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Since the therapeutic effect of boron neutron capture therapy is influenced by the intracellular distribution profile of boronoagents containing

Tumor-induced osteomalacia (TIO) is caused by typically small tumors that secrete fibroblast growth factor 23 (FGF23). As tumor resection is the only effective treatment for TIO, it is important to detect the culprit tumor. We aimed to assess the utility of 68Gallium-DOTA-D-Phe(1)-Tyr(3)-octreotide (68Ga-DOTATOC) PET/CT in TIO and the correlation between biochemical parameters and the PET/CT results. Thirty-five patients with clinically suspected TIO who had undergone 68Ga-DOTATOC PET/CT were retrospectively analyzed. 68Ga-DOTATOC PET/CT results were compared with biochemical parameters and the final diagnosis, including histopathology. 68Ga-DOTATOC PET/CT detected focal uptake consistent with TIO in 21/35 patients, one of which was considered false positive. In 16 patients, the cause of osteomalacia was confirmed histologically as phosphaturic mesenchymal tumor (n = 15) or fibrous dysplasia (n = 1). The other four patients were judged clinically as true positive by subsequent MRI and the clinical course. Overall, the detection rate of 68Ga-DOTATOC PET/CT was 57% (20/35). Median tumor maximum standardized uptake value (SUVmax) was 6.9 (range 1.5–37.7). There was no significant difference in serum intact FGF23 level between DOTATOC-positive and DOTATOC-negative cases, and no significant correlation was observed between intact FGF23 level and tumor SUVmax. 68Ga-DOTATOC PET/CT was clinically useful in detecting culprit tumors and subsequent patient management in TIO.

Perinatal hypoxic ischemic encephalopathy (HIE) results in serious neurological dysfunction and mortality. Clinical trials of multilineage-differentiating stress enduring cells (Muse cells) have commenced in stroke using intravenous delivery of donor-derived Muse cells. Here, we investigated the therapeutic effects of human Muse cells in an HIE model. Seven-day-old rats underwent ligation of the left carotid artery then were exposed to 8% oxygen for 60 min, and 72 hours later intravenously transplanted with 1 × 104 of human-Muse and -non-Muse cells, collected from bone marrow-mesenchymal stem cells as stage-specific embryonic antigen-3 (SSEA-3)+ and −, respectively, or saline (vehicle) without immunosuppression. Human-specific probe revealed Muse cells distributed mainly to the injured brain at 2 and 4 weeks, and expressed neuronal and glial markers until 6 months. In contrast, non-Muse cells lodged in the lung at 2 weeks, but undetectable by 4 weeks. Magnetic resonance spectroscopy and positron emission tomography demonstrated that Muse cells dampened excitotoxic brain glutamatergic metabolites and suppressed microglial activation. Muse cell-treated group exhibited significant improvements in motor and cognitive functions at 4 weeks and 5 months. Intravenously transplanted Muse cells afforded functional benefits in experimental HIE possibly via regulation of glutamate metabolism and reduction of microglial activation.

Glucagon-like peptide-1 receptor agonist (GLP-1RA) has been reported to have therapeutic effects on diabetes and various diseases. Precise detection of GLP-1 receptor (GLP-1R) can be useful to diagnose and elucidate the mechanism of such diseases. Here we aimed to develop an imaging probe based on GLP-1RA that has high molar activity and sensitivity for detection of low-level GLP-1R expression in non-pancreatic diseases. We selected the agonist exenatide (Ex4) as the parent peptide of a GLP-1R targeting probe and prepared Cys-Ex4 by addition of an N-terminal Cys residue and labeling with the prosthetic agent N-(3-[125I]iodophenyl)maleimide ([125I]IPM) to generate [125I]Ex4ipm. We evaluated the affinity of [125I]Ex4ipm for GLP-1R, as well as cellular binding profiles in insulinoma and prostate cancer cell lines, and in vivo biodistributions in normal and tumor-bearing mice to assess GLP-1R-dependent accumulation of radioactivity in tissues. [125I]Ex4ipm was easily synthesized with high radiochemical yield (73%), radiochemical purity (> 99%), and molar activity (81 GBq/µmol) via a thiol/maleimide reaction. Following administration to mice, [125I]Ex4ipm accumulated to high levels in the pancreas (23.3% ID/g), with radioactivity co-localizing in areas having insulin-positive β cells. High amounts of radioactivity also accumulated in insulinomas that overexpressed GLP-1R (27.5% ID/g). In contrast, low amounts of [125I]Ex4ipm accumulation, corresponding to low expression levels of GLP-1R, were observed in prostate cancer cells and xenografts used as a model of non-pancreatic applications. Our results suggested that [123I]Ex4ipm could be valuable for GLP-1R imaging in diabetes, insulinomas, and various diseases related to GLP-1R.

ObjectiveAngiogenesis facilitates tumor survival and promotes malignancy. The vascular endothelial growth factor (VEGF)/VEGF receptor (VEGFR) tyrosine kinase (TK) signaling pathway is a key factor mediating angiogenesis, suggesting that this pathway may be a target for diagnosis and therapy. In this study, we aimed to develop small molecule radioiodinated probes applicable for in vivo VEGFR imaging considering the versatility and usefulness of single photon emission computed tomography (SPECT).MethodsWe designed and synthesized 4 radioiodinated anthranilate compounds (6a–d) based on the structure of an anticancer drug targeting VEGFR-TK. The inhibitory potencies of corresponding cold compounds 4a–d and in vitro stability of compounds 6a–d were assessed by cellular proliferation inhibition assays and radio thin-layer chromatography after incubation in neutral solution. In vivo biodistributions were evaluated by determining radioactivity in tissues of interest after intravenous injection of test compounds in tumor-bearing mice. In vitro and in vivo blocking experiments using a selective VEGFR-TK inhibitor and SPECT/computed tomography (CT) imaging were performed in tumor-bearing mice.ResultsThe radioiodinated compounds 6a–d were obtained with more than 68.0% radiochemical yield and more than 95% radiochemical purity. Because compounds 4a–d showed high inhibitory potencies and compounds 6c and 6d showed high in vitro stability, 6c ([125I]m-NPAM) and 6d ([125I]p-NPAM) were further evaluated. Analysis of the in vivo biodistribution revealed a tumor to blood radioactivity ratio of greater than 4 at 24 h after [125I]p-NPAM administration. Accumulation of radioactivity in cultured tumor cells and tumor xenografts after [125I]p-NPAM administration was significantly blocked by inhibitor pretreatment. Tumors were clearly imaged at 24 h after [125I]p-NPAM injection with SPECT/CT in comparison to that in inhibitor-pretreated tumor-bearing mice.Conclusions[125I]p-NPAM may have potential applications as a lead compound for future development of a clinically usable VEGFR imaging probe for SPECT.

Integrin αvβ3 is an effective marker of angiogenesis in cancer, and αvβ3-specific imaging can yield important details about this complex physiological process. We utilized the recently reported and highly αvβ3-specific peptide, bicyclic RGD (bcRGD), as the basic structure of an in vivo αvβ3 imaging probe, and synthesized a radioiodinated form of bcRGD, namely [125I]bcRGD, with high radiochemical purity (>99%) and high molar activity (81 GBq/μmol). As expected, [125I]bcRGD exhibited high selectivity for αvβ3 compared with αvβ5 and α5β1 in vitro. [125I]bcRGD showed significantly higher accumulation in U-87MG cells (1.6% dose/mg) with high expression of αvβ3 compared to A549 cells (0.3% dose/mg) with only moderate expression. Furthermore, 30 min after administration to tumor-bearing mice, [125I]bcRGD showed significantly higher accumulation in U-87MG tumors (3.8% ID/g) than in A549 tumors (2.1% ID/g), and the radioactivity accumulation ratios of U-87MG tumor/blood and U-87MG tumor/muscle were 4.0 and 6.0, respectively. These results highlight the promising properties of [123/125I]bcRGD for use as an in vivo αvβ3 imaging probe, as well as the utility of bcRGD as a basic structure of molecular probes for both imaging and therapeutic applications. bcRGD may exhibit broad use in future theranostics applications targeting integrin αvβ3-related diseases.

Boron neutron capture therapy (BNCT) is an attractive approach to treating cancers. Currently, only one 10B-labeled boronoagent (Borofalan, BPA) has been approved for clinical BNCT in Japan, and methods for predicting and measuring BNCT efficacy must be established to support the development of next-generation 10B-boronoagents. Fluorescence sensors targeting boronic acids can achieve this because the amount and localization of 10B in tumor tissues directly determine BNCT efficacy; however, current sensors are nonoptimal given their slow reaction rate and weak fluorescence (quantum yield < 0.1). Herein, we designed and synthesized a novel small molecular-weight fluorescence sensor, BITQ, targeting boronic acids. In vitro qualitative and quantitative properties of BITQ were assessed using a fluorophotometer and a fluorescence microscope together with BPA quantification in blood samples. BITQ exhibited significant quantitative and selective fluorescence after reacting with BPA (post-to-pre-fluorescence ratio = 5.6; quantum yield = 0.53); the fluorescence plateaued within 1 min after BPA mixing, enabling the visualization of intracellular BPA distribution. Furthermore, BITQ quantified the BPA concentration in mouse blood with reliability comparable with that of current methods. This study identifies BITQ as a versatile fluorescence sensor for analyzing boronic acid agents. BITQ will contribute to 10B-boronoagent development and promote research in BNCT.

p38α, a member of the mitogen-activated protein kinase superfamily, is ubiquitously expressed in a variety of mammalian cells. Activated p38α induces inflammatory responses to external stimuli, suggesting that non-invasive detection of activated p38α would be valuable for diagnosing inflammatory diseases. For this purpose, we designed radiolabeled compounds [123I]2-IR and [123I]4-IR based on a potent p38α selective inhibitor R1487 for use with single photon emission computed tomography (SPECT). In this study, we used 125I instead of 123I due to its more usable radiochemical properties, synthesized [125I]2-IR and [125I]4-IR, and evaluated their effectiveness as activated p38α imaging probes. [123I]2-IR and [123I]4-IR were designed by introduction of a 123I atom at the 2- or 4-ositions of the phenoxy ring, preserving the pyrimidinopyridone structure of R1487. We synthesized 2-IR and 4-IR via a 7-step process. The inhibitory potencies of 2-IR, 4-IR, and p38α inhibitors were measured using an ADP-Glo™ kinase assay system. Radioiodination of 2-IR and 4-IR was performed via an organotin-radioiodine exchange reaction using the corresponding tributyltin precursors. Biodistributions were evaluated by determining radioactivity in tissues of interest after intravenous administration of [125I]2-IR and [125I]4-IR in normal ddY mice and turpentine oil-induced inflammation model mice. In vivo inhibition study was also performed in inflammation model mice after intravenous administration of [125I]4-IR with pretreatment of p38α inhibitors. We synthesized 2-IR and 4-IR at total yields of 17.5% and 19.2%, respectively. 4-IR had higher p38α inhibitory potency than 2-IR; both compounds were significantly less potent than R1487. [125I]2-IR and [125I]4-IR were successfully obtained from tributyltin precursors with high radiochemical yield (> 65%), purity (> 97%), and molar activity (~ 81 GBq/µmol). [125I]4-IR showed high radioactivity accumulation in the inflamed tissue (7.0 ± 1.2%D/g), rapid delivery throughout the body, and rapid blood clearance, resulting in a high inflammation-to-blood ratio (6.2 ± 0.4) and a high inflammation-to-muscle ratio (5.2 ± 1.3) at 30 min, while [125I]2-IR showed low radioactivity accumulation in inflamed tissue over the experimental period. Further, radioactivity accumulation in inflamed tissue after [125I]4-IR administration was significantly decreased by pretreatment with selective inhibitors. [123I]4-IR would be a promising imaging agent for detection of activated p38α.

Tumor-induced osteomalacia (TIO) is caused by typically small tumors that secrete fibroblast growth factor 23 (FGF23). As tumor resection is the only effective treatment for TIO, it is important to detect the culprit tumor. We aimed to assess the utility ofThirty-five patients with clinically suspected TIO who had undergone

Integrin α

Introduction Lactate could serve as an energy source and signaling molecule in the brain, although there is insufficient in vivo evidence to support this possibility. Here we aimed to use a one-pot enzymatic synthetic procedure to synthesize l -[3-11C]lactate that can be used to evaluate chemical forms in the blood after intravenous administration, and as a probe for pharmacokinetic analysis of lactate metabolism in in vivo positron emission tomography (PET) scans with normal and fasted rats. Methods Racemic [3-11C]alanine obtained from 11C-methylation of a precursor and deprotection was reacted with an enzyme mixture consisting of alanine racemase, d -amino acid oxidase, catalase, and lactate dehydrogenase to yield l -[3-11C]lactate via [3-11C]pyruvate. The optical purity was measured by HPLC. Radioactive chemical forms in the arterial blood of Sprague Dawley rats with or without insulin pretreatment were evaluated by HPLC 10 min after bolus intravenous injection of l -[3-11C]lactate. PET scans were performed on normal and fasted rats administered with l -[3-11C]lactate. Results l -[3-11C]Lactate was synthesized within 50 min and had decay corrected radiochemical yield, radiochemical purity, and optical purity of 13.4%, >95%, and >99%, respectively. The blood radioactivity peaked immediately after l -[3-11C]lactate injection, rapidly decreased to the minimum value within 90 s, and slowly cleared thereafter. HPLC analysis of blood samples revealed the presence of [11C]glucose (78.9%) and l -[3-11C]lactate (12.1%) 10 min after administration of l -[3-11C]lactate. Insulin pretreatment partly inhibited glyconeogenesis conversion leading to 55.4% as [11C]glucose and 38.9% as l -[3-11C]lactate simultaneously. PET analysis showed a higher SUV in the brain tissue of fasted rats relative to non-fasted rats. Conclusions We successfully synthesized l -[3-11C]lactate in a one-pot enzymatic synthetic procedure and showed rapid metabolic conversion of l -[3-11C]lactate to [11C]glucose in the blood. PET analysis of l -[3-11C]lactate indicated the possible presence of active lactate usage in rat brains in vivo.

Oxidized low-density lipoprotein (OxLDL) plays a pivotal role in atherosclerotic plaque destabilization, which suggests its potential as a nuclear medical imaging target. We previously developed radioiodinated 125I-AHP7, a peptide probe carrying a 7-residue sequence from the OxLDL-binding protein Asp-hemolysin, for specific OxLDL imaging. Although 125I-AHP7 recognized OxLDL, it had low stability. Thus, to improve stability, we designed radiolabeled 22-residue peptide probes, 125I-AHP22 and 111In-AHP22, which include the entire AHP7 sequence, and evaluated the stability, activity, and applications of these probes in vitro and in vivo. Probes consisting of a 21-residue peptide derived from the Asp-hemolysin sequence and an N-terminal Cys or aminohexanoic acid for labeling with 125I-N-(3-iodophenyl)maleimide or 111In diethylene triamine pentaacetic acid were termed 125I-AHP22 and 111In-AHP22. An in vitro-binding inhibition assay with OxLDL was performed using 125I-AHP7 as a radiotracer. Radioactivity accumulation in the atherosclerotic aorta and plasma intact fraction was evaluated 30 min after intravenous administration of probes in myocardial infarction-prone Watanabe heritable hyperlipidemic (WHHLMI) rabbits. 125I-AHP22 and 111In-AHP22 were synthesized in ~ 360 and 60 min, respectively, with > 98% radiochemical purities after RP-HPLC purification. An in vitro-binding assay revealed similar or greater inhibition of OxLDL binding by both In-AHP22 and I-AHP22 compared to I-AHP7. The fraction of intact 125I-AHP22 and 111In-AHP22 in plasma was estimated to be approximately tenfold higher than that of 125I-AHP7. Both probes were rapidly cleared from the blood. 111In-AHP22 had a 2.3-fold higher accumulation in WHHLMI rabbit aortas compared to control rabbits, which was similar to 125I-AHP7. However, 125I-AHP22 accumulated to similar levels in aortas of WHHLMI and control rabbits due to high nonspecific accumulation in normal aortas that could be due to high lipophilicity. 111In-AHP22, easily prepared within 1 h, showed moderate affinity for OxLDL, high stability in vivo, and high accumulation in atherosclerotic aortas. 111In-AHP22 could be a potential lead compound to develop future effective OxLDL imaging probes.

As matrix metalloproteinases (MMPs), especially MMP-9 and MMP-12 are involved in the pathological processes associated with chronic obstructive pulmonary disease (COPD), we developed a novel radiofluorinated probe, 18F-IPFP, for MMPs-targeted positron emission tomography (PET). 18F-IPFP was designed by iodination of MMP inhibitor to enhance the affinity, and labelled with a compact prosthetic agent, 4-nitrophenyl 2-18F-fluoropropionate (18F-NFP). As a result, IPFP demonstrated the highest affinity toward MMP-12 (IC50 = 1.5 nM) among existing PET probes. A COPD model was employed by exposing mice to cigarette smoke and the expression levels of MMP-9 and MMP-12 were significantly increased in the lungs. Radioactivity accumulation in the lungs 90 min after administration of 18F-IPFP was 4× higher in COPD mice than normal mice, and 10× higher than in the heart, muscle, and blood. Ex vivo PET confirmed the radioactivity distribution in the tissues and autoradiography analysis demonstrated that accumulation differences in the lungs of COPD mice were 2× higher than those of normal mice. These results suggest that 18F-IPFP is a promising probe for pulmonary imaging and expected to be applied to various MMP-related diseases for early diagnosis, tracking of therapeutic effects, and new drug development in both preclinical and clinical applications.

PURPOSE: Oxidized low-density lipoprotein (oxLDL) plays a key role in endothelial dysfunction, vascular inflammation, and atherogenesis. The aim of this study was to assess blood clearance and in vivo kinetics of radiolabeled oxLDL in mice. METHODS: We synthesized (123)I–oxLDL by the iodine monochloride method, and performed an uptake study in CHO cells transfected with lectin-like oxLDL receptor-1 (LOX-1). In addition, we evaluated the consistency between the (123)I–oxLDL autoradiogram and the fluorescence image of DiI-oxLDL after intravenous injection for both spleen and liver. Whole-body dynamic planar images were acquired 10 min post injection of (123)I–oxLDL to generate regional time-activity curves (TACs) of the liver, heart, lungs, kidney, head, and abdomen. Regional radioactivity for those excised tissues as well as the bladder, stomach, gut, and thyroid were assessed using a gamma counter, yielding percent injected dose (%ID) and dose uptake ratio (DUR). The presence of (123)I–oxLDL in serum was assessed by radio-HPLC. RESULTS: The cellular uptakes of (123)I–oxLDL were identical to those of DiI-oxLDL, and autoradiograms and fluorescence images also exhibited consistent distributions. TACs after injection of (123)I–oxLDL demonstrated extremely fast kinetics. The radioactivity uptake at 10 min post-injection was highest in the liver (40.8 ± 2.4% ID). Notably, radioactivity uptake was equivalent throughout the rest of the body (39.4 ± 2.7% ID). HPLC analysis revealed no remaining (123)I–oxLDL or its metabolites in the blood. CONCLUSION: (123)I–OxLDL was widely distributed not only in the liver, but also throughout the whole body, providing insight into the pathophysiological effects of oxLDL.

11C-Pittsburgh compound-B (11C-PIB) positron emission tomography (PET) is used to visualize and quantify amyloid deposition in the brain cortex in pathological conditions such as Alzheimer’s disease (AD). Intense 11C-PIB retention is also observed in the white matter (WM) of both healthy individuals and AD patients. However, the clinical implications of this retention in brain WM have not been clarified. We investigated the relationship between the extent of white matter lesions (WMLs) and the binding potential of 11C-PIB (BPND) in the WM in patients with hypertensive small vessel disease. We further examined the relationship between the extent of WMLs and BPND in WML and in normal-appearing white matter (NAWM). Twenty-one hypertensive vasculopathy patients, without AD and major cerebral arterial stenosis and/or occlusion, were enrolled (9 women, 68 ± 7 years). Regions of WML and NAWM were extracted using magnetization-prepared rapid gradient-echo and fluid-attenuated inversion recovery of magnetic resonance images. Volumes of interest (VOIs) were set in the cortex-subcortex, basal ganglia, and centrum semiovale (CS). BPND in the cortex-subcortex, basal ganglia, CS, WML, and NAWM were estimated on 11C-PIB PET using Logan graphical analysis with cerebellar regions as references. The relationships between WML volume and BPND in each region were examined by linear regression analysis. BPND was higher in the CS and basal ganglia than in the cortex-subcortex regions. WML volume had a significant inverse correlation with BPND in the CS (Slope = −0.0042, R 2 = 0.44, P

Matrix metalloproteinase-12 (MMP-12, macrophage elastase) is a member of the MMP family that is responsible for the degradation of extracellular matrix, and is associated with the inflammatory process of chronic obstructive pulmonary disease (COPD). COPD, characterized by progressive and irreversible airflow obstruction, is recently a major cause of mortality and morbidity worldwide. Herein, to develop radioiodinated probes for the early diagnosis of COPD, we designed and synthesized novel MMP-12-targeted dibenzofuran compounds (1–3) with a variety of linker structures (carbamate, amide, and sulfonamide). In competitive enzyme activity assays, it was revealed that the linker structures significantly affected the inhibitory activity against and selectivity for MMP-12. Compound 1, with carbamate linker, demonstrated potent MMP-12 inhibitory activity (IC50 = 8.5 nM) compared to compound 2, with amide linker, and compound 3, with sulfonamide linker. Using bromo-substituted carbamate 13 as a radioiodination precursor, [125I]1 was successfully prepared to high radiochemical purity (over 98%) and good specific radioactivity (4.1 GBq/μmol). These results suggest that radioiodinated compound 1 is potent as a novel MMP-12-targeted probe.

Monoamine oxidase B (MAO-B), predominantly expressed in glial cells, plays an important role in neurotransmitter regulation, and MAO-B activity relates to several neuronal diseases. Here, we aimed to develop a radiofluorinated MAO-B imaging probe based on the structure of a selective MAO-B inhibitor, MD-230254. We synthesized and evaluated a series of compounds in vitro and in vivo. A series of fluorinated analogs of MD-230254 were synthesized and evaluated for inhibitory potency and selectivity toward MAO-B. 5-[4-(2-[18 F]Fluorobenzyloxy)phenyl]-3-(2-cyanoethyl)-1,3,4-oxadiazol-2(3H)-one (2-[18 F]FBPO) was synthesized from a corresponding tributylstannyl precursor and [18 F]CH3 COOF. Biodistribution after intravenous injection of 2-[18 F]FBPO was evaluated in male ddY mice with or without pretreatment by inhibitors. Among the compounds synthesized and evaluated, 2-FBPO showed high inhibitory potency and selectivity toward MAO-B comparable with MD-230254. 2-[18 F]FBPO was successfully synthesized by an electrophilic reaction with a high radiochemical purity of more than 99%. 2-[18 F]FBPO was efficiently taken up by the brain and showed rapid blood clearance, which provided a brain/blood radioactivity ratio of 3.7 at 90 minutes postinjection. The brain radioactivity was significantly decreased by pretreatment with an MAO-B selective inhibitor. The great potential of 2-[18 F]FBPO as an MAO-B imaging probe, applicable to a variety of diseases, is indicated.

This article gives an overview of essential requirements and limitations in the quantitative assessment of regional myocardial perfusion or regional myocardial blood flow (rMBF) using existing clinical SPECT systems in clinical settings. One major requirement is the need for acquiring complete projection data without truncation. Attenuation and scatter are then prerequisites to reproduce quantitative images which should represent regional distribution of true radioactivity concentration in the myocardium. A compartmental model could then be applied to extract physiological myocardial perfusion from series of tomographic images acquired following i.v. radio ligand administration. There are also requirements in the radio-ligands if one wish to estimate quantitative blood flow for a physiologicaly wide range of flow. The most important factor is need for a high first-pass extraction fraction. Several factors that affect quantitative ability are reviewed and their importance is

Lactate could serve as an energy source and signaling molecule in the brain, although there is insufficient in vivo evidence to support this possibility. Here we aimed to use a one-pot enzymatic synthetic procedure to synthesize l-[3-Racemic [3-l-[3-We successfully synthesized l-[3

Oxidized low-density lipoprotein (OxLDL) plays a pivotal role in atherosclerotic plaque destabilization, which suggests its potential as a nuclear medical imaging target. We previously developed radioiodinatedProbes consisting of a 21-residue peptide derived from the Asp-hemolysin sequence and an N-terminal Cys or aminohexanoic acid for labeling with

A high-affinity and low-molecular-weight fluorescent Zn2+ sensor 1 based on a 2,2′-bipyridine scaffold, which functions as both the chelating moiety for Zn2+ and the fluorophore, was developed and evaluated in biological applications. Controlling the occurrence of tautomerism of the chelating moiety for Zn2+ by introducing an amino group at the 6-position of the pyridine ring dramatically increased the binding affinity toward Zn2+. Fluorescent sensor 1 exhibited a nanomolar-range dissociation constant (Kd = 2.2 nM), a large Stokes shift (140 nm), and an 8.6-fold turn-on response to Zn2+ under physiological conditions. Fluorescence images revealed that fluorescent sensor 1 exhibits good properties with respect to aqueous solubility and cell permeability and can quantitatively detect the Zn2+ levels in living cells. Furthermore, a 65Zn2+ radioactive zinc isotope uptake study revealed the real concentration of accumulated Zn2+ at the detection limit. The novel fluorescent sensor 1 is a promising sensor for use in biological applications.

Objective Positron emission tomography (PET)/computed tomography (CT) using 68Ga-labeled 1,4,7,10-tetraazacyclododecane-N,N′,N″,N‴-tetraacetic acid-d-Phe1-Tyr3-octreotide (DOTATOC) has been used to detect neuroendocrine tumors (NETs). The purpose of this study was to investigate the clinical efficacy of DOTATOC-PET/CT for detecting clinically suspected NETs when conventional imaging modalities were negative or inconclusive, in terms of additional value. Methods A total of 46 patients were analyzed retrospectively. Among them, 14 patients underwent a DOTATOC-PET/CT scan for detecting unknown primary tumors after histopathological confirmation of a NET at metastatic sites (group A): 7 patients for detecting metastasis or recurrence after surgery for NET because of their high hormone levels but with no recurrence detected by other imaging modalities (group B); the remaining 25 patients for detecting suspected NETs because their hormone levels were high with no history of histopathologically proven NET (group C). Additional information was assessed, according to each situation. Results In group A, unknown primary tumors were suspected by DOTATOC-PET/CT in 8 of 14 patients (gastrointestinal/pancreatic NET in 7 patients, prostatic cancer in 1 patient), but prostatic cancer was not confirmed by histopathology (i.e., false positive). In group B, DOTATOC-PET/CT depicted lesions in six of seven patients, including nodal metastasis (n = 5) and liver metastasis (n = 1). In group C, DOTATOC-PET/CT did not demonstrate any abnormal foci except in one case of pancreatic NET. Additional information was obtained in 50, 86, and 4 % of cases, in groups A, B, and C, respectively. Conclusions DOTATOC-PET/CT was useful for detecting NETs, especially when recurrence or metastases were suspected because of high hormone levels after surgery for a NET. It is unlikely, however, that additional information can be acquired in patients with no history of NET simply based on high hormone levels.

Membrane type-1 matrix metalloproteinase (MT1-MMP) plays pivotal roles in tumor progression and metastasis, and holds great promise as an early biomarker for malignant tumors. Therefore, the ability to evaluate MT1-MMP expression could be valuable for molecular biological and clinical studies. For this purpose, we aimed to develop short peptide-based nuclear probes because of their facile radiosynthesis, chemically uniform structures, and high specific activity, as compared to antibody-based probes, which could allow them to be more effective for in vivo MT1-MMP imaging. To the best of our knowledge, there have been no reports of radiolabeled peptide probes for the detection of MT1-MMP in cancer tissues. In this study, we designed and prepared four probes which consist of a MT1-MMP-specific binding peptide sequence (consisting of L or D amino acid isomers) and an additional cysteine (at the N or C-terminus) for conjugation with N-(m-[(123/125)I]iodophenyl) maleimide. We investigated probe affinity, probe stability in mice plasma, and probe biodistribution in tumor-bearing mice. Finally, in vivo micro single photon emission computed tomography (SPECT) imaging and ex vivo autoradiography were performed. Consequently, [(123)I]I-DC, a D-form peptide probe radioiodinated at the C-terminus, demonstrated greater than 1000-fold higher specific activity than previously reported antibody probes, and revealed comparably moderate binding affinity. [(125)I]I-DC showed higher stability as expected, and [(123)I]I-DC successfully identified MT1-MMP expressing tumor tissue by SPECT imaging. Furthermore, ex vivo autoradiographic analysis revealed that the radioactivity distribution profiles corresponded to MT1-MMP-positive areas. These findings suggest that [(123)I]I-DC is a promising peptide probe for the in vivo detection of MT1-MMP in cancers.

Positron emission tomography with 15O-labeled gases (15O-PET) is important for in vivo measurement of cerebral oxygen metabolism both in clinical and basic settings. However, there are currently no reports concerning 15O-PET in mice. Here, we developed an 15O-PET method applicable to mice with spontaneous respiration of 15O-gas without a tracheotomy catheter. Sequential 15O-PET was also performed in a mouse model of chronic cerebral hypoperfusion with bilateral common carotid artery stenosis (BCAS) induced by placement of microcoils. 15O-gas with isoflurane was supplied to the nose of mouse with evacuation of excess 15O-gas surrounding the body. 15O-PET was performed on days 3, 7, 14, 21, and 28 after surgery. Cerebral blood flow (CBF), cerebral blood volume, oxygen extraction fraction (OEF), and cerebral metabolic rate of oxygen (CMRO2) were calculated in whole brains. A significant decrease in CBF and compensatory increase in OEF in the BCAS group produced CMRO2 values comparable to that of the sham group at three days post-operation. Although CBF and OEF in the BCAS group gradually recovered over the first 28 days, the CMRO2 showed a gradual decrease to 68% of sham values at 28 days post-operation. In conclusion, we successfully developed a noninvasive 15O-PET method for mice.

We aimed to develop a gallium-68 (Ga-68)-labeled single-chain variable fragment (scFv) targeting the human epidermal growth factor receptor 2 (HER2) to rapidly and noninvasively evaluate the status of HER2 expression.Anti-HER2 scFv was labeled with Ga-68 by using deferoxamine (Df) as a bifunctional chelate. Biodistribution of [(68)Ga]Df-anti-HER2 scFv was examined with tumor-bearing mice and positron emission tomography (PET) imaging was performed. The changes in HER2 expression after anti-HER2 therapy were monitored by PET imaging.[(68)Ga]Df-anti-HER2 scFv was obtained with high radiochemical yield after only a 5-min reaction at room temperature. The probe showed high accumulation in HER2-positive xenografts and the intratumoral distribution of radioactivity coincided with HER2-positive regions. Furthermore, [(68)Ga]Df-anti-HER2 scFv helped visualize HER2-positive xenografts and monitor the changes in HER2 expression after anti-HER2 therapy.[(68)Ga]Df-anti-HER2 scFv could be a promising probe to evaluate HER2 status by in vivo PET imaging, unless trastuzumab is prescribed as part of the therapy.

Membrane type-1 matrix metalloproteinase (MT1-MMP) is a protease activating MMP-2 that mediates cleavage of extracellular matrix components and plays pivotal roles in tumor migration, invasion and metastasis. Because in vivo noninvasive imaging of MT1-MMP would be useful for tumor diagnosis, we developed a novel near-infrared (NIR) fluorescence probe that can be activated following interaction with MT1-MMP in vivo. MT1-hIC7L is an activatable fluorescence probe comprised of anti-MT1-MMP monoclonal antibodies conjugated to self-assembling polymer micelles that encapsulate NIR dyes (IC7-1, em: 858nm) at concentrations sufficient to cause fluorescence self-quenching. In aqueous buffer, MT1-hIC7L fluorescence was suppressed to background levels and increased approximately 35.5-fold in the presence of detergent. Cellular uptake experiments revealed that in MT1-MMP positive C6 glioma cells, MT1-hIC7L showed significantly higher fluorescence that increased with time as compared to hIC7L, a negative control probe lacking the anti-MT1-MMP monoclonal antibody. In MT1-MMP negative MCF-7 breast adenocarcinoma cells, both MT1-hIC7L and hIC7L showed no obvious fluorescence. In addition, the fluorescence intensity of C6 cells treated with MT1-hIC7L was suppressed by pre-treatment with an MT1-MMP endocytosis inhibitor (P

Near-infrared (NIR: 800-1000nm) fluorescent probes, which activate their fluorescence following interaction with functional biomolecules, are desirable for noninvasive and sensitive tumor diagnosis due to minimal tissue interference. Focusing on bioavailability and applicability, we developed a probe with a self-assembling polymer micelle, a lactosome, encapsulating various quantities of NIR dye (IC7-1). We also conjugated anti-HER2 single chain antibodies to the lactosome surface and examined the probe's capacity to detect HER2 in cells and in vivo . Micelles encapsulating 20mol% IC7-1 (hIC7L) showed 30-fold higher fluorescence (λ em : 858nm) after micelle denaturation compared to aqueous buffer. Furthermore, antibody modification allowed specific activation of the probe (HER2-hIC7L) following internalization by HER2-positive cells, with the probe concentrating in lysosomes. HER2-hIC7L intravenously administered to mice clearly and specifically visualized HER2-positive tumors by in vivo optical imaging. These results indicate that HER2-hIC7L is a potential activatable NIR probe for sensitive tumor diagnosis. From the Clinical Editor Near-infrared probes that activate their fluorescence following interaction with specific biomolecules are desirable for noninvasive and sensitive tumor detection due to minimal tissue interference. This team of authors developed a probe termed hIC7L and demonstrate its potential in HER2 tumor diagnosis.

Understanding cerebral oxygen metabolism is of great importance in both clinical diagnosis and animal experiments because oxygen is a fundamental source of brain energy and supports brain functional activities. Since small animals such as rats are widely used to study various diseases including cerebral ischemia, cerebrovascular diseases, and neurodegenerative diseases, the development of a noninvasivein vivomeasurement method of cerebral oxygen metabolic parameters such as oxygen extraction fraction (OEF) and cerebral metabolic rate of oxygen (CMRO2) as well as cerebral blood flow (CBF) and cerebral blood volume (CBV) has been a priority. Although positron emission tomography (PET) with15O labeled gas tracers has been recognized as a powerful way to evaluate cerebral oxygen metabolism in humans, this method could not be applied to rats due to technical problems and there were no reports of PET measurement of cerebral oxygen metabolism in rats until an15O-O2injection method was developed a decade ago. Herein, we introduce an intravenous administration method using two types of injectable15O-O2and an15O-O2gas inhalation method through an airway placed in the trachea, which enables oxygen metabolism measurements in rats.

We report a novel series of fluorescent Zn 2+ sensors based on a pyridine–pyridone core structure, which functions as both the chelating part for Zn 2+ and as the fluorophore. Pyridine–pyridone derivatives obtained by replacement of an electron-donating group with an electronic-withdrawing group at the 3-position of the pyridone ring showed almost no background fluorescence because electron transfer to the fluorophore was inhibited. However, these derivatives showed strong fluorescence with Zn 2+ . Coordination with Zn 2+ greatly influenced the electron transfer of the fluorophore, and, as a result, enabled fluorescence ON/OFF switching. In these sensors, 4-[4-(methylsulfanyl)-2-oxo-6-(pyridin-2-yl)-1,2-dihydropyridin-3-yl]benzoic acid ( 5 ) displayed excellent properties: small molecular weight (MW = 338), good water solubility, large Stokes shift (132 nm), and fluorescence ON/OFF switching with Zn 2+ . In addition, fluorescence images of Zn 2+ with 5 in living cells show that the new fluorescent sensor is useful for biological applications.

Since membrane type‐1 matrix metalloproteinase (MT1‐MMP) plays pivotal roles in tumor progression and metastasis and holds great promise as an early biomarker for malignant tumors, a method of evaluating MT1‐MMP expression levels would be valuable for molecular biological and clinical studies. Although we have previously developed a (99m) Tc‐labeled anti‐MT1‐MMP monoclonal IgG ((99m) Tc‐MT1‐mAb) as an MT1‐MMP imaging probe by nuclear medical techniques for this purpose, slow pharmacokinetics were a problem due to its large molecular size. Thus, in this study, our aim was to develop miniaturized antibodies, a single chain antibody fragment (MT1‐scFv) and a dimer of two molecules of scFv (MT1‐diabody), as the basic structures of MT1‐MMP imaging probes followed by in vitro and in vivo evaluation with an (111)In radiolabel. Phage display screening successfully provided MT1‐scFv and MT1‐diabody, which had sufficiently high affinity for MT1‐MMP (K (D) = 29.8 and 17.1 nM). Both (111)In labeled miniaturized antibodies showed higher uptake in MT1‐MMP expressing HT1080 cells than in non‐expressing MCF7 cells. An in vivo biodistribution study showed rapid pharmacokinetics for both probes, which exhibited >20‐fold higher tumor to blood radioactivity ratios (T/B ratio), an index for in vivo imaging, than (99m) Tc‐MT1‐mAb 6 h post‐administration, and significantly higher tumor accumulation in HT1080 than MCF7 cells. SPECT images showed heterogeneous distribution and ex vivo autoradiographic analysis revealed that the radioactivity distribution profiles in tumors corresponded to MT1‐MMP‐positive areas. These findings suggest that the newly developed miniaturized antibodies are promising probes for detection of MT1‐MMP in cancer cells.

Twenty-one hypertensive vasculopathy patients, without AD and major cerebral arterial stenosis and/or occlusion, were enrolled (9 women, 68 ± 7 years). Regions of WML and NAWM were extracted using magnetization-prepared rapid gradient-echo and fluid-attenuated inversion recovery of magnetic resonance images. Volumes of interest (VOIs) were set in the cortex-subcortex, basal ganglia, and centrum semiovale (CS). BPBP

This report describes details of the requirements and practical procedures for quantitative assessments of biological functional parametric images of the brain using 123I-labeled tracers and clinical SPECT systems. With due understanding of the physics and the biological background, this is considered achievable even under clinical environments, provided that data are appropriately acquired, processed, and analyzed. This article discusses how potential hurdles have been overcome for quantitatively assessing quantitative functional parametric images in clinical settings, with successful examples that provided additional clinically useful information.

Membrane type 1 matrix metalloproteinase (MT1-MMP) activates pro-MMP-2 and pro-MMP-13 to their active forms and plays important roles in the destabilization of atherosclerotic plaques. This study sought to determine the usefulness of (99m)Tc-labelled monoclonal antibody (mAb), recognizing MT1-MMP, for imaging atherosclerosis in a rabbit model (WHHLMI rabbits).Anti-MT1-MMP monoclonal IgG(3) and negative control IgG(3) were radiolabelled with (99m)Tc after derivatization with 6-hydrazinonicotinic acid (HYNIC) to yield (99m)Tc-MT1-MMP mAb and (99m)Tc-IgG(3), respectively. WHHLMI and control rabbits were injected with these radio-probes. The aorta was removed and radioactivity was measured at 24 h after the injection. Autoradiography and histological studies were performed.(99m)Tc-MT1-MMP mAb accumulation in WHHLMI rabbit aortas was 5.4-fold higher than that of control rabbits. Regional (99m)Tc-MT1-MMP mAb accumulation was positively correlated with MT1-MMP expression (r = 0.59, p 0.0001), while (99m)Tc-IgG(3) accumulation was independent of MT1-MMP expression (r = 0.03, p = NS). The highest (99m)Tc-MT1-MMP mAb accumulation was found in atheromatous lesions (4.8 ± 1.9, %ID×BW/mm(2) × 10(2)), followed in decreasing order by fibroatheromatous (1.8 ± 1.3), collagen-rich (1.6 ± 1.0) and neointimal lesions (1.5 ± 1.5). In contrast, (99m)Tc-IgG(3) accumulation was almost independent of the histological grade of lesions.Higher (99m)Tc-MT1-MMP mAb accumulation in grade IV atheroma was shown in comparison with neointimal lesions or other more stable lesions. Nuclear imaging with (99m)Tc-MT1-MMP mAb, in combination with CT and MRI, could provide new diagnostic imaging capabilities for detecting vulnerable plaques, although further investigations to improve target to blood ratios are strongly required.

We examined exendin(9-39), an antagonist of glucagon-like peptide-1 (GLP-1) receptor (GLP-1R), as a potential probe for imaging of pancreatic beta-cells. To evaluate in vitro receptor specificity, binding assay was performed using dispersed mouse islet cells. Binding assay showed competitive inhibition of [(125)I]BH-exendin(9-39) binding by non-radioactive exendin(9-39). To assess in vivo selectivity, the biodistribution was evaluated by intravenous administration of [(125)I]BH-exendin(9-39) to mice. Radioactivity of harvested pancreas reached highest levels at 60 and 120min among organs examined except lung. Pre-administration of excess non-radioactive exendin(9-39) remarkably and specifically blocked the radioactivity of pancreas. After [(125)I]BH-exendin(9-39) injection into transgenic mice with pancreatic beta-cells expressing GFP, fluorescent and radioactive signals of sections of pancreas were evaluated with an image analyzer. Imaging analysis showed that the fluorescent GFP signals and the radioactive signals were correspondingly located. Thus, the GLP-1R antagonist exendin(9-39) may serve as a useful probe for pancreatic beta-cell imaging.

Introduction Despite extensive attempts to develop cyclooxygenase (COX)-2 imaging radiotracers, no suitable positron emission tomography (PET)/single photon emission computed tomography (SPECT) tracers are currently available for in vivo imaging of COX-2 expression. The aims of this study were to synthesize and evaluate a radioiodinated derivative of lumiracoxib, 2-[(2-fluoro-6-iodophenyl)-amino]-5-methylphenylacetic acid (FIMA), which is structurally distinct from other drugs in the class and has weakly acidic properties, as a SPECT tracer for imaging COX-2 expression. Methods The COX inhibitory potency was assessed by measuring COX-catalyzed oxidation with hydrogen peroxide. Cell uptake characteristics of 125 I-FIMA were assessed in control and linterfero/interferon-γ-stimulated macrophages. The biodistribution of 125 I-FIMA was determined by the ex vivo tissue counting method in rats. Results The COX-2 inhibitory potency of FIMA (IC 50 =2.46 μM) was higher than that of indomethacin (IC 50 =20.9 μM) and was comparable to lumiracoxib (IC 50 =0.77 μM) and diclofenac (IC 50 =0.98 μM). The IC 50 ratio (COX-1/COX-2=182) indicated FIMA has a high isoform selectivity for COX-2. 125 I-FIMA showed a significantly higher accumulation in COX-2 induced macrophages than in control macrophages, which decreased with nonradioactive FIMA in a concentration dependent manner. The biodistribution study showed rapid clearance of 125 I-FIMA from the blood and most organs including the liver and kidneys. No significant in vivo deiodination was observed with radioiodinated FIMA. Conclusions FIMA showed high inhibitory potency and selectivity for COX-2. Radioiodinated FIMA showed specific accumulation into COX-2 induced macrophages, no significant in vivo deiodination and rapid blood clearance. Radioiodinated FIMA deserves further investigation as a SPECT radiopharmaceutical for imaging COX-2 expression.

Fluorescent analysis has been widely used in biological, chemical and analytical research. A useful fluorescent labeling agent should include NIR emission, a large Stoke's shift, and good labeling ability without interfering with the pharmacological profile of the labeled compound. Thus, we planned to develop an M-AMF-DOTA(Nd) derivative composed of an NIR fluorescent moiety and a maleimide conjugating moiety as a new NIR fluorescent labeling agent which fulfills these requirements. M-AMF-DOTA(Nd) was synthesized from 4-amino-fluorescein and was conjugated with an avidin molecule (Avidin-AMF-DOTA(Nd)) through Lys-side chains by reaction with 2-iminothiolane. The fluorescent features of M-AMF-DOTA(Nd) and Avidin-AMF-DOTA(Nd) were comparatively evaluated. A binding assay of Avidin-AMF-DOTA(Nd) with D-biotin and a tumor cell-uptake study were performed to estimate the effects of conjugation on the biological and physicochemical features of the protein. M-AMF-DOTA(Nd) was obtained in 22% overall yield. M-AMF-DOTA(Nd) had a typical NIR fluorescence from the Nd ion (880 nm and 900 nm from 488 nm excitation). Avidin-AMF-DOTA(Nd) was easily synthesized and also had typical NIR fluorescence from the Nd ion without loss of fluorescent intensity. The binding affinity of Avidin-AMF-DOTA(Nd) to D-biotin was equivalent to naive avidin. Avidin-AMF-DOTA(Nd) was taken up by tumor cells in the same manner as avidin conjugated with fluorescein isothiocyanate, an established, widely used fluorescent avidin. Results from this study indicate that M-AMF-DOTA(Nd) is a potential labeling agent for routine NIR fluorescent analysis.

Membrane type-1 matrix metalloproteinase (MT1-MMP) expressed on the tumor cell surface activates pro-MMP-2 and pro-MMP-13 to exacerbate the malignancy, suggesting its suitability as a target molecule for diagnosis by in vivo molecular imaging. Thus, we prepared radiolabeled anti-MT1-MMP monoclonal antibody (mAb) as a novel radiolabeled probe for detecting MT1-MMP in vivo and evaluated its usefulness in breast tumor-bearing rodents. (99m)Tc-anti-MT1-MMP mAb was prepared using HYNIC as a bifunctional chelating agent and immunoreactivity was evaluated by flow cytometry. MT1-MMP expression in breast carcinoma cells (rat: Walker-256 and MRMT-1, mouse: FM3A) was measured by Western blotting. In vivo biodistribution was examined for 48 h using tumor-implanted rodents followed by estimation of radiation absorbed by a standard quantitation platform Organ Level Internal Dose Assessment (OLINDA). (99m)Tc-anti-MT1-MMP mAb was obtained with 84% immunoreactivity to MT1-MMP and more than 92% radiochemical purity. MT1-MMP was highly expressed in all malignant cells. Tumor radioactivity increased with time after administration and reached 3 to 5 times higher values at 24 h post-injection than those at 1 h. Other organs, including the stomach, showed decreasing values over time. Tumor to blood ratios increased with time and reached more than 1.3 at 48 h. The effective dose was5.0 muSv/MBq. The results suggest that (99m)Tc-anti-MT1-MMP mAb is a promising probe for future diagnosis of breast tumors by in vivo nuclear medical imaging.

The cerebral metabolic rate for oxygen (CMRO(2)) and cerebral oxygen extraction fraction (OEF) are two fundamental parameters used to characterize the pathophysiologic status of cerebral tissues. Although the O-15-labeled gas inhalation method is used to measure these parameters in clinical studies, applying this method to small animals requires many intensive procedures. Thus the development of a new method to measure CMRO(2) and OEF in small animals is of interest. This study aimed to develop a method to assess CMRO(2) and OEF using intravenously injectable oxygen (injectable (15)O-O(2)) and Positron Emission Tomography (PET) for small animals such as rats. Injectable (15)O-O(2) was obtained after (15)O-O(2) gas circulation into an artificial lung. The OEF in normal rats was calculated using the same equation as that used for the bolus inhalation in the (15)O-O(2) gas method. The obtained value of 0.54+/-0.11 of OEF was similar to the value determined from the arterial-venous difference in the oxygen concentration. Furthermore, we evaluated the usefulness of the injectable (15)O-O(2) system in rats occluded in the right middle cerebral artery. A decrease in cerebral blood flow (CBF) and compensatory increase in OEF were observed 1 h after occlusion. In contrast, a marked decrease in CBF and CMRO(2) and a collapse of the compensatory OEF mechanism were found 24 h after occlusion. Thus injectable (15)O-O(2) with PET can be used to estimate oxygen metabolism reliably in stroke animal models, and may be useful for accelerating basic research on cerebral diseases.

Increased (18)F-fluorodeoxyglucose (FDG) uptake in inflammatory lesions, particularly in granulomatous inflammation (e.g., sarcoidosis), makes it difficult to differentiate malignant tumors from benign lesions and is the main source of false-positive FDG-PET findings in oncology. Here, we developed a rat granuloma model and examined FDG uptake in the granuloma. The effects of corticosteroid on FDG uptake in the granuloma were compared with those in a malignant tumor.Rats were inoculated with Mycobacterium bovis bacillus Calmette-Guérin (BCG) or allogenic hepatoma cells, and subdivided into control and pretreated (methylprednisolone acetate, 8 mg/kg i.m.) groups. Radioactivity in tissues was determined 1 h after the FDG injection. FDG-PET was performed in rats bearing BCG granulomas or tumors before and after prednisolone treatment.Mature epithelioid cell granuloma-formation and massive lymphocyte-infiltration were observed in the control group of granuloma, histologically similar to sarcoidosis. The mean FDG uptake in the granuloma was comparable to that in the hepatoma. Prednisolone reduced epithelioid cell granuloma-formation and lymphocyte-infiltration. Prednisolone significantly decreased the level of FDG uptake in the granuloma (52% of control), but not in the hepatoma. The FDG uptake levels in the granulomas and tumors were clearly imaged with PET.We developed an intramuscular granuloma rat model that showed a high FDG uptake comparable to that of the tumor. The effect of prednisolone pretreatment on FDG uptake was greater in the granuloma than in the tumor. These results suggest that BCG-induced granuloma may be a valuable model and may provide a biological basis for FDG studies.

Since the processing activity of the matrix metalloproteinase MT1-MMP regulates various cellular functions such as motility, invasion, growth, differentiation and apoptosis, precise in vivo evaluation of MT1-MMP activity in cancers can provide beneficial information for both basic and clinical studies. For this purpose, we designed a cleavable Positron Emission Tomography (PET)/optical imaging probe consisting of BODIPY650/665 and polyethylene glycol (PEG) conjugated to opposite ends of MT1-MMP substrate peptides. We used in vitro and in vivo fluorescence experiments to select suitable substrate peptide sequences and PEG sizes for the MT1-MMP probes and obtained an optimized structure referred to here as MBP-2k. Radiofluorinated MBP-2k ([(18)F]MBP-2k) was then successfully synthesized via an (18)F-(19)F isotopic exchange reaction in BODIPY650/665. After intravenous injection into mice with xenografted tumors, [(18)F]MBP-2k showed significantly higher accumulation in HT1080 tumors with high MT1-MMP activity than in A549 tumors that have low MT1-MMP activity. Moreover, PET images showed better contrast in HT1080 tumors. These results show that [(18)F]MBP-2k can be used as a hybrid PET/optical imaging agent and is a promising probe for non-invasive monitoring of MT1-MMP activity in cancers. This probe may also efficiently combine targeted tumor imaging with image-guided surgery that could be beneficial for patients in the future.

Photoacoustic imaging (PAI) contributes to tumor diagnosis through the use of PAI probes that effectively accumulate in tumors. Previously, we developed a symmetrical cyanine dye, IC7-1-Bu, which showed high potential as a PAI probe because of its high tumor targeting ability and sufficient in vivo PA signal. However, IC7-1-Bu lacks photostability for multiple laser irradiations, so we developed stabilized PAI probes using IC7-1-Bu as a lead compound. We focused on the effect of singlet oxygen (1O2) generated by excited PAI probes on probe degeneration. We introduced a triplet-state quencher (TSQ) moiety into IC7-1-Bu to quench 1O2 generation and designed three IC-n-T derivatives with different linker lengths (n indicates linker length). The IC-n-T derivatives emitted in vitro PA signals that were comparable to IC7-1-Bu and significantly reduced 1O2 generation while showing improved photostability against multiple irradiations. Of the three derivatives evaluated, IC-5-T accumulated in tumors effectively to allow clear PAI of tumors in vivo. Furthermore, the photostability of IC-5-T was 1.5-fold higher than that of IC7-1-Bu in in vivo sequential PAI. These results suggest that IC-5-T is a potential PAI probe for in vivo sequential tumor imaging.

Since a very complicated technique is necessary to measure cerebral blood flow (CBF) with [14C]iodoantipyrine in small animals, a practical and easy method is needed. In this paper, the differential uptake ratio (DUR) at 5 min after injection of N-isopropyl-p-[125I]iodoamphetamine (IMP) was estimated as an index of CBF in normal rats and compared with the quantitative CBF value measured using [15O]H2O and dynamic PET scan. A good correlation between the two values was obtained. The results indicate that DUR of [125I]IMP at 5 min after injection in rats is a useful and practical indicator of CBF since neither arterial blood sampling nor metabolite correction is necessary.

In the basic research on cerebral perfusion disorders, a new method for measurement of oxygen extraction fraction (OEF) and cerebral metabolic rate for oxygen (CMRO2) has been desired. Although the O-15-labeled gas inhalation method is performed in clinical studies, application of the inhalation method to small animals requires too many intensive procedures. Therefore, this study investigated a new method of assessing OEF in small animals using intravenously injectable oxygen (injectable 15O-O2). Additionally, it was compared with the inhalation method, using a monkey for further validation. Using injectable 15O-O2, 72 MBq/ml of radioactivity was obtained after 15O-O2 gas circulation into an artificial lung. OEF with injectable 15O-O2 was calculated using the same equation as that applied to the bolus inhalation method. The OEF value obtained by injectable 15O-O2 was well in accordance with that evaluated by the arterial-venous difference of oxygen concentration. Furthermore, the OEF and CMRO2 images obtained with two methods using a monkey brain showed a similar distribution. These results indicate that this method is useful for the estimation of OEF and CMRO2 in small animals using an animal positron emission tomography system and may accelerate the basic research of cerebral perfusion diseases.