Peroxidase-like Activity of Aptamer-Gold Nanoparticles for Selective and Sensitive Fluorescence Detection of Low-Density Lipoproteins

Low-density lipoprotein cholesterol (LDL-C), commonly called “bad cholesterol”, is crucial to cardiovascular health. Increased LDL-C levels pose a substantial risk to human health. As a result, there is a demand for reliable, affordable, and highly sensitive analytical methods for LDL-C detection. Herein, a facile fluorometric aptasensor for LDL-C detection based on the aptamer-enhanced peroxidase-mimicking activity of gold nanoparticles (AuNPs) has been developed. AuNPs were functionalized with LDL-C-specific thiolated aptamer to enhance their intrinsic peroxidase-like activity, which could effectively catalyze the oxidation of o -phenylenediamine dihydrochloride (OPD) by H 2 O 2 into the yellow-fluorescent product 2,3-diamino phenazine (DAP). The characterization studies confirmed that the presence of the aptamer enhances the affinity of AuNPs toward the OPD substrate, thereby leading to a marked increase in the peroxidase-mimicking activity. Moreover, after being functionalized with an aptamer, increased dispersibility and substrate affinity of AuNPs were achieved. Using LDL-C as a target analyte, under optimum conditions, a linear relationship between smartphone-recorded signal intensity and the logarithm of the analyte concentration was observed in the range of 0.05–1 mg dL –1 and the limit of detection was 0.0230 mg dL –1 . The results agree with those obtained by a clinical laboratory method. This proposed method is readily deployable and a promising prototype for diverse diagnostic applications, particularly in biomarker detection within serum or plasma samples. It holds the potential to yield substantial advantages in point-of-care testing.