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 (LDLApt) immobilized on the photosensitive layers to form LDL-LDLApt 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.