Embedding and freezing fresh human tissue in OCT using isopentane v1

For many cutting-edge spatial transcriptomic analysis methods, it is essential to prepare and store tissue in a manner that preserves RNA integrity, tissue morphology, and spatial orientation. This protocol describes the process of freezing fresh or fixed and cryoprotected tissues in optimal cutting temperature compound (OCT) using an isopentane-dry ice slurry. Rapid controlled freezing preserves RNA and mimises ice damage, while embedding in OCT prepares tissues for future cryosectioning.