Imaging Genetic Information - Nanotechnology for Biomedical Imaging and Diagnostics - page 368

Nucleus: DNA, pre-RNA
rRNA, snoRNA, snRNA,
lncRNA, pri-RNA

Probe

NP

A

Probe

Probe

Cytoplasm:
mRNA, miRNA,
rRNA, tRNA

Probe

C

Probe
endosome

B

Probe

Probe

Probe

TOM

TIM

Mitochondrium: DNA, rRNA, tRNA

fIgure 13.3 Biological barriers and general entry modes for nucleic acid-targeted probes.
membrane-impermeable probes can enter the cytoplasm via direct membrane fusion with a
liposome or exosome (path A) or by receptor-mediated or receptor-independent endocytosis
(path B) followed by endosomal escape. If the target is in the nucleus, the probe could enter
through a nuclear pore (NP) via a nuclear localization peptide sequence. If the target is in the
mitochondrion, then the probe could enter through outer and inner mitochondrial membrane
portals (TOm and TIm).

peptides have been identified, however, that afford the opportunity for delivery of
antisense imaging agents [34, 35]. As with genomic DNA, there is the possibility that
DNA binding agent could cause to unwanted mutations or other alterations in the
mitochondrial DNA.

13.2.2 rna as a Biomarker

While DNA, except for special cases, would not appear to be the best target for
genetic imaging agents, RNA has a number of attributes that make it a much more
viable target. First, RNA is often produced in much higher copy number than the
DNA from which it is transcribed, thereby affording the opportunity for a higher