Author Topic: Article: Properties of Ionic Vs. Metallic Colloidal Silver  (Read 1039 times)

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Offline PeterXXL

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Article: Properties of Ionic Vs. Metallic Colloidal Silver
« on: December 26, 2014, 06:30:32 AM »
In this article, I noticed something that I regard as an error...

At the label "Physical Differences"

Quote: "...This makes silver metal nanoparticles attract to positive charged pathogens, and silver ions attract to negative charged healthy human cells...."

However...

There's a classification of bacteria based on the thickness of their cell membranes - gram positive and gram negative. Note: there are also bacterias that does not have a cell membrane. Positive and negative here does NOT have anything to do with charge. The Gram positive bacterial cell wall is made up of thick peptidoglycan layer which is rich in Teichoic acids. These teichoic acids are negatively charged because of presence of phosphate in their structure. The Gram negative bacteria have an outer membrane composed of phospholipids and Lipopolysaccharides. The lipopolysaccharides impart a strongly negative charge to surface of Gram negative bacterial cells.

So...

- ALL bacteria that are either gram positive or gram negative have a NEGATIVE charge cell wall, where the gram negative bacteria have a much stronger charge than the gram positive.

Ref; http://www.answers.com/Q/Why_do_bacterial_cell_walls_carry_a_negative_charge
Ref: http://www.columbia.edu/itc/hs/medical/pathophys/id/2009/introNotes.pdf

On the other hand, bacteria can also be classified as Aerobic (in need of oxygen) and Anaerobic (not in need of oxygen). And the latter (Anaerobic bacteria) produces carbon dioxide, protons, and electrons (while Aeroobic) only produces carbon dioxide and water.

Ref: http://www.ncbe.reading.ac.uk/ncbe/protocols/PRACBIOTECH/PDF/bennetto.pdf

But...

- Some Anaerobic bacteria can be positive charged (as they produces electrons).

Or have I missed something?!


Offline kephra

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Re: Article: Properties of Ionic Vs. Metallic Colloidal Silver
« Reply #1 on: December 26, 2014, 10:20:14 AM »
In this article, I noticed something that I regard as an error...

At the label "Physical Differences"

Quote: "...This makes silver metal nanoparticles attract to positive charged pathogens, and silver ions attract to negative charged healthy human cells...."
Physics says this is true.  Unlike charges attract, like charges repel -- no exceptions, always.  The physical world from nano to macro is always trying to equalize itself.  Entropy always wins in the end.  However, the question should be whether this applies or not.  It is a good model though (physics is not reality, it is a model of reality) as it explains what actually happens.  Zeta potential explains it better, but is a lot harder to understand.

Quote
However...

There's a classification of bacteria based on the thickness of their cell membranes - gram positive and gram negative. Note: there are also bacterias that does not have a cell membrane. Positive and negative here does NOT have anything to do with charge. The Gram positive bacterial cell wall is made up of thick peptidoglycan layer which is rich in Teichoic acids. These teichoic acids are negatively charged because of presence of phosphate in their structure. The Gram negative bacteria have an outer membrane composed of phospholipids and Lipopolysaccharides. The lipopolysaccharides impart a strongly negative charge to surface of Gram negative bacterial cells.

So...

- ALL bacteria that are either gram positive or gram negative have a NEGATIVE charge cell wall, where the gram negative bacteria have a much stronger charge than the gram positive.
If that were true, the bacteria would not be able to invade normal cells, as they would be repelled.  Does that happen?  Obviously, pathogens do invade healthy human cells, so they must be relatively positive with respect to the healthy cell wall.

Ref; http://www.answers.com/Q/Why_do_bacterial_cell_walls_carry_a_negative_charge
[/quote]
Not a scientific reference.
Quote
Ref: http://www.columbia.edu/itc/hs/medical/pathophys/id/2009/introNotes.pdf

On the other hand, bacteria can also be classified as Aerobic (in need of oxygen) and Anaerobic (not in need of oxygen). And the latter (Anaerobic bacteria) produces carbon dioxide, protons, and electrons (while Aeroobic) only produces carbon dioxide and water.

Ref: http://www.ncbe.reading.ac.uk/ncbe/protocols/PRACBIOTECH/PDF/bennetto.pdf

But...

- Some Anaerobic bacteria can be positive charged (as they produces electrons).

Or have I missed something?!
Aerobic or anaerobic is irrelevant. 
One thing I think you are missing is that no biological cells produce free electrons.  The paper you referenced shows a chemical half reaction which only exists for a very short time before completion as the electrons are taken up by reducing the hydrogen ions to hydrogen.  Every redox reaction involves the transfer of electrons.  If you could harvest those electrons in Fig 2, what would happen to the hydrogen ions?  They would have to find electrons elsewhere by oxidizing something else and charge balance would be retained.  There is no net production of free electrons.  Even an ordinary electrical battery does not produce net free electrons.  For every electron leaving the negative electrode there must be one returned to the positive electrode resulting in redox reactions with electrode materials.

Its the exudate from the bacteria that becomes a reducing agent, and there have been papers written showing that the respiration byproducts of bacteria will reduce silver ions to silver (everyone wants to write a paper about green something or other).  This is why ionic silver kills ecoli, as the ions are reduced to silver metal in-vitro, and the test does not actually show ionic silver as effective unless this effect is also taken into account.

However, you have a valid point, and I should perhaps clarify this.  Positive and negative are relative.  For example, electrons normally flow out of the negative terminal of a battery, but if you connect a nine volt battery to a 1.5 volt battery positive to positive and negative to negative, the electrons will flow into the negative terminal of the 1.5 volt battery.  IE, the 1.5 volt battery negative terminal is actually positive with respect to the nine volt battery, so current flow is reversed.  This applies to Zeta potentials also.

So my statement is very simplified, but I talk to a general audience with basically no scientific background which is mostly who I write for.  In actuality it would probably be better explained in terms of Zeta potential which takes into account the medium the cells live in, but would be less understandable.  Physics applies to all biology, no matter how complicated. 

The Zeta potential model is better because it can explain why some kinds of bacteria are more susceptible to silver nanoparticles than others, and why gold nanoparticles tend to migrate to cancer cells. 

I commend you on your analysis, you are the first person to actually bring up these points.

Well done.

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