Extending the lifetime of anticoagulant oligodeoxynucleotide aptamers in blood.
We have investigated (123)I and (125)I DNA aptamer analogs of anticoagulant DNA aptamers to thrombin exosite 1 and exosite 2 for thrombus imaging potential. Two severe problems are rapid clearance from circulating blood and blood nuclease. With aptamers (unlike antisense) the nucleotide analogs used in polymerase chain reaction-selection cycles also must be used in the radiotracer. We investigated 3'-biotin-streptavidin (SA) bioconjugates of the aptamers to alleviate these problems. Blood nuclease assays and biodistribution analysis were used in the mouse and rabbit. We found that 3'-biotin protected the aptamers significantly from blood nuclease in vitro, but it did not slow in vivo clearance. In contrast, the 3'-biotin-SA bioconjugates were resistant to blood nuclease in vitro and were also longer-lived (10-20 times) in vivo. Bioconjugate aptamers retained affinity for thrombin. Two solutions emerge: 1) In noncirculating blood (within a thrombus) 3'-biotin extends aptamer lifetime, whereas 2) in circulating blood (the transport medium), where more aggressive clearance is encountered, 3'-SA extends aptamer lifetime.
Dougan
H
H
TRIUMF,., Vancouver, B.C, Canada. dougan@triumf.ca
Lyster
D M
DM
Vo
C V
CV
Stafford
A
A
Weitz
J I
JI
Hobbs
J B
JB
D000818:Animals; D000925:Anticoagulants / Q000097:blood* / Q000493:pharmacokinetics; D001345:Autoradiography; D001360:Avidin / Q000378:metabolism; D001798:Blood Proteins / Q000378:metabolism; D002851:Chromatography, High Pressure Liquid; D004247:DNA / Q000378:metabolism; D005260:Female; D006207:Half-Life; D007457:Iodine Radioisotopes / Q000493:pharmacokinetics; D007668:Kidney / Q000378:metabolism; D051379:Mice; D009841:Oligonucleotides / Q000097:blood* / Q000493:pharmacokinetics; D011485:Protein Binding; D011817:Rabbits; D051381:Rats; D013917:Thrombin / Q000378:metabolism; D014018:Tissue Distribution
D000925:Anticoagulants; D001798:Blood Proteins; D007457:Iodine Radioisotopes; D009841:Oligonucleotides; D001360:Avidin; D004247:DNA; D013917:Thrombin