Colorimetric and Electrochemical Bacteria Detection Using Printed Paper- and Transparency-Based Analytic Devices

Area of Science:

• Analytical Chemistry
• Biosensing
• Environmental Science

Background:

• Food and waterborne bacterial contamination poses significant public health risks.
• Accurate and rapid detection methods are crucial for ensuring safety.
• Existing methods can be time-consuming or require specialized equipment.

Purpose of the Study:

• To develop complementary electrochemical and paper-based colorimetric platforms for detecting food and waterborne bacteria.
• To utilize enzyme-specific substrates for differentiating bacterial species.
• To establish sensitive and rapid detection limits for indicator organisms.

Main Methods:

• Developed transparency-based electrochemical detection using stencil-printed carbon electrodes (SPCEs).
• Created a paper-based colorimetric well plate system using a smartphone for detection.
• Employed enzyme substrates yielding p-nitrophenol (PNP), o-nitrophenol (ONP), or p-aminophenol (PAP).
• Tested detection limits and time-to-positive results using bacterial cultures and real-world samples.

Main Results:

• Electrochemical detection achieved low limits of detection (0.5–2.8 μM) for substrates.
• Colorimetric detection limits were higher (81–119 μM) but comparable in detection time.
• Detected low concentrations of Escherichia coli and Enterococcus species within 4–8 hours.
• Successfully identified bacterial contamination in inoculated alfalfa sprout samples.

Conclusions:

• Transparency-based electrochemical and paper-based colorimetric assays are effective complementary tools for bacterial detection.
• These methods offer rapid and sensitive detection of fecal contamination indicators in food and water.
• The developed platforms are cost-effective and suitable for single-assay applications.