If you gave more information on the material used and the size distribution, more suggestions could be made. For example, for monodisperse gold nanoparticles UV-vis spectroscopy is a very easy and convenient way to determine their concentration. If there is anything that absorbs light in your particles, this may still be the easiest method.

I'd recommend high performance liquid chromatography with fluorescence detection to determine the concentration.

normally, the particle efficiency can be achieved by removing the supernatant. The sediment should be washed out with water for several times. The resulting suspension could be freeze-dried and the dry particle powder would be weighted.

Another way would be the dialysis approach. This would remove the materials that is not fabricated in the nanoparticles. However, if the target compound is encapsulated in the nanoparticles. This method is not good because your drug would be released during the dialysis process.

It should be noticed that before the freeze-drying process, the glass tubes, instead of plastic one, should be used to contain the particles because of the density concern.

You can go for cooling centrifugation of your formulation remove out the supernatant wash the filtrate with double distilled water and lyophilize it and get the solid np and weigh it.

Dear Ashour, thank you for the suggestions. But It would be great if you please elaborate it. I am not getting the way out.

Dear Mathias, I have not synthesized any metallic NPs. I have formulated a Nano-drug. Which I have primarily coated with PLGA and also stabilized with PVA & Poly-L-Lysine. Please feel free to ask me if you have any query.

Thank you for suggestions.

Regards

Dear Enis, I want to determine the concentration of the NPs. I am not focusing on the individual concentration of the components in the NPs. I need a concentration of the stock solution so that I can treat the cells with increasing dose and can check the viability and other aspects.

I don't know in which type nano particles you are working? For determination of metallic nano particle concentration u can do AAS or ICP-MS.

@ Swarup, currently I am not working on metallic NPs. Previous I have done that. Now I am focusing on drug-formulated NPs and want some help regarding that.

If you have drug-formulated nanoparticles, the best way is to centrifuge and wash to get rid of non-encapsulated drug and then freeze-dry to get the weight. Make a stock of the drug-loaded nanoparticles and then use dilutions to treat the cells. For the exact amount of drug encapsulated in the NPs, make a standard curve of drug absorption at various concentrations, calculate extinction co-efficient for drug, and then correlate to the absorbance of your formulated drug at a specific concentration in solution. This will give you the exact amount of encapsulated drug per gram of the formulated drug. I think it will help you.

Thanks Samina. You answer seems much helpful and convincing. I will go for it. I will send you if i get any further query regarding that.

Thanks & regards

Shakti

I understand your question as : how do I get to know the actual number of NPs per mL ? Is that correct ? If it's the case, I don't know the way to know the exact answer. But you can have a good estimation knowing your NPs recovery field and the mean diameter. You will find such an example in the SI part of one of our publications (Hydrogels Incorporating GdDOTA: Towards Highly Efficient Dual T1/T2 MRI Contrast Agents, Courant T et al., Angew, 2012, 51(36), 9119-22). Although we did not 'invent' the method, we applied it with success in a variety of situations and actual physical properties of NPs backed the calculations up quite nicely. Hope it will be useful.

Please collect the nanoparticles by centrifugation/freeze drying.Dissolve the particles in an organic solvent which dissolves both drug and polymer. Measure the absorbance by uv spectrophotometry and calculate the drug content from absorbance of pure drug solution in the same solvent.

There are two methods.

1.Direct method and

2. Indirect Method

Indirect Method involves estimation of free drug in supernatant whereas direct method involves lysis of dried Nanoparticles followed by estimation by reliable analytical technique.

Sorry, I read your previous comment and your question is different.

You may go for GPC (Gel Permeation Chrometography) or I think there is some link of PDI (Poly Dispersity Index) and dilution factor with concentration of nanoparticles; I guess.

Why dont you go for dissolution method and then UV? I think you can get the drug concentration in an easy why.

You can do this on small scale on roller method as well using 25mg NPs in 25ml dissolution medium per tube.

Dear Bhavin,

Thank you for the suggestions. It would be much helpful if you could provide any paper related to that.

Regards

Dear Syed,

Please elaborate the description regarding the method. Thank you.

Regards

Which one? Dissolution method or the roller mixer method? (The roller mixer was designed by ourselves in the lab. and I can send you the requirements and proceedure if you need.

Dear Syed,

Please provide protocol for roller mixer method.

Thanks & regards

Shakti

Dear Shakti, Please send your e-mail ID so that I can mail you the method along with the picture of using roller mixer inside an incubator(for the required tempt. of 37o C).

http://www.nbtc.cornell.edu/facilities/Countrate.pdf

http://www.nbtc.cornell.edu/facilities/Countrate.pdf

I would also like to suggest you one simple method on the basis of my logic.

I want also your opinion for the same.

First measure the volume (X ml) of nano-particulate suspension. Then, dry nano-particulate suspension into powder form using freeze/spray drying and measure the powder weight. Make up the volume by re-disperse powder again up to X ml and find out concentration (%Wt/ Volume).

Dose it work for you?

Dear Syed,

Its [email protected]. Please send me the details.

Regards

Shakti

Dear Shakti, Please find the details in your mail box. Regards

Please do follow the Bhavin Patel's method as well. It will work as well.

Dear Syed,

Thanks for the protocol. I found it.

Regards

Shakti

You are welcome.