Microextraction-Driven Optical Fiber Sensor Coupled with Signal Enhancement by Gold Nanostars for Detection of Antibiotics in Food and Water

In this work, a portable optical fiber-based "microextraction sensing" platform coupled with gold nanostars (Au NSRs) was designed for the detection of kanamycin (Kana). Replaceable optical fibers were used as solid-phase microextraction (SPME) devices and sensing probes. Au NSRs and Kana aptamers were sequentially modified onto a fiber core as sensing elements. The evanescent wave generated from the fiber interacted with the surface of the Au NSR, and the localized surface plasmon resonance (LSPR) effect was triggered. In the presence of Kana, the refractive index of the Au NSR surface changed, causing the LSPR characteristic peak to shift, thereby enabling the quantitative detection of Kana. Benefiting from the strong "hot spot" effect produced by the sharp branches of the Au NSR, the intensity of the signals was greatly increased. Under optimal conditions, the sensing platform exhibited high selectivity toward Kana. The calibration linear range was 0.5-500 nM (<i>r</i>² = 0.997), and a limit of detection of 0.138 nM was achieved. The optical fiber could be easily disassembled and reused. Signal stability remained intact even after a replaceable optical fiber probe was cleaned and used 10 times. The sensor was successfully applied to the analysis of Kana residues in genuine cow's milk samples. The procedure was also applied to river water samples. This assay has unique advantages of low cost, simplicity, and recyclability, making it a promising approach for food analysis and environmental monitoring.