Visual colorimetric testing strips for rapid microbe detection in aqueous solutions

Overview

This solution offers a rapid, low-cost visual method for detecting microbes in aqueous solutions using specially formulated testing strips. The approach leverages the fact that microbial metabolites diffuse throughout water and can react with chemicals coated on a white substrate to produce visible color changes. Because the human eye is highly sensitive to color variation, detection can be performed on-site without specialized instruments. Initial validation has demonstrated the ability to detect E. coli at concentrations as low as 50 CFU/mL in glucose-free dialysis solutions, at a cost of approximately $0.30 per test. The technology is intended for applications in healthcare, environmental monitoring, and water quality assessment, where fast and accessible microbial screening is critical.

Technical specifications

Detection principle:

• Microbial metabolites present in aqueous solution react with chromogenic chemicals immobilized on a white testing strip substrate
• Reactions produce visible color changes detectable by the naked eye
• Multiple chromogenic reactions can be combined with multivariate analysis to identify specific microbial species

Current test methods:

• Drop method: A small volume of aqueous sample is applied directly to a pre-treated strip and incubated for approximately 10 minutes before color observation
• Dip method: The strip is dipped into the aqueous sample (approximately 100 microliters) for approximately 10 minutes before color observation

Key features:

• Strip format is similar to lateral flow assay strips (such as pregnancy tests)
• No instrumentation required for readout
• Low per-test cost (approximately $0.30)
• Compatible with small sample volumes

Technology readiness level

The technology is at an early stage of development. Proof-of-concept validation has been completed using E. coli in glucose-free dialysis solution, achieving detection at 50 CFU/mL by visual inspection. A patent has been submitted to the Kent State University patent committee, and specific chemical formulations are being withheld for proprietary reasons. Future validation plans include expanding testing to additional bacterial species, pushing the detection limit below 0.1 CFU/mL through assay optimization, developing a quantitative color reference card, and integrating multivariate analysis for species identification. The technology is complementary to light-scattering based microbial counting methods and is positioned for further co-development and licensing partnerships.