Coreactant-Filled Hydrogel at Ruthenium-Labeled Brain Tissue Section for Electrochemiluminescence Imaging in Gel

Here, an electrochemiluminescence (ECL) imaging technique in gel is established to visualize single ruthenium-labeled brain tissue sections using a coreactant (e.g., tripropylamine, TPA) filled agarose hydrogel, instead of the coreactant in solution. The confined space between the gel and the tissue section restricts the diffusion of intermediates during the ECL reaction, resulting in enhanced and localized ECL emission, thereby improving the microstructural resolution. Accordingly, spatial heterogeneity in the ECL signals on the mouse midbrain tissue sections was observed, which primarily results from the selective impact of intrinsic tissue structural differences on the local diffusion-limited microenvironment under gel confinement. Consequently, this gel-confined ECL imaging technique can directly translate the intrinsic biophysical differences in neuroanatomy into quantifiable imaging signals without relying on complex immunohistochemical staining or high-resolution optical systems. Furthermore, the imaging method in gel offers relatively good stability over days and repeated imaging. These advantages lay the groundwork for future long-term sample preservation and potential clinical applications.