In vivo imaging of fluorescent single-walled carbon nanotubes within C. elegans nematodes in the near-infrared window

Abstract

Caenorhabditis elegans ( C. elegans) nematodes serve as a model organism for eukaryotes, especially due to their genetic similarity. Although they have many advantages like their small size and transparency, their autofluorescence in the entire visible wavelength range poses a challenge for imaging and tracking fluorescent proteins or dyes using standard fluorescence microscopy. Herein, near-infrared (NIR) fluorescent single-walled carbon nanotubes (SWCNTs) are utilized for in vivo imaging within the gastrointestinal track of C. elegans . The SWCNTs are biocompatible, and do not affect the worms’ viability nor their reproduction ability. The worms do not show any autofluorescence in the NIR range, thus enabling the spectral separation between the SWCNT NIR fluorescence and the strong autofluorescence of the worm gut granules. The worms are fed with ssDNA-SWCNT which are visualized mainly in the intestine lumen. The NIR fluorescence is used in vivo to track the contraction and relaxation in the area of the pharyngeal valve at the anterior of the terminal bulb. These biocompatible, non-photobleaching, NIR fluorescent nanoparticles can advance in vivo imaging and tracking within C. elegans and other small model organisms by overcoming the signal-to-noise challenge stemming from the wide-range visible autofluorescence.

Monitoring the Activity and Inhibition of Cholinesterase Enzymes using Single-Walled Carbon Nanotube Fluorescent Sensors

“…The suspension was centrifuged twice at 16100 rcf for 90 min, where after each centrifugation step, 80% of the supernatant was collected and the rest was discarded. The resulting DNA-SWCNT concentration was measured by absorbance spectroscopy (Shimadzu UV-3600 Plus) , using an extinction coefficient of ε 632 nm = 0.036 L mg –1 cm –1 .…”

Super‐Resolution Near‐Infrared Fluorescence Microscopy of Single‐Walled Carbon Nanotubes Using Deep Learning

“…In particular, SWCNTs emit bright fluorescence in the nIR range (900-1400 nm), which does not photobleach nor blink. [17] Moreover, given proper functionalization, they are highly biocompatible, [18,19] and were successfully utilized as imaging and sensing probes in various applications such as within plants, [14,20] live cells, [21,22] animals, [23][24][25] and brain tissue, [26,27] for example, the brain extracellular space (ECS). [28] For sensing, functionalized SWCNTs can bind specific analytes such as proteins, small molecules, metal ions, or bacteria, and exhibit fluorescence modulations upon interaction, whereas for imaging, they can be easily tracked in complex biological environment owing to their nIR fluorescence.…”

“…[28] For sensing, functionalized SWCNTs can bind specific analytes such as proteins, small molecules, metal ions, or bacteria, and exhibit fluorescence modulations upon interaction, whereas for imaging, they can be easily tracked in complex biological environment owing to their nIR fluorescence. [24,[29][30][31][32][33][34] In order to fully exploit SWCNTs as optical probes for both spatial and temporal information, the nanotubes should be individually imaged, tracked, and resolved. [35] One of the challenges is the heterogeneity of SWCNT samples, stemming from the synthesis and suspension procedures, which result in a wide distribution of SWCNT lengths.…”

“…[38] Therefore, there is a growing need for improving the spatial resolution of fluorescence images of SWCNTs in the nIR in order to fully utilize their optical properties and fluorescence emission in the biological transparency window for imaging, tracking, and sensing. [24,32] In fluorescence microscopy, both the quality and resolution of the images are predominantly limited by the optics, the photophysics of molecular emitters, and the sensor technology, posing a challenge for obtaining high-resolution images. Utilizing image reconstruction methodologies in fluorescence microscopy to solve deconvolution or super-resolution problems can improve the resolution, and also offer solutions to additional problems such as image denoising, registration, stitching, and fusion.…”

Single-Walled Carbon Nanotubes as Fluorescent Probes for Monitoring the Self-Assembly and Morphology of Peptide/Polymer Hybrid Hydrogels

“…The NIR-fluorescence emission of SWCNTs depends on their close environment. , Changes in their close proximity, e.g., by analyte binding, are translated into changes in their fluorescence properties, i.e., emission wavelength shifts or fluorescence intensity changes. ,,− Thus, SWCNTs can be utilized as NIR-fluorescence sensors that do not suffer from photobleaching or blinking, allowing for long-term measurements. ,− Successful integration of SWCNTs into hydrogels while taking advantage of their fluorescence properties as analyte-specific sensors has been shown. , Several studies also demonstrated the feasibility of SWCNTs integrated into hydrogels as implantable sensor platforms , for NIR-imaging and spectroscopy in tissue. ,− …”