Abstract
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 ((166)Dy/(166)Ho) in vivo generator shows great potential for treating large malignancies due to the long half-life time of the mother nuclide (166)Dy and the emission of high energy β(-) from the daughter nuclide (166)Ho. However, the internal conversion occurring after β(-) decay from (166)Dy to (166)Ho could cause the release of about 72% of (166)Ho when (166)Dy is bound to conventional chelators. The aim of this study is to develop a nanoparticle based carrier for (166)Dy/(166)Ho in vivo generator such that the loss of the daughter nuclide (166)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 (166)Dy and studied the retention of both (166)Dy and (166)Ho under various conditions. RESULTS: The (166)Dy was co-reduced with gold and platinum precursor to form the (166)DyAu@AuNPs and (166)DyPtAuNPs. The (166)Dy radiolabelling efficiency was determined to be 60% and 70% for the two types of nanoparticles respectively. The retention of (166)Dy and (166)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 (166)Dy and (166)Ho was retained. The results show that the incorporation of (166)Dy in AuNPs can prevent the escape of (166)Ho released due to internal conversion. CONCLUSION: We developed a chelator-free radiolabelling method for (166)Dy with good radiolabelling efficiency and very high stability and retention of the daughter nuclide (166)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.