99mTc‐HYNIC‐(Ser)3‐J18 peptide: A radiotracer for non‐small‐cell lung cancer targeting

Radiolabeled peptide could be a useful tool for the diagnosis of non‐small‐cell lung cancer (NSCLC). In this study, HYNIC‐(Ser)₃‐J18 peptide was labeled with ^99mTc using EDDA/tricine as coligands. The in vitro and in vivo studies of this radiolabeled peptide were performed for cellular‐specific binding and tumor targeting in A‐549 cells and tumor‐bearing mice, respectively. The high radiochemical purity was obtained and this radiolabeled peptide exhibited high stability in buffer and serum. The radiolabeled peptide showed high affinity for the A‐549 cells with a dissociation constant value (K_D) of 4.4 ± 0.8 nm . The tumor–muscles ratios were 2.7 and 4.4 at 1 and 2 hr after injection of ^99mTc‐(EDDA/tricine)‐HYNIC‐(Ser)₃‐J18 in tumor‐bearing mice. The tumor uptake was decreased after preinjection with non‐labeled peptide for this radiolabeled peptide in blocking experiment. The results of this study showed the ^99mTc‐(EDDA/tricine)‐(Ser)₃‐HYNIC‐J18 peptide might be a promising radiolabeled peptide for NSCLC targeting.     

New neurotensin analogue radiolabeled by 99m‐technetium as a potential agent for tumor identification

It has been shown that more than 75% of ductal pancreatic adenocarcinomas overexpressed neurotensin (NT) receptors. Overexpression of NT receptors has been reported in various human tumor types. Hence, a non‐invasive diagnosis and staging method could be very beneficial. In this work, we describe radiolabeling and evaluation of new neurotensin analogues to target neurotensin receptor‐positive tumors such as pancreatic carcinoma. Radiolabeling was performed at 95°C for 10 min using ^99mTc in the presence of tricine/EDDA exchange labeling. Radiochemical yield analysis involved ITLC and HPLC methods. A binding assay test was carried out in nine different concentrations of labeled neurotensin analogues in HT‐29 cells. Radiopeptide‐specific binding and internalization were studied in NT receptors expressing HT‐29 cells. Biodistribution studies were performed in tumor‐free BALB/c mice and HT‐29 xenografted tumor‐bearing nude mice. The peptide was efficiently labeled by ^99mTc with high radiochemical yields (>98%). The radioconjugate was thoroughly stable in the solution and human serum even for 24 hr. The radiolabeled peptide showed high affinity (32.66 ± 4.01 nm ) and specificity internalization (>%18 after 4 hr) to HT‐29 cells. The radiopeptide efficiently showed tumor size and location in tumor‐bearing nude mice. In biodistribution, a receptor‐specific uptake of radiopeptide was observed in neurotensin receptor‐positive organs such as intestine. Uptake in the tumor was 4.59 ± 0.23% ID/g after 2 hr. Owing to excellent stability, high affinity, rapid blood clearance, low accumulation in non‐target organs, and high uptake in tumor, the ^99mTc–HYNIC‐peptide is a potential agent for targeting of NTR‐overexpressing tumor cells in clinical surroundings. When successfully executed in the clinical surrounding, non‐invasive imaging of NTR‐positive tumors with ^99mTc‐labeled new neurotensin analogues could facilitate therapy procedure and monitoring.     

Preparation via coligand exchange and characterization of [99mTc‐EDDA‐HYNIC‐D‐Phe1,Tyr3]Octreotide (99mTc–EDDA/HYNIC–TOC)

[^99mTc‐EDDA–HYNIC‐D‐Phe¹,Tyr³]octreotide (^99mTc‐EDDA/HYNIC–TOC) is a promising new agent with the potential to replace [¹¹¹In‐DTPA‐D‐Phe¹]‐octreotide in somatostatin receptor scintigraphy. This hydrazinonicotinic acid derivatized somatostatin complex contains ethylenediamine N,N′ diacetic acid (EDDA) as a coligand resulting in a high in vitro and in vivo stability. Since direct ^99mTc‐labelling of HYNIC–TOC with EDDA results in low labelling yields, in this study we describe the preparation of ^99mTc‐EDDA/HYNIC‐TOC via coligand exchange from Tricine for EDDA. Exchange of coligands is achieved at elevated temperature and under optimized conditions of pH, EDDA concentration and stannous ion. High labelling yields (mean 95.9%) were achieved at high specific activities (>37GBq/µmol). Characterization via HPLC, receptor binding and LC–MS of the resulting complex is described. The formulation developed enables rapid and simple labelling of ^99mTc‐EDDA/HYNIC–TOC in a manner suitable for a clinical setting. Copyright © 2003 John Wiley & Sons, Ltd.     

A 99mTc‐tricine‐HYNIC‐labeled peptide targeting the neurotensin receptor for single‐photon imaging in malignant tumors

In this study, a new neurotensin (NT) analog was labeled with ^99mTc via HYNIC chelator and tricine as coligand and investigated further. An NT (7–13) analog was prepared, and labeling with ^99mTc was performed. The internalization rate and biodistribution of radiopeptide were studied in HT‐29 cells and nude mice bearing tumor, respectively. Radiolabeling with ^99mTc was performed at high specific activities (54 MBq/nmol) with an acceptable labeling yield (>95%). In vitro cell line studies showed a specific internalization uptake up to 13.23 ± 0.45% during 4 h which was blocked in the presence of excess cold peptide to 0.83 ± 0.15%. In biodistribution studies, uptake was observed in NT receptor‐positive organs so that after 1 h the uptakes in mouse intestine and tumor were 1.23 ± 0.16% ID/g and 1.12 ± 0.11% ID/g, respectively. In animals co‐injected with excess cold peptide, reduction uptake in tumor and intestines were 73% (1.10% vs. 0.29% ID/g at 4 h) and 61% (1.22% vs. 0.47% ID/g at 4 h) respectively. Predominant renal excretion pathway with a highest accumulation of activity in bladder was observed for this radiopeptide. This radiolabeled peptide could be a candidate for detection of NT positive tumors.     

On the 99mTc‐labeling of isoniazid with different 99mTc cores

Recent advances in the chemistry of radiolabeling with ^99mTc such as use of the ^99mTc tricarbonyl and ^99mTc–HYNIC cores have revived interest in ^99mTc‐labeling of small biomolecules and further investigation as potential radiopharmaceuticals. Isoniazid, a drug commonly used for treatment of tuberculosis, has been chosen for the present study. Three distinct strategies were utilized to radiolabel isoniazid with ^99mTc. In the direct labeling protocol, the hydrazino amide functional group of isoniazid was used for ^99mTc‐labeling in the HYNIC sense using tricine and EDDA as co‐ligands. The other strategies of ^99mTc‐labeling involved the derivatization of isoniazid to its N, N‐diacetic acid derivative, which in turn was either used as a tridentate ligand for labeling with the [^99mTc(CO)₃(H₂O)₃]⁺ synthon or directly labeled by the conventional route wherein ^99mTc is in the +3 oxidation state. The complexes prepared in >95% yields were characterized by paper chromatography, thin layer chromatography and HPLC. Comparison of the three approaches showed that maximum specific activity and stability was obtained in the ^99mTc–isoniazid derivative synthesized via the tricarbonyl method. However, in vitro cell‐binding studies indicated that none of the ^99mTc–isoniazid complexes prepared had any appreciable uptake in Mycobacterium tuberculosis. Copyright © 2005 John Wiley & Sons, Ltd.     

Preparation and comparative evaluation of 99mTc‐HYNIC‐cNGR and 99mTc‐HYNIC‐PEG2‐cNGR as tumor‐targeting molecular imaging probes

The tripeptide sequence asparagine‐glycine‐arginine (NGR) specifically recognizes aminopeptidase N (APN or CD13) receptors highly expressed on tumor cells and vasculature. Thus, NGR peptides can precisely deliver therapeutic and diagnostic compounds to CD13 expressing cancer sites. In this regard, 2 NGR peptide ligands, HYNIC‐c(NGR) and HYNIC‐PEG₂‐c(NGR), were synthesized, radiolabeled with ^99mTc, and evaluated in CD13‐positive human fibrosarcoma HT‐1080 tumor xenografts. The radiotracers, ^99mTc‐HYNIC‐c(NGR) and ^99mTc‐HYNIC‐PEG₂‐c(NGR), could be prepared in approximately 95% radiochemical purity and exhibited excellent in vitro and in vivo stability. The radiotracers were hydrophilic in nature with log P values being ?2.33 ± 0.05 and ?2.61 ± 0.08. The uptake of 2 radiotracers ^99mTc‐HYNIC‐c(NGR) and ^99mTc‐HYNIC‐PEG₂‐c(NGR) was similar in nude mice bearing human fibrosarcoma HT‐1080 tumor xenografts, which was significantly reduced (P < .05) during blocking studies. The 2 radiotracers being hydrophilic cleared rapidly from blood, liver, and intestine and were excreted through renal pathway. The pharmacokinetics of ^99mTc‐labeled HYNIC peptide could not be modulated through introduction of PEG₂ unit, thus posing a challenge for studies with other linkers towards enhanced tumor uptake and retention.     

An improved radiolabelled RNA aptamer molecule for HER2 imaging in cancers

Abstract

Human epidermal growth factor receptor 2 (HER2) expression has been shown to be increased in several types of human tumours. In this study, for the imaging of HER2-related tumours, a modified RNA aptamer with HER2-specific targeting was labelled with ^99mTc, by using hydrazino nicotinamide (HYNIC) as the chelator in the presence of tricine or ethylenediamine-N,N′-diacetic acid (EDDA) as the co-ligand. Stability testing of the radiolabelled aptamers in the serum was performed through SDS-PAGE. The aptamer–radionuclide conjugate was evaluated for its cellular HER2-specific binding in ovarian cancer cells (SKOV-3), and its biodistribution properties were assessed in normal and SKOV-3 tumour-bearing mice. In the presence of either tricine or EDDA, the HYNIC-RNA aptamers were labelled with ^99mTc at a high yield and radiochemical purity. Cellular experiments confirmed the specific binding of the RNA aptamer to the HER2 receptor. In the animal biodistribution study, uptake of the EDDA-co-liganded ^99mTc-HYNIC-RNA aptamer by the liver and spleen was remarkably lower than that of the aptamer with tricine. Tumours also showed a higher accumulation of radioactivity with the EDDA-co-liganded aptamer complex. This study demonstrated EDDA to be better than tricine for use as a co-ligand with the RNA aptamer, which can be a potential tool for the molecular imaging of HER2-overexpressing cancers.     

99mTc‐labeled NGR‐chlorambucil conjugate, 99mTc‐HYNIC‐CLB‐c(NGR) for targeted chemotherapy and molecular imaging

Targeted delivery of chemotherapeutic drug at the tumor site enhances the efficacy with minimum systemic exposure. Towards this, drugs conjugated with peptides having affinity towards a particular molecular target are recognized as affective agents for targeted chemotherapy. Thus, in the present study, tumor‐homing asparagine‐glycine‐arginine (NGR) peptide ligand was conjugated to DNA alkylating nitrogen mustard, chlorambucil (CLB). The peptide‐drug conjugate (PDC), CLB‐c(NGR), was radiolabeled with ^99mTc‐HYNIC core to trace its pharmacokinetics and biodistribution pattern. In vitro cell‐binding studies of ^99mTc‐HYNIC‐CLB‐c(NGR) were conducted in murine melanoma B16F10 cells. The cytotoxicity studies conducted by incubation of the peptide/drug/PDC with B16F10 cells demonstrated enhanced cytotoxic effect of PDC in comparison to either the peptide or the drug alone. In vivo biodistribution studies in C57BL6 mice bearing melanoma tumor showed maximum tumor uptake at 30 minutes pi (2.45 ± 0.28% ID/g), which reduced to 0.77 ± 0.1% ID /g at 3 hours pi. The radiotracer being hydrophilic cleared rapidly from the heart, lungs, liver, and muscle. The tumor‐to‐blood and tumor‐to‐muscle ratios improved with time. This study opens avenues for conjugation of other targeting peptides with the drug CLB for enhanced toxicity at the diseased site.     

99mTc‐tricarbonyl labeling of paclitaxel as an antimicrotubule agent and its evaluation in B16‐F10 melanoma tumor‐bearing mice

In the present study paclitaxel (taxol) was labeled with [^99mTc(CO)₃(H₂O)₃]⁺ core. Labeling was optimized, and radiochemical analysis was determined by thin layer chromatography and high performance liquid chromatography. Radiocomplex was evaluated and verified further as a tumor characterization agent in B16‐F10 melanoma tumor‐bearing mice. The [^99mTc(CO)₃(H₂O)₃]⁺‐paclitaxel complex with high specific activity (0.77 GBq/μmol) and labeling yield (96.8 ± 1.3) was obtained. No decrease in labeling was observed up to 6 hours, and the stability of the radiocomplex was found adequate. Our main achievement was high accumulation of radiolabeled paclitaxel in tumor (4.51 ± 0.65 percentage injected dose per gram [%ID/g] at 2‐h postinjection) followed by significant reduction (1.86 ± 0.27%ID/g) at 4‐hour postinjection. Because paclitaxel is a substrate for multidrug resistance, ^99mTc‐tricarbonyl‐paclitaxel imaging would be useful for tumor characterization rather than tumor detection.     

Synthesis and evaluation of a 99mTc‐labeled tubulin‐binding agent for tumor imaging

Cholchicine and its derivatives are very potent tubulin‐binding compounds and can be used as a potential tumor targeting agents. In this study, colchicine was labeled with ^99mTc via hydrazinonicotinic acid (HYNIC) and was investigated further. HYNIC/cholchicine was synthesized and labeling with ^99mTc was performed at 95 °C for 15 min and radiochemical analysis included HPLC method. The stability of radiconjugate was checked in the presence of human serum at 37 °C up to 24 h. Biodistribution was studied in breast tumor‐bearing mice. Labeling yield of 95.8 ± 0.54% was obtained corresponding to a specific activity of 54 MBq/µmol. Radioconjugate showed good stability in the presence of human serum. Biodistribution studies in tumor‐bearing mice showed that ^99mTc/HYNIC/colchicine conjugate accumulated in tumor with good uptake (3.17 ± 0.14% g/g at 1 h post‐injection). The radioconjugate was cleared fast from normal organs and showed clearance through urinary and hepatobiliary systems with accumulation of activity in kidneys and intestine. This radioconjugate may be useful to assess the presence of tumor by imaging.     

99mTc‐anti‐epidermal growth factor receptor nanobody for tumor imaging

Nanobodies are important biomolecules for tumor targeting. In this study, we synthesized and labeled anti‐epidermal growth factor receptor (EGFR) nanobody OA‐cb6 with ^99mTc(CO)₃⁺ and evaluated its characteristics for targeting the EGFR in the A431 human epidermal carcinoma cell line. Nanobody radiolabeling was achieved with high yield and radiochemical purity, and the radioconjugate was stable. Biodistribution results in nude mice exhibited a favorable tumor‐to‐muscle ratio at 4‐hr postinjection, and tumor location was visualized at 4 hr after injection of radiolabeled nanobody. Our result showed that the OA‐cb6‐^99mTc‐tricarbonyl radiolabeled nanobody is a promising radiolabeled biomolecule for tumor imaging in cancers with high EGFR overexpression.     

Kit with technetium‐99m labelled antimicrobial peptide UBI 29‐41 for specific infection detection

The purpose of this study was to investigate radiochemical and biological characteristics of an instant kit for the preparation of ^99mTc‐labelled UBI 29‐41 for specific detection of infections. The kit is based on ^99mTc‐labelling via HYNIC conjugated to the terminal amine of the peptide, producing a well‐understood labelled compound. One hour after the addition of fresh ^99mTcO to the kit ITLC and HPLC reverse‐phase analysis was performed. Stability of the labelled complex was challenged and the binding to bacterial pellets was assessed. Finally, the biodistribution and accumulation in MRSA‐infected tissues were studied using scintigraphy and ex vivo countings. Data were compared to a non‐kit control method. Radiochemical analysis indicated >96% labelling, stability for 24 h and the preparation was used without purification. In vitro studies showed 41% of radioactivity was bound to bacteria. After injection into mice with a bacterial infection the site of infection was visualized within 30 min. Kit prepared ^99mTc‐HYNIC‐UBI 29‐41 was rapidly (half‐life 113 min) cleared via the kidneys and urinary bladder, essentially slower than control peptide (half‐life 74 min). This slower clearance results in higher activities in blood and other tissues. Nevertheless, ^99mTc‐HYNIC‐UBI 29‐41 shows favourable radiochemical characteristics and deserves further evaluation in a clinical setting. Copyright © 2005 John Wiley & Sons, Ltd.     

Synthesis,quality control,and bio‐evaluation of 99mTc‐cyclophosphamide

Cancer is found to be the leading cause of death worldwide characterized by uncontrolled cell division. Nuclear medicines imaging using radiopharmaceuticals have pronounced potential for the diagnosis and treatment of cancers. Cyclophosphamide (CPH) is an antineoplastic drug which targets selectively cancer cells. In the present work, labeling of CPH with Tc‐99m is performed for diagnostic purpose, which gave labeling yield as high as 99% using 20 μg SnCl₂·2H₂O, 200 μg of ligand at pH 7 for 10 min reaction time at room temperature. The characterization of the prepared complex was performed using ITLC, electrophoresis, and HPLC. In vitro stability was analyzed in the presence of human serum at 37°C which has maximum value of 94 ± 0.5. The biodistribution studies of ^99mTc‐CPH were performed in normal and tumor bearing Swiss Webster mice. The high accumulation of ^99mTc‐CPH was observed in liver and tumours respectively at 4 hr after injection. Biodistribution results revealed that ^99mTc‐CPH may be a potential tumour diagnostic agent simultaneously with chemotherapy.     

Synthesis and comparative in vivo evaluation of 99mTc(CO)3‐labeled PEGylated and non‐PEGylated cRGDfK peptide monomers

This work aimed at studying the effect of insertion of medium PEG (PEG₇) on the pharmacokinetic behavior of cRGDfK peptide in comparison with the non‐PEGylated analogue. The cRGDfK peptide has thus been derivatized at ε‐amino group of lysine by conjugation with N₃–PEG₇–COOH/N₃–CH₂–COOH to prepare a PEGylated and a non‐PEGylated analogue of cRGDfK. A tridentate chelator was then incorporated by click chemistry conjugation of the two peptide azides for radiolabeling with [^99mTc(CO)₃(H₂O)₃]⁺ precursor. Comparative in vivo evaluation of the two ^99mTc(CO)₃‐labeled radiotracers, ^99mTc(CO)₃–Pra–Tz–CH₂–cRGDfK 5 and ^99mTc(CO)₃–Pra–Tz–PEG₇–cRGDfK 6 , was carried out in C57BL/6 mice bearing α_vβ₃‐positive melanoma tumors to determine their potential toward targeting integrin α_vβ₃ receptors. The radiotracers exhibited excellent stability in saline as well as in serum. Maximum tumor uptake for the two radiotracers was observed at 30 min p.i. ( 5 : 3.0 ± 0.7% ID/g; 6 : 4.1 ± 0.5% ID/g). The two neutral ^99mTc(CO)₃ radiotracers prepared exhibited receptor‐mediated uptake in melanoma tumor. The increase in the tumor uptake on introduction of PEG₇ unit was accompanied by slower clearance from other organs which resulted in decreased target‐to‐background ratios. The in vivo kinetics of ^99mTc(CO)₃‐labeled radiotracer, ^99mTc(CO)₃–Pra–Tz–CH₂–cRGDfK 5 with only methylene unit as the spacer, was found to be more favorable due to higher tumor/blood, tumor/liver, tumor/kidney, and tumor/lung ratios.     

In vitro evaluation of 99mTc-EDDA/tricine-HYNIC-Q-Litorin in gastrin-releasing peptide receptor positive tumor cell lines

Abstract

Bombesin and its derivatives exhibit a high affinity for gastrin-releasing peptide receptor (GRPr), which is over-expressed in a variety of human cancers (prostate, pancreatic, lung, etc.). The aim of this study was to investigate the in vitro potential of the hydrazinonicotinamide (HYNIC)-Q-Litorin. ^99mTc labeling was performed by using different co-ligands: tricine and ethylenediamine diacetic acid (EDDA). The radiochemical stability of radiolabeled peptide conjugates was checked at room temperature and in cysteine solution up to 24?h. The in vitro cell uptake of ^99mTc-EDDA-HYNIC-Q-Litorin and ^99mTc-tricine-HYNIC-Q-Litorin were evaluated on pancreatic tumor and control cell lines. Optimum specific activity and incubation time were determined for all the cell lines. The results showed that the cell uptake of the radiolabeled peptide conjugates in tumor cell lines were higher than in the control cell line. The findings of this study indicated the need for further development of in vivo study as a radiopharmaceutical for pancreatic tumor imaging.     

An improved kit formulation for one‐pot synthesis of [99mTc]Tc‐HYNIC‐E[c(RGDfK)]2 for routine clinical use in cancer imaging

Radiolabeled Arg‐Gly‐Asp (RGD) peptide derivatives have immense potential for non‐invasive monitoring of malignancies overexpressing integrin α_vβ₃ receptors. Easy availability of suitable radiotracers would augment the utility of this class of molecular imaging agents. Towards this, the present article describes the development of an improved lyophilized kit for the routine clinical formulation of [^99mTc]Tc complex of HYNIC‐conjugated dimeric cyclic RGD peptide derivative E‐[c(RGDfK)]₂ (E = glutamic acid, f = phenyl alanine, K = lysine) without using Sn²⁺ and systematic evaluation of its efficacy. Five batches of the kits were prepared, and [^99mTc]Tc‐HYNIC‐E[c(RGDfK)]₂ radiotracer was synthesized with high radiochemical purity (98.6 ± 0.5%) and specific activity (124.8 GBq/μmol) using the kits. Biodistribution studies in C57BL/6 mice bearing melanoma tumor exhibited significant accumulation of the radiotracer in tumor (5.32 ± 0.56 %ID/g at 60 min p.i.), and this uptake was also found to be receptor‐specific by blocking studies. Preliminary human clinical investigations carried out in 10 breast cancer patients revealed high radiotracer uptake in the tumor along with good tumor‐to‐background contrast. The developed kit formulation showed an exceptionally high shelf‐life of at least 18 months. These results demonstrated promising attributes of the developed kit formulation and warrant more extensive clinical investigations.     

Synthesis and biological evaluation of 99mTc(CO)3(IDA‐CPT) for tumor imaging

This work reports the synthesis, radiolabeling, and preliminary biodistribution results in tumor‐bearing mice of ^99mTc(CO)₃(IDA‐CPT). The novel camptothecin (CPT) derivate was successfully synthesized by conjugation of iminodiacetic acid (IDA) to camptothecin via a short carbonyl‐methylene linker. Radiolabeling was performed in high yield with [^99mTc(CO)₃]⁺ core to get ^99mTc(CO)₃(IDA‐CPT), which was hydrophilic and stable at room temperature. Biodistribution studies in tumor‐bearing mice showed that ^99mTc(CO)₃(IDA‐CPT) accumulated in the tumor with good uptake and retention. However, its clearance from normal organs was slow, resulting in poor T/NT ratios. Further modification on the linker or/and ^99mTc‐chelate to improve the tumor‐targeting efficacy and in vivo kinetic profiles is currently in progress. Copyright © 2009 John Wiley & Sons, Ltd.     

Tumor targeting with a 99mTc-labeled AS1411 aptamer in prostate tumor cells

AS1411, a 26-base guanine-rich oligonucleotide aptamer, has high affinity to nucleolin, mainly on tumor cell surfaces. In this study, a modified AS1411 was labeled with ^99mTc and evaluated as a potential tumor-targeting agent for imaging. The AS1411 aptamer was conjugated with HYNIC and labeled with ^99mTc in the presence a co-ligand. Radiochemical purity and stability testing of the ^99mTc–HYNIC–AS1411 aptamer were carried out with thin layer chromatography and a size-exclusion column in normal saline and human serum. Cellular nucleolin-specific binding, cellular internalization in DU-145 cells, as high levels of nucleolin expression, were performed. Additionally, biodistribution in normal mice and DU-145 tumour-bearing mice was assessed. Radiolabeling of the aptamer resulted in a reasonable yield and radiochemical purity after purification. The aptamer was stable in normal saline and human serum, and cellular experiments demonstrated specific binding of the AS1411 aptamer to the nucleolin protein. Based on biodistribution assessment of ^99mTc–HYNIC–AS1411, rapid blood clearance was seen after injection and it appears that the excretion route was via the urinary system at 1?h post-injection. Tumours also showed a higher accumulation of radioactivity with this labeled aptamer. ^99mTc–AS1411 can be a potential tool for the molecular imaging of nucleolin-overexpressing cancers.     

Initial evaluation of 99mTc‐tricarbonyl‐cyclopentadienyl fatty acids derivatives as SPECT tracers for myocardium

Fatty acids are myocardial metabolic agent for detecting myocardial ischemia and infraction. However, no ^99mTc‐labeled fatty acids had potential use in clinical practice. In this study, ^99mTc‐CpTT‐10‐oxo‐para‐PPA ( 1d ), ^99mTc‐CpTT‐11‐oxo‐para‐PPA ( 2d ), ^99mTc‐CpTT‐12‐oxo‐para‐PPA ( 3d ), ^99mTc‐CpTT‐11‐oxo‐ortho‐PPA ( 4d ), and ^99mTc‐CpTT‐11‐oxo‐meta‐PPA ( 5d ) were synthesized by a double ligand transfer reaction, and their biological behaviors were investigated. Compound 2d achieved good heart to blood ratio (3.39 at 5 min after intravenous), and 2d showed high‐heart uptake of 6.20% ID/g at 5 minutes after injection. Compound 3d displayed a prolonged retention in the myocardium (1.43% ID/g at 60 min after injection). Radioactivity accumulation in the lungs, spleen, and blood was eliminated rapidly. In vivo, metabolite analysis presented that compound 6d may be metabolite of 2d through β‐oxidation in tissue. Unfortunately, the biodistribution studies of 1d , 2d , 3d , 4d , and 5d showed fast heart clearance and poor heart to liver ratios, which suggested that the 5 ^99mTc‐labeled fatty acid analogues cannot be used for diagnosis.     

Design of 99mTc‐DTPA‐CLP and Preliminary Evaluation in Rats

Radiopharmaceuticals are localized in (malignant) tumor tissues by different mechanisms. One of these mechanisms, gelatinase enzyme activity, is associated with poor prognosis in cancer patients and potential targets for tumor imaging. There are some gelatinases to be associated with metastatic potential for tumor imaging to possibly predict metastases. In this study, a cyclic decapeptide conjugate, DTPA‐CLP (DTPA‐Cys‐Leu‐Pro‐Gly‐His‐Trp‐Gly‐Phe‐Pro‐Ser‐Cys), was selected as a peptide conjugate because of its selective inhibitory activity toward gelatinases. Peptide‐conjugated DTPA‐CLP was labeled with ^99mTc with a radiolabeling efficiency of 97.0 ± 2.8%. After determining optimization conditions for radiolabeling, a biodistribution study of radiolabeled peptide in albino Wistar rats was performed. According to biodistribution data, ^99mTc‐DTPA‐CLP showed high uptake in the lung, liver, uterus, and spleen. These results show that ^99mTc‐DTPA‐CLP may be used for the imaging of gelatinase activity in metastatic tumors.