The
omnipresence of salts in biofluids creates a pervasive challenge
in designing sensors suitable for in vivo applications. Fluctuations
in ion concentrations have been shown to affect the sensitivity and
selectivity of optical sensors based on single-walled carbon nanotubes
wrapped with single-stranded DNA (ssDNA–SWCNTs). We herein
observe fluorescence wavelength shifting for ssDNA–SWCNT-based
optical sensors in the presence of divalent cations at concentrations
above 3.5 mM. In contrast, no shifting was observed for concentrations
up to 350 mM for sensors bioengineered with increased rigidity using
xeno nucleic acids (XNAs). Transient fluorescence measurements reveal
distinct optical transitions for ssDNA- and XNA-based wrappings during
ion-induced conformation changes, with XNA-based sensors showing increased
permanence in conformational and signal stability. This demonstration
introduces synthetic biology as a complementary means for enhancing
nanotube optoelectronic behavior, unlocking previously unexplored
possibilities for developing nanobioengineered sensors with augmented
capabilities