Stability of tear fluid biomarkers under accessible storage conditions assessed by Raman spectroscopy

Tear fluid is a promising diagnostic tool, yet standard storage at −80∘C requires expensive, often inaccessible equipment. To establish robust standard operating procedures and facilitate biobanking, it is essential to identify more practical storage alternatives. This study evaluates the stability of tear fluid components under various accessible storage conditions, comparing liquid-state preservation and desiccated spot techniques. Molecular stability was assessed using Raman spectroscopy, a non-destructive technique ideal for multi-class biomolecule characterization. We compared liquid samples (−20∘C storage and freeze-thaw cycles) against desiccated samples stored at +20∘C, +4∘C, and −20∘C. Liquid samples at −20∘C demonstrated negligible spectral alterations, while desiccated samples maintained spectral integrity at room temperature (+20∘C). These results suggest that both liquid storage at −20∘C and desiccation offer viable, cost-effective alternatives to ultra-low temperature storage for tear-based diagnostics.