Chitosan-carbon quantum dots as a new platform for highly sensitive insulin impedimetric aptasensor

Considering the importance of measuring insulin in the prevention and diagnosis of diabetes-related illnesses, here we introduced an ultrasensitive electrochemical aptamer-based sensor for detection of insulin in human blood serum. In this research, carbon quantum dots (CQDs) were synthesized using simple, fast and cheap methods from candle soot. By dispersion of the CQDs in chitosan (Chi) matrix, homogenous CQD-Chit nano-composite was obtained. The experimental results demonstrate the good advantages of proposed CQD-Chit nano-composite, such as homogeneity, high stability and multiple amino groups for covalent immobilization of aptamer and fabrication of highly selective insulin aptasensor. CQD-Chit nano-composite was characterized by the transmission electron microscopy (TEM), field emission scanning electron microscopy (FESEM), energy dispersive X-ray spectroscopy (EDAX), Fourier transform infrared (FTIR) spectroscopy and electrochemical techniques. Under the optimized conditions with electrochemical impedance spectroscopy technique, a linear response ranges from 0.5 nM to 10 nM with the sensitivity of 80.07 Ω/nM and the very low detection limit of 106.8 pM was obtained for insulin detection. The fabricated aptasensor is validated in comparison with standard methods for detection of insulin in human blood serum. Also, the analytical performances of the fabricated aptasensor can be a superiority compared to the current insulin electrochemical biosensors.