Prospect of electroactive poly(2-aminobenzoic acid) and poly(2-aminobenzoic acid)-nanocomposite-Fe2O3 as antibacterial agents and antioxidants

The extraordinary features of the substituted polyanilines such as the electrical conductivity, redox behaviour, good environmental stability and excellent biocompatibility make them suitable for incorporation into the living systems. The present work aims at synthesizing poly(2-aminobenzoic acid) (PABA) and poly(2-aminobenzoic acid)-nanocomposite-Fe2O3 (PABA/Fe2O3) by emulsion polymerization using ammonium persulphate (APS) as the oxidant, hydrochloric acid (HCl) as the dopant and camphor sulphonic acid (CSA) as the surfactant. The structural, thermal and morphological characteristics of PABA and PABA/Fe2O3 were ascertained from UV-Visible spectroscopy, FT-IR spectroscopy, TGA/DTA and SEM-EDX. The materials were found to be semi-conducting with a conductivity of 1.5 x 10(-3) S cm(-1) for PABA and 1.4 x 10(-3) S cm(-1) for PABA/Fe2O3. The oxidation peak potentials were observed at 0.28 V and 0.5 V for PABA and at 0.27 V and 0.46 V for PABA/Fe2O3 corresponding to the change of emeraldine base to emeraldine salt to fully oxidized pernigraniline form. The reduction peaks were displayed at 0.4 V and 0.14 V for PABA and at 0.39 V and 0.12 V for PABA/Fe2O3 corresponding to the transition of fully oxidized pernigraniline to emeraldine salt to emeraldine base. The electrostatic binding between the positively charged -NH groups of PABA and the negatively charged bacterial cell wall of Enterococcus faecalis and Escherichia coli and the continuous release of Fe3+ ions of PABA/Fe2O3 enhanced the antibacterial activity. 50 mu g/ml of PABA and PABA/Fe2O3 was the minimum inhibitory and minimum bactericidal concentration required to inhibit the growth of Enterococcus faecalis. 20 mu L concentration of PABA/Fe2O3 was capable of inhibiting 89.85% DPPH free radicals owing to the synergic interaction of PABA and nano Fe2O3.