Real-time Cd2+ detection at sub-femtomolar level in various liquid media by an aptasensor integrated with microfluidic enrichment

Cadmium ion (Cd 2+ ) is a highly toxic heavy metal pollutant with long biological half-life and strong bioaccumulation, which may cause irreversible damage to human health even at low-dose intake. Sensitive and specific detection of ultra-trace Cd 2+ is of great significance in food safety and environmental monitoring. In this work, a simple-to-use aptasensor to rapidly detect Cd 2+ in various liquid media is developed based on a DNA aptamer modified gold interdigitated electrode (IDE). Capacitance at the solid-liquid interface is utilized to reflect the change caused by adsorbed Cd 2+ . With the microfluidic enrichment by AC electrothermal (ACET) effect, Cd 2+ ions are sped up toward the IDE surface and captured by the probes instantaneously. Owing to the integration of target enrichment and capacitance detection, the sample-to-result time of this sensor is as short as 30 s. This aptasensor as a quantitative detector has a linear response range from 0.45 fM to 4.5 pM, with a limit of detection of 253.16 aM. The selectivity ratio reaches 2320: 1 against non-target metal ions. By detection of Cd 2+ spiked in tap water and olive oil as well as natural residual Cd 2+ in rice leaching solution, the sensor’s applicability and reliability in different practical liquid media are demonstrated.