Antibiofilm activity of nano sized CuO

Antibiofilm properties of bulk and nano-sized copper oxide (CuO) were investigated using four species of bacteria viz: Staphylococcus aureus, E. coli, Pseudomonas aeuriginosa (PAO1) and Pseudomonas putida. The effect of both commercial and synthesized nanoparticles on biofilm formation was investigated using different concentrations 0.02, 0.12, 0.24, 0.5, 1.0, 1.2, 1.4 & 1.8 µg / mL). Both bulk (91% reduction) and nano-sized (93% reduction) particles significantly reduced biofilm formation in all the four species of bacteria. Concentration and size/shape of nanoparticles seemed to influence biofilm inhibition. Increase in NP concentration from 0.02 to 1.8 µg/mL resulted in a marginal increase in inhibition. While a similar increase in concentration of bulk particles, resulted in 18% decrease in biofilm inhibition. Differences in biofilm inhibition between bulk and nano-sized particles were marginal at low concentrations (0.02, 0.12 & 0.24 µg/mL), whereas prominent differences were observed from concentration of 0.5 µg/mL onwards for the bulk particles. The decrease in inhibition efficiency of bulk nanoparticles with increase in concentration may be attributed to the differences in size, shape, aggregation and settling behaviour. In general, higher efficiency was observed with S. aureus, E. coli and P. putida biofilms, whereas P. aeuriginosa cells showed more resistance in the presence of CuO nanoparticles. Results of the present study indicated that size and shape of the nanoparticles, seem to have an influence on the effective concentration, required for inhibition of biofilms.