WISE RESEARCH: Synthetic Blood
| ||||||||||||||||||||||||
| � | � | � | ||||||||||||||||||||||
| � | ||||||||||||||||||||||||
|
In today's technical society it is becoming more and more of a necessity to rely on synthesized molecules in carrying out complex biomedical procedures. Many natural occurring processes take too long to yield needed products, making it vital to synthesize molecules that mimic the required function. Blood is one type of complex molecule that has forms of imitation compounds. Blood is the means by which the body transports oxygen to the cells. In blood, oxygen is carried by hemoglobin, more specifically by the heme group. The heme group consists of a porphyrin ring enclosing and chelating a metal, iron (Fe). Synthetic blood essentially carries out the same functions as authentic blood does. The iron-heme group in human blood is replaced by the Co(salen) molecule which also carries out the function of transporting oxygen. The prophyrin ring in hemoglobin, is the ligand, in this case, the salen. Where blood has iron, synthetic blood has cobalt (Co). This has shown that metals besides Fe can effectively form reversible complexes with oxygen, hence, making "coboglobin." Consequently, the oxygen-carrying component in synthetic blood is Co(salen). The synthesis of the Co(salen) molecule, synthetic blood, shows amazing similarities not only in function and structure to real human blood, but also in its physical characteristics. | |||||||||||||||||||||||
| � | ||||||||||||||||||||||||
| PROCEDURE | ||||||||||||||||||||||||
|
The first step in producing synthetic blood is preparing the salen H2 ligand. A ligand, a Lewis base, is a neutral molecule or ion having a lone pair of electrons that binds to metal ions. This ligand called salenH2, was formed in a reaction between ethlenediamine and salicylaldhehyde in ethanol. We reacted 1.49g or 0.0122 moles of salicylaldehyde with 0.360g or 0.00599 moles of ethylenediamine to produce 3 mmol of salen H2. From this reaction, it was noticed that the product turned a creamy, bright yellow. We worked under a fume hood and after filtration, the salen H2 yielded was a bright, yellow, powdery product. This reaction induced the formation of a coordinate covalent bond in the metal. By using a melting point apparatus, we checked the purity of the salen. Since our sample did not melt within a difference of one to two degrees we hypothesized that there was excess water in the sample and left it to dry. Our next step was to attach the dry salen H2 ligand to the cobalt metal, to produce our desired product, Co(salen). We performed this process using schlank techniques under nitrogen, because we did not want any of the products, which were air sensitive, to be exposed to oxygen. First we dissolved 0.268g of salen H2 in about 20 ml of ethanol which turned into a yellow solution, and heated it in a hot water bath. Then we added 0.274g cobalt (II) acetate dissolved in a couple of drops of water, which was a pink solution, to the yellow salen H2 solution. The cobalt (II) acetate had to be in excess because the other reactant, salen H2 was the limiting reagent of the reaction. The result of the reaction was a brick red precipitate in a brick red solution. We heated our product for two hours and then put the flask in cold water so that we could later filter off the product. Now that we had formed the synthetic blood molecule, we had to test whether or not it actually mimicked the function of real blood. We weighed out 0.031g of Co(salen) in the glove box. We then added 5 ml of DMSO, which provided oxygen to the synthesized molecule. The resulting solution turned blood red. Since the water in the two burettes, that were supposed to measure the volume of oxygen absorbed, was displaced, this meant that the Co(salen) molecule did pick up the oxygen. We checked to see whether it would perform the reverse function of releasing the oxygen, by adding some chloroform to the solution and amazingly the Co(salen) did release the oxygen because bubbles could be seen rising to the top of the solution when the chloroform was added. UV spectroscopy was performed to see whether or not our samples matched the reference ones. The theoretical method that we used to calculate the amount of oxygen absorbed, required us to weigh out a sample of our Co(salen) product (0.031g) and divide that by the molecular weight of Co(salen) (325g). This yielded 9.5e-5 moles of Co(salen) and assuming that the ratio of Co(salen) to oxygen was 1:1 we hypothesized that 9.5e-5 moles of oxygen were absorbed. However the actual result showed that the ratio between oxygen and Co(salen) was not 1:1. Our experiment happened to yield 0.75 ml of oxygen which converted to 3.3e-5 moles of oxygen. This amount was less than what we expected if we had had a 1:1 ratio. The actual ratio turned out to be 2.9. | |||||||||||||||||||||||
| � | ||||||||||||||||||||||||
| CONCLUSION | ||||||||||||||||||||||||
| We graphed the UV-VIS spectroscopies of Co(salen) and Salen H2. Our graphs were very similar to the standardized reference graphs. This indicated that the reaction was successful and that we reached our target compound. Although Co(salen) can mimic the function of real blood it still, at this point, can not be substituted into the human body because there are other complications involved. But with modification, maybe someday this very synthetic blood that we produced in the lab, will be able to facilitate blood shortages in medical emergencies. �
|
Favourite links
|
|
| ||||||||||||||||||||
