Gold nanorods for paper-based genetic assays

Owing to their unique photophysical properties and ease of synthesis and functionalization, gold nanoparticles represent an excellent choice to develop colorimetric paper-based biosensors. Here, we selected anisotropic gold nanorods for their outstanding multiplexability and intrinsic brightness with respect to usual gold nanospheres. In particular, we compared two prominent strategies of functionalization with oligonucleotides to detect a specific DNA target, i.e. direct thiolation with a mercapto-probe, or amidation with an amino-probe in association with a carboxy-cross-linker. We found that the former provides much more consistent results, at the expense of greater complexity.