Fibro-porous meshes made from polyurethane micro-fibers: effects of surface charge on tissue response

The purpose of this research was to evaluate the influence of surface charge on fibrous encapsulation, cell nuclei density, and vessel ingrowth into small-fiber, fibro-porous, biomaterial meshes. Meshes electrospun from polyurethane with mean fiber diameters of 5.8 microm and mean fiber spacing of 64.9 microm were plasma coated with films of different relative surface charge: Hexafluoropropylene (HF) (neutral), N,N-dimethylaminoethyl methacrylate (NN) (positive charge), and methacrylic acid (MA) (negative charge). Samples were implanted in rat subcutaneous dorsum for 5 weeks then fibrous capsule presence around the implants, cell nuclei density, and vessel number were assessed. Results showed that within the resolution of the histological analysis methods used, no implant experienced fibrous encapsulation. There was no significant difference between cell nuclei density and coating for the four groups: uncoated, HF-coated, NN-coated, and MA-coated. HF-coated and NN-coated samples had lower vessel numbers than uncoated samples (p = 0.055 and 0.032, respectively). MA-coated samples had vessel numbers not significantly different from uncoated polyurethane (slightly negatively charged) samples (p = 0.879). The results suggest that negatively charged surfaces may facilitate vessel ingrowth into fibro-porous mesh biomaterials.