Labeling Peptide Nucleic Acids with Indium-111

Peptide nucleic acids (PNA) are widely used DNA mimics that bind sequence specifically to single- and double-stranded nucleic acids. Hence they are of interest in the design of gene-targeted radiotherapeutics that could deliver radiodamage to designated DNA and/or RNA sites. Here I describe a procedure for incorporation of gamma-emitting radionuclide ¹¹¹In into PNA oligomers. Diethylenetriaminepentaacetic acid (DTPA) was conjugated to a lysine-containing mixed-base PNA. ¹¹¹In-labeled PNAs were obtained by chelation of PNA-DTPA conjugates with ¹¹¹In³⁺ in an acidic aqueous solution.