title: Determination of plasma protein binding of positron emission tomography radioligands by high-performance frontal analysis.
abstract: Positron emission tomography (PET) is an imaging technique based on the use of radioligands labeled with short lived radionuclides, such as (11)C (t½=20.4min) and (18)F (t½=109.8min), which as a consequence often requires rapid plasma protein binding analysis methods. In addition, PET radioligands can suffer from non-specific binding to the membrane when ultrafiltraion, which is the most commonly used method for measuring protein binding in PET, is employed. In this study a high-performance frontal analysis (HPFA) method based on incorporation of a gel filtration column (discovery(®) BIO GFC 100, 50mm×4.6mm, 5μm, 100Å) into a radio-LC system with phosphate buffered saline (PBS, pH 7.4) at a flow rate of 3ml/min as mobile phase was developed and investigated for four PET radioligands. The minimum injection volume (MIV) of plasma, which is a crucial factor in HPFA, was determined to be 200μl (human), 500μl (monkey), 700μl (human) and 1000μl (monkey) for these four radioligands. The MIV values increased as a higher fraction of the radioligand was present in the protein-free form. The protein binding results obtained were in good agreement with ultrafiltration and the method did not suffer from non-specific binding. The short analysis time (<12min) allowed multiple protein binding measurements during time course of a human [(11)C]PBR28 PET study.
authors.affiliation: Karolinska Institutet, Department of Clinical Neuroscience, Center for Psychiatric Research, Stockholm, Sweden. Electronic address: nahid.amini@ki.se.
authors.forename: Nahid
authors.initials: N
authors.lastname: Amini
authors.affiliation: Karolinska Institutet, Department of Clinical Neuroscience, Center for Psychiatric Research, Stockholm, Sweden.
authors.forename: Ryuji
authors.initials: R
authors.lastname: Nakao
authors.affiliation: Karolinska Institutet, Department of Clinical Neuroscience, Center for Psychiatric Research, Stockholm, Sweden; PET Centre of Excellence, AstraZeneca Translational Science Center at Karolinska Institutet, Department of Clinical Neuroscience, Karolinska Institutet, Stockholm, Sweden.
authors.forename: Magnus
authors.initials: M
authors.lastname: Schou
authors.affiliation: Karolinska Institutet, Department of Clinical Neuroscience, Center for Psychiatric Research, Stockholm, Sweden.
authors.forename: Christer
authors.initials: C
authors.lastname: Halldin
mesh_terms: D000818:Animals; D001798:Blood Proteins / Q000737:chemistry*; D000882:Haplorhini; D006801:Humans; D010949:Plasma / Q000737:chemistry*; D049268:Positron-Emission Tomography / Q000379:methods; D011868:Radioisotopes / Q000737:chemistry*; D019275:Radiopharmaceuticals / Q000737:chemistry*; D014462:Ultrafiltration
chemical_list: D001798:Blood Proteins; D011868:Radioisotopes; D019275:Radiopharmaceuticals
keywords: High-performance frontal analysis (HPFA); Minimum injection volume (MIV); Plasma protein binding; Positron emission tomography (PET); Radioligand