A fluorescent sensor based on nitrogen-doped graphene quantum dots and molecularly imprinted polymers for selective...

Meropenem, a broad-spectrum carbapenem antibiotic, is widely used in the treatment of severe bacterial infections. However, the accurate determination of meropenem in complex biological and environmental matrices remains a significant analytical challenge. In this study, we report the development of a highly sensitive and selective fluorescence sensor for the determination of meropenem using nitrogen-doped graphene quantum dots capped with a surface molecular imprinting polymer (N-GQDs@MIP). Characterization and optical properties of the N-GQDs@MIP nanocomposite were thoroughly investigated using various analytical techniques. Upon excitation at 365 nm, the sensor exhibited strong fluorescence emission at 450 nm which quenched upon meropenem binding. Mechanistic studies revealed a static quenching process driven by strong host-guest interactions between meropenem and the imprinted polymer recognition sites, as confirmed by Stern-Volmer analysis and thermodynamic calculations. Density functional theory calculations also revealed specific molecular interactions between meropenem and the N-GQDs@MIP. Central composite design optimization was employed to systematically investigate the effect of key experimental parameters, such as pH, reaction time, and N-GQDs@MIP concentration, on the sensor's performance. A significant quadratic regression model was obtained, with a high coefficient of determination (R² = 0.956) and excellent predictive capability that was further employed to maximize the sensor's sensitivity. Validation of the analytical method demonstrated a wide linear range of 25-1500 ng/mL, a low limit of detection of 7.42 ng/mL, and excellent selectivity against structurally similar antibiotics as well as good stability and reusability. The developed N-GQDs@MIP sensor was successfully applied to the determination of meropenem in pharmaceutical formulations, spiked human serum, urine, and environmental water samples with satisfactory recoveries and precision. Hence, this facile and robust fluorescence sensor offers a promising analytical platform for the sensitive, selective, and reliable quantification of meropenem in various clinical and environmental applications posing the current approach as a valuable alternative to existing analytical methods.