Well, just from the G scholar: http://pubs.acs.org/doi/abs/10.1021/ja302551p

Don't know how specific it is though...

Thank Vitaliy, the paper looks very interesting! Jayden, let us know if this aptamer doesn't suit your exact purposes - we can select a custom one for a very reasonable price. www.basepairbio.com

Thanks Vitaliy; interesting paper, but kind of the reverse of what I was hoping to achieve (which is a targeting moiety on the nanoparticle, rather than a recognition site anchored to the cell). And as you say, the attachment of the aptamer isn't necessarily cell specific.