Dear Maryam, miRNA ABC kits provided by LifeTechnologies (cat # 4473087, cat # 4473088) and miRNeasy Serum/Plasma Kit (cat # 217184) by QIAGEN are considered to be the best solution for miRs isolation. Also, cheap TRIZOL reagent is recommended by some authors (attached article). The year of the article is 2010, but still useful. Good luck ;))
1. Total RNA will be isolated from serum or plasma ( microRNA not easy to isolate because it has 13- 25 nt).(miRneasy mini kit Qaigen)
2.Carrrier RNA (MS2 RNA, Roche) will be used to isolate RNA.
3. Synthetic miR (cel-miR-39, Qaigen), till date there is no endogenous control for serum microRNA , so we have to use known concentration synthetic microRNA.
4. Spike in control(Exiqon) , while converting cDNA you have to add spike in control , to check cDNA efficiency.
5. microRNA expression, by using Real Time PCR( Sybr green or taqman probe).
I will suggest you to use miRNeasy mini kit or miRNeasy serum plasma kit.
Both kits are almost similar. if you have high budget you can use plasma kit, if you have less money than use miRNeasy mini kit with some modification which is adopted to isolate miRNAs from liquid sample.
Furthermore I would like to add when I start to work with extracellular miRNAs, serum and plasma kits were not available and I used miRNeasy mini kit. at the end of my experiment this kit was available in the market and one of my colleagues start to use that kit. and I found there was no visible differences with tow kits.
for more info please do do not hesitate to contact me
I'm Damariz Rivero. I'm working at Florence University (Italy).I read your answer to Maryam's question. I'm interested to purify miRNAs from liquid samples using the mirneasy mini kit. Could you please tell me the modifications to the protocol that you performed?