Multimodal optical sensing and analyte specificity using single-walled carbon nanotubes

Abstract

Nanoscale sensing elements offer promise for single-molecule analyte detection in physically or biologically constrained environments. Single-walled carbon nanotubes have several advantages when used as optical sensors, such as photostable near-infrared emission for prolonged detection through biological media and single-molecule sensitivity. Molecular adsorption can be transduced into an optical signal by perturbing the electronic structure of the nanotubes. Here, we show that a pair of single-walled nanotubes provides at least four modes that can be modulated to uniquely fingerprint agents by the degree to which they alter either the emission band intensity or wavelength. We validate this identification method in vitro by demonstrating the detection of six genotoxic analytes, including chemotherapeutic drugs and reactive oxygen species, which are spectroscopically differentiated into four distinct classes, and also demonstrate single-molecule sensitivity in detecting hydrogen peroxide. Finally, we detect and identify these analytes in real time within live 3T3 cells, demonstrating multiplexed optical detection from a nanoscale biosensor and the first label-free tool to optically discriminate between genotoxins.

Peptide secondary structure modulates single-walled carbon nanotube fluorescence as a chaperone sensor for nitroaromatics

“…The analytes generate differentiable fingerprints via distinct spectral signatures and unique responses of several SWNT ðn;mÞ species in a manner analogous to what we have shown for genotoxins (9). Principal components analysis, performed on the detection data and collected from eight different SWNT species, confirms unique signatures of the six analytes, denoted by their segregation into separate regions of the plot (Fig.…”

“…For such a capability to be extended to specific classes of organic molecules, chemical approaches must be developed that allow for selective molecular recognition. Stepwise quenching of SWNT PL by single-molecule adsorption events to the nanotube surface (7) has been demonstrated (8,9). Our previous findings extend this resolution to biologically important reactive oxygen species and demonstrate multiplexed detection of redox-active analytes by two optical modes, leading to species identification (9).…”

“…1A). Examples of this mechanism include hydrogen peroxide binding (8,9,11), pH effects (12), and several redox-active molecules discussed in the literature (13). A second mechanism, exciton quenching, involves the adsorption of a moiety that perturbs the exciton itself, preventing recombination and/or increasing competitive nonradiative decay, effectively quenching the PL (3) (mechanism 2, Fig.…”

The Role of Length and Defects on Optical Quantum Efficiency and Exciton Decay Dynamics in Single-Walled Carbon Nanotubes

“…14Ϫ16 Stepwise fluorescence quenching in carbon nanotubes in response to changes to the nanotube's environment 16Ϫ18 can clearly also be utilized in sensor applications, such as biological sensors, ideally capable of detecting single molecules. 19 The diffusion constant is the main parameter of the diffusion model, but it is not well-known. Experimentally extracted values of the diffusion constant range over 3 orders of magnitude, from 0.1 to 100 cm 2 /s.…”

“…19 We simulate the quantum efficiency of a nanotube as a function of time, with defects randomly created and destroyed on the nanotube. The nanotube also has permanent defects at specific intervals to mimic conditions for nanotubes embedded in a cross-linked polymer 17 or from defects induced during nanotube processing.…”