Zeta Potentials

ByJessica Snyder

This post shows that C-dots are pretty close to neutral.  Here I’ve looked at gold nanoparticles and albumin.

5nm Gold:

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The distribution is very spread out, but everything centers around -58 mV.

10nm Gold:

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This sample looks a little bimodal.  Peaks are at -33 and 0 mV.

Albumin:

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Much better than the gold samples.  It looks like the zeta potential is about -20 mV for albumin.

I’ll look at some other proteins soon, but from this analysis so far, C-dot are the lowest charged species that we use and gold is the highest.

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2 Comments

  1. As I recall, albumin is considered a strongly negative protein, right?  If so, the Au is very negative, so it’s not surprising that you have had difficulty passing it through our negative membranes.  Have you tried APTES treatment to try and neutralize the membrane charge or even make it positive?

    How should we interpret the different potentials of the 5nm and 10nm gold?  Is it real or is there some kind of error in the measurements?  Is the larger gold even less charged?

  2. Albumin is a protein with a pI below 7, so should be negatively charged in this solution.  The zeta potential agrees with this. 

    Gold is even more highly charged than albumin, but I’m do not know why there is a difference between the different sizes.  This is something I wanted to test, but didn’t know what to expect.  To form the different sizes of gold you use different stoichiometries of chloroauric acid to citrate, so maybe there is a different in amount of citrate per particle.  I would consider the smaller particle to have less citrate though if it was just a case of capping.  This is something I plan on researching a bit more.

    I’ve tried APTES treatment of pnc-Si, and performed EO, but the EO rate does not indicate a positive surface.  I don’t know a good way of getting the potential of the APTES treated surface, and at any rate my first try of silanization was rough.  Carbonization does not seem to affect the potential that much.  I think that finding the right treatment to knock out membrane charge is the way to go with this stuff.

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