DIFFERENCES IN THE DISTRIBUTION OF ZIRCONIUM-95 AND NIOBIUM-95 IN THE RAT

Exploring the Potential of Zirconium-89 in Diagnostic Radiopharmaceutical Applications: An Analytical Investigation

This study highlights the use of ⁸⁹Zr-oxalate in diagnostic applications with the help of WinAct and IDAC2.1 software. It presents the biodistribution of the drug in various organs and tissues, including bone, blood, muscle, liver, lung, spleen, kidneys, inflammations, and tumors, and analyzes the maximum amount of nuclear transformation per Bq intake for each organ. The retention time of the maximum nuclear transformation and the absorbed doses of the drug in various organs and tissues are also examined. Data from clinical and laboratory studies on radiopharmaceuticals are used to estimate the coefficients of transition. The accumulation and excretion of the radiopharmaceutical in the organs is assumed to follow an exponential law. The coefficients of transition from the organs to the blood and vice versa are estimated using a combination of statistical programs and digitized data from the literature. WinAct and IDAC 2.1 software are used to calculate the distribution of the radiopharmaceutical in the human body and to estimate the absorbed doses in organs and tissues. The results of this study can provide valuable information for the biokinetic modeling of wide-spectrum diagnostic radiopharmaceuticals. The results show that ⁸⁹Zr-oxalate has a high affinity for bones and a relatively low impact on healthy organs, making it helpful in targeting bone metastases. This study provides valuable information for further research on the development of this drug for potential clinical applications.

Understanding the in vivo fate of radioimmunoconjugates for nuclear imaging

Over the past 25 years, antibodies have emerged as extraordinarily promising vectors for the delivery of radionuclides to tumors for nuclear imaging. While radioimmunoconjugates often produce very high activity concentrations in target tissues, they also are frequently characterized by elevated activity concentrations in healthy organs as well. The root of this background uptake lies in the complex network of biological interactions between the radioimmunoconjugate and the subject. In this review, we seek to provide an overview of these interactions and thus paint a general picture of the in vivo fate of radioimmunoconjugates. To cover the entire story, we have divided our discussion into 2 parts. First, we will address the path of the entire radioimmunoconjugate as it travels through the body. And second, we will cover the fate of the radionuclide itself, as its course can diverge from the antibody under certain circumstances. Ultimately, our goal is to provide the nuclear imaging field with a resource covering these important-yet often underestimated-pathways.

Biokinetic models for Group VB elements

This paper reviews biokinetic data for the Group VB elements vanadium, niobium, and tantalum, and presents biokinetic models describing their systemic behaviour. The model for systemic niobium in adults was developed earlier and described in Publication 134 of the International Commission on Radiological Protection. The model for niobium is used as a starting point for the development of models for vanadium and tantalum. Published biokinetic data for vanadium, including comparisons with niobium, indicate that the initial distribution of vanadium is broadly similar to that of niobium but that vanadium is less firmly fixed in most tissues and is excreted more rapidly than niobium. Biokinetic data for tantalum are more limited but suggest that its systemic behaviour closely resembles that of niobium at early times after administration. The model for niobium is proposed for application to tantalum in view of the suggested biological similarities of tantalum and niobium, their generally strong coherence in nature due to similar ionic radii and identical valence states, and the difficulties in developing parameter values directly from available data for tantalum. The proposed model for vanadium relies largely on vanadium-specific information and varies considerably from the model for niobium.

PET imaging with ⁸⁹Zr: from radiochemistry to the clinic

The advent of antibody-based cancer therapeutics has led to the concomitant rise in the development of companion diagnostics for these therapies, particularly nuclear imaging agents. A number of radioisotopes have been employed for antibody-based PET and SPECT imaging, notably ⁶⁴Cu, ¹²⁴I, ¹¹¹In, and (99m)Tc; in recent years, however, the field has increasingly focused on ⁸⁹Zr, a radiometal with near ideal physical and chemical properties for immunoPET imaging. In the review at hand, we seek to provide a comprehensive portrait of the current state of ⁸⁹Zr radiochemical and imaging research, including work into the production and purification of the isotope, the synthesis of new chelators, the development of new bioconjugation strategies, the creation of novel ⁸⁹Zr-based agents for preclinical imaging studies, and the translation of ⁸⁹Zr-labeled radiopharmaceuticals to the clinic. Particular attention will also be dedicated to emerging trends in the field, ⁸⁹Zr-based imaging applications using vectors other than antibodies, the comparative advantages and limitations of ⁸⁹Zr-based imaging compared to that with other isotopes, and areas that would benefit from more extensive investigation. At bottom, it is hoped that this review will provide both the experienced investigator and new scientist with a full and critical overview of this exciting and fast-developing field.

In vivo biodistribution and accumulation of 89Zr in mice

INTRODUCTION

The present investigation focuses on the chemical and biological fate of (89)Zr in mice. Electrophoreses of (89)Zr solvated or chelated in different conditions are here presented. The biological fate of mice injected with [(89)Zr]Zr-oxalate, [(89)Zr]Zr-chloride, [(89)Zr]Zr-phosphate, [(89)Zr]Zr-desferrioxamine and [(89)Zr]Zr-citrate is studied with the biodistribution, the clearances and positron emission tomography images. A special focus is also given regarding the quality of (89)Zr bone accumulation.

METHODS

Electrophoreses were carried out on chromatography paper and read by gamma counting. Then, the solutions were intravenously injected in mice, imaged at different time points and sacrificed. The bones, the epiphysis and the marrow substance were separated and evaluated with gamma counts.

RESULTS

The clearances of [(89)Zr]Zr-chloride and [(89)Zr]Zr-oxalate reached 20% of injected dose (ID) after 6 days whereas [(89)Zr]Zr-phosphate was only 5% of ID. [(89)Zr]Zr-citrate and [(89)Zr]Zr-DFO were noticeably excreted after the first day postinjection (p.i.). [(89)Zr]Zr-chloride and [(89)Zr]Zr-oxalate resulted in a respective bone uptake of ∼15% ID/g and∼20% ID/g at 8 h p.i. with minor losses after 6 days. [(89)Zr]Zr-citrate bone uptake was also observed, but [(89)Zr]Zr-phosphate was absorbed in high amounts in the liver and the spleen. The marrow cells were insignificantly radioactive in comparison to the calcified tissues.

CONCLUSION

Despite the complexity of Zr coordination, the electrophoretic analyses provided detailed evidences of Zr charges either as salts or as complexes. This study also shows that weakly chelated, (89)Zr is a bone seeker and has a strong affinity for phosphate.

Dialysis osteomalacia: a possible role for zirconium as well as aluminium

Six patients with dialysis osteomalacia were studied before and after treatment with desferrioxamine. Before treatment, all six had severe osteomalacia with histochemical evidence of metals at the mineralization front, confirmed by energy dispersive X-ray microanalysis to include Al, Zr and Fe. Zr was not detected by histological staining in patients without dialysis osteomalacia. After treatment a decrease of Al and Zr was associated with improvement in clinical, biochemical, radiological and histological parameters. These observations suggest the possibility of a role for metals other than Al in the pathogenesis of dialysis osteomalacia.