Rapid bacterial detection based on catalase activity using an optofluidic chip

Rapid and low-cost detection of bacteria in water is critical for ensuring drinking water safety and enabling effective public health surveillance. We introduce an optofluidic platform for quantifying bacteria by using catalase-mediated hydrogen peroxide consumption, eliminating the need for exogenous bio-recognition probes. Sample handling and optical readout are integrated in the optofluidic chip through a sequential process: the water sample is first mixed with hydrogen peroxide to trigger catalase-catalyzed reactions, then combined with a chromogenic substrate for detection. High-sensitivity absorbance measurement for the Fe 3 + –sulfosalicylic acid complex is enabled by an integrated optical waveguide. Using Escherichia coli ( E. coli ) as a model strain, the method exhibits a linear dynamic range of 5 × 10 1 –5 × 10 6 CFU/mL and a limit of detection of 4 CFU/mL. The platform was further validated using Staphylococcus aureus ( S. aureus ) and Bacillus subtilis ( B. subtilis ), confirming its broad applicability across catalase-positive bacterial species. Live/dead bacterial discrimination experiments demonstrated that the detection signal originates exclusively from metabolically active viable cells. Interference tests and analysis of real water samples verified the selectivity and accuracy of the method. Detection results are available within 10 min, enabling continuous operation with high sensitivity. This optofluidic approach provides a novel on-site technique for rapid bacterial detection and holds promising application prospects in online industrial and environmental monitoring.