Deposition Quantification Methods?

[Helepolis]

Hi all,

Some background for the subsequent question.

We are working on a system for a targeted delivery of aerosolized drugs in to the lungs.
The general principle of how the system operates is by releasing a bolus of the aerosolized liquid infused with magnetic particles (Fe3O4 - magnetite) in to the respiratory tract, bringing it to a specific location and then using a magnet, the bolus is deposited.

Now we are trying to quantify the amount of deposition from the bolus, and to do so we have tried the next method:
Using regular table salt (NaCl) mixed in the solution of the liquid and the magnetic particles, to try and measure the increase in conductivity of DI water (after rinsing the deposition area with that DI water) compared to a base line sample of clean DI water.
So far we had inconsistent and seemingly random results.
To measure the conductivity we used this device.

So my question is basically if anyone have any ideas on how to measure the deposition, preferebly using substances that are "safe" (e.g. salt, magnetite, fluorescein...) and can be measured using "basic" equipment that can be found in a typical chemistry lab (we access to a medical center labs and in an academic institute).

 

[ashtree]

Obviously you are dealing with very small quantities of NaCl in solution.
Is a measurement sensitivity of 0.01us/cm low enough to detect the quantities you are dealing with?

Regards
Ashtree
"Any water can be made potable if you filter it through enough money"

 

[Compositepro]

I am not sure how well your idea will work with the few details that you provided. I have never heard of such a magnetic technique. That may be because it doesn't work. Static electrical charge is commonly used to enhance deposition, as in powder coating. You could, for example, give your particles a negative charge. They would then repel each other, thus preventing agglomeration of the particles. Charged particles are attracted to ground or to oppositely charged surfaces. If a person inhaling your bolus were also negatively charged then the bolus would be repelled from body surfaces such as the mouth and throat. After inhalation, the body could be changed to a positive charge, and then the particles in your bolus would be attracted to the nearest body surface, the lungs. This should be fairly quantitative at getting all your particles to deposit, so I am not sure how important the measurement would be. There would be a current created by this charge transfer that occurs when a charged particle contacts a surface, which should be measurable with great accuracy if there are no large interferences.

 

[Helepolis]

Obviously you are dealing with very small quantities of NaCl in solution.
Is a measurement sensitivity of 0.01us/cm low enough to detect the quantities you are dealing with?

It seams that there is a readout from the device i mentioned, the avg. read is almost 8 times higher than that of the DI water, but the reads are all over the place with no apparent consistency or corelation to the amount of deposited boluses and/or deposition duration.

I have never heard of such a magnetic technique

It has been tested before but with little to now success

That may be because it doesn't work

We are already way past the proof of concept in an in-vitro experiments (we can target an area as small as 30mm in length by 5mm in width with an accuracy of less than 1mm)

You could, for example, give your particles a negative charge. They would then repel each other, thus preventing agglomeration of the particles

We don't have to worry about agglomeration as we use particles coated with surfactant.

This should be fairly quantitative at getting all your particles to deposit, so I am not sure how important the measurement would be

We do have around 95-99% of the bolus deposited at the desired location but we need to quantify the deposited amount for the article.

For now we want to try and quantify the deposition using the substances that are already in the bolus (i.e SPION's-Fe3O4 and salt-NaCl) or maybe use other bio-compatible chemicals such as Fluorescein.