Development of new albumin-binding radiotracers for PET imaging of cerebrospinal fluid flow in the glymphatic system
Abstract Background The glymphatic system is a recently discovered brain-wide clearance system that allows the cerebrospinal fluid (CSF) flow to clear metabolic waste, but the tools for the quantitative and non-invasive investigation of its function and activity especially in humans is lacking, hind...
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2025-07-01
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| Series: | EJNMMI Radiopharmacy and Chemistry |
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| Online Access: | https://doi.org/10.1186/s41181-025-00365-4 |
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| author | Martta Peltoniemi Surachet Imlimthan Sonja C. Jalonen Niklas Daniel Åke Persson Terhi J. Lohela Tuomas O. Lilius Mirkka Sarparanta |
| author_facet | Martta Peltoniemi Surachet Imlimthan Sonja C. Jalonen Niklas Daniel Åke Persson Terhi J. Lohela Tuomas O. Lilius Mirkka Sarparanta |
| author_sort | Martta Peltoniemi |
| collection | DOAJ |
| description | Abstract Background The glymphatic system is a recently discovered brain-wide clearance system that allows the cerebrospinal fluid (CSF) flow to clear metabolic waste, but the tools for the quantitative and non-invasive investigation of its function and activity especially in humans is lacking, hindering studies on glymphatic system physiology and therapeutic potential of glymphatic drug delivery and modulation. We postulated that albumin-binding radiotracers could be used to this end by binding to the endogenous protein in CSF, constituting a macromolecular, biological radiotracer, allowing for the visualization of CSF flow in the central nervous system non-invasively with positron emission tomography (PET). Results We prepared three albumin-binding tracers based on 4-(p-iodophenyl)butyric acid and truncated Evans Blue radiolabeled with gallium-68 using the NODAGA chelator for in vivo radiolabeling of CSF albumin, and an in vitro radiolabeled reference tracer Al[18F]F-RESCA-rat serum albumin (RSA) with high radiochemical yield and purity, and acceptable molar activity (Am). The biological evaluation of the tracers showed high radiolabel stability and rapid binding with albumin in vitro and in vivo with the biological half-life in Swiss mice after intravenous administration matching serum albumin (> 18 h). Dynamic PET imaging in female Sprague Dawley rats under ketamine/dexmedetomidine anesthesia after lumbar and intracisternal infusion showed distribution of the tracers towards intracranial space and along the spinal canal from the infusion site. However, the cervical lymph nodes were only visualized after the infusion of Al[18F]F-RESCA-RSA, characteristic for macromolecular tracers, indicating that the gallium-68-labeled tracers did not bind fully to endogenous CSF albumin in vivo, but were distributing to different brain areas according to their physicochemical properties. Conclusions While the relatively low molar activity (Am) of the [68Ga]Ga-NODAGA complex achieved in our setup combined with the limited amount of endogenous albumin at the infusion site (0.012–0.024 nmol) resulted in residual unbound tracer in the rat CSF in vivo, the tracers, especially the Al[18F]F-RESCA-RSA show promise for tracking CSF flow with PET, constituting the first tailored radiotracers to this end. |
| format | Article |
| id | doaj-art-11efa16675f54cc8a1bb72c4ed2bc405 |
| institution | Kabale University |
| issn | 2365-421X |
| language | English |
| publishDate | 2025-07-01 |
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| spelling | doaj-art-11efa16675f54cc8a1bb72c4ed2bc4052025-08-20T03:45:39ZengSpringerOpenEJNMMI Radiopharmacy and Chemistry2365-421X2025-07-0110111810.1186/s41181-025-00365-4Development of new albumin-binding radiotracers for PET imaging of cerebrospinal fluid flow in the glymphatic systemMartta Peltoniemi0Surachet Imlimthan1Sonja C. Jalonen2Niklas Daniel Åke Persson3Terhi J. Lohela4Tuomas O. Lilius5Mirkka Sarparanta6Division of Pharmacology and Pharmacotherapy, Faculty of Pharmacy, University of HelsinkiDepartment of Chemistry, Radiochemistry, Faculty of Science, University of HelsinkiDivision of Pharmacology and Pharmacotherapy, Faculty of Pharmacy, University of HelsinkiDivision of Pharmacology and Pharmacotherapy, Faculty of Pharmacy, University of HelsinkiIndividualized Drug Therapy Research Program, Faculty of Medicine, University of HelsinkiDivision of Pharmacology and Pharmacotherapy, Faculty of Pharmacy, University of HelsinkiDepartment of Chemistry, Radiochemistry, Faculty of Science, University of HelsinkiAbstract Background The glymphatic system is a recently discovered brain-wide clearance system that allows the cerebrospinal fluid (CSF) flow to clear metabolic waste, but the tools for the quantitative and non-invasive investigation of its function and activity especially in humans is lacking, hindering studies on glymphatic system physiology and therapeutic potential of glymphatic drug delivery and modulation. We postulated that albumin-binding radiotracers could be used to this end by binding to the endogenous protein in CSF, constituting a macromolecular, biological radiotracer, allowing for the visualization of CSF flow in the central nervous system non-invasively with positron emission tomography (PET). Results We prepared three albumin-binding tracers based on 4-(p-iodophenyl)butyric acid and truncated Evans Blue radiolabeled with gallium-68 using the NODAGA chelator for in vivo radiolabeling of CSF albumin, and an in vitro radiolabeled reference tracer Al[18F]F-RESCA-rat serum albumin (RSA) with high radiochemical yield and purity, and acceptable molar activity (Am). The biological evaluation of the tracers showed high radiolabel stability and rapid binding with albumin in vitro and in vivo with the biological half-life in Swiss mice after intravenous administration matching serum albumin (> 18 h). Dynamic PET imaging in female Sprague Dawley rats under ketamine/dexmedetomidine anesthesia after lumbar and intracisternal infusion showed distribution of the tracers towards intracranial space and along the spinal canal from the infusion site. However, the cervical lymph nodes were only visualized after the infusion of Al[18F]F-RESCA-RSA, characteristic for macromolecular tracers, indicating that the gallium-68-labeled tracers did not bind fully to endogenous CSF albumin in vivo, but were distributing to different brain areas according to their physicochemical properties. Conclusions While the relatively low molar activity (Am) of the [68Ga]Ga-NODAGA complex achieved in our setup combined with the limited amount of endogenous albumin at the infusion site (0.012–0.024 nmol) resulted in residual unbound tracer in the rat CSF in vivo, the tracers, especially the Al[18F]F-RESCA-RSA show promise for tracking CSF flow with PET, constituting the first tailored radiotracers to this end.https://doi.org/10.1186/s41181-025-00365-4Albumin-bindingCerebrospinal fluid (CSF) flowGlymphatic systemGallium-68IntrathecalPositron emission tomography (PET) |
| spellingShingle | Martta Peltoniemi Surachet Imlimthan Sonja C. Jalonen Niklas Daniel Åke Persson Terhi J. Lohela Tuomas O. Lilius Mirkka Sarparanta Development of new albumin-binding radiotracers for PET imaging of cerebrospinal fluid flow in the glymphatic system EJNMMI Radiopharmacy and Chemistry Albumin-binding Cerebrospinal fluid (CSF) flow Glymphatic system Gallium-68 Intrathecal Positron emission tomography (PET) |
| title | Development of new albumin-binding radiotracers for PET imaging of cerebrospinal fluid flow in the glymphatic system |
| title_full | Development of new albumin-binding radiotracers for PET imaging of cerebrospinal fluid flow in the glymphatic system |
| title_fullStr | Development of new albumin-binding radiotracers for PET imaging of cerebrospinal fluid flow in the glymphatic system |
| title_full_unstemmed | Development of new albumin-binding radiotracers for PET imaging of cerebrospinal fluid flow in the glymphatic system |
| title_short | Development of new albumin-binding radiotracers for PET imaging of cerebrospinal fluid flow in the glymphatic system |
| title_sort | development of new albumin binding radiotracers for pet imaging of cerebrospinal fluid flow in the glymphatic system |
| topic | Albumin-binding Cerebrospinal fluid (CSF) flow Glymphatic system Gallium-68 Intrathecal Positron emission tomography (PET) |
| url | https://doi.org/10.1186/s41181-025-00365-4 |
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