Screening, Post-SELEX Optimization and Application of DNA Aptamers Specific for Tobramycin

Tobramycin (TOB) is an aminoglycoside antibiotic. The residue of TOB in animal-derived foods and environment will be harmful to human health, and therefore the specific detection of TOB residue in food and water is of great importance. Herein, through magnetic beads-based SELEX, overall 37 ssDNA aptamers specific for TOB were screened after ten rounds of selection. The affinity and specificity of these aptamers were evaluated, among which No. 32 aptamer (Ap 32) exhibits excellent performance. Then a post-SELEX optimization of Ap 32 was carried out based on rational design, through which a truncated aptamer with the length of 34 nucleotides (Ap 32-2) was identified as the best aptamer for TOB. Finally, the application of the screened aptamer was explored. A colorimetric assay of TOB was established based on the aptamer-modified gold nanoparticles (AuNPs). In the range from 100 to 1400 nM, the absorbance of AuNPs solution at 520 nm was linearly decreased with the increased concentration of TOB. The detection limit was estimated to be 37.9 nM. The assay was applied to detect TOB residue in honey samples.