Technological advances in electrospinning of nanofibers.

Progress in the electrospinning techniques has brought new methods for the production and construction of various nanofibrous assemblies. The parameters affecting electrospinning include electrical charges on the emerging jet, charge density and removal, as well as effects of external perturbations. The solvent and the method of fiber collection also affect the construction of the final nanofibrous architecture. Various techniques of yarn spinning using solid and liquid surfaces as well as surface-free collection are described and compared in this review. Recent advances allow production of 3D nanofibrous scaffolds with a desired microstructure. In the area of tissue regeneration and bioengineering, 3D scaffolds should bring nanofibrous technology closer to clinical applications. There is sufficient understanding of the electrospinning process and experimental results to suggest that precision electrospinning is a real possibility.

Biodegradable polymer nanofiber mesh to maintain functions of endothelial cells.

Maintaining functions of endothelial cells in vitro is a prerequisite for effective endothelialization of biomaterials as an approach to prevent intimal hyperplasia of small-diameter vascular grafts. The aim of this study was to design suitable nanofiber meshes (NFMs) that further maintain the phenotype and functions of human coronary artery endothelial cells (HCAECs). Collagen-coated random and aligned poly(L-lactic acid)-co-poly(epsilon-caprolactone) (P(LLA-CL)) NFMs were fabricated using electrospinning. Mechanical testing showed that tensile modulus and strength were greater for the aligned P(LLA-CL) NFM than for the random NFM. Spatial distribution of the collagen in the NFMs was visualized by labeling with fluorescent dye. HCAECs grew along the direction of nanofiber alignment and showed elongated morphology that simulated endothelial cells in vivo under blood flow. Both random and aligned P(LLA-CL) NFMs preserved phenotype (expression of platelet endothelial cell adhesion molecule-1, fibronectin, and collagen type IV in protein level) and functions (complementary DNA microarray analysis of 112 genes relevant to endothelial cell functions) of HCAECs. The P(LLA-CL) NFMs are potential materials for tissue-engineered vascular grafts that may enable effective endothelialization.

Potential of nanofiber matrix as tissue-engineering scaffolds.

Tissue-engineering scaffolds should be analogous to native extracellular matrix (ECM) in terms of both chemical composition and physical structure. Polymeric nanofiber matrix is similar, with its nanoscaled nonwoven fibrous ECM proteins, and thus is a candidate ECM-mimetic material. Techniques such as electrospinning to produce polymeric nanofibers have stimulated researchers to explore the application of nanofiber matrix as a tissue-engineering scaffold. This review covers the preparation and modification of polymeric nanofiber matrix in the development of future tissue-engineering scaffolds. Major emphasis is also given to the development and applications of aligned, core shell-structured, or surface-functionalized polymer nanofibers. The potential application of polymer nanofibers extends far beyond tissue engineering. Owing to their high surface area, functionalized polymer nanofibers will find broad applications as drug delivery carriers, biosensors, and molecular filtration membranes in future.

Structure and properties of electrospun PLLA single nanofibres.

An electrospinning method was used to spin semi-crystalline poly(L-lactide) (PLLA) nanofibres. Processing parameter effects on the internal molecular structure of electrospun PLLA fibres were investigated by x-ray diffraction (XRD) and differential scanning calorimetry (DSC). Take-up velocity was found as a dominant parameter to induce a highly ordered molecular structure in the electrospun PLLA fibres compared to solution conductivity and polymer concentration, although these two parameters played an important role in controlling the fibre diameter. A collecting method of a single nanofibre by an electrospinning process was developed for the tensile tests to investigate structure-property relationships of the polymer nanofibres. The tensile test results indicated that higher take-up velocity caused higher tensile modulus and strength due to the ordered structure developed through the process.

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.