Highly sensitive dual-mode assay for tetracycline detection

A dualmode tetracycline (TC) assay was developed based on a colloidally stable mixture of TC-specific aptamer stabilized AuNPs (Apt-stabilized AuNPs) and graphite carbon nitride nanosheets (g-C₃N₄) for sensitive detection of TC. The presence of TC in the solution could be identified based on the colorimetric and fluorescent signals. This dual-mode assay requires no salt during TC detection and has high sensitivity, allowing detection limits (LOD) of TC to 1.0 × 10⁻¹⁶ M with a wide dynamic detection range (six orders of magnitude, from 5.0 × 10⁻¹⁶ to 5.0 × 10⁻¹¹ M), and exhibits good selectivity for TC over other metal cations, antibiotics, amino acids, and proteins. The mechanism of this dual-mode assay for TC detection was investigated in detail. Moreover, the amount of TC in actual samples (spiked drinking water and milk) was successfully monitored. The findings provide valuable guidance in developing an advanced platform for detecting TC and other antibiotics.