Design and preparation of proline, tryptophan and poly-l-lysine functionalized magnetic nanoparticles and their radiolabeling with 131I and 177Lu for potential theranostic use

[Display omitted] •Proline, tryptophan, and poly-l-lysine functionalized MNPs were synthesized and characterized.•Dispersions of PLL-MNPs have demonstrated heating ability under applied magnetic fields.•Functionalized MNPs were radiolabeled with theranostic radionuclides 131I and 177Lu.•The highest radiochemical purity, in vitro and in vivo stability were obtained for 177Lu–PLL-MNPs.•177Lu–PLL-MNPs heated at 80 °C exhibits promising potential as a theranostic nanoagent. Surface modification of magnetic nanoparticles with poly-l-lysine, proline, and tryptophan was used to design potential theranostic agents for the application in cancer diagnosis and radionuclide-hyperthermia therapy. Characterization of bare and functionalized magnetic nanoparticles was performed in detail. The transparency of the examined magnetic nanoparticles was measured in the non-alternating magnetic field for a complete and better understanding of hyperthermia. For the first time amino acid-functionalized magnetic nanoparticles were labeled with theranostic radionuclides 131I and 177Lu. The specific absorption rate (SAR) procured for poly-l-lysine functionalized magnetic nanoparticles (SAR values of 99.7 W/g at H0 = 15.9 kA/m and resonant frequency of 252 kHz) demonstrated their possible application in magnetic hyperthermia. Poly-l-lysine functionalized magnetic nanoparticles labeled with 177Lu showed the highest radiochemical purity (>99.00 %) and in vitro stability in saline and serum (>98.00 % up to 96 h). The in vivo analysis performed after their intravenous administration in healthy Wistar rats presented good in vivo stability for several days. Encouraging results as well as magnetic and radiochemical properties of 177Lu–PLL-MNPs (80 °C) justify their further testing toward the potential use as theranostic agents for diagnostic and combined radionuclide-hyperthermia therapeutic applications.