Smartphone-assisted colorimetric detection of tobramycin based on a dual-split aptamer remodeling-initiated target-hybridization chain reaction

The extensively used tobramycin (TOB) impacts human health and the ecological environment. Herein, we propose a smartphone-assisted, RGB-dependent method for colorimetrically detecting TOB using a dual split aptamer-initiated target hybridization chain reaction (HCR). In our method, four DNA sequences were designed: Sp-a, Sp-b, hairpin H1, and H2. Sp-a and Sp-b contained one split aptamer sequence and one split trigger sequence, respectively, which specifically bound to the target, TOB, forming a ternary complex, bringing the two split triggers close together. This initiated a trigger-H1 reaction, the opening of H1, the hybridization of HI with H2, and the opening of H2. This alternating H1/H2 opening initiated HCR amplification, forming a long double-stranded DNA (dsDNA) structure that did not bind to all the gold nanoparticles (AuNPs), ultimately resulting in some unbound AuNPs and a color change. As the TOB concentration increased, the system's color shifted from wine to blue, facilitating the sensitive colorimetric detection of TOB. The linear detection ranges for UV-Vis spectrometry and smartphone-based sensing were 10 pg mL⁻¹–150 ng mL⁻¹ and 10 pg mL⁻¹–150 ng mL⁻¹, with LODs of 2.49 pg mL⁻¹ and 18.52 pg mL⁻¹, respectively. The highly specific and high-practicability method developed in this study showed good recovery rates in actual milk and lake water samples, providing a new on-site and visual approach for TOB detection.