*2.2. Raman Spectroscopy*

A Raman spectroscopy system (Horiba Jobin Yvon-XploRA PLUS) collected Raman spectra of ex vivo kidney tissue samples (Figure 1b). A 532 nm laser was projected onto room-temperature kidney sections, and the resulting Raman scattering between 700 and 3500 cm−<sup>1</sup> was recorded through a CCD camera. Measurements were taken at various pathological sites, including glomeruli and other structures within the cortical region.

The collected Raman spectra were processed using MATLAB 2018b (MathWorks, Inc., Natick, MA, USA) with baseline and background correction [38], spectral smoothing through a Savitzky-Golay filter [39], and normalization based on water content (3100–3400 cm−1). For multivariate and machine learning analysis, the biological fingerprint region (800–1800 cm<sup>−</sup>1) was selected, which contains molecular information including proteins, lipids, and other tissue constituents.
