Despite their advantageous chemical properties for nuclear imaging, radioactive sodium-22 ( 22 Na) tracers have been excluded for biomedical applications because of their extremely long lifetime. In the current study, we proposed, for the first time, the use of 22 Na radiotracers for pre-clinical applications by efficiently loading with silica nanoparticles (SiNPs) and thus offering a new life for this radiotracer. Crown-ether-conjugated SiNPs (300 nm; −0.18±0.1 mV) were successfully loaded with 22 Na with a loading efficacy of 98.1%±1.4%. Noninvasive positron emission tomography imaging revealed a transient accumulation of 22 Na-loaded SiNPs in the liver and to a lower extent in the spleen, kidneys, and lung. However, the signal gradually decreased in a time-dependent manner to become not detectable starting from 2 weeks postinjection. These observations were confirmed ex vivo by quantifying 22 Na radioactivity using γ-counter and silicon content using inductively coupled plasma-mass spectrometry in the blood and the different organs of interest. Quantification of Si content in the urine and feces revealed that SiNPs accumulated in the organs were cleared from the body within a period of 2 weeks and completely in 1 month. Biocompatibility evaluations performed during the 1-month follow-up study to assess the possibility of synthesized nanocarriers to induce oxidative stress or DNA damage confirmed their safety for pre-clinical applications. 22 Na-loaded nanocarriers can thus provide an innovative diagnostic agent allowing ultra-sensitive positron emission tomography imaging. On the other hand, with its long lifetime, onsite generators or cyclotrons will not be required as 22 Na can be easily stored in the nuclear medicine department and be used on-demand.

In this work, we investigate the potential of exploiting TiO2 thin films as sensing layers on silicon micro-electromechanical systems for the detection of gamma radiations. All samples are exposed to gamma rays produced by 60Co, with different doses ranging from 0 kGy to 40 kGy. Properties of silicon coated with a 200-nm-thick layer of TiO2 grown at 200 °C by atomic layer deposition are studied before and after its gamma irradiation using x-ray diffraction (XRD), scanning electron microscopy, and spectroscopic ellipsometry. Atomic force microscopy (AFM) is carried out on functionalized microcantilevers to measure the resonance frequency shift (Δf 0) resulting from irradiation of the TiO2 thin film. XRD results show a change in the films from a mixture of rutile and anatase phases to an anatase phase upon irradiation. Spectroscopic ellipsometry results show a change with a fixed pattern in the film thickness, roughness, void, and optical constants with different irradiation doses. This pattern appears as Δf 0 in AFM, where the response of sensors to doses between 0 kGy and 20 kGy was linear. The values of Δf 0 are convenient to control parameters for the proposed dosimeter, which is characterized by the reproducibility and sensitivity of measurements. The maximum detectable linear effect of the proposed dosimeter was found at a dose of 20 kGy. This makes a 200-nm thin layer of TiO2 coated on a microcantilever surface, a possible candidate for dosimetry for the range lower than 20 kGy applications, such as in personal dosimeters.

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This study generally relates to nuclear sensors and specifically to detecting nuclear and electromagnetic radiation using an ultrasensitive quartz tuning fork (QTF) sensor. We aim to detect low doses of gamma radiation with fast response time using QTF. Three different types of QTFs (uncoated and gold coated) were used in this study in order to investigate their sensitivity to gamma radiations. Our results show that a thick gold coating on QTF can enhance the quality factor and increase the resonance frequency from 32.7 to 32.9 kHz as compared to uncoated QTF. The results also show that increasing the surface area of the gold coating on the QTF can significantly enhance the sensitivity of the QTF to radiation. We investigated the properties of gold-coated and uncoated QTFs before and after irradiation by scanning electron microscopy. We further investigated the optical properties of SiO2 wafers (quartz) by spectroscopic ellipsometry (SE). The SE studies revealed that even a small change in the microstructure of the material caused by gamma radiation would have an impact on mechanical properties of QTF, resulting in a shift in resonance frequency. Overall, the results of the experiments demonstrated the feasibility of using QTF sensors as an easy to use, low-cost, and sensitive radiation detector.

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