Question on Wound Healing of Potatoes

[Essential Oil Girl]

Hi,

I plan on performing an experiment on seeing if some medicinal plant extracts can improve wound healing. Because human skin cells would be difficult to purchase and maintain, I've read that one can perform wound healing experiments on potato tubers. I've looked for references on exactly what one would measure as the potatoes are healing, after they are cut. Either I've seen sketchy descriptions or they required more complex equipment than I would have in my high school laboratory. I think that one approach might be to measure the rate of hydrogen peroxide degradation or the rate of change of the catalase enzyme. However, I'm not quite sure how to do either and I'm not even sure if this is the best measurement approach.

I'd appreciate any guidance on this idea.

Thanks for your help.

[donnahardy2]

Hi,

This is a very interesting project. Probably the easiest way to measure wound healing in potatoes is to measure the loss of weight in the tubers. If the wounded potato tuber heals, it becomes more resistant to the loss of water:

http://www.springerlink.com/content/3365306483355070/ (let me know if you can't access this article)

Do you have access to a very sensitive balance? I would guess that you would need a balance that would weigh within +/- 0.01 grams. I recommend doing a quick preliminary trial to make sure this will work for you. If your balance is not sensitive enough to measure the difference between controls and experimental samples, you would need to increase the size (weight) of each sample/control.

You should also plan to include photographs or visual observation to complement the quantitative data.

Donna Hardy

[Essential Oil Girl]

Donna,

Thanks for the reference to the Potato Research article. I have access to some journals, but that is not one of them. I can only see the abstract. Is it possible to send me the full text of the article? I also saw that this is part 2 of a 2 part article; the first part is in that same issue. In part 2, the authors might reference what they did in part one. Is it possible to send that one too.

Regarding the measurement of wound healing, I agree that measuring the weight (due to moisture loss) would be a way to compare my experimental vs. control groups. Thank you for that idea. However, I was looking to get down to more of a mechanistic level of what is going on between the two groups of potatoes I hope to study. I've read that after potatoes are wounded, H2O2 is formed and then an enzyme (catalase?) converts the H2O2 into H2O and O2. I think some people use an O2 sensor to more directly measure how quickly this reaction is occurring. I don't think my high school has an O2 sensor though, so that is why I was looking for any background info on measuring enzyme activity. (I hadn't taken a course where I've studies enzymes yet and so was not sure of how to approach the problem).

I'll find out tomorrow how sensitive our scales are at school and also ask my teachers about measuring enzyme activity. If you have any ideas about the enzyme activity in particular, please let me know.

Thanks in advance if you can send the research papers!

[donnahardy2]

Hi,

I apologize; when I found the McGee potato wound healing reference I didn’t realize I had access only to one page also. I can only access articles that my institution subscribes to, and we don’t subscribe to Potato Research. Since this reference is directly related to your topic, it would be good if you could contact a local university and see if you can get a copy of it. However, I did find other references that should help with the catalase assay.

Here is a website that describes how to measure catalase activity based on the time it takes for a filter paper (containing catalase from the sample) to rise to the surface.

http://www.accessexcellence.org/AE/ATG/ ... /index.php

Here is a science buddies website that describes how to measure carbon dioxide produced by yeast; you could adapt the set up to measure the amount of oxygen produced from hydrogen peroxide due to catalase activity.

http://www.sciencebuddies.org/mentoring ... p009.shtml

Here is a science buddies website that includes information on catalase, but does not include a specific protocol:

http://www.sciencebuddies.org/science-f ... p040.shtml

Here is a website that offers a catalase assay kit for sale, which is based on UV absorption at 240 nm. I definitely do not recommend spending $400 on this kit, but it may give you an idea for making your own assay. You would need a catalase standard and a spectrophotometer that would measure UV absorption and some glass cuvettes.

http://www.nwlifescience.com/index.php? ... Itemid=256

Here is a website that includes a list of parameters you will need to consider including temperature, pH, enzyme concentration and substrate concentration. It also includes a method for trapping the oxygen released from hydrogen peroxide.

http://www.science-projects.com/catalasekinetics.htm

You should plan to spend some time optimizing your catalase assay to make sure it gives reproducible results and is suitable for your sample. Do this before you start your primary experiment. It’s good that you are thinking about measuring catalase since this is the major enzyme in potatoes and it will make a better science fair project with more data. Why don’t you plan to measure weight and catalase activity?

Donna Hardy