Barnard_2010_P Development of an Oxygen Carrier
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K-8106[ww w.kashan.co.za] Development of an oxygen carrier nanoemulsion for organ preservation A BARNARD 1 , S MSOMI 2 , S MOOLMAN 1 , K NAIDOO 3 1 CSIR Materials Science and Manufacturing , PO Box 395, Pretoria, South Africa, 0001 2 T shwane University of Te chnology , Private Bag X680, Pretoria, 0001 3 CSIR Biosciences, PO BOX 395, Pretoria, 0001 Email: abarnard@csir .co.za – www.csir .co.za INTRODUCTION The current key development focus in organ preservation for transplant purposes is preservation of organs at normothermic or subnormothermic temperatures (i.e at or slightly below physiological temperature) as opposed to cold storage. The current gold standard in organ preservation for transplant is to preserve harvested organs at low temperatures while circulating an organ preservation solution through the organ. The organs however, sustain some damage when exposed to such low temperatures, a phenomenon known as ‘cold perfusion damage’ . It is therefore desirable to transport the organ at temperatures closer to normal physiological conditions (i.e 25 to 37 °C) . This however, substantially increases the organ’s oxygen requirement levels. A critical aspect of organ preservation at higher temperatures is thus the provision of a sufficient oxygen supply to the harvested organ so that the organ can maintain its metabolic rate and remain a viable candidate for transplant. The CSIR has developed a synthetic perfluorocarbon(PFC) based nanoemulsion that serves as an oxygen carrier for the preservation of organs. Perfluorochemicals can be used as oxygen carriers due to their exceptionally high capacity to dissolve gasses 1,2 . Additionally, PFC ’s display high levels of chemical stability and biological inertness which makes them suitable for biological use 1,2 . Perfluorooctyl bromide (PFOB) is the parti cular PFC used in the CSIR oxygen carrier emulsion 1,2 . AIM A collaboration between the Academic Medical Centre (AMC) in the Netherlands and the CSIR aims to combine the nutrient provision abilities of AMC’s organ preservation fluid, ‘Polysol’, with the CSIR’s oxygen carrier to serve as a novel organ preservation solution for normothermic or submormothermic organ storage. Polysol is a liquid that contains proteins, divalent ions, various amino acids and other ingredients designed to provide necessary nutrition to the organ that is being transported. APPROACH Initially, when combining Polysol and the nanoemulsion, the nutrients present in Polysol caused accelerated instability of the nanoemulsion in the form of flocculation and phase separation. Literature states that the addition of polyethylene glycol (PEG) to perfluorocarbon emulsions enhances stability 3 . A two-month stability trial was therefore conducted to investigate the effect of PEG addition on the emulsion and the Polysol-emulsion mixture stability. The stability of the nanoemulsion was determined by measuring the droplet size and zeta p otential of the emulsion through use of a Malvern Zetasizer. RESULTS It was found that sedimentation of the Polysol-PFOB emulsion mixture was largely decreased by the addition of PEG. It was also found that stability was achieved by adding PEG of a specific molecular weight of 20 kD range and specific concentration of 0.2% v/v. INTRODUCTION OF A SILICONE-BASED EMULSION Due to the high cost of the PFC (PFOB is approx. R16 000/kg), a more economically-viable option than the PFC emulsion was sought. A PDMS (poly(dimethylsiloxane)) e mulsion was successfully developed for this purpose. When comparing the PFC and PDMS emulsion it is found that PDMS: • has similar oxygen carrying capacity and similar cytotoxicity to the PFC emulsion with droplet sizes of 140 nm to 160 nm reported during the stability trials as compared to droplet sizes of 220 nm to 360 nm for the PFC emulsion • emulsion is stable in the presence of Polysol or other protein/ amino acid-based aqueous solutions without the addition of PEG • emulsion costs 50 times less than the PFC emulsion. CONCLUSIONS • a stable Polysol-PFC emulsion mixture for organ preservation purposes can be formulated through the addition of 0.2% v/v 20 kD PEG • a PDMS-based emulsion for organ preservation purposes is stable without the addition of PEG A stable organ preservation solution with a high oxygen solubility capacity can potentially provide the nutrients and oxygen required for organ preservation at temperatures closer to normal physiological temperatures, thus increasing the chances of organs being viable for transplant. FUTURE WORK The project team is currently planning acute toxicity in vivo trials for the emulsion formulation, as well as the first in vivo efficacy studies in a rat model. ACKNOWLEGEMENTS The author would like to acknowledge the CSIR for the project funding as well as Academic Medical Centre (AMC) for the provision of Polysol. REFERENCES 1. Moolman, F .S., 2004 a. Oxygen carriers for novel bio-artificial liver support system, PhD dissertation. Pretoria: University of Pretoria. 2. Moolman, F.S., Rolfes, H., Van Der Merwe, S.W. and Focke, W.W. 2004 b. Optimisation of perfluorocarbon emulsion properties for enhancing oxygen mass transfer in a bio-artificial livers support system. Biochemical Engineering Journal 19:237-250. 3. Fukushima, S., Kubota, H., Kishimoto, S., Sakuma, I., Nakai, N., Fujii, S., Kitabatake, A. and Takeuchi, Y. 2003. Effect of pegylation on stability, toxicity and pharmacokinetics of perfluorocarbon emulsion as blood substitutes, Artificial Blood 11(1):122. HE05-PO Figure 1: 40% PFOB-lecithin E80S emulsion and Polysol mixture with, from left to right, 0% PEG, 2% PEG, 2.5% PEG and 3% PEG with Polysol:emulsion ratio 1:1 for a) to d) and ratio 3:1 for e) to h) Improving the viability of organs for transplant using nanotechnology a b c d e f g h
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Oxygen Carriers
Transcript of Barnard_2010_P Development of an Oxygen Carrier
K-8106[ww w.kashan.co.za]
Development of an oxygen carriernanoemulsion for organ preservation
A BARNARD1, S MSOMI2, S MOOLMAN1, K NAIDOO3
1CSIR Materials Science and Manufacturing , PO Box 395, Pretoria, South Africa, 00012Tshwane University of Technology, Private Bag X680, Pretoria, 0001
3CSIR Biosciences, PO BOX 395, Pretoria, 0001
Email: [email protected] – www.csir.co.za
INTRODUCTIONThe current key development focus in organ preservation fortransplant purposes is preservation of organs at normothermicor subnormothermic temperatures (i.e at or slightly belowphysiological temperature) as opposed to cold storage.
The current gold standard in organ preservation for transplantis to preserve harvested organs at low temperatures whilecirculating an organ preservation solution through the organ. Theorgans however, sustain some damage when exposed to suchlow temperatures, a phenomenon known as ‘cold perfusiondamage’. It is therefore desirable to transport the organ attemperatures closer to normal physiological conditions (i.e25 to 37 °C) . This however, substantially increases the organ’soxygen requirement levels.
A critical aspect of organ preservation at higher temperaturesis thus the provision of a sufficient oxygen supply to theharvested organ so that the organ can maintain its metabolicrate and remain a viable candidate for transplant.
The CSIR has developed a syntheticperfluorocarbon (PFC) basednanoemulsion that serves as an oxygen carrier for the preservationof organs. Perfluorochemicals can be used as oxygen carriersdue to their exceptionally high capacity to dissolve gasses1,2. Additionally, PFC ’s display high levels of chemical stability andbiological inertness which makes them suitable for biologicaluse1,2. Perfluorooctyl bromide (PFOB) is the parti cular PFC used inthe CSIR oxygen carrier emulsion1,2.
AIM A collaboration between the Academic Medical Centre (AMC)in the Netherlands and the CSIR aims to combine the nutrientprovision abilities of AMC’s organ preservation fluid, ‘Polysol’, withthe CSIR’s oxygen carrier to serve as a novel organ preservationsolution for normothermic or submormothermic organ storage.Polysol is a liquid that contains proteins, divalent ions, variousamino acids and other ingredients designed to provide necessarynutrition to the organ that is being transported.
APPROACHInitially, when combining Polysol and the nanoemulsion, thenutrients present in Polysol caused accelerated instability of thenanoemulsion in the form of flocculation and phase separation.Literature states that the addition of polyethylene glycol (PEG)to perfluorocarbon emulsions enhances stability 3. A two-monthstability trial was therefore conducted to investigate the effect ofPEG addition on the emulsion and the Polysol-emulsion mixturestability.
The stability of the nanoemulsion was determined by measuringthe droplet size and zeta potential of the emulsion through use ofa Malvern Zetasizer.
RESULTSIt was found that sedimentation of the Polysol-PFOB emulsionmixture was largely decreased by the addition of PEG. It was alsofound that stability was achieved by adding PEG of a specificmolecular weight of 20 kD range and specific concentration of0.2% v/v.
INTRODUCTION OF A SILICONE-BASED EMULSIONDue to the high cost of the PFC (PFOB is approx. R16 000/kg),a more economically-viable option than the PFC emulsion wassought. A PDMS (poly(dimethylsiloxane)) emulsion was successfullydeveloped for this purpose. When comparing the PFC and PDMSemulsion it is found that PDMS:• has similar oxygen carrying capacity and similar cytotoxicity
to the PFC emulsion with droplet sizes of 140 nm to 160 nmreported during the stability trials as compared to droplet sizesof 220 nm to 360 nm for the PFC emulsion
• emulsion is stable in the presence of Polysol or other protein/amino acid-based aqueous solutions without the addition ofPEG
• emulsion costs 50 times less than the PFC emulsion.
CONCLUSIONS• a stable Polysol-PFC emulsion mixture for organ preservation
purposes can be formulated through the addition of 0.2% v/v20 kD PEG
• a PDMS-based emulsion for organ preservation purposes isstable without the addition of PEG
A stable organ preservation solution with a high oxygen solubilitycapacity can potentially provide the nutrients and oxygenrequired for organ preservation at temperatures closer to normalphysiological temperatures, thus increasing the chances of organsbeing viable for transplant.
FUTURE WORKThe project team is currently planning acute toxicity in vivo trialsfor the emulsion formulation, as well as the first in vivo efficacystudies in a rat model.
ACKNOWLEGEMENTSThe author would like to acknowledge the CSIR for the projectfunding as well as Academic Medical Centre (AMC) for the provisionof Polysol.
REFERENCES1. Moolman, F.S., 2004 a. Oxygen carriers for novel bio-artificial liver support system,
PhD dissertation. Pretoria: University of Pretoria.
2. Moolman, F.S., Rolfes, H., Van Der Merwe, S.W. and Focke, W.W. 2004 b.
Optimisation of perfluorocarbon emulsion properties for enhancing oxygen mass
transfer in a bio-artificial livers support system. Biochemical Engineering Journal
19:237-250.
3. Fukushima, S., Kubota, H., Kishimoto, S., Sakuma, I., Nakai, N., Fujii, S.,
Kitabatake, A. and Takeuchi, Y. 2003. Effect of pegylation on stability, toxicity
and pharmacokinetics of perfluorocarbon emulsion as blood substitutes, Artificial
Blood 11(1):122.
HE05-PO
Figure 1: 40% PFOB-lecithin E80S emulsion and Polysol mixture with, from left to right, 0% PEG, 2% PEG, 2.5% PEG and3% PEG with Polysol:emulsion ratio 1:1 for a) to d) and ratio 3:1 for e) to h)
Improving the viabilityof organs for transplant
using nanotechnology
a b c d e f g h
