Portable colorimetric device for low-density lipoproteins detection using aptamer-enhanced NiMnFe layered double hydroxide nanozyme.

A portable colorimetric platform was developed for rapid, selective, and sensitive detection of cholesterol-enriched low-density lipoprotein (LDL-C) in plasma by exploiting the aptamer-enhanced catalytic activity of NiMnFe layered double hydroxides (NiMnFe-LDHs). Unlike conventional enzymatic colorimetric assays and ELISA, which are costly, time-consuming, and reliant on sophisticated instrumentation, this system enables direct image acquisition and automated analysis using a single-board computer, thereby reducing assay time, operational complexity, and user dependence. Functionalization of NiMnFe-LDHs with an LDL-specific aptamer improves nanomaterial dispersion through electrostatic repulsion, increasing exposure of catalytic active sites and enhancing hydroxyl radical (•OH) generation. In addition, π–π interactions and hydrogen bonding between the aptamer and 3,3′,5,5′-tetramethylbenzidine (TMB) improve substrate affinity, further strengthening the peroxidase-like activity of the NiMnFe-LDHs@aptamer system. Upon LDL-C binding, formation of an LDL-C/aptamer corona partially blocks the LDH surface, limiting access of TMB and H2O2 to catalytic sites. This suppresses •OH generation and TMB oxidation, resulting in a concentration-dependent decrease in colorimetric signal. The portable device achieved a linear detection range of 0.05–1.25 mg dL⁻¹ with a detection limit of 0.04 mg dL⁻¹. Although compatible with 96-well plates, the system’s key advantage lies in its integrated imaging and processing workflow, enabling scalable, high-throughput, and decentralized LDL-C diagnostics with potential extension to other biomarkers.