Gene Delivery Using Chemical Methods - Challenges in Delivery of Therapeutic Genomics and Proteomics - page 149

The in vitro stability of ODN binding to CTAB anchored on poly(isohexylcyanoacryl
ate) (PIHCA) nanospheres demonstrated efficient protection against enzymatic degrada-
tion even after 5 h of incubation with phosphodiesterase or in cell culture media [154] .
Similar in vitro stability was observed with ODNs adsorbed onto DEAE-containing
nanospheres and incubated with DNAse [167] . Few studies showing in vitro activity of
ODN-loaded PIHCA nanospheres were reported. Cell uptake studies performed using
U937 cells demonstrated eightfold or higher uptake of ODN adsorbed to nanospheres
than ODN-free solution, when incubated for 24 h [155] . It was demonstrated that nano-
sphere-anchored antisense ODNs effectively cause point mutation in codon 12 of the
Ha-ras mRNA responsible for expression of the Ha-ras gene. Thus, they hindered pro-
liferation of cells expressing the point-mutated Ha-ras gene [168,169].
The effective concentration required with nanospheres was 100-fold lesser than
free ODN. ODN cholesterol complex loaded onto PIHCA nanospheres demonstrated
efficient sequence-specific inhibition of the proliferation of T24 human bladder car-
cinoma cells. ODN-anchored CTAB-coated nanospheres exhibited superior efficacy
in vivo in the nude mice model, when mice were inoculated with HBL100rasl cells
expressing point-mutated Ha-ras genes. ODN-containing nanospheres inhibited Ha-
ras-dependent tumors in a highly specific manner [168] . The biodistribution stud-
ies performed with PIHCA nanospheres revealed that oligothymidilate was majorly
taken up by liver cells; however, distribution to other organs was reduced, especially
to the kidneys. Thus, using nanospheres, ODN could be delivered to the liver with
certain specificity and the urinary excretion reduced [170] . In vivo studies with
PACA-encapsulated phosphorothioate ODNs directed against EWS Fli-1 chime-
ric RNA were performed in experimental Ewing sarcoma mice [171] . Intratumoral
injection of antisense-loaded nanocapsules, with cumulative dose of 14.4 nanomoles,
led to a significant inhibition of tumor growth. However, free ODN failed to demon-
strate any antisense effect.
4.2.2.4 Poly( N -Vinyl Pyrrolidone)
Poly( N -vinyl pyrrolidone) (PVP) is a water-soluble synthetic homopolymer with gen-
tle adhesive properties ( Fig. 4.7 ). It is available in a broad range of molecular weights,
from 8 to 1300 kDa. It does not form micelles or particulate structures in standard for-
mulations. Usually, viscosity of solution determines the maximum concentration used.
The most common use is as a tablet binder and tablet-coating additive; however, it is
also used in formulations of antibiotics, chemotherapeutic drugs, and ophthalmic and
topical solutions. Commercially available brand names are Plasdone® (International
Specialty Products, Wayne, NJ), Kollidon® (BASF, Ludwigshafen, Germany), and
others. PVP used for gene delivery is normally in the size range of 10-50 kDa [172] .
PVP is classified in a new class of polymer described as protective interactive
noncondensing (PINC TM ) polymers. Mumper et al. have shown use of PINC poly-
mers to enhance the delivery of plasmids to solid tissue, especially skeletal muscle
[172-174] . The major characteristics of this class of polymers are:
1. protection of pDNA from nuclease degradation,
2. dispersion and retention of pDNA throughout the muscle cells,