Novel Amphiphilic Probes for [¹⁸F]-Radiolabeling Preformed Liposomes and Determination of Liposomal Trafficking by Positron Emission Tomography

Abstract

Positron-emission tomography (PET) is a noninvasive real-time functional imaging system and is expected to be useful for the development of new drug candidates in clinical trials. For its application with preformulated liposomes, we devised an optimized [18F]-compound and developed a direct liposome modification method that we termed the "solid-phase transition method". We were successful in using 1-[18F]fluoro-3,6-dioxatetracosane ([18F]7a) for in vivo trafficking of liposomes. This method might be a useful tool in preclinical and clinical studies of lipidic particle-related drugs.

Liposome-Encapsulated Hemoglobin Ameliorates Ischemic Stroke in Nonhuman Primates: An Acute Study

“…Therefore, nanometer-sized LEH, but not RBCs, may flow with plasma through capillaries, patent even in the core of ischemia (Theilen et al, 1994), to facilitate the O 2 supply by reducing the O 2 diffusion distance. We recently labeled LEH with an 18 F probe (Urakami et al, 2007) and found a concentric accumulation of radioactivity from the surrounding cortex toward the basal ganglia in a rodent MCAO model (Urakami et al, 2009) using a small animal PET system (Clairvivo; Shimadzu, Kyoto, Japan). Thus, it is plausible that LEH may perfuse with plasma, supplying O 2 to the cortex during ischemia to prevent ischemic penumbra from undergoing irreversible processes and thereby suppressing subsequent reperfusion injury.…”

Thermoactivatable polymer-grafted liposomes for low-invasive image-guided chemotherapy

“…The 3D imaging of certain in vivo traceable liposomes has been performed, using predominantly magnetic resonance imaging (MRI) (iron oxide nanoparticles, 15,16 gadolinium chelates, 17 and manganese [Mn] 18 ) but also nuclear imaging (positron emission tomography and single photon emission computed tomography). 19,20 MRI is widely used in the clinical field and offers many advantages, such as high spatial resolution 3D imaging, no exposure to ionized radiation, and detection with functional and physiological mapping. Thermosensitive liposomes loaded with water-soluble contrast agents (gadolinium chelates 21 or Mn 218, 22,23 ) have been reported for monitoring liposome accumulation or drug-release processes.…”

Multi-functional liposomes having temperature-triggered release and magnetic resonance imaging for tumor-specific chemotherapy

“…Recently, efforts have been made to provide imaging functions to various types of carriers by incorporating various types of imaging probes, such as quantum dots [15][16][17], 5 magnetic iron oxide nanoparticles [11,12,18,] and radionuclide 18 F [19,20] have been incorporated to drug carrier materials for fluorescence imaging, magnetic resonance imaging (MRI), and positron emission tomography (PET) imaging, respectively. Among them, MRI is advantageous from the view points of image of high resolution and no exposure to radiation.…”