A label-free electrochemical aptasensor for low-density lipoprotein detection using MoS2-Au-Fc nanosheets as a high-performance redox indicator

Abstract

Low-density lipoprotein (LDL) is a key biomarker involved in cardiovascular disease (CVD) risk assessment. Early-stage diagnosis of CVD complications by monitoring LDL levels could be a significant clinical tool and the first step toward adopting efficient therapy. Herein, a novel label-free electrochemical aptasensor for LDL detection was developed via the molybdenum disulfide-gold nanoparticle- ferrocene-carboxylic acid nanosheets (MoS2-Au-Fc NSs) enhanced signal amplification strategy. The MoS2-Au-Fc NSs were used not only as the biocompatible substrate for LDL aptamer (LDLapt) stabilization due to the increasing electrical conductivity and effective surface area, but also as a redox probe for monitoring the changes of the electrochemical signal because of good electroactive properties of Fc. The aptasensor fabrication steps were investigated by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and scanning electron microscopy (SEM). When LDL was captured onto the sensor via the specific affinity of the LDLapt, the formed LDLapt-LDL complexes shed from the electrode and enhanced the electron transfer rate on the electrode surface, resulting in an increase of the peak current. Thus, LDL can be easily detected by measuring the changes of peak current. Under ideal circumstances, the aptasensor was linearly correlated with logarithm LDL concentration from 0.001 to 100.0 μg/mL with R2 of 0.9914, and a low detection limit of 0.42 ng/mL. Furthermore, the LDL detected by aptasensor in actual serum samples with good actual errors (0.73%–5.00%) and satisfactory relative standard deviations (RSDs) (0.04%–0.84%). This study provides a new analytical method for measuring the level of LDL which is specifically up-regulated in CVD patients at an early stage.