Fig 2: Fourier transform infrared (FT-IR) spectra of hesperidin (HSD, dotted line), copper(II) acetate (Cu(II), dashed line), and HSD–Cu(II) complex (full line) on a Cary 630 FT-IR spectrometer equipped with a monolithic design diamond Attenuated Total Reflectance (ATR) accessory (Agilent Technologies Inc.). Hesperidin is a chelating agent of metal multivalent ions (Me2+). The creation of the complex involves -OH groups in ortho- positions that coordinate with divalent cations [1].

Fig 3: ATR-FTIR spectral data of human cohort. (a) Workflow. Sublingual saliva samples were collected from human subjects with known COVID.POS and COVID.NEG status. Follow-up SARS-CoV-2 PCR was conducted for the COVID.POS group on the saliva or swab collected on day of saliva collection (COVID.POSFU.POS or COVID.POSFU.NEG). Clarified saliva adjusted to a final concentration of 75% ethanol was used for ATR-FTIR on an Agilent Cary 630 FTIR, with samples dried (~30 s) on the crystal. Data for each technical replicate were baseline corrected, then normalized to an AUC of 1. (b) Average spectra (3500–650 cm-1) of COVID.NEG and COVID.POS groups. Colored bands indicate chemical components of interest: aliphatic (yellow), amide I/II/III (cyan), saccharide (green), phosphodiester (purple stripes). (c) Canonical plot with symbols indicating the location of sampling; NSW, New South Wales Health Pathology; TPCH, The Prince Charles Hospital; QIMRB, QIMR Berghofer Medical Research Institute. (d) Contingency table for leave-one-out cross-validation of the partial least squares discriminant analysis (PLS-DA) model. Columns represent actual designation, while rows represent predicted categorization. Bold numbers indicate the correct prediction. (e) Average spectra (3500–650 cm-1) for each of the three clinical groups. Labelling as for panel (b).

Fig 4: Measuring adherence by spectroscopy using the Agilent Cary 630 FTIR Spectrometer. A vaginal swab is placed directly on the “diamond” (red arrow) whereby a laser is projected onto the swab to generate a spectral scan. The spectral scan is analyzed through discriminant model algorithms on the laptop for a final “yes” or “no” output

Fig 5: Vibrational spectroscopy units used in this research. (A) Metrohm Mira M3 (785 nm) Raman instrument, (B) handheld Progeny Rigaku (1064 nm), (C) portable Agilent Cary 630 FT-IR device, and (D) handheld Progeny Rigaku (1064 nm) instrument conducting the through-the-bottle analysis.