Dear Zenande,

this is a very interesting technical question. Indeed, when gold nanoparticles are intended to be used in for in vivo biomedical applications they must be sterile. In this context please have a look at the following very useful article in which different sterilization methods are reviewed

Sterilization Matters: Consequences of Different Sterilization Techniques on Gold Nanoparticle

Article Sterilization Matters: Consequences of Different Sterilizati...

Fortunately this paper has been posted by the authors as public full text on RG. Thus you can freely access it and download it as pdf file. I hope it helps answering your question.

Good luck with your research and best wishes, Frank Edelmann

Filteration need to be based on the size you require, there is a limit for the maximum and minimum size for use in in vivo condition as well as the organ and route of administration! The sterility has been discussed by Frank Edelman. If you put more details, further suggestions may come.

Zenande Pali

Pay attention to my recommendations, which can be followed by following your question.

1.After filtration, you get clear solutions. If there is no wine-red color, then perhaps there are already no nanoparticles with adsorbed organic dye.

2. The adsorbed organic matter from plants is sometimes

have bactericidal properties. Nanoparticles too. You need to check this and it may not be necessary to sterilize your material.

3. Instead of filtration, centrifugation can be used to separate the nanoparticles from the dispersion medium. This is a softer separation method than filtering.

Thank you so much for all your input. I highly appreciate it!