Incorporation of crystal violet, methylene blue and safranin O into a copolymer emulsion; the development of a novel antimicrobial paint

Crystal violet, methylene blue, safranin O and 2 nm gold nanoparticles were incorporated into a copolymer emulsion paint and three separate paint systems were prepared; a three-dye system (crystal violet, methylene blue, safranin O and 2 nm gold nanoparticles), a two-dye system (crystal violet, methylene blue and 2 nm gold nanoparticles) and a one dye system (safranin O and 2 nm gold nanoparticles). The modified polymers were characterised by UV-Vis absorbance spectroscopy, IR spectroscopy and X-ray photoelectron spectroscopy. The three paint systems were moderately stable under aqueous conditions, with a limited amount of leaching of the dyes from the paint polymer into the surrounding aqueous solution. Exposure of the three paint systems to a 28 W white light source induced the lethal photosensitisation of both Staphylococcus aureus and Escherichia coli. Moreover, both the three-dye and two-dye systems resulted in a 4 log kill against S. aureus under dark conditions, and a 1.5 log dark kill was obtained by the safranin O and 2 nm gold nanoparticle system.