Strategies for the surface biofunctionalization of sulfur-based chalcogenide infrared optical glasses

Abstract

Effective surface functionalization plays a critical role in the selectivity and sensitivity of sensing devices. While chalcogenide glasses (ChG) have received a lot of attention as promising optical materials for mid-IR biosensors, there have been just a few reported instances of their successful (bio)functionalization. In the present work, we explore three different approaches for the grafting of heterobifunctional derivatives on Ge25Sb10S65 substrates. One of these approaches consisted in the use of traditional silane chemistry to functionalize hydroxyl moieties on the ChG, while the other two are novel strategies based on the potential reactivity of maleimide and cyclooctyne derivatives for sulfhydryl moieties at the surface of the inorganic glass matrix. Using these approaches, biotinylated surfaces were prepared and the selective grafting of a fluorescent-labeled protein was then validated via IR spectroscopy, AFM and fluorescence. Our results showed that successful biofunctionalization of Ge-Sb-S ChG was achieved by all three methods. Moreover, the functionalization process can be easily adapted for substrates with any type of geometry and for the grafting of different molecules at the surface, paving the way for the future development of infrared optical sensing systems exhibiting surface bio selectivity.