Iron oxide nanoparticles as carriers for the Dy-166/Ho-166 in vivo generator

Abstract

Background:
Cancer is one of the leading causes of death worldwide. Targeted radionuclide therapy has become a important treatment, this is when a carrier molecule is attached to a radionuclide to deliver cytotoxic radiation levels to diseased cells. β
− emitters are frequently used in RNT because they have a long penetration depth, such as the dysprosium-166/holmium-166 (166Dy/166Ho) in vivo generator. The 166Dy/166Ho in vivo generator shows great potential for large tumors because of the long half-life time of the mother nuclide 166Dy and the emission of high energy β− from the daughter nuclide 166Ho. Previous research shows the release of 72 % of the 166Ho when 166Ho is bound to conventional chelators due to internal conversion after the β− decay. The aim of this thesis is to synthesize an iron oxide nanoparticle as carrier for the 166Dy/166Ho in vivo generator. This iron oxide nanoparticles (SPIONs) should prevent internal conversion and thus the loss of the daughter nuclide 166Ho.
Results:
The dysprosium doped iron oxide nanoparticles were synthesized successfully with an average diameter of 6.1 ± 1.5 nm, measured with TEM. The DLS and TEM results showed that the SPIONs were aggregating. The labeling efficiency represents how much Dy is retained in the Dy doped SPIONs, for the non-radioactive Dy this was measured with the ICP/OES. The labelling efficiency was 3.21 ± 0.8 %. The 166Dy doped iron oxide nanoparticles were also synthesized successfully with a radiolabelling efficiency of 3.12 ± 2.2 %, measured with a 2480 Wizard 2 Gamma counter. The retention of 166Dy + 166Ho was 79.2 ± 1.8 % after 96 h.
Conclusion:
The retention of 166Dy + 166Ho in iron oxide nanoparticles was 79.2±1.8 % after 96 hours. This is much higher than the retention of 28% by conventional chelators. This means that the iron oxide nanoparticls is a safer carrier for the 166Dy/166Ho in vivo generator than the conventional chelator.