Abstract
Here, cation exchange (CE) reactions are exploited to radiolabel ZnSe, ZnS, and CuFeS2 metal chalcogenide nanocrystals (NCs) with 64Cu. The CE protocol requires one simple step, to mix the water-soluble NCs with a 64Cu solution, in the presence of vitamin C used to reduce Cu(II) to Cu(I). Given the quantitative cation replacement on the NCs, a high radiochemical yield, up to 99%, is reached. Also, provided that there is no free 64Cu, no purification step is needed, making the protocol easily translatable to the clinic. A unique aspect of the approach is the achievement of an unprecedentedly high specific activity: by exploiting a volumetric CE, the strategy enables to concentrate a large dose of 64Cu (18.5 MBq) in a small NC dose (0.18 µg), reaching a specific activity of 103 TBq g-1. Finally, the characteristic dielectric resonance peak, still present for the radiolabeled 64Cu:CuFeS2 NCs after the partial-CE reaction, enables the generation of heat under clinical laser exposure (1 W cm-2). The synergic toxicity of photo-ablation and 64Cu ionization is here proven on glioblastoma and epidermoid carcinoma tumor cells, while no intrinsic cytotoxicity is seen from the NC dose employed for these dual experiments.
Highlights
Cation exchange (CE) reactions are exploited to radiolabel zinc selenide (ZnSe), ZnS, and CuFeS2 metal chalcogenide nanocrystals (NCs) with 64Cu
Introduction in terms of the type of ionizing particles that are released and their decay time.[8] 64Cu decays though β− particles (0.573 MeV, Non-stoichiometric copper chalcogenide nanocrystals NCs are 39%) and electron capture (44%) emission, which are useful for mainly known for their localized surface plasmonic resonance radiotherapy applications[9] but it can produce a β+ decay band, which peaks in the near infrared region (NIR).[1]
We synthetized and characterized a multi-anchoring ligand made of poly-isobutylene maleic anhydride (PIMA), equipped with cysteamine units, which act as anchors for the NC surface and having amine-polyethylene glycol-methoxy-terminated (PEG) molecules as water soluble units (Figure 1a), (Figure S3, Supporting Information, for more details).[28]
Summary
Cation exchange (CE) reactions are exploited to radiolabel ZnSe, ZnS, and CuFeS2 metal chalcogenide nanocrystals (NCs) with 64Cu. We demonstrate that performing a quantitative CE reaction is feasible using a 64CuCl2 solution of high specific activity, on water-dispersible chalcogenide-based NCs of different materials, including ZnS, CuFeS2, and ZnSe. In this work, we show that, by using a constant amount of 64Cu on a μg dose of NCs, the specific activity can be varied in a wide range (from 2 to 100 TBq g−1), especially designed for a radiotherapeutic use.
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