Quantitative Analysis of Salmonella typhimurium Based on Elemental-Tags Laser-Induced Breakdown Spectroscopy

Current rapid bacterial detection methods are dedicated to the classification and identification of bacteria. However, there is still a lack of a method for specific quantitative analysis of certain bacteria. In this work, a method based on elemental-tags laser-induced breakdown spectroscopy (ETLIBS) was developed for the rapid and specific quantitative analysis of Salmonella typhimurium (S. ty). Elemental tags were first synthesized by assembling copper nanoparticles (CuNPs) with poly(thymine) (poly-T) template that linked with the aptamer sequence. Under the specific recognition of the aptamer, S. ty can be fully combined with the elemental tags within 30 min to achieve labeling. Afterward, the silicon nanowires (SiNWs) array modified with Au@Ag nanoparticles (SiNWs-Au@Ag) was employed to capture S. ty in 30 min. Attributed to the rapid analysis superiority of ETLIBS mapping, 100 spectra of SiNWs-Au@Ag/S. ty/CuNPs can be obtained in 5 min. It was found that the peak area of the Cu(I) atomic emission line at 324.75 nm fitted by the Voigt profile was linearly related to the bacterial concentration in the range of 10²-10⁶ CFU/mL(R² = 0.978). Furthermore, ETLIBS mapping achieved a low limit of detection (LOD) of 61 CFU/mL and showed good selectivity to S. ty compared with other bacteria. Besides, the method exhibited preeminent detection performance in spiked samples with the recoveries of 87-113%. With the advantages of rapidity, high efficiency, and specificity, the proposed method is expected to be a powerful tool for bacterial detection.