I made PLGA drug loaded nanoparticles (without any surfactants). Before lyophilization, I put them in -70C for a day or more. When I take them out from the deep freezer and let them thaw, they are aggregated. Does cryoprotectant help me? How much is needed? Which kinds of protectants are preferred? How can I know the used protectant is the suitable one? Is it necessary to omit the protectant before antibacterial tests?
Yes, cryoprotectants help you, but the adding of this affects the original composition of your particles, and you must considerate that. I see other option, liquid nitrogen to freeze it, and with this, maybe the structure of your particles not change. on your other question, glycerol is a useful cryoprotectant.
Jonathan Diaz
I mainly use freeze drying as a way to remove my solvent which is water. In this case liquid nitrogen and glycerol seem not suitable. Regarding to some articles, I am going to test some monosaccharides as cryoprotectant. I have some problems with the monosaccharides' type and concentrations.
Check the articles in the area of food chemistry, especially freeze-preservation, there are several different cryoprotectants as monosaccharides are used, and perhaps you have other options
Yes, cryoprotectants wil help you, but the original composition of NPs changes.
I tried with 2.0 wt% sucrose or 2.0 wt% threalose and the system works well..
Paolo Verderio
How do you calculate 2 wt%? Is it 2 wt% of the drug added to prepare nanoparticles, not considering the amount of drug which is not loaded on nanoparticles? What is the normal percentage range for cryoprotectants? (1-20%?)
NO 2 wt% is the amount of Sucrose/Threalose in the solution used as cryoprotectant.
It does not depend on the NPs conc.
So, How much should it be added to nanoparticle? Is there any ratio?
It was just an accident but it made me think that maybe the aggregation effect the freeze dried product.
How should I know is it necessary to add a cryoprotectant or not? I should determine the particle size before and after freeze drying process? Are there any other methods?
30%-40% lactose will do the job. no aggregation. the size of the liposomes does not change dry fo 6 months. finding the right formulation of the NP helps.
Its about percentage of cryoprtotectant. If it says 5% w/v does that mean for drying 20 ml formulation containing whatever the drug amount or lipid concentration 1gm of let say mannitol to be added?
may be helpful:
http://www.sciencedirect.com/science/article/pii/S0927776514001350
you can use mannitol (5 - 15%), glucose, sucrose, trehalose, PEG 2000, or PEG 10,000) as cryoprotectant , this lead to stabilization and prevention particles from degradation during freeze-drying and storage.
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