A comparison of nanoscale and multiscale PCL/gelatin scaffolds prepared by disc-electrospinning.

Electrospinning is a versatile and convenient technology to generate nanofibers suitable for tissue engineering. However, the low production rate of traditional needle electrospinning hinders its applications. Needleless electrospinning is a potential strategy to promote the application of electrospun nanofiber in various fields. In this study, disc-electrospinning (one kind of needleless electrospinning) was conducted to produce poly(ε-caprolactone)/gelatin (PCL/GT) scaffolds of different structure, namely the nanoscale structure constructed by nanofiber and multiscale structure consisting of nanofiber and microfiber. It was found that, due to the inhomogeneity of PCL/GT solution, disc-electrospun PCL-GT scaffold presented multiscale structure with larger pores than that of the acid assisted one (PCL-GT-A). Scanning electron microscopy images indicated the PCL-GT scaffold was constructed by nanofibers and microfibers. Mouse fibroblasts and rat bone marrow stromal cells both showed higher proliferation rates on multiscale scaffold than nanoscale scaffolds. It was proposed that the nanofibers bridged between the microfibers enhanced cell adhesion and spreading, while the large pores on the three dimensional (3D) PCL-GT scaffold provide more effective space for cells to proliferate and migrate. However, the uniform nanofibers and densely packed structure in PCL-GT-A scaffold limited the cells on the surface. This study demonstrated the potential of disc-electrospun PCL-GT scaffold containing nanofiber and microfiber for 3D tissue regeneration.

Fabrication and characterization of vitamin B5 loaded poly (l-lactide-co-caprolactone)/silk fiber aligned electrospun nanofibers for schwann cell proliferation.

Bioengineering strategies for peripheral nerve regeneration have been focusing on the development of alternative treatments for nerve repair. In present study we have blended the Vitamin B5 (50mg) with 8% P(LLA-CL) and P(LLA-CL)/SF solutions and produced aligned electrospun nanofiber mashes and characterized the material for its physiochemical and mechanical characteristics. The vitamin loaded composites nanofibers showed tensile strength of 8.73±1.38 and 8.4±1.37 in P(LLA-CL)/Vt and P(LLA-CL)/SF/Vt nanofibers mashes, respectively. By the addition of vitamin B5 the P(LLA-CL) nanofibers become hydrophilic and the contact angle decreased from 96° to 0° in 6min of duration. The effect of vitamin B5 on Schwann cells proliferation and viability were analyzed by using MTT assay and the number of cells cultured on vitamin loaded nanofiber mashes was significantly higher than the without vitamin loaded nanofiber samples after 5th day (p<0.05) whereas, P (LLA-CL)/SF/Vt exhibit the consistently highest cell numbers after 7th days culture as compare to P (LLA-CL)/Vt. The in vitro vitamin release behavior was observed in PBS solution and released vitamin was calculated by revers phase HPLC method. The sustain release behavior of vitamin B5 were noted higher in P(LLA-CL)/Vt (80%) nanofibers as compared to P (LLA-CL)/SF/Vt (62%) nanofibers after 24h. The present work provided a basis for further studies of this novel aligned nanofibrous material in nerve tissue repair or regeneration.

Superelastic, superabsorbent and 3D nanofiber-assembled scaffold for tissue engineering.

Fabrication of 3D scaffold to mimic the nanofibrous structure of the nature extracellular matrix (ECM) with appropriate mechanical properties and excellent biocompatibility, remain an important technical challenge in tissue engineering. The present study reports the strategy to fabricate a 3D nanofibrous scaffold with similar structure to collagen in ECM by combining electrospinning and freeze-drying technique. With the technique reported here, a nanofibrous structure scaffold with hydrophilic and superabsorbent properties can be readily prepared by Gelatin and Polylactic acid (PLA). In wet state the scaffold also shows a super-elastic property, which could bear a compressive strain as high as 80% and recovers its original shape afterwards. Moreover, after 6 days of culture, L-929 cells grow, proliferate and infiltrated into the scaffold. The results suggest that this 3D nanofibrous scaffold would be promising for varied field of tissue engineering application.

Preparation and characterization of electrospun in-situ cross-linked gelatin-graphite oxide nanofibers.

Electrospun gelatin(Gel) nanofibers scaffold has such defects as poor mechanical property and quick degradation due to high solubility. In this study, the in situ cross-linked electrospinning technique was used for the production of gelatin nanofibers. Deionized water was chosen as the spinning solvent and graphite oxide (GO) was chosen as the enhancer. The morphological structure, porosity, thermal property, moisture absorption, and moisture retention performance, hydrolysis resistance, mechanical property, and biocompatibility of the produced nanofibers were investigated. Compared with in situ cross-linked gelatin nanofibers scaffold, in situ cross-linked Gel-GO nanofibers scaffold has the following features: (1) the hydrophilicity, moisture absorption, and moisture retention performance slightly reduce, while the hydrolysis resistance is improved; (2) the breaking strength, breaking elongation, and Young's modulus are significantly improved; (3) the porosity slightly reduces while the biocompatibility considerably increases. The in situ cross-linked Gel-GO nanofibers scaffold is likely to be applied in such fields as drug delivery and scaffold for skin tissue engineering.

A multi-layered vascular scaffold with symmetrical structure by bi-directional gradient electrospinning.

Multi-layered scaffolds are advantageous in vascular tissue engineering, in consideration of better combination of biomechanics, biocompatibility and biodegradability than the scaffolds with single structure. In this study, a bi-directional gradient electrospinning method was developed to fabricate poly(l-lactide-co-caprolactone) (P(LLA-CL)), collagen and chitosan based tubular scaffold with multi-layered symmetrical structure. The multi-layered composite scaffold showed improved mechanical property and biocompatibility, in comparison to the blended scaffold using the same proportion of raw materials. Endothelialization on the multi-layered scaffold was accelerated owing to the bioactive surface made of pure natural materials. hSMCs growth showed the similar results because of its better biocompatibility. Additionally, fibers morphology change, pH value balance and long term mechanical support results showed that the gradient structure effectively improved biodegradability.

Nerve conduits constructed by electrospun P(LLA-CL) nanofibers and PLLA nanofiber yarns.

Injuries of the peripheral nerve occur commonly in various people of different ages and backgrounds. Generally, surgical repairing, such as suturing the transected nerve stumps and transplanting an autologous nerve graft, is the only choice. However, tissue engineering provides an alternative strategy for regeneration of neural context. Functional nerve conduits with three dimensional (3D) support and guidance structure are badly in need. Herein, a uniform PLLA nanofiber yarn constructed by unidirectionally aligned nanofibers was fabricated via a dual spinneret system, which was subsequently incorporated into a hollow poly(l-lactide-co-caprolactone) (P(LLA-CL)) tube to form a nerve conduit with inner aligned texture. The biocompatibility of the poly(l-lactic acid) (PLLA) yarn was assessed by in vitro experiments. Schwann cells (SCs) presented a better proliferation rate and spread morphology of the PLLA yarn than that of PLLA film. Confocal images indicated that the axon spreads along the length of the yarn. SCs were also cultured in the conduit. The data indicated that SCs proliferated well in the conduit and distributed dispersedly throughout the entire lumen. These results demonstrated the potential of the PLLA nanofiber yarn conduit in nerve regeneration.

Dexamethasone loaded core-shell SF/PEO nanofibers via green electrospinning reduced endothelial cells inflammatory damage.

Silk fibroin (SF)/PEO nanofibers prepared by green electrospinning is safe, non-toxic and environment friendly, it is a potential drug delivery carrier for tissue engineering. In this study, a core-shell nanofibers named as Dex@SF/PEO were obtained by green electrospinning with SF/PEO as the shell and dexamethasone (Dex) in the core. The nanofiber morphology and core-shell structure were studied by Scanning Electron Microscope (SEM) and Transmission Electron Microscope (TEM). The Dex release behavior from the nanofibers was tested by High Performance liquid (HPLC) method. The protective effect of drug loaded nanofibers mats on Porcine hip artery endothelial cells (PIECs) against LPS-induced inflammatory damage were determined by MTT assay. TEM result showed the distinct core-shell structure of nanofibers. In vitro drug release studies demonstrated that dexamethasone can sustain release over 192 h and core-shell nanofibers showed more slow release of Dex compared with the blending electrospinning nanofibers. Anti-inflammatory activity in vitro showed that released Dex can reduce the PIECs inflammatory damage and apoptosis which induced by lipopolysaccharide (LPS). Dex@SF/PEO nanofibers are safe and non-toxic because of no harmful organic solvents used in the preparation, it is a promising environment friendly drug carrier for tissue engineering.

Three-dimensional polycaprolactone scaffold via needleless electrospinning promotes cell proliferation and infiltration.

Electrospinning has been widely used in fabrication of tissue engineering scaffolds. Currently, most of the electrospun nanofibers performed like a conventional two-dimensional (2D) membrane, which hindered their further applications. Moreover, the low production rate of the traditional needle-electrospinning (NE) also limited the commercialization. In this article, disc-electrospinning (DE) was utilized to fabricate a three-dimensional (3D) scaffold consisting of porous macro/nanoscale fibers. The morphology of the porous structure was investigated by scanning electron microscopy images, which showed irregular pores of nanoscale spreading on the surface of DE polycaprolactone (PCL) fibers. Protein adsorption assessment illustrated the porous structure could significantly enhance proteins pickup, which was 55% higher than that of solid fiber scaffolds. Fibroblasts were cultured on the scaffold. The results demonstrated that DE fiber scaffold could enhance initial cell attachment. In the 7 days of culture, fibroblasts grew faster on DE fiber scaffold in comparison with solid fiber, solvent cast (SC) film and TCP. Fibroblasts on DE fibers showed a stretched shape and integrated with the porous surface tightly. Cells were also found to migrate into the DE scaffold up to 800µm. Results supported the use of DE PCL fibers as a 3D tissue engineering scaffold in soft tissue regeneration.

Fabrication of cell penetration enhanced poly (l-lactic acid-co-ɛ-caprolactone)/silk vascular scaffolds utilizing air-impedance electrospinning.

In the vascular prosthetic field, the prevailing thought is that for clinical, long-term success, especially bioresorbable grafts, cellular migration and penetration into the prosthetic structure is required to promote neointima formation and vascular wall development. In this study, we fabricated poly (l-lactic acid-co-ɛ-caprolactone) P(LLA-CL)/silk fibroin (SF) vascular scaffolds through electrospinning using both perforated mandrel subjected to various intraluminal air pressures (0-300kPa), and solid mandrel. The scaffolds were evaluated the cellular infiltration in vitro and mechanical properties. Vascular scaffolds were seeded with smooth muscle cells (SMCs) to evaluate cellular infiltration at 1, 7, and 14 days. The results revealed that air-impedance scaffolds allowed significantly more cell infiltration as compared to the scaffolds fabricated with solid mandrel. Meanwhile, results showed that both mandrel model and applied air pressure determined the interfiber distance and the alignment of fibers in the enhanced porosity regions of the structure which influenced cell infiltration. Uniaxial tensile testing indicated that the air-impedance scaffolds have sufficient ultimate strength, suture retention strength, and burst pressure as well as compliance approximating a native artery. In conclusion, the air-impedance scaffolds improved cellular infiltration without compromising overall biomechanical properties. These results support the scaffold's potential for vascular grafting and in situ regeneration.

The aligned core-sheath nanofibers with electrical conductivity for neural tissue engineering.

Currently, electroactive biomaterials have often been fabricated as tissue engineering scaffolds to provide electrical stimulation for neural tissue engineering. The goal of this work was to study the synergistic effect of electrical stimulation and nerve growth factor (NGF) on neuron growth. The composite meshes of polyaniline (PANi) and well-blended poly(l-lactic acid-co-ε-caprolactone)/silk fibroin (PS) incorporated with nerve growth factor (NGF) were prepared by coaxial electrospinning. The results showed that the increased concentration of PANi had a large effect on the fiber diameter, which was significantly reduced from 683 ± 138 nm to 411 ± 98 nm and then increased to 498 ± 100 nm. The contact angles and Young's modulus decreased to 28.3°± 5.4° and 7.2 ± 1.2 MPa, respectively, and the conductance increased to 30.5 ± 3.1 mS cm-1. The results of the viability and morphology of mouse Schwann cells on the nanofibrous meshes showed that PS-PANi-1 loaded with NGF exhibited the highest cell number after 5 days culture and the aligned nanofibers could guide cell orientation. The synergistic effects of electrical stimulation and NGF were also investigated via the growth and differentiation of rat pheochromocytoma 12 (PC12) cells. The scaffolds loaded with NGF under electrical stimulation could effectively support PC12 neurite outgrowth and increase the percentage of neurite-bearing cells as well as the median neurite length. More importantly, the NGF release from the conductive core-shell structure nanofiber could be increased by electrical stimulation. These promising results demonstrated that there was a potential use of this functional scaffold for nerve tissue regeneration.