Diabetes Research Group
King's College London
Nanobiotechnology to deliver anti-inflammatory agents to islet transplantation sites
Amazon LF Austin1, Zheng-Liang Zhi1, Shanta J Persaud1, Peter M Jones1, Aileen J King1.
1Diabetes Research Group, King’s College London Faculty of Life Sciences & Medicine, Guy’s Campus, London, SE1 1UL, UK, London, United Kingdom
Introduction: Inflammation is an obstacle for islet transplantation. α1-antitrypsin is a serum protease inhibitor with proven anti-inflammatory properties as well as many other clinical benefits such as anti-thrombotic and immunomodulatory effects. Our aim is to use nanotechnology to locally deliver this protein to the site of islet transplantation in both multi-layered α1-antitrypsin nanocapsules and by using α1-antitrypsin containing nanoparticles within alginate microcapsules.
Methods: Islets were isolated from ICR and C57Bl/6 mice and nanoencapsulated with an alternating layering scheme of two glycol-chitosan/heparin-aldehyde bilayer and two glycol-chitosan/α1-antitrypsin bilayers with a final layer of α1-antitrypsin. The ICR islets were cultured in the absence or presence of cytokines (IL-1β (1ng/ml), TNFα (5ng/ml) and IFNγ (5ng/ml)) and islet cell viability was measured using a real-time fluorescence viability assay. 175 unmodified or nanoencapsulated C57Bl/6 islets were transplanted under the kidney capsule of streptozotocin-diabetic C57Bl/6 recipient mice in a minimal mass model and blood glucose was measured over 28 days to assess transplantation outcome.
Nanoparticles incorporating α1-antitrypsin were made using serum albumin, polyethylglycol and heparin. The release of the protein from the nanoparticles was determined using radiolabelled (125I) α1-antitrypsin. Nanoparticles incorporating α1-antitrypsin were co-encapsulated with ICR mouse islets within alginate beads (with a high (approximately 60%) guluronic acid content gelled with 50 mM CaCl2 and 1 mM BaCl2.). The function of the islets co-encapsulated with or without α1-antitrypsin nanoparticles was assessed using a dynamic secretion system to measure glucose induced insulin secretion.
Results: Nanoencapsulation: The viability of α1-antitrypsin nanoencapsulated islets challenged with cytokines was significantly higher compared to unmodified islets challenged with cytokines at 24 hours (Nanoencapsulated = 98308±16403 Relative Luminescence Units (RLU) and unmodified = 66492±14202 RLU; p<0.05) and 48 hours (Nanoencapsulated = 87173±7935 RLU and unmodified = 57940±11814 RLU; p<0.05) showing the ability of the coating to protect the islets from cytokine-mediated damage. At day 3 after transplantation, when inflammation is high, 38% of the α1-antitrypsin nanocoated islet group had blood glucose <12mM vs 17% of the unmodified islet group. However, this effect was lost by day 7 indicating a lack of long-term effect.
Microencapsulation: Nanoparticles released up to 17% total radiolabelled 125I-α1-antitrypsin within 24 hours and 21% by 48 hours indicating efficient release of the active protein from the nanoparticles. Microcapsules containing islets and nanoparticles showed a similar insulin secretion to those with no nanoparticles demonstrating that nanoparticles do not interfere with normal islet secretory function.
Conclusion: The incorporation of α1-antitrypsin in nanocapsules protected islets from a hostile microenvironment in vitro but this was not sustained long-term in vivo. Nanoparticles containing α1-antitrypsin release the protein over a time-frame that could be therapeutically useful in reducing early inflammatory events in microencapsulated islet transplantation.
This work was supported by a grant from the Juvenile Diabetes Research Foundation (JDRF).
15:30 - 16:30
|Zeroing in on the Perfect Encapsulation and Immunoisolation Device||Nanobiotechnology to deliver anti-inflammatory agents to islet transplantation sites||Room 110|