Improved Radiolytic Stability of a 68Ga-labelled Collagelin Analogue for the Imaging of Fibrosis

There is an unmet medical need for non-invasive, sensitive, and quantitative methods for the assessment of fibrosis. Herein, an improved collagelin analogue labelled with gallium-68 for use with positron emission tomography (PET) is presented. A cyclic peptide, c[CPGRVNleHGLHLGDDEGPC], was synthesized by solid-phase peptide synthesis, conjugated to 2-(4,7-bis(2-(tert-butoxy)-2-oxoethyl)-1,4,7-triazonan-1-yl)acetic acid, and labelled with gallium-68. High performance liquid chromatography (HPLC) was used for the quality and stability assessment of the collagelin analogue. Non-specific organ distribution, blood clearance, and excretion rates were investigated in healthy mice and rats using ex vivo organ distribution analysis and dynamic in vivo PET/CT. Mice with carbon tetrachloride (CCl4) induced liver fibrosis were used for the investigation of specific binding via in vitro frozen section autoradiography, ex vivo organ distribution, and in vivo PET/CT. A non-decay corrected radiochemical yield (48 ± 6%) of [68Ga]Ga-NOTA-PEG2-c[CPGRVNleHGLHLGDDEGPC] ([68Ga]Ga-NO2A-[Nle13]-Col) with a radiochemical purity of 98 ± 2% was achieved without radical scavengers. The 68Ga-labelling was regioselective and stable at ambient temperature for at least 3 h. The autoradiography of the cryosections of fibrotic mouse liver tissue demonstrated a distinct heterogeneous radioactivity uptake that correlated with the fibrosis scores estimated after Sirius Red staining. The blood clearance and tissue washout from the [68Ga]Ga-NO2A-[Nle13]-Col was fast in both normal and diseased mice. Dosimetry investigation in rats indicated the possibility for 4–5 PET/CT examinations per year. Radiolytic stability of the collagelin analogue was achieved by the substitution of methionine with norleucine amino acid residue without a deterioration of its binding capability. [68Ga]Ga-NO2A-[Nle13]-Col demonstrated a safe dosimetry profile suitable for repeated scanning.

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Improved Detection of Molecular Markers of Atherosclerotic Plaques Using Sub-Millimeter PET Imaging

Molecules ◽

10.3390/molecules25081838 ◽

2020 ◽

Vol 25 (8) ◽

pp. 1838 ◽

Cited By ~ 1

Author(s):

Jessica Bridoux ◽

Sara Neyt ◽

Pieterjan Debie ◽

Benedicte Descamps ◽

Nick Devoogdt ◽

...

Keyword(s):

Pet Imaging ◽

Ex Vivo ◽

High Sensitivity ◽

Radiochemical Yield ◽

Control Group ◽

Complexing Agent ◽

Atherosclerotic Plaques ◽

Atherosclerotic Lesions ◽

Pet Ct

Since atherosclerotic plaques are small and sparse, their non-invasive detection via PET imaging requires both highly specific radiotracers as well as imaging systems with high sensitivity and resolution. This study aimed to assess the targeting and biodistribution of a novel fluorine-18 anti-VCAM-1 Nanobody (Nb), and to investigate whether sub-millimetre resolution PET imaging could improve detectability of plaques in mice. The anti-VCAM-1 Nb functionalised with the novel restrained complexing agent (RESCA) chelator was labelled with [18F]AlF with a high radiochemical yield (>75%) and radiochemical purity (>99%). Subsequently, [18F]AlF(RESCA)-cAbVCAM1-5 was injected in ApoE−/− mice, or co-injected with excess of unlabelled Nb (control group). Mice were imaged sequentially using a cross-over design on two different commercially available PET/CT systems and finally sacrificed for ex vivo analysis. Both the PET/CT images and ex vivo data showed specific uptake of [18F]AlF(RESCA)-cAbVCAM1-5 in atherosclerotic lesions. Non-specific bone uptake was also noticeable, most probably due to in vivo defluorination. Image analysis yielded higher target-to-heart and target-to-brain ratios with the β-CUBE (MOLECUBES) PET scanner, demonstrating that preclinical detection of atherosclerotic lesions could be improved using the latest PET technology.

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Monitoring the Early Response of Fulvestrant Plus Tanshinone IIA Combination Therapy to Estrogen Receptor-Positive Breast Cancer by Longitudinal 18F-FES PET/CT

Contrast Media & Molecular Imaging ◽

10.1155/2019/2374565 ◽

2019 ◽

Vol 2019 ◽

pp. 1-8 ◽

Cited By ~ 1

Author(s):

SiMin He ◽

MingWei Wang ◽

YongPing Zhang ◽

JianMin Luo ◽

YingJian Zhang

Keyword(s):

Combination Therapy ◽

Ex Vivo ◽

Early Response ◽

Ct Imaging ◽

Tanshinone Iia ◽

Breast Cancers ◽

Antitumor Effects ◽

Pet Ct ◽

Er Positive

Endocrine monotherapy of breast cancers is generally hampered by the primary/acquired resistance and adverse sides in clinical settings. Herein, advantaging the multitargeting antitumor effects and normal organ-protecting roles of Chinese herbal medicine, the aim of this study was to investigate the enhanced synergistic efficacy of fulvestrant plus Tan IIA combination therapy in ER-positive breast cancers and to monitor the early response by longitudinal 18F-FES PET/CT imaging. The experimental results showed FUL + Tan IIA combination therapy significantly inhibited tumor growth of ER-positive ZR-75-1 tumor xenografts and exhibited distinct antitumor effects at an earlier time point after treatment than did the monotherapy of FUL or Tan IIA. Moreover, 18F-FES PET/CT imaging competently monitored the early response of FUL + Tan IIA combination therapy. The quantitative 18F-FES %ID/gmax in vivo was further confirmed by and correlated well with ERα expression ex vivo. In conclusion, the synergic effect of FUL + Tan IIA combination therapy to ER-positive breast cancers was verified in the preclinical tumor models and the early treatment response could be monitored by 18F-FES PET/CT.

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DNA Damage in Blood Leukocytes of Prostate Cancer Patients Undergoing PET/CT Examinations with [68Ga]Ga-PSMA I&T

Cancers ◽

10.3390/cancers12020388 ◽

2020 ◽

Vol 12 (2) ◽

pp. 388 ◽

Cited By ~ 1

Author(s):

Sarah Schumann ◽

Harry Scherthan ◽

Torsten Frank ◽

Constantin Lapa ◽

Jessica Müller ◽

...

Keyword(s):

Contrast Agent ◽

Ex Vivo ◽

Absorbed Dose ◽

Dna Double Strand Breaks ◽

Blood Leukocytes ◽

Blood Samples ◽

Time Points ◽

Pet Ct ◽

Radiation Induced

The aim was to investigate the induction and repair of radiation-induced DNA double-strand breaks (DSBs) as a function of the absorbed dose to the blood of patients undergoing PET/CT examinations with [68Ga]Ga-PSMA. Blood samples were collected from 15 patients before and at four time points after [68Ga]Ga-PSMA administration, both before and after the PET/CT scan. Absorbed doses to the blood were calculated. In addition, blood samples with/without contrast agent from five volunteers were irradiated ex vivo by CT while measuring the absorbed dose. Leukocytes were isolated, fixed, and stained for co-localizing γ-H2AX+53BP1 DSB foci that were enumerated manually. In vivo, a significant increase in γ-H2AX+53BP1 foci compared to baseline was observed at all time points after administration, although the absorbed dose to the blood by 68Ga was below 4 mGy. Ex vivo, the increase in radiation-induced foci depended on the absorbed dose and the presence of contrast agent, which could have caused a dose enhancement. The CT-dose contribution for the patients was estimated at about 12 mGy using the ex vivo calibration. The additional number of DSB foci induced by CT, however, was comparable to the one induced by 68Ga. The significantly increased foci numbers after [68Ga]Ga-PSMA administration may suggest a possible low-dose hypersensitivity.

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SURG-07. Plasmonic gold nanostars to increase the efficiency and specificity of laser interstitial thermal therapy (LITT) in the treatment of brain tumors

Neuro-Oncology Advances ◽

10.1093/noajnl/vdab071.100 ◽

2021 ◽

Vol 3 (Supplement_3) ◽

pp. iii24-iii25

Author(s):

Ethan Srinivasan ◽

Pakawat Chongsathidkiet ◽

Ren Odion ◽

Yang Liu ◽

Eric Sankey ◽

...

Keyword(s):

Ex Vivo ◽

Thermal Therapy ◽

Surrounding Tissue ◽

Intracranial Tumors ◽

Invasive Treatment ◽

Laser Interstitial Thermal Therapy ◽

Gold Nanostars ◽

Pet Ct ◽

The Impact

Abstract Introduction Laser interstitial thermal therapy (LITT) is an effective minimally-invasive treatment option for intracranial tumors. Our group produced plasmonics-active gold nanostars (GNS) designed to preferentially accumulate within intracranial tumors and amplify the ablative capacity of LITT while better conforming to tumor boundaries and protecting surrounding tissue. Materials and Methods: The 12nm GNS were synthesized using reduced HAuCl4 with Na3C6H5O7 seeds, mixed with AgNO3, C6H8O6, and HAuCL4, and coated with polyethylene glycol then functionalized with methoxy PEG thiol. CT-2A glioma cells were intracranially implanted into mice, followed 18 days later by IV injection of GNS. PET-CT was performed at 10-minutes, 24-, and 72-hours post-GNS administration, with autoradiography (AR) and histopathology (HP) on sacrifice after the last scan. To test the impact of GNS on LITT coverage capacity in appropriately sized ex vivo models, we utilized agarose gel-based phantoms incorporating control and GNS-infused central “tumors” in multiple shapes. LITT was administered with the NeuroBlate System. Results In vivo, GNS preferentially accumulated within intracranial tumors on PET-CT at the 24- and 72-hour timepoints. AR and HP confirmed high GNS accumulation within tumor. Ex vivo, in cuboid tumor phantoms, the GNS-infused phantom heated 5.5x faster than the control, rising 0.49°C per minute compared to 0.09°C. In a split-cylinder tumor phantom with half containing GNS, the GNS-infused border heated 2x faster and the surrounding area was exposed to 30% lower temperatures. In a GNS-infused star-shaped phantom, the heat spread contoured along phantom boundaries. Conclusion Our results provide evidence for use of GNS to improve the specificity, efficiency, and potentially safety of LITT. The in vivo data support selective accumulation within intracranial tumors, and the GNS-infused phantom experiments demonstrate increased rates of heating within the tumor model, heat contouring to tumor borders, and decreased heating of surrounding regions representing normal structures.

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A Semi Rigid Novel Hydroxamate AMPED-Based Ligand for 89Zr PET Imaging

Molecules ◽

10.3390/molecules26195819 ◽

2021 ◽

Vol 26 (19) ◽

pp. 5819

Author(s):

Lisa Russelli ◽

Francesco De Rose ◽

Loredana Leone ◽

Sybille Reder ◽

Markus Schwaiger ◽

...

Keyword(s):

Pet Imaging ◽

Ex Vivo ◽

Small Animal ◽

Biologically Active ◽

Small Animal Pet ◽

Organ Distribution ◽

Complexing Agent ◽

Distribution Studies

In this work, we designed, developed, characterized, and investigated a new chelator and its bifunctional derivative for 89Zr labeling and PET-imaging. In a preliminary study, we synthesized two hexadentate chelators named AAZTHAS and AAZTHAG, based on the seven-membered heterocycle AMPED (6-amino-6-methylperhydro-1,4-diazepine) with the aim to increase the rigidity of the 89Zr complex by using N-methyl-N-(hydroxy)succinamide or N-methyl-N-(hydroxy)glutaramide pendant arms attached to the cyclic structure. N-methylhydroxamate groups are the donor groups chosen to efficiently coordinate 89Zr. After in vitro stability tests, we selected the chelator with longer arms, AAZTHAG, as the best complexing agent for 89Zr presenting a stability of 86.4 ± 5.5% in human serum (HS) for at least 72 h. Small animal PET/CT static scans acquired at different time points (up to 24 h) and ex vivo organ distribution studies were then carried out in healthy nude mice (n = 3) to investigate the stability and biodistribution in vivo of this new 89Zr-based complex. High stability in vivo, with low accumulation of free 89Zr in bones and kidneys, was measured. Furthermore, an activated ester functionalized version of AAZTHAG was synthesized to allow the conjugation with biomolecules such as antibodies. The bifunctional chelator was then conjugated to the human anti-HER2 monoclonal antibody Trastuzumab (Tz) as a proof of principle test of conjugation to biologically active molecules. The final 89Zr labeled compound was characterized via radio-HPLC and SDS-PAGE followed by autoradiography, and its stability in different solutions was assessed for at least 4 days.

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The Influence of Substituents in 99mTc-Benzylidenediphosphonate Complexes on their Organ Distribution in Rats

Nuklearmedizin ◽

10.1055/s-0038-1624204 ◽

1984 ◽

Vol 23 (03) ◽

pp. 119-122

Author(s):

P. Kristen ◽

A. Garnier-Moiroux ◽

K. Winkel ◽

M. Eisenhut

Keyword(s):

Binding Sites ◽

Tumor Tissue ◽

Bone Lesion ◽

Organ Distribution ◽

Blood Clearance ◽

Bone Uptake ◽

Femur Diaphysis ◽

Influence Of Substituents

SummaryThe biodistribution of a series of new 99mTc-benzylidenediphosphonate complexes (99mTc-BDP) in rats was found to vary considerably with substituents in the alpha (X) and para (R) position of the BDP ligands. From the in vivo behaviour of the 99mTc-BDP complexes the following conclusions could be drawn: 1. the blood clearance was accelerated by X = NH2; 2. the kidney uptake was decreased by X = OH; 3. the bone uptake was enhanced by X = OH and R = OH; and 4. R = C1 retarded the blood clearance, increased the kidney and lowered the bone uptake. A subcutaneously transplantable osteosarcoma was tested with 99mTc-BDP complexes as a bone lesion model. Although rapidly growing the osteosarcoma accumulated less activity than the femur diaphysis. The small amount of binding sites in the tumor tissue for osteotropic radiopharmaceuticals was attributed to the formation of necroses.

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Amyloid-Targeting PET Tracer [18F]Flutemetamol Accumulates in Atherosclerotic Plaques

Molecules ◽

10.3390/molecules24061072 ◽

2019 ◽

Vol 24 (6) ◽

pp. 1072 ◽

Cited By ~ 2

Author(s):

Sanna Hellberg ◽

Johanna Silvola ◽

Heidi Liljenbäck ◽

Max Kiugel ◽

Olli Eskola ◽

...

Keyword(s):

Ex Vivo ◽

Mouse Strains ◽

Aortic Tissue ◽

Atherosclerotic Plaques ◽

Carotid Artery Plaque ◽

Pet Tracer ◽

Pet Ct ◽

Human Carotid

Atherosclerosis is characterized by the accumulation of oxidized lipids in the artery wall, which triggers an inflammatory response. Oxidized low-density lipoprotein (ox-LDL) presents amyloid-like structural properties, and different amyloid species have recently been recognized in atherosclerotic plaques. Therefore, we studied the uptake of the amyloid imaging agent [18F]Flutemetamol in atherosclerotic plaques. The binding of [18F]Flutemetamol to human carotid artery plaque was studied in vitro. In vivo uptake of the tracer was studied in hypercholesterolemic IGF-II/LDLR−/−ApoB100/100 mice and C57BL/6N controls. Tracer biodistribution was studied in vivo with PET/CT, and ex vivo by gamma counter and digital ex vivo autoradiography. The presence of amyloid, ox-LDL, and macrophages in the plaques was examined by immunohistochemistry. [18F]Flutemetamol showed specific accumulation in human carotid plaque, especially in areas positive for amyloid beta. The aortas of IGF-II/LDLR−/−ApoB100/100 mice showed large thioflavin-S-positive atherosclerotic plaques containing ox-LDL and macrophages. Autoradiography revealed 1.7-fold higher uptake in the plaques than in a lesion-free vessel wall, but no difference in aortic tissue uptake between mouse strains were observed in the in vivo PET/CT. In conclusion, [18F]Flutemetamol binds to amyloid-positive areas in human atherosclerotic plaques. Further studies are warranted to clarify the uptake mechanisms, and the potential of the tracer for in vivo imaging of atherosclerosis in patients.

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Abstract 15108: Imaging Coronary Atherosclerosis Using [18F]FDG PET-CT: Validation Study in Pigs

Circulation ◽

10.1161/circ.130.suppl_2.15108 ◽

2014 ◽

Vol 130 (suppl_2) ◽

Author(s):

Miikka Tarkia ◽

Antti Saraste ◽

Christoffer Stark ◽

Tommi Vähäsilta ◽

Timo Savunen ◽

...

Keyword(s):

Coronary Arteries ◽

Coronary Atherosclerosis ◽

Vessel Wall ◽

Ex Vivo ◽

Intimal Thickening ◽

Fdg Uptake ◽

Atherosclerotic Lesions ◽

Pet Ct ◽

18F Fdg

Introduction: Positron emission tomography (PET) with 18F-fluorodeoxyglucose ([18F]FDG) can be used to detect atherosclerotic plaque inflammation. The degree of [18F]FDG uptake in different stages of coronary atherosclerosis remains largely unknown. Thus, we studied the amount of [18F]FDG uptake and feasibility of its in vivo quantification by combination of PET and computed tomography angiography (CTA) in a pig model of atherosclerosis. Methods: In order to induce coronary atherosclerosis, diabetes was caused by streptozotocin injections in farm pigs (n=10). After 6 months on high-fat diet, pigs underwent dual gated cardiac PET and CTA to measure [18F]FDG uptake in the proximal segments of coronary arteries as maximal target to background ratio (TBR = [18F]FDG uptake normalized to blood pool). Proximal coronary segments (n=33) were harvested for ex vivo measurement of radioactivity and for histology and measurement of tracer uptake into the vessel wall by autoradiography (ARG). Results: The pigs were hyperglycemic (12.3±4.7 mmol/L) and hypercholesterolemic (12.7±5.1 mmol/L) at the end of the study. The coronary arteries showed intimal thickening (n=16 segments) and atheroma (n=10 segments). Compared with the normal vessel wall, ARG showed 1.7±0.7 times higher accumulation of [18F]FDG in intimal thickening and 4.1±2.3 in atheroma (p=0.004 and p=0.003, respectively). Ex vivo mean vessel to blood ratio of segments with atheroma was higher than non-atherosclerotic segments (2.6±1.2 vs. 1.3±0.7, p=0.04). In vivo PET imaging showed the highest TBR of 2.7. However, maximal TBR was not significantly different in segments without atherosclerosis (1.1±0.5) and either intimal thickening (1.2±0.4, p=1.0) or atheroma (1.6±0.6, p=0.4) and no correlation was seen between the segmental TBR measured by in vivo PET-CT and [18F]FDG uptake measured by either biodistribution or autoradiography. Conclusions: We found increased [18F]FDG uptake in atherosclerotic lesions. However, quantification of [18F]FDG uptake in these relatively small and early stage atherosclerotic lesions by dual gated PET and CTA was not feasible. Further studies are needed to clarify feasibility of this approach in more advanced and highly inflamed atherosclerotic coronary plaques.

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68Ga-NeoB: Präklinische Ergebnisse zur Bildgebung gastrointestinaler Stromatumoren und zur Bestimmung der Zielrezeptordichte im Gastrointestinaltrakt

Der Nuklearmediziner ◽

10.1055/a-1375-9605 ◽

2021 ◽

Vol 44 (02) ◽

pp. 102-112

Author(s):

Marc Pretze ◽

Carmen Wängler ◽

Stefan O. Schönberg ◽

Björn Wängler

Keyword(s):

Ex Vivo ◽

Gastrointestinale Stromatumoren ◽

Pet Ct ◽

Grpr Antagonist

Zusammenfassung 68Ga-NeoB (früher bekannt als NeoBOMB1) ist ein neuartiger DOTA-gekoppelter Gastrin-Releasing-Peptid-Rezeptor(GRPR)-Antagonist mit hoher Bindungsaffinität zum GRPR und ausgezeichneter In-vivo-Stabilität. Ziel dieser präklinischen Studie war es, die Verwendung von 68Ga-NeoB zur Bestimmung der GRPR-Expression im Pankreasgewebe weiter zu erforschen, indem der GRPR-Sättigungsgrad im Pankreas bei der Verwendung verschiedener molarer Stoffmengen von 68Ga-NeoB geschätzt wurde. Darüber hinaus wurde 68Ga-NeoB als Tracer für gastrointestinale Stromatumoren (GIST) in 2 verschiedenen Mausstämmen untersucht. Anschließende Ex-vivo-Biodistributionsstudien mit verschiedenen Stoffmengen des antagonistischen Tracers 68Ga-NeoB mit hoher Bindungsaffinität zu GRPR wurden zur Abschätzung der Rezeptordichte in Organen oder Geweben mit hoher Expression dieses Rezeptors genutzt. Die Kombination von PET/CT und MRT-Datensätzen unterstützte die Ermittlung von Organanreicherungen auch bei Erreichen des Sättigungsgrades des Radiotracers in gastrointestinalen Organen.

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EXTH-19. INTEGRATION OF PLASMONIC GOLD NANOSTARS AND LASER INTERSTITIAL THERMAL THERAPY (LITT) FOR SPECIFIC AND AMPLIFIED ABLATION OF BRAIN TUMORS

Neuro-Oncology ◽

10.1093/neuonc/noab196.658 ◽

2021 ◽

Vol 23 (Supplement_6) ◽

pp. vi167-vi167

Author(s):

Ethan Srinivasan ◽

Pakawat Chongsathidkiet ◽

Ren Odion ◽

Yang Liu ◽

Eric Sankey ◽

...

Keyword(s):

Ex Vivo ◽

Thermal Therapy ◽

Surrounding Tissue ◽

Intracranial Tumors ◽

Invasive Treatment ◽

Laser Interstitial Thermal Therapy ◽

Gold Nanostars ◽

Pet Ct ◽

The Impact

Abstract INTRODUCTION Laser interstitial thermal therapy (LITT) is an effective minimally-invasive treatment option for intracranial tumors. Our group produced plasmonics-active gold nanostars (GNS) designed to preferentially accumulate within intracranial tumors and amplify the ablative capacity of LITT while better conforming to tumor boundaries and protecting surrounding tissue. MATERIALS AND METHODS The 12nm GNS were synthesized using reduced HAuCl4 with Na3C6H5O7 seeds, mixed with AgNO3, C6H8O6, and HAuCL4, and coated with polyethylene glycol then functionalized with methoxy PEG thiol. CT-2A glioma cells were intracranially implanted into mice, followed 18 days later by IV injection of GNS. PET-CT was performed at 10-minutes, 24-, and 72-hours post-GNS administration, with autoradiography (AR) and histopathology (HP) on sacrifice after the last scan. To test the impact of GNS on LITT coverage capacity in appropriately sized ex vivo models, we utilized agarose gel-based phantoms incorporating control and GNS-infused central “tumors” in multiple shapes. LITT was administered with the NeuroBlate System. RESULTS In vivo, GNS preferentially accumulated within intracranial tumors on PET-CT at the 24- and 72-hour timepoints. AR and HP confirmed high GNS accumulation within tumor. Ex vivo, in cuboid tumor phantoms, the GNS-infused phantom heated 5.5x faster than the control, rising 0.49°C per minute compared to 0.09°C. In a split-cylinder tumor phantom with half containing GNS, the GNS-infused border heated 2x faster and the surrounding area was exposed to 30% lower temperatures. In a GNS-infused star-shaped phantom, the heat spread contoured along phantom boundaries. CONCLUSIONS Our results provide evidence for use of GNS to improve the specificity, efficiency, and potentially safety of LITT. The in vivo data support selective accumulation within intracranial tumors, and the GNS-infused phantom experiments demonstrate increased rates of heating within the tumor model, heat contouring to tumor borders, and decreased heating of surrounding regions representing normal structures.

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