Back in february before Madelyn was born , i was corresponding with Nathan  Kuehne the young man from Victoria who is working on the home phe testing device. 

After watching his amazing tedx talk on the device that was posted to youtube back in december i had a few questions so i wrote an email to nathan , and he has allowed me to share his responses on my blog.

Amanda :

From what I understand , the test turns purple in the presence of PHE. However since we area always eating protein and a limited amount of phe is always in our blood, this would mean that the test should always read positive? What I would like to know, is have you developed a way to accurately detect and read in numbers just how much phe is in the urine? Like reading? it is not enough to just have the presence detected, for treatment, we need to be able to read how much is present. Like on the home tests being developed with blood, they have a screen that produces a digital number. Will your device be able to do the same?

Nathan:

First off, I need to preface my answers to all the questions with a bit of a disclaimer. Due to the nature of a TEDx talk, it is hard to delve into the chemistry in sufficient detail to cover all the aspects of the project. As a result, many of the obvious questions that would arise from my work, especially for a PKU patient, would not be found online in the talk, but are questions I have definitely considered and I include in my other presentations (competitions, Science Fair, interviews, ect.)

Anyway, the answer to your question is both yes, and no. You are absolutely correct, any Phe will start the chemical process and produce nanoparticles, and thus the colour change. Having said this, the reaction is not a runaway train after that (bad analogy, my apologies). Only so many nanoparticles will be produced as there is Phe in the solution. This means a gradient will be produced depending on the amount of Phe in the sample. The more Phe, the darker the solution; I’ve included a picture that demonstrates this more easily than I can in words (Figure 1).

With this in mind, I was planning on developing something along the lines of a pH chart for people to read their levels. It could be a small piece of paper or something equivalent, and it would show a gradient of purple, and what concentration each colour corresponded to. This would give people the ability to attach a numerical value for blood concentration to their visual test, and thus determine how much is present.

Alternatives to the chart include using solution conductivity. Since the solution produces gold nanoparticles, the conductivity of the solution would increase as the amount of Phe increases. This way, I could imbed a program that converts solution conductivity to an actual value, taking away the risk associated with visual interpretation of a chart. While I acknowledge that this would be a much better method to go about the test, as a high-school student, it is slightly out of my reach at the moment to pursue and develop electronic integration to my test, therefore I am more included to pursue the chart at the moment. However, this may change as I continue to work on it.

Amanda :

my second question is : Many of the home tests in developed by the NPKUA and previously by Biomarin, have had trouble with accuracy when phe levels like mine are in the low range. Does your device operate similarly? how can you improve the accuracy for lower range levels? Idealy PHE levels in anyone should be 2-6 mg / dl so that would be considerably lower then say someone who is suffering from high levels. My highest level I ever had was 25 mg/ dl.

Nathan:

As I mentioned in my answer to the first question, there is a lot of more complex experimentation I leave out of my presentations, and this is one of them. As part of my research, I did tests regarding a concept called the Limit of Detection, or the LOD. Essentially, this is a test that determines how sensitive my test is, and gives me a value of how low the concentration of Phe can be for me to know if the colour change is because of Phe or if the colour change is due to experimental error.

My LOD was below that of the low-end range of Phe levels in PKU patients, according to published literature, meaning my test works for all concentrations of Phe. However, I am not 100% sure how the accuracy changes at those lower levels – that will take more research to determine. I am optimistic, considering the reliability of gold nanoparticle production with Phe, that the accuracy should not change very much.

Amanda:

There are 2 systems for reading PHE results. In canada we use the milligrams per deciliter and in the states or the uk we see that they use the umol/ L system . where levels range is 120-360 . What system would your device use?

Nathan:

Regardless if I pursue the chart system, or the conductivity system, since mg/dl to µM/L is a simple conversion, it would be very to make my test useable in both locations, with both sets of units included.

Amanda :

have you been approached or applied to either the NPKUA, CanPKU or the government for any sort of assistance in developing your device or plan to?

Nathan:

I have not been approached nor have I applied to any agency or organization for assistance, and this is for a few reasons. The main reason is that I am working on a slightly different project at the moment, which may replace the device I developed and presented in my TEDx talk. I am trying to port the chemical aspect of the test to a specially designed piece of paper, and as a result, remove the need for the device. Because as much as I like it and am proud of it, it is large and fairly cumbersome. As an extension, this new test would, theoretically, include the capability to test for types of cancer, Alzheimer’s, and other metabolic disorders like PKU. It is still in the research phase, and as a result, I can’t speak to whether it will be successful or not. If all goes well, this new platform will be the method of testing for PKU.

If it is not successful, I will consider returning to the device, and trying to optimize parts of that system. With this in mind, I have not sought out funding or support yet because, quite honestly, I am not sure what will work best and as a result, what I may try and develop further.

Amanda :

And lastly, if it is ok with you, once you have replied, may i publish this conversation to my blog? with your permission of course. I think these are all questions we have had since you have entered our world and it has spurred many conversation on social media.

Nathan:

Yes, I would be happy for you to share my answers. I have been in contact with a few other members of the PKU community as a result of places I have posted my talk, and I would love for these answers to reach people like them.