Application of sulfur and nitrogen doped carbon quantum dots as sensitive fluorescent nanosensors for the determination of saxagliptin and gliclazide

In this study, highly fluorescent sulfur and nitrogen doped carbon quantum
dots (S,N-CQDs) were used as fluorescent nanosensors for direct
spectrofluorimetric estimation of each of gliclazide and saxagliptin
without any pre-derivatization steps for the first time. S,N-CQDs were
synthesized employing a simple hydrothermal technique using citric acid
and thiosemicarbazide. The produced S,N-CQDs were characterized using
different techniques including fluorescence emission spectroscopy, UV
spectrophotometry, high resolution transmission electron microscopy, and
FT-IR spectroscopy. Following excitation at 360 nm, S,N-CQDs exhibited a
strong emission peak at 430 nm. The native fluorescence of S,N-CQDs was
quantitatively enhanced by addition of increased concentrations of the
studied drugs. The fluorescence enhancement of S,N-CQDs and the
concentrations of the studied drugs revealed a wide linear relationship in
the range of 30.0-500.0 μM and 75.0-600.0 µM with limits of
detection of 5.0 μM and 10.15 µM for gliclazide and saxagliptin,
respectively. The proposed method was efficiently utilized for
determination of cited drugs in their commercial tablets with % recoveries
ranging from 98.6 to 101.2% and low % RSD values (less than 2%). The
mechanism of interaction between S,N-CQDs and the two drugs was studied.
Validation of the proposed method was carried out in accordance with ICH
guidelines.