Bacterial nanocellulose-IKVAV hydrogel matrix modulates melanoma tumor cell adhesion and proliferation and induces vasculogenic mimicry in vitro.

Vasculogenic mimicry process has generated great interest over the past decade. So far, however, there have been only a few matrices available that allow us to study that process in vitro. Here, we have developed an innovative hydrogel platform with defined composition that mimics the structural architecture and biological functions of the extracellular matrix for vasculogenic mimicry of human melanoma cells (SK-MEL-28). We chemically immobilized IKVAV peptide on bacterial nanocellulose (BNC) fibers. BNC-IKVAV hydrogel was found to improve the adhesion and proliferation of SK-MEL-28 cells on the top and bottom surfaces. Particularly, the bottom surface of BNC-IKVAV induced SK-MEL-28 cells to organize themselves as well-established networks related to the vasculogenic mimicry process. Finally, our results showed that not only BNC-IKVAV but also BNC hydrogels can potentially be used as a three-dimensional platform that allows the screening of antitumor drugs. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 106B: 2741-2749, 2018.

Electroactive Gellan Gum/Polyaniline Spongy-Like Hydrogels.

The ability of electroactive materials to influence and modulate cell behavior has been revealing great potential, especially in the field of skeletal muscle tissue engineering. Herein, we propose PANi-GG electroactive spongy-like hydrogels as potential materials to modulate myoblast bioresponse. polyaniline (PANi) adds electroconductiviy to gellan gum (GG) spongy-like hydrogels that hold a high resemblance to the extracellular matrix (ECM), that is, water content, mechanical properties, and microarchitecture, and that can be further tuned to meet muscle tissue properties. For this purpose, PANi-GG spongy-like hydrogels were obtained by ionically cross-linking with calcium chloride (CaCl2) and further in situ aniline polymerization through oxidation with ammonium persulfate (APS) in a molar ratio of 1:1.05. The physicochemical characterization, surface morphology, electro-conductivity, and mechanical performance were assessed by FTIR, SEM, four-point probe technique, and compression testing, respectively. The viability and proliferation of L929 was not compromised after direct contact of PANi-GG spongy-like hydrogels with L929 cells, as determined by MTS assay and DNA quantification, respectively. C2C12 myoblasts were entrapped within the electroactive materials and cells adhered and spread. Moreover, cells proliferated along the cell culture period showing myosin expression after 7 days of culture. These results highlight that PANi-GG spongy like hydrogels are attractive candidates to be used in skeleton muscle tissue engineering.

Eumelanin Nanoparticle-Incorporated Polyvinyl Alcohol Nanofibrous Composite as an Electroconductive Scaffold for Skeletal Muscle Tissue Engineering.

Eumelanins are melanocyte-derived natural pigments with inherent electrical cues and outstanding physicochemical properties, which enhance the electroconductivity of the synthetic polymeric scaffold, upon incorporation as nanoparticles. Electrospun nanofibrous meshes generated from such composite polymers are of great interest for muscle tissue engineering applications. In this study, we investigated the feasibility of fabricating nanofibrous scaffolds of polyvinyl alcohol (PVA) incorporated with eumelanin nanoparticles (EUNp) by electrospinning and further assessed their impact on myogenic differentiation of skeletal myoblasts. Morphological and physicochemical analysis of EUNp-PVA nanofibrous mesh showed uniform, bead-free, thermally stable, and randomly oriented nanofibers (450 ± 10 nm) with effective retention of the incorporated EUNp, without any chemical cross-reactivity. Voltammetric measurements of EUNp-PVA mesh exhibits stable electrical conductivity (∼4.0 S cm-1), which was undetectable in plain PVA meshes. In vitrocytocompatibility studies showed a significant increase in viability, proliferation, and metabolic activity of the seeded C2C12 myoblast on EUNp-PVA mesh compared to controls. Interestingly, EUNp-PVA nanofibers supported reorganization of the C2C12 myoblast, with comparatively longer and wider myotube-like structures formed. Our results suggest that an EUNp-PVA composite nanofibrous scaffold with inherent electroconductive properties of incorporated EUNp and topographical cues of PVA nanofibers could be an excellent biomaterial scaffold for skeletal muscle tissue engineering applications.

Physicochemical and biological assessment of PEEK composites embedding natural amorphous silica fibers for biomedical applications.

The main aim of this study was to assess the physicochemical and biological properties of a novel poly(ether ether ketone) (PEEK) composite containing 30%wt natural amorphous silica fibers (NASF). PEEK and NASF powders were previously functionalized by atomization and citric acid in order to enhance adhesion between polymeric matrix and fillers. Then, composites were produced by cold compression molding technique at 350°C for 3h. Materials were characterized by chemical, microstructural, thermophysical, mechanical and cytotoxic analysis. The results of the mechanical assays showed that the incorporation fibers increased the elastic modulus of the resultant PEEK composite in 56% while its microhardness increased in 26.7%. Chemical and microscopic analyses detected a good interfacial adhesion between PEEK and NASF. The results of the cytotoxicity assays indicated that PEEK/NASF composites stimulated the metabolic activity of fibroblasts and therefore a high cytocompatibility was noticed. PEEK composites embedding natural amorphous silica fibers revealed a high potential to be used in medicine and dentistry replacing several polymeric and composite materials.

* Synthesis and Characterization of Electroactive Gellan Gum Spongy-Like Hydrogels for Skeletal Muscle Tissue Engineering Applications.

Advances on materials' research for tissue engineering (TE) applications have shown that animal cells respond directly to the material physical, chemical, mechanical, and electrical stimuli altering a variety of cell signaling cascades, which consequently result in phenotypic and genotypic alterations. Gellan gum (GG) spongy-like hydrogels (SLH) with open microstructure, mechanical properties, and cell performance have shown promising results for soft TE applications. Taking advantage of intrinsic properties of GG-SLH and polypyrrole (PPy) electroactivity, we developed electroactive PPy-GG-SLH envisaging their potential use for skeletal muscle TE. Three different methods of in situ chemical oxidative polymerization were developed based on the availability of pyrrole: freely dissolved in solution (method I and III) or immobilized into GG hydrogels (method II). PPy was homogeneously distributed within (method I and III) and on the surface (method II) of GG-SLH, as also confirmed by Fourier Transform infrared spectra. PPy-GG-SLH showed higher conductivity than GG-SLH (p < 0.05) whereas PPy-GG-SLH (method I and II) showed the best conductivity among the 3 methods (∼1 to 2 × 10-4 S/cm). The microarchitecture of PPy-GG-SLH (method I) was similar to GG-SLH but PPy-GG-SLH (method II and III) presented smaller pore sizes and lower porosity. PPy-GG-SLH (method I and II) compressive modulus (∼450-500 KPa) and recovering capacity (∼75-90%) was higher than GG-SLH, nevertheless the mechanical properties of PPy-GG-SLH (method III) were lower. The water uptake of PPy-GG-SLH was rapidly up to 2500% and were stable along 60 days of degradation being the maximum weight loss 20%. Mechanically stable and electroactive PPy-GG-SLH (method I and II) were analyzed regarding cellular performance. PPy-GG-SLH were not cytotoxic for L929 cells. In addition, L929 and C2C12 myoblast cells were able to adhere and spread within PPy-GG-SLH, showing improved spreading in comparison to GG-SLH performance. Overall, PPy-GG-SLH show promising features as an alternative electroactive platform to analyze the influence of electrical stimulation on skeletal muscle cells.

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.