Figure 3.

Enhanced darkfield imaging of positively charged Au ENP / E. coli agglomeration. A) Representative images of 100 nm bPEI coated Au ENPs incubated with E. coli and monitored over time show immediate heteroagglomeration which led to increasingly large agglomerates across the 24 h period. bPEI Au ENPs appear bright yellow and E. coli appear faint white. A 10 μm scale bar is in the upper right comer. B) Representative image of control experiment, shown here with 30 nm PEG Au ENP incubated with E. coli displays no observable interaction or agglomeration of bacteria with neutral/negative charged particles at any time. Au ENPs appear faint green, E. coli appear bright white. A 10 μm scale bar is in the lower right. C) Plot showing small scale agglomeration for bacteria/Au ENP by measuring percentage of particles > 3 μm² in area for each time point and bPEI Au ENP size. Control experiment is 30 nm PEG Au ENP / E. coli sample. D) Plot of average agglomerate spatial area measured for each bacteria / bPEI Au ENP size combination and time point. Control comparison is 30 nm PEG Au ENP w/ E. coli. For both C) and D) the plotted error bars are ± 1 standard deviation, n = 3 images, and ANOVA with Tukey’s post hoc analyses for the 24 h data. Bars with the same letter are not significantly different from one another; Tukey’s multiple comparisons test, p ≤ 0.05.