ABSTRACT
Acknowledgments ............................................................................................ 384
References ........................................................................................................ 384
As mentioned previously in this book, one of the major obstacles in drug delivery
today is the low bioavailability of hydrophilic compounds, such as oligonucleotides
(ON). The main reason for this is the inability of these substances to transverse the
lipid membrane of cells. ONs are interesting therapeutical tools that can be used as
decoys and sequester transcription factors, as well as to initiate degradation of RNA
in the form of short interfering RNAs (siRNA). To overcome the bioavailability
problem and problems associated with delivery of these macromolecules, such as
nuclease degradation, endosomal trapping, and poor nuclear targeting, several
carrier systems have been developed, as reviewed by Gardlik et al.1 These delivery
systems mainly include viruses and nonviral vectors such as polycations and
cationic liposomes. Viruses are generally considered to be more efficient than
nonviral vectors but are potentially immunogenic in vivo. Although polycations and
cationic liposomes are widely used on a routine basis today, they are still not
efficient enough or are too toxic for in vivo applications.
