Detection of FAD in Blood Plasma for the Diagnosis of Liver Diseases Using Fluorescent Carbon Quantum Dots

Diagnosis of liver diseases from liquid biopsy remains a significant clinical challenge due to the limitation in the quantification of endogenous biomarkers and the expensive testing methods. Here, we demonstrate the sensing of endogenous blood plasma fluorophores in the presence of carbon quantum dots (CQDs) by the localized surface plasmon resonance (LSPR) method. The enhancement in the emission of endogenous fluorescence signals in the presence of CQDs can be proposed as a simple and rapid method for diagnosing liver diseases. The performance of the sensor has been validated from the interaction and energy transfer between CQDs and endogenous fluorophores by the emission intensity ratio of NADH and FAD endogenous fluorophores, which are the key biomarkers in liver diseases. This ratio determines the redox state of the cell. The shift in the redox ratio determines the metabolic state of the cells, which helps in the discrimination of cancer cells from normal cells. The changes in intensity by resonance energy transfer statistically validated the discrimination between healthy and liver-diseased plasma conditions of cirrhosis and hepatocellular cancer. Selectivity was documented toward fluorescence enhancement with a limit of detection of 2.3 μM. The results show that the simple and rapid sensing of endogenous fluorophores with high sensitivity and specificity has a strong potential for the biochemical diagnosis of liver diseases.