FRET-driven fluorescent aptasensor for ultrasensitive low-density lipoprotein detection integration of sulfur-doped carbon nitride quantum dots and MXene-Gold nanocomposites.

Low-density lipoprotein (LDL) is a critical biomarker for cardiovascular disease (CVD) risk assessment. Accurate and sensitive monitoring of LDL levels in human serum is crucial for timely diagnosis, targeted intervention, and reduction of mortality. In this paper, we constructed a fluorescent aptamer sensor for LDL determination based on sulfur-doped graphitic carbon nitride quantum dots conjugated with LDL aptamer (S-g-CNQDs-LDL) as a fluorescence donor and MXene-supported gold nanoparticles (MXene-Au) as the energy acceptor, based on fluorescence resonance energy transfer (FRET) principle. The sensing mechanism relies on LDL concentration-dependent fluorescence recovery mediated by the disruption of FRET. Under optimal conditions, the fluorescent aptamer sensor exhibited a linear dynamic range of 20.0-100.0 μg/mL regression equation: Y = 0.00874× - 0.07426, R = 0.9900, with a detection limit (LOD) of 0.343 μg/mL. In clinical serum samples, the relative standard deviations (RSD) ranged from 0.48 % to 2.64 %, confirming the sensor's reliability for LDL analysis in biological matrices. The proposed biosensor demonstrates great potential for clinical serum analysis, offering a novel paradigm for point-of-care CVD risk stratification.