Single-walled carbon nanotubes as optical probes for bio-sensing and imaging

Abstract

The unique physical properties of single-wall carbon nanotubes (SWCNTs) have been exploited in novel applications in various fields including electronics and life sciences. Their photoluminescence in the near-infrared (NIR) range, where optical interference from biological tissues is minimum, has rendered them particularly attractive as optical probes in biological environments. Herein we review the use of the SWCNT NIR emission in bio-sensing and imaging.To interface the insoluble carbon nanotubes with aqueous biological environment, biomaterials and organic polymers have been widely used for non-covalently functionalizing SWCNTs. Such functionalization minimizes the toxicity of carbon nanotubes in biological and physiological environments, while maintaining its optical properties. SWCNTs have been demonstrated as both in vitro and in vivo optical sensors, targeting biologically important molecules, such as neurotransmitters and cell signaling molecules. For optical imaging, functionalized SWCNTs were used as NIR contrast agents for probing cellular processes and imaging plants and small animals.We also discuss emerging SWCNT-based super-resolution schemes. We conclude that SWCNTs are promising optical materials for basic life science research, biomedical diagnostics, and therapeutics.

Fluorescent Single-Walled Carbon Nanotubes for Protein Detection

“…The non-photobleaching, non-blinking fluorescent emission of SWCNTs plays a key role in rendering them optical sensors, enabling in situ, label-free, real-time detection with both spatial and temporal resolution [89,113,115]. Recent studies have demonstrated the detection of proteins using various approaches for surface functionalization, including natural substrates [53,121,125] and synthetic polymers [89,129,145], with the potential to enable long-term continuous monitoring of important biomarkers or to replace costly and time-consuming laboratory testing [173]. We have highlighted the advantages of SWCNTs for in-vivo and in-vitro biomedical applications such as drug delivery, imaging, and sensing, focusing on protein recognition.…”

Amphiphilic anthanthrene trimers that exfoliate graphite and individualize single wall carbon nanotubes

“…Focusing on the lowest energy absorption of 1, 1/ SWCNT formation results in maxima at 448 and 474 nm. S 11 absorptions of SWCNTs, that is, (6,5), (7,5), and (7,6) at 1013, 1053, and 1157 nm, respectively, shift hypsochromically to 997, 1046, and 1142 nm in the presence of 1. Monitoring the fluorescence changes during 1/SWCNT formation in ethanol leads to the same results as in DMF with stronger contributions of excimer-like 1.…”

“…S5 † shows a comparison of 1/SWCNT and pristine SWCNT dispersions. Focusing on the S 11 transitions in DMF, the absorption maxima of (6,5), (7,5), and (7,6) at 1012, 1054, and 1160 nm, 43 respectively, in pristine SWCNTs are hypsochromically shifted in the respective 1/SWCNTs to 999, 1050, and 1150 nm. Hypsochromic shifting of SWCNT absorptions stands for effectively debundled or even individualized SWCNTs.…”

“…Both nanographene (NG) and single wall carbon nanotubes (SWCNT) are emerging nanomaterials in applications such as molecular electronics, catalysis, solar cells, or as probes for optical imaging of biomolecules. [1][2][3][4][5] Despite rapid progress in the chemical functionalization of NGs and SWCNTs, preserving the spectroscopic and transport characteristics of the pristine materials in nanostructured devices with advanced functions, still remains one of the greatest challenges in the field. For example, NG and SWCNT functionalization has been realized by means of forming covalent bonds or employing non-covalent interactions with planar, π-conjugated chromophores and polymers.…”

Unsupervised Idealization of Nano-Electronic Sensors Recordings with Concept Drifts: A Compressive Feature Learning Approach for Non-Stationary Single-Molecule Data Analysis

“…More recently, another approach has been emerging based on single-molecule field-effect transistors (smFETs), in which an individual molecule is immobilized on a nanoscale electrical circuit, such as a carbon nanotube (6)(7)(8)(9)(10)(11)(12) or silicon nanowire (13)(14)(15)(16). By recording fluctuations in the electrical conductance of such circuits, studies have reported the realtime monitoring of transitions between different conformational states, such as hybridization (17)(18)(19)(20), folding events in nucleic acids (17,21), enzymatic catalysis with a ultra-high sensitivity and specificity (22,23), and also other applications in biology and medicine, such as imaging (24,25) and drug delivery (26,27) to cancer and brain. Detecting and modeling the kinetics and thermodynamics of such molecular interactions from smFET recordings require robust data analysis tools that can handle challenging signal specificities: 1) the stochastic nature of the biomolecular system, 2) the possible non-stationarity of the molecular dynamics of the reaction system, such as changes between transient and steady-state conformations, 3) the multi-source composition of the sensor response, aggregating all the contributions from the biochemical system with those of the measurement medium and the sensor components into a single output, 4) the mixed noises (AWGN, flicker, and impulse) characteristic of FET devices, 5) the sensor baseline drift that can occur during long acquisitions, and 6) the sizable amount of data generated by such recordings, all together resulting in complex time series to idealize into a state trajectory.…”