Effect of Filter Sterilization on the Proteomic Profile of Saliva

Objectives: Contamination of sterile human saliva with internal microorganisms poses a significant challenge for in-vitro studies. Filtration is a standard method of removing microorganisms from saliva. Studies have compared saliva filtration with other sterilization techniques, but the impact of different filtration systems on saliva's protein composition is unexplored. This study assessed the effect of six common filtration systems on the proteomics profile of saliva.
Methods: Human saliva was collected from five healthy individuals. Filters made from Polyethersulfone (PES), Cellulose Nitrate (CN), and Surfactant-free Cellulose Acetate (SFCA), with pore sizes of 0.2μm and 0.45μm, were evaluated. Filtrate saliva was incubated on Brain Heart Infusion agar to check for sterility. Bicinchoninic acid (BCA) assay and tandem mass spectrometry were used to evaluate any changes to the protein composition of saliva. The experiment was repeated six times (n=6). Kruskal-Wallis and subsequent Dunn’s testing were used to assess the results of the BCA assay (α=1%).
Results: A total of 125 proteins were identified, with 11 proteins exclusive to Whole Saliva Supernatant (WSS) and only one protein exclusive to filtered saliva (SFCA 0.45μm). A significant decrease in protein concentration was observed (p<.01) in both CN filters while also affecting the proteomic profile of human saliva. SFCA and PES filters had no discernible effect on protein concentration or composition. All filters, regardless of pore size, achieved effective sterilization.
Conclusions: This research highlights the role of filtration systems in shaping saliva's protein composition, emphasizing the need for careful selection of the appropriate filtration system. Future research should assess the impact of filtration on the acquired pellicle and focus on comprehensive standardization of saliva collection and analysis methodologies to advance the development of national/international saliva banks for diagnostic application.