Production and evaluation of electrospun polyaniline/biopolymer composite nanofibres for medical applications

The aim of this study is the production of a nanofibrous electroactive mat and the investigation of its potential use in tissue engineering, and more specifically for wound dressing purposes. The limitations regarding electrospinnability of the conducting polymer will be identified and addressed and the factors related to its biological properties will be evaluated. To this end, conducting polymer, polyaniline (PANI) was chosen as the electroactive component and blend electrospinning was identified as the most suitable method to produce continuous nanofibres containing PANI. Various biocompatible polymers and solvent systems were investigated for their suitability to assist in electrospinning and PEO (polyethylene oxide) and CH (chitosan) were chosen as carrier polymers for blend electrospinning of PANI. Consequently, CSA (Camphor-10-sulfonic acid (β)) doped PANI/PEO and CSA doped PANI/CH conducting nanofibrous mats were produced by electrospinning. The electrospinning windows for both blends were determined by using full factorial experimental designs. The combined effects of the humidity, voltage and flow rate on the fibre morphology and diameter were examined for both blends, demonstrating that the ambient humidity is the critical factor affecting the electrospinning process and determining the electrospinning window for a conducting polymer. Low humidity favors the formation of defect free fibres while high humidity either hinders fibre formation or causes the formation of defects on the fibres. In the case of PANI/PEO blends, different levels of PANI doping were investigated, and high level of doping with CSA was found to lead to the formation of crystalline structures. Data fitting was used to explore the behavior of conducting polymers using the case of PANI/PEO electrospinning and very good agreement between experimental and theoretical predictions was obtained for only a limited range of experimental conditions, whereas deviation was observed for all other sets of conditions. In the case of PANI/CH, the effect of different ratios of conducting polymer in the blend (0:1, 1:3, 3:5 and 1:1) was examined, as for the electrospinnability, resulting 3 nanofibrous morphology, mat contact angle, electrical conductivity, antibacterial activity and cellular biocompatibility. The incorporation of PANI in the electrospinning blend, affected the electrospinnability of the solution, making it more susceptible to RH deviations, and contributed to the decrease of nanofibre diameter. Higher PANI content was found to result in more hydrophobic and more conducting mats. The method that was used to stabilize the PANI/CH mats was also found to affect antibacterial activity and conductivity. The produced blend mats, exhibited antibacterial activity which was higher against Gram positive B. subtilis and lower against gram negative E. coli. The cellular biocompatibility was assessed with human osteoblasts and fibroblasts, in terms of cell proliferation rate as well as cell attachment and morphology. Cells of both cell lines adhered well and showed good growth rates on nanofibrous substrates of all blend ratios when compared to standard tissue culture plastic. Finally, amongst the PANI containing mats, the one of 1:3 PANI:CH ratio, was identified as the best to support osteoblast and fibroblast cell proliferation when compared to the pure chitosan.