Influence of nano-CuO and -TiO2 on deposition and detachment of Escherichia coli in two model systems

Growing evidence suggests that agricultural water quality is closely tied to food safety risks. Therefore, the presence of nanoparticles in environmental waters due to utilization as pesticides and fertilizers may have unintended consequences, as the effects of their interactions with foodborne bacteria are not well understood. This investigation utilizes a 2D parallel-plate flow cell and a 3D saturated sand column to systematically examine changes in bacterial transport trends due to nano-bio interactions under dynamic flow conditions. Two Escherichia coli species, O157:H7 and 25922, exposed to nano-CuO (<50 nm) and nano-TiO2 (<150 nm), were used to mimic agriculturally relevant conditions. In flow cell experiments, the presence of nano-CuO increased deposition and minimized release of pathogenic E. coli O157:H7 on a model spinach surface, while nano-TiO2 had no significant effects (p > 0.05). Attachment and detachment - as quantified by mass transfer rate coefficients - of E. coli 25922 from the leaf surface were not impacted by the presence of nanoparticles. No breakthrough was observed in the column experiments, with the exception of nano-TiO2 eluted in the presence of E. coli O157:H7. However, column dissection revealed higher proportions of suspended particles retained in the upper portion of the column when either nanoparticle was present. This provides further evidence that nanoparticles affect bacterial deposition and release, potentially promoting biofilm formation and foodborne illness risks.