Plasmon-enhanced fluorescence and FTIR spectroscopy of saliva with silver nanoparticles for lung cancer detection.

Abstract

The present study provides a comprehensive investigation of the influence of the localized surface plasmon resonance (LSPR) of silver nanoparticles (AgNPs) on the spectral and luminescent properties of saliva from patients with lung cancer (n = 59), compared with a group of healthy volunteers (n = 31). Significant intergroup differences were identified using absorption and fluorescence spectroscopy, fluorescence lifetime measurements, and Fourier-transform infrared (FTIR) spectroscopy. Saliva samples from cancer patients were characterized by higher optical density, increased luminescence intensity, and the appearance of an emission band at 614 nm, attributed to endogenous porphyrins. The fluorescence lifetime increased from 1.32 ns in the control group to 1.89 ns in samples obtained from patients with lung cancer, indicating alterations in the biochemical microenvironment of salivary fluorophores. The addition of silver nanoparticles resulted in pronounced plasmon-enhanced emission, with the luminescence intensity increasing by 1.5-fold in the control group and by 1.8-fold in the samples from cancer patients. Differences in fluorescence decay kinetics and FTIR spectral profiles indicate distinct interactions between the nanoparticles and biomolecules, as well as an enhanced formation of the biomolecular corona in saliva during lung cancer. Preliminary results of luminescence spectra classification show excellent metrics with a ROC-AUC of 0.932 and specificity/sensitivity of 0.935/0.797, demonstrating the promise of optical diagnostics for tumor markers.

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