D. Janković

Investigating an organ-targeting platform based on hydroxyapatite nanoparticles using a novel in situ method of radioactive 125Iodine labeling

In this study, we have investigated the synthesis of nanoparticles of hydroxyapatite (HAp) and hydroxyapatite coated with chitosan (HAp/Ch) and the chitosan-poly-d,l-lactide-co-glycolide polymer blend (HAp/Ch-PLGA) as an organ-targeting system. We have examined and defined the final destination, as well as the dynamics and the pathways of the synthesized particles following intravenous administration in vivo. The XRD, ZP, FT-IR and SEM analyses have confirmed that the hydroxyapatite nanoparticles with d50=72 nm are coated with polymers. Radioactive 125-Iodine ((125)I), a low energy gamma emitter, was used to develop a novel in situ method for the radiolabeling of particles and investigation of their biodistribution. (125)I-labeled particles exhibited high stability in saline and serum over the second day, which justified their use in the following in vivo studies. The biodistribution of (125)I-labeled particles after intravenous injection in rats differed significantly: HAp particles mostly targeted the liver, HAp/Ch the spleen and the liver, while HAp/Ch-PLGA targeted the lungs. Twenty-four hours post injection, HAp particles were excreted completely, while both (125)I-HAp/Ch and (125)I-HAp/Ch-PLGA were retained in the body for a prolonged period of time with more than 20% of radioactivity still found in different organs.

Preparation and in vivo evaluation of multifunctional 90 Y-labeled magnetic nanoparticles designed for cancer therapy

Two different types of magnetic nanoparticles (MNPs) were synthesized in order to compare their efficiency as radioactive vectors, Fe₃O₄-Naked (80 ± 5 nm) and polyethylene glycol 600 diacid functionalized Fe₃O₄(Fe₃O₄-PEG600) MNPs (46 ± 0.6 nm). They were characterized based on the external morphology, size distribution, and colloidal and magnetic properties. The obtained specific power absorption value for Fe₃O₄-PEG600 MNPs was 200 W/g, indicated their potential in hyperthermia based cancer treatments. The labeling yield, in vitro stability and in vivo biodistribution profile of (90) Y-MNPs were compared. Both types of MNPs were (90)Y-labeled in reproducible high yield (>97%). The stability of the obtained radioactive nanoparticles was evaluated in saline and human serum media in order to optimize the formulations for in vivo use. The biodistribution in Wistar rats showed different pharmacokinetic behaviors of nanoparticles: a large fraction of both injected MNPs ended in the liver (14.58%ID/g for (90)Y-Fe₃O₄-Naked MNPs and 19.61%ID/g for (90)Y-Fe₃O₄-PEG600 MNPs) whereas minor fractions attained in other organs. The main difference between the two types of MNPs was the higher accumulation of (90)Y-Fe₃O₄-Naked MNPs in the lungs (12.14%ID/g vs. 2.00%ID/g for (90)Y-Fe₃O₄-PEG600 MNPs) due to their in vivo agglomeration. The studied radiolabeled magnetic complexes such as (90)Y-Fe₃O₄-PEG600 MNPs constitute a great promise for multiple diagnostic-therapeutic uses combining, for example, MRI-magnetic hyperthermia and regional radiotherapy.

Alteration of the organ uptake of the 99mTc-radiopharmaceuticals, 99mTc-DPD, 99mTc-DMSA, 99mTc-tin colloid and 99mTc-MAA, induced by the applied cytotoxic drugs methotrexate sodium and cyclophosphamide

AimTo investigate the influence of certain cytotoxic drugs on the organ uptake of the following 99mTc-radiopharmaceuticals: 99mTc-2,3-dicarboxypropane-1,1-diphosphonic acid (99mTc-DPD), 99mTc-meso-2,3-dimercaptosuccinic acid (99mTc-DMSA), 99mTc-tin colloid and 99mTc-macroaggregated albumin (99mTc-MAA). Methotrexate sodium and cyclophosphamide were used as models to evaluate these effects. MethodsTwo groups of healthy male Wistar rats were treated separately by oral application of the drugs for 7 days. On the eighth day, each of the 99mTc-radiopharmaceuticals was applied in a separate group of treated animals. They were sacrificed at different time intervals and the radioactivity in the organs of interest was measured. The organ uptake of the 99mTc-radiopharmaceuticals in an additional control group of animals was also studied. ResultsThe results obtained showed an alteration in the organ uptake of 99mTc-radiopharmaceuticals in animals treated with cytotoxic drugs. In rats treated with methotrexate sodium, there was a higher uptake of 99mTc-DMSA in the bones, stomach and intestine, a higher uptake of 99mTc-DPD in the bones, intestine, blood and muscle, a lower uptake of 99mTc-tin colloid in the liver and a lower accumulation of 99mTc-MAA in the lungs. Cyclophosphamide-treated animals showed enhanced uptake of 99mTc-DMSA in the kidneys, a twofold enhanced uptake of 99mTc-DPD in all organs except the stomach, a decreased uptake of 99mTc-tin colloid in the lungs, spleen and kidneys and a significantly decreased uptake of 99mTc-MAA in the lungs. ConclusionThese results confirm that both methotrexate sodium and cyclophosphamide may alter the organ uptake of 99mTc-radiopharmaceuticals in experimental animals.

Development and evaluation of 90Y-labeled albumin microspheres loaded with magnetite nanoparticles for possible applications in cancer therapy

Radiolabeled albumin microspheres with encapsulated citric acid-coated magnetite nanoparticles were developed as a targeting approach to localize both radioactivity and magnetic energy at the tumor site. We present in vitro and in vivo studies of yttrium-90 (90Y)-labeled human serum albumin magnetic microspheres (HSAMMS) as a multifunctional agent for possible applications in a bimodal radionuclide-hyperthermia cancer therapy. The HSAMMS were produced using a modified emulsification-heat stabilization technique and contained 11 nm magnetite nanoparticles coated with citric acid, distributed as inhomogeneous clusters within the albumin microspheres. The size, size distribution and the morphology of magnetite nanoparticles and HSAMMS were determined by FESEM, HRTEM and SEM/FIB dual beam. The average particle size of the complete HSAMMS was 20 μm, and they exhibited superparamagnetic behavior at room temperature. The in vitro experiments (in saline and human serum) revealed the high stability of the labeled HSAMMS in saline and human serum after 72 h. Following the intravenous administration of the 90Y-HSAMMS in rats, 88.81% of the activity localizes in the lungs after 1 h, with 82.67% remaining after 72 h. These data on 90Y-HSAMMS provide good evidence for their potential use in bimodal radionuclide-hyperthermia cancer therapy.

Novel multifunctional 90Y-labelled albumin magnetic microspheres for cancer therapy

We present in vitro and in vivo studies of yttrium-90 (Y)-labelled human serum albumin magnetic microspheres (HSAMMS) as multifunctional agent for bimodal radionuclidehyperthermia cancer therapy. The HSAMMS were produced using a modified emulsificationheat stabilization technique and contained 10-nm magnetite nanoparticles coated with citric acid, distributed as inhomogeneous clusters within the albumin microspheres. The average particle size of the complete HSAMMS was 20 μm, and they exhibited superparamagnetic behavior at

90Y-Labeled Tin Fluoride Colloid as a Promising Therapeutic Agent: Preparation, Characterization, and Biological Study in Rats

In this study, tin fluoride colloid (SnF-c) was prepared, labeled with yttrium-90 ((90)Y), and characterized with respect to its physicochemical properties and biological behavior in an animal model. Particle size of SnF-c, at constant concentration of SnF(2), was dependent on pH, concentration of sodium fluoride (NaF), temperature, and time. The particle size of SnF-c decreased with an increase in NaF concentration and a decrease in reaction mixture pH. Radiolabeling yield of (90)Y-SnF-c at higher temperature increased and it was greater than 98% for the preparation at 95 °C. The (90)Y-SnF-c demonstrated high in vitro stability both in human serum and human synovial fluid at 37 °C up to 7 days. In vivo distribution studies in healthy male Wistar rats of (90)Y-SnF-c (particles <1 μm), following intravenous administration, revealed that the localization takes place preferably in the liver. The (90)Y-SnF-c (particles >1 μm) was well retained in the synovial space for 96 h after intra-articular injection, whereas leakage of (90)Y from the joint was 1.96% over this period. Because of high labeling yield and stability, (90)Y-SnF-c might be a promising agent for radiosynovectomy or therapy of liver malignancies.

Labeling, characterization, and in vivo localization of a new 90Y-based phosphonate chelate 2,3-dicarboxypropane-1,1-diphosphonic acid for the treatment of bone metastases: Comparison with 99mTc–DPD complex

The goal of this investigation was to examine the possibilities for yttrium-90-labeling of the 2,3-dicarboxypropane-1,1-diphosphonic acid (DPD), which is currently labeled with technetium-99m and as a (99m)Tc-DPD clinically used as bone imaging agent. Analysis of the complex enclosed the radiochemical quality control methods, biodistribution studies, as well as the determination of pharmacokinetic parameters. The biological behavior of complexes (90)Y-DPD, (99m)Tc-DPD and (90)Y-labeled DPD-kit formulation [(90)Y-(Sn)-DPD] in animal model was compared. The labeling conditions were standardized to give the maximum yield, which ranged between 93% and 98%. The examined (90)Y complex could be easily prepared, with an outstanding yield and was also found to be very stable for at least 10h after (90)Y-labeling. Protein binding value was 4.6+/-0.7% for (90)Y-DPD complex and the complex possess a hydrophilic character. The satisfactory results of (90)Y-DPD biodistribution in healthy test animals were obtained; the uptake in the bone was 11-13%ID/g after 24h depending on the pH value during the preparation. With high skeletal uptake, a minimum uptake in soft tissues and rapid blood clearance the (90)Y-DPD complex proved to be an excellent candidate for targeting tumor therapy.

Comparison of some physicochemical and pharmacokinetical parameters of 99mTc-PAH, 99mTc-MAG3 and 131I-OIH

The purpose of this study was to compare some physicochemical characteristics as well as pharmacokinetic behavior of 99mTc-PAH, as a novel renal agent, with 99mTc-MAG3 and 131I-OIH. 99mTc-PAH was prepared from lyophilized kit by adding 99mTcO4–. Labeled complex was stabile and high radiochemical purity radiopharmaceutical, with a low percentage of protein bound to human albumin and hydrophilic character. In spite of its smaller renal uptake, 99mTc-PAH gave satisfactory renal images. 99mTc-PAH showed faster urinary elimination than 99mTc-MAG3 and similar to those one for 131I-OIH. The comparison of pharmacokinetic parameters of 99mTc-PAH, 99mTc-MAG3 and 131I-OIH indicated the favorable characteristics of 99mTc-PAH.

Technetium-99m labeling of hippuric and p-amino-hippuric acid in the presence of DTPA: Biological and pharmacokinetic evaluation and comparison with99mTc-DTPA

Abstract99mTc-Hipp as a modified99mTc-DTPA, and99mTc-PAH as a new renal agent are developed. Each veal of lyophilised kit contain hippuric (Hipp) or p-aminohippuric acid (PAH), diethyltriaminepentaacetic acid as calciumtrisodium salt (CaNa3DTPA) and stannouschloride (SnCl2·xH2O), in molar ratio Hipp/PAH:DTPA=4∶1. They are high radiochemical purity radiopharmaceuticals, with hydrophilic character and low percentage of protein binding. The ITL chromatography and HPLC analyses of these labeled compounds have shown almost identical results as99mTc-DTPA, but their biological behavior in rats confirm certain differences.99mTc-Hipp is a renal agent clearing by the glomerular system, with better pharmacokinetical parameters than99mTc-DTPA:t1/2(α)=4.1 min,t1/2(β)=198.6 min,Kcl=1.2·10−2min−1 and a twofold value for blood clearance (Cl=2.07 ml/min).99mTc-PAH is a quite different renal agent, rapidly secreted by kidney as a tubular secretion agent. Its pharmacokinetical parameters:t1/2(α)=2.5 min,t1/2(β)=41.7 min andKcl=5.1·10−4 min−1 are almost equal to those of99mTc-MAG3, but the blood clearance of Cl=5.22 ml/min is even higher than that of IOH clearance.

Modified pyrophosphate-99mTc kit for application in nuclear cardiology

A modified99mTc(Sn)-pyrophosphate (PyP) kit for the application in nuclear cardiology (radioventriculography, angiocardiography, scintigraphy of blood pool) was developed. Each vial contains 12 mg PyP (Na4P2O7), 4 mg SnCl2·2H2O, 2.5 mg gentisic acid and 10 mg NaCl. The reconstitution is performed by dissolving the lyophilized kit in 3 ml 0.9% NaCl. In comparison with the standard pyrophosphate kit for bone scanning and detection of miocardial infarction, it contains an increased amount of Sn(II) so that the molar ratio ligand/reductant is lowered from 25 to 2.5. The radiochemical analyses showed that the radiochemical purity of the labeled kit is high (>90%) during three hours after addition of99mTc-activity. The shelf-life of the inactive freeze-dried preparation is up to four months providing that it is kept in vacuum and at appropriate temperature (2–8°C). The biodistribution studies revealed increased accumulation in blood and low uptake by liver and kidneys. It was concluded that the modified kit performs stable and reproducible properties.