Intracellular Delivery of Native Proteins Facilitated by Cell-Penetrating Poly(disulfide)s. 
Intracellular delivery of therapeutic proteins is highly challenging and in most cases requires chemical or genetic modifications.  Herein, two complementary approaches for endocytosis-independent delivery of proteins to live mammalian cells are reported.  By using either a "glycan" tag naturally derived from glycosylated proteins or a "traceless" tag that could reversibly label native lysines on non-glycosylated proteins, followed by bioorthogonal conjugation with cell-penetrating poly(disulfide)s (CPDs), we achieved intracellular delivery of proteins (including antibodies and enzymes) which, upon spontaneous degradation of CPDs, led to successful release of their "native" functional forms with immediate bioavailability.