Single-walled carbon nanotubes (SWNTs) have emerged as promising signal transduction elements for biological imaging and sensing due to their notable fluorescence in the near-infrared (NIR) region with minimal light absorbance by water or scattering by tissue.1
Recently, exciting developments in SWNT surface chemistry have shown the retention and improvement of fluorescence intensity in SWNT after covalent surface functionalization.2
These chemistries provide chemical handles for specific attachment of molecules of interest to the SWNT surface while keeping the intrinsic NIR fluorescence of the SWNT intact for bioimaging and sensing applications. However, despite their unperturbed fluorescence, it is unclear whether functionalized SWNTs retain their ability for molecular sensing, which necessitates a modulation in SWNT fluorescence provided by the molecular recognition of a surface-adsorbed polymer. We compare the photophysical properties of functionalized SWNTs to their pristine counterparts, and show SWNT optical properties remain available for sensing applications, but only for certain sensing strategies. Molecular recognition provided by surfactant and phospholipid SWNT surface coatings retain their ability to detect molecular analytes such as fibrinogen and insulin. Conversely, DNA oligonucleotide surface coatings under-perform for molecular recognition of dopamine compared to sensors constructed from pristine SWNT. Lastly, we explore the application of functionalized SWNT as dual-functional nanoparticles with both targeting and sensing capabilities. Our work establishes the potential advantages and drawbacks of covalent SWNTs functionalization, despite preservation of SWNT fluorescence, and implications for applications in molecular sensing.
(1) Bonis-OâDonnell, J. T. D.; Page, R. H.; Beyene, A. G.; Tindall, E. G.; McFarlane, I. R.; Landry, M. P. Dual Near-Infrared Two-Photon Microscopy for Deep-Tissue Dopamine Nanosensor Imaging. Adv. Funct. Mater. 2017, 27 (39), 1â10.
(2) Setaro, A.; Adeli, M.; Glaeske, M.; Przyrembel, D.; Bisswanger, T.; Gordeev, G.; Maschietto, F.; Faghani, A.; Paulus, B.; Weinelt, M.; et al. Preserving Ï-Conjugation in Covalently Functionalized Carbon Nanotubes for Optoelectronic Applications. Nat. Commun. 2017, 8, 1â7.