| Autor: |
Koatale PC; Department of Nuclear Medicine, University of Pretoria, Pretoria 0001, South Africa.; Nuclear Medicine Research Infrastructure (NuMeRI), Steve Biko Academic Hospital, Pretoria 0001, South Africa., Welling MM; Department of Radiology, Interventional Molecular Imaging Laboratory, Leiden University Medical Center, 2333 ZA Leiden, The Netherlands., Mdanda S; Department of Nuclear Medicine, University of Pretoria, Pretoria 0001, South Africa.; Nuclear Medicine Research Infrastructure (NuMeRI), Steve Biko Academic Hospital, Pretoria 0001, South Africa., Mdlophane A; Department of Nuclear Medicine, University of Pretoria, Pretoria 0001, South Africa.; Nuclear Medicine Research Infrastructure (NuMeRI), Steve Biko Academic Hospital, Pretoria 0001, South Africa., Takyi-Williams J; Therapeutics Systems Research Laboratories (TSRL), Inc., Ann Arbor, MI 48109, USA., Durandt C; Department of Medical Immunology, Institute for Cellular and Molecular Medicine, University of Pretoria, Pretoria 0001, South Africa.; South African Medical Research Council Extramural Unit for Stem Cell Research and Therapy, University of Pretoria, Pretoria 0001, South Africa., van den Bout I; Department of Physiology, University of Pretoria, Pretoria 0001, South Africa., Cleeren F; Department of Pharmacy and Pharmacological Sciences, Radiopharmaceutical Research, KU Leuven, 3000 Leuven, Belgium., Sathekge MM; Department of Nuclear Medicine, University of Pretoria, Pretoria 0001, South Africa.; Nuclear Medicine Research Infrastructure (NuMeRI), Steve Biko Academic Hospital, Pretoria 0001, South Africa., Ebenhan T; Department of Nuclear Medicine, University of Pretoria, Pretoria 0001, South Africa.; Nuclear Medicine Research Infrastructure (NuMeRI), Steve Biko Academic Hospital, Pretoria 0001, South Africa. |
| Abstrakt: |
The ability of bacteria to recycle exogenous amino acid-based peptides and amino sugars for peptidoglycan biosynthesis was extensively investigated using optical imaging. In particular, fluorescent AeK-NBD was effectively utilized to study the peptidoglycan recycling pathway in Gram-negative bacteria. Based on these promising results, we were inspired to develop the radioactive AeK conjugate [ 68 Ga]Ga-DOTA-AeK for the in vivo localization of bacterial infection using PET/CT. An easy-to-implement radiolabeling procedure for DOTA-AeK with [ 68 Ga]GaCI 3 followed by solid-phase purification was successfully established to obtain [ 68 Ga]Ga-DOTA-AeK with a radiochemical purity of ≥95%. [ 68 Ga]Ga-DOTA-AeK showed good stability over time with less protein binding under physiological conditions. The bacterial incorporation of [ 68 Ga]Ga-DOTA-AeK and its fluorescent Aek-NBD analog were investigated in live and heat-killed Escherichia coli ( E. coli ) and Staphylococcus aureus ( S. aureus ). Unfortunately, no conclusive in vitro intracellular uptake of [ 68 Ga]Ga-DOTA-AeK was observed for E. coli or S. aureus live and heat-killed bacterial strains ( p > 0.05). In contrast, AeK-NBD showed significantly higher intracellular incorporation in live bacteria compared to the heat-killed control ( p < 0.05). Preliminary biodistribution studies of [ 68 Ga]Ga-DOTA-AeK in a dual-model of chronic infection and inflammation revealed limited localization at the infection site with non-specific accumulation in response to inflammatory markers. Finally, our study demonstrates proof that the intracellular incorporation of AeK is necessary for successful bacteria-specific imaging using PET/CT. Therefore, Ga-68 was not a suitable radioisotope for tracing the bacterial uptake of AeK tripeptide, as it required chelation with a bulky metal chelator such as DOTA, which may have limited its active membrane transportation. An alternative for optimization is to explore diverse chemical structures of AeK that would allow for radiolabeling with 18 F or 11 C. |
