Design and preliminary assessment of 99mTc-labeled ultrasmall superparamagnetic iron oxide-conjugated bevacizumab for single photon emission computed tomography/magnetic resonance imaging of hepatocellular carcinoma

Hepatocellular carcinoma (HCC) has a very high incidence and mortality. Early diagnosis and timely treatments are therefore required to improve the quality of life and survival rate of HCC patients. Here, we developed a vascular endothelial growth factor (VEGF)-based multimodality imaging agent for single photon emission computed tomography (SPECT), computed tomography (CT) and magnetic resonance imaging (MRI) and used it to assess HCC mice and explore the combinative value of CT/MRI-based morphological imaging and SPECT functional imaging. HCC targeting with ¹²⁵I-labeled bevacizumab monoclonal antibody (mAb) was examined using SPECT/CT in HepG2 tumor-bearing mice after intravenous mAb injection. Based on this, an integrated, bimodal, VEGF-targeted, ultrasmall superparamagnetic iron oxide (USPIO)-conjugated ^99mTc-labeled bevacizumab mAb was synthesized to increase tumor penetration and accumulations. The in vivo pharmacokinetics and HepG2 tumor targeting were explored through in vivo planar imaging and SPECT/CT using a mouse model of HepG2 liver cancer. The specificity of the radiolabeled nanoparticles for HepG2 HCC was verified using in vitro immunohistochemistry and Prussian blue staining. With diethylenetriamine pentaacetic acid as a bifunctional chelating agent, USPIO-bevacizumab achieved a ^99mTc labeling efficiency of >90 %. The in vivo imaging results also exhibited the targeting of USPIO on HepG2 HCC. The specificity of these results was confirmed using in vitro immunohistochemistry and Prussian blue staining. Our preliminary findings showed the potential of USPIO as an imaging agent for the SPECT/MRI of HepG2 HCC.     

Preparation and evaluation of <Superscript>131</Superscript>I-quercetin as a novel radiotherapy agent against dedifferentiated thyroid cancer

Here we reported the radiolabeling and evaluation of a novel ¹³¹I-radiolabeled quercetin for the treatment of dedifferentiated thyroid cancers. The human thyroid cancer cell lines (FTC-133, TT and DRO) experienced much higher uptake of ¹³¹I-quercetin as compared to the free ¹³¹I. And the proliferation inhibition rate of ¹³¹I-quercetin on in vitro DRO cell line was 86.87 ± 7.15%. Biodistribution and SPECT analysis demonstrated that the injected radioactivity mainly accumulated in tumors. The tumor volume in the treatment group was dramatically inhibited in comparison with the control group.     

A novel peptide-based probe 99mTc-PEG6-RD-PDP2 for the molecular imaging of tumor PD-L2 expression

Tumor-related PD-L2 expression is associated with the clinical efficacy of PD-1/PD-L1 blockade therapy. PD-L2-specific imaging can help selecting patients for appropriate immunotherapy. In this study, a PD-L2-targeting peptide (PDP2) was screened by the one-bead one-compound combinatorial library approach. Using the retro-inverso d-peptide of PDP2 (RD-PDP2) and PEGylation strategies, we developed a novel Tc-99m-labeled PD-L2-targeting peptide as a SPECT tracer (^99mTc-PEG₆-RD-PDP2) for imaging of tumor PD-L2 expression. The radiolabeling yield of ^99mTc-PEG₆-RD-PDP2 was greater than 95% by the standard HYNIC/tricine/TPPTS labeling procedure. ^99mTc-PEG₆-RD-PDP2 displayed high PD-L2-binding specificity both in vitro and in vivo. SPECT/CT imaging with ^99mTc-PEG₆-RD-PDP2 showed that the A549-PD-L2 tumors were clearly visualized, whereas the signals in PD-L2-negative A549 tumors were much lower. In vivo blocking study suggested that the tumor uptake of ^99mTc-PEG₆-RD-PDP2 was PD-L2 specifically mediated. ^99mTc-PEG₆-RD-PDP2 is a promising SPECT probe for the non-invasive imaging of tumor PD-L2 expression and has a great potential in guiding the anti-PD-1 or anti-PD-L1 immunotherapy of cancer.     

Preparation of <Superscript>131</Superscript>I–betulinic acid and its biodistribution in murine model of hepatocellular tumor

The aim of this study was to examine the radioiodinating condition of betulinic acid and understand the possibility of ¹³¹I–betulinic acid (¹³¹I–BA) as a potential tumor radiotherapy agent through in vitro uptake and in vivo biodistribution studies ¹³¹I–BA was prepared by the reaction of betulinic acid with Na¹³¹I in the presence of hydrogen peroxide, and then purified by HPLC. The labeling yield was about 80%, and the radiochemical purity was greater than 95%. ¹³¹I–BA was found to be stable at 4 °C in saline containing 1% ethanol. In vitro studies showed that ¹³¹I–betulinic acid accumulated in the cancer cell lines (BEL-7402 and NCI-H446) in comparison with free ¹³¹I⁻. In vivo biodistribution study in KM mice bearing HepA tumor showed that ¹³¹I–BA stayed longer time in tumors than free ¹³¹I⁻. A significant differences were seen in tumor/muscle ratio at 4 h postinjection between ¹³¹I–BA and free ¹³¹I⁻. In vivo and in vitro studies showed the higher fraction of ¹³¹I–BA can be utilized for therapy and a higher dose will be delivered per targeting event. ¹³¹I–BA is a promising radiopharmaceutical in nuclear medicine, especially for hepatocellular tumor targeted radionuclide brachytherapy.     

Evaluation of a novel EphA2 targeting peptide for triple negative breast cancer based on radionuclide molecular imaging

A new strategy for the early diagnosis of triple-negative breast cancer (TNBC) is urgently needed however specific targets are lacking. EphA2 has been reported to be over-expressed in a variety of tumors, including TNBC, and is closely related to tumor progression. In this study, we designed a novel peptide, SD01, and tested its potential in the diagnosis of TNBC. FITC-SD01 and FITC-YSA were prepared and found to bind to the 4T1 TNBC cell line, the former showing greater affinity. ¹²⁵I-SD01 and ¹²⁵I-YSA were obtained with high radiochemical yield and radiochemical purity, and both showed a high binding affinity to 4T1 cells, with a higher B_max in ¹²⁵I-SD01. Whole-body phosphoautoradiography showed clearer imaging of tumors in the group of ¹²⁵I-SD01 than in ¹²⁵I-YSA. Biodistribution demonstrated higher tumor accumulation in the ¹²⁵I-SD01 group. In group of ¹²⁵I-SD01, the tumor to the opposite muscle tissue (T/NT) ratio was 5.998 ± 0.37, in contrast to 4.69 ± 0.18 in ¹²⁵I-YSA group. Our results indicated that ¹²⁵I-SD01 could selectively and specifically target 4T1 cells in vitro and in vivo, and showed higher binding affinity and better imaging compared to ¹²⁵I-YSA. Therefore, SD01 was deemed to be a novel peptide with more favorable properties in terms of targeting EphA2.     

Sulfamide-substituted-BODIPY based fluorescence drugs: Synthesis,spectral characteristics,molecular docking,and bioactivity

BODIPY derivatives have attracted much attention in the field of biological probes, but probes with a single imaging function are no longer innovative. In this paper, two multifunctional sulfonamide-BODIPY derivatives were designed and synthesized. Photophysical properties, cytotoxicity, in vitro and in vivo imaging, apoptosis, cell cycle, and molecular docking simulation were studied. The results showed that the compound had low cytotoxicity to normal cells, but had strong inhibitory effect on tumor cells. The IC₅₀ value of compound 3 on HCT-116 cells was 58.61 ± 4.91 μmol/L, and 4 on HeLa cells was 52.29 ± 10.93 μmol/L. Cell imaging and mice experiments demonstrated that the probe had excellent biocompatibility and potential tumor targeting; and in vivo imaging of mice at different time periods showed that the fluorescence intensity of probes in subcutaneous lung tumor gradually increased with the extension of time. In addition, the flow cytometry analysis of 3 showed that the G1 phase of HCT-116 cells was inhibited and apoptosis of tumor cells was promoted. In molecular docking simulation, sulfonamide-BODIPY derivatives had high affinity scores with CDK2: −8.0 and −8.4 kcal·mol⁻¹, and the multiple interactions with receptors provided conditions for the probes to recognize tumor cells.     

Preparation and SPECT imaging of the novel Anxa 1-targeted probe 99mTc-p-SCN-Bn-DTPA-GGGRDN-IF7

Annexin 1 (Anxa1) is a highly specific surface marker of tumor vasculature in several solid tumors. The IF7 peptide was modified with a hydrophic linkers,GGGRDN, and introduced into a new bifunctional chelating agent p-SCN-Bn-DTPA. The resulting peptides (p-SCN-Bn-DTPA-GGGRDN-IF7) was successfuly labeled with ^99mTc. The targeting characteristics to Anxa1 of the radiolabeled peptide were evaluated by in vitro and in vivo study is on U87 tumor models. SPECT imaging revealed that the U87 tumors were clearly visualized (3.64 ± 0.44%ID/g at 2 h p.i.). ^99mTc-p-SCN-Bn-DTPA-GGGRDN-IF7 (Tc-RIF7) might be a potential target probe for detecting Anxa1 levels in cancers due to the favorable characterizations such as convenient synthesis, specific Anxa1 targeting and moderate tumor uptakes.

     

Multifunctional nanoprobe for cancer cell targeting and simultaneous fluorescence/magnetic resonance imaging

Multifunctional nanoprobes with distinctive magnetic and fluorescent properties are highly useful in accurate and early cancer diagnosis. In this study, nanoparticles of Fe₃O₄ core with fluorescent SiO₂ shell (MFS) are synthesized by a facile improved Stöber method. These nanoparticles owning a significant core-shell structure exhibit good dispersion, stable fluorescence, low cytotoxicity and excellent biocompatibility. TLS11a aptamer (Apt1), a specific membrane protein for human liver cancer cells which could be internalized into cells, is conjugated to the MFS nanoparticles through the formation of amide bond working as a target-specific moiety. The attached TLS11a aptamers on nanoparticles are very stable and can't be hydrolyzed by DNA hydrolytic enzyme in vivo. Both fluorescence and magnetic resonance imaging show significant uptake of aptamer conjugated nanoprobe by HepG2 cells compared to 4T1, SGC-7901 and MCF-7 cells. In addition, with the increasing concentration of the nanoprobe, T₂-weighted MRI images of the as-treated HepG2 cells are significantly negatively enhanced, indicating that a high magnetic field gradient is generated by MFS-Apt1 which has been specifically captured by HepG2 cells. The relaxivity of nanoprobe is calculated to be 11.5 mg⁻¹s⁻¹. The MR imaging of tumor-bearing nude mouse is also confirmed. The proposed multifunctional nanoprobe with the size of sub-100 nm has the potential to provide real-time imaging in early liver cancer cell diagnosis.     

Indium-111 labeled bleomycin for targeting diagnosis and therapy of liver tumor: optimized preparation,biodistribution and SPECT imaging with xenograft models

In this work, the preparation of ¹¹¹In radiolabeled bleomycin (¹¹¹In-BLM) was optimized systematically and used for SPECT imaging of liver cancer xenograft models. ¹¹¹In-BLM with a high radiochemical yield (>?99%) could be obtained at pH 0.5–1 at a mixture ratio of 9:1 (¹¹¹In/BLM, mCi/mg). The radiochemical purity of ¹¹¹In-BLM retained?>?99% in either buffers or serum for 3 days. Biodistribution of ¹¹¹In-BLM revealed its excellent stability in vivo. The SPECT imaging studies showed ¹¹¹In-BLM has great specificity to liver tumor xenograft. All the results implied ¹¹¹In-BLM is a potential radiopharmaceutical for targeting diagnosis and therapy of liver tumor.

     

Evaluation and comparison of 99mTc-labeled d-glucosamine derivatives with different 99mTc cores as potential tumor imaging agents

Isocyanide is a strong coordination ligand that can coordinate with [^99mTc(I)(CO)₃]⁺ core and [^99mTc(I)]⁺ core to produce stable ^99mTc complexes, therefore developing a ^99mTc-labeled isocyanide complex for single-photon emission computed tomography (SPECT) imaging is considered to be of great interest. In order to develop potential tumor imaging agents with satisfied tumor uptake and suitable pharmacokinetic properties in vivo, a novel d -glucosamine isocyanide derivative, 4-isocyano-N-(2,4,5-trihydroxy-6-(hydroxymethyl)tetrahydro-2H-pyran-3-yl)butanamide (CN3DG), was synthesized and radiolabeled with [^99mTc(I)]⁺ and [^99mTc(CO)₃]⁺ cores to obtain [^99mTc(CN3DG)₆]⁺ and [^99mTc(CO)₃(CN3DG)₃]⁺ in high radiolabeling yields (>95%). Both of the complexes showed good hydrophilicity and great stability in vitro. Cell uptake studies performed in S180 cells demonstrated they were transported into cells by glucose transporters. Biodistribution studies of the two complexes in mice bearing S180 tumor showed they had high tumor uptakes and rapid clearance from muscle and blood so that the tumor/blood and tumor/muscle ratios were high. By comparison, [^99mTc(CN3DG)₆]⁺ was superior to [^99mTc(CO)₃(CN3DG)₃]⁺ in regard to tumor uptake, tumor/blood and tumor/liver ratios. S180 tumors could be seen clearly from the SPECT/CT images with [^99mTc(CN3DG)₆]⁺. Considering its favorable properties, [^99mTc(CN3DG)₆]⁺ would be a promising tumor imaging agent and needs to be further studied.     

Preparation of <Superscript>99m</Superscript>Tc-metronidazole as a model for tumor imaging

Metronidazole (MTNZ) is an antiprotozoa drug, could be labeled with the ^99mTc. MTZL could be used as an ideal vehicle to deliver radioactive decay energy of ^99mTc to the sites of tumor, thus facilitate tumor imaging. The process of labeling was done using tin chloride as reducing agent. The optimum conditions required to label 25 μg MTZL were 100 μg stannous chloride, 30 min reaction time, room temperature at pH 7–9 using 0.5 M phosphate buffer. The radiochemical purity of the labeled compound, at the above conditions, was determined using paper chromatography. The yield was about 93%. About 2.5 × l0⁶ of Ehrlich Ascites Carcinoma (EAC) was injected intrapritoneally (i.p) to produce ascites and intramuscularly (i.m) in the right thigh to produce solid tumor in female mice. Biodistribution studies were carried out by injecting solution of ^99mTc-MTZL in normal and tumor bearing mice. The uptake in ascites was over 5% of the injected dose per gram tissue body weight, at 4 h post injection and above 4% in solid tumor. These data revealed localization of the tracer in the tumor tissues with high percentage sufficient to use ^99 mTc MTZL as promising tool for diagnosis of tumor.     

Streamlined in vivo selection and screening of human prostate carcinoma avid phage particles for development of peptide based in vivo tumor imaging agents

Bacteriophage (phage) display has been exploited for the purpose of discovering new cancer specific targeting peptides. However, this approach has resulted in only a small number of tumor targeting peptides useful as in vivo imaging agents. We hypothesize that in vivo screening for tumor uptake of fluorescently tagged phage particles displaying multiple copies of an in vivo selected tumor targeting peptide will expedite the development of peptide based imaging agents. In this study, both in vivo selection and in vivo screening of phage displaying foreign peptides were utilized to best predict peptides with the pharmacokinetic properties necessary for translation into efficacious in vivo imaging agents. An in vivo selection of phage display libraries was performed in SCID mice bearing human PC-3 prostate carcinoma tumors. Eight randomly selected phage clones and four control phage clones were fluorescently labeled with AlexaFluor 680 for subsequent in vivo screening and analyses. The corresponding peptides of six of these phage clones were tested as 111In-labeled peptide conjugates for single photon emission computed tomography (SPECT) imaging of PC-3 prostate carcinomas. Two peptide sequences, G1 and H5, were successful as in vivo imaging agents. The affinities of G1 and H5 peptides for cultured PC-3 cells were then analyzed via cell flow cytometry resulting in Kd values of 1.8 μM and 2.2 μM, respectively. The peptides bound preferentially to prostate tumor cell lines compared to that of other carcinoma and normal cell lines, and H5 appeared to possess cytotoxic properties. This study demonstrates the value of in vivo screening of fluorescently labeled phage for the prediction of the efficacy of the corresponding 111In-labeled synthetic peptide as an in vivo SPECT tumor imaging agent.     

Preparation and Evaluation of Novel Folate Isonitrile 99mTc Complexes as Potential Tumor Imaging Agents to Target Folate Receptors

In order to seek novel technetium-99m folate receptor-targeting agents, two folate derivatives (CN5FA and CNPFA) were synthesized and radiolabeled to obtain [^99mTc]Tc-CN5FA and [^99mTc]Tc-CNPFA complexes, which exhibited high radiochemical purity (>95%) without purification, hydrophilicity, and good stability in vitro. The KB cell competitive binding experiments indicated that [^99mTc]Tc-CN5FA and [^99mTc]Tc-CNPFA had specificity to folate receptor. Biodistribution studies in KB tumor-bearing mice illustrated that [^99mTc]Tc-CN5FA and [^99mTc]Tc-CNPFA had specific tumor uptake. Compared with [^99mTc]Tc-CN5FA, the tumor/muscle ratios of [^99mTc]Tc-CNPFA were higher, resulting in a better SPECT/CT imaging background. According to the results, the two ^99mTc complexes have potential as tumor imaging agents to target folate receptors.     

Synthesis and evaluation of 111In-labeled d-glucose as a potential SPECT imaging agent

The purpose of this study was to develop an efficient synthetic method for labeling d-Glucosamine with indium-111 (¹¹¹In), and to investigate the imaging properties of the resulting radiotracer in MDA-MB-468 xenograft models using single-photon emission computed tomography (SPECT). The precursor compound, 2-(4-Isothiocyanato benzyl)-1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid-deoxyglucosone (DOTA-DG), was synthesized from 2-d-Glucosamine. DOTA-DG was labeled with ¹¹¹In within 20 min. The labeling efficiency and radiochemical purity of ¹¹¹In-DOTA-DG were >95 and >96 % as determined by radio-HPLC. SPECT imaging studies were performed using nude mice bearing MDA-MB-468 mammary tumors after intravenous injection of at a dose of 1.11 MBq (0.1 mL) ¹¹¹In-DOTA-DG. Tumors were clearly delineated by SPECT imaging at 120 min after injection.     

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.     

Radiolabeled GX1 Peptide for Tumor Angiogenesis Imaging

Early and accurate detection of primary or metastatic tumors is of great value in staging, treatment management, and prognosis. Tumor angiogenesis plays an essential role in the growth, invasion, and metastatic spread of solid cancers, and so, is a promising approach for tumor imaging. The GX1 (CGNSNPKSC) peptide was identified by phage display library and has been investigated as a marker for human cancers. This study aims to evaluate the ^99mTc-HYNIC-PEG₄-c (GX1) as a biomarker for tumor imaging. Our results showed that GX1 specifically binds to tumor cells in vitro. SKMEL28 and MDA-MB231 cells achieved total binding peak at 60 min of incubation. For B16F10 and MKN45 cells, the total and specific binding were similar during all time points, while A549 cell line showed rapid cellular total uptake of the tracer at 30 min of incubation. Biodistribution showed low non-specific uptakes and rapid renal excretion. Melanoma tumors showed enhanced GX1 uptake in animal model at 60 min, and it was significantly blocked by cold peptide. The radiotracer showed tumor specificity, especially in melanomas that are highly vascularized tumors. In this sense, it should be considered in future studies, aiming to evaluate degree of angiogenesis, progression, and invasion of tumors.     

Biodistribution and imaging of <Superscript>99m</Superscript>Tc-MAVGG-adenine in tumor bearing mice

To increase the tumor uptake of Val-Gly-Gly (VGG), adenine was introduced into the peptide. N-mercaptoacetyl-VGG-adenine (MAVGG-adenine) and MAVGG were labeled with ^99mTc using a solution of SnCl₂ and tartaric acid as reducing agent. Biodistribution in mice bearing the S180 tumor was measured and γ imaging was performed. Compared with MAVGG, adenine conjugated MAVGG had higher tumor uptake and tumor to normal tissue ratios, which suggested that the tumor uptake property of a peptide may be improved by introducing a nucleotide base. The high contrasted tumor images of ^99mTc-MAVGG-adenine also suggested its potential utility as tumor imaging agent.     

Could be radiolabeled flavonoid used to evaluate infection?

The aim of this study was to determine whether [¹³¹I]apigenin is a powerful and discrimination infection from inflammation for scintigraphic imaging. The study was carried out in inflamed rats with Staphylococcus aureus (S. aureus) and sterile inflamed rats with turpentine oil. Biodistribution study of [¹³¹I]apigenin was performed in the rats. Apigenin was labeled with ¹³¹I by iodogen method. Obtained [¹³¹I]apigenin with high yield (98%) was injected i.v. to both group rats. The results were expressed as the percent uptake of injected dose per gram of organ (%ID/g), the bacterial infected and sterile inflamed muscles. Binding of [¹³¹I]apigenin to the infected thigh muscle (target muscle = T) and normal thigh muscle (non-target muscle = NT) ratio (T/NT = 4.51 at 15 min) was higher than binding to bacterial inflamed muscle (T/NT = 2.25 at 15 min) of rats. [¹³¹I]apigenin showed good localization in both inflamed tissues. This uptake in the sterile inflamed tissue is higher than bacterial infected tissue. [¹³¹I]apigenin might be useful for imaging of inflamed tissues. However, it is not discriminate sterile inflamed tissue from bacterial infected tissue.     

Preparation of <Superscript>125</Superscript>I-celecoxib with high purity as a possible tumor agent

A preparation of ¹²⁵I-celecoxib is carried out via an electrophilic substitution reaction. The reaction parameters studied were celecoxib concentration, reaction temperature, pH of the reaction mixture and kinds of oxidizing agents in order to obtain a high radiochemical yield of the ¹²⁵I-celecoxib. Using 3.7 MBq of Na¹²⁵I, 150 μg (3.9 mM (mmol/L)) of celecoxib, and 1.6 mM (mmol/L) of chloramine-T (CAT) as oxidant at pH 4 and 60 °C for 15 min a maximum radiochemical yield of ¹²⁵I-celecoxib (65%) was obtained. The labeled compound was separated and purified by means of high pressure liquid chromatography (HPLC). The biological distribution in infected mice indicates the suitability of radioiodinated celecoxib as imaging of tumor.     

Synthesis and biological evaluation of novel 99mTc‐oxo and 99mTc‐tricarbonyl complexes with C3′‐functionalized thymidine dithiocarbamate for tumor imaging

A novel C3′‐functionalized thymidine dithiocarbamate derivative (3’DTC‐TdR) was successfully synthesized and labelled using [^99mTcO]³⁺ core and [^99mTc(CO)₃(H₂O)₃]⁺ core with high yields. The structures of the ^99mTc complexes were verified by preparation and characterization of the corresponding stable rhenium complexes. Both of the complexes were lipophilic and stable in vitro. Cell internalization experiments indicated that the uptakes of ^99mTcO‐3’DTC‐TdR were related to nucleoside transporters. Biodistribution of these complexes in mice bearing tumor showed that they had high tumor uptakes, good tumor/muscle ratios and tumor/blood ratios. Especially for ^99mTcO‐3’DTC‐TdR, it exhibited the highest tumor/muscle ratio and tumor/blood ratio at 4 h post‐injection. SPECT/CT imaging studies indicated clear accumulation in tumor, suggesting ^99mTcO‐3’DTC‐TdR would be a promising candidate for tumor imaging.