Technetium-99m dextran kit: formulation and biological behaviour

A new formulation of stannous-dextran (Sn-Dx) freeze dried kit, containing 60 mg dextran (Dx-70) and 0.08 mg SnCl₂·2H₂O, to be labelled with^99mTc, has been developed. At pH 6.5–7.0. the labelling efficiency was greater than 95%. Gel chromatography column scanning technique was applied for radiochemical purity determination of^99mTc-Dx preparation and the degree of in vivo plasma protein binding. Not less than 70% of the administered activity was bound to plasma and remained constant over a 1h period. The biological behaviour after intravenous injection of^99mTc-Dx kit was characterized by high and efficient yield of the radiopharmaceutical. The preliminarly clinical results on normal subjects showed that the radiopharmaceutical could be a useful agent for scintigraphy of leg lymph vesel, pelvic and inguinal lymph nodes. The activity uptake in liver and kidney (60 min) was relatively very low, whereas the urinal bladder activity (30 min) represents the drainage of the activity entering the blood stream after interdigital injection of^99mTc-Dx.     

Labelling and quality control of gentamycin with99mTc and biodistribution

Gentamycin sulfate (antibiotic) was labelled with^99mTc with high radioactive yield. Technetium species were studied using different types of sephadex on columns. Stannous chloride was used as reducing agent for heptavalent^99mTc obtained directly from generator to lower oxidation state prior to labelling. Optimal pH was found to form the most stable complex. A lyophilized kit was prepared and it was stable for more than three months. Mice, rats and rabbits have been used as exprimental animals. Accumulation of more than 20% of the labelled formula in kidneys 30 minutes post injection in rats has been found. Gamma camera images in rabbit were clear enough for kidney delineation thirty minutes after injection.     

99mTc-labeling and in vitro characterization of N4- and N3S-RGDS-derivative peptides

The aim of this work was to characterize the in vitro behavior of N4- and N3S-RGDS-derivative peptides labeled with ^99mTc. Peptides AGGG-Abu-GRGDSPK-NH₂ (F22) and C(acm)-GGG-Abu-GRGDSPK-NH₂ (SMA1) were synthesized by solid phase. The stability of ^99mTc-labeled peptides was assessed in a 30-fold molar excess of cysteine and in plasma. The affinity for plasma proteins was also evaluated. Labeling yield was >95% for both peptides. ^99mTc-F22 was not stable in presence of cysteine, but 63% of ^99mTc remained chelated to SMA1 up to 24 hours. Both peptides showed low affinity to plasma proteins. N3S-RGDS-derivative peptide (SMA1) showed more stable coordination binding with ^99mTc and a higher stability in plasma with regard to N4-RGDS-derivative peptide (F22).     

Effect of chemical condition of technetium-99m sodium pertechnetate on the active kit components and radiolabeling yield of Tru-Scint® ADTM monoclonal antibody kit

The chemical condition of^99mTc eluate obtained from a⁹⁹Mo-^99mTc generator is a function of the source, time elapsed after elution and age of the eluate. The radiochemical purity and stability of^99mTc labeled MAb-170 (Tru-Scint^®AD^TM, photoactivated monoclonal antibody kit) preparations was evaluated comparing pertechnetate source of known age and elution history. The effect of H₂O₂, a radiolytic impurity in^99mTc eluates, on the active kit components stannous ion and photoactivated MAb and radiolabeling, yield has been investigated. The lyophilized Tru-Scint^® AD^TM kit has been labeled with 20 to 80 mCi in 0.5 to 4.0 ml of Sodium Pertechnetate^99mTc Injection, USP. The eluates were obtained from three brands of generators and used up to six hours after elution. The kits were reconstituted either with Sodium Pertechnetate^99mTc Injection, USP or Sodium Chloride Injection, USP, 0.9% containing known amounts of H₂O₂. The reconstituted kits were analyzed for radiolabeling yield and radiochemical impurities, stannous ion and protein sulfhydryl group. The results indicated that the radiolabeling yield is a function of both the chemical condition of^99mTc eluate, generator brand and the radiolabeling parameters like reconstitution volume and activity. The observed radiolabeling yield differences did not depend on the amount of chemical technetium in the eluate. The major radiochemical impurities at 15-minute post labeling have been identified as the^99mTc-buffer complex and column adsorbed reduced^99mTc (^99mTc-Ad) species and not the unreduced^99mTcO ₄ ^– .     

Evaluation of labelling conditions,quality control and biodistribution study of 99mTc-5-aminolevulinic acid (5-ALA): a potential liver imaging agent

Labelling of 5-aminolevulinic acid (5-ALA) with ^99mTc was achieved by using SnCl₂·2H₂O as reducing agent. Radiochemical purity and labelling efficiency was determined by instant thin layer chromatography/paper chromatography. Efficiency of labelling was dependent on many parameters such as amount of ligand, reducing agent, pH, and time of incubation. ^99mTc labelled 5-ALA remained stable for 24 h in human serum. Tissue biodistribution of ^99mTc-5-ALA was evaluated in Sprague–Dawley rats. Biodistribution study (% ID/g) in rats revealed that ^99mTc-5-ALA was accumulated significantly in liver, spleen, stomach and intestine after half hour, 4 and 24 h. Significant activity was noted in bladder and urine at 4 h. High liver uptake of ^99mTc-5-ALA makes it a promising liver imaging agent.     

Synthesis and biological distribution of 99mTc–norfloxacin complex, a novel agent for detecting sites of infection

The optimization of the radiolabeling yield of ciprofloxacin analogous, norfloxacin, with technetium-99m (^99mTc) was described. Dependence of the labeling yield of ^99mTc–norfloxacin complex on the concentration of norfloxacin, SnCl₂·2H₂O content, pH of the reaction mixture and reaction time was studied. Norfloxacin was labeled with ^99mTc at pH 3 with a labeling yield of 95.4% by using 5 mg norfloxacin, 50 μg SnCl₂·2H₂O and 30 min reaction time. The formed ^99mTc–norfloxacin complex was stable for a time up to 3 h. Biological distribution of ^99mTc–norfloxacin complex was investigated in experimentally induced inflammation rats using Staphylococcus aureus (bacterial infection model) and heat killed Staphylococcus aureus and turpentine oil (sterile inflammation model). In case of bacterial infection, the T/NT value for ^99mTc–norfloxacin complex was found to be 6.9 ± 0.4 which was higher than that of the commercially available ^99mTc–ciprofloxacin under the same experimental condition.     

Neutron resonance capture analysis and applications

This paper addresses the development of two new radiopharmaceuticals for infection imaging. The optimization of the labeling yield of ciprofloxacin analogous, lomefloxacin and ofloxacin, with ^99mTc is described. ^99mTc-lomefloxacin was obtained with a radiochemical yield of 93.6% by adding ^99mTc to 2.5 mg lomefloxacin in the presence of 50 μg SnCl₂ while ^99mTc-ofloxacin was obtained (96.6%) by adding ^99mTc to 2 mg ofloxacin in the presence of 50 μg SnCl₂. Biodistribution studies in rats were carried out in experimentally induced infection in the left thigh using Staphylococcus aureus. Both thighs of the rats were dissected and counted and the ratio of bacterial infected thigh/contralateral thigh was then evaluated. ^99mTc-lomefloxacin showed higher uptake (T/NT = 6.5±0.5) in the infectious lesion than ^99mTc-ofloxacin (T/NT = 4.3±0.6) and abscess-to-muscle ratios for both preparations were higher than that of ^99mTc-ciprofloxacin (T/NT = 3.8±0.8), indicating that ^99mTc-lomefloxacin could be used for infection imaging.     

99mTc-DMSA complex preparation: the effect of pH and tin(II) chloride amount on reaction

Labelling of meso-2,3-dimercaptosuccinic acid (DMSA) with technetium-99m was reinvestigated. Dependence of the ^99mTc-DMSA complex formation on the molar ratio of DMSA:reducing agent (SnCl₂·2H₂O) and pH was studied. Five different types of ^99mTc-DMSA complexes were determined. Especially three different complexes were established in the clinically used and prepared DMSA kit labelled with ^99mTc under alkaline condition. This radiopharmaceutical is used as imaging agent of the primary medullary carcinoma in the thyroid gland and different metastasis types. The existence of all complexes was observed by paper chromatography, paper electrophoresis and high performance liquid chromatography.     

<Superscript>99m</Superscript>Tc-roxifiban: a potential molecular imaging agent for the detection and localization of acute venous thrombosis

^99mTc-roxifiban was obtained in a high radiochemical yield (98.4%) by complexing ~750 MBq ^99mTc with 2.5 mg roxifiban in the presence of 150 µg SnCl₂·2H₂O. Factors affecting the labelling yield were investigated and optimized. The complex was lipophilic and stable in saline and serum for more than 8 h. The complex structure prediction and molecular docking to its target activated GPIIb/IIIa receptor were performed. The tracer in vitro binding to activated platelets was high (27–32%). In vivo evaluation was performed through clearance, biodistribution and imaging studies in rats. All results supported the usefulness of the tracer as thrombus imaging agent.     

Evaluation of the 99mtechnetium labelling effect on Pseudomonas aeruginosa surface properties

Gamma emitter isotopes present some advantages over beta emitters as radioisotopic microbial labels. The labelling of bacteria with ^99mtechnetium (^99mTc) has recently been described. However, it was not ascertained weether the labelling process modifies microbial physicochemical surface properties important in the interaction between bacteria and eukaryotic cells. In the present study, we evaluated the effect of the labelling process on Pseudomonas aeruginosa surface charge, hydrophobicity, adherence to human buccal epithelial cells and phagocytosis by human leukocytes. No significant differences in electrophoretic mobility or cationized ferritin distribution was observed on the cell surface of labelled and unlabelled bacteria. ^99mTc labelling did not modify the hydrophobicity adhesiveness or phagocytosis of P. aeruginosa. It is concluded that bacterial labelling with ^99mTc may be a useful method for the numeration of bacteria and the analysis of their functional properties.     

Preparation and biodistribution of99mTc-HT18

The preparation of N₁-(octadecylcarbomyl-methy)-ethylenediaminetriacetic acid labelled with^99mTc is described. Reduction of technetium was made using sodium borohydride (procedure A) or stannous chloride (procedure B), and the labelling efficiency was checked by thin layer chromatography. Preliminary studies of biol-behavior of this complex were performed in white rats.     

Labelling of human serum albumin millimicrospheres (hamm) with99mTc

Human serum albumin microspheres were labelled with^99mTc as a single step kit with radiochemical yields higher than 95%. With respect to the organ distribution in mice, the per cent of injected dose in liver was 78%.     

Preparation,molecular modeling and biodistribution of 99mTc-phytochlorin complex

Phytochlorin [21H, 23H-Porphine-7-propanoicacid, 3-carboxy-5-(carboxymethyl)13-ethenyl-18-ethyl-7,8-dihydro-2,8,12,17-tetramethyl-,(7S,8S)] was labeled with ^99mTc and the factors affecting the labeling yield of ^99mTc-phytochlorin complex were studied in details. At pH 10, ^99mTc-phytochlorin complex was obtained with a high radiochemical yield of 98.4 ± 0.6 % by adding ^99mTc to 100 mg phytochlorin in the presence of 75 μg SnCl₂·2H₂O after 30 min reaction time. The molecular modeling study showed that the structure of ^99mTc-phytochlorin complex presents nearly linear HO–Tc–OH unit with an angle of 179.27° and a coplanar Tc(N1N2N3N4) unit. Biodistribution of ^99mTc-phytochlorin complex in tumor bearing mice showed high T/NT ratio (T/NT = 3.65 at 90 min post injection). This preclinical study showed that ^99mTc-phytochlorin complex is a potential selective radiotracer for solid tumor imaging and afford it as a new radiopharmaceutical suitable to proceed through the clinical trials for tumor imaging.     

Radiosynthesis and evaluation of novel [99mTc(I)]+ and [99mTc(I)(CO)3]+ complexes with a 4-nitroimidazole isocyanide for imaging tumor hypoxia

[^99mTc(I)]⁺ and [^99mTc(I)(CO)₃]⁺ complexes with isocyanide exhibit high stability, which makes them suitable platforms to develop novel ^99mTc radiopharmaceuticals. To develop novel ^99mTc radiotracers for imaging hypoxia, in this study, a novel L ligand (4-nitroimidazole isocyanide derivative) was synthesized and labelled using [^99mTc(I)]⁺ core and [^99mTc(I)(CO)₃]⁺ core to produce [^99mTc(L)₆]⁺ and [^99mTc(CO)₃(L)₃]⁺ with high yields. To verify the structure of the ^99mTc complexes, corresponding rhenium analogues were synthesized and characterized. Both of the ^99mTc complexes were stable and hydrophilic. in vitro cellular uptake results showed they could exhibit good hypoxic selectivity. The evaluation of biodistribution in mice bearing S180 tumors indicated both of them could accumulate in tumor. Between them, [^99mTc(L)₆]⁺ exhibited higher tumor uptake and tumor/non-target ratio than [^99mTc(CO)₃(L)₃]⁺. Further, single photon emission computed tomography (SPECT) imaging studies of [^99mTc(L)₆]⁺ indicated an obvious accumulation in tumor and the value of the region-of-interest (ROI) ratio of the uptake for the tumor site to the corresponding non-tumor region was 5.64 ± 0.52. The above results suggested [^99mTc(L)₆]⁺ would be a potential tracer for imaging tumor hypoxia.     

Formulation of a freeze-dried kit for the preparation of <Superscript>99m</Superscript>Tc-tetrofosmin

A new formulation of a freeze-dried kit for the labeling of tetrofosmin with technetium-99m has been developed. The kit contains lyophilized mixture of 0.320 mg tetrofosmin [6,9-bis(2-ethoxyethyl)-3,12-dioxa-6,9-diphosphatetradecane], 0.025 mg stannous chloride dihydrate, 5 mg sodium tartrate and 5 mg sodium hydrogen carbonate. The product contains no antimicrobial preservative. When ^99mTc pertechnetate up to 6 mL saline containing 200 mCi is added to lyophilized mixture, a lipophilic, cationic ^99mTc complex is formed, ^99mTc-tetrofosmin. The performance of newly developed kit is compared with commercially available MYOVIEW kit for heart imaging. The patient studies show that the images of heart obtained by ^99mTc-tetrofosmin prepared by new formulation are equally good to MYOVIEW.     

Synthesis and preclinical pharmacological evaluation of a novel 99mTc–shikonin as a potential tumor imaging agent

Shikonin was isolated from Ratanjot pigment then the obtained shikonin was well characterized. This study is aimed to optimize radiolabeling yield of shikonin with ^99mTc with respect to factors that affect the reaction conditions such as shikonin amount, SnCl₂·2H₂O amount, reaction time and pH of the reaction mixture. In vitro stability of the radiolabeled complex was checked and it was found to be stable for up to 6?h. Biodistribution studies showed that, ^99mTc?Cshikonin accumulate in tumor sites with higher T/NT than other currently available ^99mTc(CO)₃-VIP, ^99mTc?Cnitroimidazole analogues and ^99mTc?Cpolyamine analogues indicating that shikonin deliver ^99mTc to the tumor sites with a percentage sufficient for imaging and can overcome many drawbacks of other radiopharmaceuticals used for tumor imaging.     

Synthesis, Radiolabelling and in vitro Stability Study of 99mTc(CO)+3 Labeled Dendrimer PAMAM-Folic Acid Conjugate

Dendrimer polyamidoamine generation five‐folic acid conjugate was synthesesed and radiolabelled with fac‐[^99mTc(CO)₃(H₂O)₃]⁺, its in vitro stability was evaluated further. Both of the labeling yield and radiochemical purity of the G5‐FA‐DTPA‐^99mTc(CO)₃ conjugate exceeded 95%. More than 95.7% and 93.1% of the conjugate still keeps its original structure in PBS and new‐born calf serum solution respectively.     

Preparation and biological distribution of 99mTc-cefazolin complex, a novel agent for detecting sites of infection

The optimization of the radiolabeling yield of cefazolin with ^99mTc was described. Dependence of the labeling yield of ^99mTc-cefazolin complex on the amounts of cefazolin and SnCl₂·2H₂O, pH and reaction time was studied. Cefazolin was labeled with ^99mTc with a labeling yield of 89.5 % by using 1 mg cefazolin, 5 μg SnCl₂·2H₂O at pH 4 and 30 min reaction time. The radiochemical purity of ^99mTc-cefazolin was evaluated with ITLC. The formed ^99mTc-cefazolin complex was stable for a time up to 3 h, after that the labeling yield decreased 64.0 % at 8 h. Biological distribution of ^99mTc-cefazolin complex was investigated in experimentally induced inflammation mice, in the left thigh, using Staphylococcus aureus (bacterial infection model) and turpentine oil (sterile inflammation model). Both thighs of the mice were dissected and counted and the ratio of bacterial infected thigh/contralateral thigh was then evaluated. In case of bacterial infection, T/NT for ^99mTc-cefazolin complex was 8.57 ± 0.4 after 0.5 h, which was higher than that of the commercially available ^99mTc-ciprofloxacin under the same experimental conditions. The ability of ^99mTc-cefazolin to differentiate between septic and aseptic inflammation indicates that ^99mTc-cefazolin could undergo further clinical trials to be used for imaging sites of infection.     

Development of electrochemical labelling procedures using MEK extracted99mTc

Electrolytic labelling procedures have been reported for various^99mTc radiopharmaceuticals which differ widely in the choice of the electrodes, working pH, applied voltage and the quantity of current passed. The authors have studied the electrolytic labelling of^99mTc EHDP, gluconate and glucoheptonate with MEK extracted^99mTc using tin electrodes under different experimental conditions. The results have, shown that these compounds can be efficiently labelled with^99mTc in a single step procedure avoiding multiple pH adjustments. Labelling of human serum albumin microspheres suitable for lung imaging with^99mTc by the electrolytic method is also reported.     

99mTc-labelled compounds prepared with tungsten(III) as the reducing agent

The application of K₃W₂Cl₉ as reducing agent in preparation of^99mTc-labelled compounds is described. Pertechnetate reduction was carried out in solutions of pH 2 and also of pH 5.5. DTPA, citrate, gluconate, HEDSPA and MDP were successfully labelled. Two types of labelled gluconate complexes were obtained. Complex I exhibited in rats an increased^99mTc affinity to kidneys (21%). Complex II exhibited an increased^99mTc affinity to bone (8.7%). Two types of labelled HEDSPA preparations were obtained: one yielded 29%^99mTc activity in bone, the other type exhibited only 13.4%. The results indicated the absence of mixed complexes.