Core-shell structured gold nanoparticles as carrier for Dy/Ho in vivo generator.

Background: Radionuclide therapy (RNT) has become a very important treatment modality for cancer nowadays. Comparing with other cancer treatment options, sufficient efficacy could be achieved in RNT with lower toxicity. β emitters are frequently used in RNT due to the long tissue penetration depth of the β particles. The dysprosium-166/holmium-166 (Dy/Ho) in vivo generator shows great potential for treating large malignancies due to the long half-life time of the mother nuclide Dy and the emission of high energy β from the daughter nuclide Ho. However, the internal conversion occurring after β decay from Dy to Ho could cause the release of about 72% of Ho when Dy is bound to conventional chelators. The aim of this study is to develop a nanoparticle based carrier for Dy/Ho in vivo generator such that the loss of the daughter nuclide Ho induced by internal conversion is prevented. To achieve this goal, we radiolabelled platinum-gold bimetallic nanoparticles (PtAuNPs) and core-shell structured gold nanoparticles (AuNPs) with Dy and studied the retention of both Dy and Ho under various conditions.

Results: The Dy was co-reduced with gold and platinum precursor to form the DyAu@AuNPs and DyPtAuNPs. The Dy radiolabelling efficiency was determined to be 60% and 70% for the two types of nanoparticles respectively. The retention of Dy and Ho were tested in MiliQ water or 2.5 mM DTPA for a period of 72 h. In both cases, more than 90% of both Dy and Ho was retained. The results show that the incorporation of Dy in AuNPs can prevent the escape of Ho released due to internal conversion.

Conclusion: We developed a chelator-free radiolabelling method for Dy with good radiolabelling efficiency and very high stability and retention of the daughter nuclide Ho. The results from this study indicate that to avoid the loss of the daughter radionuclides by internal conversion, carriers composed of electron-rich materials should be used.