Expanding the potential of paraffin section studies using NanoSuit-correlative light and electron microscopy.

Histological examination using optical microscopy is essential in life sciences and diagnostic medicine, particularly for formalin-fixed paraffin-embedded (FFPE) tissue sections stained with hematoxylin and eosin or 3,3'-diaminobenzidine. However, conventional electron microscopy faces challenges, such as sample destruction, complex processing, and difficulty in correlating light and electron microscopy images. The NanoSuit method overcomes these limitations by forming an ultrathin protective membrane that enhances conductivity and preserves hydrated tissue architecture, enabling high-resolution scanning electron microscopy imaging. In this study, we applied NanoSuit-correlative light and electron microscopy (CLEM) to FFPE sections to assess its potential for non-destructive and reversible electron microscopy characterization. Using NanoSuit-CLEM, we successfully visualized endothelial structures, amyloid deposits, sarcomeres, mitochondria, bacteria, viruses, and foreign body deposits in FFPE sections. Energy-dispersive X-ray spectrometry further facilitated elemental analysis of foreign materials. These findings demonstrate that NanoSuit-CLEM allows for the precise visualization of ultrastructural details in FFPE sections without requiring new equipment. This method holds promise for advancing pathology by improving diagnostic accuracy and enabling multimodal tissue analysis.