| 1. |
- Adler, Anna, et al.
(author)
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Regulation of the innate immune system by fragmented heparin-conjugated lipids on lipid bilayered membranes in vitro
- 2023
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In: Journal of materials chemistry. B. - : Royal Society of Chemistry. - 2050-750X .- 2050-7518. ; 11:46, s. 11121-11134
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Journal article (peer-reviewed)abstract
- Surface modification with heparin is a powerful biomaterial coating strategy that protects against innate immunity activation since heparin is a part of the proteoglycan heparan sulfate on cell surfaces in the body. We studied the heparinization of cellular and material surfaces via lipid conjugation to a heparin-binding peptide. In the present study, we synthesized fragmented heparin (fHep)-conjugated phospholipids and studied their regulation of the innate immune system on a lipid bilayered surface using liposomes. Liposomes have versatile applications, such as drug-delivery systems, due to their ability to carry a wide range of molecules. Owing to their morphological similarity to cell membranes, they can also be used to mimic a simple cell-membrane to study protein–lipid interactions. We investigated the interaction of complement-regulators, factor H and C4b-binding protein (C4BP), as well as the coagulation inhibitor antithrombin (AT), with fHep-lipids on the liposomal surface. Herein, we studied the ability of fHep-lipids to recruit factor H, C4BP, and AT using a quartz crystal microbalance with dissipation monitoring. With dynamic light scattering, we demonstrated that liposomes could be modified with fHep-lipids and were stable up to 60 days at 4 °C. Using a capillary western blot-based method (Wes), we showed that fHep-liposomes could recruit factor H in a model system using purified proteins and assist in the degradation of the active complement protein C3b to iC3b. Furthermore, we found that fHep-liposomes could recruit factor H and AT from human plasma. Therefore, the use of fHep-lipids could be a potential coating for liposomes and cell surfaces to regulate the immune system on the lipid surface.
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| 2. |
- Adler, Anna, et al.
(author)
-
Regulation of the innate immune system by fragmented heparin-conjugated lipids on lipid bilayered membranes in vitro
- 2023
-
In: Journal of materials chemistry. B. - : Royal Society of Chemistry. - 2050-750X .- 2050-7518. ; 11:46, s. 11121-11134
-
Journal article (peer-reviewed)abstract
- Surface modification with heparin is a powerful biomaterial coating strategy that protects against innate immunity activation since heparin is a part of the proteoglycan heparan sulfate on cell surfaces in the body. We studied the heparinization of cellular and material surfaces via lipid conjugation to a heparin-binding peptide. In the present study, we synthesized fragmented heparin (fHep)-conjugated phospholipids and studied their regulation of the innate immune system on a lipid bilayered surface using liposomes. Liposomes have versatile applications, such as drug-delivery systems, due to their ability to carry a wide range of molecules. Owing to their morphological similarity to cell membranes, they can also be used to mimic a simple cell-membrane to study protein-lipid interactions. We investigated the interaction of complement-regulators, factor H and C4b-binding protein (C4BP), as well as the coagulation inhibitor antithrombin (AT), with fHep-lipids on the liposomal surface. Herein, we studied the ability of fHep-lipids to recruit factor H, C4BP, and AT using a quartz crystal microbalance with dissipation monitoring. With dynamic light scattering, we demonstrated that liposomes could be modified with fHep-lipids and were stable up to 60 days at 4 degree celsius. Using a capillary western blot-based method (Wes), we showed that fHep-liposomes could recruit factor H in a model system using purified proteins and assist in the degradation of the active complement protein C3b to iC3b. Furthermore, we found that fHep-liposomes could recruit factor H and AT from human plasma. Therefore, the use of fHep-lipids could be a potential coating for liposomes and cell surfaces to regulate the immune system on the lipid surface.
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| 3. |
- Duehrkop, Claudia, et al.
(author)
-
Development and characterization of an innovative heparin coating to stabilize and protect liposomes against adverse immune reactions
- 2016
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In: Colloids and Surfaces B. - : Elsevier BV. - 0927-7765 .- 1873-4367. ; 141, s. 576-583
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Journal article (peer-reviewed)abstract
- Liposomes have been recognized as excellent drug delivery systems, but when they come in direct contact with different blood components they may trigger an immediate activation of the innate immune system. The aim of the present study was to produce long-circulating, blood-compatible liposomes by developing a construct of liposomes covered by a novel unique heparin complex (CHC; 70 heparin molecules per complex) to avoid recognition by the innate immune system. Unilamellar, cationic liposomes were produced by hand extrusion through a 100-nm polycarbonate membrane. Coating of liposomes with the macromolecular CHC was accomplished by electrostatic interactions. Dynamic light scattering as well as QCM-D measurements were used to verify the electrostatic deposition of the negatively charged CHC to cationic liposomes. The CHC-coated liposomes did not aggregate when in contact with lepirudin anti coagulated plasma. Unlike previous attempts to coat liposomes with heparin, this technique produced freely moveable heparin strands sticking out from the liposome surface, which exposed AT binding sites reflecting the anticoagulant potentials of the liposomes. In experiments using lepirudin-anticoagulated plasma, CHC-coated liposomes, in contrast to non-coated control liposomes, did not activate the complement system, as evidenced by low C3a and sC5b-9 generation and reduced leakage from the liposomes. In conclusion, we show that liposomes can be successfully coated with the biopolymer CHC, resulting in biocompatible and stable liposomes that have significant application potential. (C) 2016 Elsevier B.V. All rights reserved.
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| 4. |
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| 5. |
- Klapper, Yvonne, et al.
(author)
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Mediation of a non-proteolytic activation of complement component C3 by phospholipid vesicles
- 2014
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In: Biomaterials. - : Elsevier BV. - 0142-9612 .- 1878-5905. ; 35:11, s. 3688-3696
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Journal article (peer-reviewed)abstract
- Liposomes are becoming increasingly important as drug delivery systems, to target a drug to specific cells and tissues and thereby protecting the recipient from toxic effects of the contained drug. Liposome preparations have been described to activate complement. In this study, we have investigated complement activation triggered by neutral dimyristoyl-phosphocholine (DMPC) liposomes in human plasma and whole-blood systems. Incubation in plasma led to the generation of complement activation products (C3a and sC5b-9). Unexpectedly, investigations of surface-bound C3 revealed contact activated, conformationally changed C3 molecules on the liposomes. These changes were characterized by Western blotting with C3 monoclonal antibodies, and by incubating liposomes with purified native C3 and factors I and H. Quartz crystal microbalance analysis confirmed binding of C3 to planar DMPC surfaces. In addition, we demonstrated that DMPC liposomes bound to or were phagocytized by granulocytes in a complement-dependent manner, as evidenced by the use of complement inhibitors. In summary, we have shown that C3 is activated both by convertase-dependent cleavage, preferentially in the fluid phase, by mechanisms which are not well elucidated, and also by contact activation into C3(H2O) on the DMPC surface. In particular, this contact activation has implications for the therapeutic regulation of complement activation during liposome treatment. (C) 2013 Elsevier Ltd. All rights reserved.
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| 6. |
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