated that scaffolds formed from smaller particle sizes (less than 106 μm) have significantly more tissue penetration than those formed from larger particle sizes (greater than 106 μm). These results indicate that using small PLG particles (less than 106 μm) leads to high elastic moduli, provides a more interconnected pore structure and promotes greater tissue penetration into the scaffolds in vivo.     

Improved mesenchymal stem cells attachment and in vitro cartilage tissue formation on chitosan-modified poly(L-lactide-co-epsilon-caprolactone) scaffold

Considering the load-bearing physiological requirement of articular cartilage, scaffold for cartilage tissue engineering should exhibit appropriate mechanical responses as natural cartilage undergoing temporary deformation on loading with little structural collapse, and recovering to the original geometry on unloading. A porous elastomeric poly l-lactide-co-?-caprolactone (PLCL) was generated and crosslinked at the surface to chitosan to improve its wettability. Human bone marrow derived mesenchymal stem cells (MSC) attachment, morphological change, proliferation and in vitro cartilage tissue formation on the chitosan-modified PLCL scaffold were compared with the unmodified PLCL scaffold. Chitosan surface promoted more consistent and even distribution of the seeded MSC within the scaffold. MSC rapidly adopted a distinct spread-up morphology on attachment on the chitosan-modified PLCL scaffold with the formation of F-actin stress fiber which proceeded to cell aggregation; an event much delayed in the unmodified PLCL. Enhanced cartilage formation on the chitosan-modified PLCL was shown by real-time PCR analysis, histological and immunochemistry staining and biochemical assays of the cartilage extracellular matrix components. The Young's modulus of the derived cartilage tissues on the chitosan-modified PLCL scaffold was significantly increased and doubled that of the unmodified PLCL. Our results show that chitosan modification of the PLCL scaffold improved the cell compatibility of the PLCL scaffold without significant alteration of the physical elastomeric properties of PLCL and resulted in the formation of cartilage tissue of better quality.     

Fabrication and characterization of poly (ethylenimine) modified poly (l-lactic acid) nanofibrous scaffolds

Abstract

Bone tissue engineering aims to construct biological substitutes for repairing bone defects. Nanofibrous (NF) scaffolds are commonly utilized to mimic the extracellular matrix (ECM) environment and promote tissue regeneration in tissue engineering process. Poly (lactic acid) (PLA) has attracted much attention in the field of tissue engineering because of its biocompatibility, biodegradability and so on. However, the intrinsic hydrophobicity and the lacking of active functional groups limit its practical application to some extent. In this study, poly(ethylenimine) (PEI) modified PLLA nanofibrous scaffolds were fabricated in a one step process by aminolysis combined with thermally induced phase separation technique for introducing more functional groups, PEI acting as the modifier. The morphology of PEI-modified PLLA scaffolds prepared under different experimental conditions was analyzed by scanning electron microscope (SEM). The suitable conditions to fabricate scaffolds with a homogeneous nanofibrous structure, good hydrophilicity and excellent mechanical properties were determined according to the results of SEM, water contact angle (WCA) and mechanical properties testing. Besides, Fourier transform infrared spectroscopy (FTIR), proton nuclear magnetic resonance spectroscopy (¹H NMR), X-ray Photoelectron Spectroscopy (XPS) and gel permeation chromatography (GPC) were used to confirm the occurrence of the ammonolysis reaction between PLLA and PEI. The in vitro biomineralization study showed that the PEI-modified PLLA scaffolds had a greater ability to induce the formation of apatite in 1.5SBF than PLLA scaffolds, indicating that the bone-bioactivity of PLLA scaffolds was significantly improved after modification with PEI. Furthermore, cell culture assay revealed that MC3T3-E1 osteoblasts exhibited better proliferation performance on the PEI-modified PLLA scaffolds. All the results implied that the synthesized modified PLLA nanofibrous scaffolds may provide promising applications in bone tissue engineering.     

Functional and morphological characteristics of bovine adrenal chromaffin cells on macroporous poly(D,L-lactide-co-glycolide) scaffolds

Adrenal chromaffin cells (ACCs) secrete several neuroactive substances that are effective in influencing pain sensitivity in the central nervous system as well as enhancing the recovery of the intrinsic nigrostriatal dopaminergic system in patients with Parkinson's disease. ACC transplantation may be upregulated by the use of three-dimensional (3-D) scaffolds. In this study, we determined whether biodegradable poly(D,L-lactic-coglycolic acid) (PLGA) (85:15) sponges could be used as support for chromaffin cells. ACCs were isolated from bovine adrenal glands by standard perfusion (95% purity) followed by additional purification (>99.5% purity). ACC (approximately 5 x 10(5) cells) suspension in collagen (type I) was seeded on prewetted sponges and cultured in DMEM-F12 (1:1) medium (5% fetal bovine serum). The catecholamine and enkephalin levels of the samples were measured by high-performance liquid chromatography and radioimmunoassay. Cell morphology was examined by transmission electron microscopy. Morphological evidence showed prolonged viability of chromaffin cells on scaffolds having pores of 250-400 microm. Cell counts and scanning electron microscopy demonstrated that the majority of seeded cells were located within the scaffold. Chromaffin cells exhibited higher levels of enkephalins and catecholamines on PLGA scaffold compared with their monolayer cultures. By the use of 3-D PLGA as support for ACCs, it is possible to upregulate metabolic function and localize a high number of morphologically healthy-looking cells. Highly purified ACCs cultured on PLGA scaffold may have promise in transplantation studies, because these cells are less immunogenic and may be applied to in vivo settings by using short-term immunosuppression.     

Fabrication and surface modification of macroporous poly(L-lactic acid) and poly(L-lactic-co-glycolic acid) (70/30) cell scaffolds for human skin fibroblast cell culture

The fabrication and surface modification of a porous cell scaffold are very important in tissue engineering. Of most concern are high-density cell seeding, nutrient and oxygen supply, and cell affinity. In the present study, poly(L-lactic acid) and poly(L-lactic-co-glycolic acid) (70/30) cell scaffolds with different pore structures were fabricated. An improved method based on Archimedes' Principle for measuring the porosity of scaffolds, using a density bottle, was developed. Anhydrous ammonia plasma treatment was used to modify surface properties to improve the cell affinity of the scaffolds. The results show that hydrophilicity and surface energy were improved. The polar N-containing groups and positive charged groups also were incorporated into the sample surface. A low-temperature treatment was used to maintain the plasma-modified surface properties effectively. It would do help to the further application of plasma treatment technique. Cell culture results showed that pores smaller than 160 microm are suitable for human skin fibroblast cell growth. Cell seeding efficiency was maintained at above 99%, which is better than the efficiency achieved with the common method of prewetting by ethanol. The plasma-treatment method also helped to resolve the problem of cell loss during cell seeding, and the negative effects of the ethanol trace on cell culture were avoided. The results suggest that anhydrous ammonia plasma treatment enhances the cell affinity of porous scaffolds. Mass transport issues also have been considered.     

New technique of seeding chondrocytes into microporous poly(L-lactide-co-epsilon-caprolactone) sponge by cyclic compression force-induced suction

The initial requirement for a functional engineered cartilage tissue is the effective and reproducible seeding of chondrocytes into the interior of microporous scaffolds. High seeding efficiency, high cell viability, uniform cell distribution, and short operation time are also essential. We devised a new technique of seeding rabbit chondrocytes into microporous poly(L-lactide-co-epsilon-caprolactone) (PLCL) (porosity, 71- 80%; wall thickness, 2 and 6 mm) sponges under compression force-induced suction using a custom designed loading apparatus. Cell distribution and cell viability were determined using confocal laser scanning microscopy with fluorescent dye-staining techniques. Factors that affect the quality of a cell seeded construct were studied, namely, the porosity and thickness of sponges and suction cycles. Under 1 cycle of suction, an increase in porosity promoted cell seeding efficiency (CSE; defined as the percentage of the number of cells in the sponges relative to the initial number of cells seeded), cell viability (at 1 day post seeding), and a relatively uniform cell distribution, whereas thick sponges exhibited an inhomogeneous cell distribution irrespective of incubation time. Multiple cycles of suction of 5 and 10 at 0.1 Hz significantly improved the CSE, whereas high cell viability was maintained and even spatial cell distribution was achieved in 1 week. This study revealed that our newly developed cell seeding technique with multiple cycles of suction is a promising approach to inoculating cells into microporous sponges with high CSE, high cell viability, and homogeneous cell distribution.     

Characterization of electrospun core/shell poly(vinyl pyrrolidone)/poly(L-lactide-co-epsilon-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-epsilon-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.     

Fibrous poly(chitosan-g-DL-lactic acid) scaffolds prepared via electro-wet-spinning

DL-lactic acid was grafted onto chitosan to produce poly(chitosan-g-DL-lactic acid)(PCLA) copolymers. These PCLAs were then spun into submicron and/or nanofibers to fabricate scaffolds using an electro-wet-spinning technique. The diameter of fibers in different scaffolds could vary from about 100 nm to around 3 microm. The scaffolds exhibited various pore sizes ranging from about 1 microm to less than 30 microm and different porosities up to 80%. Two main processing parameters, that is, the concentration of PCLA solutions and the composition proportions of coagulation solutions, were optimized for obtaining desired scaffolds with well-controlled structures. The tensile properties of the scaffolds in both dry and hydrated states were examined. Significantly improved tensile strength and modulus for these fibrous scaffolds in their hydrated state were observed. The data collected from in vitro rabbit-fibroblast/scaffold culture showed that there were no substantial differences in the viability, density and distribution of cultured fibroblasts between PCLA scaffolds and pure chitosan scaffolds.     

Select bladder smooth muscle cell functions were enhanced on three-dimensional,nano-structured poly(ether urethane) scaffolds

Bladder wall resection is often required as a treatment for invasive bladder cancer. When this happens, a suitable replacement material is needed. The present study, therefore, created three-dimensional, porous, nano-structured poly(ether urethane) (PU) matrices for use as bladder tissue-engineering scaffolds. Select cytocompatibility experiments (specifically adhesion and long-term growth studies) were performed on these scaffolds using human bladder smooth muscle cells (BdSMCs). In addition, the amount of total collagen and elastin present in each cell-seeded scaffold was determined since the production of these extracellular matrix (ECM) proteins is essential for the health and survival of cells and for the functionality of the replaced organ. Finally, to better understand how these scaffolds and resident cells would perform in the complex mechanical environment of the bladder wall, scaffolds and cells were subjected to 10 cmH₂O pressure using a computer-controlled pressure chamber. Results provided evidence that compared to conventionally used, micro-dimensional PU scaffolds, the novel, nanodimensional scaffolds created in this research increased cell adhesion, growth, and ECM protein production. Additionally, scaffolds and resident cells were not affected by exposure to 10 cmH₂O pressure (compared to controls maintained under atmospheric conditions). These results are promising and provide evidence that the nano-dimensional PU scaffolds created in this research are suitable bladder replacement materials that may outperform materials currently used for such purposes.