A high-sensitivity label-free electrochemical aptasensor for point-of-care measurements of low-density lipoprotein in plasma based on aptamer and MXene-CMCS-Hemin nanocomposites

Cardiovascular disease (CVD) remains a significant worldwide health challenge, with mortality rates rising rapidly. Low-density lipoprotein (LDL) is a crucial serum biomarker for the early diagnosis of CVD, which can significantly improve outcomes and reduce mortality. Herein, a label-free electrochemical aptasensor for rapid detection of LDL was developed based on the titanium carbide–carboxymethyl chitosan–hemin (MXene-CMCS-Hemin) nanocomposites as the electrochemical signal probe. Firstly, gold nanoparticles (Au NPs) were electrodeposited onto a screen-printed carbon electrode (SPCE) to form a conductive substrate. Subsequently, the MXene-CMCS-Hemin nanocomposites were anchored onto the Au NPs/SPCE surface. Then LDL Apt was immobilized on the surface of MXene-CMCS-Hemin/Au NPs/SPCE to construct the electrochemical aptasensor. When LDL specifically bound with the LDL Apt to form LDL-LDL Apt complexes, hindering the electron transfer and reducing the Hemin oxidation current, LDL detection can be achieved via differential pulse voltammetry (DPV). Under optimal circumstances, the changes of Hemin's oxidation current showed a good linear response with LDL concentration in the range of 0.1–4.0 μmol/L with a detection limit of 0.095 μmol/L (S/N = 3). The aptasensor demonstrated good performance with the relative errors of 0.60 % to 6.58 % for the direct detection of LDL in human serum samples, which offers a novel tool for the clinical diagnosis of CVD.