Nanofibrous Polyaniline: an Antioxidative and Antimicrobial Polymer with Potential Tissue-engineering and Related Applications

Abstract

This study, for the first time, investigates antioxidant and antimicrobial properties of nanofibrous polyaniline (nfPANI) via a rapidly mixed reaction (RMR) method, polyaniline (PANI) colloids and dispersions, electrospun PANI fibres-scaffolds and PANI composites with potential medical devices applications. In Chapter 3, effects of high ammonium persulfate (HAPS) level and different dopant acids (hydrochloric acid, HCl; and camphorsulfonic acid, CSA) on the RMR method were studied and the morphologies were unaffected. HCl doped nfPANI was higher in yield, molecular weight, conductivity, free-radical scavenging (against 1,1-diphenyl-2-picrylhydrazyl, DPPH●) and antibacterial efficacy (against Staphylococcus aureus ATCC 6838 and Escherichia coli ATCC 25322). PANI emulsions and colloids were synthesised with different surfactants (sodium dodecyl sulfate, SDS; polysorbate 20, Tween20), and steric stabilisers (polyvinylpyrrolidone, PVP360 and PVP24, Mn = 360,000 and 24,000; polyethylene glycols, PEG400 and PEG200, Mn = 400 and 200) were investigated in Chapter 4. PANI-SDS emulsion showed high free-radical scavenging capacity and antibacterial efficacy. PVP-PANI colloids showed best stability, but reduced free-radical scavenging capacity and antibacterial efficacy due to steric stabilisation. In Chapter 5, electrospinning of PVP360 and PVP-nfPANI were discussed. UV-vis spectra confirmed nfPANI was undoped during electrospinning. PVP-nfPANI fibre-scaffolds retained 70% of free-radical scavenging capacity, but PVP-nfPANI fibre-scaffolds were highly sensitive to aqueous and polar solvents. Aqueous dispersions prepared from nfPANI, nfPANI in PVP360 solutions, electrospun PVPnfPANI fibre re-dispersions, and in-situ polymerised PANI-PVP were examined in Chapter 6. Steric stabilisation of PVP resulted in enhanced storage stability of PANI dispersions, and contributed to decreases in free-radical scavenging capacities and antibacterial efficacies. In Chapter 7, electrospun PCL containing nfPANI (PCL-nfPANI) were prepared and characterised. Nano-scaled electrospun fibres (c.a. 150 nm) were produced with high nfPANI loading (20% w/w). PCL-nfPANI fibre-scaffolds were electrically conductive, free-radical scavenging, antibacterial and non-cytotoxic. In Chapter 8, silicone rubber (SR) was dip-coated and in-situ polymerised with PANI, but both showed poor adhesions. In contrast, SR-PANI composites were prepared by direct blending of nfPANI and the curing was unaffected. The resultant composites were antibacterial, but with reduced free-radical scavenging capacity. The results from this study suggest potential antioxidant and antimicrobial applications in: spray-on, topical, tissue-culture, wound-dressing, packaging, and implants applications.