Fluorometric determination of doxycycline based on the use of carbon quantum dots incorporated into a molecularly...

A fluorometric assay is described for doxycycline detection. It is based on the use of nitrogen-doped carbon quantum dots (NCQDs) coated with molecularly imprinted polymers (MIPs). The NCQDs were prepared by a one-step hydrothermal reaction using citric acid and ethylenediamine (EDA) as the starting materials. Afterwards, the NCQDs were incorporated into the polymer that was molecularly imprinted with doxycycline. It is found that doxycycline quenches the fluorescence of the NCQDs, and that the functional groups on the surface of NCQDs play an important role in terms of quenching efficiency. A larger fraction of carboxyl groups presented on the surface of NCQDs leads to a higher quenching efficiency due to the enhanced electron transfer from NCQD to doxycycline. The NCQDs@MIP composite can specifically and rapidly recognize doxycycline. Fluorescence drops linearly in the 5 to 50 μM doxycycline concentration range, and the limit of detection is 87 nM. This method was successfully applied to the determination of doxycycline in spiked pig serum where it gave recovery rates of >94%. Graphical abstract Schematic illustration for fabricating a fluorescent sensor based on nitrogen-doped carbon quantum dots (NCQDs) and molecularly imprinted polymers (MIPs). The sensor integrates the merits of the high sensitivity of NCQD and good selectivity of MIPs, and can be significantly quenched upon interaction with doxycycline.