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Polymeric Nanoconstructs as Oxygen Carriers

VI Convegno Nazionale sulla Scienza e Tecnologia dei Materiali 12-15 June 2007, Perugia, Italy. Polymeric Nanoconstructs as Oxygen Carriers. Anna Maria Piras , Federica Chiellini, Alberto Dessy BIOlab UdR INSTM, Department of Chemistry and Industrial Chemistry, University of Pisa, Italy.

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Polymeric Nanoconstructs as Oxygen Carriers

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  1. VI Convegno Nazionale sulla Scienza e Tecnologia dei Materiali 12-15 June 2007, Perugia, Italy Polymeric Nanoconstructs as Oxygen Carriers Anna Maria Piras, Federica Chiellini, Alberto Dessy BIOlab UdR INSTM, Department of Chemistry and Industrial Chemistry, University of Pisa, Italy

  2. Oxygen Carriers • To be administered for the immediate re-establishment of O2 homeostasis in case of urgent need • No need of cross-matching • Prolonged storage conditions Free Hb: not feasible Short circulation times Abnormally high O2 affinity Breakdown into dimers • Renal Toxicity • Haemoglobinuria • Malaise • Abdominal pain Acellular Hb-based O2 Carriers • Cross-linked Hb • Polymerised Hb • Polymer Conjugated Hb • Low O2 affinity • Plasma expanders • Hypertension Cellular Hb-based O2 Carriers Encapsulated Hb Co-encapsulation of enzymes and reductants • Enhancement of Hb half-life • No osmotic effect

  3. PEG moieties Hemoglobin Cofactors Bioerodible Polymer Aim of the Work Development of Polymeric Bioerodible Nanoparticles as Hemoglobin Based Oxygen Carriers Oxygen Release Particle Erosion Removal from Blood Circulation

  4. Materials Polymers VAM41-PEG:2-methoxyethanol hemiesters of poly(maleic anhydride-co-butylvinylether)5% PEG2000 Active Agent Hb:Human Hemoglobin GLYx-HPMAy:poly(methacryloylglycylglycine-OHx -co-hydroxypropylmethacrylamidey) Stabilizer GiG-bCD: 1–O–glycidyl–2,3–O–isopropylidenglyceryl--cyclodextrin

  5. Bioerodible Polymers: VAM41 C6H6 AIBN 60 °C DCM THF 75°C DMAP

  6. VAM41-5%PEG2000 5% PEG grafting To achieve stealth effect on nanoparticles Purified by ion exchange chromatography Process yield: 92%

  7. Materials Compatibility with Hb The influence of nanoparticle components on Hb-Oxygen interaction was evaluated through UV-VIS spectroscopy under oxygenated and deoxygenated conditions. Mixtures of nanoparticle components and Hb were tested. No major difference on Hb capability of reversibly bind oxygen

  8. Nanoparticles Preparation Co-precipitation Technique Under controlled atmosphere and Temperature

  9. Particle Characterisation Methods • Granulometry in Suspension: Dynamic Light Scattering • Scanning Electron Microscopy (SEM) • Surface Features: Zeta Potential • Protein Detection: Drabkin’s Assay • Encapsulation Efficiency (EE%) • Loading (%) • Particles Erosion Rate: Dialysis Diffusion technique • Citotoxicity: LDH Assay on Mouse Embryo Fibroblasts

  10. Formulation Set - Up Formulation 12T-2 Formulation 5T-2 Formulation V11T-2

  11. Light Scattering Nanoparticles: Controlled Conditions Homogeneous colloidal suspensions Diameter (139 ± 21)nm Zeta Potential (-5.38 ± 0.22) mV SEM Micrograph Drabkin’s reagent Hb loading: (57 ± 1.7)% w/w Hb Encapsulation Efficiency: 88%

  12. Erosion Kinetics Diffusion through dialysis membrane (EC, MWCO:100 kDa) Hb loaded nanoparticles Conditions: PBS pH 7.4, RT. Nanoparticles displayed slow and progressive bioerosion that reached the 77% of complete dissolution after 55 hours.

  13. Citotoxicity Evaluation Hb displays a high cytotoxicity in vitro due to its active role in oxidative reactions and for strong interactions with cellular membranes. Cell line: Balb/3T3 Clone A31 balb/c murine embryo fibroblast LDH assay: lactate dehydrogenase (LDH) release assay Hb loaded Nanoparticles suspensions show Reduced Cell Mortality in comparison to free Hb

  14. Anti-oxidants Antioxidant agents were employed in nanoparticles preparation The encapsulated Hb displays a predominant fraction of metHb Citric Acid Ascorbic Acid/Leucomethylene Good nanoparticles morphology and diameter distribution 2mM Citric Acid (80  51)nm Leuco/Hb=75 (103  93)nm No major benefit on Hb preservation was evidenced

  15. New Strategies Alternative Materials GLY25-HPMA75 VAM41-PEG modified with antioxidant moieties, reduced number of free COOH M. Gizdavic-Nikolaidis et al. Curr. Appl. Phys 4:347-350 (2004) M. Li et al., Biomaterials 27:2705-2715 (2006) Modulators of Hemoglobin Affinity to O2 2,3-diphosphoglycerate (2,3 DPG) Pyridoxal-5’-Phosphate (PLP)

  16. GLY25-HPMA75 Nanoparticles Optimized with Human Albumin as Model Protein (12717)nm Applied to Hb, under N2 and at 4°C (7842)nm

  17. Conclusions • Core-Corona Hb loaded Bioerodible Nanoparticles were prepared. • Nanoparticles display an homogeneous diameter distribution (14020)nm, good surface properties, high EE% and Loading. • Preliminary toxicity investigation evidenced a reduced cytotoxicity compared to free Hb. • GLYx-HPMAy polymers appear also suitable for the development of Hb based Oxygen carriers. • New co-factors and polymeric matrices will be investigated for preserving Hb functionality.

  18. Acknowledgments • The presented results have been attained within the framework of the “Sviluppo Nuovi Derivati del Sangue” financed project by MIUR. • Polymer Laboratories (UK) for supplying polymeric materials, prepared within the EC-project “TATLYS” G5RD-CT-2000-00294 • Mr. Piero Narducci in recording SEM images of Nanoparticles

  19. Thanks for Your Attention

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