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

Abstract

A class of peptides from the bombolitin family, not previously identified for nitroaromatic recognition, allows near-infrared fluorescent single-walled carbon nanotubes to transduce specific changes in their conformation. In response to the binding of specific nitroaromatic species, such peptide-nanotube complexes form a virtual "chaperone sensor," which reports modulation of the peptide secondary structure via changes in single-walled carbon nanotubes, near-infrared photoluminescence. A split-channel microscope constructed to image quantized spectral wavelength shifts in real time, in response to nitroaromatic adsorption, results in the first single-nanotube imaging of solvatochromic events. The described indirect detection mechanism, as well as an additional exciton quenching-based optical nitroaromatic detection method, illustrate that functionalization of the carbon nanotube surface can result in completely unique sites for recognition, resolvable at the single-molecule level.bionanotechnology | explosives detection | pesticides | spectroscopy | optical sensors S ingle-walled carbon nanotubes (SWNT) emit near-infrared (NIR) bandgap photoluminescence (PL) (1, 2), which is highly responsive to its physical and chemical environment (3-6). SWNT are unique among nanoscale sensor platforms in their ability to detect the adsorption of as few as a single molecule of an analyte (7,8). 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).The current work investigates the selective optical detection of binding events by single-SWNT PL modulation, employing both intensity-and wavelength-based signal transduction. We find that specific noncovalently bound polymers can be harnessed to change the properties of the nanotube-polymer complex, resulting in complete modulation of the nanotube sensitivity to certain analytes. Resolution of an entire class of molecules can be achieved by the nanotube via reporting the conformational state of a peptide, for example. Nanotube emission undergoes solvatochromic shifts due to nitroaromatic compound-mediated secondary structure changes of the amphipathic bombolitin II oligopeptide. In this work, we probe solvatochromic interactions at the single-nanotube level by a strategy in which two spectrally adjacent optical channels measure anticorrelated, quantized fluctuations, signifying molecular binding events. In addition, we find that an oligonucleotide of single-stranded DNA with the sequence ðATÞ 15 [ssðATÞ 15 ] oligonucleotide imparts optical selectivity of SWNT for trinitrotoluene (TNT) via intensity modulation. Although nanotubes do not ...

Molecular recognition using corona phase complexes made of synthetic polymers adsorbed on carbon nanotubes

“…6e-g). Using a home-built nearinfrared, dual-channel imaging microscope 23 , we spatially imaged the wavelength shifts of the (7,6) SWNT, l max ¼ 1,147 nm, on riboflavin binding within murine macrophages cultured in riboflavinfree media (Supplementary Fig. 20).…”

“…Adsorbates can also screen the one-dimensional confined exciton 18,19 , causing solvatochromic shifts in emission 20,21 , particularly with polymer wrappings that change conformation. Our laboratory and others have developed SWNT fluorescence sensors for detecting b-D-glucose 12 , DNA hybridization 21 , divalent metal cations 20 , assorted genotoxins 22 , nitroaromatics 23 , nitric oxide 13,17 , pH 16 and the protein avidin 14 . These efforts have invariably exploited conventional molecular recognition entities, such as enzymes 24 , oligonucleotides 21 or specific functional groups with known affinity for the target molecule 13 .…”

Protein functionalized carbon nanomaterials for biomedical applications

“…The peptides were non-covalently bound to the nanotubes by direct sonication, and underwent a conformation change upon analyte binding, resulting in a solvatochromatic shift in the fluorescent emission [113].…”

30 years of advances in functionalization of carbon nanomaterials for biomedical applications: a practical review

“…These approaches can be greatly suitable for in vivo diagnostic and therapeutic purposes, such as vaccine 116 and gene delivery 117,118 systems, as well as an exciton quenching-based optical sensing for singlemolecule detection of nitroaromatic compounds. 119 …”