VIVIT: Resolving trans-scale volumetric biological architectures via ionic glassy tissue

Abstract

Biological structures across scales integrate seamlessly to perform essential functions. While various histological methods have been developed to reveal these intricate structures, preserving the integrity of large-volume architectures while revealing microstructures with high resolution remains a major challenge. Here, we introduce vitreous ionic-liquid-solvent-based volumetric inspection of trans-scale biostructure (VIVIT), a 3D histological method leveraging the chemical properties of ionic liquids. VIVIT transforms biological tissue into an ionic glassy state, which enables optical clearing with minimal distortion and high transparency, preserves tissue from low-temperature crystal damage, and amplifies fluorescent signals from both genetically encoded and immunostained labels, thus yielding precise and reliable mapping of fluorescent signals within intact 3D architectures. Using VIVIT, we demonstrate the link between the modality of synaptic inputs to multisensory thalamic neurons and the targets of their brain-wide outputs and identified aspects of inhibitory control in the human cortex. VIVIT thus offers opportunities to elucidate the organizational principles underlying trans-scale biostructures.

Keywords: Fluorescent imaging; Higher-order thalamus; Histology; Ionic liquid; Neural connectivity; Neuroanatomy; Non-conventional solvent; Tissue clearing; Trans-scale biostructure; Volumetric imaging.