Adoption of particle-based biosensing as a cost-disruptive tool for screening highly dilute sample streams for bacterial contamination

Target amplification and concentration have been barriers to the realization of LMIC-affordable diagnostic platforms and methods for handling dilute sample streams such as urine or water. The need to amplify targets via nucleic acid amplification, cell culture, and centrifugation increase the complexity and cost of the sample screening process, thereby impacting LMIC adoption and testing rigor. In this proof-of-concept study, we demonstrate the feasibility of detecting 100 Escherichia coli CFU/ mL of water without the need for target amplification. This is enabled by Molecular weightstones (MWS) - a class of non-traditional, particle-based biosensors which signal the presence of bacteria via particle-biomarker aggregation and sedimentation. We demonstrated detection and quantification of E. coli in water in the range of 100 - [Formula: see text] CFU/ mL using [Formula: see text] MWS particles within 10 minutes and a lower concentration (10 CFU/ mL) in 5 hours. At a cost profile of USD 1 per test(unscaled), MWS can be used as an instrument-free qualitative method for signaling bacterial presence in dilute samples through visually discernible results. It can also be adapted for quantifying bacterial load in dilute samples via computer vision using a companion device.