Electrochemical sensor for ultrasensitive sensing of biotin based on heme conjugated with gold nanoparticles and its electrooxidation mechanism.

We report the fabrication of a facile sensor using heme conjugated with gold nanoparticles (AuNPs) in situ on a glass carbon electrode (GCE) for the ultrasensitive determination of biotin without antibody or streptavidin. The use of heme and AuNPs as dual amplifiers allows a very broad detection range from 0.0050 to 50.0000 μmol·L and a very low detection limit of 0.0016 μmol·L. The mechanistic aspects were elucidated using electrochemical analyses and frontier orbital calculations showing that the electrooxidation of biotin involves a one-electron and a one-proton transfer, generating biotin sulfoxide. The heme/AuNPs/GCE sensor exhibited excellent selectivity, reproducibility and stability, indicating high robustness. The recovery was between 97.20 and 105.70% with RSD less than 8.71%, suggesting good practicability. Our studies demonstrate that this approach can be used to detect and quantify biotin in a range of foods, including milk, infant formula, flour, orange juice, mango juice, egg white and egg yolk. Furthermore, all measurements do not require any intricate preparation or pre-treatment of the foods, thus representing a great potential for point-of-care testing.