Imaging Genetic Information - Nanotechnology for Biomedical Imaging and Diagnostics - page 366

Watson-crick base pairing with an antisense oligonucleotide. This would presumably
greatly simplify the development of generic delivery systems with the appropriate
pharmacokinetics since the only difference between imaging agents would be the
precise sequence of the antisense agent for a given nucleic acid target. Nucleic acids
have already been extensively exploited for ex vivo diagnostic applications, and
many disease-specific target sequences are known [16-19]. Potential nucleic acid
targets within a cell are duplex DNA residing within the nucleus and in the mitochon-
dria and various RNAs that are transcribed from the DNA such as messenger RNA
(mRNA), ribosomal RNA (rRNA), and noncoding RNAs such as microRNAs
(miRNAs) (Fig. 13.2).

Chromosomal DNA

snoRNA

tRNA

snoRNA + rRNA

lncRNA

rRNA

snoRNA

Nucleolus

rRNA

snoRNA

Pre-mRNA

Pri-miRNA

Cap

AAAA

Cap AAAA

snRNP

Splicing

Nucleus

Cytoplasm

snRNA

Pre-mirna

Dicer

Cap

AAAA

miRNA
duplex rRNA

Translation

tRNA

rRNA

RISC
complex

Protein

fIgure 13.2 Potential nucleic acid targets for genetic imaging agents. Shown are some of
the major nucleic acid metabolism pathways in the nucleus and cytoplasm of a cell. Not shown
are targets in the mitochondrion that contains mtDNA, which encodes its own rRNA, mRNAs,
tRNAs, and ncRNAs.