Antisense Oligonucleotides and RNA Interference - Challenges in Delivery of Therapeutic Genomics and Proteomics - page 357

7.8.2.6 Hydrodynamic Injection
Injecting AS ODNs in a physiological buffer locally to the diseased site effectively con-
centrates them at the site of injection. The method is simple, reproducible, and highly
efficient, with transfection efficiency dependent on the anatomy of the target organ, the
injection volume, and the injection rate [162,184] . Being nonspecific, hydrodynamic
delivery can be used for intracellular delivery of any water-soluble compounds, small
colloidal particles, or even viruses. This technique allows direct transfer of substances
into cytoplasm without endocytosis. Hydrodynamic renal vein injection of an AS ODN
against connective tissue growth factor has been reported to treat renal fibrosis in rats
[185] . However, due to the large injection volumes and invasiveness of the technique, it
is not widely used clinically. Recently, an improvement in the precision and reproduc-
ibility of this technique has been reported, using a computer-controlled catheter-guided
injection device. Successful gene delivery to the liver, kidney, and muscles of rodents
has been observed with this device [12,156] .
7.8.2.7 Electroporation
Electroporation is a technique for local delivery of AS ODNs, making use of an exter-
nally applied electrical field to increase the electrical conductivity and permeability of
the cellular plasma membrane by creating localized pores in the membrane. Treatment
of tissue with hyaluronidase prior to injection of AS ODNs may significantly enhance
transfection due to improved distribution of ODNs within the tissue [157,162] . The
technique has been reported to successfully deliver phosphorothioate-modified ODNs
against c-myc proto-oncogene of U937 cells [186] and fluorescein-labeled AS ODNs
to the promoters of the proto-oncogene c-myb (24-mer) transdermally [187] . However,
the technique has limited use because of high cell mortality and suffers from draw-
backs such as difficulty in transfecting cells in a large area of tissues due to a limited
effective range of approximately 1 cm between the electrodes. Furthermore, surgery is
required to place the electrodes into deep-seated organs. Process parameters like volt-
age, length, and number of electric pulses can be optimized to get maximum transfec-
tion with minimum cell mortality.
7.8.2.8 Ultrasound-Mediated Antisense Drug Delivery
Ultrasound-mediated antisense drug delivery is a noninvasive physical method of
transfection that makes use of ultrasound waves of optimum strength for optimal
time to facilitate permeation of AS ODNs into the target cells. The ultrasound cre-
ates pores in the cellular membrane, facilitating passive diffusion of ODNs across
the membrane. The transfection efficiency is dependent on the size and local con-
centration of ODNs, and better transfection is obtained when complexes of ONDs
with cationic lipids are used [162,188] . The technique can be readily used for site-
specific delivery of AS ODNs to soft internal tissues. The method has been reported
to deliver digoxigenin-labelled AS ODN to treat prostate cancer in nude mice [189] .
The only drawback associated with ultrasound-mediated antisense drug delivery is
low transfection efficiency.