It was demonstrated that conducting polymers can be used in development of bioactive matrices for tissue engineering. The most promising conducting polymer for biomedical applications is polypyrrole. Due to a number of useful properties, polypyrrole can be used in designing “smart” biologically active materials. In order to improve mechanical properties of the composite matrices, aliphatic copolyamide was used. Thin polymeric films were obtained from solution of this copolyamide; the solution was also used in preparation of non-woven fibrous mats by electrospinning. Copolyamide films were modified with pyrrole in the process of its oxidative polymerization to give the desired composite matrices. The obtained samples demonstrated suitable performance characteristics and a sufficient conductivity level for cell technologies. In vitro experiments showed that the matrices based on copolyamide and polypyrrole provide good survivability, adhesion and proliferation of human dermal fibroblasts.

The conducting film material intended for research in the field of cell technology is obtained on the basis of two biocompatible polymers—aliphatic copolyamide and polypyrrole. The material consists of hybrid nanofibers having the core–shell structure. The film is formed by copolyamide microfibers that are obtained by electrospinning and coated with a polypyrrole nanolayer. Studies show that the material is stable and does not change its characteristics when stored both in air and in aqueous media. The hybrid fiber film has a high porosity, good water wettability, and a sufficient level of stress–strain characteristics. The resistance of the material is 300–600 Ω/sq, which allows its use for the electrical stimulation of proliferative activity of cells.

The quantitative difference in the antibacterial response was measured for pine rosin and propolis against Staphylococcus aureus ATCC 12598. The activity was studied for fibrous networks that form entirely bio-based cellulose-acetate (CA) materials. The analysis considers the effects of bacterial input, additive dosage, solvent type, variation in preparation, as well as the effect of storage time. Based on the results, the electrospun network structure is dependent on the solvent and the concentration of rosin and propolis. Both rosin and propolis improved the cellulose acetate solution processability, yet they formed beads at high concentrations. Rosin and propolis created strong antibacterial properties when these material systems were immersed in the liquid for 24 h at room temperature. The response remained visible for a minimum of two months. The electrospun networks of water and DMAc solvent systems with 1 to 5 wt% rosin content were clearly more efficient (i.e., decrease of 4 to 6 logs in colony forming units per mL) than the propolis networks, even after two months. This efficiency is likely due to the high content of abietic acids present in the rosin, which is based on the Fourier transform infrared spectra. The results of the additional analysis and cell cultivation with dermal fibroblast cells indicated an impairing effect on skin tissue by the rosin at a 1 wt% concentration compared to the pure CA fibers.

We have demonstrated the possibility of application of electroconducting polymers for fabricating bioactive matrices for tissue engineering. Polypyrrole is most promising among such polymers in the context of its biomedical applications. Polypyrrole possesses a number of properties that make it an adequate basis for preparing "smart" bioactive materials. To obtain the best mechanical properties of composite matrices, we used aliphatic copolyamide. The matrices obtained from the copolyamide solution had the structure of thin films, as well as fibrous nonwoven mats prepared by electroformation. Copolyamide films were modified with polypyrrole using polymerization by oxidation with the formation of composite matrices. The samples obtained in this way exhibited service properties acceptable for applications and an electric conductivity level sufficient for cell technologies. In the in vitro experiments, the copolyamide- and polypyrrole-based matrices support the viability, adhesion, and proliferation of human dermal fibroblasts.

Most recycling methods remove the essential sizing from reinforcing fibres, and many studies indicate the importance of applying sizing on recycled fibres, a process we will denote here as resizing. Recycled fibres are not continuous, which dissociates their sizing and composite lay-up processes from virgin fibres. In this study, commercial polypropylene and polyurethane-based sizing formulations with an aminosilane coupling agent were used to resize recycled glass and carbon fibres. The impact of sizing concentration and batch process variables on the tensile properties of fibre-reinforced polypropylene and polyamide composites were investigated. Resized fibres were characterized with thermal analysis, infrared spectroscopy and electron microscopy, and the tensile properties of the composites were analysed to confirm the achievable level of performance. For glass fibres, an optimal mass fraction of sizing on the fibres was found, as an excess amount of film former has a plasticising effect. For recycled carbon fibres, the sizing had little effect on the mechanical properties but led to significant improvement of handling and post-processing properties. A comparison between experimental results and theoretical prediction using the Halpin-Tsai model showed up to 81% reinforcing efficiency for glass fibres and up to 74% for carbon fibres.

The investigation of the dependence of effective viscosity on shear rate for a water-alcohol solution of an aliphatic copolyamide and its mixtures with single-wall carbon nanotubes reveals that additives of the nanoparticles in the amount of 0.5 wt % lead to a substantial reduction in the effective viscosity as the shear rate rises. The measurement of the surface tension and electrical conductivity of the solutions bearing 0.1–2.0 wt % of the nanotubes allows one to choose an optimal mode for electrospinning of the composite nanofibers based on the aliphatic copolyamide. The introduction of carbon nanofibers reduces the specific resistance of the material to 8.9 × 109 Ω m, but increases the elastic modulus. The lack of cytotoxicity of the resulting materials and the high proliferative activity of human dermal fibroblasts on their surface allow one to use the film materials based on the composite nanofibers in cell technologies and as matrices for tissue engineering.

Методом электроформования растворов полиамидокислоты на основе диангидрида 3,3 ,4,4 -дифенил тетракарбоновой кислоты и о-толидина в смеси растворителей N,N-диметилацетамид-бензол получены нановолокна диаметром от 100 до 300 нм. Термическая обработка нановолокнистого материала из полиамидокислоты приводит к образованию нановолокон ароматического полиимида диаметром от 100 до 200 нм. Температура начала терморазложения полиимидных нановолокон в атмосфере аргона составляет 537 °С. Методом сканирующей электронной микроскопии показано, что материал на основе нановолокон из ароматического полиимида сохраняет эластические свойства вплоть до температуры жидкого азота. Полученный материал характеризуется отсутствием цитотоксичности - фибробласты человека, культивируемые на нем, обладают высокой пролиферативной активностью.

Nanofibers with a diameter of 100–300 nm are obtained by electroformation of solutions of polyamide acid based on 3,3′,4,4′-biphenyltetracarboxylic acid dianhydride and o-toluidine in an N,N-dimethylacetamide/ benzene solvent mixture. Thermal treatment of nanofibrous polyamide acid material leads to the formation of nanofibers of aromatic polyimide with a diameter of 100–200 nm. The temperature of the beginning of thermal decomposition of polyimide nanofibers in an argon atmosphere is 537°C. SEM images show that the material based on aromatic polyimide nanofibers preserves its elastic properties even at the temperature of liquid nitrogen. The obtained material is characterized by the absence of cytotoxicity: human fibroblasts cultivated on it are characterized by high proliferative activity.

Conducting materials based on polypyrrole-modified nanofibers of polylactides of different molecular masses and copolymers of ε-caprolactam (–NH–(CH2)5–CO–) and hexamethylenediamine adipate (–H(CH2)6NHCO(CH2)4CO–) were prepared. As shown by scanning electron microscopy, oxidative polymerization of pyrrole on the polymer nanofiber matrix depends on the nanofib er hydrophilicity. The heterophase synthesis of polypyrrole on the surface of hydrophilic nanofibers of the aliphatic copolyamide allowed uniform coating of the material surface with polypyrrole nanoparticles. The surface resistivity of the composite material was about 0.4 kΩ sq–1.