Figure 7
(a) A scattering-based μPAD assay for E. coli K12 via (b) immunoagglutination of polystyrene microparticles conjugated with anti-E. coli IgG. Through antibody-antigen binding, the presence of E. coli in a water sample leads to enhanced clustering of particle-E. coli complexes in the channel. (c) This change is optically detectable by smartphone imaging, and is correlated to E. coli K12 concentration by measuring the normalized change in Mie scattering intensity at 65° under ambient lighting conditions. (d) Dual-target and negative control solutions were assayed and compared with (e) single-target μPAD detection of E. coli K12 concentrations using anti-E. coli K12 IgG-conjugated microparticles as a scattering reagent (n = 4). (f) There was no significant difference in fractional quenching measured between the dual target control solutions and 0.5 × 103 CFU∙mL−1 E. coli K12, whereas each negative control solution demonstrated a significant difference in intensity compared with the E. coli K12 standard (p < 0.05).
