Novel aptasensor for the ultrasensitive detection of kanamycin based on grapheneoxide quantum-dot-linked single-stranded DNA-binding protein

We coupled single-stranded DNA-binding protein (SSB) with graphene oxide quantum dots (GOQDs) to form QDs-SSB, as a new type of fluorescent probe. Considering the superiority of FRET and the urgency of realizing kanamycin (KAN) sensitive detection, we combined this fluorescent probe with Apt-BHQ1, and applied the FRET principle to achieve ultra-trace detection of KAN. The superiority of detection depends on: SSB has a strong affinity for aptamer (apt) in free state but not in collapsed state; The aptamer is in a free state when not bound to the target and is folded when combined with the target. In the absence of KAN, the fluorescence of the QDs-SSB was quenched by Apt-BHQ1 via FRET. However, when the KAN was added to the QDs-SSB/apt-BHQ1 system, the combination of aptamer with KAN caused the aptamer to assume a folded state and lose its ability to bind with SSB, thereby reducing FRET and the fluorescence of QDs-SSB recovery. The detection limit of this aptasensor was low to 6 pg/mL with a linear range of 0.01-90 ng/mL. Moreover, the method had high selectivity, stability, and anti-interference. Thus, this is a promising method that can be widely used for biological detection.