Im functionalising gold nanoparticles with thiolated DNA, this is done using excess DNA in solution, it is critical that once the procedure is complete any remaining DNA is completely removed. Due to the size of the gold nanoparticles I am currently centrifuging at 100000G to pellet and resuspend in ultra purified water. However I am concerned: what if by using this level of RCF I am also pelleting the DNA and the purification method is completely ineffective.
Thanks for your help.
I don't believe you can pellet DNA in solution by ultracentrifugation. Anything not bound to the particles will likely remain in the supernatant. Still, is it really necessary to spin at such high g force?
You shouldn't need this RCF to pellet your microparticles. Just a hunch, but they are likely not aggregating in a stable pellet. What size are your gold particles? Have you considered ultrafiltration or dialysis?
Carl.
Hi
The nanoparticles are stable - this is can directly observed due the distinct ruby red color they display - I have aggregated lots of gold nanoparticles... They at best turn purple and at worst turn into black specks at the bottom of a centrifuge tube.
Nanopartz suggests such a high RCF (They describe RPM which isnt so helpful however (https://www.nanopartz.com/gold-nanoparticles-properties-centrifuge-speeds.asp). I am centrifuging 5nm and 3.5 nnm particles. They are likely to come down at a somewhat lower RCF due to the many DNA strands attached to them (It is these attached DNA strands which give the gold nanoparticles there incredible resistance to high RCF). However even at this level of RCF there is still a lot of waste when resuspending.
I am not familiar with either of the techniques you mention but will look them up. Thanks for your advice!
http://www.cytodiagnostics.com/store/pc/Gold-Nanoparticle-Handling-and-Storage-d7.htm
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