Cell therapy and cellular engineering
begin with internalizing
synthetic biomolecules and functional nanomaterials into primary cells.
Conventionally, electroporation, lipofection, or viral transduction
has been used; however, these are limited by their cytotoxicity, low
scalability, cost, and/or preparation complexity, especially in primary
cells. Thus, a universal intracellular delivery method that outperforms
the existing methods must be established. Here, we present a versatile
intracellular delivery platform that leverages intrinsic inertial
flow developed in a T-junction microchannel with a cavity. The elongational
recirculating flows exerted in the channel substantially stretch the
cells, creating discontinuities on cell membranes, thereby enabling
highly effective internalization of nanomaterials, such as plasmid
DNA (7.9 kbp), mRNA, siRNA, quantum dots, and large nanoparticles
(300 nm), into different cell types, including hard-to-transfect primary
stem and immune cells. We identified that the internalization mechanism
of external cargos during the cell elongation–restoration process
is achieved by both passive diffusion and convection-based rapid solution
exchange across the cell membrane. Using fluidic cell mechanoporation,
we demonstrated a transfection yield superior to that of other state-of-the-art
microfluidic platforms as well as current benchtop techniques, including
lipofectamine and electroporation. In summary, the intracellular delivery
platform developed in the present study enables a high delivery efficiency
(up to 98%), easy operation (single-step), low material cost (<$1),
high scalability (1 × 106 cells/min), minimal cell
perturbation (up to 90%), and cell type/cargo insensitive delivery,
providing a practical and robust approach anticipated to critically
impact cell-based research.