Implant-associated infections remain a major challenge in orthopaedic surgery, motivating the development of antimicrobial implant surfaces that do not compromise bone regeneration. As osteoclasts are crucial for bone remodelling and implant integration, their response to antimi- crobial surface modifications must be carefully evaluated. This thesis investigated the effects of silver nanoparticles (AgNPs) incorporated into plasma electrolytic oxidation (PEO) treated Ti6Al4V implant surfaces on osteoclastogenesis under direct and indirect in vitro exposure con- ditions. Human CD14+ monocytes were cultured directly on the implant surfaces to evaluate surface-mediated effects, and indirectly in Transwell-based mono- and coculture models to as- sess the influence of released ions and human mesenchymal stem cell (hMSC)-derived signals on osteoclastogenesis. Surface characterisation confirmed successful PEO treatment and AgNP incorporation without alteration of surface morphology. Direct contact with AgNP-containing surfaces reduced the number of viable adherent cells, while osteoclast differentiation markers re- mained detectable in surviving cells. In contrast, indirect exposure to implant-derived ionic cues did not impair osteoclast formation. These findings highlight the exposure-dependent effects of AgNP-incorporated PEO surfaces and support their potential for antimicrobial implant design within a biologically tolerable range. ... Read more

Periprosthetic joint infections by antibiotic-resistant biofilm-forming pathogenic bacteria such as Staphy-lococcus aureus are a growing concern in the field of arthroplasty. They are difficult to treat and can lead to implant revision surgery, health complications, and in some cases death. An established method in clinical practice for delivering antibiotics directly to the site of surgery is the use of antibiotic-loaded polymethyl methacrylate (PMMA), a synthetic polymer used to integrate joint implants into bone tissue. With rising rates of antibiotic resistance, researchers are looking for alternative treatments for bacterial infections and one of the possible candidates is targeted alpha therapy (TAT). Ra-223 is one such alpha emitter which is already being used in a clinical setting under the name Xofigo®to treat cancer. With the ability of PMMA to be loaded with pharmaceuticals, it may be worthwhile to investigate whether radioistopes such as Ra-223 can also be loaded and released from the polymer. In this thesis, the potential use of PMMA as a radioisotope delivery vehicle is investigated, as well as the bactericidal capacity of Ra-223 against S. aureus are investigated.
To achieve this, PMMA was loaded separately with two different radioisotopes, Ga-68 and Ra-223. The loading was done with and without the presence of a chelator. The release of the isotopes from PMMA was measured over time. Growth of S. aureus cultures was measured under different activities of Ra-223 and growth curves were constructed. The uptake of Ra-223 by the bacteria was also measured.
A minimum of 50% Ga-68 was found to be released when freely added to PMMA. This was due to the insolubility of the Ga-68 eluate in PMMA, causing the isotope to be concentrated in a single spot. However, the addition of a chelator significantly dampened the release to maximum of 3%, since Ga-68 was homogeneously dispersed throughout the PMMA volume. Ra-223 was shown to have a similar release when added freely to PMMA (47%), but the chelator used was shown not to extract any Ra-223 to the PMMA and therefore no release was observed. There was no measurable bactericidal effect of Ra-223 on S. aureus for the activities used in the experiments. It was found that 8±5% of the total amount of Ra-223 was taken up by the bacteria after 18 h of incubation.
Although PMMA seems to exhibit some radioisotope release, further experiments need to be carried out to determine if these amounts can evoke a bactericidal effect. The percentage of Ra-223 taken up by S. aureus shows that the isotope has some promise as a potential bactericide against it, but experiments with higher activities need to be carried out. Furthermore, future experiments are needed to determine the internalization of Ra-223 by S. aureus. ... Read more

The radionuclide technetium-99m (99𝑚Tc) is utilized in 80-85% of in-vivo nuclear medicine diagnostics due to its ideal physical and chemical properties, including a short half-life, gamma emission suitable for imaging, and versatile chemistry. Its production relies on molybdenum-99 (99Mo), traditionally generated through uranium fission. However, the transition to low-enriched uranium (LEU) targets and growing demand for 99𝑚Tc have driven the search for alternative production methods and materials. This study investigates the potential of molybdenum silicide (MoSi2) materials as targets for neutron-activated 99Mo production and as generators for 99𝑚Tc extraction. Three synthesis methods were explored to produce nanoscale molybdenum silicides. A sol-gel carbothermic reduction method failed to produce MoSi2, yielding elemental molybdenum, molybdenum dioxide, and molybdenum carbide due to oxygen contamination. The sol-gel preoxidation method successfully coated commercial MoSi2 with an amorphous silica layer, enhancing the material’s stability. The magnesiothermic reduction method successfully produced an oxide mixture intermediate (SiO2/MoO3) with nanosphere structures, initially containing 0.57 wt% molybdenum. The molybdenum content was later increased to 23.96 wt%. However, synthesis of the Si/MoSi2 nanocomposites from this intermediate was not completed due to time constraints. The chemical stability, extraction and retention behavior of commercial and silica-coated MoSi2 were evaluated in MilliQ and methyl ethyl ketone (MEK). The silica coating reduced molybdenum leaching and exhibited selective 99𝑚Tc extraction. Retention studies highlighted the significant role of solvent interactions in governing radionuclide adsorption. In MEK, the silica-coated material exhibited lower 99𝑚Tc retention, likely due to reduced adsorption sites caused by solvent interactions with silanol groups, while 99Mo retention could not be evaluated due to insufficient extraction data. The results demonstrate the potential of silica-coated MoSi2 in 99Mo/99𝑚Tc generator applications. However, further work is needed to optimize synthesis, increase surface area and evaluate long-term performance under irradiation. This could pave the way for sustainable and efficient isotope production systems. ... Read more

¹⁶¹Tb is considered a promising alternative to ¹⁷⁷Lu in the treatment of neuroendocrine tumors and prostate cancer. It is produced via neutron irradiation of ¹⁶⁰Gd targets and its subsequent separation from said targets. Current separation methods have limitations so a fast removal method of the Gd bulk is desired. Such a method is developed in this research using solvent extraction techniques. Three extractants were investigated, the one with the highest potential, DEHPA, was used to optimize the extraction. This yielded a Tb extraction efficiency of 98.6 ± 0.2 % and a Gd extraction efficiency of 85.7 ± 5.5 % followed by a Tb back-extraction efficiency of 98.2 ± 0.1 % and a Gd back-extraction efficiency of more than 98.2 ± 0.1 %. The Tb/Gd separation was increased by adding the reverse size selective chelator MACROPA to the aqueous phase to preferentially complex Gd in the aqueous phase. This yielded a Tb and Gd extraction efficiency of 95.0 ± 0.2 % and 53.1 ± 3.0 % respectively. The ratio between total EEs of Tb and Gd after three subsequent extractions was approximately 10 demonstrating the potential of using sequential extractions to remove a bulk of Gd from Tb. The procedure of doing consecutive extractions must however be further optimized as nearly 80% of Tb was not extracted. Finally, it was shown that the resulting solution after bulk Gd removal can still be further purified using an ion exchange column. In future research, it is highly advised to investigate the recycling of Gd and MACROPA from the aqueous phase after extraction to allow for further irradiation of the Gd and re-usability of the MACROPA. ... Read more

Technetium-99m (^99mTc) is a critical isotope in nuclear medicine, used for diagnostic imaging. It is conventionally produced in a aluminum oxide ⁹⁹Mo/^99mTc generator that runs on molybdenum-99 (⁹⁹Mo) produced by fission of uranium-235. This fission-based production method faces several challenges. To address these challenges, alternative production pathways are being explored. Neutron irradiation of enriched ⁹⁸Mo nanomaterials and proton bombardement of enriched ¹⁰⁰Mo nanomaterials are two of the possible options. Within this research, the pathway of ⁹⁸Mo neutron capture will be the focus.
Developing a novel circular low specific activity 99Mo/99mTc generator that can run on these materials requires research to be done into the potential materials. The materials must meet two qualifying conditions: they should have a high surface-to-volume ratio, and show high radionuclide extraction potentials. This is an exploratory study to determine if molybdenum disulfides can be synthesized to meet those conditions.
Multiple synthesis methods of MoS₂ nanostructures were explored, and insights were given on their morphological and compositional characteristics. Of the six synthesized materials, four were MoS₂ nanospheres, one was MoS₂ microcubes and one was unable to be characterized
due to unsuccessful separation of the product. Two of the products were further evaluated on their stability and surface area. Stability tests in milliQ were done under two conditions: five consecutive cycle washes and five time-based washing cycles. Both materials exhibited lower Mo breakthrough during the consecutive washes than during the time-based wash cycles. The most compelling results were the downward trend that the Mo breakthrough data shows for the consecutive washes and the high breakthrough percentage in the 24 h soak for one of the samples (namely, 1.2 ± 0.28%) . Furthermore, the same two materials were tested on irradiation performance. Radionuclide extractions were made in milliQ, and extraction yields were calculated for ⁹⁹Mo. ... Read more

Calcium is the most abundant mineral in the human body and is essential for building and maintaining bones and teeth. Only 20-30% of the calcium in milk can be absorbed by the human body. 90% of the insoluble calcium in milk is located in the casein micelles, and 40% of this calcium is hard to exchange.
It is important to understand how this non-exchangeable calcium behaves and whether there are ways of making it exchangeable.
In this study, the hard-to-exchange (HTE) calcium in the casein micelles of bovine skimmed milk was studied. In order to investigate this, a protocol for the preparation of artificial casein micelles was established. The hydrodynamic radius and the hydration of the casein micelles were measured to see if the artificial casein micelles could be compared to the casein micelles from bovine skimmed milk. Subsequently, 45Ca was used to track the exchange of calcium in the three different fractions of milk and artificial casein micelles: casein micelles, serum proteins, and soluble phase. (Ultra)centrifugation was used to separate the fractions.
Characterisation of bovine skimmed milk and artificial casein micelles was carried out first. The hydrodynamic radius of the casein micelles in both types of milk was determined and it was concluded that the hydrodynamic radius of both types of milk was comparable to each other. Furthermore, the hydration of casein micelles was investigated. A difference was measured between the hydration of both casein micelles. This can be explained by a small deviation in casein and fat content between the two types of milk.
In order to draw conclusions about the suitability of using artificial casein micelles to model casein micelles naturally present in milk, the protocol needs to be adapted by adjusting the casein content and removing the fat from both types of casein micelles. It is also necessary to investigate the mineral content of both types of milk.
It was found that almost half (48.8 ± 0.6%) of the 45Ca added to bovine skimmed milk was located in the supernatant, while the remaining 54.2 ± 0.6% was distributed within the casein micelles. When this distribution is compared to that of artificial casein micelles, it can be seen that the %45Ca in the artificial casein micelles is much lower than in the bovine skimmed milk casein micelles. This is because of the fact that artificial casein micelles contain a lower content of casein aggregates cross-linked with colloidal calcium phosphate (CCP) in comparison with bovine skimmed casein micelles.
When 45Ca was added after the preparation of artificial casein micelles, the HTE calcium was found to be 54.5 ± 2.6%. However, when the 45Ca was added during the preparation of artificial casein micelles and measured after 0 hours, the HTE calcium was 63.1 ± 2.0% and after 24 hours it was determined to be 59.6 ± 3.4%. These values were not in agreement with the values from Zhang et al. [1].
Overall, this project contributed to a better understanding of the hard-to-exchange calcium in milk using artificial casein micelles and 45Ca. It shows that further research needs to be carried out to determine whether artificial milk can be used as a model for bovine skimmed milk and to determine the HTE calcium in artificial casein micelles. ... Read more

Holmium-166 is a promising radionuclide for therapeutic and imaging applications due to its advantageous decay characteristics. However, these applications require or would benefit from a higher specific activity of ¹⁶⁶Ho than that obtained via a ¹⁶⁵Ho(n,γ)¹⁶⁶Ho reaction by irradiating a pure ¹⁶⁵Ho target. The specific activity is limited, because only a minor fraction of the ¹⁶⁵Ho target nuclides is converted into ¹⁶⁶Ho during irradiation and these isotopes are inseparable using conventional chemical methods, since they are of the same element. The Szilard-Chalmers effect facilitates this separation by changing the chemical state of the produced radionuclide due to the recoil induced by neutron absorption. Nevertheless, currently applied target materials, mainly ligands, are unsuitable for commercial scale production with sufficient yield and specific activity, because of: radiolysis, isotopic interchange and recombination. It is proposed that these processes can be significantly reduced by exploiting zeolites, which are materials with interconnected cavities, to bind ¹⁶⁵Ho target nuclides in the closed cages prior to irradiation. The concept behind is, that upon recoil the ¹⁶⁶Ho nuclides relocate to the open cages, from which they are extracted after irradiation, while the ¹⁶⁵Ho target nuclides remain locked in the closed cages. This results in an increased specific activity. Therefore, the aim of this thesis is to examine the increase in the specific activity of ¹⁶⁶Ho produced via a (n,γ) reaction by applying the Szilard-Chalmers effect using zeolite A.

A procedure to achieve the optimal loading of holmium into the open cages (18.3 wt% Ho) and closed cages (93.3% of total holmium) of zeolite A was investigated, as well as the efficiency of its extraction from the open cages (between 39 and 55%). The obtained specific activity and yield were analysed upon irradiation of these zeolite A samples. Irradiating zeolite A with ¹⁶⁵Ho exclusively in the open cages resulted in only a slight increase of the specific activity (maximal 3.3 GBq/g), but a relatively good yield (maximal 53%). In contrast, irradiation of zeolite A with ¹⁶⁵Ho loaded in both the closed and the open cages, resulted in a considerably lower yield (maximal 14.4%), but a substantially increased specific activity (maximal 7.3 GBq/g), which is a factor 5.2 higher than without the Szilard-Chalmers effect. 
Nevertheless, further improvement should be considered as a higher specific activity is key to successful radionuclide therapy. This could potentially be achieved by increasing the extraction efficiency by exploring other types of zeolites, in search of more suitable functional characteristics. ... Read more

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Cancer is often treated by radiation therapy. There are three types of radiation therapy: external beam therapy, brachytherapy and radionuclide therapy. A downside to radiation therapy is its damaging effect on healthy tissue. A different type of treatment is photodynamic therapy. In PDT photo-active substances are being used to generate reactive oxygen species under irradiation. These ROS are a group of radicals which can cause damage to the DNA and in some cases cause necrotic or apoptotic cell death. By combining radiotherapy and PDT, the effectiveness of the treatment can be enhanced. Among different ROS, singlet oxygen is the most effective in causing DNA damage. As the nanoparticle titaniumdioxide and the photo-active molecule chlorin e6 can generate ROS under ionizing radiation, it is very attractive to look further into how much singlet oxygen they can generate. This report will focus on the singlet oxygen generating abilities of the photo-active substances TiO2 and Ce6 under the irradiation of lutetium-177 and iodine-125. The relative amounts of generated singlet oxygen are measured using a probe called Singlet Oxygen Sensor Green and fluorescence spectroscopy. The experiments using 177Lu, did not show a lot of promise as a decrease in fluorescence intensity was seen in the radioactive samples. It is possible that 177Lu precipitates despite of its chelation with DTPA and the beta-minus particles might have destroyed the SOSG probe. When comparing the Ce6 samples with the TiO2 samples, the TiO2 samples show much higher intensities. A possible explanation for this result might be the fact that 177Lu destroys both the SOSG and Ce6, whereas TiO2 is not an organic molecules and it thus not destroyed by 177Lu. The intensities of the Ce6 samples was higher than the control group. This suggests there is some positive influence of Ce6 on the generation of singlet oxygen under irradiation of 177Lu. The experiments using 125I showed promise as the control samples and Ce6 samples showed an increased intensity in the presence of 125I. This suggest that under irradiation of 125I more singlet oxygen is generated than without. The TiO2 samples show inconclusive results and thus no trend can be seen between the exposed and non-exposed samples. This is possible due to some TiO2 particles being present in the eluate. ... Read more

To ensure proper development, infants must receive the right amount of nutrients. Since their intake of minerals and trace elements in the first four months comes solely from mother milk or formula, valuable information about the uptake can derived by analyzing their excretion (in the form of feces or urine). Previous studies have used this approach but required convoluted collection of excretion before analysis.

This study investigates methods for non-invasive mineral uptake determination in babies, through measurement of minerals and trace elements in used diapers based on two analytical techniques, instrumental neutron activation analysis (INAA) and inductively coupled plasma optical emission spectroscopy (ICP-OES). This study compares the applicability of both techniques for different types of diapers. Furthermore, the representativeness of subsampling of diapers is investigated, and the elements that can be measured by the proposed methods are identified.

This study finds that Large Sample INAA (LSNAA) can be used to investigate used cloth diapers, assuming it is possible to measure cloth diapers individually. This method is able to measure potassium and probably sodium in urine, as well as potassium and potentially sodium, iron, and zinc in feces. The proposed method is as follows: The used diaper is dried and thereafter placed in the pot, with the empty space filled with cotton sheets. The samples are irradiated for 100 hours with a flux of 3.00 *1012 ± 0.02*1012 cm2s-1, followed by measuring the diapers after 2.5 and 19 days after irradiation. To determine the minerals in excretion, the minerals measured in the blank diaper are subtracted, which are determined by irradiating three blank diapers, with the same settings as the used diapers, and taking the average and standard deviation.

Furthermore, this study finds that ICP-OES can be used to measure potassium in disposable diapers containing urine. The proposed method is as follows: the area where the urine is located is dissolved using 6 mL nitric acid (65%) per 200 mg. The same area is dissolved three times for a blank diaper. The samples are filtered and diluted ± 8 times. Thereafter, the samples are measured using the ICP-OES device. To determine the minerals in urine, the measurements of the blank diaper are subtracted from the measurements of diaper with urine. Internal standards are used to compensate for differences between matrices. This approach assumes that differences between different sizes of diaper pieces are the result of matrix differences. The results from this study provide no conclusive evidence for the best dissolution method for a disposable diaper.

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Iron deficiency is considered the most significant nutritional deficiency worldwide, affecting billions of people. Iron deficiency leads to a higher prevalence of iron deficiency anaemia; a condition responsible for over 50,000 deaths annually. Since anaemia is considered a global health problem, various countermeasures have been implemented to battle this disease. One of these countermeasures is the supplementation of iron. Different iron compounds are employed for supplementation, including ferrous sulphate and ferrous fumarate. However, since only 15% of the supplemented iron is absorbed by the human body, the remaining 85% can cause various health-related issues. Due to heightened amounts of iron present in the duodenum, a disbalance in the human gut is induced, leading to e.g. excessive growth of Escherichia coli (E.coli).
This study investigates the influence of 3 and 30 µM iron supplementation of ferric chloride and ferric sulphate; radiolabelled with Fe-55. These results have been reported in the form of growth curves, and the remaining amount of Fe-55 in the growth medium has been used to estimate iron uptakeby E.coli. No significant differences were observed between 3 and 30 µM iron supplementation of both compounds, indicating that iron concentration may not be considered as the main limiting growth factor of E.coli. Therefore, further research is recommended where the medium is analysed for the presence of other nutrients. Additionally, adjustments in the growth environment are recommended, to determine which growth conditions influence E.coli the most. ... Read more

In the human body calcium is the most abundant mineral and is involved in a lot of vital processes. Calcium deficiency occurs when there is not enough calcium present in the bloodstream. In the Netherlands one in three women will face this problem in their lifetime. A major factor contributing to this problem is that the intake of calcium on average is below the recommended amount which is around 950 mg/day for adults in the Netherlands. Calcium deficiency when left unattended can lead to osteoporosis. Therefore it is important to consume enough calcium rich products or take calcium supplements. Milk is a good source of calcium and is considered a staple food. This makes bovine milk a good candidate for calcium fortification. Milk can be fortified by using calcium salts to increase the bioavailability the calcium present. In this thesis in vitro methods were used to study the effects of calcium salt fortification on the phase distribution of calcium in bovine skimmed milk under different pH conditions and by using the radioactive isotope 45Ca to track the exchange between the phase casein micelles, serum proteins and the soluble phase when fortifying the milk. For unfortified milk it was found that 36.0±0.9% was present in the soluble phase, 3.7±2.9% was present in the serum proteins phase and 60.3±3.0% in the casein micelles. Acidifying the milk to simulate the gastric environment resulted in an increase of the soluble phase from 55.1±2.7% to 97.0±3.3% which corresponds to a decrease in pH from pH 6 to pH 2. For the fortification of the milk, five calcium salts were selected for synthesis. The salts were calcium carbonate, tricalcium di-citrate, calcium gluconate, calcium lactate and tri-calcium phosphate. The fortification was performed with all of the synthesized salts except calcium lactate and tri-calcium phosphate. The starting material for the syntheses, calcium chloride, was also used for fortification. It was found that for the fortification of CaCO3 under gastric conditions a bioavailability of 100% could be achieved. However the acidic environment also resulted in coagulation of the milk and therefore the bioavailability could not be accurately assessed. Calcium gluconate had the only increase in bioavailability under normal conditions. In conclusion a better understanding of fortification with calcium salts was achieved and the influence of pH on the bioavailability of calcium in milk and the effects on the salt fortification. ... Read more

Radiotherapy is a vital component in the treatment of malignancies, with approximately 50 to 70% of cancer patients receiving it at some point. This therapy consists of irradiating the affected body part with an external beam of ionising radiation. A limitation of this technique is its damaging effect on healthy cells surrounding the tumour. Semiconducting nanoparticles could offer a solution to this, as these compounds can generate reactive oxygen species (ROS). ROS are a group of free radicals that are known to be able to damage DNA and potentially cause necrotic or apoptotic cell death. Using these metal nanoparticles could increase the radiation damage to malignant cells during radiotherapy, without raising the risk of cell death for the surrounding tissue. Especially TiO2 nanoparticles have been increasingly studied due to their ability to produce singlet oxygen, one of the most reactive ROS, while also having low toxicity and cost. However, many aspects of the ROS-formation remain unclear, including certain ROS production pathways. This report will therefore focus on the ability of TiO2 to produce specific ROS in response to ionising radiation, which will primarily be compared to the ROS formation through the radiolysis of water. The focus lies on the detection of singlet oxygen and hydrogen peroxide (H2O2 ) after irradiation by either a Co-60 gamma or a low energy X-ray source over a range of 5 to 40 Gy. Their concentrations are detected by fluorescence spectroscopy for singlet oxygen, and by UV-VIS spectroscopy for hydrogen peroxide. The results were promising for the use of TiO2 in radiotherapy, with both MilliQ water and TiO2 being able to produce singlet oxygen in increasing amounts over the entire researched irradiation range for both radiation sources; Moreover, TiO2 could produce a significantly larger amount of this ROS than the MilliQ water samples did. The hydrogen peroxide detection experiments were first conducted with ZnO instead of TiO2 . During these, the trends observed for the H2O2 concentration were similar to the ones obtained during the singlet oxygen experiments. The main difference was that the ZnO samples produced approximately the same amount of H2O2 as the MilliQ water samples for X-ray irradiation, instead of higher values. Lastly, the hydrogen peroxide concentration in both TiO2 and ZnO samples was measured after irradiation by Co-60. ZnO exhibited an upward trend in which the H2O2 molarity increased as the applied dose got higher. The detected H2O2 levels in the TiO2 samples were, on the other hand, relatively stagnant. This observation is likely attributed to a relatively high extent of either the degradation, conversion, or adsorption of this ROS at the surface of TiO2 ... Read more

Combining different treatment modalities has proven to improve patient outcome compared to applying single treatments. Consequently, mild hyperthermia (HT) and radiotherapy (RT) are combined to radiosensitize tumour cells by inhibiting DNA damage repair mechanisms. In this study, it was investigated if combining both treatment modalities shows an improved therapeutic effect on 3D tumour models made of FaDu cells. To this end, the spheroid size and cell viability were measured over time after treatment. It was also attempted to obtain further qualitative information of the effect on the spheroids using confocal microscopy. During experiments spheroids were formed of FaDu tumour cells, cells of a head-and-neck squamous cell carcinoma, using Matrigel®. These spheroids grew fast within the first 10 days of seeding up to a size of 550-600 𝜇m reliably. These spheroids were then exposed to both single HT and RT as well as combined HT and RT. Both single treatment modalities showed a decrease in cell growth and cell viability with increasing treatment dose. The thermal doses of 30 and 120 CEM43 and radiation doses of 2 and 6 Gy were chosen to be used in the combined treatment experiments. Combined treatment showed an improved effect on the cell growth and cell viability for most treatment groups, both for HT followed by RT and the other way around, with the determining factor seemingly being the thermal dose. The thermal dose of 120 CEM43 combined with 6 Gy of radiation dose showed the highest cell killing potential, with 9±2% of the cell viability remaining when using radiotherapy before hyperthermia and 18±3% when starting with HT before using RT. The most significant difference in effect due to the order in which RT and HT were administered was seen in the group treated with 2 Gy of radiation dose and 120 CEM43 of thermal dose. In this group RT preceding HT resulted in a cell viability of 13±2% on day 7 after treatment, whilst HT preceding RT resulted in a cell viability of 48±8%. Visual inspection of the spheroids showed an increased effect in the form of less growth, as well as flaking around the edges of the spheroids. Obtaining qualitative information on the effect that combined treatment had on spheroids using confocal microscopy was unsuccessful. Both using a live and dead cell staining kit, as well as PI staining proved ineffective in accurately visualizing the dead cells in spheroids. ... Read more

166Ho is a promising radionuclide for targeted radionuclide therapy, because of its beneficial decay characteristics and the possibility to track its dose delivery in a patient. However, a problem for the use of 166Ho in these treatments is its limited maximally produced specific activity in neutron irradiation of a pure 165Ho target, since the produced 166Ho is chemically inseparable from the 165Ho target. The Szilard-Chalmers method is known to be able to increase the achieved specific activity. It does so by irradiating the target isotope while it is incorporated in a compound. As the target isotope undergoes (n, γ) neutron capture it forms the product isotope and escapes the compound due to recoil from prompt gamma emissions. Then by separating the product isotopes from the compound, which still contains the target isotopes, a high specific activity can be achieved. However, batch irradiations using the Szilard-Chalmers method for production of high specific activity gives low production yields. In order to increase these production yields, a continuous flow Szilard-Chalmers system is proposed. The objective of this research is to investigate the main processes at play in a continuous flow system using the Szilard-Chalmers method on 165HoDOTAfor the production of high specific activity 166Ho. Investigations on the labelling of Ho3+ to DOTA4- have shown that 96±3 % labelling efficiency is achievable. Experiments on relabelling and isotope-exchange have shown that less than 8 % of 166Ho3+ undergoes relabelling with DOTA4- or isotope-exchange with 165HoDOTA-. Also, a cation exchange separation method for separation of Ho3+ from DOTA4- and HoDOTA- was developed. Moreover, investigations on Szilard-Chalmers separation of a dried 165HoDOTAsample have shown that with a 4-minute irradiation it was possible to achieve a specific activity of 2.8±0.2 MBq mg-1 . This corresponds to an enrichment factor of 1.62±0.03 compared to an irradiation without Szilard-Chalmers separation. Decreased radiolysis by shielding and slowed neutrons, and increased initial labelling are expected to be able to increase the achieved enrichment factor even more. The continuous flow Szilard-Chalmers system could in potential prove very useful in high specific activity radionuclide production, but further improvements on its subprocesses are necessary before practical implication is worthwhile. ... Read more

Radiometals re-emerge as a promising alternative in nuclear imaging. Cyclotron production of such radiometals using liquid targets solve critical impurity problems seen with current conventional production methods. Purification employing liquid-liquid extraction in microfluidic environments has recently been investigated. Fluid behaviour in microfluidic environments are deeply laminar, and one of the dominant factors in mass transfer in such environments is diffusion. For optimal design, numerical models are being developed to theoretically describe mass transfer in a microfluidic environment. To achieve this, diffusion coefficients of radiometals in their respective liquid target solutions need to be known. Exploiting the laminar flow properties in microfluidics, microfluidic devices have been employed in determining diffusion coefficients. This study presents a simplified 2D theoretical description of mass transfer in single phase flows in microfluidic channels. It has been attempted to verify the proposed model by determining the diffusion coefficient with methylene blue in an aqueous solution for direct comparison with literature. The method was tested for microfluidic devices of varying geometries, different flow rates and alternative setups, and yielded overestimations of a factor of two regarding literature. Consistently finding this overestimation, along with the discovery of several small mistakes in work presented in literature, does not render the method inaccurate. Further research in what range microfluidic devices remain an appropriate tool for determining diffusion coefficients is required. Diffusion coefficients for 68Ga in target solutions of varying concentrations of zinc nitrate, dissolved in aqueous solutions of varying concentrations of nitric acid were investigated. The influence on concentration of nitric acid was minimal, while the diffusion coefficient was found to be inversely proportional to the viscosity of the target solution, in correspondence with the general behaviour of several empirical correlation relations for finding the diffusion coefficient. ... Read more

Microfluidic extraction is a promising alternative for existing extraction methods of radioisotopes due to the high surface-to-volume ratio. When assessing the compatibility of microfluidic material with the extraction system, there are three critical aspects—compatibility with organic solvents, compatibility with the radiochemistry, and, most importantly, the resistance to radiation-induced damage. Resistance to radiation-induced damage includes the primary reactions of the radiation with the matter, such as bond cleavage and the indirect damage caused by radiation due to free radicals. On the other hand, polymers are an interesting alternative as they are cheap and suitable for producing microfluidic chips. Therefore, in this experimental study, multiple interactions with polymers and quartz caused by radiation are assessed. In general, most radiation-induced modifications can be traced back to changes taking place in the structure of the material. Some of the changes have been attributed to the scission of the polymer chains, promotion of cross-linkages, breaking of covalent bonds, formation of carbon clusters, and liberation of volatile products. However, these materials must not lose their mechanical and chemical properties to maintain a well-functioning microfluidic extraction system. Atomic layer deposition (ALD) is an interesting surface modification method due to its self-limiting nature and atomic precision control. With ALD, it is possible to deposit a nano-scale layer of metal oxide that reduces surface-induced damage without changing much of its bulk properties. Furthermore, with ALD, it is possible to change the wettability of the material to make them suited for microfluidic liquid-liquid extraction. This study showed that a 40nm T iO2 thin-film was able to stabilize the surface modifications during high flux electron irradiation. A similar pattern is found between the samples coated with VALD as radiation-induced surface activation is achieved. Briding oxygen that usually is present on the surface gets replaced by carboxyl groups and increases the surface energy to increase the hydrophilicity of the surface. Furthermore, polycarbonate, quartz, and high-density polyethylene showed impressive radiation resistance up to 5MGy as Young’s modulus showed no significant difference. With this study, it is possible to use nano-coating to stabilize the radiation-induced surface activation and can be helpful for surface modifications in multiple fields. ... Read more

Anaemia affects a third of women and almost 50% of infants and toddlers worldwide. Iron deficiency is the most common cause of anaemia, and the most common nutritional disorder in the world. To increase dietary iron intake, iron fortification of staple foods commonly consumed by the general public is an effective approach to prevent and control iron deficiency anaemia. It is important to maximise the iron bioavailability (absorption by the human body) in these fortified products, since iron overload is also known to cause Since the diet of infants and toddlers revolves around milk, milk is a good food carrier to address iron deficiency anaemia in children. The aim of this project is to assess the influence of five factors on the bioavailability of iron fortified skim milk: (1) iron concentration, (2) molecular form of the added iron, (3) storage time after fortification, (4) the addition of an iron enhancer and (5) the addition of an iron inhibitor.
Skim milk was fortified with FeC l2 and FeC l3 to 5 and 20 mmol Fe L−1
and stored for 24 hours or one week.
Part of the milk was further left untreated and to another part ascorbic acid (vitamin C) or tannic acid were added as respectively iron enhancer and iron inhibitor. The bioavailability of the iron in these milk samples was assessed on phase distribution and oxidation state, since it is believed that iron in the soluble phase of the milk and in the oxidation state Fe2+ is more bioavailable.
Analysis showed that the difference in iron concentration induced a pH decrease, which was greater for the higher concentrations of iron and the molecular form FeC l3. The pH difference caused the percentage of iron present in the casein fraction to increase, in the protein fraction to decrease and did not influence the iron in the soluble phase. It was also found that the 20 mmol L −1 FeC l2 showed more iron in the soluble phase and more Fe2+, whereas no statistical difference was observed for the 5 mmol L −1 , which might also be due
to the pH difference. The increase in storage time to one week was reflected by an increase in iron bound to the caseins. This shift was not reflected in a change of oxidation state. The addition of the iron enhancer (ascorbic acid) increased the iron present in the protein fraction and soluble phase, which was strengthened by the further decrease in pH. The chelation of iron by ascorbic acid did not necessarily reduce Fe3+ tot Fe2+; the Fe2+ decreased for the 20 mmol L −1 FeC l2, whereas it increased for the 20 mmol L −1 FeC l3. Lastly the
addition of the iron inhibitor resulted in a significant decrease of Fe2+. Most iron was bound to the casein or precipitated as iron-tannic acid complex.
Overall, this research confirmed that the bioavailability of milk is not easily evaluated, since the behaviour of iron in milk depends on many different factors that can not be studied isolated. Only by evaluating many possible combinations of concentration, molecular forms, additives and storage conditions, the bigger puzzle can be solved. This project attributed to a part of the solution and is therefore a valuable contribution in the development of bioavailable milk products, that will reduce iron deficiency anaemia in children. ... Read more

Calcium is an important mineral which the body uses to maintain strong bones and carry out many important bodily functions. According to the Dutch nutrition center people in the Netherlands consume 80-90% of their calcium through milk and other milk products. Often times people will further ’process’ milk for other food products. Examples of these include boiling milk to make hot chocolate or freezing it for ice-cream. These temperature changes can have great influence on the bio-availability of the Calcium. The goal of this thesis was to find the effect of temperature on the bio-availability of Calcium in milk. This was done through 2 experiments. Dialysing skim bovine milk at temperatures between 4-90°C and heating or cooling the bovine milk to temperatures between -18°C-95°C and then dialysing at room temperature. The dialysis separates the soluble and insoluble phase of milk allowing for the calculation of percentage soluble calcium which is a good indicator for bio-availability of calcium in milk. It was found that there is a linear relationship between the temperature of the milk and the percentage soluble Calcium, the higher the temperature of the milk the lower the amount of bio-available calcium in the milk. Furthermore when looking at the heated milk it was found that heating to 60°C and above all showed a similar drop in percentage soluble calcium indicating some permanent loss of bio-available calcium. This permanent loss is however lower than what can be observed to be lost in the milk whilst hot indicating that a portion of the calcium that becomes insoluble upon heating returns to the soluble phase once returned to its original temperature. ... Read more