Label-free fluorescent probe based on upconversion nanoparticles for convenient detection of cytochrome c.

Abnormal levels of cytochrome c (Cyt c) are closely associated with various human diseases, including neurodegenerative disorders and cancers. Therefore, the quantitative detection of Cyt c holds significant value for both disease diagnosis and therapeutic efficacy assessment. Herein, we developed two novel label-free fluorescent probes for sensitive Cyt c detection based on upconversion nanoparticles: one functionalized with poly (ethylene glycol) ylated phospholipid (DSPE-PEG) alone, and the other co-functionalized DSPE-PEG combined with triphenylphosphine. The electrostatic interaction generates resulting in a quantifiable fluorescence quenching effect. The proposed method demonstrated excellent performance in the detection of Cyt c in complex matrices, including cell lysates and human blood sample. Notably, it offers significant advantages over conventional assays by simplifying sample preparation, reducing operational steps, and providing rapid response with distinct observable signals, showing great potential for clinical diagnosis and therapeutic monitoring.