Preparation and bioevaluation of a novel 99mTc-labelled propylene amine oxime (PnAO) containing two 4-methyl-2-nitroimidazole groups as a promising tumor hypoxia imaging agent

Hypoxia is a common phenomenon in solid tumors, and its presence inhibits the efficacy of tumor chemotherapy and radiotherapy. Accurate measurement of hypoxia before tumor treatment is essential. Three propylene amine oxime (PnAO) derivatives with different substituents attached to 2-nitroimidazole were synthesized in the work, they are 3,3,9,9-tetramethyl-1,11-bis(4-bromo-2-nitro-1H-imidazol-1-yl)-4,8-diazaundecane-2,10-dione dioxime (Br2P2), 3,3,9,9-tetramethyl-1,11-bis(4-methyl-2-nitro-1H-imidazol-1-yl)-4,8-diazaundecane-2,10-dione dioxime (Me2P2) and 3,3,9,9-tetramethyl-1,11-bis(4,5-dimethyl-2-nitro-1H-imidazol-1-yl)-4,8-diazaundecane-2,10-dione dioxime (2Me2P2). The three compounds were radiolabeled with 99mTc to give three complexes([99mTc]Tc-Br2P2, [99mTc]Tc-Me2P2 and [99mTc]Tc-2Me2P2) with good in vitro stability. [99mTc]Tc-Me2P2 with a more suitable reduction potential had the highest hypoxic cellular uptake, compared with [99mTc]Tc-2P2 that have been previously reported, [99mTc]Tc-Br2P2 and [99mTc]Tc-2Me2P2. Biodistribution results in S180 tumor-bearing mice demonstrated that [99mTc]Tc-Me2P2 had the highest tumor-to-muscle (T/M) ratio (12.37 ± 1.16) at 2 h in the four complexes. Autoradiography and immunohistochemical staining results revealed that [99mTc]Tc-Me2P2 specifically targeted tumor hypoxic regions. The SPECT/CT imaging results showed that [99mTc]Tc-Me2P2 could target the tumor site. [99mTc]Tc-Me2P2 may become a potential hypoxia imaging agent.

Synthesis and preliminary biological evaluation of a novel 99mTc-labeled small molecule for PD-L1 imaging

In recent years, PD-1/PD-L1 checkpoint blockade immunotherapy with remarkable efficacy has set off a heat wave. The expression level of PD-L1, which plays a predictive role in anti-PD-1/PD-L1 therapy, could be quantified by noninvasive imaging with radiotracers. Herein, we introduced the synthesis and preliminary biological evaluation of a novel 99mTc-labeled small molecule radiotracer [99mTc]G3C-CBM for PD-L1 imaging. [99mTc]G3C-CBM was achieved with high radiochemical purity (>96 %) and remained good stability in PBS and FBS. In competitive combination experiment, [99mTc]G3C-CBM was displaced by increasing concentrations of unlabeled G3C-CBM, resulting in an IC50 value of 41.25±2.23 nM for G3C-CBM. The uptake of [99mTc]G3C-CBM in A375-hPD-L1 cells (17.51±2.08 %) was approximately 6.47 folds of that in A375 cells (2.71±0.36 %) after co-incubation for 2 h. The biodistribution results showed that the radioactivity uptake in A375-hPD-L1 tumor reached the maximum (0.35±0.01 %ID/g) at 2 h post injection, and the optimum tumor/muscle ratio of 2.94±0.29 occurred at the same time. In addition, [99mTc]G3C-CBM was quickly cleared from the blood with a clearance half-life of just 119.25 min. These results indicate that [99mTc]G3C-CBM is a potential SPECT PD-L1 imaging agent and is worthy of further study.

Design, characterization and evaluation of a new 99mTc-labeled folate derivative with affinity towards folate receptor

Folate receptors (FRs) are known to be over-expressed in several human malignancies and therefore serve as an important target for small radiolabeled folate derivatives for non-invasive imaging of tumor, which is an important tool for future treatment recourse. In the present article, we report the synthesis of a new ^99mTc-labeled radiotracer for the aforementioned application following the well-established ^99mTc-'4+1' chemistry. Formation of the desired [^99mTc]Tc-complex with >95% radiochemical purity was confirmed by radio-HPLC and its structure was ascertained by characterizing a natural rhenium analogue of the said complex. Although the ligand exhibited a weaker affinity towards FRs compared to native folic acid (IC50 8.09 µM vs 29.46 nM), the ^99mTc-labeled complex was found to bind folate receptor-positive KB cells with high specificity (∼90%). Similar studies in a folate receptor negative cell line viz. A549 further corroborated the receptor-specificity of the synthesized complex. In vivo studies in KB tumor xenograft showed moderate uptake of ∼2.6% upto 3 h post-injection with high specificity (∼80%). The favorable features observed warrant further screening of the current design towards achieving an improved molecular probe for the said application.

Improving tumor/muscle and tumor/blood ratios of 99mTc-labeled nitroimidazole propylene amine oxime (PnAO) complexes with ethylene glycol linkers

Three nitroimidazole propylene amine oxime (PnAO) derivatives with different lengths of ethylene glycol chain were synthesized and radiolabeled with ^99mTc. The radiochemical purities of three ^99mTc-labeled complexes, oxo[[6,6,12,12-tetramethyl-1,17-bis(2-nitro-1H-imidazol-1-yl)-3,15-dioxa-7,11-diazaheptadecane-5, 13-dione dioximato] (3-)-N,N',N'',N''']-technetium-99m (^99mTc-2P2O1), oxo[[9,9,15,15-tetramethyl-1,23-bis(2-nitro-1H-imidazol-1-yl)-3,6,18,21-tetraoxa-10, 14-diazatricosane-8,16-dione dioximato] (3-)-N,N',N'',N''']-technetium-99m (^99mTc-2P2O2) and oxo[[15,15,21,21-tetramethyl-1,35-bis(2-nitro-1H-imidazol-1-yl)-3,6,9,12,24,27,30,33-octaoxa-16,20-diazapentatriacontane-14,22-dione dioximato] (3-)-N,N',N'',N''']-technetium-99m (^99mTc-2P2O4), were above 90%, and they were all stable both in vitro and in vivo. The hypoxia/normoxia uptake ratios of the three complexes were 2.92 ± 0.61, 2.63 ± 0.64 and 2.29 ± 0.67 in S180 cellular uptake assay (4 h). All of these complexes presented good hypoxia selectivity. The results of biodistribution studies in S180 tumor-bearing mice revealed that the tumor/muscle (T/M) ratios (7.20 ± 2.37, 7.19 ± 1.75, 5.56 ± 1.10) and tumor/blood (T/B) ratios (1.66 ± 0.34, 1.73 ± 0.25, 2.13 ± 0.19) at 4 h of three complexes were significantly higher than those of ^99mTc-2P2 (3.24 ± 0.65, 0.81 ± 0.34) without the ethylene glycol chains. Among them, ^99mTc-2P2O4 had the best T/B ratio. The new complexes have higher tumor/blood and tumor/muscle ratios by adding suitable length of ethylene glycol chain. It is helpful for the design and optimization of hypoxic imaging agents.

Rat thyroid graft transplantation after cryopreservation with scintigraphic standardization for an experimental study

PURPOSE

Budget cuts among other factors undermine the use of state-of-the-art equipment by many research groups. This doesn't mean that their scientific data are not reliable or top-notch. Resort to adaptations is a recurrent need in their reality. The aim of this study was to assess whether scintigraphy with ^99mTcO₄ is effective in evaluating the functionality of thyroid grafts after cryopreservation in rats.

MATERIAL AND METHODS

24 rats were randomly distributed into 3 groups: Control Group (CG), without surgical procedure, Hypothyroidism Group (HTG), submitted to total thyroidectomy, and Transplanted Group (TG), with total thyroidectomy and cryopreservation of the thyroid gland for 7 days followed by grafting of a thyroid lobe. A protocol using a gamma camera imaging was conducted fourteen weeks after transplantation, and the whole body ^99mTc, focusing on the topic of heterotopic thyroid uptake was evaluated.

RESULTS

The images acquired had good quality with no noise and artifacts that could jeopardize its analysis. On the 14th day, HTG displayed no thyroid uptake, and the TG had a clear uptake of the thyroid graft in the topography of the biceps femoris muscle. Presented data also showed that both equipment spatial resolution and alignment (4.375 mm) did not interfere with the physiological uptake of ^99mTc by the thyroid graft.

CONCLUSION

The viability and functionality of cryopreserved thyroid autotransplantation in rats who underwent total thyroidectomy were successfully accessed by the scintigraphy protocol developed.

Evaluation of 99mTc-CN5DG as a broad-spectrum SPECT probe for tumor imaging

Previously, we reported a [^99mTc(ǀ)]⁺ labeled d-glucoamine derivative (^99mTc-CN5DG) and evaluated it as a tumor imaging agent in mice bearing A549 tumor xenografts. In this paper, ^99mTc-CN5DG was further studied in U87 MG (human glioma cells), HCT-116 (human colon cancer cells), PANC-1 (human pancreatic cancer cells) and TE-1 (human esophageal cancer cells) tumor xenografts models to verify its potential application for imaging of different kinds of tumors. The biodistribution data showed that ^99mTc-CN5DG had a similar biodistribution pattern in four tumor models at 2 h post-injection with high accumulation in tumors and kidneys. The tumor/muscle ratios (from 4.08 ± 0.42 to 9.63 ± 3.53) and tumor/blood ratios (from 17.18 ± 7.40 to 53.17 ± 16.16) of ^99mTc-CN5DG in four tumor models were high. All four kinds of tumors could be clearly seen on their corresponding SPECT/CT images. Pharmacokinetic study in healthy CD-1 mice demonstrated that ^99mTc-CN5DG cleared fast from blood (2 min, 12.97 ± 0.88%ID/g; 60 min, 0.33 ± 0.06%ID/g) and the blood distribution, elimination half-life was 5.81 min and 21.16 min, respectively. No abnormality was observed through the abnormal toxicity study. All of the above results demonstrated that ^99mTc-CN5DG could be a broad-spectrum SPECT probe for tumor imaging and its further clinical application is warranted.

Development of technetium-99m labeled ultrafine gold nanobioconjugates for targeted imaging of folate receptor positive cancers

INTRODUCTION

Strategic design and synthesis of nanoparticle based preparations could improve diagnostic screening of several cancer types, thereby facilitating better clinical management of the disease. Towards this, the present work aims to develop and evaluate a radioactive technetium-99m (^99mTc) labeled gold nanoparticle (NP) preparation modified with folic acid, so as to diagnose folate receptor positive cancers viz. ovarian, breast, etc. METHODS: 11-Bromoundecanoic acid (UA) was synthetically modified both with folic acid and Hydrazinonicotinic acid (HYNIC) chelate at the carboxylic acid end and subsequently converted to thiol functionality at the bromo terminal to yield folic acid-UA-SH and HYNIC-UA-SH ligands respectively. Gold NPs modified with folic acid and HYNIC chelator were obtained on direct addition of folic acid-UA-SH and HYNIC-UA-SH to chloroauric acid in polysorbate 80 solution under reducing conditions. These NPs were then radiolabeled with ^99mTc following HYNIC labeling approach. Both the inactive and ^99mTc-labeled gold NPs were then tested for their biological efficacy in folate receptor (FR) positive KB cancer cell lines. Also, biodistribution studies of ^99mTc-labeled gold NPs were carried in KB tumor xenografts to ascertain the efficacy towards FR in in vivo system.

RESULTS

Polysorbate 80 could stabilize the gold NP preparation with average size <10 nm as determined by TEM. Inhibition of [³H]folic acid with functionalized gold nanoparticle revealed affinity towards FR positive KB cell lines with an IC₅₀ ~ 9 μM. Biodistribution studies of ^99mTc-labeled gold NP preparation in SCID mice bearing KB tumor showed an uptake of 1.39 ± 0.18%ID/g in tumor and 5.48 ± 0.72%ID/g in kidneys at 3 h post-injection. In vivo distribution in folic acid pre-treated animals could not establish the specificity towards folate receptors.

CONCLUSIONS

Biological evaluation of functionalized gold NP showed affinity towards FR positive cancer cell lines. ^99mTc-labeled NP exhibited target uptake in both in vitro and in vivo models, but folic acid inhibition could not establish the target specificity. Nevertheless, in vivo pharmacokinetics envisaged in the present design was achieved using the present gold functionalized NP preparation.

Synthesis and evaluation of [99mTcN]2+ core and [99mTcO]3+ core labeled complexes with 4-nitroimidazole xanthate derivative for tumor hypoxia imaging

A 4-nitroimidazole xanthate ligand (NMXT) was synthesized and radiolabeled with [^99mTcN]²⁺ core and [^99mTcO]³⁺ core to obtain ^99mTcN-NMXT and ^99mTcO-NMXT, respectively. The two ^99mTc-complexes were prepared with high radiochemical purity and had good stability. The partition coefficient results indicated both of them were hydrophilic, and cellular uptake studies showed they exhibited good hypoxic selectivity. From the biodistribution study results, ^99mTcO-NMXT showed more favourable tumor uptake (1.73 ± 0.14 ID%/g) and higher tumor/muscle ratio (7.01 ± 0.16) than ^99mTcN-NMXT at 4 h post-injection. Single photon emission computed tomography (SPECT) imaging study of ^99mTcO-NMXT showed there was a visible accumulation in tumor site, suggesting it would be a promising candidate as a tumor hypoxia imaging agent.

Preparation and assessment of a new radiotracer technetium-99m-6-hydrazinonicotinic acid-tyrosine as a targeting agent in tumor detecting through single photon emission tomography

The goal of investigation was to bring up an impressive way to synthesize technetium-99 m-6-hydrazinonicotinic acid-tyrosine (^99mTc-HYNIC-Tyr), a newfound radiotracer, and to assess the capacity of being as a tumor scintigraphy agent. The conjugate was prepared by solid phase method using tritely chloride resin. The precursor HYNIC-Tyr was labeled with ^99mTc which was accomplished at 100 °C through the coligands tricine and EDDA. Furthermore, the serum albumin binding, cellular attachment, organs uptake and tumor accumulation were measured. C6 glioma cells were used for cellular and tumor uptake studies. ^99mTc-HYNIC-Tyr was prepared with labeling yield of >99% (n = 3). Radiotracer showed stability in serum proteins in incubates temperature. Specific cellular attachment of radiotracer was noticeable in C6 glioma cells with dissociation constant in nano molar range (21.03 ± 1.54 nM). The amount of uptake in C6 rat glioma xenograft was 2.61 ± 0.12 percent of injection dose per gram after 30 min. In whole-body scintigraphy, C6 glioma tumor was easy to be traced and interpreted at 1 h after administration of radiotracer. Our data suggest that ^99mTc-HYNIC-Tyr, a new radiotracer based on amino acid, efficiently differentiates the tumor cells and goes into them. Our results indicate that this radiotracer has excellent capacity to detect tumor cells in rat and to be included as a radiopharmaceutical for detecting cancer tumors.

Aryl isocyanide derivative for one-pot synthesis of purification-free 99mTc-labeled hexavalent targeting probe

INTRODUCTION

^99mTc-labeled hexavalent probes can be readily synthesized by the coordination of six equivalent isocyanide ligands towards Tc^I, and alkyl isocyanide ligands have been extensively used for preparing such probes. However, high ligand concentration (>1 mM) is generally required due to their insufficient coordination ability to Tc^I.

METHODS AND RESULTS

In this study, we revealed that aryl isocyanide ligands, which have greater π-accepting ability compared with alkyl ones, provided ^99mTc-labeled hexavalent probes in high radiochemical yields (>95%) even at low ligand concentration (50 μM). We applied this finding to the synthesis of a ^99mTc-labeled hexavalent RGD probe, targeting integrin α_vβ₃. This ^99mTc-labeled probe was prepared in a 5 min reaction at ligand concentration of 50 μM, and exhibited high tumor localization in vivo without post-labeling purification.

CONCLUSION

The present findings indicate that aryl isocyanide ligands would be a useful precursor to a variety of ^99mTc-labeled hexavalent targeting probes for molecular imaging of saturable systems.

ADVANCES IN KNOWLEDGE

Aryl isocyanide is a better precursor than alkyl isocyanide for preparing ^99mTc-labeled hexavalent targeting probe.

IMPLICATION FOR PATIENT CARE

This work provides a straightforward method to prepare molecular imaging agents of high target uptake, which would facilitate nuclear medicine imaging in clinical settings.

Preparation, radiolabeling with 99mTc and 67Ga and biodistribution studies of albumin nanoparticles covered with polymers

OBJECTIVE

To optimize radiolabeling with ^99mTc and ⁶⁷Ga of albumin nanoparticles coated with 4 differents synthetic polymers and to evaluate their stability in vivo and in vitro, as well as their biodistribution in vivo after intravenous administration.

MATERIAL AND METHODS

The nanoparticles were prepared using albumin and NOTA-modified albumin by the desolvation method and coated with 4 different polymers; HPMC, GMN2, GPM2 and GTM2. They were purified, lyophilized and characterized. Radiolabelling with ^99mTc was perfomed with 74 MBq of ^99mTc sodium pertechnetate, previously reduced with and acid solution of tin chloride at different concentrations (0.003, 0.005, 0.007, 0.01, 0.05 and 0.1mg/ml) and at different times (5, 10, 15, 30 and 60minutes) and temperatures (room temperature, 40°C and 60°C). Radiolabelling with ⁶⁷Ga was perfomed by incubation of the nanoparticles with 37 MBq of ⁶⁷Gallium chloride (obtained from commercial gallium-⁶⁷ citrate) at different times (10 and 30minutes) and temperatures (room temperature, 30°C and 60°C), and posterior purification with microconcentrators. The radiochemical purity was evaluated by TLC. Stability studies of radiolabeled nanoparticles in physiological serum and blood plasma were perfomed. Biodistribution studies of nanoparticles coated with GPM2 polymer were carried out in Wistar rats after intravenous administration of the nanoparticles. Control animals were carried out with ^99mTc sodium pertechnetate and ⁶⁷Ga chloride. To do so, the animals were killed and activity in organs was measured in a gamma counter.

RESULTS

^99mTc labeling was carried out optimally with a tin concentration of 0.007mg/ ml for the GPM2 nanoparticles and 0.005mg / ml for the rest of the formulations, with a radiolabelling time of 10minutes at room temperature. In the case of ⁶⁷Ga the label was optimized at 30° C temperature and 30minutes of incubation. In both cases the radiochemical purity obtained was greater than 97%. The nanoparticles showed high stability in vitro after 48hours of labeling (70% nanoparticles labeled with ^99mTc and 90% those labeled with ⁶⁷Ga). Biodistribution studies of nanoparticles ^99mTc -GPM2 and ⁶⁷Ga -NOTA-GPM2 showed a high accumulation of activity in the liver at 2 and 24hours after intravenous administration.

CONCLUSION

The labeling procedure with ^99mTc and ⁶⁷Ga of albumin and albumin modified with NOTA nanoparticles allows obtaining nanoparticles with high labeling yields and adequate in vitro stability, allowing their use for in vivo studies.

99mTc-radiolabeled HER2 targeted exosome for tumor imaging

Exosomes represent unique features including nontoxicity, non-immunogenicity, biodegradability, and targeting ability that make them suitable candidates for clinical applications. Therefore, in this study, ^99mTc-radiolabel HER2 targeted exosomes (^99mTc-exosomes) were provided for tumor imaging. These exomes are obtained from genetically engineered cells and possessed DARPin G3 as a ligand for HER2 receptors. These exosomes were radiolabeled using fac-[^99mTc(CO)₃(H₂O)₃]⁺ synthon. The quality control showed high radiochemical purity (RCP) for ^99mTc-exosomes (>96%). ^99mTc-exosomes displayed a higher affinity toward SKOV-3 cells (higher HER2 expression) in comparison with MCF-7, HT29, U87-MG, A549 cell lines at different levels of HER2 expression. Trastuzumab (an antibody with a high affinity toward HER2) inhibited the binding of ^99mTc-exosomes to SKOV-3 cells up to 40%. Biodistribution study in SKOV-3 tumor bearing nude mice confirmed the ability of ^99mTc-exosomes for accumulation in the tumor. ^99mTc-exosomes can visualize tumor in SKOV-3 tumor-bearing nude mouse. The blockage of HER2 receptors using trastuzumab (excessive amount) suggests the ^99mTc-exosomes binding to the receptors and reduced the accumulation of ^99mTc-exosomes in the tumor site. This suggest that ^99mTc-exosomes interact with HER2 receptors and act through specific targeting.

Preparation and evaluation of 99mTc-labeled HYNIC-palbociclib analogs for cyclin-dependent kinase 4/6-positive tumor imaging

Overexpression and amplification of cyclin-dependent kinase 4/6 (CDK4/6) occur in many cancers and may be the cause of resistance to CDK4/6 inhibitors in preclinical models. However, there are few investigations on the assessment of CDK4/6 expression in tumors or other tissues. Palbociclib, which was approved in 2015 to treat ER+/HER2-breast cancer in combination with letrozole, is a selective CDK4/6 inhibitor. In this study, an intermediate (compound 3), which could be hydrolyzed into the ligand (compound L) consisting of palbociclib as the bioactive molecule and 6-hydrazino nicotinamide (HYNIC) as the bifunctional chelator, was synthesized. Compound L was radiolabeled with ^99mTc using tricine/TPPTS or tricine/TPPMS as co-ligands. ^99mTc-tricine-TPPTS-L and ^99mTc-tricine-TPPMS-L were prepared with high radiochemical purity without postlabeling purification. They had great in vitro stability. Both radiotracers were hydrophilic, but ^99mTc-tricine-TPPTS-L had a lower log P value. In vitro cell uptake studies in MCF-7 cells showed that cellular uptake was blocked by preincubation with palbociclib, suggesting a CDK4/6-mediated uptake mechanism. Biodistribution in mice bearing MCF-7 tumors showed that ^99mTc-tricine-TPPTS-L had higher tumor uptake than ^99mTc-tricine-TPPMS-L, while they had comparable tumor-to-muscle and tumor-to-blood ratios. Radioactivity accumulation in tumors was obvious in micro-SPECT/CT images with ^99mTc-tricine-TPPTS-L. When mice were preinjected with palbociclib, tumor uptake of ^99mTc-tricine-TPPTS-L significantly decreased and the tumor accumulation was clearly lost, confirming CDK4/6 specificity. All results in this work indicated that ^99mTc-tricine-TPPTS-L is a promising tumor imaging agent that targets CDK4/6.

Fabrication of miniature 141Ce sources by chemical deposition towards possible use in the performance evaluation of gamma cameras - A feasibility study

¹⁴¹Ce sources were fabricated for quality assurance of gamma cameras. The fabrication process consisted of electro-deposition of Ni on a Cu sphere in 0.01 N H₂SO₄ containing 30 mg/mL H₃BO₃ and 50 μg of NiSO₄·7H₂O at pH 2-3 followed by deposition of ¹⁴¹Ce on it. > 95% deposition of ¹⁴¹Ce on substrate could be achieved at pH 5. Source core was loaded in custom-made Al holder. Autoradiography confirmed uniform activity distribution. SEM and EDS analyses confirmed deposition of Cerium on substrate.

Synthesis, characterization and biological studies of rhenium, technetium-99m and rhenium-188 pentapeptides

A pentapeptide macrocyclic ligand, KYCAR (lysyl-tyrosyl-cystyl-alanyl-arginine), has been designed as a potential chelating ligand for SPECT imaging and therapeutic in vivo agents. This study shows the synthesis and characterization of KYCAR complexes containing nonradioactive rhenium, ^99mTc, or ¹⁸⁸Re. The metal complexes were also biologically evaluated to determine in vivo distribution in healthy mice. The overall goals of this project were (1) to synthesize the Tc/Re pentapeptide complexes, (2) to identify spectroscopic methods for characterization of syn versus anti rhenium peptide complexes, (3) to analyze the ex vivo stability, and (4) to assess the biological properties of the [^99mTc]TcO-KYCAR and [¹⁸⁸Re]ReO-KYCAR complexes in vivo. Details on these efforts are provided below.

METHODS

^NatRe/^99mTc/¹⁸⁸ReO-KYCAR complexes were synthesized, and macroscopic species were characterized via HPLC, IR, NMR, and CD. These characterization data were compared to the crystallographic data of ReO-KYC to assist in the assignment of diastereomers and to aid in the determination of the structure of the complex.

RESULTS

The radiometal complexes were synthesized with high purity (>95%). HPLC, IR, NMR and CD data on the macroscopic ^natReO-KYCAR complexes confirm the successful complexation as well as the presence of two diastereomers in syn and anticonformations. Tracer level complexes show favorable stabilities ex vivo for 2+ h.

CONCLUSION

Macroscopic metal complexes form diastereomers with the KYCAR ligand; however, this phenomenon is not readily observed on the tracer level due to the rapid interconversion. It was determined through pK_a measurements that the macroscopic ^natReO-KYCAR complex is 0 at physiological pH. The [^99mTc]TcO-KYCAR is stable in vitro while the [¹⁸⁸Re]ReO-KYCAR shows 50% decomposition in PBS and serum. Biologically, the tracer level complexes clear through the hepatobiliary pathway. Some decomposition of both tracers is evident by uptake in the thyroid and stomach.

Non-dependence of nuclear decay rates of 123I and 99mTc on Earth-Sun distance

Recently published studies have suggested an annual fluctuation of the decay rate of several radionuclides, in particular ³²Si and ²²⁶Ra. Variation of solar neutrino flux caused by variation of Earth-Sun distance has been proposed as the mechanism of this fluctuation. In this study we prospectively look at two radionuclides which have not previously been studied for annual variation, ¹²³I and ^99mTc. Half-lives of samples of these radionuclides were measured approximately weekly and semiweekly respectively over a period of 2 years. Spectral analysis using the Lomb-Scargle method demonstrated no significant periodicity, and in particular, no evidence for a period of 1 year.

Cyclotron production of 99mTc: Comparison of known separation technologies for isolation of 99mTc from molybdenum targets

Intensive efforts were undertaken during the last few decades for the separation of cyclotron-produced ^99mTc from ⁹⁹Mo and new papers have been published on this topic since the last review [1]. In the future the cyclotron-based methods can replace reactor-based technology in producing this medical radioisotope and the nuclear reaction ¹⁰⁰Mo(p,2n)^99mTc appears to be the most worthwhile approach. New ways of producing of ^99mTc require efficient separation methods. Several strategies for separation of ^99mTc from ⁹⁹Mo have been already developed. The advantages, disadvantages and technical challenges toward application potential of investigated methods to separate ^99mTc from irradiated ¹⁰⁰Mo target are discussed. These methods include column chromatography, solvent extraction, chemical precipitation and thermochromatography.

Manufacturing and characterization of molybdenum pellets used as targets for 99mTc production in cyclotron

The method of ¹⁰⁰Mo metallic target preparation for production of ^99mTc by proton irradiation in ¹⁰⁰Mo(p,2n)^99mTc reaction was demonstrated. For this purpose, pressing of molybdenum powder into pellets and their subsequent sintering in reductive atmosphere were applied. The influence of parameters such as molybdenum mass and time of both pressing and sintering on the ¹⁰⁰Mo target durability was investigated. Under the optimized conditions, ¹⁰⁰Mo metallic pellet targets with density of 9.95±0.06g/cm³ were obtained. Morphology and structure of pressed pellets before and after sintering were studied by using standard optical microscope and Scanning Electron Microscope (SEM). Nanoindentation technique was used to investigate the mechanical properties such as nanohardness and Young modulus. Prepared ¹⁰⁰Mo pellets were successfully irradiated with protons and ^99mTc was efficiently isolated.

Radiolabeling and biological characterization of TPGS-based nanomicelles by means of small animal imaging

INTRODUCTION

In recent years, nanomedicines have raised as a powerful tool to improve prevention, diagnosis and treatment of different pathologies. Among the most well investigated biomaterials, D-α-tocopheryl polyethylene glycol succinate (also known as TPGS) has been on the spot for the last decade. We therefore designed a method to biologically characterize TPGS-based nanomicelles by labeling them with ^99mTc.

METHODS

Labeling process was performed by a direct method. The average hydrodynamic diameter of TPGS nanomicelles was measured by dynamic light scattering and radiochemical purity was assessed by thin layer chromatography. Imaging: a dynamic study was performed during the first hour post radioactive micelles administration in a gamma camera (TcO₄^- was also administered for comparative purposes). Then two static images were acquired in ventral position: 1h and 12h post injection. Blood pharmacokinetics of ^99mTc-TPGS during 24h was performed.

RESULTS

Images revealed whole body biodistribution at an early and delayed time and semiquantification was performed in organs of interest (%Total counts: soft tissue 6.1±0.5; 3.9±0.1, Bone 1.2±0.2; 1±0.1, Heart 1.5±0.6; 0.7±0.3, Kidneys 16.6±1.3; 26.5±1.7, Liver 8.6±1.1; 11.1±0.1 for 1 and 12 h post injection respectively).

CONCLUSION

This work demonstrated that TPGS based nanomicelles are susceptible to be radiolabeled with ^99mTc thus they can be used to perform imaging studies in animal models. Moreover radiolabeling of these delivery nano systems reveals their possibility to be used as diagnostic agents in the near future.

Melanoma targeting with [99mTc(N)(PNP3)]-labeled α-melanocyte stimulating hormone peptide analogs: Effects of cyclization on the radiopharmaceutical properties

The purpose of this study was to evaluate the effect of cyclization on the biological profile of a [^99mTc(N)(PNP3)]-labeled α-melanocyte stimulating hormone peptide analog. A lactam bridge-cyclized H-Cys-Ahx-βAla³-c[Lys⁴-Glu-His-D-Phe-Arg-Trp-Glu¹⁰]-Arg¹¹-Pro-Val-NH₂ (NAP-NS2) and the corresponding linear H-Cys-Ahx-βAla-Nle-Asp-His-D-Phe-Arg-Trp-Gly-NH₂ (NAP-NS1) peptide were synthetized, characterized by ESI-MS spectroscopy and their melanocortin-1 receptor (MC1R) binding affinity was determined in B16/F10 melanoma cells. The consistent [^99mTc(N)(PNP3)]-labeled compounds were readily obtained in high specific activity and their stability and biological properties were assessed. As an example, the chemical identity of [^99mTc(N)(NAP-NS1)(PNP3)]⁺ was confirmed by carrier added experiments supported by radio/UV HPLC analysis combined with ESI(+)-MS. Compared with the linear peptide, cyclization negatively affected the biological properties of NAP-NS2 peptide by reducing its binding affinity for MC1R and by decreasing the overall excretion rate of the corresponding [^99mTc(N)(PNP3)]-labeled peptide from the body as well as its in vivo stability. [^99mTc(N)(NAP-NS1)(PNP3)]⁺ was evaluated for its potential as melanoma imaging probe in murine melanoma model. Data from in vitro and in vivo studies on B16/F10 melanoma model of [^99mTc(N)(NAP-NS1)(PNP3)]⁺ clearly evidenced that the radiolabeled linear peptide keeps its biological properties up on the conjugation to the [^99mTc(N)(PNP3)]-building block. The progressive increase of the tumor-to-nontarget ratios over the time indicates a quite stable interaction between the radio-complex and the MC1R.

Characterization of TCP-1 probes for molecular imaging of colon cancer

Molecular probes capable of detecting colorectal cancer (CRC) are needed for early CRC diagnosis. The objective of this study was to characterize c[CTPSPFSHC]OH (TCP-1), a small peptide derived from phage display selection, for targeting human CRC xenografts using technetium-99m ((99m)Tc)-labeled TCP-1 and fluorescent cyanine-7 (Cy7)-labeled form of the peptide (Cy7-TCP-1). (99m)Tc-TCP-1 was generated by modifying TCP-1 with succinimidyl-6-hydrazino-nicotinamide (S-HYNIC) followed by radiolabeling. In vitro saturation binding experiments were performed for (99m)Tc-TCP-1 in human HCT116 colon cancer cells. SCID mice with human HCT116 cancer xenografts were imaged with (99m)Tc-TCP-1 or control peptide using a small-animal SPECT imager: Group I (n=5) received no blockade; Group II (n=5) received a blocking dose of non-radiolabeled TCP-1. Group III (n=5) were imaged with (99m)Tc-labeled control peptide (inactive peptide). SCID mice with human PC3 prostate cancer xenografts (Group IV, n=5) were also imaged with (99m)Tc-TCP-1. Eight additional SCID mice bearing HCT116 xenografts in dorsal skinfold window chambers (DSWC) were imaged by direct positron imaging of (18)F-fluorodeoxyglucose ((18)F-FDG) and fluorescence microscopy of Cy7-TCP-1. In vitro(99m)Tc-HYNIC-TCP-1 binding assays on HCT 116 cells indicated a mean Kd of 3.04±0.52nM. In cancer xenografts, (99m)Tc-TCP-1 radioactivity (%ID/g) was 1.01±0.15 in the absence of blockade and was reduced to 0.26±0.04 (P<0.01) with blockade. No radioactive uptake was observed in the PC3 tumors with (99m)Tc-TCP-1 or HCT116 tumors with inactive peptide. Cy7-TCP-1 activity localized not only in metabolically active tumors, as defined by (18)F-FDG imaging, but also in peritumoral microvasculature. In conclusion, TCP-1 probes may have a distinct targeting mechanism with high selectivity for CRC and tumor-associated vasculature. Molecular imaging with TCP-1 probes appears promising to detect malignant colorectal lesions.

Sustained release profile of quatro stimuli nanocontainers as a multi sensitive vehicle exploiting cancer characteristics

A versatile drug delivery carrier that responds to external stimuli was synthesized via the emulsion polymerization process. This simple two-step process was carried out by using Poly (Methyl Methacrylate) as a soft template and a series of monomers, with desired properties, as coating monomers. It is noteworthy that during shell fabrication (2nd step) an inner cavity is created inside the nanocontainers that can be used as a host for small drug molecules. The thermo-, pH- and redox sensitive monomers used in the coating procedure were Dimethyl Amino Ethyl Methacrylate (DMAEMA), Acrylic Acid (AA) and N,N'-(disulfanediylbis(ethane-2,1-diyl))bis(2-methylacrylamide) (Disulfide or DS), respectively. It has to be noted that DMAEMA is also pH- sensitive and acts synergistically with AA. The surface of the multi-stimuli nanocontainers was functionalized with magnetite nanoparticles in order to induce an alternating magnetic field (AMF) sensitivity. By using AMF in various strenghts and frequencies, the temperature of the final multi-stimuli nanocontainers (Q-NCs) can be increased in a controlled manner resulting in the Hyperthermia phenomenon. Loading and release studies were carried out using the anthracycline drug, Doxorubicin, aiming at the confirmation of the release mechanism.

Co-administration of succinylated gelatine with a (99m)Tc-bombesin analogue, effects on pharmacokinetics and tumor uptake

The bombesin analogue, [(99m)Tc-GGC]-(Ornithine)3-BN(2-14), (99m)Tc-BN-O, targeting gastrin releasing peptide receptors (GRPrs) on the surface of tumors, was pre-clinically investigated as potential imaging agent for single photon emission computed tomography (SPECT). In addition, the improvement of its pharmacokinetic profile (PK) was investigated through the co-administration of a succinylated gelatin plasma expander (Gelofusine), aiming to reduce its kidney accumulation and enhance its tumor-to-normal tissue contrast ratios. Biodistribution data were collected from normal mice and rats, and PC-3 tumor bearing mice, in reference to its PK, metabolism and tumor uptake. Imaging data were also collected from PC-3 tumor bearing mice. Biodistribution and imaging experiments showed that (99m)Tc-BN-O was able to efficiently localize the tumor (5.23 and 7.00% ID/g at 30 and 60min post injection, respectively), while at the same time it was rapidly cleared from the circulation through the kidneys. HPLC analysis of kidney samples, collected at 60min p.i. from normal mice and rats, showed that the majority of radioactivity detected was due to intact peptide i.e. 56% for mice and 73% for rats. Co-administration of (99m)Tc-BN-O with Gelo resulted in the reduction of kidney uptake in both animal models. The integrated area under the curve (AUC30-60 min) from the concentration-time plots of kidneys was decreased in both mice and rats by 25 and 50%, respectively. In PC-3 tumor bearing mice, an increase of tumor uptake (AUCtumor increased by 69%) was also observed with Gelo. An improvement in tumor-to-blood and tumor-to-normal tissue ratios was noted in all cases with the exception of the pancreas, which normally expresses GRPr. The results of this preclinical study may also be extended to other similar peptides, which are utilized in prostate cancer imaging and present similar PK profile.

Preparation and evaluation of the tumor-specific antigen-derived synthetic mucin 1 peptide: A potential candidate for the targeting of breast carcinoma

PURPOSE

The goal of this study was to prepare a synthetic peptide derived from breast tumor associated antigen and to evaluate its potential as a breast cancer imaging agent.

METHODS

A mucin 1 derived peptide was synthesized by solid-phase peptide synthesis and examined for its radiochemical and metabolic stability. The tumor cell binding affinity of (99m)Tc-MUC1 peptide was investigated on MUC1-positive T47D and MCF7 breast cancer cell lines. In vivo biodistribution was studied in normal Balb/c mice and in vivo tumor targeting and imaging in MCF7 and T47D tumor-bearing nude mice.

RESULTS

The synthesized MUC1-derived peptide displayed high radiochemical and metabolic stability. In vitro tumor cell-binding on T47D and MCF7 cell lines demonstrated high affinity of (99m)Tc-MUC1 peptide towards human breast cancer cells (binding affinities in nanomolar range). Pharmacokinetic studies performed on Balb/c mice are characterized by an efficient clearance from the blood and excretion predominantly through the urinary system. In vivo tumor uptake in nude mice with MCF7 tumor xenografts was 2.77±0.63% ID/g as early as 1h p.i. whereas in nude mice with T47D human ductal breast epithelial cancer cells, the accumulation in the tumor was found to be 2.65±0.54% ID/g at 1h p.i. Also tumor lesion was detectable in γ-camera imaging. The tumor uptake values were always higher than the blood and muscle uptake, with good tumor retention and good tumor-to-blood and tumor-to-muscle ratios. A low to moderate (<5% ID/g) accumulation and retention of (99m)Tc-MUC1 was found in the major organs (i.e., lungs, stomach, liver, intestines, kidneys, etc.) in both normal and tumor-bearing mice.

CONCLUSION

This study suggests that (99m)Tc-MUC1 tumor-antigen peptide may be a potential candidate for the targeted imaging of MUC1-positive human tumors and warrants further investigation.

Synthesis and biological assessment of folate-accepted developer (99m)Tc-DTPA-folate-polymer

A novel cancer-targetable folate-poly(2-hydroxyethyl methacrylate) (PFDH) copolymer containing DTPA segment was prepared by conventional chemical synthesis and labeled with (99m)Tc subsequently. The (99m)Tc-labled PFDH could be produced easily with high radiochemical yield of 91% and radiochemical purity of 95%. The LogP octanol-water value for the (99m)Tc-labled PFDH was -2.19 and the radiotracer was stable in phosphate-buffered saline and human serum for 2h (>95% in PBS or ∼90% in human serum). To investigate (99m)Tc-labled PFDH tumor targeting, the in vitro and in vivo stability, cell uptake, in vivo biodistribution, and SPECT imaging were evaluated, respectively. These preliminary results strongly suggest that the novel folate conjugated dendrimer maybe developed to be potential for delivery of therapeutic radionuclides.

Noninvasive visualization of microRNA-155 in multiple kinds of tumors using a radiolabeled anti-miRNA oligonucleotide

PURPOSE

We investigated whether a (99m)Tc radiolabeled anti-miRNA-155 oligonucleotide (AMO-155) could visualize the expression of miR-155 in multiple kinds of tumors in vivo.

METHODS

AMO-155 was chemically synthesized and modified with 2'-O-methyl (2'-OMe) and phosphorothioate (PS). It was radiolabeled with (99m)Tc via the conjugation with NHS-MAG3 at 5' end. The characterization of radiolabeling and serum stability was evaluated using high performance liquid chromatography (HPLC) and agarose gel electrophoresis. The expression of C/EBPβ, one of the miR-155 target proteins, was assessed using Western blot. The cellular uptake and delivery of AMO-155 was further evaluated in tumor cells. (99m)Tc-AMO-155 was tested in vivo in multiple tumor models, including miR-155 over-expressed and low-expressed tumor models. Finally, biodistribution of (99m)Tc-AMO-155 was evaluated.

RESULTS

(99m)Tc-AMO-155 was prepared with high yield and radiochemical purity. It showed high stability in fresh human serum for 10h. (99m)Tc-AMO-155 displayed comparable capacity as unlabeled AMO-155 to increase the expression of C/EBPβ protein in MCF-7 cells. (99m)Tc-AMO-155 showed an increased radioactive uptake in MCF-7 cells after 8h of incubation, whereas no change of (99m)Tc-pertechnetate uptake was observed. Carboxyfluorescein (FAM) labeled AMO-155 had higher fluorescent delivery than Control in HeLa and HepG2 cells by confocal microscopy. In miR-155 over-expressed tumor models, (99m)Tc-AMO-155 showed significantly higher tumor accumulation than (99m)Tc-Control. Furthermore, (99m)Tc-AMO-155 was capable of discriminating between MCF-7 and MDA-MB-231 tumors based on their expression of miR-155.

CONCLUSIONS

Our study successfully prepared and proved (99m)Tc-AMO-155 as a prospective imaging agent for the noninvasive visualization of miR-155 expression in vivo.

⁹⁹mTc-HYNIC-MPG: a novel SPECT probe for targeting mutated EGFR

Mutated epidermal growth factor receptor (EGFR) is an important biomarker for cancer diagnosis and molecular target for many anticancer drugs. Localizing EGFR and evaluating EGFR mutational status can help to identify patients who are potentially the most suitable ones for targeted treatments. Hence, we developed a novel EGFR tyrosine kinase inhibitor labeled with (99m)Tc ((99m)Tc-HYNIC-MPG) and evaluated its EGFR binding capacity in vitro and in vivo. This molecular probe was synthesized by one-step method that is simple and highly efficient. Importantly, the uptake rate for (99m)Tc-HYNIC-MPG in the liver was as low as 28.44 ± 0.15% (mean ± SD, n=3). This finding presents for the first time that (99m)Tc-HYNIC-MPG can bind to mutated EGFR efficiently and thus provides a novel molecular tool to detect mutated EGFR and suppress tumorigenesis.

Identification of Staphylococcus aureus infection by aptamers directly radiolabeled with technetium-99m

INTRODUCTION

Aptamers are oligonucleotides that have high affinity and specificity for their molecular targets which are emerging as a new class of molecules for radiopharmaceuticals development. In this study, aptamers selected to Staphylococcus aureus were evaluated for bacterial infection identification.

METHODS

Anti S. aureus aptamers were labeled with (99m)Tc by the direct method. The radiolabel yield and complex stability were assessed by thin-layer chromatography (TLC). Three groups of Swiss mice containing 6 animals each were used. The first group was infected intramuscularly in the right thigh with S. aureus. The second group was infected in the same way with C. albicans and the third group was injected with zymosan to induce aseptic inflammation. After 24 h, radiolabeled aptamers (22.2 MBq) were injected by the tail vein. The mice were euthanized 4 h post injection and tissue sample activities measured in a gamma counter.

RESULTS

The (99m)Tc labeled aptamers were stable in saline, plasma and cystein excess. Radiolabeled aptamers showed increased uptake in the kidneys for all groups indicating a main renal excretion, which is consistent with the hydrophilic nature and small size of aptamers. The radiopharmaceutical showed rapid blood clearance indicated by a reduced dose (% ID/g) in the blood. The biodistribution showed that aptamers were able to identify the infection foci caused by S. aureus displaying a target/non-target ratio of 4.0±0.5. This ratio for mice infected with C. albicans was 2.0±0.4 while for mice with aseptic inflammation was 1.2±0.2. Histology confirmed the presence of infection in groups 1 and 2, and inflammation in group 3.

CONCLUSIONS

The biodistibution study demonstrated a statistically higher uptake in the S. aureus foci relative to inflammation and C. albicans infected areas. These results highlight the potential of aptamers labeled directly with (99m)Tc for bacterial infection diagnosis by scintigraphy.

Physicochemical studies of the reaction of (99m)Tc with 5,5'-diethyl barbituric acid, adenine, d-glucose and thiobarbituric acid at different temperatures

The reaction of (99m)Tc pertechnetate with 5,5'-diethyl barbituric acid, adenine, d-glucose and thiobarbituric acid at different temperatures was studied. The solvent effect on the electronic absorption spectra of the reactions was recorded. The reaction mixtures have been analyzed at different times using TLC and a radiodetctor to show the peaks at the plates. (99m)Tc pertechnetate is obtained from the Mo generators. It is difficult to separate the complexes in the solid state. The percentage of (99m)Tc involved in the complexes can be determined. Characterization of the (99m)Tc complexes as well as the determination of the extent of radiolabeling was done by thin layer chromatography using 0.9% NaCl solution as a solvent. The Rf value of (99m)TcO4(-) is (≈1). The solvatochromism for the reaction of (99m)Tc with d-glucose was mainly affected by solute permanent dipole-solvent permanent dipole interaction, the dipolar interaction for the reaction of (99m)Tc with of 5,5'-diethyl barbituric acid and for the reaction of (99m)Tc with adenine and thiobarbituric was solute-solvent hydrogen bonding.

Kit formulated asialoglycoprotein receptor targeting tracer based on copolymer for liver SPECT imaging

INTRODUCTION

Specific targeting of galactose-carrying molecule to ASGP-R in normal hepatocytes has been demonstrated before. In this study, galactosyl polystyrene was synthesized from controllable ratio of functional monomers and radio-labelled with (99m)Tc by formulated kit for SPECT imaging of hepatic function.

METHODS

p(VLA-co-VNI)(46:54) was synthesized by free-radical copolymerization initiated by AIBN, purified by dialysis, lyophilized to kit with Tricine and TPPTS as co-ligands for (99m)Tc labeling. Radiotracer (99m)Tc-p(VLA-co-VNI)(46:54)(Tricine)(TPPTS) was prepared and evaluated by in vitro stability, in vivo metabolism, ex vivo biodistribution and microSPECT/CT imaging in normal KM mice. MicroSPECT/CT and microMRI imaging were also performed in C57BL/b6 mice with xenograft hepatic carcinoma for hepatic function evaluation.

RESULTS

(99m)Tc-p(VLA-co-VNI)(46:54)(Tricine)(TPPTS) was obtained in high radio chemical purity (RCP) (>99%) by using instant kit without further purification and excellent in vitro and in vivo stability. The result of biodistribution showed that liver had high uptake (90.49±10.68 ID%/g) at 30 min after injection and was blocked significantly by cold copolymer. MicroSPECT imaging in normal KM mice at 1h and 4h after injection showed good liver retention and targeting properties. Significant defect of activity was observed in the tumor site which was confirmed by MRI imaging.

CONCLUSION

(99m)Tc-p(VLA-co-VNI)(46:54)(Tricine)(TPPTS) with lower ratio of targeting moiety has no observable effect on the specific binding affinity and liver uptake. This makes it possible to introduce more imaging units for multi-modality imaging. Furthermore, the instant kit preparation of (99m)Tc-labeling provides great potential for the evaluation of hepatocyte function in clinical application.

Preparation of 99mTc-TRODAT-1 with high labeling yield in boiling water bath: a new formulation

A new formulation for preparation of (99m)Tc-labeled tropane derivative, (99m)Tc-TRODAT-1, which is useful as a potential CNS dopamine transporter imaging agent, was evaluated and characterized. Preparation of (99m)Tc-TRODAT-1 was attained previously by a formulation in which vial has to be autoclaved at 121 °C for 30 min. It is highly desirable to further improve the preparation method by developing a simplified one vial formulation which will be labeled in boiling water bath (95 °C) for 15 min and a high labeling yield will be achieved. A formulation contained 10 μg of TRODAT-1, 20 μg tricine, 40 μg SnCl2 and 20mg manitol was prepared. Labeling was performed at 95 °C for 15 min and radiochemical analysis involved ITLC and HPLC methods. The stability of radioconjugate was checked in the presence of human serum at 37 °C up to 24h. (99m)Tc-TRODAT-1 was prepared with a radiochemical purity of more than 95% and specific activity of 64.3 MBq/nmol. Biodistribution studies of this new formulation in rats revealed similar regional brain distribution as compared with those obtained with the previous preparation in which brain uptake was high in striatum and striatum to cerebellum ratio was high. Requiring no autoclave facility for labeling, this new formulation will significantly improve the using feasibility of this radiopharmaceutical in clinic.

Validation of an alternative radiochemical purity method for [99mTc]pentetate ([99mTc]DTPA)

[(99m)Tc]pentetate ([(99m)Tc]DTPA) is the most commonly used radiopharmaceutical renography agent. The aim of this work was to validate an alternative method for assessing [(99m)Tc]DTPA radiochemical purity (RCP), according to the ICH Q2(R1) guidance: "Validation of Analytical Procedures". The proposed method is composed of two chromatographic systems. System A is a miniaturized system of thin layer chromatography (TLC) silica gel impregnated aluminum strips as stationary phase (SP) and distilled water as mobile phase (MP). System B consists of Whatman 1 paper strips as SP and methyl ethyl ketone as MP. Results indicate that the proposed RCP method has been validated, as it is specific, precise, accurate, linear and robust. Therefore, it can be used as an alternative method for RCP quality control purposes and as stability indicator as well.

A novel ingestible electronic drug delivery and monitoring device

BACKGROUND

We developed an ingestible electronic drug delivery and monitoring system. This system includes an electronic capsule comprising a drug reservoir, a pH and temperature sensor, a microprocessor and wireless transceiver, a stepper motor, and batteries. The location of the capsule in the gut derived from pH data can be monitored in real time. The stepper motor can be remotely actuated to expel the contents of the drug reservoir.

OBJECTIVES

First human study.

DESIGN

Two consecutive observational studies.

SETTING

University medical center.

SUBJECTS

Twenty healthy volunteers.

INTERVENTIONS

Study I: Ingestion and passage of the capsule. Study II: Ingestion and passage of the capsule, loaded with (99m)technetium-pertechnetate ((99m)Tc); remotely actuated expulsion of (99m)Tc in the gut.

MAIN OUTCOME MEASUREMENTS

Study I: Safety, tolerability, and functionality (wireless pH and temperature recording). Study II: Tracing of the capsule and expulsion and distribution of (99m)Tc from the drug reservoir by scintigraphy. Correlating location pH with scintigraphy.

RESULTS

Study I: Ingestion and passage of the capsule was safe and well tolerated. Transmitted pH and temperature data were received by the recorder in 96.5% ± 3%. Study II: pH-determined passage of the esophagogastric, gastroduodenal, and ileocolonic junction correlated well with scintigraphy. Expulsion of (99m)Tc from the capsule was successful in 9 of 10 subjects.

LIMITATIONS

Subjects with relatively low body mass index.

CONCLUSIONS

This electronic drug delivery and monitoring system may be a promising tool for targeted delivery of substances to well-defined areas of the GI tract.

(99m)Tc-MORF oligomers specific for bacterial ribosomal RNA as potential specific infection imaging agents

PURPOSE

Radiolabeled oligomers complementary to the 16S rRNA in bacteria were investigated as bacterial infection imaging agents.

METHODS AND RESULTS

Identical sequences with backbones phosphorodiamidate morpholino (MORF), peptide nucleic acid (PNA), and phosphorothioate DNA (PS-DNA) were (99m)Tc-labeled and evaluated for binding to bacterial RNA. MORF binding to RNA from Escherichia coli strains SM101 and K12 was 4- and 150-fold higher compared to PNA and PS-DNA, respectively. Subsequently MORF oligomer in fluorescence in situ hybridization showed a stronger signal with study MORF compared to control in fixed preparations of two E. coli strains and Klebsiella pneumoniae. Flow cytometry analysis showed study MORF accumulation to be 8- and 80-fold higher compared to the control in live K. pneumoniae and Staphylococcus aureus, respectively. Further, fluorescence microscopy showed increased accumulation of study MORF over control in live E. coli and K. pneumonia. Binding of (99m)Tc-study MORF to RNA from E. coli SM101 and K12 was 30.4 and 117.8pmol, respectively, per 10(10) cells. Mice with K. pneumoniae live or heat-killed (sterile inflammation) in one thigh at 90min for both (99m)Tc-study MORF and control showed higher accumulation in target thighs than in blood and all other organs expect for kidneys and small intestine. Accumulation of (99m)Tc-study MORF was significantly higher (p=0.009) than that of the control in the thigh with sterile inflammation.

CONCLUSION

A (99m)Tc-MORF oligomer complimentary to the bacterial 16S rRNA demonstrated binding to bacterial RNA in vitro with specific accumulation into live bacteria. Radiolabeled MORF oligomers antisense to the bacterial rRNA may be useful to image bacterial infection.

A HER2-targeted RNA aptamer molecule labeled with 99mTc for single-photon imaging in malignant tumors

A modified RNA aptamer with HER2-specific binding was conjugated to hynic and labeled with (99m)Tc, for potential use as a radiopharmaceutical for diagnostic imaging of ovarian cancer cells (SKOV-3) with high HER2 expression. The aptamer was radiolabeled with (99m)Tc by using hynic as the chelator and tricine as the co-ligand. Stability testing of the radioconjugated aptamer was performed via ITLC and SDS-PAGE in normal saline and serum. The aptamer-radionuclide conjugate was evaluated for cellular HER2-specific binding, saturation affinity, and cellular internalization in SKOV-3 and MCF-7 cells, and its biodistribution properties were assessed in normal and SKOV-3 tumor-bearing mice. Radiolabeling of the aptamer was achieved with high yield and radiochemical purity, and the (99m)Tc-hynic-RNA aptamer was highly stable in normal saline and serum. Cellular experiments showed specific binding of the aptamer to the HER2 receptor with a dissociation constant of 27 nM. Rapid blood clearance was observed after injection of the (99m)Tc-hynic-RNA aptamer, and the main excretion route was via the hepatobilary system. While the radioconjugated aptamer bound specifically to the HER2 receptor on cells in vitro, it did not show any significant tumor-to-blood or tumor-to-muscle ratios in mice. Modifications to radiolabeled aptamer will require improving its pharmacokinetic properties and tumor uptake in vivo.

Diagnostic accuracy of renal pelvic dilatation for detecting surgically managed ureteropelvic junction obstruction

PURPOSE

In this study we evaluate the diagnostic accuracy of renal pelvic dilatation for detecting infants with prenatal hydronephrosis who will need surgical intervention for ureteropelvic junction obstruction during followup.

MATERIALS AND METHODS

Between 1999 and 2010, 371 newborns diagnosed with isolated prenatal hydronephrosis were prospectively followed. The main event of interest was the need for pyeloplasty. Diagnostic odds ratio, sensitivity, specificity and diagnostic accuracy (assessed by AUC) of fetal renal pelvic dilatation and postnatal renal pelvic dilatation were evaluated.

RESULTS

A total of 312 patients were included in the analysis and 25 (7.5%) infants underwent pyeloplasty. The diagnostic performance for detecting the need for pyeloplasty was excellent for all ultrasonography measurements. The AUC was 0.96 (95% CI 0.92-0.98) for fetal renal pelvic dilatation, 0.97 (95% CI 0.95-0.98) for postnatal renal pelvic dilatation and 0.95 (95% CI 0.92-0.97) for the Society for Fetal Urology grading system. A cutoff of 18 mm for fetal renal pelvic dilatation and a cutoff of 16 mm for postnatal renal pelvic dilatation had the best diagnostic odds ratio to identify infants who needed pyeloplasty. Considering a diagnosis to be positive only if fetal renal pelvic dilatation was greater than 18 mm and postnatal dilatation was greater than 16 mm, sensitivity was 100% and specificity was 86% (95% CI 80.7-89.9).

CONCLUSIONS

Our findings suggest that the combination of fetal and postnatal renal pelvic dilatation is able to increase the diagnostic accuracy for detecting infants who need a more comprehensive postnatal investigation for upper urinary tract obstruction.