“…In many applications, surface modification of the waveguiding structures is essential to provide molecular recognition interfaces that attract analyte molecules (e.g., proteins, peptides) to the waveguide surface (Figure 6). Depending on the material properties, such bio(organic) modifications take advantage of various binding motifs, including self-assembled monolayers, metal ion affinity and chelation mechanisms, amine coupling, antibody coupling, biotin-avidin linking, and his-tag coupling, thus enabling device technologies suitable for biodiagnostics (108)(109)(110)(111). Ideally, DNA-and aptamer-based functionalization facilitating selective yet label-free binding with high affinity and selectivity have been shown, for example, for bacterial lysates (112) (Figure 7).…”