Foreign body reaction associated with PET and PET/chitosan electrospun nanofibrous abdominal meshes.

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.

Nanofiber density determines endothelial cell behavior on hydrogel matrix.

When cultured under static conditions, bacterial cellulose pellicles, by the nature of the polymer synthesis that involves molecular oxygen, are characterized by two distinct surface sides. The upper surface is denser in fibers (entangled) than the lower surface that shows greater surface porosity. Human umbilical vein endothelial cells (HUVECs) were used to exploit how the microarchitecture (i.e., surface porosity, fiber network structure, surface topology, and fiber density) of bacterial cellulose pellicle surfaces influence cell-biomaterial interaction and therefore cell behavior. Adhesion, cell ingrowth, proliferation, viability and cell death mechanisms were evaluated on the two pellicle surface sides. Cell behavior, including secondary necrosis, is influenced only by the microarchitecture of the surface, since the biomaterial is extremely pure (constituted of cellulose and water only). Cell-cellulose fiber interaction is the determinant signal in the cell-biomaterial responses, isolated from other frequently present interferences such as protein and other chemical traces usually present in cell culture matrices. Our results suggest that microarchitecture of hydrogel materials might determine the performance of biomedical products, such as bacterial cellulose tissue engineering constructs (BCTECs).

Manipulation of chemical composition and architecture of non-biodegradable poly(ethylene terephthalate)/chitosan fibrous scaffolds and their effects on L929 cell behavior.

Microporous, non-woven fibrous scaffolds made of poly(ethylene terephthalate) and chitosan were produced by electrospinning. Fiber morphology, diameter, pore size, and wettability were manipulated by varying the chemical composition of the electrospinning solution, i.e. chitosan concentration and molecular weight, and by post-electrospinning treatment with glutaraldehyde. In vitro studies were conducted using a fibroblast cell line toward a comprehensive understanding of how scaffolds characteristics can modulate the cell behavior, i.e. viability, adhesion, proliferation, extracellular matrix secretion, and three-dimensional colonization. Substantial differences were found as a result of scaffold morphological changes. Higher levels of adhesion, spreading, and superficial proliferation were achieved for scaffolds with smaller fiber and pore diameters while cell penetration and internal colonization were enhanced for scaffolds with larger pores. Additionally, the available area for cell adhesion, which is related to fiber and pore size, was a crucial factor for the viability of L929 cells. This paper provides significant insights for the development and optimization of electrospun scaffolds toward an improved biological performance.

Nanofibrous poly(3-hydroxybutyrate-co-3-hydroxyvalerate)/chitosan scaffolds for skin regeneration.

The purpose of this study was to evaluate hybrid poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV)/chitosan nanofibrous mats as scaffolds for skin engineering. In vitro studies were carried out to test the potential of the scaffolds for fibroblasts adhesion, viability, and proliferation (L929 cell line). The in vivo performance was also studied in a full-thickness wound healing model. PHBV/chitosan 4:1 (w/w) exhibited a higher in vitro biocompatibility and a better ability for cell adhesion and growth, compared to PHBV/chitosan 2:3 (w/w). The in vivo assay also revealed the better performance of this scaffold, improving the wound healing process in rats.

Quantitation of methylxanthinic alkaloids and phenolic compounds in mate (Ilex paraguariensis) and their effects on blood vessel formation in chick embryos.

Methylxanthinic alkaloids and phenolic compounds are related to the therapeutic properties of Ilex paraguariensis infusions. Considering the known vascular tropism of xanthines, an aqueous extract (mate) and caffeine were evaluated on blood vessel formation, in connection with the analysis of those secondary metabolites, which was performed in young and mature leaf samples collected in three cultivation systems located in the southern region in Brazil (Santa Catarina State). Samples of young and mature leaves from a monoculture cultivation system (MC) showed the highest content of phenolic compounds (149.68 microg/mL, young leaves; 135.50 microg/mL, mature leaves) and caffeine (young leaves, 148.07 microg/mL; mature leaves, 244.63 microg/mL) as compared to samples from agroforesty (AF) and shaded-native (NT) cultures. Theophylline was not detected in samples by reverse phase-high performance liquid chromatography, and mature leaves showed lower theobromine amounts (11.46 microg/mL). Treatments performed with mate aqueous extract and caffeine (1.03-4.12 microM/disk) in the yolk sac vascular membranes of 2-day-old chick embryos revealed pro-vasculo- and angiogenic properties as well as embryonic growth enhancement. These findings, uncoupled from any detectable embryotoxic effect, suggest a potential therapeutic and/or prophylactic use in cardiovascular disorders for caffeine and related constituents of mate plant extracts, an issue that waits further studies.