A Microfluidic Aptamer-Based Sensor for Detection of Mercury(II) and Lead(II) Ions in Water

Abstract

Heavy metal contaminants have serious consequences for the environment and human health. Consequently, effective methods for detecting their presence, particularly in water and food, are urgently required. Accordingly, the present study proposes a sensor capable of detecting mercury Hg(II) and lead Pb(II) ions simultaneously, using graphene oxide (GO) as a quenching agent and an aptamer solution as a reagent. In the proposed device, the aptamer sequences are labeled by FAM and HEX fluorescent dyes, respectively, and are mixed well with 500 ppm GO solution before injection into one inlet of the microchannel, and the heavy metal sample solution is injected into another inlet. The presence of Hg(II) and Pb(II) ions is then detected by measuring the change in the fluorescence intensity of the GO/aptamer suspension as the aptamer molecules undergo fluorescence resonance energy transfer (FRET). The selectivity of these two ions is also shown to be clear among other mixed heavy metal ions. The experimental results show that the aptamer sensors have a linear range of 10~250 nM (i.e., 2.0~50 ppb) for Hg(II) ions and 10~100 nM (i.e., 2.1~20.7 ppb) for Pb(II) ions. Furthermore, the limit of detection is around 0.70 ppb and 0.53 ppb for Hg(II) and Pb(II), respectively, which is lower than the maximum limits of 6 ppb and 10 ppb prescribed by the World Health Organization (WHO) for Hg(II) and Pb(II) in drinking water, respectively.

Low-cost microfluidics: Towards affordable environmental monitoring and assessment

“…Micromilling and 3D printed devices were explored for heavy metal detection (Santangelo et al, 2019;Huang et al, 2021) and though these devices were successful experimentally and demonstrated enough accuracy to be used in the lab, the dependency on external pumping systems and trained personnel still limit their market potential. When it comes to processing samples with large volumes, injection molded devices have emerged as a major player.…”

Review on the Selection of Aptamers and Application in Paper-Based Sensors

“…A microfluidic aptamer sensor capable of detecting Hg and Pb ions simultaneously was developed by Huang et al [85]. The GO was used as the quencher, and an octanoic acid solution was used as the reagent.…”

Recent Achievements in Electrochemical and Optical Nucleic Acids Based Detection of Metal Ions

“…In the case of microfluidic devices integrated with biosensors and dedicated to metal ions detection, such an approach is still in its very initial stage; however, progress made for medical (biomarkers) application can be fully utilized. One such example is the device proposed by Huang, W.-H. et al [ 118 ]. The authors proposed a device capable of simultaneous detection of Hg 2+ and Pb 2+ ions ( Figure 31 ).…”

“… ( A ) experimental setup; ( B ) Schematic integration of experimental setup; ( C , D ) exemplary result of simultaneous detection of Hg 2+ and Pb 2+ ions in two concentrations, 10 nM and 100 nM respectively [ 118 ]. …”