Luminescent gold nanoclusters as a signal reporter for cytochrome c assay with a double signal amplification strategy

Quantitative determination of serum cytochrome c (Cyt c) is of importance in the regular medical assessment of cancer diseases. This work reported a new fluorescence method for the determination of Cyt c with glutathione‐protected gold nanoclusters (GSH‐AuNCs) as a signal reporter. Cyt c was observed to quench the fluorescence of GSH‐AuNCs due to its electron‐rich structure. This inhibitory effect was further strengthened by its peroxidase mimetic catalytic activity on hydrogen peroxide (H2O2)‐mediated oxidation of GSH‐AuNCs. The inhibitory efficiency was linearly related to Cyt c concentrations ranging from 10.0 to 700.0 nM with a limit of detection of 2.7 nM (3sb/S). The relative standard deviation was 3.6% for Cyt c at a 40.0 nM concentration level (n = 11). The practical application of the method was evaluated by the determination of Cyt c in spiked human serum samples. The recoveries were within the range from 92.6 to 104.8%, suggesting its potential application in biomedical and clinical diagnosis. Cytochrome c significantly decreases the fluorescence of glutathione‐protected gold nanoclusters due to its electron‐rich structure and peroxidase mimetic catalytic activity. The double signal amplification strategy allows the determination of Cytochrome c ranging from 10.0 to 700.0 nM.