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Abstract

Parkinson’s disease (PD) is a progressive neurodegenerative disorder characterized by motor impairments and non-motor symptoms, significantly impacting patients' quality of life. Currently, cerebrospinal fluid (CSF) is the primary biofluid used for PD biomarker studies, notably α-synuclein, despite the invasive nature of lumbar puncture procedures. Recent work has shown that some of these PD biomarkers have been measured in saliva. As an alternative to CSF, saliva can be non-invasively self-collected by patients repeatedly over time to monitor biomarker levels. However, the stability of these biomarkers in saliva needs to be evaluated before saliva can be considered for patient self-collection studies. Therefore, the goal of this study was to determine if α-syn and cortisol levels were stable in saliva using different common sample storage conditions. Salivary samples were analyzed using enzyme-linked immunosorbent assay (ELISA) kits to measure α-synuclein and cortisol levels under various storage conditions, simulating real-world scenarios of home collection and transport. Our findings indicate that both biomarkers are quantifiable in saliva with high reliability and stability. The results showed that cortisol and α-synuclein concentrations were well-maintained at -20°C and -80°C storage conditions, with minimal degradation observed under room temperature overnight storage. Moreover, freeze-thaw cycles did not significantly affect the biomarker stability. These findings support the potential of saliva as a feasible and non-invasive biofluid for PD biomarker analysis, facilitating easier and more frequent monitoring of disease progression. Further studies are warranted to validate these preliminary findings and to establish standardized protocols for saliva collection and storage in clinical settings.

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