Figure 2

Experiment 1: Spectral discrimination of SARS-CoV-2 spike pseudotyped lentiviral particles. (a) Mean pseudo-absorbance (PA) pixel spectra of spike pseudotyped lentiviral particles in phosphate buffered solution (S-LP_PBS) for high concentration (HC = 4.0 × 10³ TU µL⁻¹) and low concentration (LC = 0.8 × 10³ TU µL⁻¹) and their respective negative controls (Ctrl_PBS). (b) Mean pseudo-absorbance (PA) pixel spectra of spike pseudotyped lentiviral particles in artificial saliva (S-LP_AS) for high concentration (HC = 4.0 × 10³ TU µL⁻¹) and low concentration (LC = 0.8 × 10³ TU µL⁻¹) and their respective negative controls (Ctrl_AS). (c) Overall score value of the tenfold cross-validation essay performed in partial least square-discriminant analysis (PLS-DA Model 1) in both preparations (per pixel). Dashed lines represent their linear correlations. (d) Scatter plot of the two latent variables (V1 and V2) used in the PLS-DA Model 1 for different viral concentrations. Brown and green dots represent positive and control samples respectively. (e,f) Spectral feature descriptor (SFD), computed in the band 483–610 nm for S-LP and G-LP samples in phosphate buffered solution (PBS), artificial saliva (AS), and the corresponding culture media as control (Ctrl). ***p-value = 0 using the Wilcoxon rank sum test. Outliers were removed for clarity.