Electrospun chitosan-P(LLA-CL) nanofibers for biomimetic extracellular matrix

Chitosan-poly(L-lactic acid-co-epsilon-caprolactone)(50:50) (P(LLA-CL)) (CS/P(LLA-CL)) blends were electrospun into nanofibers using 1,1,1,3,3,3-hexafluoro-2-propanol (HFIP) and trifluoroacetic acid (TFA) as solvents. Chitosan, which is difficult to electrospin into nanofibers, could be easily electrospun into nanofibers with addition of a small portion of P(LLA-CL). The fiber diameter depended on both the polymer concentration and the blend ratio of chitosan to P(LLA-CL). The average fiber diameter increased with increasing polymer concentration and decreasing the blend ratio of chitosan to P(LLA-CL). X-ray diffractometry (XRD) and Fourier-transform infrared (FT-IR) spectra were measured to characterize blended nanofibers. The porosity of CS/P(LLA-CL) nanofiber mats increased with increasing the weight ratio of chitosan to P(LLA-CL), while both the tensile strength and the ultimate strain increased with increasing P(LLA-CL) ratio. Fibroblast cell growth on nanofiber mats were investigated with MTT assay and scanning electron microscope (SEM) observation. The highest cell proliferation was observed on the nanofiber mats when the weight ratio of chitosan to P(LLA-CL) was 1:2. As SEM images shown, fibroblast cells showed a polygonal shape on blend nanofiber mats and migrated into the nanofiber mats.     

Electrospun nanofiber fabrication as synthetic extracellular matrix and its potential for vascular tissue engineering

Substantial effort is being invested by the bioengineering community to develop biodegradable polymer scaffolds suitable for tissue-engineering applications. An ideal scaffold should mimic the structural and purposeful profile of materials found in the natural extracellular matrix (ECM) architecture. To accomplish this goal, poly (L-lactide-co-epsilon-caprolactone) [P(LLA-CL)] (75:25) copolymer with a novel architecture produced by an electrospinning process has been developed for tissue-engineering applications. The diameter of this electrospun P(LLA-CL) fiber ranges from 400 to 800 nm, which mimicks the nanoscale dimension of native ECM. The mechanical properties of this structure are comparable to those of human coronary artery. To evaluate the feasibility of using this nanofibrous scaffold as a synthetic extracellular matrix for culturing human smooth muscle cells and endothelial cells, these two types of cells were seeded on the scaffold for 7 days. The data from scanning electron microscopy, immunohistochemical examination, laser scanning confocal microscopy, and a cell proliferation assay suggested that this electrospun nanofibrous scaffold is capable of supporting cell attachment and proliferation. Smooth muscle cells and endothelial cells seeded on this scaffold tend to maintain their phenotypic shape. They were also found to integrate with the nanofibers to form a three-dimensional cellular network. These results indicate a favorable interaction between this synthetic nanofibrous scaffold with the two types of cells and suggest its potential application in tissue engineering a blood vessel substitute.     

聚左旋乳酸/壳聚糖电纺丝纳米纤维支架与兔内皮祖细胞的生物相容性

背景：电纺丝技术能够使许多高分子材料制备出与细胞外基质相似的三维纳米纤维支架。聚乳酸/壳聚糖纳米纤维复合支架材料能够克服材料的不足,提高组织工程支架生物相容性。 目的：评价聚左旋乳酸/壳聚糖电纺丝纳米纤维支架与兔内皮祖细胞的生物相容性。 方法：电纺丝技术制备聚左旋乳酸,壳聚糖,聚左旋乳酸/壳聚糖的纳米纤维支架,扫描电镜观察其形貌结构。纳米纤维支架与内皮祖细胞进行复合培养后,观察细胞在不同材料上的黏附率、一氧化氮分泌,生长特征和在聚左旋乳酸/壳聚糖纳米纤维支架上的细胞表型特征。 结果与结论：聚左旋乳酸/壳聚糖纳米纤维支架比聚左旋乳酸、壳聚糖具有更合适的纤维直径,具有与细胞外基质相似的纳米纤维三维多孔结构。聚左旋乳酸/壳聚糖纳米纤维支架能够促进内皮祖细胞黏附率和细胞的一氧化氮分泌(P < 0.05,P < 0.01)。内皮祖细胞能够在聚左旋乳酸/壳聚糖复合材料膜上融合成片,保持了细胞的完整形态和分化功能,显示了内皮细胞特异性的vWF表型。提示聚左旋乳酸/壳聚糖电纺丝纳米纤维支架与兔内皮祖细胞具有良好的生物相容性。     

Degradation of electrospun nanofiber scaffold by short wave length ultraviolet radiation treatment and its potential applications in tissue engineering

Development in the field of tissue engineering has brought much attention in the fabrication and preparation of scaffold with biodegradable synthetic polymer nanofibers. Electrospun biodegradable polymeric nanofibers are increasingly being used to fabricate scaffolds for tissue engineering applications as they provide high surface area-to-volume ratio and possess high porosity. One common way to sterilize polymeric nanofiber scaffolds is 254-nm ultraviolet (UV) irradiation. In this study, we aim to evaluate the effects of UV radiation on the degradation in polymeric nanofibers, and then capitalize on UV-induced degradation and UV photolithography in polymeric nanofiber scaffolds for tissue engineering applications. Poly(D,L-lactic-co-glycolic) acid (PLGA, 75:25) and poly(L-lactide-co-epsilon-caprolactone) [P(LLA-CL), 70:30] nanofibrous meshes were produced by electrospinning. The nanofibers were irradiated by commercial germicide UV (lambda=254 nm) lamp for different intervals. We found that UV sterilization induced significant degradation of nanofiber. At 1 h UV irradiation, the average molecular weight of PLGA and P(LLA-CL) nanofibers were reduced by 46% and 35%, respectively, with corresponding reduction in the tensile strength of 26% for PLGA and 28% for P(LLA-CL). Hence, precautions may have to be taken into consideration when sterilizing polymeric nanofibers by UV treatment. UV-induced degradation on nanofibers was applied to fabrication of a three-dimensional (3D) tissue engineering scaffold by UV photolithography. Masked exposure to UV could generate patterned holes (d=100 microm) on the nanofibrous mesh. Cell culture study showed that smooth muscle cells were able to migrate into the holes. This method can be used to fabricate a 3D nanofibrous scaffold with micropores.     

The influence of electrospun aligned poly(epsilon-caprolactone)/collagen nanofiber meshes on the formation of self-aligned skeletal muscle myotubes

Current treatment options for restoring large skeletal muscle tissue defects due to trauma or tumor ablation are limited by the host muscle tissue availability and donor site morbidity of muscle flap implantation. Creation of implantable functional muscle tissue that could restore muscle defects may bea possible solution. To engineer functional muscle tissue for reconstruction, scaffolds that mimic native fibers need to be developed. In this study we examined the feasibility of using poly(epsilon-caprolactone) (PCL)/collagen based nanofibers using electrospinning as a scaffold system for implantable engineered muscle. We investigated whether electrospun nanofibers could guide morphogenesis of skeletal muscle cells and enhance cellular organization. Nanofibers with different fiber orientations were fabricated by electrospinning with a blend of PCL and collagen. Human skeletal muscle cells (hSkMCs) were seeded onto the electrospun PCL/collagen nanofiber meshes and analyzed for cell adhesion, proliferation and organization. Our results show that unidirectionally oriented nanofibers significantly induced muscle cell alignment and myotube formation as compared to randomly oriented nanofibers. The aligned composite nanofiber scaffolds seeded with skeletal muscle cells may provide implantable functional muscle tissues for patients with large muscle defects.     

Improvement and Characterization of the Adhesion of Electrospun PLDLA Nanofibers on PLDLA-Based 3D Object Substrates for Orthopedic Application

Abstract

Intensive research has demonstrated the clear biological potential of electrospun nanofibers for tissue regeneration and repair. However, nanofibers alone have limited mechanical properties. In this study we took poly(L-lactide-co-D-lactide) (PLDLA)-based 3D objects, one existing medical device (interference screws) and one medical device model (discs) as examples to form composites through coating their surface with electrospun PLDLA nanofibers. We specifically investigated the effects of electrospinning parameters on the improvement of adhesion of the electrospun nanofibers to the PLDLA-based substrates. To reveal the adhesion mechanisms, a novel peel test protocol was developed for the characterization of the adhesion and delamination phenomenon of the nanofibers deposited to substrates. The effect of incubation of the composites under physiological conditions on the adhesion of the nanofibers has also been studied. It was revealed that reduction of the working distance to 10 cm resulted in deposition of residual solvent during electrospinning of nanofibers onto the substrate, causing fiber–fiber bonding. Delamination of this coating occurred between the whole nanofiber layer and substrate, at low stress. Fibers deposited at 15 cm working distance were of smaller diameter and no residual solvent was observed during deposition. Delamination occurred between nanofiber layers, which peeled off under greater stress. This study represents a novel method for the alteration of nanofiber adhesion to substrates, and quantification of the change in the adhesion state, which has potential applications to develop better medical devices for orthopedic tissue repair and regeneration.     

Biocompatibility,Alignment Degree and Mechanical Properties of an Electrospun Chitosan–P(LLA-CL) Fibrous Scaffold

Chitosan–poly(L-lactide-co-ε-caprolactone) (P(LLA-CL)) complex fibers, fibrous mats and a tubular scaffold have been obtained through electrospinning. Due to their high porosity, there were more porcine iliac artery endothelial cells (PIECs) attached to fiber mats than to tissue-culture plate (TCP) and coverslips. The cells could grow and spread well on nanofiber mats. There were many of native extracellular matrix (ECM)-like colloids above and under the surface of fibrous mats after cell culturing. The two-dimensional fast Fourier transform (2-D FFT) approach was used to analysis alignment degree of fibers collected on a rotary mandrel. The relations among mechanical properties, alignment degree, fiber diameter and rotary speed are discussed. Aligned fibers with various alignment degrees could be found through adjusting rotary speed. Fiber alignment was the variable most closely associated with the regulation of stress and strain. In this study, we show a feasible approach for producing scaffold with controllable mechanical property for soft tissue engineering through electrospinning.     

The design of electrospun PLLA nanofiber scaffolds compatible with serum-free growth of primary motor and sensory neurons

Aligned electrospun nanofibers direct neurite growth and may prove effective for repair throughout the nervous system. Applying nanofiber scaffolds to different nervous system regions will require prior in vitro testing of scaffold designs with specific neuronal and glial cell types. This would be best accomplished using primary neurons in serum-free media; however, such growth on nanofiber substrates has not yet been achieved. Here we report the development of poly(L-lactic acid) (PLLA) nanofiber substrates that support serum-free growth of primary motor and sensory neurons at low plating densities. In our study, we first compared materials used to anchor fibers to glass to keep cells submerged and maintain fiber alignment. We found that poly(lactic-co-glycolic acid) (PLGA) anchors fibers to glass and is less toxic to primary neurons than bandage and glue used in other studies. We then designed a substrate produced by electrospinning PLLA nanofibers directly on cover slips pre-coated with PLGA. This substrate retains fiber alignment even when the fiber bundle detaches from the cover slip and keeps cells in the same focal plane. To see if increasing wettability improves motor neuron survival, some fibers were plasma etched before cell plating. Survival on etched fibers was reduced at the lower plating density. Finally, the alignment of neurons grown on this substrate was equal to nanofiber alignment and surpassed the alignment of neurites from explants tested in a previous study. This substrate should facilitate investigating the behavior of many neuronal types on electrospun fibers in serum-free conditions.     

Electrospun bio-composite P(LLA-CL)/collagen I/collagen III scaffolds for nerve tissue engineering

One of the biggest challenges in peripheral nerve tissue engineering is to create an artificial nerve graft that could mimic the extracellular matrix (ECM) and assist in nerve regeneration. Bio-composite nanofibrous scaffolds made from synthetic and natural polymeric blends provide suitable substrate for tissue engineering and it can be used as nerve guides eliminating the need of autologous nerve grafts. Nanotopography or orientation of the fibers within the scaffolds greatly influences the nerve cell morphology and outgrowth, and the alignment of the fibers ensures better contact guidance of the cells. In this study, poly (L-lactic acid)-co-poly(ε-caprolactone) or P(LLA-CL), collagen I and collagen III are utilized for the fabrication of nanofibers of different compositions and orientations (random and aligned) by electrospinning. The morphology, mechanical, physical, and chemical properties of the electrospun scaffolds along with their biocompatibility using C17.2 nerve stem cells are studied to identify the suitable material compositions and topography of the electrospun scaffolds required for peripheral nerve regeneration. Aligned P(LLA-CL)/collagen I/collagen III nanofibrous scaffolds with average diameter of 253 ± 102 nm were fabricated and characterized with a tensile strength of 11.59 ± 1.68 MPa. Cell proliferation studies showed 22% increase in cell proliferation on aligned P(LLA-CL)/collagen I/collagen III scaffolds compared with aligned pure P(LLA-CL) scaffolds. Results of our in vitro cell proliferation, cell-scaffold interaction, and neurofilament protein expression studies demonstrated that the electrospun aligned P(LLA-CL)/collagen I/collagen III nanofibrous scaffolds mimic more closely towards the ECM of nerve and have great potential as a substrate for accelerated regeneration of the nerve.     

Nanofiber enabled layer-by-layer approach toward three-dimensional tissue formation

Taking rapid and efficient formation of functional tissues as our long-term goal, we discuss in this study a new and generic approach toward formation of multilayered three-dimensional (3D) tissues using nanofibers. 3:1 poly (epsilon-caprolactone) (PCL) (8% w/v)/collagen (8.0% w/v) solution was electrospun into nanofibers with an average diameter of 454.5 +/- 84.9 nm. The culture of human dermal fibroblasts (NHDF) on PCL/collagen nanofibers showed a high initial cell adhesion (88.1 +/- 1.5%), and rapid cell spreading with spindle morphology. Three-dimensional multilayered cell-nanofiber constructs were built with alternating NHDF seeding (1 x 10(5)cells/layer) and PCL/collagen nanofiber collection on site of electrospinning, where almost all the seeded cells retained in the constructs. The formed construct showed layered structure with uniform cell distribution in between layers of PCL/collagen nanofibers. In the 3D constructs, cells continuously proliferated and deposited new extracellular matrix. By culturing either fibroblast/fiber layered constructs or keratinocyte/fibroblast/fiber layered constructs, dermal-like tissues or bilayer skin tissues (containing both epidermal and dermal layers) were consequently produced within 1 week. Taken together, the present study reports a novel approach to 3D multilayered tissue formation using a bottom-up, on-site layer-by-layer cell assembly while electrospinning. This approach has marked potentials to form functional tissues composed of multiple types of cells, heterogeneous scaffold composition, and customized specific microenvironment for cells.     

Preparation and cytocompatibility of PLGA scaffolds with controllable fiber morphology and diameter using electrospinning method

Poly(lactide-co-glycolide) (PLGA) scaffolds prepared by the electrospinning technology were paid more attention in tissue engineering, but detailed investigation on the influence of process parameters on scaffold morphology and fiber diameters as well as distribution remains to be conducted. In the current study, PLGA concentration, electric field strength, and feeding rate were varied to prepare different PLGA scaffolds. It was shown that with the varying of the above parameters, the electrospun porous PLGA scaffolds exhibited fibrous morphology either with/out beads or bead-fiber string. The diameter of nanofibers increased with the PLGA concentration and feeding rate, whereas the electric field strength exerted only minor effects on the average diameter of the nanofibers. The cytocompatibility of the scaffold prepared from optimizing fabrication parameters was evaluated using human fibroblasts. Good cell attachment, fast proliferation rate, characteristic fibroblast morphology with homogeneous distribution was observed on the scaffold. As a whole, this study demonstrated that the fiber morphology and diameter of the electrospun PLGA scaffolds could be tailored by controlling fabrication parameters. And nanofibrous PLGA could act as a biologically preferred scaffold for fibroblasts growth with maintenance of characteristic morphology.     

Electrospinning Thermoplastic Polyurethane-Contained Collagen Nanofibers for Tissue-Engineering Applications

Electrospinning is a new method used in tissue engineering. It can spin fibers in nanoscale by electrostatic force. A series of thermoplastic polyurethane (TPU)/collagen blend nanofibrous membranes was prepared with different weight ratios and concentrations via electrospinning. The two biopolymers used 1,1,1,3,3,3,-hexafluoro-2-propanol (HFP) as solvent. The electrospun TPU-contained collagen nanofibers were characterized using scanning electron microscopy (SEM), XPS spectroscopy, atomic force microscopy, apparent density and porosity measurement, contact-angle measurement, mechanical tensile testing and viability of pig iliac endothelial cells (PIECs) on blended nanofiber mats. Our data indicate that fiber diameter was influenced by both polymer concentration and blend weight ratio of collagen to TPU. The average diameter of nanofibers gradually decreases with increasing collagen content in the blend. XPS analysis indicates that collagen is found to be present at the surface of blended nanofiber. The results of porosity and contact-angle measurement suggest that with the collagen content in the blend system, the porosity and hydrophilicity of the nanofiber mats is greatly improved. We have also characterized the molecular interactions in TPU/collagen complex by Fourier transform infrared spectroscopy (FT-IR). The result could demonstrate that there were no intermolecular bonds between the molecules of TPU and collagen. The ultimate tensile stress and strain were carried out and the data confirmed the FT-IR results. The TPU/collagen blend nanofibrous mats were further investigated as promising scaffold for PIEC culture. The cell proliferation and SEM morphology observations showed that the cells could not only favorably grow well on the surface of blend nanofibrous mats, but also able to migrate inside the scaffold within 24 h of culture. These results suggest that the blend nanofibers of TPU/collagen are designed to mimic the native extracellular matrix for tissue engineering and develop functional biomaterials.     

Electrospinning of silk fibroin nanofibers and its effect on the adhesion and spreading of normal human keratinocytes and fibroblasts in vitro

An electrospinning method was used to fabricate silk fibroin (SF) nanofiber nonwovens for cell culture of normal human keratinocytes and fibroblasts. The electrospinning of regenerated SF was performed with formic acid as a spinning solvent. For insolubilization, as-spun SF nanofiber nonwovens were chemically treated with an aqueous methanol solution of 50%. Morphology and microstructure of as-spun and chemically treated SF nanofibers were investigated by scanning electron microscopy and mercury porosimetry. As-spun SF nanofibers exhibited a circular cross-section with a smooth surface. From the image analysis, they had an average diameter of 80 nm and their diameters ranged from 30 to 120 nm. During the chemical treatment for 60 min, porosity of nonwovens composed of SF nanofibers decreased from 76.1% up to 68.1%. To assay the cytocompatibility and cell behavior onto the electrospun SF nanofibers, cell attachment and spreading of normal human keratinocytes and fibroblasts seeded on the SF nanofibers and interaction between cells and SF nanofibers were studied. Cell morphology on SF nanofibers was examined by scanning electron microscopy. Our results indicate that the SF nanofibers may be a good candidate for the biomedical applications, such as wound dressing and scaffolds for tissue engineering.     

Stable immobilization of rat hepatocyte spheroids on galactosylated nanofiber scaffold

Primary rat hepatocytes self-assemble into multi-cellular spheroids and maintain differentiated functions when cultured on a two-dimensional (2-D) substrate conjugated with galactose ligand. The aim of this study is to investigate how a functional nanofiber scaffold with surface-galactose ligand influences the attachment, spheroid formation and functional maintenance of rat hepatocytes in culture, as compared with the functional 2-D substrate. Highly porous nanofiber scaffolds comprising of fibers with an average diameter of 760 nm were prepared by electrospinning of poly(epsilon-caprolactone-co-ethyl ethylene phosphate) (PCLEEP), a novel biodegradable copolymer. Galactose ligand with a density of 66 nmol/cm(2) was achieved on the nanofiber scaffold via covalent conjugation to a poly(acrylic acid) spacer UV-grafted onto the fiber surface. Hepatocytes cultured on the galactosylated PCLEEP nanofiber scaffold exhibited similar functional profiles in terms of cell attachment, ammonia metabolism, albumin secretion and cytochrome P450 enzymatic activity as those on the functional 2-D substrate, although their morphologies are different. Hepatocytes cultured on galactosylated PCLEEP film formed 50-300 microm spheroids that easily detached from surface upon agitation, whereas hepatocytes cultured on galactosylated nanofiber scaffold formed smaller aggregates of 20-100 microm that engulfed the functional nanofibers, resulting in an integrated spheroid-nanofiber construct.     

Fabricating Microparticles/Nanofibers Composite and Nanofiber Scaffold with Controllable Pore Size by Rotating Multichannel Electrospinning

Polymeric nanofibers fabricated via electrospinning are regarded as promising scaffolds for biomimicking a native extracellular matrix. However, electrospun scaffolds have poor porosity, resulting in cells being unable to infiltrate into the scaffolds but grow only on its surface. In this study, we modified regular electrospinning into rotating multichannel electrospinning (RM-ELSP) to produce microparticles and nanofibers simultaneously. Gelatin nanofibers (0.1–1 μm) and polycaprolactone (PCL) microparticles (0.5–10 μm) were formed and well-mixed. Adjusting the concentration of PCL and/or gelatin, we can fabricate various microparticles/nanofibers composites with different sizes of PCL particles and different diameters of gelatin nanofibers depending on their concentrations (2–10%) during electrospinning. Using PCL particles as a pore generator, we obtained gelatin nanofiber scaffolds with controllable pore size and porosity. Cells adhere and grow into the scaffold easily during in vitro cell culture.     

Biocompatibility of electrospun halloysite nanotube-doped poly(lactic-co-glycolic acid) composite nanofibers

Organic/inorganic hybrid nanofiber systems have generated great interest in the area of tissue engineering and drug delivery. In this study, halloysite nanotube (HNT)-doped poly(lactic-co-glycolic acid) (PLGA) composite nanofibers were fabricated via electrospinning and the influence of the incorporation of HNTs within PLGA nanofibers on their in vitro biocompatibility was investigated. The morphology, mechanical and thermal properties of the composite nanofibers were characterized by scanning electron microscopy (SEM), tensile test, differential scanning calorimetry and thermogravimetric analysis. The adhesion and proliferation of mouse fibroblast cells cultured on both PLGA and HNT-doped PLGA fibrous scaffolds were compared through 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide assay of cell viability and SEM observation of cell morphology. We show that the morphology of the PLGA nanofibers does not appreciably change with the incorporation of HNTs, except that the mean diameter of the fibers increased with the increase of HNT incorporation in the composite. More importantly, the mechanical properties of the nanofibers were greatly improved. Similar to electrospun PLGA nanofibers, HNT-doped PLGA nanofibers were able to promote cell attachment and proliferation, suggesting that the incorporation of HNTs within PLGA nanofibers does not compromise the biocompatibility of the PLGA nanofibers. In addition, we show that HNT-doped PLGA scaffolds allow more protein adsorption than those without HNTs, which may provide sufficient nutrition for cell growth and proliferation. The developed electrospun HNT-doped composite fibrous scaffold may find applications in tissue engineering and pharmaceutical sciences.     

静电纺丝纳米纤维组织工程支架的研究进展

背景：静电纺丝纳米纤维具有促进细胞生长的作用。 目的：描述静电纺纳米支架对细胞生长的促进作用以及静电纺纳米支架孔径大小、机械强度缺陷改进的研究进展。 方法：检索数据库为CNKI数字图书馆全文、PubMed数据库2001至2011年有关静电纺丝和组织工程支架的文献。检索关键词为“组织工程,静电纺丝,支架;electrospinning,tissue engineering scaffolds,nanofiber”。 结果与结论：静电纺丝纳米纤维直径、孔径大小及纤维表面对细胞生长行为有重要影响,小孔径静电纺丝纳米纤维支架不利于细胞浸润生长,且用单一电纺技术制备得到的纳米纤维支架机械性能较差,如何增加静电纺丝纳米纤维支架孔径大小以提高细胞的浸润以及提高其机械性能强度,是目前应用研究应解决的问题。     

Cell infiltration and growth in a low density, uncompressed three-dimensional electrospun nanofibrous scaffold

A limiting factor of traditional electrospinning is that the electrospun scaffolds consist entirely of tightly packed nanofiber layers that only provide a superficial porous structure due to the sheet-like assembly process. This unavoidable characteristic hinders cell infiltration and growth throughout the nanofibrous scaffolds. Numerous strategies have been tried to overcome this challenge, including the incorporation of nanoparticles, using larger microfibers, or removing embedded salt or water-soluble fibers to increase porosity. However, these methods still produce sheet-like nanofibrous scaffolds, failing to create a porous three-dimensional scaffold with good structural integrity. Thus, we have developed a three-dimensional cotton ball-like electrospun scaffold that consists of an accumulation of nanofibers in a low density and uncompressed manner. Instead of a traditional flat-plate collector, a grounded spherical dish and an array of needle-like probes were used to create a Focused, Low density, Uncompressed nanoFiber (FLUF) mesh scaffold. Scanning electron microscopy showed that the cotton ball-like scaffold consisted of electrospun nanofibers with a similar diameter but larger pores and less-dense structure compared to the traditional electrospun scaffolds. In addition, laser confocal microscopy demonstrated an open porosity and loosely packed structure throughout the depth of the cotton ball-like scaffold, contrasting the superficially porous and tightly packed structure of the traditional electrospun scaffold. Cells seeded on the cotton ball-like scaffold infiltrated into the scaffold after 7 days of growth, compared to no penetrating growth for the traditional electrospun scaffold. Quantitative analysis showed approximately a 40% higher growth rate for cells on the cotton ball-like scaffold over a 7 day period, possibly due to the increased space for in-growth within the three-dimensional scaffolds. Overall, this method assembles a nanofibrous scaffold that is more advantageous for highly porous interconnectivity and demonstrates great potential for tackling current challenges of electrospun scaffolds.     

Adhesion and growth of endothelial cell on amphiphilic PU/PS IPN surface: effect of amphiphilic balance and immobilized collagen

The architecture of an engineered tissue substitute plays an important role in modulating tissue growth. A novel poly(D,L-lactide-co-glycolide) (PLGA) structure with a unique architecture produced by an electrospinning process has been developed for tissue-engineering applications. Electrospinning is a process whereby ultra-fine fibers are formed in a high-voltage electrostatic field. The electrospun structure, composed of PLGA fibers ranging from 500 to 800 nm in diameter, features a morphologic similarity to the extracellular matrix (ECM) of natural tissue, which is characterized by a wide range of pore diameter distribution, high porosity, and effective mechanical properties. Such a structure meets the essential design criteria of an ideal engineered scaffold. The favorable cell-matrix interaction within the cellular construct supports the active biocompatibility of the structure. The electrospun nanofibrous structure is capable of supporting cell attachment and proliferation. Cells seeded on this structure tend to maintain phenotypic shape and guided growth according to nanofiber orientation. This novel biodegradable scaffold has potential applications for tissue engineering based upon its unique architecture, which acts to support and guide cell growth.