A fluorescent sensor based on a silicon quantum dots/chitosan nanocomposite for tetracycline monitoring in serum samples

An optical nano-probe based on silicon quantum dots (SiQDs) was developed for the trace determination of tetracycline (TC) in biological samples. SiQDs were synthesized using 3-aminopropyl triethoxysilane as a silicon source and ascorbic acid as a reductant at 60 °C. The as-prepared water-soluble SiQDs were then modified with chitosan (CS) nanoparticles to produce a strong fluorescence emission at 435 nm. The fluorescence emission of the modified SiQDs (SiQDs/CS nanocomposite) was significantly quenched upon the addition of TC through an inner filter mechanism, realizing a novel "on-off" fluorescent probe. Numerous factors affecting the analytical signal were inspected and optimized. Under optimal conditions, the developed chemo-sensor was used to determine tetracycline in a concentration range of 0.7-1000.0 µg L^-1, with a detection limit of 0.2 µg L^-1. The developed nano-probe was used for TC monitoring in human serum samples with relative recovery values in the range of 96.0-104.9% for the spiked samples. The fabricated nano-probe shows numerous advantages, such as simplicity, selectivity, and rapid response, introducing a novel analytical method for TC sensing in aqueous media. Additionally, the water solubility, high stability, and low toxicity of the SiQDs/CS nanocomposite expand its applicability as a fluorescent nano-probe in biological matrices.