OCR Text |
Show 23 college of engineering In the past, hemoglobin-based oxygen carriers have been considered as an option to deliver oxygen but the binding of oxygen to the center of the hemoglobin is difficult1. Also, hemoglobin-based oxygen carriers have been determined to be somewhat more toxic then some of the other options that are available2. To help solve this problem another approach has been proposed that involves the use of perfluorocarbons (PFC). Nanocap-sules filled with perfluorocarbons have been considered as potential oxygen carriers for artificial blood3. PFC's are biologically inert materials that have the ability to dissolve 50 times more oxygen than blood plasma and are rela-tively inexpensive to produce4. However, a major problem is the extreme hydrophobicity of perfluorocarbons, which requires the use of emulsifiers to form oil-in-water emulsions. The synthesized emulsion is composed of 95% L-α-phosphatidylcholine (lecithin) from soybean, 1,2-dioleoyl-sn- glycero-3-phosphate (DOPA), perfluorooctyl bromide (PFOB) that is derived from PFC, and water. A current disadvantage of the emulsion is producing a stable structure that also retains a low particle size. To stabilize the structure a calcium carbonate, CaCO3, coating has been proposed. Calcium carbonate is readily produced and is fairly non-toxic. This coating has the ability to be absorbed into the body without any rejection5, which makes it a good candidate for medical use. The emulsion particles are about 200 nm in diameter so the size of the particles with coating should be less than 500 nm in size. Since nano calcium carbonate have been synthesized with a par-ticle diameter size of about 50 nm6, 7 it will help the size of the particles with the coating to stay within the range of 200-300 nm. We will show that the CaCO3 coating for the lecithin emulsion will provide an optimal particle size, that also provides the emulsion the stability required, in order to then be used as an oxygen carrier. PFOB-filled DOPA nanoemulsions were prepared by mixing pure PFOB, DOPA, lecithin, and DI water. The mixture was stirred at room temperature at a speed of 1200 RPM using a magnetic stirrer. It was then extruded using a 10 mL Thermobarrel LIPEX extruder (Millipore, Billerica, MA) with a 200 nm pore size and the mixture was extruded 5 times. The average diameter of the particles of the non-coated emulsion was determined to be 190 ± 42 nm. After coating the emulsion using the five different concentrations of CaCl2, the size of each sample was re-measured to see the effect on the size of the particles (Figure 1). As the molar concentration of CaCl2 used for the coating increased so did the size of the emulsion particles, from 152 nm to 614 nm in diameter size. The molar concentra-tion of 1x10-2 for CaCl2 was chosen to determine how pH would affect the thickness of the coating. Five different samples of CaCl2 were titrated to pH levels of 1, 3, 5, 7, and 9. The emulsion was mixed with these titrated samples and as seen in Figure 2 the size of the particles increased as the pH increased ranging from 130 to around 750 nm in size. The thickness of the coating is about within the range with which we would like. Future work includes testing for stability of the particles to check for aggregate formations or any coalescence. It will also be important study the stability of the CaCO3 coating in plasma and blood using a calcium ion electrode to make sure there is no long term leaching. Finally of oxygen capacity per unit weight of nanoparticles and the rate of oxygen uptake and download should be performed to confirm they can function as an oxygen carrier in the body. CALCIUM CARBONATE COATING FOR PERFLUOROOCTYL BROMIDE LECITHIN EMULSION Samia Awan (Agnes Ostafin) Department of Bioengineering and Department of Materials Science & Engineering University of Utah UNDERGRADUATE RESEARCH ABSTRACTS Agnes Ostafin Samia Awan Figure 1: Size of coating at various concentrations of CaCl2: Each point is an average of the 5 different runs conducted for each sample. Figure 2: Size of 10-2 CaCl2 coating on 0.1M Na2CO3 relative to pH value: Each point is an average of the 5 runs conducted for that sample. |