Surface-enhanced Raman spectroscopy (SERS) metabolite profiling of pleural fluid

Pleural effusion is a common complication of lung diseases that requires rapid and accurate diagnosis. However, conventional diagnostic methods are often time-consuming and resource-intensive. Surface-enhanced Raman spectroscopy (SERS) offers a promising, label-free alternative for pleural fluid analysis but remains largely unexplored. In this pilot study, we developed a practical workflow for SERS-based pleural fluid analysis, incorporating preprocessing steps to convert noisy raw data into interpretable spectra, with protein depletion identified as a critical step. Using the optimized SERS protocol, pleural fluid spectra were compared with urine and protein-depleted serum profiles, revealing significant contributions from purine metabolites, particularly uric acid. Moreover, we identified distinct spectral signatures for transudative and exudative pleural fluids. Transudates exhibited sharper, more intense peaks and greater inter-sample variability, whereas exudates showed higher spectral reproducibility, as further supported by Principal Component Analysis. These findings highlight the potential of SERS, implemented with a portable Raman spectrometer, as a rapid, label-free, and cost-effective tool for pleural fluid assessment. Nevertheless, these results are preliminary, and further validation in larger and more diverse patient cohorts is required before integration into point-of-care diagnostic workflows.