Supercharged ferritin nanocages enable universal cytosolic protein delivery.

Efficient intracellular protein delivery represents an essential prerequisite for protein-based biotechnologies and therapeutics targeting intracellular components. However, this process is limited by multiple factors, including nonspecific protein binding, insufficient cellular uptake, inefficient endosomal escape, and inadequate cytosolic protein release. Here we show that by engineering fully recombinant supercharged protein nanocages, we achieve exceptionally high cellular uptake using a strategy we term 'supercharged interface engineering'. By incorporating unnatural amino acids bearing phenylboronic acid groups, we develop a representative protein nanocage, pFn + . Simply mixing pFn+ with protein cargoes forms a noncovalent complex possessing enhanced cellular uptake efficiency, robust endosomal escape capability, and excellent biocompatibility. Notably, this system successfully delivers functional gene-editing tools and therapeutic antibodies in female mouse models. These findings indicate that pFn+ represents a promising platform for enhancing the cytosolic delivery of protein cargoes. Moreover, the proposed supercharged interface engineering strategy is valuable for advancing next-generation intracellular protein delivery systems.