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 (r2 = 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.