miRNA in serum - (Nov/01/2011 )

I'm currently working with miRNA in serum. Previously I've worked on miRNA and mRNA expression in Breast cancer using microarrays. I would like to do miRNA expression analysis in serum of breast cancer patients but I haven't found a good protocol. Has anyone used any arrays that don't cost much and work? If so, what protocol have you used? I find it hard to chose isolation protocol for the miRNA in serum as there are many different protocols.
I've tried to run expression analysis in serum using the agilent platform, but i experienced that the input of miRNA is too low and doesn't work.

Thanks for any answers.

Chen et al., 2005 and Chen et al., 2008 Nucleic Acids Research have assayed miRNA from Serum