Chem 8157

Here is a question/comment for Eric and the rest of the class:

1. The paper describes that this method is label-free? Is this correct?

The authors never make clear what their definition of label-free is. Presumably, they refer to this method as being label free in that there is no covalently attached label during hybridization of the target DNA to the probe oligonucleotide. If this is their definition, then this method is indeed label-free. However, in order to achieve detection, the method requires hybridization of the ligase probe with the DNA that is attached to the gold nanoparticle. In that respect, this method is not label-free. It seems that the authors should be more careful in either clearly defining what they call label-free or choose another phrase for selling their method.

I think in this paper the detection is achieved by hybridization adsorption of gold nanoparticle modified with ssDNA that are complementary to the ligation probe sequence. There is no additional modify to the target DNA, like hybridization with molecular beacon or dye. These methods all modify target DNA. Compared with SPRI, they are not label free.