Inner filter effect (IFE) as a simple and selective sensing platform for detection of tetracycline using milk-based nitrogen-doped carbon nanodots as fluorescence probe

A simple, selective, and sensitive turn-off fluorescent assay for detecting of tetracycline in pharmaceutical dosage form based on inner filter effect (IFE) sensing platform has been described. In this IFE sensing strategy, N-doped carbon dots (CDs) were prepared by one-pot solvothermal synthesis using milk as a precursor and were directly used as a fluorophore in IFE. The prepared CDs were characterized by common spectroscopic and microscopic techniques. The CDs exhibited excitation-wavelength dependent emission with 10% as the fluorescence quantum yield. The fluorescence of CDs was decreased in correlation to the addition of absorber (tetracycline), as the excitation spectrum of the fluorophore (CDs) matches the absorption spectrum of the absorber. The present IFE-based sensing platform showed a good linear relationship from 2.0 µM to 200 µM (R² = 0.9960) and provided a detection limit of 0.6 µM (signal-to-noise ratio of 3). Additionally, the cytotoxic effects of CDs were determined using normal healthy male Balb/C mice model treated with various doses of CDs and at the end of the study, no mortality or even no sign of toxicity was observed at oral doses of 100 and 200 mg/kg CDs in all treated animals. The proposed nanoprobe assay is a free from interferences, low-cost, biocompatible, and accurate for the detection of tetracycline in pharmaceutical formulation.