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CHEMISTRY 1000

CHEMISTRY 1000. Topics of Interest #3: Acid, Baking Soda and Cancer. Acidity and Illness. Tissues containing cancerous cells (or fighting off an infection) tend to be more acidic than healthy tissues.

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CHEMISTRY 1000

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  1. CHEMISTRY 1000 Topics of Interest #3: Acid, Baking Soda and Cancer

  2. Acidity and Illness • Tissues containing cancerous cells (or fighting off an infection) tend to be more acidic than healthy tissues. • If we could measure tissue pH non-invasively, we could potentially use that to detect cancer. We could also use it to monitor whether a tumour is growing or shrinking in response to treatment. • Magnetic Resonance Imaging (MRI) allows us to examine the chemical environment of all atoms of a particular isotope. • The original form of this technology is widely used in chemistry labs where it goes by the name Nuclear Magnetic Resonance (NMR) because it is looking at the chemical environment around a nucleus. It is a major topic of Organic Chemistry 2 (CHEM 2600). F.A. Gallagher et al Nature (2008) 453, 940-943

  3. Detecting Acidity in Tissue • At first glance, you might think that the way to look for acidity in tissue would be to look at all of the 1H atoms and see how many exist as H+. This might work in theory but, in practice, signals from all of the other 1H atoms in the cell would probably obscure the signal. • We need to use an isotope that’s not as common in the body so that we can just look at it. MRI doesn’t work well on 2H, and 3H is radioactive, so we want to look at elements other than hydrogen. • We need something safe to put in our bodies that will contain an uncommon (and non-radioactive!) isotope and that will react with acid. F.A. Gallagher et al Nature (2008) 453, 940-943

  4. Detecting Acidity in Tissue • The pH of our blood is maintained by buffers – one of which is a carbonate buffer (i.e. a mixture of CO2, HCO3- and CO32- where the ratio of the three species determines/is determined by pH). • Looking at 12C would be as difficult as looking at 1H but, if we added HCO3- containing 13C instead of 12C, we could then look at what happened to the 13C! • When HCO3- reacts with acid, CO2 is produced, so when H13CO3- reacts with acid, 13CO2 is produced: so F.A. Gallagher et al Nature (2008) 453, 940-943

  5. Detecting Acidity in Tissue • We can see that the two 13C atoms are in different chemical environments. NMR can tell that too (see right) and can tell what fraction of 13C atoms are in H13CO3- and what fraction are in 13CO2. F.A. Gallagher et al Nature (2008) 453, 940-943

  6. Detecting Acidity in Tissue • The images below show a section of mouse tissue containing a tumour. In the image on the left, the tumour is outlined in red. In the image on the right, we can see the tumour using this imaging technique! F.A. Gallagher et al Nature (2008) 453, 940-943

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