Fig. 4.

Hydrogel aptasensor for the detection of AIV H5N1: (a) chemical modification of the QCM surface with a nanoporous gold film; (b) QCM electrode before (I) and after (II) the surface modification; (c) scanning electron microscopy (SEM) image of an AIV H5N1 bound to the nanowell structure on the crystal surface; (d) frequency shifts of the aptasensor to 2 HAU of different AIV subtypes; (e) frequency responses to tracheal swab samples spiked with 2^-4 to 2⁰ HAU of AIV H5N1. Reprinted with permission from Wang et al. (2017). (For interpretation of the references to colour in this figure legend, the reader is referred to the Web version of this article.)