Colorimetric immunodetection of bacteria enriched on membranes within a compact multichannel filtration device

Abstract Colorimetric immunoassay is a widely used method for pathogen detection. The conventional implementation of immunoassays in 96-well plates often encounters difficulties for samples with low concentrations. In this study, the detection performance has been improved using a cellulose acetate membrane for target enrichment and immunodetection. For this end, a compact multichannel filtration device was fabricated using a 3D printer for sample loading. Background effects of the membrane were greatly minimized after pretreatment with a sodium hydroxide solution to significantly reduce non-specific binding. The colorimetric result of the immunodetection of Escherichia coli strain K12 (E.coli K12) was recorded and quantitatively analyzed with a smartphone camera. A limit of detection was calculated as 40 cfu (colony forming unit)/ml, two orders of magnitude more sensitive than that obtained on 96-well plates with standard protocol. The developed approach features an integrated sample enrichment scheme, reduced reagents consumption, multiple channels for parallel processing and no reliance on advanced laboratory instruments, thereby providing potential for a low-cost and easy-to-use immunodetection system.