Before you decide on a method I'd turn you toward Burgos et al. Identification of extracellular miRNA in human cerebrospinal fluid by next-generation sequencing. That paper is a very useful tool.

thanks for your answer

Mr.Jeffrey Shelton 

i already read the mentioned article and the total RNA yield will be not enough for doing NGS because i called the company and they said it should be 1ug/ul of total RNA because they didn't handle low concentration of total RNA before.

Mr.Emanuel A Devers

i asked the company (Macrogen ) but they said should be 1ug/ul so i am trying a way to maximize the total RNA yield.

so i collect 1ml of serum and pass it through Qiagen kit for microrna but the total RNA yield was low around 64ng/ul and low ratio around 1.4.

thanks for your help.

Hello Adham,

I am currently sequencing miRNAs using the small RNA Tru-Seq illumina preparation kit. I start from a non-cellular population where the contamination by other types of RNA is not common.

Long time ago I did serum miRNA purification and I remember that the yield was very low, start from bigger volumes or you will not have enough for anything. I would also recommend to use Ribogreen as quantification method.

This said, I have prepared my libraries starting with 10ng of RNA in 5uL and I haven't had any problems. So you have a general idea, my yield after the library preparation and size selection was half the one a colleague was doing in parallel starting with 1ug of total cell RNA

hello Jennifer

thanks for your help. 

i will try to require Ribogreen to quantufie RNA isolated from serum. I have one question is it easy to construct library using small RNA Tru-Seq illumina preparation kit? because I didn't do before and how about cost of it?