What could cause autologous serum eye drops to precipitate? A patient has been using the drops for years due to dry eye symtpoms. Recently, three of four production series tended to precipitate when being thawed. Cold agglutinines, cryoglobulines, bacterial contamination was ruled out by lab examinations. FVIII (as one of the factors in cryoprecipitate) was only slightly elevated to 180% (upper norm limit is 150% at our lab). Electrophoresis of serum proteins was normal...any suggestions?
You may want to check whether there have been any recent changes in the solvents used in the drops. Good luck!
you might need to think of addition cryoprotectants before freezing the eye drops to avoid serum protein unfolding.
Do you store the autologous serum in the -20degrees C ? How long do you keep the serum for?
I have only experience of one case and it is collected every 2 weeks, and used over one month.
We have not seen this precipitation.
Dear all,
thank you for your answers! We indeed store the serum frozen at -40°C, but I do not know at what cold the user stores them; I would guess taht a normal household fridge won´t go deeper than -20°C!
Dear Hamdy, what cryoprotectant would you use? Dextrane, HES? DMSO surely is out of the question, I could not think of a way it could work?
Dear Ivayla, what solvents are you referring to? We only freeze pure autologous serum.
trehalose, mannitol, sorbitol are among cryoprotectants you could safely use for that particular application.
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