Method for in situ polypyrrole coating, and the example of its use for functionalization of polyurethane anisotropic electrospun mats.

The in situ coating of polymer substrate with polypyrrole, described herein with detailed know-how, represents a novel technique of surface functionalization. The choice of oxidizing agent and the polymerization time both affect the properties of the thin polypyrrole layer. The specific conductivity, free surface energy, thickness, topography, and FTIR spectra of polypyrrole layer were determined. The conductive coatings were further used to functionalize both isotropic and anisotropic electrospun polyurethane nanofibrous mats to show their applicability and study the bioactive effect of both the anisotropy and conductivity together. The morphology of composites was studied by means of atomic force microscopy and scanning electron microscopy. A complex cytocompatibility study was performed, including determining cytotoxicity by optical and fluorescence microscopy, the advanced qualification of cell morphology by cell-image analysis, and a study of stem cell behavior. The results clearly showed the significant impact of substrate modification on cells, especially on fibroblasts while the embryonic stem cells were less affected. This study shows not only the effective way to prepare a thin conducting layer based on polypyrrole but also demonstrates its importance for the fabrication of smart biomaterials.

Formulation of Magneto-Responsive Hydrogels from Dually Cross-Linked Polysaccharides: Synthesis, Tuning and Evaluation of Rheological Properties.

Smart hydrogels based on natural polymers present an opportunity to fabricate responsive scaffolds that provide an immediate and reversible reaction to a given stimulus. Modulation of mechanical characteristics is especially interesting in myocyte cultivation, and can be achieved by magnetically controlled stiffening. Here, hyaluronan hydrogels with carbonyl iron particles as a magnetic filler are prepared in a low-toxicity process. Desired mechanical behaviour is achieved using a combination of two cross-linking routes-dynamic Schiff base linkages and ionic cross-linking. We found that gelation time is greatly affected by polymer chain conformation. This factor can surpass the influence of the number of reactive sites, shortening gelation from 5 h to 20 min. Ionic cross-linking efficiency increased with the number of carboxyl groups and led to the storage modulus reaching 103 Pa compared to 101 Pa-102 Pa for gels cross-linked with only Schiff bases. Furthermore, the ability of magnetic particles to induce significant stiffening of the hydrogel through the magnetorheological effect is confirmed, as a 103-times higher storage modulus is achieved in an external magnetic field of 842 kA·m-1. Finally, cytotoxicity testing confirms the ability to produce hydrogels that provide over 75% relative cell viability. Therefore, dual cross-linked hyaluronan-based magneto-responsive hydrogels present a potential material for on-demand mechanically tunable scaffolds usable in myocyte cultivation.