Optical Detection of the Spatial Structural Alteration in the Human Brain Tissues/Cells and DNA/Chromatin due to Parkinson's Disease.

Parkinson's disease (PD) is one of the most common neurodegenerative disorders, highlighting the urgent need for early, reliable biomarkers. Structural disorder at the subcellular level, particularly in nuclear components such as DNA/chromatin, offers a promising diagnostic target. In this study, we applied two mesoscopic physics-based optical techniques-partial wave spectroscopy (PWS) and inverse participation ratio (IPR)-to quantify nanoscale structural alterations in postmortem human brain tissues and nuclei. Both PWS and IPR revealed a significant increase in structural disorder and mass density fluctuations in DNA/chromatin of PD samples. These abnormalities are potentially linked to the pathological aggregation of alpha-synuclein in the substantia nigra, a hallmark of PD-related neurodegeneration. Complementary histological analyses supported the optical findings, validating the presence of disrupted microarchitecture. Our results establish PWS and IPR as sensitive optical/photonics tools for detecting early nanoscale changes in PD, offering a novel path toward improved diagnosis and understanding of disease progression.