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.

Chitosan/dialdehyde cellulose hydrogels with covalently anchored polypyrrole: Novel conductive, antibacterial, antioxidant, immunomodulatory, and anti-inflammatory materials.

In this work, conductive composite hydrogels with covalently attached polypyrrole (PPy) nanoparticles are prepared. Hydrogels are based on partially re-acetylated chitosan soluble at physiological pH without any artificial structural modifications or need for an acidic environment, which simplifies synthesis and purification. Low-toxic and sustainable dialdehyde cellulose (DAC) was used for crosslinking chitosan and covalent anchoring of PPy colloidal particles. The condensation reaction between DAC and PPy is reported for the first time and improves not only the anchoring of PPy particles but also control over the properties of the final composite. The soluble chitosan and PPy particles are shown to act in synergy, which improves the biological properties of the materials. Prepared composite hydrogels are non-cytotoxic, non-irritating, antibacterial, can capture reactive oxygen species often related to excessive inflammation, have conductivity similar to human tissues, enhance in vitro cell growth (migration assay), and have immunomodulatory effects related to the stimulation of neutrophils and macrophages. The covalent attachment of PPy also strengthens the hydrogel network. The aldol condensation as a method for PPy covalent anchoring thus presents an interesting possibility for the development of advanced biomaterials in the future.