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

The extensively used tobramycin (TOB) impacts human health and ecological environment. We proposed a smartphone-assisted RGB-dependent method for colorimetrically detecting TOB using dual split aptamer-initiated target hybridization chain reaction (HCR). Four DNA sequences: Sp-a, Sp-b, hairpin H1, and H2 were designed. Sp-a and Sp-b contained one split aptamer sequence and one split trigger sequence, respectively, which specifically bound to target TOB, forming a ternary complex, bringing close the two split triggers. This initiated a trigger-H1 reaction, opening H1, hybridizing with H2, and opening H2. This alternating H1/H2 opening initiated HCR amplification, forming a long double-stranded DNA (dsDNA) structure not binding to gold nanoparticles (AuNPs), causing the unprotected AuNPs and color change. As TOB concentration increased, the system's color shifted from wine to blue, sensitively detecting TOB via colorimetry. Its detection linear ranges for UV-Vis spectrometer and smartphone-based sensing platform were 10 pg/mL-150 ng/mL and 10 pg/mL-150 ng/mL, with LODs being 2.49 pg/mL and 18.52 pg/mL. This high-specificity, high-practicability method showed good recovery rates in actual milk and lake water samples, providing a new on-site and visual TOB detection approach.