Amit,

Basically release medium will based on your end application, like is it IM, IV or other use? We use PBS 7.4 for non-polymeric nano particle drug release with 2% surfactant at 36.5 deg. C in orbital shaker incubator. For small volume release medium, you need to change the release medium frequently to overcome super saturation.

Thank you,

Prakash

Did you try using phosphate buffer.. If you are doing in-vitro studies you can use simulated conditions involving 1% sodium lauryl sulfate dissolution solution.

Buffer : ethanol 80:20 for polymeric nano particles. I am not sure of same can be used for protein nano particles as well.

Thanks Pankaj for your reply. I used phosphate buffer but the release was negligible. I ve not tried using SLS and yes I am doing in vitro studies. can you suggest a reference for the protocol.

Thanks Himanshu for your suggestion. I will try it out and hope that it works for protein nanoparticles as well. Kindly suggest reference for the procedure.

If you are planning to inject nanoparticles you must to study the release rate at blood pH7.4 (PBS). U can change the ph based on where u r injecting the nanoparticles. Saturation point to be avoided by replacing fresh medium. Also u can increase volume. U can refer some of my publications. Also u can refer the articles from international journal of pharmaceutical sciences.pharmacopeias.

Lot of references online. Use agent in which your drug is soluble the most. Tween or surfactant may increase the release due to surface acting property.

As mentioned above, the release kinetics has to be studied in physiological pH especially at the site where the release is targeted to take place. If drug release is minimal at the present formulation, it is not the buffer or surfactants in the in vitro solution only that you need to focus on. You may have to modify the drug or the protein nanoparticle as well to modify the affinity of the drug in the composite so that it can easily be released. In short, the release kinetics is dependent upon the strength of drug-nanoparticle interaction, drug-nanoparticle ratio, pH, temperature, etc at which the drug has to be released.

@ Zoraida Aguilar. Take example of present situation of hydrophobic drug in which drug is not soluble in water (PBS buffer). Even if nanoparticle release drug in buffer it will be in suspended form. On sampling the solution, neither HPLC nor UV will detect drug. For detection drug need to be in solution form. In that case will you work on nanoparticle conjugation or release media composition?

For research purposes only, yes that should be done; in this case you can get details such as how fast and how much can be released in the solution used. The data gathered can be used to modify the drug to suit human physiological conditions.

For human consumption, the in-vitro solubility in the non-physiological solution will not make much sense and will not be very useful . What will be of benefit is the properties in physiological conditions at which the drug has to be released once ingested by the human consumer.

True. But PBS buffer itself do not work as a replica of human plasma or other secretions. I can understand your prospective but only after studying the release the person can work further to work on composition and conjugation.

PBS does not mimic the physiological conditions but it is a buffer so you can use it as the base to create a pH resembling what is in the human system. Also, you can dissolve salts in it as well as proteins, etc to simulate the biological fluids. Once you know how your drug-NP system behaves in this environment, you an use human plasma or serum to follow your drug release in vitro. I believe you have to start with the simplest system before you go to the complex biological systems when you do a study like this. Otherwise, you will encounter a lot of problems and issues that you may not be able to solve unless you go to the simple systems first.

If you know the chemistry of the drug and the properties of the protein nanoparticle, you can start the modification so that it is suitable for the human system. By doing this, you will eliminate the battle in finding a suitable non-physiologically relevant condition which will not be useful in the end. This should be avoided to minimize waste not only in reagents but in time and in overall expenditure.

Amit,

Basically release medium will based on your end application, like is it IM, IV or other use? We use PBS 7.4 for non-polymeric nano particle drug release with 2% surfactant at 36.5 deg. C in orbital shaker incubator. For small volume release medium, you need to change the release medium frequently to overcome super saturation.

Thank you,

Prakash

Protein-loaded formulations (5 mg) were weighed and suspended in 1mL phosphate buffered saline in 2 mL eppendrof tubes. They were then incubated at 37 °C with constant shaking. The samples were kept for specified periods of time (2, 5, 10, 15, 20, and up to 50 days, respectively) and were analyzed for protein determination.

Depend on your requirement. If you are on R&D step and want to choose the prototype for further step, you can use any medium that can solubilise the drug but if you want to mimic the condition in the body, the medium is depended on the target organ or the administration such as IV, IM, SC, or oral. If you want to characterise the final formulation, you must use the physiological medium.

Do the study with phosphate buffer, your formulation might release the drug in PBS. Even your drug is hydrophobic it can release the drug in the media. if your formulation impose in difficulty of release, go for optimization of your formulation. get of success by optimization....

Is your nanoparticle (NP)/drug system in a dispersed/suspended state ?

Solid content ?

Maybe then also use centrifugation to separate drug (supernatant) from NP (pellet). You can get

-> Loaded amount

-> Released amount

My NP is in dispersed state in phosphate buffer

What happens upon centrifugation ?

Phase separation into (solid/dense) pellet and clear supernatant ?

what about centrifugation, decanting supernatant, replacing supernatant by release medium and checking supernatant by e.g. UV-VIS for your drug conc.

All this repeatedly for several time points.

Yes, that's true, but what would be the releasing medium as the drug is hydrophobic and it will tend to remain inside the nanocarrier.

Thanks Martin.

What is your application ?

What would be the relevant bioenvironment (aqueous medium, soft/hard tissue) ?

At the initial stage, the application would be to deliver the drug to a cancer cell, in vitro.

Instead of buffer make use of simulated gastro-intestinal fluids in presence or absence of enzymes

Check the solubility of your drug in aqueous solution of surfactant (like SLS). You can even use buffered solution with 1-2% w/v SLS. What are you intending to suspend your particles in? I mean dialysis bag /franz diffusion cell/centrifugation?

I faced a similar problem with aromatic hydrophobic drug, which was sticking to the polystyrene tube used for release study. I could not detect the drug with UV, although I knew it was released from the dialysis bag. I could resolve it by using a glass vial instead of plastic tube. People use surfactants like Tween 80, Span, some people use simple glucose. You can try using some surfactants.

I suggest the use of surfactants known as soy lecithin which is biodegradable. The results can be interesting

Thanks Mario

You're welcome. aiming to facilitate the solubilization, you may dilute the surfactant in solution of acetone and ethanol in the ratio of 60:40 and heat to 60 degrees. good luck!

The cumulative release of hydrophobic drug from the nanoparticles can be studied by using activated cellophane or the dialysis membrane. Regarding media for the same, along with buffer, any good surfactant like SLS in the concentration of 1-3 % may be added to make the released drug soluble.

I faced a similar problem during my release experiments. However, to set up a calbirtion curve is difficult for hydrophobic drugs. I carried out in vitro release study SGF with %0.2 SLS. I obtained a controlled release profile. But in this case, does SLS (which is an anionic surfactant) interact with polycationic chitosan and increase turbidity?

it will certainly complex. You should check this effect without the drug as blank.

Hi, I'm having the same problem. My drug couldn't dissolve in PBS 7.4. The highest solubility of my drug in PBS 7.4 + 30% Ethanol is only 3.7ug/ml. So I plan to increase ethanol to be 50%. Is it posible to add more Ethanol in the buffer for drug release study?