Carbon-based light addressable potential aptasensor based on the synergy of C-MXene@rGO and OPD@NGQDs for low-density lipoprotein detection

A novel carbon-based light-addressable potentiometric aptasensor (C-LAPS) was constructed for detection low-density lipoprotein (LDL) in serum. Carboxylated Ti₃C₂ MXene @reduced graphene oxide (C-MXene@rGO) was used as interface and o-phenylenediamine functionalized nitrogen-doped graphene quantum dots (OPD@NGQDs) as the photoelectric conversion element. The photosensitive layers composed of OPD@NGQDs/C-MXene@rGO exhibit superior photoelectric conversion efficiency and excellent biocompatibility, which contribute to an improved response signal. When LDL reacts with the LDL aptamer (LDL_Apt) immobilized on the photosensitive layers to form LDL-LDL_Apt complexes, the reaction process can induce the modification of the surface potential in the photosensitive layer, leading to potential shift observed through the I-V curves. The experimental conditions were successfully optimized with few planned tests by applying the Box-Behnken design and response surface methodology aspects of the Design-Expert software. Under the optimal condition, the potential shift had a linear relationship with concentrations of LDL from 0.02 to 0.30 μg/mL. The limit of detection (LOD) was 5.88 ng/mL (S/N = 3) and the sensitivity was 315.20 mV/μg·mL⁻¹. In addition, the LDL C-LAPS demonstrated excellent specificity, reproducibility, and stability in detecting LDL. The sensor performed well in quantifying LDL in real samples. Therefore, the LDL C-LAPS has the potential for clinical applications.