Label-free colorimetric sensor for Pb2+ determination using catalytic activity of MnO2 nanoflowers and elongated aptamer

In this study, a label-free aptasensor utilizing colorimetric properties was developed to detect Pb2+ with high sensitivity. The approach involved applying modified aptamer which enhanced the oxidase-mimicking activity of MnO2 nanoflowers. This innovative method provides an efficient means for monitoring Pb2+ ions without requiring any labeling techniques. The fundamental principle of this aptasensor is based on the adsorption of a modified aptamer onto MnO2 nanoflowers' surface, which in turn increases their affinity for chromogenic substrates and enhances their catalytic activity. The proposed aptasensor exploits the high sensitivity due to the extension of the aptamer sequence length by terminal deoxynucleotidyl transferase (TdT). Under optimum experimental conditions, the developed colorimetric aptasensor indicated a linear detection range from 4 to 80 nM with a limit of detection (LOD) of 1.4 nM. Moreover, the aptasensor successfully monitored Pb2+ in the drinking water, milk and human serum samples. Henceforth, the colorimetric aptasensor exhibited in this study possesses several benefits such as uncomplicated operation, cost-effectiveness, label-free detection and remarkable sensitivity. Thus rendering it a suitable option for analyzing intricate samples.