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

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

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.     

Electrospun PLGA nanofiber scaffolds for articular cartilage reconstruction: mechanical stability, degradation and cellular responses under mechanical stimulation in vitro

We investigated the potential of a nanofiber-based poly(DL-lactide-co-glycolide) (PLGA) scaffold to be used for cartilage reconstruction. The mechanical properties of the nanofiber scaffold, degradation of the scaffold and cellular responses to the scaffold under mechanical stimulation were studied. Three different types of scaffold (lactic acid/glycolic acid content ratio = 75 : 25, 50 : 50, or a blend of 75 : 25 and 50 : 50) were tested. The tensile modulus, ultimate tensile stress and corresponding strain of the scaffolds were similar to those of skin and were slightly lower than those of human cartilage. This suggested that the nanofiber scaffold was sufficiently mechanically stable to withstand implantation and to support regenerated cartilage. The 50 : 50 PLGA scaffold was degraded faster than 75 : 25 PLGA, probably due to the higher hydrophilic glycolic acid content in the former. The nanofiber scaffold was degraded faster than a block-type scaffold that had a similar molecular weight. Therefore, degradation of the scaffold depended on the lactic acid/glycolic acid content ratio and might be controlled by mixing ratio of blend PLGA. Cellular responses were evaluated by examining toxicity, cell proliferation and extracellular matrix (ECM) formation using freshly isolated chondrocytes from porcine articular cartilage. The scaffolds were non-toxic, and cell proliferation and ECM formation in nanofiber scaffolds were superior to those in membrane-type scaffolds. Intermittent hydrostatic pressure applied to cell-seeded nanofiber scaffolds increased chondrocyte proliferation and ECM formation. In conclusion, our nanofiber-based PLGA scaffold has the potential to be used for cartilage reconstruction.     

Electrospun PLGA nanofiber scaffolds for articular cartilage reconstruction: mechanical stability,degradation and cellular responses under mechanical stimulation in vitro

We investigated the potential of a nanofiber-based poly(DL-lactide-co-glycolide) (PLGA) scaffold to be used for cartilage reconstruction. The mechanical properties of the nanofiber scaffold, degradation of the scaffold and cellular responses to the scaffold under mechanical stimulation were studied. Three different types of scaffold (lactic acid/glycolic acid content ratio = 75 : 25, 50 : 50, or a blend of 75 : 25 and 50 : 50) were tested. The tensile modulus, ultimate tensile stress and corresponding strain of the scaffolds were similar to those of skin and were slightly lower than those of human cartilage. This suggested that the nanofiber scaffold was sufficiently mechanically stable to withstand implantation and to support regenerated cartilage. The 50 : 50 PLGA scaffold was degraded faster than 75 : 25 PLGA, probably due to the higher hydrophilic glycolic acid content in the former. The nanofiber scaffold was degraded faster than a block-type scaffold that had a similar molecular weight. Therefore, degradation of the scaffold depended on the lactic acid/glycolic acid content ratio and might be controlled by mixing ratio of blend PLGA. Cellular responses were evaluated by examining toxicity, cell proliferation and extracellular matrix (ECM) formation using freshly isolated chondrocytes from porcine articular cartilage. The scaffolds were non-toxic, and cell proliferation and ECM formation in nanofiber scaffolds were superior to those in membrane-type scaffolds. Intermittent hydrostatic pressure applied to cell-seeded nanofiber scaffolds increased chondrocyte proliferation and ECM formation. In conclusion, our nanofiber-based PLGA scaffold has the potential to be used for cartilage reconstruction.     

Poly(3-hydroxybutyrate-co-3-hydroxyvalerate)-based nanofibrous scaffolds to support functional esophageal epithelial cells towards engineering the esophagus

Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) and PHBV–gelatin were electrospun to obtain defect-free nanofibers by optimizing various process and solution parameters. Tensile strength, Young’s modulus, and wettability of PHBV–gelatin nanofibrous scaffold were determined and compared with PHBV nanofibrous scaffold. Our results demonstrate that PHBV–gelatin nanofibers exhibited higher tensile strength and Young’s modulus than the PHBV nanofibers. Human esophageal epithelial cells (HEEpiC) were cultured on PHBV and PHBV–gelatin nanofiber showed better cell proliferation in PHBV nanofibrous scaffold than the PHBV–gelatin scaffold after 7?days of culture. HEEpiC cultured on PHBV and PHBV–gelatin nanofibrous scaffold exhibited characteristic epithelial cobblestone morphology after 3 days of culture. Further, the HEEpiC extracellular matrix (ECM) proteins (collagen type IV and laminin) and phenotypic marker proteins (cytokeratin-4 and 14) expressions were significantly higher in PHBV–gelatin nanofibrous scaffold than the PHBV nanofiber scaffold. However, the long-term stability and functional state of the cells on the PHBV scaffold give it an edge over the blend scaffolds. Thus, PHBV-based nanofibrous scaffolds could be explored further as ECM substitutes for the regeneration of esophageal tissue.     

Biocompatibility evaluation of emulsion electrospun nanofibers using osteoblasts for bone tissue engineering

Emulsion electrospinning is an advanced technique to fabricate core-shell structured nanofibrous scaffolds, with great potential for drug encapsulation. Incorporation of dual factors hydroxyapatite (HA) and laminin, respectively, within the shell and core of nanofibers through emulsion electrospinning might be of advantageous in supporting the adhesion, proliferation, and maturation of cells instead of single factor-encapsulated nanofibers. We fabricated poly(L-lactic acid-co-?-caprolactone) (PLCL)/hydroxyapaptite (PLCL/HA), PLCL/laminin (PLCL/Lam), and PLCL/hydroxyapatite/laminin (PLCL/HA/Lam) scaffolds with fiber diameter of 388?±?35, 388?±?81, and 379?±?57?nm, respectively, by emulsion electrospinning. The elastic modulus of the prepared scaffolds ranged from 22.7–37.0?MPa. The osteoblast proliferation on PLCL/HA/Lam scaffolds, determined on day 21, was found 10.4% and 12.0% higher than the cell proliferation on PLCL/Lam or PLCL/HA scaffold, respectively. Cell maturation determined on day 14, by alkaline phosphatase (ALP) activity, was significantly higher on PLCL/HA/Lam scaffolds than the ALP activity on PLCL/HA and PLCL/Lam scaffolds (p???0.05). Results of the energy dispersive X-ray studies carried out on day 28 also showed higher calcium deposition by cells seeded on PLCL/HA/Lam scaffolds. Osteoblasts were found to adhere, proliferate, and mature actively on PLCL/HA/Lam nanofibers with enhanced cell proliferation, ALP activity, bone protein expression, and mineral deposition. Based on the results, we can conclude that laminin and HA individually played roles in osteoblast proliferation and maturation, and the synergistic function of both factors within the novel emulsion electrospun PLCL/HA/Lam nanofibers enhanced the functionality of osteoblasts, confirming their potential application in bone tissue regeneration.     

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.     

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.     

Electrospinning polyaniline-contained gelatin nanofibers for tissue engineering applications

Polyaniline (PANi), a conductive polymer, was blended with a natural protein, gelatin, and co-electrospun into nanofibers to investigate the potential application of such a blend as conductive scaffold for tissue engineering purposes. Electrospun PANi-contained gelatin fibers were characterized using scanning electron microscopy (SEM), electrical conductivity measurement, mechanical tensile testing, and differential scanning calorimetry (DSC). SEM analysis of the blend fibers containing less than 3% PANi in total weight, revealed uniform fibers with no evidence for phase segregation, as also confirmed by DSC. Our data indicate that with increasing the amount of PANi (from 0 to approximately 5%w/w), the average fiber size was reduced from 803+/-121 nm to 61+/-13 nm (p<0.01) and the tensile modulus increased from 499+/-207 MPa to 1384+/-105 MPa (p<0.05). The results of the DSC study further strengthen our notion that the doping of gelatin with a few % PANi leads to an alteration of the physicochemical properties of gelatin. To test the usefulness of PANi-gelatin blends as a fibrous matrix for supporting cell growth, H9c2 rat cardiac myoblast cells were cultured on fiber-coated glass cover slips. Cell cultures were evaluated in terms of cell proliferation and morphology. Our results indicate that all PANi-gelatin blend fibers supported H9c2 cell attachment and proliferation to a similar degree as the control tissue culture-treated plastic (TCP) and smooth glass substrates. Depending on the concentrations of PANi, the cells initially displayed different morphologies on the fibrous substrates, but after 1 week all cultures reached confluence of similar densities and morphology. Taken together these results suggest that PANi-gelatin blend nanofibers might provide a novel conductive material well suited as biocompatible scaffolds for tissue engineering.     

Selective functionalization of nanofiber scaffolds to regulate salivary gland epithelial cell proliferation and polarity

Epithelial cell types typically lose apicobasal polarity when cultured on 2D substrates, but apicobasal polarity is required for directional secretion by secretory cells, such as salivary gland acinar cells. We cultured salivary gland epithelial cells on poly(lactic-co-glycolic acid) (PLGA) nanofiber scaffolds that mimic the basement membrane, a specialized extracellular matrix, and examined cell proliferation and apicobasal polarization. Although cells proliferated on nanofibers, chitosan-coated nanofiber scaffolds stimulated proliferation of salivary gland epithelial cells. Although apicobasal cell polarity was promoted by the nanofiber scaffolds relative to flat surfaces, as determined by the apical localization of ZO-1, it was antagonized by the presence of chitosan. Neither salivary gland acinar nor ductal cells fully polarized on the nanofiber scaffolds, as determined by the homogenous membrane distribution of the mature tight junction marker, occludin. However, nanofiber scaffolds chemically functionalized with the basement membrane protein, laminin-111, promoted more mature tight junctions, as determined by apical localization of occludin, but did not affect cell proliferation. To emulate the multifunctional capabilities of the basement membrane, bifunctional PLGA nanofibers were generated. Both acinar and ductal cell lines responded to signals provided by bifunctional scaffolds coupled to chitosan and laminin-111, demonstrating the applicability of such scaffolds for epithelial cell types.     

Cooperative effect of heparan sulfate and laminin mimetic peptide nanofibers on the promotion of neurite outgrowth

Extracellular matrix contains an abundant variety of signals that are received by cell surface receptors contributing to cell fate, via regulation of cellular activities such as proliferation, migration and differentiation. Cues from extracellular matrix can be used for the development of materials to direct cells into their desired fate. Neural extracellular matrix (ECM) is rich in axonal growth inducer proteins, and by mimicking these permissive elements in the cellular environment, neural differentiation as well as neurite outgrowth can be induced. In this paper, we used a synthetic peptide nanofiber system that can mimic not only the activity of laminin, an axonal growth-promoting constituent of the neural ECM, but also the activity of heparan sulfate proteoglycans in order to induce neuritogenesis. Heparan sulfate mimetic groups that were utilized in our system have an affinity to growth factors and induce the neuroregenerative effect of laminin mimetic peptide nanofibers. The self-assembled peptide nanofibers with heparan sulfate mimetic and laminin-derived epitopes significantly promoted neurite outgrowth by PC-12 cells. In addition, these scaffolds were even effective in the presence of chondroitin sulfate proteoglycans (CSPGs), which are the major inhibitory components of the central nervous system. In the presence of these nanofibers, cells could overcome CSPG inhibitory effect and extend neurites on peptide nanofiber scaffolds.     

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.     

Manufacture of elastic biodegradable PLCL scaffolds for mechano-active vascular tissue engineering

A soft and very elastic poly(lactide-co-epsilon-caprolactone) (PLCL)(50:50, Mn 185 x 10(3)) was synthesized. Tubular scaffolds were prepared by an extrusion-particulate leaching method for mechano-active vascular tissue engineering. The copolymer was very flexible but completely rubber-like elastic. Even the high porous PLCL scaffolds (90% salt wt) exhibited 200% elongation, but recovery over 85% in a tensile test. Moreover, the PLCL scaffolds maintained their high elasticity also in culture media under cyclic mechanical strain conditions. The highly porous scaffold (90% salt wt) withstood for an initial 1 week without any deformation and sustained for 2 weeks in culture media under cyclic stress of 10% amplitude and at 1 Hz frequency which are similar to the natural vascular conditions. Vascular smooth muscle cells (VSMCs) were seeded on to the PLCL scaffolds. The cell adhesion and proliferation on the scaffolds of various pore-size were increased with increasing pore size. For the pore sizes of 50-100 microm, 100-150 microm, 150-200 microm and 200-250 microm, the ratios of cell numbers were about 1:1.2:1.9:2.2, respectively, at both 12 h and 5 days. Similarly, the higher porous scaffolds exhibited more cell adhesion and proliferation compared to lower porous one, where the effect was more pronounced in the longer proliferation period. SMC-seeded scaffolds were implanted subcutaneously in athymic nude mice to confirm the biocompatibility. Such a high elastic property and proper biocompatibility to SMCs of PLCL scaffolds prepared in this study will be very useful to engineer SM-containing tissues such as blood vessels under mechanically dynamic environments (mechano-active tissue engineering).     

Beneficial effect of aligned nanofiber scaffolds with electrical conductivity for the directional guide of cells

Abstract

Conducting polymer-based scaffolds receive biological and electrical signals from the extracellular matrix (ECM) or peripheral cells, thereby promoting cell growth and differentiation. Chitin, a natural polymer, is widely used as a scaffold because it is biocompatible, biodegradable, and nontoxic. In this study, we used an electrospinning technique to fabricate conductive scaffolds from aligned chitin/polyaniline (Chi/PANi) nanofibers for the directional guidance of cells. Pure chitin and random and aligned Chi/PANi nanofiber scaffolds were characterized using field emission scanning electron microscope (FE-SEM) and by assessing wettability, mechanical properties, and electrical conductivity. The diameters of aligned Chi/PANi nanofibers were confirmed to be smaller than those of pure chitin and random nanofibers owing to electrostatic forces and stretching produced by rotational forces of the drum collector. The electrical conductivity of aligned Chi/PANi nanofiber scaffolds was ~91% higher than that of random nanofibers. We also studied the viability of human dermal fibroblasts (HDFs) cultured on Chi/PANi nanofiber scaffolds in vitro using a CCK-8 assay, and found that cell viability on the aligned Chi/PANi nanofiber scaffolds was ~2.1-fold higher than that on random Chi/PANi nanofiber scaffolds after 7 days of culture. Moreover, cells on aligned nanofiber scaffolds spread in the direction of the aligned nanofibers (bipolar), whereas cells on the random nanofibers showed no spreading (6 h of culture) or multipolar patterns (7 days of culture). These results suggest that aligned Chi/PANi nanofiber scaffolds with conductivity exert effects that could improve survival and proliferation of cells with directionality.     

PCL–gelatin composite nanofibers electrospun using diluted acetic acid–ethyl acetate solvent system for stem cell-based bone tissue engineering

Composite nanofibrous scaffolds with various poly(ε-caprolactone) (PCL)/gelatin ratios (90:10, 80:20, 70:30, 60:40, 50:50 wt.%) were successfully electrospun using diluted acetic and ethyl acetate mixture. The effects of this solvent system on the solution properties of the composites and its electrospinning properties were investigated. Viscosity and conductivity of the solutions, with the addition of gelatin, allowed for the electrospinning of uniform nanofibers with increasing hydrophilicity and degradation. Composite nanofibers containing 30 and 40 wt.% gelatin showed an optimum combination of hydrophilicity and degradability and also maintained the structural integrity of the scaffold. Human mesenchymal stem cells (hMSCs) showed favorable interaction with and proliferation on, the composite scaffolds. hMSC proliferation was highest in the 30 and 40 wt.% gelatin containing composites. Our experimental data suggested that PCL–gelatin composite nanofibers containing 30–40 wt.% of gelatin and electrospun in diluted acetic acid–ethyl acetate mixture produced nanofiber scaffolds with optimum hydrophilicity, degradability, and bio-functionality for stem cell-based bone tissue engineering.     

Novel chitosan-based hyaluronan hybrid polymer fibers as a scaffold in ligament tissue engineering

To clarify the feasibility of using novel chitosan-based hyaluronan hybrid polymer fibers as a scaffold in ligament tissue engineering, their mechanical properties and ability to promote cellular adhesion, proliferation, and extracellular matrix production were studied in vitro. Chitosan fibers and chitosan-based 0.05% and 0.1% hyaluronan hybrid fibers were developed by the wet spinning method. Hyaluronan coating significantly increased mechanical properties, compared to the chitosan fibers. Rabbit fibroblasts adhesion onto hybrid fibers was significantly greater than for the control and chitosan fibers. For analysis of cell proliferation and extracellular matrix production, a three-dimensional scaffold was created by simply piling up each fiber. At 1 day after cultivation, the DNA content in the hybrid scaffolds was higher than that in the chitosan scaffold. Scanning electron microscopy showed that the fibroblasts had produced collagen fibers after 14 days of culture. Immunostaining for type I collagen was clearly predominant in the hybrid scaffolds, and the mRNA level of type I collagen in the hybrid scaffolds were significantly greater than that in the chitosan scaffold. The present study revealed that hyaluronan hybridization with chitosan fibers enhanced fiber mechanical properties and in vitro biological effects on the cultured fibroblasts.     

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.     

Engineering hybrid polymer-protein super-aligned nanofibers via rotary jet spinning

Cellular microenvironments are important in coaxing cells to behave collectively as functional, structured tissues. Important cues in this microenvironment are the chemical, mechanical and spatial arrangement of the supporting matrix in the extracellular space. In engineered tissues, synthetic scaffolding provides many of these microenvironmental cues. Key requirements are that synthetic scaffolds should recapitulate the native three-dimensional (3D) hierarchical fibrillar structure, possess biomimetic surface properties and demonstrate mechanical integrity, and in some tissues, anisotropy. Electrospinning is a popular technique used to fabricate anisotropic nanofiber scaffolds. However, it suffers from relatively low production rates and poor control of fiber alignment without substantial modifications to the fiber collector mechanism. Additionally, many biomaterials are not amenable for fabrication via high-voltage electrospinning methods. Hence, we reasoned that we could utilize rotary jet spinning (RJS) to fabricate highly aligned hybrid protein-polymer with tunable chemical and physical properties. In this study, we engineered highly aligned nanofiber constructs with robust fiber alignment from blends of the proteins collagen and gelatin, and the polymer poly-ε-caprolactone via RJS and electrospinning. RJS-spun fibers retain greater protein content on the surface and are also fabricated at a higher production rate compared to those fabricated via electrospinning. We measured increased fiber diameter and viscosity, and decreasing fiber alignment as protein content increased in RJS hybrid fibers. RJS nanofiber constructs also demonstrate highly anisotropic mechanical properties mimicking several biological tissue types. We demonstrate the bio-functionality of RJS scaffold fibers by testing their ability to support cell growth and maturation with a variety of cell types. Our highly anisotropic RJS fibers are therefore able to support cellular alignment, maturation and self-organization. The hybrid nanofiber constructs fabricated by RJS therefore have the potential to be used as scaffold material for a wide variety of biological tissues and organs, as an alternative to electrospinning.     

Neural mechanisms of subliminal priming for traumatic episodic memory: an ERP study

Nerve regeneration and functional recovery have been a major issue following injury of nerve tissues. Electrospun nanofibers are known to be suitable scaffolds for neural tissue engineering applications. In addition, modified substrates often provide better environments for neurite outgrowth. This study was conducted to determine if multi-walled carbon nanotubes (MWCNTs)-coated electrospun poly (l-lactic acid-co-caprolactone) (PLCL) nanofibers improved the neurite outgrowth of rat dorsal root ganglia (DRG) neurons and focal adhesion kinase (FAK) expression of PC-12 cells. To accomplish this, the DRG neurons in either uncoated PLCL scaffolds (PLCL group) or MWCNTs-coated PLCL scaffolds (PLCL/CNT group) were cultured for nine days. MWCNTs-coated PLCL scaffolds showed improved neurite outgrowth of DRG neurons. Moreover, FAK expression was up-regulated in the PLCL/CNT group when compared to the PLCL group in a non-time-dependent manner. These findings suggest that MWCNTs-coated nanofibrous scaffolds may be alternative materials for nerve regeneration and functional recovery in neural tissue engineering.     

Synergic effects of nanofiber alignment and electroactivity on myoblast differentiation

The interactions between cells and materials play critical roles in the success of new scaffolds for tissue engineering, since chemical and physical properties of biomaterials regulate cell adhesion, proliferation, migration, and differentiation. We have developed nanofibrous substrates that possess both topographical cues and electroactivity. The nanofiber scaffolds were fabricated through the electrospinning of polycaprolactone (PCL, a biodegradable polymer) and polyaniline (PANi, a conducting polymer) blends. We investigated the ways in which those properties influenced myoblast behaviors. Neither nanofiber alignment nor PANi concentration influenced cell growth and proliferation, but cell morphology changed significantly from multipolar to bipolar with the anisotropy of nanofibers. According to our analyses of myosin heavy chain expression, multinucleate myotube formation, and the expression of differentiation-specific genes (myogenin, troponin T, MHC), the differentiation of myoblasts on PCL/PANi nanofibers was strongly dependent on both nanofiber alignment and PANi concentration. Our results suggest that topographical cues and the electroactivity of nanofibers synergistically stimulate muscle cell differentiation to make PCL/PANi nanofibers a suitable scaffold material for skeletal tissue engineering.