Analytical Sciences

Saliva Preparation Method Exploration for ATR-FTIR Spectroscopy: Towards Bio-fluid Based Disease Diagnosis

Daniele Riêra PASCHOTTO,* Breno PUPIN,** Tanmoy T. BHATTACHARJEE,*** and Luís Eduardo Silva SOARES*

*Laboratory of Dentistry and Applied Materials (LDAM), Research and Development Institute (IP & D), Universidade do Vale do Paraíba, São José dos Campos, São Paulo, Brazil
**Laboratory of Molecular Biology, Research and Development Institute (IP & D), Universidade do Vale do Paraíba, São José dos Campos, São Paulo, Brazil
***Sir John Walsh Research Institute, 310 Great King Street, Dunedin 9016, New Zealand

Saliva has garnered a lot of interest as a non-invasive, easy to collect, and biochemical rich sample for attenuated total reflection–Fourier transform infrared spectroscopy (ATR-FTIR) based disease diagnosis. Although a large number of studies have explored its potential, the preparation methods used differ greatly. For large scale clinical studies to aid translation into clinics, the collection/processing methodology needs to be standardized. Therefore, in this study, we explored different saliva collection (spitting, method A/cotton soaking, method B) and processing protocols (unprepared, TS; supernatant from the centrifugation, CS; and drying, C) to find which gives the best ATR-FTIR signals. Analysis showed highest proteins, carbohydrates, amino acids, and nucleic acid + proteins/lipids in BTS, BCS, ACS, and BC, respectively. Notably, only BC shows a 1377 cm⁻¹ nucleic acid band that is also uniquely identified in multivariate analysis. We conclude that the collection-processing protocol should be based on a biochemical component that best gives a differential diagnosis.

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