Dear Molly,

If I understand well, I would recommend you using fluorescence for encapsualtion measurement.

Step 1) prepare a solution of fluorescently-labelled nanoparticles and measure the fluorescence in a certain volume (this will give you fluorescence intensity/mL)

Step 2) encapsulate your fluorescently-labelled nanoparticles into your hydrogel.

Generally, you mix nanoparticles with hydrogels and then once the gel is polymerized, you add medium or buffer on the top for hydration. Release will be measured in this top buffer.

Step 3) regularly, measure the fluorescence into the supernatant (medium on top of the hydrogel). As you know the volume used to form the hydrogel, you can easily calculate the release rate over days.

For your information, we propose reagents for transfection in 3D (refer to the link below): nanoparticles of nucleic acids and reagent are formed and encapsulated into hydrogels to prepare a Gene Activated Matrix (after that, once it is polymerized, cells are added and get transfected while colonizing the gel).

Some of our collaborators have already performed this kind of measurements with nanoparticles formed of nucleic acids and 3D-FectIN transfection reagent, over 5 days and told us that more than 80% of nanoparticles were kept encapsulated into collagen hydrogel.

I hope this will help, if by chance you are interested in testing our transfection reagent, please do not hesitate to contact me via Researchgate or at [email protected]

best regards,

Cedric

http://www.ozbiosciences.com/3d-transfection/27-3d-fectin-3d-hydrogels-transfection-reagent.html

Some nanoparticles show absorbance at certain wavelengths in UV-Vis Spectrophotometry. I hope it can be used to calculate EE of nanoparticles in hydrogel against a sample containing known amount of nanoparticles. Otherwise, you can separate hydrogel (containing encapsulated nanoparticles) and measure nanoparticles remaining in supernatant. This is indirect method using folowing equation:

EE (in hydrogel) = total nanoparticles added - nanopartiles in supernatant 

Thanks  Cédric Sapet and Mubashar Rehman for your suggestions.