125 ng pBR322 (10 μL supplied in 10 mM Tris–HCl (pH 8.0) with 1 mM ethylenediaminetetraacetic acid (EDTA), Sigma) was mixed with 1 MBq 111In-chloride, 67Ga-chloride or 67Ga-citrate and incubated up to 72 h at 4 °C (final EDTA concentration 0.1 mM). The final volume was 100 μL in Dulbecco's phosphate-buffered saline pH 7.4 (PBS; Thermo Fisher, UK).
Plasmids were co-incubated with 14 mM dimethylsulfoxide (DMSO), excess EDTA (5 mM) or diethylenetriamine pentaacetic acid (DTPA; 5 mM). Controls included untreated plasmid (no radionuclide), external irradiation (where radionuclides in a 50 mL tube were physically separated from plasmid in 1.5 mL microcentrifuge tube inside the 50 mL tube), and equivalent amounts of non-radioactive gallium- (0.69 pmol) and indium-chloride (0.58 pmol) at molar concentrations equivalent to 1 MBq radionuclide.
After treatment, 12.5 ng plasmid on a 0.8% agarose gel, run at 100 V for 25 min, was visualized with Gel Red™ (Biotium, USA) by UV transilluminator (Gel Doc-it, BioRad, UK).
Plasmids were co-incubated with 14 mM dimethylsulfoxide (DMSO), excess EDTA (5 mM) or diethylenetriamine pentaacetic acid (DTPA; 5 mM). Controls included untreated plasmid (no radionuclide), external irradiation (where radionuclides in a 50 mL tube were physically separated from plasmid in 1.5 mL microcentrifuge tube inside the 50 mL tube), and equivalent amounts of non-radioactive gallium- (0.69 pmol) and indium-chloride (0.58 pmol) at molar concentrations equivalent to 1 MBq radionuclide.
After treatment, 12.5 ng plasmid on a 0.8% agarose gel, run at 100 V for 25 min, was visualized with Gel Red™ (Biotium, USA) by UV transilluminator (Gel Doc-it, BioRad, UK).