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.     

A perspective on <Superscript>99m</Superscript>Tc and <Superscript>125/131</Superscript>I labeled receptor targeted compounds and their in vitro/in vivo affinities

A novel quinoline derivative, 2,2′-[(5-chloro-8-hydroxyquinoline-7-yl) methylazanediyl] diacetic acid (CHQMADA) was labeled with ^99mTc using SnCl₂·2H₂O as a reducing agent to give a complex with a labeling yield 94 %. Also [^99mTc(H₂O)₃(CO)₃]⁺ was prepared by heating at 100 °C for 30 min using 2 mg CHQMADA at pH 8 to give a labeling yield >99 %. ^99mTc-(CO)₃ CHQMADA and ^99mTc-Sn(II)-CHQMADA showed tissue uptake (target to non target T/NT = 6.80 ± 0.22) and (T/NT = 5.65 ± 0.34) respectively in Escherichia coli induced infection, which is higher than the commercially available ^99mTc-ciprofloxacin (T/NT = 3.80 ± 0.80). In conclusion, both complexes were able to differentiate between septic and aseptic inflammation with superiority of [^99mTc-(CO)₃ CHQMADA].     

Study on the preparation and biological evaluation of <Superscript>99m</Superscript>Tc–gatifloxacin and <Superscript>99m</Superscript>Tc–cefepime complexes

The aim of this work is the development of new radiopharmaceuticals for imaging infection and inflammation in human. Gatifloxacin (fluoroquinolone derivative) and cefepime (cephalosporine derivative) are antibiotics used to treat bacterial infections were investigated to label with one of the most important radioactive isotopes (technetium-99m). The reaction parameters that affect the labeling yield such as substrate concentration, stannous chloride dihydrate concentration, pH of the reaction mixture, and reaction time were studied to optimize the labeling conditions. Maximum radiochemical yield of ^99mTc–gatifloxacin (90  ± 1.8%) complex was obtained by using 50 μg SnCl₂·2H₂O and 2.5 mg gatifloxacin at pH 10 while ^99mTc–cefepime was prepared at pH 8 with a maximum radiochemical yield of 98  ± 1.4% by adding ^99mTc to 5 mg cefepime in the presence of 50 μg SnCl₂·2H₂O. Biological distribution of ^99mTc–gatifloxacin and ^99mTc–cefepime was carried out in experimentally induced infection rats, in the left thigh, using Escherichia coli. Both thighs of the rats were dissected and counted and the ratio of bacterial infected thigh/contralateral thigh was then evaluated. T/NT for both ^99mTc–gatifloxacin and ^99mTc–cefepime was found to be 4.5  ± 0.3 and 8.4  ± 0.1, respectively, which was higher than that of the commercially available ^99mTc–ciprofloxacin. The abscess to normal muscle ratio indicated that ^99mTc–cefepime could be used for infection imaging. Besides, in vitro studies showed that ^99mTc–cefepime can differentiate between bacterial infection and sterile inflammation.     

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.     

Labeling and biodistribution of 99mTc-7-bromo-1,4-dihydro-4-oxo-quinolin-3-carboxylic acid complex

7-Bromo-1,4-dihydro-4-oxo-quinolin-3-carboxylic acid (BDOQCA), was synthesized with a yield of 93% and well characterized. The obtained compound was investigated to label with one of the most important radioactive isotopes (technetium-99m). Effect of BDOQCA concentration, stannous chloride dihydrates (SnCl₂.2H₂O) concentration, pH and reaction time on the percent labeling yield of ^99mTc-BDOQCA complex was studied in details. ^99mTc-BDOQCA complex was obtained at a maximum yield of 97.3% by mixing 2.5 mg of BDOQCA with 25 μg SnCl₂.2H₂O at pH 6 and 30 min reaction time and the formed complex was stable for a time up to 8 h with a maximum yield of 97.3%. Biodistribution studies in mice were carried out using experimentally induced infection in the left thigh using E. coli. Both thighs of the mice were dissected and counted to evaluate the ratio of bacterial infected thigh/contralateral thigh. Higher uptake in the infected thigh was observed after 2 h of IV administration of ^99mTc-BDOQCA complex (T/NT = 7.6 ± 0.6%) than that of the commercially available ^99mTc-ciprofloxacin complex (T/NT = 3.8 ± 1%). The in vitro binding and biodistribution of ^99mTc-BDOQCA complex in the septic and aseptic inflammation bearing mice showed that, ^99mTc-BDOQCA complex is a promising agent for infection imaging and can differentiate between infected and inflamed muscle.     

99mTc-ceftriaxone, as a targeting radiopharmaceutical for scintigraphic imaging of infectious foci due to Staphylococcus aureus in mouse model

^99mTc-labeled antibiotics have opened an exciting field of research in infectious diseases diagnosis. Direct labeling of ceftriaxone with ^99mTc was carried out using the various amounts of ceftriaxone and SnCl₂·2H₂O at different pH and incubation time intervals to find the highest radiochemistry efficiency with high stability at room temperature and human blood serum. ITLC-SG and HPLC were performed to measure the radiochemical purity of the conjugate. The binding study showed 45 % specific binding to Staphylococcus aureus. The biodistribution study and scintigraphic imaging showed the localization of ^99mTc-ceftriaxone at the site of infection in comparison with normal and inflamed muscles with high sensitivity and specificity in mouse model. The results showed that ^99mTc-ceftriaxone is a promising candidate as a targeting radiopharmaceutical for Staphylococcal infection imaging in humans which needs further investigations.     

Synthesis,radiochemical and biological characteristics of <Superscript>99m</Superscript>Tc-8-hydroxy-7-substituted quinoline complex: a novel agent for infection imaging

2,2′-[(8-hydroxyquinolin-7-yl)methylazanediyl]diacetic acid (HQMADA) was synthesized via reaction of 8-hydroxyquinoline with iminodiacetic acid in presence of paraformaldehyde with a yield of 27%. The obtained compound was well characterized via different analytical techniques. Labeling of the synthesized compound with technetium-99m in pertechnetate form (^99mTcO₄ ⁻) in the presence of stannous chloride dihydrate was carried out via chelation reaction. The reaction parameters that affect the labeling yield such as HQMADA concentration, stannous chloride dihydrate concentration, pH of the reaction mixture, and reaction time were studied to optimize the labeling conditions. Maximum radiochemical yield of ^99mTc-HQMADA complex (91.9%) was obtained by using 1.5 mg HQMADA, 50 μg SnCl₂·2H₂O, pH 8 and 30 min reaction time. Biodistribution studies in mice were carried out in experimentally induced infection in the left thigh using E. coli. ^99mTc-HQMADA complex showed higher uptake (T/NT = 5.5 ± 0.3) in the infectious lesion than the commercially available ^99mTc-ciprofloxacin (T/NT = 3.8 ± 0.8). Biodistribution studies for ^99mTc-HQMADA complex in Albino mice bearing septic and aseptic inflammation models showed that ^99mTc-HQMADA complex able to differentiate between septic and aseptic inflammation.     

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.     

<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.     

Preparation of 99mTc-cefoperazone complex, a novel agent for detecting sites of infection

Prompt localization of infection sites is essential for initiating appropriate therapeutic measures. There have been major advances in the management of patients suffering from infective and/or inflammatory disorders as a result of introduction of newer drugs with high sensitivity and specificity. Since the last decade, ^99mTc-ciprofloxacin was used as a biologically active radiopharmaceutical to diagnose inflammation but it has some problems related to radiochemical purity and stability. The aim of this study is to develop simple and easy formulation of cefoperazone (other broad spectrum antimicrobial agent) with ^99mTc a ready to use labeling kit for infection imaging. The optimum condition that gives high labeling yield of ^99mTc-cefoperazone complex, 97.9%, was achieved by using 3 mg cefoperazone, 100 μg Sn(II), at pH 8 and 10-minute reaction time. For in vivo binding of ^99mTc-cefoperazone pharmacokinetic studies were carried in experimentally induced infection, in the left thigh, using Staphylococcus aureus in rats. Both thighs of the rats were dissected and counted and the ratio of bacterial infected thigh/contralateral thigh was then evaluated. The time for maximum accumulation of ^99mTc-cefoperazone at the site of infection (T/NT = 4.5) was 45-minute post intravenous injection, followed by gradual decline. So, ^99mTc-cefoperazone complex is simple and stable preparation for infection imaging after 45-minute post injection.     

Optimization of the reaction conditions for the preparation of 99mTc-celecoxib and its biological evaluation

Celecoxib was labelled effectively with ^99mTc. The labeling yield was found to be influenced by the amount of celecoxib, the amount of stannous chloride dihydrate, the reaction time, the temperature and the pH of the reaction mixture. The importance of stannous chloride dihydrate arises from its function as a reducing agent for pertechnetate to form complex celecoxib. The suitable amount required to produce high labeling yield of ^99mTc-celecoxib was 500 μg SnCl₂·2H₂O. The pH of the reaction medium was found to play a significant role in this labeling process. The labeling reaction was performed at a neutral medium (pH 7). The labeling reaction proceeds well at room temperature (25 ± 1 °C) and the complex decomposes by heat. The labeled celecoxib (^99mTc-celecoxib) showed a good localization in inflamed foci and a good imaging must be taken 4 h post injection.     

Synthesis, biodistribution and evaluation of 99mTc-sitafloxacin kit: a novel infection imaging agent

Radiosynthesis of ^99mTc-sitafloxacin (^99mTc-STF) complex and its efficacy as a potential infection imaging agent was evaluated. Effect of sitafloxacin (STF) concentration, sodium pertechnetate (Na^99mTcO₄), stannous chloride dihydrate (SnCl₂·2H₂O), and pH on the % radiochemical purity yield (RCP) of ^99mTc-STF complex was studied. A stable ^99mTc-STF complex up to 120 min with maximum %RCP yield was observed by mixing 2 mg of STF with 3 mCi of Na^99mTcO₄ and 150 μL of SnCl₂·2H₂O (1 μg/μL in 0.01 N HCl) at a pH 5.5. Artificially infected rats with Staphylococcus aureus were used for studying the biodistribution behavior of the ^99mTc-STF complex. After 30 min of the intravenous (I.V.) administration of the ^99mTc-STF complex, 7.50 ± 0.10% was absorbed in the infected thigh of the rats and the uptake gradually increased to 18.50 ± 0.20% within 90 min. Rabbits with artificially induced infection were used for evaluating the scintigraphic accuracy. Higher uptake in the infected thigh was observed after 2 h of I.V. administration of the ^99mTc-STF complex. Target to non-target organ ratio of the % absorbed dose incase of infected/normal muscle was 6.82 ± 0.40, 17.11 ± 0.60, and 23.13 ± 1.00% at 30, 60 and 90 min of administration. Stable and higher %RCP, higher uptake in the infected thigh, and spectral studies, recommend the ^99mTc-STF for routine infection imaging.     

Synthesis of 99mTc-oxybutynin for M3-receptor-mediated imaging of urinary bladder

Radiolabeling of oxybutynin, a muscarinic acetylcholine (mACh) receptor antagonist agent with ^99mTc is of considerable interest for imaging of urinary bladder. This study is aimed to optimize radiolabeling yield of oxybutynin with ^99mTc using SnCl₂·2H₂O as a reducing agent with respect to factors that affect the reaction conditions such as oxybutynin amount, stannous chloride 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 8 h. ^99mTc-oxybutynin was injected via subcutaneous and intravenous administration routes into normal Sprague?CDawley rats. Biodistribution studies have revealed that ^99mTc-oxybutynin exhibits high affinity and specificity for the muscarinic M₃ subtype located on the smooth muscle of urinary bladder relative to the M₁ and M₂ subtypes of the G protein coupled receptor (GPCR) superfamily. In vivo uptake of subcutaneous ^99mTc-oxybutynin in urinary bladder was 19.6 ± 0.42% ID at 0.5 h, whereas in intravenous administration route the accumulation in the urinary bladder was found to be 9.4 ± 0.31% ID at 0.5 h post injection. Administration of cold oxybutynin effectively blocked urinary bladder uptake and further confirms the high specificity of this complex for the M₃ receptor.     

Synthesis of techentium-99m labeled clinafloxacin (99mTc�CCNN) complex and biological evaluation as a potential Staphylococcus aureus infection imaging agent

In the present study synthesis of the ^99mTc?CCNN complex and its efficacy as a prospective Staphylococcus aureus (S. aureus) infection imaging agent was assessed. The ^99mTc?CCNN complex was characterized in terms of stability in saline, serum, in vitro binding with S. aureus and in vivo percent absorption in male Wister rats (MWR) infected with live and heat killed S. aureus. Radiochemically the ^99mTc?CCNN complex showed stable behavior in saline and serum at different intervals. At 30 min after reconstitution the complex showed maximum radiochemical purity (RCP) yield of 97.55 ± 0.22%. The RCP yield decreased to 90.50 ± 0.18% within 240 min. In serum, 18.15% unwanted side product was appeared within 16 h of the incubation. In vitro saturated binding with S. aureus was observed at different intervals with a 62.00% maximum at 90 min. Normal percent in vivo uptake was observed in MWR artificially infected with live S. aureus with a five times higher in the infected muscle as compared to the inflamed and normal muscles. No difference in the percent uptake of the complex in MWR infected with heat killed S. aureus in the infected, inflamed and normal muscles were observed. Based on the promising in vitro and in vivo radiochemical and biological characteristics, we recommend the ^99mTc?CCNN complex for in vivo localization of the S. aureus infectious foci.     

Synthesis and preliminary evaluation of 99mTc-spermine as a tumor imaging agent

Polyamines are essential for the growth and survival of all cells with biosynthesis and transportation of polyamines being very active in tumors. With the aim of developing a new tumor imaging agent, the endogenous polyamine, spermine was labeled with ^99mTc, and its characters were also evaluated via in vitro and in vivo studies. ^99mTc-labeled spermine probe (^99mTc-spermine) was synthesized by the direct pretinning procedure and the labeling procedure was optimized with regard to the pH, reaction time, amounts of spermine and SnCl₂. The stability of the ^99mTc-spermine and its capacity to accumulate into 4T1 tumor cells were also evaluated. Biodistribution of ^99mTc-spermine was studied in 4T1 tumor-bearing mice. In the optimal conditions, the whole radiosynthesis was accomplished within 10 min with a decay-corrected yield of 96.5 ± 1.3 % and radiochemical purity of >95 %.^99mTc-spermine was stable at both 37 and 4 °C for at least 6 h. In vitro tests revealed that the ability of ^99mTc-spermine to penetrate in 4T1 tumour cells and an excess of spermine blocked the accumulation of the compound in the models. Biodistribution studies showed a high tumor uptake peaked at 30 min post-injection with 1.82 ± 0.19 % ID%/g. The tumor to muscle uptake ratios of the probe were 3.60 ± 0.51, 4.48 ± 0.29, 4.82 ± 0.18, 5.64 ± 0.10, respectively at 30 min, 1, 2 and 4 h postinjection. Block studies indicated that ^99mTc-spermine had specific binding of tumor via polyamine transport systems. ^99mTc-spermine is a promising radiopharmaceutical in tumor imaging. Further studies are required to determine the usability of ^99mTc–spermine for diagnosis purposes.     

Synthesis of 99mTc-cationic steroid antimicrobial-107 and in vitro evaluation

Ceragenins/cationic steroid antimicrobials (CSAs) are a group of cholic acid derivatives with many properties that make them favourable for application as anti-infective agents. CSA-107 is also a member of this group that was labelled with ^99mTc by using SnCl₂·2H₂O as reducing agent and Na–K tartrate as transchelating agent. Labelling efficiency was optimized by varying the amount of reducing agent, pH, and time of incubation. Labelling efficiency and the stability of ^99mTc-CSA-107 in human serum was determined by paper and thin layer chromatography, which were >95 and >90 % respectively. In vitro binding of ^99mTc-CSA-107 was >95 % determined by using Staphylococcus aureus bacteria.     

Labeling of scorpion venom with 99mTc and its biodistribution

Labeling of scorpion venom (SV) was successfully achieved with ^99mTc using direct chelating method. Venom was labeled with ^99mTc using stannous chloride as reducing agent. Preliminary studies were done to establish the optimum conditions for obtaining the highest yield of the labeled venom. The labeling technique is effective, as a maximum labeling yield (97 %) was obtained after 30-min reaction time by using 80 μg SV in phosphate buffer of pH 7 and 25 μg Sncl₂·2H₂O at room temperature. Venom was injected into normal mice to determine the excretion pathway. Biodistribution studies in normal mice with SV shows rapid clearance of the venom from blood and tissue except for kidneys. The improvement of the immunotherapeutic treatment of envenomation requires a better knowledge of the biological actions of the SV since tissue distribution studies are very important for clinical purpose.     

Preparation of radioiodinated ritodrine as a potential agent for lung imaging

Ritodrine (a beta-2 adrenergic receptor agonist) was successfully labeled with ¹²⁵I via direct electrophilic substitution reaction at ambient temperature. ¹²⁵I-ritodrine was obtained with a maximum labeling yield of 97 ± 0.163 % and in vitro stability up to 24 h. Biodistribution studies showed that maximum in vivo uptake of ¹²⁵I-ritodrine in lungs was 20.4 ± 0.22 % injected activity/g tissue at 1 h post-injection, whereas the clearance from mice appeared to proceed mainly via the renal pathway. ¹²⁵I-ritodrine is not a blood product and so it is more safe than the currently available ^99mTc-MAA, and its lung uptake is higher than that of the recently discovered ^99mTc(CO)₅I and ^99mTc-DHPM. As a conclusion, radioiodinated ritodrine could be used as a novel radiopharmaceutical for lung perfusion scan safer than the currently available ^99mTc-MAA and more potential than the recently discovered ^99mTc(CO)₅I and ^99mTc-DHPM.     

Biodistribution of ultra small superparamagnetic iron oxide nanoparticles in BALB mice

Recently ultrasmall superparamagnetic iron oxide (USPIO) nanoparticles (NPs) have been widely used for medical applications. One of their important applications is using these particles as MRI contrast agent. While various research works have been done about MRI application of USPIOs, there is limited research about their uptakes in various organs. The aim of this study was to evaluate the biodistribution of dextran coated iron oxide NPs labelled with ^99mTc in various organs via intravenous injection in Balb/c mice. The magnetite NPs were dispersed in phosphate buffered saline and SnCl₂ which was used as a reduction reagent. Subsequently, the radioisotope ^99mTc was mixed directly into the reaction solution. The labeling efficiency of USPIOs labeled with ^99mTc, was above 99 %. Sixty mice were sacrificed at 12 different time points (From 1 min to 48 h post injections; five mice at each time). The percentage of injected dose per gram of each organ was measured by direct counting for 19 harvested organs of the mice. The biodistribution of ^99mTc-USPIO in Balb/c mice showed dramatic uptake in reticuloendothelial system. Accordingly, about 75 percent of injected dose was found in spleen and liver at 15 min post injection. More than 24 % of the NPs remain in liver after 48 h post-injection and their clearance is so fast in other organs. The results suggest that USPIOs as characterized in our study can be potentially used as contrast agent in MR Imaging, distributing reticuloendothelial system specially spleen and liver.