Conjugation to Polyethylene Glycol Polymer Promotes Aptamer Biodistribution to Healthy and Inflamed Tissues

Here, we examine biodistribution of radiolabeled aptamers and assess the relative ability of different stabilized aptamer compositions (mixed 2'-F/2'-O-Me; fully 2'-O-Me modified) to access inflamed tissues in a murine inflammation model. Biodistribution of 3H-labeled aptamers, including pegylated and unpegylated compositions, was assessed 3 hours postadministration using quantitative whole body autoradiography (QWBA). Aptamer penetration of cells in kidney and liver was also examined at a qualitative level by microautoradiography. To evaluate aptamer distribution to diseased tissues, inflammation was induced locally in animal hind limbs by treatment with carrageenan just prior to aptamer dosing. Aptamer compositions examined exhibited significant variation in distribution levels among organs and tissues. Highest concentrations of radioactivity in whole body tissues for all animals were observed in the kidney and urinary bladder contents. Relatively little radioactivity was associated with brain, spinal cord, and adipose tissue. Overall, the total level of radioactivity in whole body tissues was significantly higher for a 20-kDa PEG conjugate than for other aptamers. Comparatively high levels of the 20-kDa conjugate were seen in well-perfused organs and tissues, including liver, lungs, spleen, bone marrow, and myocardium. A fully 2'-O-Me composition aptamer had the lowest level of radioactivity in whole body tissues but distributed to higher concentrations in the gastrointestinal tract contents relative to other aptamers. Interestingly, the 20-kDa PEG-conjugated aptamer showed significantly higher levels of distribution to inflamed paw tissues than did either unconjugated or fully 2'-O-Me-modified aptamers.