An ultrasensitive aptasensor for hemin and hemoglobin based on signal amplification via electrocatalytic oxygen reduction.

The present study aims at the fabrication of a novel electrochemical aptasensor, Ap-GA-AMSN-GCE, for the label-free determination of hemin and hemoglobin (Hb). Basically, the electrochemical reduction current of hemin or Hb incubated on Ap-GA-AMSN-GCE in the presence of oxygen serves as an excellent signal for quantitative determination of these analytes. By differential pulse voltammetry, the calibration plot was linear in the concentration range of 1.0 × 10(-19)-1.0 × 10(-6) M of hemin and Hb. Also, the detection limits, DL, of hemin and Hb were found to be 7.5 × 10(-20) M and 6.5 × 10(-20) M respectively. According to the experimental results, using the proposed aptasensor in the absence of any oxygen molecule in the analytical solution, the DL value of hemin was 1.0 × 10(-12) M. The very low DL obtained in the presence of oxygen is due to the excellent electrocatalytic activity of hemin and Hb incubated on the aptasensor for oxygen reduction. This electrocatalytic activity has a key role in bringing about excellent low detection limits, DL, and wide linear concentration ranges of analytes. Finally, this aptasensor was satisfactorily used for the determination of Hb in human blood samples.