Antimicrobial activities of nanostructured polyanilines doped with aromatic nitro compounds

Abstract

Polyaniline (PANI) doped with nitro compounds such as 2,4,6-trinitrophenol i.e., picric acid, 3,5-dinitrobenzoic acid and hydrochloric acid in the emeraldine salt form was synthesized by chemical oxidative polymerization. Polyaniline emeraldine base (PANIEB) was prepared by dedoping polyaniline chloride (PANICl). The as-synthesized PANIs were characterized by Fourier transform infrared (FT-IR), powder X-ray diffraction (XRD), scanning electron microscopy (SEM) and UV–Visible spectra. The size of PANI particles varied from 2 to 70 nm, and the average particle size was around 40 nm. The crystallinity of PANI improved when doped with nitro compounds. The in vitro antimicrobial properties of the PANI against various gram negative, gram positive bacteria and fungus Candida albicans were evaluated using agar well diffusion method. The antibacterial effects were assessed from the diameter of zone of inhibition and minimum inhibitory concentration values. The test results indicated that doped PANIs had enhanced antimicrobial efficacy compared to PANIEB. The mechanism of antimicrobial effects of PANI was also proposed. PANI-3,5-dinitrobenzoate (PANIDN) was found to exhibit two times lower antibacterial activity compared to 3,5-dinitrobenzoic acid, thereby indicating the suitability of doped PANI for slow drug release when used as tissue implants. Keywords: Aromatic nitro compounds, Doped polyanilines, Emeraldine base, Antimicrobial properties