A rapid “cusp-covering” to Au nanostar as plasmonic sensor in a single-drop microreactor for the determination of kanamycin in biosamples

For complicated real sample detection, the metal nanomaterial-based plasmonic sensing strategy always presents great challenge since the reaction was easily affected by the matrix effect. In this study, a single-drop (9 μL) microreactor was designed for a plasmonic “cusp-covering” process to detect residual antibiotic (kanamycin, Kana) in biological samples. A target-triggered catalytic hairpin assembly and hybridization chain reaction (CHA-HCR) amplification cascades strategy was applied to recognize and amplify the signal of Kana. Then, a magnetic three-phase single-drop microextraction was introduced and provided a microreactor for the reaction of covering various thicknesses of Ag on the cusp of Au nanostar, the change in composition and morphology of the materials resulted in a significant shift of localized surface plasmon resonance (LSPR) signal. Moreover, a computational simulation was conducted to prove the advancement of the strategy. Taking advantage of the LSPR effect, the single-drop microreaction system, and the CHA-HCR amplification cascades, an excellent analytical performance was novelly achieved and the detection sensitivity was significantly enhanced. This strategy exhibited a low limit of detection of 33 aM for the determination of Kana with relative standard deviations < 5% (n = 3) and achieved a wide linearity ranging from 0.1 fM to 1 nM. The proposed strategy eliminated the matrix effect of the real sample and provided a stable environment for the minimized detection system, which is capable of sensitively detecting Kana in milk or other real biosamples.