Near‐Infrared Fluorescence Lifetime Imaging of Biomolecules with Carbon Nanotubes**

Abstract

Single-walled carbon nanotubes (SWCNTs) are versatile near infrared (NIR) fluorescent building blocks for biosensors. Their surface is chemically tailored to respond to analytes by a change in fluorescence. However, intensity-based signals are easily affected by external factors such as sample movements. Here, we demonstrate fluorescence lifetime imaging microscopy (FLIM) of SWCNT-based sensors in the NIR. We tailor a confocal laser scanning microscope (CLSM) for NIR signals (> 800 nm) and employ time correlated single photon counting of (GT) 10 -DNA functionalized SWCNTs. They act as sensors for the important neurotransmitter dopamine. Their fluorescence lifetime (> 900 nm) decays biexponentially and the longer lifetime component (370 ps) increases by up to 25 % with dopamine concentration. These sensors serve as paint to cover cells and report extracellular dopamine in 3D via FLIM. Therefore, we demonstrate the potential of fluorescence lifetime as a readout of SWCNT-based NIR sensors.

Wide-field fluorescence lifetime imaging of neuron spiking and subthreshold activity in vivo

“…In voltage imaging, lifetime will enable improved measurement of FRET-opsin (3, 7), hybrid FRET (6), and dye indicators (8). We also anticipate application to imaging calcium (27), neurotransmitters (28,29), and cyclic adenosine monophosphate (30). Use of GEVIs in vivo is often accompanied by a large fluorescence background that results from protein expression outside the cellular membrane (31) or leaky gene expression from nontargeted cells (32).…”

Carbon Nanomaterial Fluorescent Probes and Their Biological Applications

“…Also a consequence of their electronic bandgap structure, certain SWCNT chiralities exhibit photoluminescence by absorbing light in the NIR-I and emitting in the NIR-II region. This makes them excellent reagents for biological imaging , and scaffolds for biosensing applications. , SWCNTs have also been employed as photoinduced drug delivery vessels, , gene and protein delivery vehicles, , nanopores, , adjuvant vaccines, and are used in tissue engineering applications. − …”

Nanocrystals for Deep-Tissue In Vivo Luminescence Imaging in the Near-Infrared Region

“…Time-resolved imaging is a crucial technique for discerning fluorescence information in the time domain. ,− It relies on the fluorescence lifetime of fluorescent probes, which represents the average duration during which excited-state photons remain in the excited state before returning to the ground state. − By employing time-gating technology as a temporal filter, the long-lifetime emission (ranging from microseconds to milliseconds) from the probes is captured following the reduction of autofluorescence or scattered light (0.1–5 ns). − Time-resolved imaging greatly enhances imaging sensitivity and SNR by effectively mitigating the impact of absorption, scattering, and background autofluorescence induced by excitation light. − This technique has the potential to decrease false-positive and false-negative signals in biological detection. The SNR increases with extended acquisition time, reaching its peak after the complete decay of autofluorescence.…”