Effect of NP size on attachment density and growth rate

Next, we investigated the effect of particle size on the attachment density outcome in the ABS and BS NanoBEADS variants constructed using the optimal assembly parameters of E-800-60 and 165±11 nm or 121±6 nm particles. Representative scanning electron microscopy (SEM) images of both NanoBEADS variants are shown in Figure 5a-d. As shown in Figure 5e, NPs with a smaller diameter of 121±6 nm had significantly increased attachment density (p<0.0001) for ABS NanoBEADS, but the slightly increased attachment density for BS NanoBEADS was not statistically significant. Consistent with our observation of NanoBEADS constructed with large NPs, there was an average of 70% decrease in the NP areal density upon changing from the ABS linkage chemistry to the antibody-free BS linkage chemistry (Figure 5e). Our results suggest that irrespective of NP size, the linkage chemistry (i.e., the method used to present biotin on the bacteria outer membrane) significantly affects the NP attachment outcome. When the biotinylated antibody is used, more particles per bacteria are attached compared to using physisorbed biotin. The observed trends in the effect of NP size on the NP attachment density were conserved when the closely comparable B-800-60 assembly parameters were used (Figure S3a).