Federica Simonelli

Radiolabelling of engineered nanoparticles for in vitro and in vivo tracing applications using cyclotron accelerators

We present in this article an outline of some cyclotron-based irradiation techniques that can be used to directly radiolabel industrially manufactured nanoparticles, as well as two techniques for synthesis of labelled nanoparticles using cyclotron-generated radioactive precursor materials. These radiolabelled nanoparticles are suitable for a range of different in vitro and in vivo tracing studies of relevance to the field of nanotoxicology. A basic overview is given of the relevant physics of nuclear reactions regarding both ion-beam and neutron production of radioisotopes. The various issues that determine the practicality and usefulness of the different methods are discussed, including radioisotope yield, nuclear reaction kinetics, radiation and thermal damage, and radiolabel stability. Experimental details are presented regarding several techniques applied in our laboratories, including direct light-ion activation of dry nanoparticle samples, neutron activation of nanoparticles and suspensions using an ion-beam driven activator, spark-ignition generation of nanoparticle aerosols using activated electrode materials, and radiochemical synthesis of nanoparticles using cyclotron-produced isotopes. The application of these techniques is illustrated through short descriptions of some selected results thus far achieved. It is shown that these cyclotron-based methods offer a very useful range of options for nanoparticle radiolabelling despite some experimental difficulties associated with their application. For direct nanoparticle radiolabelling, if care is taken in choosing the experimental conditions applied, useful activity levels can be achieved in a wide range of nanoparticle types, without causing substantial thermal or radiation damage to the nanoparticle structure. Nanoparticle synthesis using radioactive precursors presents a different set of issues and offers a complementary and equally valid approach when laboratory generation of the nanoparticles is acceptable for the proposed studies, and where an appropriate radiolabel can be incorporated into the nanoparticles during synthesis.

Excitation functions and yields for cyclotron production of radiorhenium via nat W(p,ߙxn)181-186gRe nuclear reactions and tests on the production of 186gRe using enriched 186W

Abstract Excitation functions and thin-target yields for the 181-186gRe radionuclides have been measured by the stacked-foil activation technique on tungsten foils of natural isotopic composition for different proton energies up to 22.0 MeV. A further check on the cross sections was done by irradiation of thick-targets and comparing the irradiated thick-target yields with those calculated by analytical integration from the thin-target yields. The production of 186gRe was also studied by the irradiation of thick-target of enriched 186W with a 13.6±0.2 MeV proton beam. The results for 186W(p,ߙn)186gRe were compared also to those calculated by the EMPIRE II code (version 2.19), due to 186gRe extensive applications in nuclear medicine for metabolic radiotherapy of tumours. It was found that the maximum percentage of 186gRe by irradiation of natural tungsten is about 20% only, which confirms the conclusion that high radionuclidic purity and specific activity of 186gRe necessitate the use of highly enriched 186W target.

A quantitative in vitro approach to study the intracellular fate of gold nanoparticles: from synthesis to cytotoxicity

Abstract Due to their physico-chemical characteristics, gold nanoparticles (AuNPs) seem to be suitable for biomedical and therapeutic applications even if conflicting data on their toxicological profiles are present in literature. In order to better understand if AuNPs could be safe we must consider different biological endpoints such as cytotoxicity, genotoxicity, inflammation and biopersistence. Starting from these considerations, one of the first issues to be assessed is to better understand if AuNPs can be internalized by cells. In this work, we propose a methodological approach to radioactivate AuNPs by neutron activation and the quantification of their internalization by two in vitro cell systems such as MDCK and HepG2 after 24 h of exposure. Despite a dose-dependent internalization, no evidence of cytotoxicity, determined by two different standard in vitro methods such as Neutral Red Uptake and Colony Forming Efficiency, was observed.

Cyclotron production of44Sc for clinical application

Abstract 44Sc is a promising β+-emitter for molecular imaging with intermediate half-life of 4 h. Due to the chemical similarity of Sc3+ to the Lu3+ and Y3+ cations, 44Sc-DOTA bioconjugates are expected to demonstrate similar properties in vivo as the 177Lu- and 90Y-bioconjugates, what is important in planning the radionuclide therapy. 44Sc can be obtained from the 44Ti/44Sc generator. An alternative method for 44Sc production can be the irradiation of 44Ca target at small cyclotrons. The aim of our work was to optimize the parameters of 44CaCO3 irradiation and to develop a simple procedure for 44Sc separation from the calcium target. For optimization study, 44CaCO3 targets were irradiated by protons in the energy range of 5.6–17.5 MeV with 9 MeV being found to be the best energy for 44Ca irradiations. A simple and fast separation procedure of 44Sc from calcium target was developed using chelating resin Chelex 100. DOTATATE conjugate was successfully radiolabelled with high yield at elevated temperature using the produced 44Sc. While 44CaCO3 is relatively expensive, the cost of 44Sc-DOTATATE production can be reduced by target recovery. Due to low proton energy required to produce GBq activity level of 44Sc, the availability of 44Sc radioisotope could be enhanced to open new opportunities for applications in medical imaging.

Cyclotron Production of Radioactive

Nowadays, a wide variety of nanoparticles (NPs) are applied in different fields such as medical science and industry. Due to their large commercial volume, the OECD Working Party on Manufactured Nanomaterials (NMs) has proposed to study a set of 14 nanomaterials, one of which being cerium oxide (CeO2). In particular, CeO2 based NPs are widely used in automotive industry, healthcare, and cosmetics. In this paper, we propose a method for the production of radioactive CeO2 NPs. We demonstrate that they maintain the same physicochemical characteristics as the “cold” ones in terms of size distribution and Zeta potential; we develop a new protocol to assess their cellular interaction in immortalized mouse fibroblast cell line Balb/3T3, a model for the study of basal cytotoxicity and carcinogenic potential induced by chemicals and in the present case by NPs. Experimental result of this work, which shows a quasi-linear concentration-uptake response of cells, can be useful as a reference dose-uptake curve for explaining effects following biological uptake after exposure to CeO2 NPs.

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BACKGROUND The pulmonary route is very promising for drug delivery by inhalation. In this regard, nanoparticulate drug delivery systems are discussed, and one very promising nano carrier example is gold nanoparticles (Au NP). Directly after their deposition, inhaled Au NP come into contact with pulmonary surfactant protein D (SP-D). SP-D can agglomerate Au NP in vitro, and this may influence the clearance as well as the systemic translocation in vivo. The aim of the present study was to investigate the clearance and translocation of Au NP at a very early time point after inhalation, as well as the influence of SP-D. METHODS Aerosolized 20-nm radioactively labeled Au NP were inhaled by healthy adult female mice. One group of mice received dissolved 10 μg of SP-D by intratracheal instillation prior to the Au NP inhalation. After a 2-hr Au NP inhalation period, the mice were killed immediately, and the clearance and translocation to the blood stream were investigated. RESULTS The highest amount of Au NP was associated with the lung tissue. In the bronchoalveolar lavage fluid (BALF), more Au NP remained free compared with the amount associated with the BALF cells. The amount of Au NP cleared by the mucociliary escalator was low, probably because of this very early time point. Instillation of SP-D prior to Au NP inhalation had no statistically significant effect on the biodistribution of the Au NP. CONCLUSION Our data show that inhaled Au NP are retained in the mouse lungs and are translocated after a short time, and that SP-D has only a minor effect on Au NP translocation and clearance at a very early time point.

Nanoparticles and Their Application for In Vitro Uptake Studies

(230)U/(226)Th is a promising novel alpha-emitter system for application in targeted alpha therapy of cancer. The therapeutic nuclides can be produced by proton irradiation of natural (232)Th according to the reaction (232)Th(p,3n)(230)Pa, followed by subsequent beta decay of (230)Pa to (230)U. In this study, the experimental excitation function for the (232)Th(p,3n)(230)Pa reaction up to 34 MeV proton energy has been measured using the stacked-foil technique. The proton energies in the various foils were calculated with the SRIM 2003 code and gamma-ray spectrometry was used to measure the activities of the various radioisotopes produced. The measured cross-sections are in good agreement with selected literature values and with model calculations using the EMPIRE II code. The reaction (232)Th(p,3n)(230)Pa allows the production of carrier-free (230)U in clinically relevant levels.

Biodistribution of Inhaled Gold Nanoparticles in Mice and the Influence of Surfactant Protein D

A novel production method for n.c.a. 64Cu based on deuteron irradiation of 64Zn is presented. The production takes place through the 64Zn(d, 2p) 64Cu reaction using a deuteron beam of 19.5 MeV energy on highly enriched 64Zn disks. An average yield over three irradiations of 31 MBq/μA h (850 μCi/μA h) and saturation yield of 575 MBq/μA (15.5 mCi/μA) at the end of the beam (EOB) was measured by γ-ray spectrometry. Two of the three runs, of low irradiation charge, were used for radiochemistry. The copper isotopes were separated from other radionuclidic impurities by the combination of cation and anion exchange chromatography. An average radiochemical yield of 90% was estimated for the two runs performed in this study, and the specific activity as determined using flame atomic absorption spectrometry was about 4 MBq/μg, 2 hours after EOB. An extrapolation of the present results to production conditions (50 μA, 10 h) indicates approximately 8 GBq/μg (220 mCi/μg) of specific activity. The overall uncertainty in these values is estimated to 15%.

Cross-sections of the reaction 232Th(p,3n)230Pa for production of 230U for targeted alpha therapy.

Abstract A method for preparation of 67Cu based on deuteron irradiation of enriched 70Zn is presented. Cross-sections for 67Cu formation were determined by the stacked foil technique for deuteron energies in the range from 10 to 20 MeV for the first time. Irradiations of 70Zn foils were followed by radiochemical separation of 67Cu from the target material and co-produced radionuclidic impurities. The maximum cross-section value of 25.5 ± 2.2 mb was reached at 19 MeV. The integral yield in the energy window of 20 → 10 MeV on 95% enriched 70Zn is estimated at 4.2 MBq/μA h (110 μCi/μA h) or 375 MBq/μA (10 mCi/μA) at saturation.

A Novel Method for n.c.a. 64Cu Production by the 64Zn(d,2p)64Cu Reaction and Dual Ion-exchange Column Chromatography

Proton-induced nuclear reactions for generation of (99)Mo and (99m)Tc radionuclides were investigated using the stacked-foil activation technique on 99.05% enriched (100)Mo targets at energies up to Ep=21MeV. Excitation functions of the reactions (100)Mo(p,x)(99)Mo and (100)Mo(p,2n)(99m)Tc have been measured.