What is the difference between CRISPR and ZFNs (zinc finger nucleases)?

Zinc finger nucleases (ZFNs) employ customizable DNA binding domains (DBDs) that can recognize specific DNA sequences. Each ZFN contains two distinct domains: a zinc finger protein comprised of a DBD composed of two stitched together “finger” components and a DNA-cleaving nuclease domain. The combination of the DNA binding and cleaving elements produce the scissors required for genome editing in the nucleus. ZFNs can be delivered by electroporation or cell transfection.1

In contrast to CRISPR, the process of transfecting and selecting cells can be quite arduous and laborious. Also, the cost of multiple protein-DNA complex formation and recognition can be quite expensive when compared to merely injecting RNA targeted to the RISC.

1. J. Doudna and E.J. Sontheimer. “The Use of CRISPR/Cas9, ZFNs, and TALENs in Generating Site-Specific Genome Alterations,” Methods in Enzymology 2014.