Chromium-51 (51Cr) is an attractive radionuclide for diagnosis, which is usually applied for red cells and platelet radiolabeling. However, commercially available 51Cr produced in nuclear reactors via neutron activation requires long irradiation times and complex separation methods. In this work, five metal–organic frameworks (MIL-100 (Cr), MIL-100 (Fe), MIL-100 (Al), MIL-101 (Cr) and aluminium fumarate MOF (FuAl)) were synthesized and the effect of gamma ray irradiation with a high dose rate and a maximum dose of 6 MGy was investigated. The two chromium-based MOFs, MIL-100 (Cr) and MIL-101 (Cr), were selected as radiation targets to produce high specific activity 51Cr by the Szilard-Chalmers effect. A solid–liquid extraction was applied to extract the produced 51Cr under different conditions, including different extractants, extraction times and pH. The most promising results were achieved when using irradiated MIL-101 (Cr) and EDTA as extracting agent, reaching an enrichment factor of 1132 ± 50.

The original publication of this article contained an incorrect author name. The incorrect and correct information is listed in this correction article. The original article has been updated.

Irradiation of aqueous solutions containing alkyl chlorides generates peroxyl radicals by reactions of alkyl chlorides, aqueous electrons, and dissolved oxygen. The peroxyl radical can oxidize thioethers to sulfoxides, a transformation that has relevance for targeted or triggered drug delivery. However, small-molecule alkyl chlorides can induce liver damage, which limits their potential for application in anticancer therapy. Here, we show that alkyl chlorides bound to a hydrophilic random copolymer chain behave similar to small-molecule alkyl chlorides. Our work shows that using polymeric alkyl chlorides can be an alternative to small-molecule alkyl chlorides provided that the alkyl chloride functionalities are easily accessible to aqueous electrons.

Multifunctional, biocompatible magnetic materials, such as iron oxide nanoparticles (IONPs), hold great potential for biomedical applications including diagnostics (e.g., MRI) and cancer therapy. In particular, they can play a crucial role in advancing cancer thermotherapy by generating heat when administered intratumorally and when exposed to an alternating magnetic field. This heat application is often combined with radio- (chemo)therapy and/or imaging. Consequently, the design of materials for such a multimodal approach requires hybrid nanoparticles that retain their magnetic properties while integrating additional functionalities. This work introduces synthesis and investigation of magnetically enhanced nanoparticles with a palladium core (envisioned for future radiolabeling with therapeutic 103Pd) and a magnetic iron oxide shell containing paramagnetic manganese (Pd/Fe|(nMn)-oxide, n = 0.25 and 0.5). Doping the iron oxide lattice with Mn significantly increases magnetic saturation, boosting specific loss power up to 1.7 times compared to that of undoped analogs. Interestingly, higher Mn-content in Pd/Fe|(0.5Mn)-oxide leads to a pronounced Mn outer rim, enhancing the heating efficiency at 346 kHz and 23 mT and contributing to the water exchange on the surface of the paramagnetically doped nanoparticles, resulting in additional T1 MRI contrast. The enhanced magnetic properties of the hybrid Pd/Fe|Mn-oxide nanoparticles enable effective therapeutic outcomes with injection of only small quantities of the material, offering great potential for effective cancer treatment strategies that combine hyperthermia/thermal ablation with radiotherapy while allowing for real-time monitoring via MRI.

The controlled release of drugs using local ionizing radiation presents a promising approach for targeted cancer treatment, particularly when applied in concurrent radio-chemotherapy. In these approaches, radiation-generated reactive species often play an important role. However, the reactive species that can be used to trigger release have low yield and lack selectivity. Here, we demonstrate the generation of highly oxidative species when aqueous solutions containing low concentrations of organochlorides (such as chloroform) are irradiated with ionizing radiation at therapeutically relevant doses. These reactive species were identified as peroxyl radicals, which formed in a reaction cascade between organochlorides and aqueous electrons. We employed stilbene-based probes to investigate the oxidation process, showing double bond oxidation and cleavage. To translate this reactivity into a radiation-sensitive material, we synthesized a micelle-forming amphiphilic block copolymer that has stilbene as the linker between two blocks. Upon exposure to ionizing radiation, the oxidation of stilbene led to the cleavage of the polymer, which induces the dissociation of the block-copolymer micelles and the release of loaded drugs.

Objective: To investigate the potential of hybrid Pd/Fe-oxide magnetic nanoparticles designed for thermo-brachytherapy of breast cancer, considering their specific loss power (SLP) and clinical constraints in the applied magnetic field. Methods: Hybrid nanoparticles consisting of palladium-core and iron oxide shell of increasing thickness, were suspended in water and their SLPs were measured at varying magnetic fields (12–26 mT peak) and frequencies (50–730 kHz) with a commercial alternating magnetic field generator (magneTherm™ Digital, nanoTherics Ltd.). Results: Validation of the heating device used in this study with commercial HyperMag-C nanoparticles showed a small deviation (±4%) over a period of 1 year, confirming the reliability of the method. The integration of dual thermometers, one in the center and one at the bottom of the sample vial, allowed monitoring of homogeneity of the sample suspensions. SLPs measurements on a series of nanoparticles of increasing sizes showed the highest heating for the diameter of 21 nm (SLP = 225 W/g) at the applied frequencies of 346 and 730 kHz. No heating was observed for the nanoparticles with the size <14 nm, confirming the importance of the size-parameter. The heating ability of the best performing Pd/Fe-oxide-21 was calculated to be sufficient to ablate tumors with a radius ±4 and 12 mm using 10 and 1 mg/mL nanoparticle concentration, respectively. Conclusions: Nanoparticles consisting of non-magnetic palladium-core and magnetic iron oxide shell are suitable for magnetic hyperthermia/thermal ablation under clinically safe conditions of 346 kHz and 19.1 mT, with minimal eddy current effects in combination with maximum SLP.

Radionuclide therapy employing alpha emitters holds great potential for personalized cancer treatment. However, certain challenges remain when designing alpha radiopharmaceuticals, including the lack of stability of used radioconjugates due to nuclear decay events. In this work, ultrasmall silver telluride nanoparticles with a core diameter of 2.1 nm were prepared and radiolabeled with lead-212 using a chelator-free method with a radiolabeling efficiency of 75%. The results from the in vitro radiochemical stability assay indicated a very high retention of bismuth-212 despite the internal conversion effects originating from the decay of 212Pb. To further evaluate the potential of the nanoparticles, they were radiolabeled with indium-111, and their cell uptake and subcellular distribution were determined in 2D U87 cells, showing accumulation in the nucleus. Although not intentional, it was observed that the indium-111-radiolabeled nanoparticles induced efficient tumor cell killing, which was attributed to the Auger electrons emitted by indium-111. Combining the results obtained in this work with other favorable properties such as fast renal clearance and the possibility to attach targeting vectors on the surface of the nanoparticles, all well-known from the literature, these ultra-small silver telluride nanoparticles provide exciting opportunities for the design of theragnostic radiopharmaceuticals.

The relatively high linear energy transfer of Auger electrons, which can cause clustered DNA damage and hence efficient cell death, makes Auger emitters excellent candidates for attacking metastasized tumors. Moreover, gammas or positrons are usually emitted along with the Auger electrons, providing the possibility of theragnostic applications. Despite the promising properties of Auger electrons, only a few radiopharmaceuticals employing Auger emitters have been developed so far. This is most likely explained by the short ranges of these electrons, requiring the delivery of the Auger emitters to crucial cell parts such as the cell nucleus. In this work, we combined the Auger emitter ¹²⁵I and ultrasmall gold nanoparticles to prepare a novel radiopharmaceutical. The ¹²⁵I labeled gold nanoparticles were shown to accumulate at the cell nucleus, leading to a high tumor-killing efficiency in both 2D and 3D tumor cell models. The results from this work indicate that ultrasmall nanoparticles, which passively accumulate at the cell nucleus, have the potential to be applied in targeted radionuclide therapy. Even better tumor-killing efficiency can be expected if tumor-targeting moieties are conjugated to the nanoparticles.

While hyperthermia has been shown to induce a variety of cytotoxic and sensitizing effects on cancer tissues, the thermal dose–effect relationship is still not well quantified, and it is still unclear how it can be optimally combined with other treatment modalities. Additionally, it is speculated that different methods of applying hyperthermia, such as water bath heating or electromagnetic energy, may have an effect on the resulting biological mechanisms involved in cell death or in sensitizing tumor cells to other oncological treatments. In order to further quantify and characterize hyperthermia treatments on a cellular level, in vitro experiments shifted towards the use of 3D cell spheroids. These are in fact considered a more representative model of the cell environment when compared to 2D cell cultures. In order to perform radiofrequency (RF)-induced heating in vitro, we have recently developed a dedicated electromagnetic field applicator. In this study, using this applicator, we designed and validated an experimental setup which can heat 3D cell spheroids in a conical polypropylene vial, thus providing a reliable instrument for investigating hyperthermia effects at the cellular scale.

Background: The radionuclide Ga-68 is commonly used in nuclear medicine, specifically in positron emission tomography (PET). Recently, the interest in producing Ga-68 by cyclotron irradiation of [⁶⁸Zn]Zn nitrate liquid targets is increasing. However, current purification methods of Ga-68 from the target solution consist of multi-step procedures, thus, leading to a significant loss of activity through natural decay. Additionally, several processing steps are needed to recycle the costly, enriched target material. Results: To eventually allow switching from batch to continuous production, conventional batch extraction and membrane-based microfluidic extraction were compared. In both approaches, Ga-68 was extracted using N-benzoyl-N-phenylhydroxylamine in chloroform as the organic extracting phase. Extraction efficiencies of up to 99.5% ± 0.6% were achieved within 10 min, using the batch approach. Back-extraction of Ga-68 into 2 M HCl was accomplished within 1 min with efficiencies of up to 94.5% ± 0.6%. Membrane-based microfluidic extraction achieved 99.2% ± 0.3% extraction efficiency and 95.8% ± 0.8% back-extraction efficiency into 6 M HCl. When executed on a solution irradiated with a 13 MeV cyclotron at TRIUMF, Canada, comparable efficiencies of 97.0% ± 0.4% were achieved. Zn contamination in the back-extracted Ga-68 solution was found to be below 3 ppm. Conclusions: Microfluidic solvent extraction is a promising method in the production of Ga-68 achieving high efficiencies in a short amount of time, potentially allowing for direct target recycling. Graphical Abstract: [Figure not available: see fulltext.].

Two porphyrinic metal-organic frameworks (PCN-222 and PCN-224) were prepared and their potential as molybdenum adsorbents for the ⁹⁹Mo/^99mTc generator was explored. The molybdenum adsorption properties of the two adsorbents, including adsorption kinetics and equilibrium isotherms, were evaluated at different molybdenum concentrations and pH. The maximum adsorption capacity of PCN-222 and PCN-224 was evaluated to be 525 mg g⁻¹ and 455 mg g⁻¹, respectively. The possible adsorption mechanism was investigated by X-ray Photoelectron Spectra and Fourier-Transform Infrared Spectroscopy. The results demonstrated that molybdenum species were adsorbed on the two MOFs through electrostatic attraction and hydrogen bonds. In the case of PCN-222, the Mo-O-Zr coordination interaction also played an important role. Additionally, the elution performance of two ⁹⁹Mo/^99mTc generators developed by using PCN-222 and PCN-224 as adsorbents was measured to assess possible clinical applications. The PCN-222-based ⁹⁹Mo/^99mTc generator exhibited better elution performance and showed that around 56% of ^99mTc could be obtained without zirconium breakthrough when relatively high pH solutions were used (pH = 9.6).

Combination of therapies is a common strategy in cancer treatment. Such combined therapies only have merit provided that there is superior therapeutic outcome with fewer side effects, compared to single therapies. Here, this work explores the possibility to combine chemotherapy with radionuclide therapy using polymeric micelles as a delivery vehicle. For this purpose, this work prepares poly(ε-caprolactone-b-ethylene oxide) (PCL-PEO) micelles and load them simultaneously with paclitaxel (PTX) and ¹⁷⁷Lu(III). This work chooses a 3D tumor spheroid composed of glioblastoma cells (U87) to evaluate the combined treatment. The diffusion of the micelles in the spheroid is investigated by confocal laser scanning microscopy (CLSM) and light-sheet fluorescence microscopy (LSFM). The results show that the micelles are able to penetrate deep into the spheroid within 24 h of incubation and mainly accumulated around or in the lysosomes once in the cell. Subsequently, this work evaluates the cell killing efficiency of the single treatments (PTX or ¹⁷⁷Lu(III)) versus combined treatment (PTX + ¹⁷⁷Lu(III)) by measuring the growth of the spheroids as well as by performing a cell-viability assay. The results indicate that the combined therapy achieves a superior therapeutic outcome with better cell growth inhibition and cell killing efficiency compared to the single treatments.