Quantification of a latex agglutination assay for bacterial pathogen detection in a low-cost capillary-driven fluidic platform

Bacterial contamination of water, for example by Escherichia coli, is a major cause of preventable diseases in rural developing communities. With the lack of infrastructure and experienced laboratory professionals, careful water sampling and analysis becomes inaccessible in these resource-limited environments. There is a need for a low-cost and equipment-free detection platform for detecting pathogens within fluid samples. Latex agglutination assays have been widely used in biology and medicine for its simplicity and specificity. However, conventional agglutination tests have their shortcomings, including the subjectivity in determining the degree of agglutination and the non-quantitative output. We propose a miniaturized device capable of quantifying the E. coli contamination levels in fluid samples. The detection employs the latex agglutination test, where functionalized latex particles form agglutinates with specific antigens in the fluid sample. Channels fabricated using adhesive tapes coated with hydrophilic materials are used to drive the fluid sample through a detection zone, where an image analysis algorithm quantifies the degree of agglutination using images obtained by a smartphone. The use of capillary-driven flows eliminates the needs for an external active pumping system and other equipment typically necessary for interfacing fluidic chips. This aspect of our device could resolve the issues with lack of trained personnel, which is a major and severe constraint in deploying health technology in these regions.