A portable fluorescent aptamer sensor for rapid quantitative detection of Hg²

Mercury(II) ions (Hg²⁺) are heavy metal ions that can cause human poisoning and can lead to death in severe cases. Therefore, establishing a rapid quantitative detection method for Hg²⁺ is important for protecting human health. In this study, a portable hydrogel-based fluorescent aptasensor was developed for the rapid and quantitative detection of Hg²⁺. A type of RCA/G-quadruplex product was designed during the rolling circle amplification (RCA) process. By combining it with the thioflavin T (ThT) fluorescent dye, a highly efficient RCA-ThT fluorescent probe was obtained, which could sensitively and efficiently recognise Hg²⁺. Furthermore, the RCA-ThT fluorescent probe was physically combined with a hydrogel to construct a novel hydrogel-based fluorescent sensor. The hydrogel combined with the RCA-ThT fluorescent probe was dropped onto the lid of a centrifuge tube. The solution containing Hg²⁺ was added to the same centrifuge tube. The centrifuge tube was inverted so that the solution will come into contact with the sensor. This enabled portable rapid detection, which fully complies with the basic requirements of Point-of-Care Testing (POCT). Additionally, the RGB values were obtained through photo capture, and colorimetric analysis was performed to determine the exact content of Hg²⁺ using the WeChat App. The portable hydrogel-based fluorescent aptamer sensor offered a detection limit of 0.044 μmol L^-1 for Hg²⁺ and a detection range of 1-100 μmol L^-1. The sensor exhibited good stability and immediate detection capabilities, showing promising application prospects in food safety monitoring.