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We modified the surface of electrospun poly(caprolactone) (PCL) nanofibers to improve their compatibility with endothelial cells (ECs) and to show the potential application of PCL nanofibers as a blood vessel tissue-engineering scaffold. Nonwoven PCL nanofibers (PCL NF) and aligned PCL nanofibers (APCL NF) were fabricated by electrospinning technology. To graft gelatin on the nanofiber surface, PCL nanofibers were first treated with air plasma to introduce -COOH groups on the surface, followed by covalent grafting of gelatin molecules, using water-soluble carbodiimide as the coupling agent. The chemical change in the material surface during surface modification was confirmed by X-ray photoelectron spectroscopy and quantified by colorimetric methods. ECs were cultured to evaluate the cytocompatibility of surface-modified PCL NF and APCL NF. Gelatin grafting can obviously enhance EC spreading and proliferation compared with the original material. Moreover, gelatin-grafted APCL NF readily orients ECs along the fibers whereas unmodified APCL NF does not. Immunostaining micrographs showed that ECs cultured on gelatin-grafted PCL NF were able to maintain the expression of three characteristic markers: platelet-endothelial cell adhesion molecule 1 (PECAM-1), intercellular adhesion molecule 1 (ICAM-1), and vascular cell adhesion molecule 1 (VCAM-1). The surface-modified PCL nanofibrous material is a potential candidate material in blood vessel tissue engineering.

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Electrospun collagen-blended poly(L-lactic acid)-co-poly(epsilon-caprolactone) [P(LLA-CL), 70:30] nanofiber may have great potential application in tissue engineering because it mimicks the extracellular matrix (ECM) both morphologically and chemically. Blended nanofibers with various weight ratios of polymer to collagen were fabricated by electrospinning. The appearance of the blended nanofibers was investigated by scanning electron microscopy and transmission electron microscopy. The nanofibers exhibited a smooth surface and a narrow diameter distribution, with 60% of the nanofibers having diameters between 100 and 200 nm. Attenuated total reflectance-Fourier transform infrared spectra and X-ray photoelectron spectroscopy verified the existence of collagen molecules on the surface of nanofibers. Human coronary artery endothelial cells (HCAECs) were seeded onto the blended nanofibers for viability, morphogenesis, attachment, and phenotypic studies. Five characteristic endothelial cell (EC) markers, including four types of cell adhesion molecule and one EC-preferential gene (von Willebrand factor), were studied by reverse transcription-polymerase chain reaction. Results showed that the collagen-blended polymer nanofibers could enhance the viability, spreading, and attachment of HCAECs and, moreover, preserve the EC phenotype. The blending electrospinning technique shows potential in refining the composition of polymer nanofibers by adding various ingredients (e.g., growth factors) according to cell types to fabricate tissue-engineering scaffold, particularly blood vessel-engineering scaffold.

Nanofibers exist widely in human tissue with different patterns. Electrospinning nanotechnology has recently gained a new impetus due to the introduction of the concept of biomimetic nanofibers for tissue regeneration. The advanced electrospinning technique is a promising method to fabricate a controllable continuous nanofiber scaffold similar to the natural extracellular matrix. Thus, the biomedical field has become a significant possible application field of electrospun fibers. Although electrospinning has developed rapidly over the past few years, electrospun nanofibers are still at a premature research stage. Further comprehensive and deep studies on electrospun nanofibers are essential for promoting their biomedical applications. Current electrospun fiber materials include natural polymers, synthetic polymers and inorganic substances. This review briefly describes several typically electrospun nanofiber materials or composites that have great potential for tissue regeneration, and describes their fabrication, advantages, drawbacks and future prospects.

The natural extracellular matrix (ECM) is a complex structure that is built to meet the specific requirements of the tissue and organ. Primarily consisting of nanometer diameter fibrils, ECM may contain other vital substances such as proteoglycans, glycosaminoglycan and various minerals. Current research in tissue engineering involves trying to replicate the ECM such that it provides the environment for tissue regeneration. Electrospinning is a versatile process that results in nanofibers by applying a high voltage to electrically charge a liquid. A variety of polymers and other substances have been incorporated into the artificial nanofibrous scaffold. Surface modification and cross-linking of the nanofibers are some ways to improve the biocompatibility and stability of the scaffold. Electrospun scaffolds with oriented nanofibers and other assemblies can be constructed by modifying the electrospinning setup. Using electrospinning, researchers are able to specifically tailor the electrospun scaffold to meet the requirements of the tissue that they seek to regenerate. In vitro and in vivo experiments demonstrate that electrospun scaffolds hold great potential for tissue engineering applications.

Quick establishment of a confluent and stable endothelial cells (ECs) layer in the lumen of vascular grafts is critical for long-term patency of small-diameter vascular grafts. The objective of the study was to fabricate tubular nanofiber scaffolds, incorporate ECs onto the lumen of the scaffolds, and establish an animal model to prove the basic concept of using the scaffolds as vascular grafts. Poly(L-lactic acid)-co-poly(epsilon-caprolactone) P(LLA-CL 70:30) tubular nanofiber scaffolds were fabricated by electrospinning onto a rotating mandrel. Collagen was coated onto the scaffolds after air plasma treatment. Structure and mechanical property of the scaffolds were studied by scanning electron microscopy and tensile stress measurement, respectively. Human coronary artery endothelial cells (HCAECs) were rotationally seeded onto the lumen of the scaffolds at the speed of 6 rpm for 4 h through a customized seeding device, followed with static culture. Results showed evenly distributed and well-spread HCAECs throughout the lumen of the scaffold from 1 day onward to 10 days after seeding. Further, HCAECs maintained phenotypic expression of PECAM-1. To prove the basic concept of using the scaffolds as vascular grafts, acellular tubular P(LLA-CL) nanofiber scaffolds (inner diameter 1 mm) were implanted into rabbits to replace the inferior superficial epigastric veins. Results showed the scaffolds sustained the surgical process, kept the structure integrity, and showed the patency for 7 weeks.

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