Portable smartphone-based RecJf exonuclease-modulated enhanced ratiometric fluorescence bioplatform for rapid visual detection of As.

Arsenite (As), a highly carcinogenic heavy metal ion and widely distributed in nature, can have serious health implications even with minimal exposure. Herein, a portable smartphone device-based ratiometric fluorescence platform was established for sensitive detection of As. The work relied on the use of metal-organic framework-tagged cDNA (PCN-224-cDNA), with high adsorption capability and fluorescence properties, as an internal reference to quench the fluorescence of FAM-anchored aptamer (FAM-Apt) via hybridization. In the presence of As, FAM-Apt specifically bound to As leading to conformational changes, which detached from the PCN-224-cDNA surface. Interestingly, a smartphone-based readout equipment engineered using a 3D-printed hardware device administered the portable detection of As. The limit of detection (LOD) for the proposed ratiometric biosensor was calculated to be 0.021 ng/mL, significantly below WHO's safety threshold. Hence, it demonstrates significant potential for large-scale screening of As residues in food and the environment.