Researchers at the University of Michigan and Idaho State University have engineered an encapsulin-based protein nanocage capable of loading cargo proteins directly after assembly, Nature Communications reported on August 14, 2026. The discovery addresses cytosolic delivery of therapeutic proteins, an area that has presented persistent challenges in drug delivery research.
The platform centers on a protein nanocage designated QtEnc, which exhibits permeability properties that allow in vitro cargo internalization in a single step. Unlike existing protein nanocage cargo loading systems, QtEnc can encapsulate proteins as large as 482 kilodaltons and allows multiplexed co-encapsulation of multiple payloads with tunable ratios.
Using the nanocage, the researchers developed a modular delivery vehicle termed QtEncNC. The carrier incorporates two specialized components: a pH-responsive cargo detachment module and an endosomal escape module. Under low pH conditions, the detachment module triggers the release of loaded proteins from the assembled nanocage shell, while the escape module facilitates cytosolic delivery. In laboratory tests on HeLa cells, the team demonstrated cytosolic delivery using the cytotoxic protein BLF1 as a model payload.
The study was authored by Seokmu Kwon, Michael P. Andreas, Jesse A. Jones, and Tobias W. Giessen across the University of Michigan's Department of Biological Chemistry and Department of Chemical Engineering alongside Idaho State University's Department of Biomedical and Pharmaceutical Sciences. Research support came from the University of Michigan Cryo-EM Facility, backed by the U-M Life Sciences Institute and U-M Biosciences Initiative, with cryo-electron tomography assistance from Vinson Lam. Structural graphics were performed with UCSF ChimeraX under National Institutes of Health grant R01GM129325. Funding included NIH grant R35GM133325, NSF grant 2342136, an Asan Foundation Biomedical Science Scholarship, and a Rackham Predoctoral Fellowship. Kwon and Giessen have filed a patent application for the platform.
