Heavy metal pollution resulting from significant heavy metal waste discharge is increasingly serious. Traditional methods for the detection of heavy metal ions have high requirements on external conditions, so developing a sensitive, simple, and reproducible detection method is becoming an urgent need. The aptamer, as a new kind of artificial probe, has received more attention in recent years for its high sensitivity, easy acquisition, wide target range, and wide use in the detection of various harmful substances. The detection platform that an aptamer-based electrochemical biosensor (E-apt sensor) provides is a new approach for the detection of heavy metal ions. Nanomaterials are particularly important in the construction of E-apt sensors, as they can be used as aptamer carriers or sensitizers to stimulate or inhibit electrochemical signals, thus significantly improving the detection sensitivity. This review summarizes the application of different types of nanomaterials in E-apt sensors. The construction methods and research progress of the E-apt sensor based on different working principles are systematically introduced. Moreover, the advantages and challenges of the E-apt sensor in heavy metal ion detection are summarized.

Malachite green oxalate (MG) is a kind of veterinary drug, which is freely soluble in water and hazardous to aquatic products, resulting in food toxicity and human health problems. The demand for effective and sensitive detection of MG residues is increasing in food safety. In this work, three DNA aptamers MG-36-12/16/17 targeting MG with good affinity (K_d values were 169.78, 71.94, and 102.46 μM, respectively) were obtained by Capture-SELEX. Furthermore, MG-36-12, MG-76-16-6A, and MG-36-17 were found to perform sensitively and specifically to detect MG as a sensing probe in a FRET fluorescent aptasensor, where the FAM-labeled aptamer and GO were employed as efficient energy donor–acceptor pair. The linear range of this aptasensor using aptamer MG-36-12 was from 1.71 to 514.29 ng/mL and the LOD was as low as 0.79 ng/mL. Additionally, the fluorescent assay using aptamer MG-36-17 to detect MG exhibited a linear relationship from 1.71 to 857.14 ng/mL and a LOD of 2.13 ng/mL. Meanwhile, the aptasensor showed high specificity to MG with no cross-reactivity to other veterinary drugs and had a mean recovery of 81.54% to 100.96% in actual water samples from the aquatic product market.