Instant Thin Layer Chromatography Research Articles

^{99m}Tc labeled levofloxacin as an infection imaging agent: a novel method for labeling levofloxacin using cysteine\cdot HCl as co-ligand and in vivo study

Levofloxacin was labeled with ^{99m}Tc using cysteine\cdot HCl as co-ligand and SnCl_2.2H_2O as reducing agent. The influence of various parameters such as amount of cysteine\cdot HCl, reducing agent, pH value, and reaction time on labeling process was studied. After optimizing the conditions the labeling was performed at pH 5 using 1 mg of levofloxacin, 500 \mu g of cysteine\cdot HCl, 50 \mu g of SnCl_2.2H_2O, and 15 min reaction time. The radiochemical purity was determined with the help of instant thin layer chromatography (ITLC) and reverse phase high performance liquid chromatography (RP-HPLC) which was more than 95% and was stable for up to 6 h. Biodistribution of ^{99m}Tc-levofloxacin (^{99m}Tc-lefx) was studied in infection induced rat models using live Staphylococcus aureus and heat killed S. aureus (sterile inflammation model). In the case of the live S. aureus induced abscess model, the accumulation of ^{99m}Tc-lefx at target was 3.96, which was higher than that of ^{99m}Tc-ciprofloxacin (^{99m}Tc-cifx), taken as the control.

Automated Module Radiolabeling of Peptides and Antibodies with Gallium-68, Lutetium-177 and Iodine-131

Our objectives were to automate radiolabeling of therapeutic activities for safe, reliable, cost-effective, practical routine preparation of (177)Lu-radiopeptides, (131)I radioimmunotherapeutic agents, and (68)Ga-peptide PET diagnostics and, in particular, minimize radiation exposure to the radiopharmaceutical chemist. Reprogramming and adaptation of a commercially available synthetic module (IBA molecular; Synthera®) allowed high yield, fully automated, in-house radiolabeling of novel therapeutic and diagnostic radiopharmaceuticals under remote shielded sterile conditions. Radiochemical yield and purity was measured by instant thin-layer chromatography and high-performance liquid chromatography. (68)Ga-octreotate and (177)Lu-octreotate were synthesized, resulting in both radiochemical yield and radiochemical purity greater than 99%. Synthesis of (131)I-rituximab resulted in a yield of 60%, with a radiochemical purity greater than 99%. Using 400 MBq (68)GaCl(3) per synthesis, the estimated absorbed body and hand dose for a manual synthesis was 2 and 27 μ Sv, contrasting with automated synthesis exposure of 1.3 and 7.9 μ Sv. Using 8000 MBq (177)LuCl(3) per synthesis, the estimated absorbed body and hand dose for a manual synthesis was 44.7 and 75 μ Sv, contrasting with automated synthesis exposure of 2.5 and 20 μ Sv. Using 6000 MBq (131)I per synthesis, the estimated absorbed body and hand dose for a manual synthesis was 83.7 and 335 μ Sv, contrasting with automated synthesis exposure of 10.9 and 54.7 μ Sv. The reduction in radiation exposure by automated synthesis of radiopharmaceuticals in the Synthera® module was at least five fold. Automated synthesis of therapeutic (177)Lu and (131)I radiopharmaceuticals and (68)Ga PET agents in the shielded sterile Synthera® module is simple, practical, and efficient and virtually eliminates radiation exposure to the radiopharmaceutical chemist.

Radiolabelling of peptides for PET, SPECT and therapeutic applications using a fully automated disposable cassette system

Radiolabelled somatostatin analogues have found wide clinical use in nuclear medicine for both diagnostic and therapeutic applications. Here, we describe the development of a fully automated synthesis system allowing radiolabelling of 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA)-derivatized peptides with ⁶⁸Ga/¹¹¹In/¹⁷⁷Lu and ⁹⁰Y, meeting radiation safety and pharmaceutical requirements. The system consists of a syringe pump, a holder for insertion of a single use multivalve cassette, a heater and a removable radiation shielding. ⁶⁸Ga labelling was performed in acetate buffer and ¹⁷⁷Lu, ⁹⁰Y and ¹¹¹In labelling in ascorbate buffer, respectively, followed by purification on a C18 cartridge and final sterile filtration. Cross-contamination was prevented by using disposable cassettes and also by ensuring pharmaceutical standards. Radiochemical purity (RCP) was determined by instant thin-layer chromatography on silica gel impregnated glass fibres and reversed-phase high performance liquid chromatography. ⁶⁸Ga-DOTA-peptides were prepared with high RCP (>91%) and radiochemical yields (RCY>80% decay corrected) and ⁶⁸Ge content was less than 0.0001% in all cases. Synthesis time did not exceed 30 min. ¹¹¹In, ¹⁷⁷Lu and ⁹⁰Y labelling of DOTA-peptides resulted again in high yields (approximately 90%) and RCP (approximately 95%) and total synthesis time of less than 45 min. Radiation dose to fingers was considerably reduced when compared with manual labelling procedures. The described system allows fully automated, aseptic preparation of DOTA-peptides radiolabelled with different radionuclides in high radiochemical yields and pharmaceutical quality suitable for clinical application.

HPLC investigation of the radiochemical purity of 99mTc-MIBI

Technetium-99m-sestamibi (99mTc-MIBI) is a small, lipophilic and cationic compound used for myocardial perfusion imaging. In addition, 99mTc-MIBI has been shown to be useful in identifying several types of tumors, such as breast, lung and thyroid cancers. The high quality of this radiopharmaceutical and its uniformity are very important facts for application of this preparation in clinical practice. The monograph for 99mTc-MIBI recommends at least 90% radiochemical purity (RCP) for clinical use. Various factors may influence the RCP of certain reagent kits. Some of these include the amount of activity added to the reagent kit, heating time and the age of the formulated kit. The effect of these factors on RCP of 99mTc-MIBI has been investigated using high performance liquid chromatography (HPLC) and instant thin layer chromatography.

SU‐E‐T‐325: Development of a Radioscandium Immunoconjugate for Radioimunotherapy

Purpose: Developing monoclonal antibodies with beta‐emitters has led to the introduction of important agents in radioimmunotherapy. In this work, Sc‐46 chloride was obtained by thermal neutron flux (4 × 1013 n.cm‐2.s‐1) of natural metallic scandium sample followed by dissolution in acidic media (radiochemical purity ITLC, >99%) as a substitute for 47Sc in radiolabeling studies. Methods: 46Sc was produced with a specific activity of approximately 7.0–7.5 mCi/mg and radionuclidic purity of >98% by irradiation. NHS DOTA was freshly prepared and kept under a blanket of dry N2. Rituximab (MabThera) was used without further purification. Whatman No. 1 paper was obtained from Whatman (Maidstone, UK) for instant thin layer chromatography (ITLC). Radio‐chromatography was performed by using a bioscan AR‐2000 radio TLC scanner instrument (Bioscan). A high purity germanium (HPGe) detector coupled with a Canberra™ (model GC1020‐7500SL) multichannel analyzer and a dose calibrator ISOMED 1010 were used for counting distributed activity in rat organs. Results: The liver is the major target organ due to the presence of metaloproteins, apart from the liver, the spleen is the second major accumuation target.Thus, transferrin is principally responsible for scandium metabolism in vivo, while binding with ferritin is negligible []. Slight differences in the reported biodistribution data and the present work are possibly because of using rats instead of mice. Conclusions: As an immunoconjugate model, rituximab was conjugated with DOTA chelating agent, followed by 46Sc‐radiolabeling. The biodistributions of radiopharmaceutically acceptable 46ScCl3 and 46Sc‐DOTA‐rituximab formulations were checked in wild‐type rats up to 72 hours post injection. The biodistribution of 46ScCl3 among the tissues were in agreement with the former reports, while 46Sc‐DOTA‐rituximab accumulated mostly in the liver and spleen as shown in many other radiolabeled anti‐CD20 immunoconjugates. The development of other 47Sc‐labeled‐monoclonal antibodies for ultimate radioimmunotherapy based on this study using long‐half life, 46Sc radionuclide is possible.

Preparation and biological evaluation of 177Lu conjugated PR81 for radioimmunotherapy of breast cancer

PR81 is a monoclonal antibody that binds with high affinity to MUC1 antigen that is over expressed in 80% of breast cancers. In this study, we developed a method for indirect labeling of PR81 with lutetium-177 and performed all preclinical qualifications in production of a biologic agent for radioimmunotherapy of breast cancer. The radiochemical purity and in vitro stability of (177)Lu labeled PR81 was determined by instant thin layer chromatography. The immunoreactivity and cell toxicity of the complex were tested on MCF7 cell line. The biodistribution and scintigraphy studies were performed in BALB/c mice with breast tumor. The radiochemical purity was 91.2±3.8% after 2 h. The in vitro stabilities in phosphate buffer and human blood serum were 83.1±3.4% and 76.2±3.6% at 96 h, respectively. The immunoreactivity of the complex was 83.4±2.4%. The cell toxicity study showed that the complex inhibited 85.2±3.4% growth of MCF7 cells at a concentration of 2500 ng/ml after 96 h. The biodistribution and scintigraphy studies showed the accumulation of the complex at the site of tumors with high sensitivity and specificity. The results showed that one may consider (177)Lu-DOTA-PR81 as a potential radiopharmaceutical for therapy of human breast cancer, which needs further investigations.

Evaluation of alternative methods for radiochemical purity testing of indium-111 capromab pendetide

ObjectiveTo evaluate alternative methods for radiochemical purity testing of indium (In)-111 capromab pendetide after the discontinuation of instant thin-layer chromatography silica gel (ITLC-SG) strips. DesignDescriptive experimental study. SettingUnited States in 2009. ParticipantsNot applicable. InterventionPaper chromatography using Whatman 3MM strips, paper chromatography using Whatman 31ET strips, and mini-column chromatography using silica Sep-Pak cartridges were evaluated in the radiochemical purity testing of 13 consecutive vials of In-111 capromab pendetide prepared for clinical patient imaging procedures. These methods also were evaluated by testing seven aliquots of In-111 capromab pendetide that had been spiked with 5% to 15% In-111 pentetate (diethylene triamine pentaacetic acid). Main outcome measuresCorrelation coefficients, radiochemical purity values for each method compared with ITLC-SG, and procedure times. ResultsCorrelation coefficients of 0.988, 0.996, and 0.979 were found for ITLC-SG compared with Whatman 3MM, Whatman 31ET, and silica Sep-Pak, respectively. Compared with ITLC-SG, mean (±SD) radiochemical purity values differed by −0.8± (range −2.5 to 0.4) for Whatman 3MM, −0.8± (–2.3 to 0) for Whatman 31ET, and −0.5± (–3.6 to 0.7) for silica Sep-Pak. The approximate time required to develop the chromatography strip or elute the mini-column was 3, 14, 5, and 6 minutes for ITLC-SG, Whatman 3MM, Whatman 31ET, and silica Sep-Pak, respectively. ConclusionAll three methods evaluated were acceptable alternatives to ITLC-SG for radiochemical purity testing of In-111 capromab pendetide. Based on its slightly higher correlation to ITLC-SG, slightly tighter SD and range, and slightly shorter development time, Whatman 31ET is preferred in our facility.

Development of 68Ga‐Glycopeptide as an Imaging Probe for Tumor Angiogenesis

Objective. This study was aimed to study tissue distribution and tumor imaging potential of 68Ga-glycopeptide (GP) in tumor-bearing rodents by PET. Methods. GP was synthesized by conjugating glutamate peptide and chitosan. GP was labeled with 68Ga chloride for in vitro and in vivo studies. Computer outlined region of interest (counts per pixel) of the tumor and muscle (at the symmetric site) was used to determine tumor-to-muscle count density ratios. To ascertain the feasibility of 68Ga-GP in tumor imaging in large animals, PET/CT imaging of 68Ga-GP and 18F-FDG were conducted in New Zealand white rabbits bearing VX2 tumors. Standard uptake value of tumors were determined by PET up to 45 min. To determine blood clearance and half-life of 68Ga-GP, blood samples were collected from 10 seconds to 20 min. Results. Radiochemical purity of 68Ga-GP determined by instant thin-layer chromatography was >95%. Tumor uptake values (SUV) for 68Ga-GP and 18F-FDG in New Zealand white rabbits bearing VX2 tumors were 3.25 versus 7.04. PET images in tumor-bearing rats and rabbits confirmed that 68Ga-GP could assess tumor uptake. From blood clearance curve, the half-life of 68Ga-GP was 1.84 hr. Conclusion Our data indicate that it is feasible to use 68Ga-GP to assess tumor angiogenesis.

Labelling and optimization of PHOTOFRIN® with 99mTc

Abstract PHOTOFRIN® was labelled with 99mTc using SnCl2·2H2O as reducing agent. Instant thin layer chromatography (ITLC-SG) in 0.05 M NaOH was used for evaluation of radiochemical purity. Labelling efficiency was dependent on various factors that include the ligand/reductant ratio, pH and time of incubation. Therefore, optimum conditions of labelling were also determined. The stability of 99mTc-PHOTOFRIN® in serum was checked by using fresh human serum. Tissue distribution of 99mTc-PHOTOFRIN® was evaluated in Sprague Dawley rats. PHOTOFRIN® was labelled with an efficiency of >95% under optimum conditions, which were PHOTOFRIN®: 200 μg, pH: 3–4, SnCl2·2H2O: 15 μg and 30 min incubation at room temperature. The 99mTc-labelled PHOTOFRIN® remained stable in human serum for 24 h. Biodistribution study in rats revealed maximum concentration of the labelled compound in liver, lungs and spleen at 0.5 h, and significant activity was also seen in the bladder and urine, indicating the mode of urinary excretion of PHOTOFRIN®.

Chemical and biological evaluation of 153Sm and 46/47Sc complexes of indazolebisphosphonates for targeted radiotherapy

Novel 1-hydroxy-1,1-bisphosphonates derived from indazole and substituted at the C-3 position were labeled with the radionuclides (46)Sc and (153)Sm. Several parameters such as molar ligand concentration, pH, reaction time and temperature were studied. The radiolabelling yield, reaction kinetics and stability were assessed and radiocomplexes were evaluated by in vitro and in vivo experiments. The radionuclides (46)Sc and (153)Sm were obtained by neutron irradiation of natural Sc(2)O(3) and enriched (152)Sm(2)O(3) (98.4%) targets at the neutron flux of 3 × 10(14) n cm(-2)s(-1). The radiolabelling yield, reaction kinetics and stability were accomplished by ascending instant thin layer chromatography. The radiocomplexes were submitted to in vitro experiments (hydroxyapatite binding and lipophilicity) and biodistribution studies in animal models. The radionuclides (46)Sc and (153)Sm were produced with specific activities of 100 and 430 MBq mg(-1), respectively. High radiochemical yields were achieved and the hydrophilic radiocomplexes have shown high degree of binding to hydroxyapatite. Biodistribution studies at 1, 3 and 24h of the 4 radiocomplexes under study, have showed a similar biodistribution profile with a relatively high bone uptake, slow clearance from blood and a very slow rate of total radioactivity excretion from the whole animal body. We have developed a new class of indazolebisphosphonates complexes with radioisotopes of samarium and scandium. All complexes have shown high degree of binding to hydroxyapatite, which could be attributed to the ionized phosphonate groups. The bone uptake and the bone-to-muscle ratios were relatively low.

The effect of selected preparation variables on the radiochemical purity of 99mTc-EDDA-HYNIC-TOC

[99mTc-EDDA-HYNIC-D-Phe1, Tyr3]-Ocreotide (99mTc-EDDA-HYNIC-TOC) increasingly emerges to be an alternative tool for somatostatin receptor (SSTR) scintigraphy of neuroendocrine tumours. The high quality of this radiopharmaceutical and its uniformity are very important facts for application of this preparation in clinical practice. Various factors may influence the radiochemical purity (RCP) of certain reagent kits. Some of these include the amount of activity added to the reagent kit, heating time and the age of the formulated kit. The effect of these factors on RCP of 99mTc-EDDA-HYNIC-TOC has been investigated using high performance liquid chromatography (HPLC) and instant thin layer chromatography (ITLC).

Radiolabeling and dose fixation study of oral alpha-ketoglutarate as a cyanide antidote in healthy human volunteers

Context. Radiolabeling and dose fixation study of alpha-ketoglutarate (A-KG). Objective. A-KG is a potential oral antidote for cyanide poisoning. Its protective efficacy in animals was best exhibited at a dose of 2.0 g/kg body weight, which when extrapolated to human is very high. The objective of this study was to reduce the dose of A-KG in humans with concomitant increase in its bioavailability, employing pharmacoscintigraphic techniques to assess kinetics in man. Materials and methods. A-KG was radiolabeled with technetium-99m pertechnetate (Tc-99m) and its purity, labeling efficiency, and stability in vitro were determined by instant thin layer chromatography. Time-dependent bio-absorption of the drug in rats and rabbits was assessed by gamma scintigraphy after oral administration of a tracer dose of 99mTc-A-KG mixed with nonradioactive A-KG at a concentration of 0.1–2.0 g/kg in the presence or absence of aqueous dilution. Furthermore, scintigraphy and radiometry studies were performed in healthy human volunteers using 5–20 g of A-KG, given in single or split doses followed by different quantity of water. Drug bioavailability was estimated periodically. Results. High radiolabeling (>97%) of A-KG with a stability of 24 h in vitro was obtained. Less than 1% absorption of the drug occurred within 20 min after A-KG was administered in animals at a concentration of 2.0 g/kg body weight. One-tenth reduction in dose increased the bioavailability to 15%. Significant improvement in gastric emptying of the drug was achieved when the drug was administered along with 1–5 mL of water. In humans, two doses of 10 g A-KG given at an interval of 10 min, followed by 300 mL of water, increased the drug bioavailability to 40% as compared to a single dose of 20 g. Discussion. Significant reduction in A-KG dose was achieved in humans as compared to the recommended dose in animals. Conclusion. Aqueous dilution improves the bioavailability of A-KG in humans.

Studies on tolonium chloride labeled with radioiodine

Tolonium chloride is a common reagent in the diagnosis of oral premalignant and malignant lesions. This study establishes the optimal preparation of radioiodinated tolonium chloride (RTC) and evaluate its radiochemical and biological characteristics. Instant thin layer chromatography (ITLC), ion exchange chromatography (IC), paper electrophoresis, and the effect of pH on labeling efficiency revealed the chemical characterization of RTC. Biodistribution, blood clearance, urinary excretion, toxic effect, and Lugol’s solution effect on the thyroid uptake of RTC revealed RTCs biological characteristics. The optimal labeling condition was pH = 2.96 after 15 h stirring, the labeling efficiency was 60%. After purification by IC, the radiochemical purity of RTC was 94%, and the shelf life of RTC was at least 90 days. In the biodistribution study, the liver was major target organs, approximated 6.11% of injected dose accumulate in per gram of tissue (6.11% ID/g) at 10 min after injection. The tissue-to-blood radioactivity ratio significant (p < 0.05) increased with reaction time. In liver, the tissue-to-blood radioactivity ratio was 2.2 ± 0.51 at 10 min after injection, and increased to 22.4 ± 4.52 at 120 min after injection. The blood clearance study showed a significant decrease in blood radioactivity. The radioactivity in the blood was about 2.76% of the injected dose per milliliter blood at 10 min post-injection, but decreased to 0.12% at 120 min post-injection. Lugol’s solution does not affect the thyroid uptake of RTC. Almost all the administered RTC recovered at 60 h after injection, with 79% recovered in feces and 17% recovered in urine. This study shows that RTC is non-toxic, and may be suitable as a liver imaging agent.

A Rapid Radiochemical Purity Testing Method for 99mTc-Tetrofosmin

The standard radiochemical purity (RCP) testing method for (99m)Tc-tetrofosmin as described in the package insert requires extensive time (20-30 min) and considerable skill to achieve accurate results. Additionally, the instant thin-layer chromatography strip impregnated with silica gel (2x20 cm) used in the standard method will not be commercially available in the future. The purpose of this study was to evaluate whether a method developed by our laboratory for RCP testing of (99m)Tc-sestamibi could also be used as an alternative method for the RCP assay of (99m)Tc-tetrofosmin. The alternative RCP testing system consisted of a precut paper strip (1x8.5 cm) from solvent saturation pads (Pall Corp.) as the stationary phase, with 1:1 chloroform:tetrahydrofuran used as the mobile phase. To validate the reliability of the alternative method, RCP values from 17 kit preparations were compared with the 2 methods. Kits were reconstituted according to the package insert instructions, and 4 additions of (99m)Tc-sodium pertechnetate were purposely added to create trials with RCP values below the accepted limit of 90% purity. Two hundred four trials (100 of which were replicated) were run from the 17 kit preparations. Sixty-four (31%) of the 204 trials were below 90% purity based on the standard method. The overall agreement between the standard and alternative methods was 94% (192/204). The sensitivity of the alternative method for unacceptable RCP limits was 86% (55/64), and the specificity for acceptable RCP values was 98% (137/140). The agreement between the replicated trials of the alternative method was 99% (99/100), and for the standard method it was 92% (92/100). The standard method proved to be a much slower method and requires much more precision and attention. The alternative method is much faster, is easier, requires less attention to the solvent-development process, and can be used for RCP testing of both (99m)Tc-tetrofosmin and (99m)Tc-sestamibi. Furthermore, the stationary phase is much more readily available, is not moisture-sensitive, and is less susceptible to operator technique. Our method is accurate in determining the RCP value of (99m)Tc-tetrofosmin and is a better RCP testing method for (99m)Tc-tetrofosmin.

Study of magnetic ferrite nanoparticles labeled with 99mTc-pertechnetate

This study examined the applications of novel non-polymer magnetic ferrite nanoparticles (Fe3O4 NPs) labeled with 99mTc-pertechnetate (99mTcO4 −). The radiochemistry, chemistry, and biodistribution of Fe3O4 NPs labeled with 9mTcO4 − were analyzed. This paper employed instant thin layer chromatography and magnetic adsorption to evaluate the labeling efficiency and stability of 99mTc-Fe3O4 at various reaction conditions. A scanning electron microscope, X-ray diffractometer, Fourier transform infrared spectrometer, laser particle size analyzer, and superconducting quantum interference device magnetometer were used to analyze the physical and chemical properties of the Fe3O4 and 99Tc-Fe3O4 nanoparticles. The biodistribution and excretion of 99mTc-Fe3O4 were also investigated. Radiochemical analyses showed that the labeling efficiency was over 92% after 1 min in the presence of a reducing agent. Hydroxyl and amine groups covered the surface of the Fe3O4 particles. Therefore, 99Tc (VII) reduced to lower oxidation states and might bind to Fe3O4 NPs. The sizes of the 99Tc-Fe3O4 NPs were about 600 nm without ultrasound vibrations, and the particle sizes were reduced to 250 nm under ultrasound vibration conditions. Nonetheless, Fe3O4 NPs and 99Tc-Fe3O4 NPs exhibited superparamagnetic properties, and the saturation magnetization values were about 55 and 47 emu/g, respectively. The biodistribution showed that a portion of the 99mTc-Fe3O4 nanoparticles might embolize in a pulmonary capillary initially; the embolism radioactivity was cleared from the lungs and was then taken up by the liver. 99mTc-Fe3O4 metabolized very slowly only 1–2% of the injected dose (ID) was excreted in urine and about 2.37% ID/g was retained in the liver 4 h after injection. Radiopharmaceutically, 99mTc-Fe3O4 NPs displayed long-term retention, and only 99mTc-Fe3O4 NPs that dissociated to free pertechnetate could be excreted in urine. This research evaluated the feasibility of non-polymer magnetic ferrite NPs labeled with technetium as potential radiopharmaceuticals in nuclear medicine.

Studies on the porphine labeled with 99mTc–pertechnetate

The aim of this research is to use acetylacetonate as a 99mTc chelating agent label with porphyrin and evaluate its radiochemical and biological characteristics. Stannous chloride was used as a reductant to determine the chemical and biological characterization of 99mTc-complexes from labeling porphine{4′,4′′,4′′′-(2lH,23H-Porphine-5,10,15,20-terayl)tetrakis-(benzoic acid), TPPB} with 99mTc–pertechnetate. Instant thin layer chromatography (ITLC), size exclusion chromatography (SEC), paper electrophoresis, and UV/Vis spectrophotometry were used to evaluate chemical characterization. Finally, biodistribution and liver function tests were applied to evaluate biological characteristics. The results of this study show that the labeling efficiency of 99mTc(acac)–TPPB was nearly 100% when using acetylacetone (acac) as a conjugator. Three major 99mTc(acac)–TPPB complexes were separated by SEC, and all of them were hydrophilic. The UV-Vis spectra of 99mTc(acac)–TPPB complexes closely resembled those of the TPPB, but the wave lengths of their peaks changed 430, 521, 556, 591 and 647 nm after complexation. The biodistribution study selected the liver as the target organ. The 99mTc(acac)–TPPB complex may cause short-term liver injury. However, this injury can be repaired, and the reagent is quickly metabolized. Hence, the toxicity of the 99mTc(acac)–TPPB complex is within an acceptable range, and making it a promising liver imaging agent.

Ziele der Qualitätssicherung im nuklearmedizinischen Labor

Als Radiopharmaka bezeichnet man radioaktive Verbindungen, die sowohl für diagnostische Fragestellungen als auch für therapeutische Interventionen bei verschiedensten Erkrankungen eingesetzt werden können. Im allgemeinen besitzen sie keine pharmakologischen Effekte, vor allem da sie nur in sehr geringen Mengen (nanomolarer Bereich) verwendet werden. Dosis-Wirkungs-Beziehungen treten bei ihnen im Gegensatz zu „normalen” Pharmaka nicht auf. Als Parenteralia unterliegen sie einer Reihe von biologischen Qualitätskriterien wie Sterilität und Apyrogenität, aber auch sog. physikochemischen Kriterien wie chemische und radiochemische Reinheit und Radionuklidreinheit. Gerade die beiden letztgenannten sollten regelmäßig vom Anwender, der letztlich für die Bereitung der Markierungskits verantwortlich ist, überprüft werden. Dazu stehen eine Reihe schneller und einfacher Methoden wie die Dünnschichtchromatografie oder Kartuschenmethoden zur Verfügung. Unter Verwendung dieser Methoden lässt sich ein einfaches und effizientes Qualitätssicherungssystem für das nuklearmedizinische Labor etablieren, das eine hohe Produktqualität garantieren kann.

Apoptotic abscess imaging with 99mTc-HYNIC-rh-Annexin-V

Abscess formation causes systemic and localized up-regulation of neutrophil [polymorphonuclear leukocytes (PMNs)] signaling pathways. In the abscess, following bacterial ingestion or PMN activation by inflammatory mediators, PMN apoptosis is elevated and leads to the externalization of phosphatidylserine. Annexin-V (AnxV) has been shown to have high affinity to externalized phosphatidylserine. We hypothesized that (99m)Tc-AnxV will target high densities of apoptotic PMNs and image abscesses. AnxV, conjugated with hydrazinenicaotinamide (HYNIC), was labeled with reduced (99m)TcO(4)(-) and its purity was determined by instant thin-layer chromatography. Apoptosis was induced in isolated human PMNs by incubation in 2% saline for 17 and 22 h at 37 degrees C. PMNs were then incubated with (99m)Tc-HYNIC-AnxV and associated (99m)Tc was determined. Abscesses were induced in mice by intramuscular injection of bacteria or turpentine. Following intravenous administration of (99m)Tc-HYNIC-AnxV, mice were imaged and tissue distribution studied at 4 and 24 h. Radiochemical purity of (99m)Tc-HYNIC-AnxV was 84.9+/-8.11%. At 17 h, (99m)Tc-HYNIC-AnxV bound to apoptotic PMNs was 71.6+/-0.01% and 48.6+/-0.01% for experimental and control cells, respectively (P=.002). At 22 h, experimental cells retained 74.9+/-0.02% and control cells retained 47.2+/-0.02% (P=.005). (99m)Tc-HYNIC-AnxV associated with bacterial abscesses was 1.25+/-0.09 and 3.75+/-0.83 percent injected dose per gram (%ID/g) at 4 and 24 h compared to turpentine abscesses which was 1.02+/-0.16 and 0.72+/-0.17 %ID/g at 4 (P<or=.05) and 24 h (P<or=.01). (99m)Tc-HYNIC-AnxV represents a minimally invasive and promising agent to image and potentially distinguish between infectious and inflammatory abscesses.

An innovative, quick and convenient labeling method for the investigation ofpharmacological behavior and the metabolism of poly(DL-lactide-co-glycolide)nanospheres

Nanoparticles of poly(DL-lactide-co-glycolide) (PLGA) in the size range 90–150 nm wereproduced using the physicochemical method with solvent/non-solvent systems. Theencapsulation of the ascorbic acid in the polymer matrix was performed by homogenizationof the water and organic phases. In vitro degradation and release tests of PLGAnanoparticles with and without encapsulated ascorbic acid were studied for more than 60days in PBS and it has been determined that PLGA completely degrades withinthis period, fully releasing all encapsulated ascorbic acid. The cytotoxicity ofPLGA and PLGA/ascorbic acid 85/15% nanoparticles was examined with humanhepatoma cell lines (HepG2 ECACC), in vitro. The obtained results indicatethat neither PLGA nanospheres nor PLGA/ascorbic acid 85/15% nanoparticlessignificantly affected the viability of the HepG2 cells. The investigation of thedistribution and pharmacokinetics of PLGA is crucial for the effective prediction ofhost responses to PLGA in particular applications. Thus we present a method oflabeling PLGA nanospheres and PLGA/ascorbic acid 85/15 wt% nanoparticles by 99mTc which binds outside, leaving the cage intact. This enables a quick and convenient investigationof the pharmacological behavior and metabolism of PLGA. The biodistribution of 99mTc-labeled PLGA particles with and without encapsulated ascorbic acid after different periodsof time of their installation into rats was examined. PLGA nanospheres with encapsulatedascorbic acid exhibit prolonged blood circulation accompanied by time-dependent reductionin the lungs, liver and spleen, and addition in the kidney, stomach and intestine. Thesamples were characterized by x-ray diffraction, scanning electron microscopy, stereologicalanalysis, transmission electron microscopy, ultraviolet spectroscopy and instant thin layerchromatography.

Synthesis and Assessment of 99mTc Chelate-Conjugated Alendronate for Development of Specific Radiopharmaceuticals

Indole-based alendronate (AI) was derived from the condensation reaction of indole 3-carboxaldehyde with sodium alendronate (ALN) and was characterized by various spectroscopic methods (e.g., ultraviolet, fourier-transform-infrared, and liquid chromatography mass spectrometry). The AI was labeled with (99m)Tc and radiochemical purity was above 97%, which was ascertained by instant thin-layer chromatography, using different solvent conditions, with a specific activity 2-5 mCi/mg. The receptor ligand assay on human bone cell line Soas-2 showed K(D) = 0.55 nM. The derivative (AI) was stable, which was determined under physiologic conditions up to 24 hours The blood kinetic study showed a biexponential pattern as well as quick wash-out from the circulation with varying biologic t(1/2)(F) and t(1/2)(S). Excellent-quality radio images were recorded of bone, showing a rapid clearance of background activity, at an early visualization at 1.5 hours. The excretory pathway of the derivative was through the kidneys, which was evidenced by biodistribution studies. Thus, the newly synthesized derivative can be considered as a specific bone-seeking agent.