Enhancing bacterial detection via laser-induced fluorescence: a comparison of methods and detection limits

Rapid bacterial detection is essential in clinical diagnostics, environmental monitoring, and food industry quality control, where sensitivity and speed are critical. This study evaluates four Laser-Induced Fluorescence (LIF) techniques, Conventional LIF, Reflection-Enhanced LIF (RELIF), Wavefront-Enhanced LIF (WELIF), and a combined approach (WERELIF), to improve sensitivity and lower detection limits for bacterial quantification. Using Pseudomonas aeruginosa as a model organism, fluorescence was excited at 405 nm, with a peak at approximately 500 nm. Calibration curves were constructed to determine the limit of detection (LOD) of each method and assess its performance in trace bacterial analysis. WERELIF demonstrated the highest fluorescence intensity and the lowest limit of detection (LOD) among the tested techniques, making it the most effective method for detecting low bacterial concentrations. RELIF exhibited significant signal enhancement due to reflective optimization. In contrast, WELIF provided moderate improvements, which were affected by sample inhomogeneity. The enhanced LIF techniques were superior to the conventional approach, particularly in terms of higher fluorescence intensity. This advantage is significant for applications such as early pathogen detection in clinical samples or monitoring bacterial contamination in water and food supplies. These findings provide a foundation for improving fluorescence-based bacterial quantification, with potential applications in point-of-care diagnostics, environmental surveillance, and industrial biosensing.