This invention discloses an apparatus and method for producing microcavitational activity in aqueous fluids for non-invasive
macromolecule delivery into living cells. A standard electrohydraulic
shock wave lithotripter is fitted with an adjustable ring reflector that shares the same foci as the standard lithotripter hemi-ellipsoidal reflector. A small portion of the spherical
shock wave, generated by the
spark discharge at the first focus (F1), is reflected and diffracted by the ring reflector, resulting in a weak preceding
shock wave approximately 8.5 mus in front of the lithotripter shock wave reflected and diffracted by the hemi-ellipsoidal reflector. The peak negative pressure of the preceding weak shock wave or pulse at F2 can be adjusted from -0.96 to -1.91 MPa, using an output
voltage of 25 kV. Living cells are exposed to the preceding shock wave and the lithotripter shock wave. With optimal pulse combination, the
maximum efficiency of shock wave-induced
cell membrane permeabilization can be enhanced substantially (up to 91%), by applying to the living cells a low dosage of, for example, 50 shocks. In addition, injury to mouse lymphoid cells is significantly increased at
high dosage (up to 50% with shock number >100). The invention thus enables shock wave-inertial microbubble interaction to be used selectively to either enhance the efficiency of shock wave-mediated
macromolecule delivery at low dosage or tissue destruction at
high dosage.