Smartphone-assisted ratiometric fluorescence biosensor for mercury ion detection based on fluorescence-enhanced PCN-224

Fluorescence-enhanced PCN-224 (FE-PCN-224) was prepared by modifying porphyrin MOF PCN-224 by 1 M Tris-HCl. We found that FE-PCN-224 was able to significantly enhance the fluorescence intensity of 6-FAM-labelled aptamer (FAM-Apt) in pure water, while its own fluorescence intensity was not disturbed. Based on the above, a ratiometric fluorescence biosensing platform was constructed relying on the specific recognition of Hg 2+ by T (thymine)-rich aptamers and the PET effect between T-Hg 2+ -T and FAM. The emission of FE-PCN-224 was used as the reference signal, and the emission of FAM-Apt was used as the sensitive response signal for detecting Hg 2+ . Hence, the concentration gradient of Hg 2+ could be accurately identified by the difference of the ratiometric signals F 518 / F 650 . The sensing system has good reliability and high stability. With the support of ImageJ software and mobile phone colour analysis software, convenient quantitative detection was realized through RGB channel analysis of real colour images. Meanwhile the prepared fluorescent colourimetric card can be applied to achieve semi-quantitative detection by the naked eye. The developed convenient biosensor provides a potential route for rapid detection of mercury ion contamination.