Cu₂O QDs-Apoferritin as a Sensor Media for Neurotransmitters

Quantum dots (QDs) are considered lucrative especially in the area of biosensors because of their peculiar optical properties. Although II–VI semiconductor QDs such as CdSe are the most studied QDs, their inherent toxicity may hinder safe use in in vivo applications, such as biolabeling procedures. In the present work, non-toxic Cu₂O QDs-apoferritin are efficiently synthesized in the cavity of cage-shaped apoferritin. The Cu₂O QDs are crystalline with an average size of 3 nm. To utilize the Cu₂O QDs-apoferritin as a biosensor, the change in photoluminescence (PL) spectrum is investigated by accompanying its conjugation reaction with neurotransmitters. When the Cu₂O QDs-apoferritin are conjugated with dopamine, significant fluorescence quenching occurred, and the PL intensity exhibited a linear relationship with dopamine concentration in the range of 0.25–10 × 10^–6 m with an R² of 0.9842. Moreover, the results show that Cu₂O QDs-apoferritin have good selectivity for dopamine over gamma-aminobutyric acid, histamine, and ascorbic acid.