Fluorometric Detection of Salmonella in Water Using a Cell Imprinted Polymer Thin Film-based Microfluidic Sensor

Most imprinted polymer-based bacterial sensors rely on microparticles as recognition elements, which pose challenges in handling, integration, and consistency in real-world applications. This study introduces a novel fluorometric microfluidic biosensor using cell-imprinted polymer (CIP) thin films for Salmonella detection in water. The CIP was fabricated by mixing Salmonella cells into a pre-polymer solution containing four functional monomers. Non-imprinted polymer (NIP) solution was prepared by eliminating the template bacteria. The CIP and NIP pre-polymers were injected into a pair of laser-cut parallel microchannels, UV‑cured, and washed to form complementary bacterial binding cavities in CIP. A second pair of microchannels with fluid inlets and outlets were bonded orthogonally to the CIP/NIP microchannels, allowing for fluid handling and bacterial exposure (10 ¹ -10 ⁸ CFU/mL) within the sensor. Exposure to FITC dye post bacteria capture and fluorescence quantification showed an increase in signal intensity proportional to Salmonella concentration. The sensor exhibited a detection limit of 1.47×10 ³ CFU/mL and a linear dynamic range from 10 ³ to 10 ⁷ CFU/mL. Specificity assays showed that CIP differentiated target bacteria from non-target species at 10 ⁷ CFU/mL, but with moderate selectivity. Competitive binding experiments further confirmed the sensor’s capability to differentiate Salmonella from E. coli and Sarcina at 10 ⁷ CFU/mL. Future optimization of polymer composition and microfluidic design is required to enhance sensitivity and selectivity. Overall, this work shows that combining CIPs with a simple microfluidic fluorescence setup is an effective way to build low-cost, portable sensors for real-time whole-cell bacterial detection.