ABSTRACT
In this study, linear poly(ethylene glycol) (PEG) and novel linear-hyperbranched, amphiphilic polyglycerol (hbPG) polymers with cholesterol (Ch) as a lipid anchor moiety were radiolabeled with fluorine-18 via copper-catalyzed click chemistry. In vivo investigations via positron emission tomography (PET) and ex vivo biodistribution in mice were conducted. A systematic comparison to the liposomal formulations with and without the polymers with respect to their initial pharmacokinetic properties during the first hour was carried out, revealing remarkable differences. Additionally, cholesterol was directly labeled with fluorine-18 and examined likewise. Both polymers, Ch-PEG27-CH2-triazole-TEG-(18)F and Ch-PEG30-hbPG24-CH2-triazole-TEG-(18)F (TEG: triethylene glycol), showed rapid renal excretion, whereas the (18)F-cholesten displayed retention in lung, liver, and spleen. Liposomes containing Ch-PEG27-CH2-triazole-TEG-(18)F revealed a hydrodynamic radius of 46 nm, liposomal Ch-PEG30-hbPG24-CH2-triazole-TEG-(18)F showed a radius of 84 nm and conventional liposomes with (18)F-cholesten 204 nm, respectively. The results revealed fast uptake of the conventional liposomes by liver, spleen, and lung. Most importantly, the novel hbPG-polymer stabilized liposomes showed similar behavior to the PEG-shielded vesicles. Thus, an advantage of multifunctionality is achieved with retained pharmacokinetic properties. The approach expands the scope of polymer tracking in vivo and liposome tracing in mice via PET.
Subject(s)
Ethers/chemistry , Liposomes/chemistry , Polymers/chemistry , Radiopharmaceuticals/chemistry , Animals , Cholesterol/chemistry , Ethers/pharmacokinetics , Fluorine Radioisotopes , Isotope Labeling , Male , Mice, Inbred C57BL , Micelles , Polymers/pharmacokinetics , Positron-Emission Tomography , Radiopharmaceuticals/pharmacokinetics , Tissue DistributionABSTRACT
Metergoline, a serotonin receptor antagonist, was labeled with carbon-11 in order to evaluate its pharmacokinetics and distribution in non-human primates using positron emission tomography. [(11)C]Metergoline had moderate brain uptake and exhibited heterogeneous specific binding, which was blocked by pretreatment with metergoline and altanserin throughout the cortex. Non-specific binding and insensitivity to changes in synaptic serotonin limit its potential as a PET radiotracer. However, the characterization of [(11)C]metergoline pharmacokinetics and binding in the brain and peripheral organs using PET improves our understanding of metergoline drug pharmacology.
Subject(s)
Metergoline/chemistry , Positron-Emission Tomography , Radiopharmaceuticals/chemistry , Receptors, Serotonin/chemistry , Animals , Brain/metabolism , Carbon Radioisotopes/chemistry , Metergoline/chemical synthesis , Metergoline/pharmacokinetics , Primates , Protein Binding , Radiopharmaceuticals/pharmacokinetics , Receptors, Serotonin/metabolism , Tissue DistributionABSTRACT
Why beat about the bush? An operationally simple and mild reaction based on the direct fixation of (11)CO(2) with 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) has been developed for the synthesis of (11)C-labeled carbamates at 75 degrees C within 10 minutes in radiochemical yields above 70% (see scheme). This strategy should be immediately useful for the construction of new radiotracers for positron emission tomography and other applications.
