Enhancing the Sensitivity of Colorimetric Aptasensor Through Cd ²⁺ ‐Thymine Interactions in ssDNA Loops for Food Contaminant Detection

ABSTRACT Cadmium contamination of water threatens environmental ecosystems and by entering the food chain, ultimately poses significant risks to human health. In response to this issue, we developed an efficient, sensitive, and user‐friendly colorimetric aptasensor for the rapid detection of cadmium (II) ions (Cd 2+ ) in water. Molecular dynamics (MD) simulations indicated that Cd 2+ binding occurs primarily at a thymine base within the loop region, prompting a rational truncation of noncore sequences. This strategy confirmed that a shorter aptamer exhibits enhanced affinity for Cd 2+ in an AuNP‐based colorimetric aptasensor. This optimization resulted in a broad linear detection range (2–20,000 nM) and a significantly lowered detection limit of 0.27 nM. This detection limit is well below the maximum allowable levels for cadmium in drinking water set by both the World Health Organization (WHO) and the United States Environmental Protection Agency (U.S. EPA), demonstrating its potential for practical detection. Furthermore, the method exhibited excellent reproducibility, selectivity, and stability, yielding promising results in real water samples. This investigation further explores the influence of aptamer length on target detection, paving the way for innovative research ideas to enhance sensor performance.