This study describes the preparation and characterization of nanofibrous mats obtained by electrospinning poly(ethylene terephthalate) (PET) solutions in trifluoroacetic acid/dichloromethane (TFA/DCM). Special attention was paid to the effect of polymer concentration and solvent properties on the morphology, structure, and mechanical and thermal properties of the electrospun nonwovens. The results show that the spinnable concentration of PET solution in TFA/DCM solvents is above 10 wt %. Mats have nanofibrous morphology with fibers having an average diameter in the range of 200–700 nm (depending on polymer concentration and solvent composition) and an interconnected pore structure. Higher solution concentration favors the formation of uniform fibers without beads and with higher diameter. Morphology and fiber assembly changed with the solvent properties. Solvent mixtures rich in TFA, i.e., those with higher dielectric constant and lower surface tension, originated fibers with small diameter. However, due to the lower volatility, those solvent mixtures also produced more branched and crosslinking fibers, with less morphologic uniformity. Mechanical properties (Young's modulus, ultimate strength, and elongation at break) and thermal properties (glass transition, crystallization, and melting) have been studied for the PET electrospun nanomats and compared with those of the original polymer. Solvent effect on fiber crystallinity was not significant, but a complex effect was observed on the mechanical properties of the electrospun mats, as a consequence of the different structural organization of the fibers within the mat network. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 460–471, 2008

Nanotechnology is an exciting emerging field with multiple applications in skin regeneration. Nanofibers have gained special attention in skin regeneration based on their structural similarity to the extracellular matrix. A wide variety of polymeric nanofibers with distinct properties have been developed and tested as scaffolds for skin regeneration. Besides providing support for tissue repair, nanofibrous materials can act as delivery systems for drugs, proteins, growth factors, and other molecules. Moreover, the morphology, biodegradability, and other functionalities of nanofibrous materials can be controlled towards specific conditions of wound healing. Other nanostructured drug delivery systems, such as nanoparticles, micelles, nanoemulsions, and liposomes, have been used to improve wound healing at different stages. These nanoscale delivery systems have demonstrated several benefits for the wound healing process, including reduced cytotoxicity of drugs, administration of poorly water-soluble drugs, improved skin penetration, controlled release properties, antimicrobial activity, and protection of drugs against light, temperature, enzymes or pH degradation, as well as stimulation of fibroblast proliferation and reduced inflammation.

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Electrospun materials have been widely explored for biomedical applications because of their advantageous characteristics, i.e., tridimensional nanofibrous structure with high surface-to-volume ratio, high porosity, and pore interconnectivity. Furthermore, considering the similarities between the nanofiber networks and the extracellular matrix (ECM), as well as the accepted role of changes in ECM for hernia repair, electrospun polymer fiber assemblies have emerged as potential materials for incisional hernia repair. In this work, we describe the application of electrospun non-absorbable mats based on poly(ethylene terephthalate) (PET) in the repair of abdominal defects, comparing the performance of these meshes with that of a commercial polypropylene mesh and a multifilament PET mesh. PET and PET/chitosan electrospun meshes revealed good performance during incisional hernia surgery, post-operative period, and no evidence of intestinal adhesion was found. The electrospun meshes were flexible with high suture retention, showing tensile strengths of 3 MPa and breaking strains of 8–33%. Nevertheless, a significant foreign body reaction (FBR) was observed in animals treated with the nanofibrous materials. Animals implanted with PET and PET/chitosan electrospun meshes (fiber diameter of 0.71±0.28 µm and 3.01±0.72 µm, respectively) showed, respectively, foreign body granuloma formation, averaging 4.2-fold and 7.4-fold greater than the control commercial mesh group (Marlex). Many foreign body giant cells (FBGC) involving nanofiber pieces were also found in the PET and PET/chitosan groups (11.9 and 19.3 times more FBGC than control, respectively). In contrast, no important FBR was observed for PET microfibers (fiber diameter = 18.9±0.21 µm). Therefore, we suggest that the reduced dimension and the high surface-to-volume ratio of the electrospun fibers caused the FBR reaction, pointing out the need for further studies to elucidate the mechanisms underlying interactions between cells/tissues and nanofibrous materials in order to gain a better understanding of the implantation risks associated with nanostructured biomaterials.

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