| 1. |
- Bohl Kullberg, Erika, et al.
(författare)
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Development of EGF-conjugated liposomes for targeted delivery of boronated DNA-binding agents
- 2002
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Ingår i: Bioconjugate chemistry. - : American Chemical Society (ACS). - 1043-1802 .- 1520-4812. ; 13:4, s. 737-743
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Tidskriftsartikel (refereegranskat)abstract
- Liposomes are of interest as drug delivery tools for therapy of cancer and infectious diseases. We investigated conjugation of epidermal growth factor, EGF, to liposomes using the micelle-transfer method. EGF was conjugated to the distal end of PEG−DSPE lipid molecules in a micellar solution and the EGF−PEG−DSPE lipids were then transferred to preformed liposomes, either empty or containing the DNA-binding compound, water soluble acridine, WSA. We found that the optimal transfer conditions were a 1-h incubation at 60 °C. The final conjugate, 125I-EGF−liposome−WSA, contained approximately 5 mol % PEG, 10−15 EGF molecules at the liposome surface, and 104 to 105 encapsulated WSA molecules could be loaded. The conjugate was shown to have EGF-receptor-specific cellular binding in cultured human glioma cells.
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| 2. |
- Bohl Kullberg, Erika
(författare)
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Tumor Cell Targeting of Stabilized Liposome Conjugates : Experimental studies using boronated DNA-binding agents
- 2003
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- To further develop cancer therapy, targeted delivery of cell killing agents directly to tumor cells is an interesting approach. This thesis describes the development of PEG-stabilized liposome conjugates targeting either epidermal growth factor receptor (EGFR) using its natural ligand EGF, or human epidermal growth factor receptor 2 (HER-2) using the antibody trastuzumab. Both receptors are known to be overexpressed on a variety of tumors. The liposomes were loaded with the boronated compounds water soluble boronated acridine (WSA) or water soluble boronated phenantridine (WSP), compounds primarily developed for boron neutron capture therapy, BNCT. The liposome conjugates bound specifically to their receptors in cell culture. Because the WSA conjugates exhibited the most favorable boron uptake this compound was chosen for further study. The WSA-loaded liposome conjugates was internalized, an important characteristic for BNCT, and had a long retention inside the cells. The cellular localization of WSA, studied using fluorescence was found to be mainly cytoplasmic. To increase the boron uptake studies comparing different incubation methods was performed. It was shown for both EGF and trastuzumab targeted liposomes the uptake could be increased over 10 times by changing from incubation in monolayer culture to incubation in cell suspension in roller flasks. With this treatment the boron concentrations reached after 24 h incubation time was 90 ppm for EGF-liposomes and 132 ppm for trastuzumab-liposomes, levels that are clinically interesting. To study the cell-killing efficacy of the liposome-conjugates an experimental BNCT study was performed using EGF-liposome-WSA on cultured glioma cells. About half the number of thermal neutron was needed to inactivate 90% of the cells if the cells had been incubated with EGF-liposome-WSA compared to control cells. When comparing the survival to dose it was shown that to inactivate 90% of the cells 2.9 Gy was needed for EGF-liposome-WSA and neutrons compared to 5.6 Gy with 137Cs gamma. The biodistribution of EGF-liposomes was also studied in mice. It was compared to EGF and it was found that the addition of a PEG-stabilized liposome to EGF significantly reduced EGF uptake in liver and kidneys, the circulation time in blood was prolonged as well. The reduced liver uptake might be due to inability of the 100 nm liposomes to pass the sinusoidal fenestrations of the liver and bind to the EGFR-rich hepatocytes. The reduced liver uptake potentates the use of EGF-liposome conjugates for systemic injection.
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| 3. |
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| 4. |
- Kullberg, Erika Bohl, et al.
(författare)
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An aminoacridine derivative for radionuclide therapy : DNA binding properties studied in a novel cell-free in vitro assay
- 2005
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Ingår i: International Journal of Oncology. - 1019-6439 .- 1791-2423. ; 27:5, s. 1355-60
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Tidskriftsartikel (refereegranskat)abstract
- Radiolabelled DNA-binding compounds can be used to increase the efficiency of radionuclide cancer therapy of disseminated disease. In this work, the aminoacridine compound N-[3-(acridine-9-ylamino)-propyl]-3-iodobenzamide (A3) labelled with the Auger-emitting nuclide 125I using Chloramine-T was studied. Optimal labelling conditions of 125I-A3 were investigated and the interaction with DNA was studied using a novel cell-free in vitro assay with naked human genomic DNA in agarose plugs. This novel assay showed to be simple and reliable. The results verify that 125I-A3 specifically binds DNA with low dissociation and is potent in causing double-strand breaks, yielding 1.0-1.4 breaks per decay. In conclusion, 125I-A3 is a most suitable DNA-binding compound for future therapeutic studies of Auger-electron emitters like 125I.
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| 5. |
- Kullberg, Erika Bohl, et al.
(författare)
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EGF-receptor targeted liposomes with boronated acridine : growth inhibition of cultured glioma cells after neutron irradiation
- 2005
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Ingår i: International Journal of Radiation Biology. - : Informa UK Limited. - 0955-3002 .- 1362-3095. ; 81:8, s. 621-629
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Tidskriftsartikel (refereegranskat)abstract
- PURPOSE: To study survival of cultured U-343MGaCl 2:6 glioma cells after incubation with boron-containing liposomes targeting the epidermal growth factor receptor following neutron irradiation. MATERIALS AND METHODS: Epidermal growth factor-tagged liposomes were loaded with water-soluble boronated acridine developed for boron neutron capture therapy, (BNCT). Cellular uptake and distribution were studied. Further, cells were placed at 3 cm depth in a phantom and exposed to an epithermal neutron beam to study clonogenic cell survival. RESULTS: The cellular uptake of boron reached 90 ppm and it was determined by subcellular fractionation that most of the cell-associated boron was located outside of the nucleus. For clonogenic survival, the cells were incubated with epidermal growth factor receptor-targeted liposomes for 4 hours resulting in a cellular concentration of 55 ppm boron (11 ppm 10B). At a fluence of 3 x 10(12) neutrons/cm2 the cell killing effect of the boron-containing epidermal growth factor-liposomes was about ten times higher than for neutrons only. Furthermore, theoretical calculation of the survival by enriched compound (55 ppm 10B), using the parameters from non-enriched compound (11 ppm 10B), shows that the killing effect in this case would be approximately five orders of magnitude higher than for neutrons only. CONCLUSION: The results in this study show that epidermal growth factor-receptor targeted liposomes are suitable as tumor-cell delivery agents of boron for BNCT and support further studies to demonstrate their effectiveness in vivo.
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| 6. |
- Kullberg, Erika Bohl, et al.
(författare)
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Tumor-cell targeted EGF liposomes loaded with boronated acridine : Uptake and processing
- 2003
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Ingår i: Pharmaceutical research. - 0724-8741 .- 1573-904X. ; 20:2, s. 229-236
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Tidskriftsartikel (refereegranskat)abstract
- PURPOSE:The aim of this work was to investigate the cellular binding and processing of polyethylene glycol-stabilized epidermal growth factor (EGF) liposomes. The liposomes were actively loaded with water-soluble boronated acridine (WSA), primarily developed for boron neutron capture therapy.METHODS:The uptake, internalization, and retention of EGF-liposome conjugates were studied in two cultured monolayer cell-lines, A-431 and U-343, with regard to the nuclide-label on the targeting agent, the carrier, and the load. The subcellular localization of WSA was studied using confocal microscopy.RESULTS:We found that the liposome complex was internalized after specific binding to the EGF receptor. After internalization in the tumor cells, WSA was distributed mainly in the cytoplasm and was shown to have long cellular retention, with 80% of the boron remaining after 48 h.CONCLUSIONS: The long retention of the compound and the cellular boron concentration reached makes these targeted liposomes interesting for further development toward boron neutron capture therapy.
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