Antibodies
are powerful tools that may potentially find wide applications
in live-cell bioimaging, disease diagnostics, and therapeutics. Their
practical applications have however remained limited thus far, owing
to their inability to cross the cell membrane. Existing approaches
for cytosolic delivery of functional antibodies are available, but
they are constantly plagued by the need for chemical/genetic modifications,
low delivery efficiency, and severe endolysosomal trapping. Consequently,
it is of paramount importance to develop new strategies capable of
highly efficient cytosolic delivery of native antibodies with immediate
bioavailability. Herein, we report a modification-free, convenient
“mix-and-go” strategy for the cytosolic delivery of
native antibodies to different live mammalian cells efficiently, with
minimal endolysosomal trapping and immediate bioavailability. By simply
mixing a cell-permeant bioadaptor (derived from protein A or TRIM21)
with a commercially available off-the-shelf antibody, the resulting
noncovalent complex could be immediately used for intracellular delivery
of native antibodies needed in subsequent cytosolic target engagement.
The versatility of this approach was successfully illustrated in a
number of applications, including antibody-based, live-cell imaging
of the endogenous protein glutathionylation to detect oxidative cell
stress, antibody-based activation of endogenous caspase-3, and inhibition
of endogenous PTP1B activity, and finally TRIM21-mediated endogenous
protein degradation for potential targeted therapy. Our results thus
indicate this newly developed, “mix-and-go” antibody
delivery method should have broad applications in chemical biology
and future drug discovery.