Smartphone detection of Escherichia coli from wastewater utilizing paper microfluidics

Smartphone detection of E. coli from wastewater was successfully demonstrated using paper microfluidics. Three channels of each paper chip were pre-loaded with BSA-conjugated and anti-is. coft-conjugated beads with varying amount, for negative control, low- and high-range E. coli detection, respectively. Dipping a paper chip into wastewater (or pipetting) led E. coli antigens to travel through paper fibers while effectively filtering out contaminants. E. coli antigens caused immunoagglutination of antibody-conjugated beads (but not BSA-conjugated beads) that were still confined within the paper fibers. This immunoagglutination was quantified by evaluating Mie scattering from the digital images taken at an optimized angle and distance with a smartphone. The detection limit was single-cell-level and the total assay time was less than one minute.