A colorimetric nanoprobe based on dynamic aggregation of SDS-capped silver nanoparticles for tobramycin determination in exhaled breath condensate

A colorimetric nanoprobe was developed for the quantification of tobramycin in exhaled breath condensate (EBC). The nanoprobe consists of silver nanoparticles (Ag NPs) modified with sodium dodecyl sulfate (SDS), which is applied in the presence of sodium metaborate. Characterization of the synthesized SDS-capped Ag NPs by transmission electron microscopy (TEM), Fourier-transform infrared spectroscopy (FT-IR), X-ray powder diffraction (XRD), and energy-dispersive X-ray spectroscopy (EDX) showed that the nanoparticles were well synthesized with nearly uniform size and an average diameter of < 30 nm. Interaction of sodium metaborate with the SDS-capped Ag NPs and tobramycin results in aggregation of the nanoparticles and consequently decreases the absorbance intensity, leading to the production of a new absorbance peak and a color change from yellow to purple. The absorbance intensity was recorded at λ_max = 400 nm and 522 nm and λ₅₂₂/λ₄₀₀ was used as the analytical signal. The experimental parameters were investigated and optimized using a multivariate optimization method (central composite design). The current nanoprobe gives a linear response for tobramycin from 1.0 to 50.0 ng mL⁻¹ with a detection limit of 0.5 ng mL⁻¹. The intra- and inter-day relative standard deviations for five replicated analyses of 10.0 ng mL⁻¹ tobramycin are 2.8% and 4.2%, respectively.