Sensitivity Enhancement of a Micro Ring Resonator-Based Photonic Sensor by Using a Gelatin Methacryloyl Functional Coating for the Detection of Metoprolol

Aquatic environments are often contaminated with biopersistent pharmaceuticals, such as the β-blocker metoprolol. The quantitative determination of such pollutants is crucial for environmental monitoring. Therefore, a highly sensitive integrated photonic biosensor for the detection of minute concentrations of metoprolol is presented here. The sensor is based on a thermally robust ring resonator with a hydrogel coating for metoprolol adsorption. Hydrogels consisting of gelatin methacryloyl enabled an increase in the concentration of metoprolol ions in the vicinity of the photonic chip, resulting in high sensitivity of the sensor setup. Compared to an uncoated chip, an increase in sensitivity of up to a factor of 20 was observed. In combination with software-implemented signal processing, the setup showed a detection limit of less than 1 × 10^–4μmol mL^–1. The combination of functional coating, thermally insensitive design, and applied digital signal postprocessing makes the system introduced here an attractive approach toward sensor-based wastewater analysis and monitoring.