High sensitivity near-infrared imaging of fluorescent nanosensors

Abstract

Biochemical processes are fast and occur on small length scales, which makes them difficult to measure. Optical nanosensors based on single-wall carbon nanotubes (SWCNTs) are able to capture such dynamics. They fluoresce in the near-infrared (NIR, 850 3 1700 nm) tissue transparency window and the emission wavelength depends on their chirality. However, NIR imaging requires specialized and cooled InGaAs cameras with low resolution because the quantum yield of normal Si-based cameras rapidly decreases in the NIR. Here, we developed an efficient one-step phase separation approach to isolate monochiral (6,4)-SWCNTs (880 nm emission) from mixed SWCNT samples. It enabled us to image them in the NIR with highresolution standard Si-based cameras (>50 x more pixels). (6,4)-SWCNTs modified with (GT)10-ssDNA become highly sensitive for the important neurotransmitter dopamine. These sensors are 1.7-fold brighter and 7.5 x more sensitive and allow fast imaging (< 50 ms). They enable high-resolution imaging of dopamine release from cells. Thus, the assembly of biosensors from (6,4)-SWCNTs combines the advantages of nanosensors working in the NIR with the sensitivity of (Si-based) cameras and enables broad usage of these nanomaterials.

Near infrared fluorescence lifetime imaging of biomolecules with carbon nanotubes

“…Here, the SWCNTs are used as a sensor paint that covers both, glass surface between the cells as well as the cells itself 42 instead of placing the sensor beneath the cells as it was state of the art 46,59,61 . To find out if FLIM with SWCNT-based sensors is possible in a complex environment in cell medium surrounded by cells, first a more general approach was tested.…”

“…Detection of dopamine and other neurotransmitters with a high spatiotemporal resolution is therefore a major but challenging goal to gain deeper insights in intercellular communication. In contrast to other approaches such as electrochemical or genetically encoded sensors [50][51][52][53][54][55][56][57][58] imaging of neurotransmitter with SWCNT-based sensors offers very high spatial and temporal resolution 42,46,[59][60][61] .…”

“…MD simulations revealed that an interaction between polar groups from dopamine and the phosphate backbone of the DNA moves the backbone closer to the SWCNT resulting in an altered electrostatic potential at the SWCNT surface 59,62,63 . Coating of SWCNTs with guanine (G) containing ssDNA sequences such as (GT) x -SWCNTs showed the best results and these sensors were used for biological studies 42,59,61 . Additional characterization of (GT) x -SWCNTs rendered a length of 10 bases ((GT) 10 ) to be most selective and sensitive 44 .…”

Ratiometric imaging of catecholamine neurotransmitters with nanosensors

“…This makes them uniquely suited for biological applications and they therefore serve as versatile building blocks for biosensors. [21][22][23][24][25][26][27] However, due to the high hydrophobicity of SWCNTs, hydrophilic surface coatings are required to use them in aqueous environments. Surfactants or larger (bio)polymers that either form micelles around the SWCNTs or exhibit π-π interactions are suitable for this purpose.…”