Hello All,
I'm fabricating a simple glucose sensor using a platinum wire as working electrode coated with Glucose oxidase, BSA, glutaraldehyde and Nafion. I ran the CV against a platinum counter and Ag/AgCl reference to find the oxidation potential at +0.5 V. I ran chronoamp at this fixed potential for a final concentration ranging from E-12 M to 1M of sucrose, equally aliquoted in PBS but I didn't see any changes in my current increasing like a staircase as is in all chronoamps!! It's been 4 trials and I seem to not find the culprit.
The way I coat:
I dip the wire in each solution for 1-2 hours in RT, dry and wash with DI before use. (not sure if the large amount of solution on the wire might affect the coating, should I decrease the amount to a couple of microliters at the tip? )
The way I run the experiment:
run for 100 seconds, pause, inject the sample, stir for 45 seconds, run again for another 100 Sec. (I've also seen that it should be possibly continuous stirring, could this be the issue? )
Any ideas and feedback will be appreciated.
Thank you very much.
If you want to make a sensor you should understand what chemistry is going on in your system. Read DOI 10.1021/cr068069
" final concentration ranging from E-12 M" Are you serious?
Hi Yurii,
Thank you I have already gone through the literature you've mentioned.
Of course I understand the chemistry and the previous sensor we fabricated for cyanide detection had a LOD of 1 femto molar (-15), so in a microelectrode array system such low concentrations are expected.
The chemistry is not my question anyways, the point is I need to learn Chronoamperometry and I would appreciate your feedback on that topic.
Hello Maedeh,
I am trying to do a same project. The only difference is that I am using gold electrodes and I use chitosan to immobilize GOx. I also electrodeplate prussian blue on my electrode (for H2O2 reduction). I have the same problem let me know if you found a solution.
By the way what type of GOx are you using?
Hi Mozneb, why you use sucrose as substrate? Maybe you should use glucose.
Hi Maedeh,
So just to get this right: when you measure chronoamperometry you get the same current, irrespective of substrate concentration? Have you tried running CV or SWV at these different concentrations? Especially SWV is very sensitive.
One thing to consider is the diffusion of the substrate: if your oxidation at the electrode is faster than the diffusion supplying the material to the enzyme you will see that as limiting factor and not necessarily the concentration of the substrate.
Hello Maedeh,
In my opinion, the way you followed to run the experiment is different than mine. In my case, I keep stirring continuous at a constant rate throughout the experiment. Stirring condition ensures homogeneity of the solution after the injection of sample at a definite time interval.
And during injecting sample, I do not pause the experiment. Rather I inject the sample at a certain time interval under running condition with stirring on.
You can check the following article to know more about it.
Article Fabrication of nanostructured Pd thin films using aerosol-as...
Dear Maedeh,
I think the comments of Li-Fan Hsu and Tamanna Islam are very good.
First, I would recommend you to use glucose and to check that the enzyme you are using is actually working at least in solution by using another technique (a colorant reacting to hydrogen peroxide or a test in the spectrophotometer).
Second, if you don't see ANY current variation in the range you cited, it's not a problem of stirring or of the technique you are using but of the materials or of their deposition. I suggest you to check by CV with and without an high glucose concentration, if the oxidation peak you are considering is actually that one related to the GOx catalysis of glucose (you shall simply compare the two CV measurements to see at what potential the signal is changing).
Good luck and if you want I could take a look to the results to help you.
Bests,
GR
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