I'm working to make PEG-PLGA nanoparticles for the sustained release of hypertensive drugs, and I'd like to calculate the % yield of my formation process, as well as the drug loading characteristics of my nanoparticles. To do this I am lyophilizing my nanoparticles to create a dry powder for these tests. Before lyophilizing, I am adding sucrose to my nanoparticle solution as a cyroprotectant. What I am wondering is how to differentiate between nanoparticles and sucrose at the end of the lyophilization process? Can you just assume that 100% of the sucrose is still there and just subtract the initial sucrose from the final product to get the nanoparticle weight? If I weigh out 10 mg of the final product, how can I tell what percentage of this weight is from the sugar itself? Please let me know how you've handled this problem in your research.
If you just want to weigh the plga that produced your particles you do not need to add a cryoprotectant. The cryoprotectant is used to preserve the shape of the nanoparticles if you are planning to see them in an electronic microscope. Sucrose is not volatile so you can also do what you are saying about subtracting the added sugar. The problem that I envisioned in this scenario is that the weight of polymer will be small compared to that of the sugar.
Omar Gonzalez-Ortega Thank you for your response. It would be very helpful if you could clarify your response. From the research I've done, it seems that the addition of a cryoprotectant is essential to preserve the characteristics of the nanoparticles (size, zeta potential, and drug release). I need to know the weight of the nanoparticles without compromising the characteristics of the nanoparticles. Do you have any suggestions?
To determine the weigh of PLGA do not add cryoprotectant, prepare two same batches; one for weight determination and one for whatever you want to pursue.
On the other hand, once you dry the sample even under the presence of a cryoprotectant you will end up with microparticles (lumps of the initial nanoparticles) and it will be virtually impossible to resuspend the dried material and recover your initial nanoparticles. This is a common mistake in the community. Anyway you do not have to believe me. Compare size, zeta potential and drug release of freshly prepared and reconstituted particles. Even if you are using PEG to impart steric stability.
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