We synthesized statistical poly(2-isopropyl-2-oxazoline-co-2-butyl-2-oxazolines) (POXs) that are molecularly dissolved below their cloud point temperature in aqueous milieu and are incorporated into micellar nanoparticles of biocompatible Pluronic F127 (F127) after heating their solution above transition temperature, T(tr) . A functional comonomer 2-(but-3-enyl)-2-oxazoline copolymerized into one of the POXs (polymer E) allows introduction of fenolic moieties and subsequent radionuclide labeling with iodine-125. Self-assembly of the polymer E with F127 leads to formation of radioactive nanoparticles with hydrodynamic diameter 20 nm in aqueous solution by heating to 37 °C. The nanoparticles are intended to be used as radioimaging tool in solid tumor diagnostics.